hvdc transmission system

HVDCTRANSMISSIONSYSTEMFORRURALALASKAAPPLICATIONSPhaseII‐PrototypingandTesting

May2012FINALREPORT,Version1.1

preparedby

polarconsultalaska,inc.1503West33rdAvenue,Suite310Anchorage,Alaska99503Phone:(907)258‐2420

fundingagency

TheDenaliCommission510LSt.,Suite410Anchorage,Alaska99501Phone:(907)271‐1414

projectadministrator

AlaskaCenterforEnergyandPowerUniversityofAlaska,Fairbanks814AlumniDr.P.O.Box755910Fairbanks,Alaska99775Phone:(907)474‐5402

FINALREPORT,VERSION1.1 POLARCONSULTALASKA,INC.HVDCTRANSMISSIONSYSTEMFORRURALALASKANAPPLICATIONS PHASEII–PROTOTYPINGANDTESTING

MAY 2012

AbouttheCoverImage:

ThecoverimageisofademonstrationinstallationinFairbanksofaguyedfiberglasspolesimilarinsize,height,andconstructiontothepolesconsideredinthisstudyforoverheadtransmissioninruralAlaskaapplications.Thepoleisa12‐inch‐diameter,60‐foot‐tallfiberglassstructuresupportedbythreemicro‐thermopiles.Thepole’sfourguysareanchoredbytwomicro‐thermopilesandtwoscrewanchorssetinsilt‐richpermafrost.


MAY 2012 PAGE I

EXECUTIVESUMMARY

ProgramObjectives

ThisreportpresentstheachievementsandfindingsofPhaseIIofthe“High‐VoltageDirectCurrent(HVDC)TransmissionSystemsforRuralAlaska”researchanddevelopment(R&D)program.ThegoalofthisprogramistoimprovetheeconomicviabilityofAlaska’sruralcommunitiesbyprovidingmoreaffordableelectricitytransmissionalternatives.PhaseIIworkwasfundedbytheDenaliCommissionandcompletedbyPolarconsultAlaska,Inc.(Polarconsult)undercontracttotheAlaskaCenterforEnergyandPower(ACEP).

TheeffectofexcessiveenergycostscontinuestodegradethequalityoflifeinAlaska’sruralcommunitiesandplacestheseindigenouspopulationsatsevererisk.Nearly80%ofruralcommunitiesaredependentondieselfuelfortheirprimaryenergyneeds.Someofthepooresthouseholdsspent47%oftheirincomeonenergyin2008,morethanfivetimestheamountinAnchorage(CWN,2012).

HVDCintertieswillsupportmorecost‐effectivedevelopmentoflocalenergyresources,suchaswind,hydro,biomass,geothermal,hydrokinetic,gas,andcoal.Reducingthecostoflow‐power(1megawatt[MW]andless)intertiesbyusingHVDCsystemscanenableincreasedinterconnectionofruralcommunitiestoAlaska’sabundantenergyresources.

HVDCintertieswillalsobenefitruralcommunitieswithreducedenergycostsbybuildingeconomicsofscaleinruralpowergridsandallowingutilitiestoconsolidatebulkfuelfacilitiesanddieselelectricpowerplantsintomoreefficientandlower‐costconfigurations.

Asaresultofongoingadvancesinpowerelectronics,small‐scaleHVDCintertiesarenowfeasible.Thisreporthasidentifiedlow‐poweroverheadandsubmarineHVDCtransmissionsystemsasaneconomicallysuperioralternativetoconventionalalternatingcurrent(AC)interties.AdditionalcostreductionscanberealizedbyintegratingHVDCsystemswithfutureexpansionofbroadbandfiber‐optictelecommunicationnetworks.ThissynergisticopportunitybetweenthetelecommunicationsandelectricindustriesisoneofseveralreasonsHVDCintertiescanhelpsurmounttheeconomicbarriersfacingAlaska’sruralcommunities.

ComparativeanalysisofHVDCtransmissionsystemswithconventionalACsystemsindicatessignificanttechnicalandeconomicadvantagesofHVDCsystems.InmanyruralAlaskaapplications,theuseofHVDCsystemswillsignificantlylowerintertiecosts.

PhaseIIObjectivesandFindings

PhaseIIofthisR&DprogramfollowsthePhaseI–PreliminaryDesignandFeasibilityAnalysisFinalReport(Polarconsult,2009).PhaseItasksincludedassessingconvertertechnicalfeasibilityandevaluatingtheeconomicsofalow‐powerHVDCsystemsizedforruralAlaskaapplications.BasedonthefavorableresultsofthePhaseIproject,thefollowingPhaseIIobjectiveswereestablished:

● ConfirmationofthetechnicalfeasibilityoftheHVDC/ACpowerconvertertechnologybydesigning,building,andtestingafull‐scaleprototypeofa1‐MWbidirectionalpowerconverterandkeytransmissionsystemelements.


MAY 2012 PAGE II

● Confirmationoftheeconomicfeasibilityofthelow‐powerHVDCsysteminruralAlaskaapplicationsbydeterminingthecommercialcostoftheconverter,theconverter’sefficiency,andtheestimatedoverallcostsofanHVDCsystem.

● DevelopmentofcostestimatesforHVDCtransmissionsystemsandcomparisonwithconventionalACsystemstoquantifythebenefitsandsavingsofHVDCsystems.

PhaseIIhasdemonstratedthattheconvertertechnologyistechnicallyviableandthetransmissionsystemiseconomicallyfeasible.KeyPhaseIIfindingsare:

● Low‐powerHVDCconvertertechnologyisexpectedtobecommerciallyavailableat$250perkilowattperconverter.

● Estimatesofconstructioncostsforaconceptual25‐mileoverheadHVDCintertieindicatecapitalcostsavingsofapproximately30%comparedwithaconventionaloverheadACintertie.Estimatedlife‐cyclecostsrangefrom79%to107%ofthelife‐cyclecostofanACintertie.

● LongeroverheadHVDCintertiescanexpectcapitalcostsavingsofupto40%.

● PhaseIIanalysisalsoindicatesthatsignificantsavingsarepossibleforsubmarinecableandundergroundcableapplicationsusingHVDCsystems.Estimatedcapitalcostsavingsona25‐milelow‐powerHVDCsubmarinecableintertieareover50%comparedtoACalternatives.

BasedonPhaseIIfindings,thebenefitsoflow‐powerHVDCsystemsforAlaskaaresubstantial,andcontinueddevelopmentofthissystemisrecommended.

OpportunitiesandBarriers

BasedonanalysisandstudyconductedduringthisPhaseIIproject,PolarconsulthasconcludedthatthisHVDCtechnologypresentsthefollowingopportunitiesforAlaska’sutilityindustryandruralcommunities:

● Lessexpensiveruralelectricinterties,leadingtolower‐costenergyandincreasedenergyindependenceforruralcommunities.

● Interconnectiontocurrentlystrandedlocalenergyresources.

● Interconnectioncostsavingsbycombiningruralelectricandtelecommunicationsinterties.

Thesuccessfulcommercializationandadoptionoflow‐powerHVDCtechnologyinAlaskarequiresovercomingthefollowingbarriers:

● Completionofthecommercialdevelopmentanddemonstrationoftheconvertertechnology.Continueddevelopmentoftheprototypeconverters,culminatinginindependenttestingoftheconvertersanddeploymentonanAlaskautilitysystem,isneededtoprovethattheconvertersareacommerciallyviabletechnology.

● Acceptanceanduseoflow‐powerHVDCtechnologybyAlaska’sutilityindustry.Continuedinvolvementofin‐stateandinternationalstakeholderswiththeongoingdevelopmentofthistechnologyisconsiderednecessarytosurmountingthisbarrier.

● Developmentanddemonstrationofstandardsandcontrolprotocolsforlow‐powermultiterminaldirect‐current(MTDC)transmissionnetworks,whichareneededtobuildcost‐effectiveregionalHVDCpowernetworksinruralAlaska.


MAY 2012 PAGE III

Recommendations

Basedontheconclusionsandfindingsofthisproject,thefollowingactionsarerecommended:

PhaseIIIprogramactivities:

● Continueddevelopmentofthepowerconvertertechnologytocommercializetheexistingprototypeconverterdesign.SolicitationofadditionalHVDCconvertermanufacturersiswarrantedtoencouragediversityofsuppliersandcompetition;

● Independenttestingoftheconverterstovalidateefficiencyandperformance,followedbydeploymentonanAlaskanutilitysystemtovalidatefunctionalityandreliabilityinacommercialsetting;

● FurtherdevelopmentofMTDCtransmissionsystemsinterconnectionandcontroltechnologies;and

● Continuedinvolvementofin‐statestakeholdersinthedevelopmentofthistechnology.

Stakeholderactions:

● Incorporatelow‐powerHVDCtechnologyintoAlaska’sregionalandstatewideenergyplansandpolicies;

● ContinuecoordinationwiththeStateofAlaskatoallowaproject‐specificwaiveroftheNationalElectricalSafetyCode(NESC)toallowtheuseofsingle‐wireearthreturn(SWER)circuits;

● EncourageplannedruralpowerandtelecommunicationsintertiestoincorporateHVDCtechnologyintheireconomicandtechnicalanalysis,aswellastheirenvironmentalandpermittingreviewprocesses;

● Engagethetelecommunicationsindustrytoraiseawarenessofthesynergiespossiblebetweenlow‐powerHVDCtransmissionandfibernetworksinruralAlaska;and

● Collaboratewithinternationalstakeholderstoidentifysynergiesandlessonslearnedfromparalleltechnologydevelopmentefforts.Coordinateondevelopmentofapplicablepolicies/standardsandidentificationofmarketstohelpexpeditethecommercializationandreducethecostsoflow‐powerHVDCsystems.


MAY 2012 PAGE IV

TABLEOFCONTENTS

EXECUTIVESUMMARY...........................................................................................................................................................I

1.0 INTRODUCTION........................................................................................................................................................1 1.1 REPORTORGANIZATION...................................................................................................................................................2

1.2 ACKNOWLEDGEMENTS......................................................................................................................................................3

1.3 DISCLAIMER.........................................................................................................................................................................4

1.4 COPYRIGHTNOTICE...........................................................................................................................................................4

2.0 BACKGROUND............................................................................................................................................................5 2.1 PROGRAMOVERVIEW........................................................................................................................................................6

2.2 STAKEHOLDERADVICE......................................................................................................................................................7

3.0 HVDCTRANSMISSIONSYSTEMDESCRIPTION............................................................................................8 3.1 HVDCBACKGROUND........................................................................................................................................................8

3.2 HVDCSYSTEMCONFIGURATIONS................................................................................................................................10

3.3 COMPARISONOFACTOHVDCTRANSMISSION.........................................................................................................16

3.4 OVERHEADINTERTIEALTERNATIVES.........................................................................................................................17

3.5 SUBMARINECABLEINTERTIEALTERNATIVES...........................................................................................................19

4.0 HVDCCONVERTERSTATIONS.........................................................................................................................20 4.1 OVERVIEW........................................................................................................................................................................20

4.2 CONVERTERDEVELOPMENTOVERVIEW.....................................................................................................................20

4.3 ADDITIONALEQUIPMENT..............................................................................................................................................28

5.0 DESIGNCONCEPTSFOROVERHEADINTERTIES....................................................................................29 5.1 OVERHEADDESIGNAPPROACH....................................................................................................................................29

5.2 GEOTECHNICALCONDITIONS........................................................................................................................................30

5.3 ENVIRONMENTALLOADS...............................................................................................................................................30

5.4 CONSTRUCTION,RUSSTANDARDPRACTICE..............................................................................................................30

5.5 CONSTRUCTION,ALASKA‐SPECIFICCONCEPT............................................................................................................31

5.6 TESTINGOFOVERHEADDESIGNCONCEPTS...............................................................................................................32

6.0 SYSTEMECONOMICS...........................................................................................................................................37 6.1 COSTCOMPARISONOFACANDHVDCOVERHEADINTERTIES..............................................................................37

6.2 CASESTUDIES..................................................................................................................................................................41

7.0 CONCLUSIONSANDRECOMMENDATIONS................................................................................................49 7.1 CONCLUSIONS...................................................................................................................................................................49

7.2 OPPORTUNITIESANDBARRIERS...................................................................................................................................49

7.3 RECOMMENDATIONS.......................................................................................................................................................50


MAY 2012 PAGE V

LISTOFTABLES

Table6‐1 EstimatedLife‐CycleCostsfor25‐mileOverheadACandHVDCInterties......................39

Table6‐2 SummaryofCaseStudies......................................................................................................................42

Table6‐3 EstimatedCostforaGreensCreek–HoonahHVDCIntertie.................................................44

Table6‐4 EstimatedBenefit‐CostRatioofGreensCreek–HoonahHVDCIntertie..........................45

Table6‐5 EstimatedInstalledCostfora5‐MWPilgrimHotSprings–NomeIntertie....................48

LISTOFFIGURES

Figure3‐1 TypicalLargeHVDCStation....................................................................................................................9

Figure3‐2 ThreeTypesofIntertiesUsedinHVDCSystems........................................................................11

Figure3‐3 MonopolarHVDCIntertieUsingSWER...........................................................................................12

Figure3‐4 MonopolarHVDCIntertiewithReturnConductor(SWER‐capableforBackup)..........13

Figure3‐5 BipolarHVDCIntertie(SWER‐capableforBackup)..................................................................14

Figure4‐1 LowVoltageAlternatingCurrent(LVAC)Enclosure:MechanicalLayout........................22

Figure4‐2 HVDCTransformerTank:MechanicalLayout.............................................................................23

Figure4‐3 CentralResonantLinkTestSetup.....................................................................................................25

Figure4‐4 Hi–PotTestSetupforHVDCTransformer.....................................................................................25

Figure4‐5 DrySystemInverterModeTestSchematicandSetup..............................................................26

Figure4‐6 System#1HVTankandLVEnclosure............................................................................................27

Figure4‐7 System#1ShowingHVMeasurementProbes.............................................................................27

Figure5‐1 InstallingMicro‐ThermopileforGuyAnchor...............................................................................33

Figure5‐2 AssemblingthePrototypeGFRPPoleSplice................................................................................34

Figure5‐3 PrototypeGFRPPoleFoundationDuringInstallation..............................................................35

Figure5‐4 PrototypePoleattheFairbanksTestSite......................................................................................36

Figure6‐1 ComparativeInstalledCost:Overhead1‐MWHVDCandACInterties..............................38

Figure6‐2 ComparativeLife‐CycleCost:Overhead1‐MWHVDCandACInterties............................40

Figure6‐3 LocationMapforPotentialHVDCProjectSites...........................................................................41

Figure6‐4 GreensCreek–HoonahIntertieRoute...........................................................................................43

Figure6‐5 ProspectiveTransmissionRoutefromPilgrimHotSpringstoNome................................47


MAY 2012 PAGE VI

APPENDICES

APPENDIXA HVDCOVERVIEW............................................................................................................................A‐1

APPENDIXB ECONOMICANALYSIS...................................................................................................................B‐1

APPENDIXC CONCEPTUALDESIGNOFOVERHEADHVDCINTERTIELINES.................................C‐1

APPENDIXD CONCEPTUALDESIGNFORSUBMARINECABLES............................................................D‐1

APPENDIXE SWERCIRCUITSANDHVDCSYSTEMGROUNDING.........................................................E‐1

APPENDIXF HVDCPOWERCONVERTERDEVELOPMENT.....................................................................F‐1

APPENDIXG HVDCSYSTEMPROTECTION,CONTROLS,ANDCOMMUNICATIONS......................G‐1

APPENDIXH CANDIDATEHVDCSYSTEMDEMONSTRATIONPROJECTS..........................................H‐1

APPENDIXI STAKEHOLDERADVISORYGROUPINVOLVEMENTANDMEETINGS........................I‐1

APPENDIXJ BIBLIOGRAPHY..................................................................................................................................J‐1


MAY 2012 PAGE VII

ACRONYMSANDTERMINOLOGY

°F degreesFahrenheit

A,a,i amperesoramps

AC alternatingcurrent

ACEP AlaskaCenterforEnergyandPower

ACSR aluminumconductorsteelreinforced

ADNR AlaskaDepartmentofNaturalResources

AEA AlaskaEnergyAuthority

AEL&P AlaskaElectricLightandPowerCompany

AFI ArcticFoundations,Inc.

AKDOL AlaskaDepartmentofLabor

albedo Theextenttowhichanobjectdiffuselyreflectslight.

alternatingcurrent

Theformofelectricitycommonlyusedinhomesandbusinessesinwhichthecurrentandvoltageoscillateatafrequencyof60cyclespersecond.(Thefrequencyinsomenationsis50cycles.)

Alumoweld Atypeofcableusedinelectricalsystems.Eachstrandofthecableconsistsofasteelcorewithalayerofaluminumextrudedoveritduringthepullinganddrawingprocess.Thesteelcoreprovidesincreasedstrength,andthealuminumexteriorprovidesbettercorrosionprotectionandincreasedelectricalconductivity.

amperes/amps

Ameasureoftheamountofelectricalcurrentflowingthroughacircuit(atypicalhouseholdcircuitisratedfor20amperes).

AP&T AlaskaPowerandTelephoneCompany

APA AlaskaPowerAssociation

ASCE AmericanSocietyofCivilEngineers

AVEC AlaskaVillageElectricCooperative,Inc.

AVR automaticvoltagereference

bandwidth Ameasureofthedatatransfercapabilityofagivencommunicationsmethod.Unitsofbandwidthcanvarybutaregenerallybitspersecond.

BEC BethelElectricUtility

bipolar Atypeofdirectcurrentcircuitthatusestwowirestotransmitenergy.Bipolarcircuitsoperateonewire(“pole”)atapositivepotentialandthesecondpoleatanegativepotentialrelativetoground(e.g.,+/‐600,000volts).Thesecircuitsnormallyalsohaveanearthreturnpathwayoradedicatedgroundconductorthatisusedtocompensateforanyimbalanceonthetwopolesandservesasatemporaryreturnpathwayifthenegativeorpositivepoleisoutofserviceforanyreason.

BSNC BeringStraitsNativeCorporation


MAY 2012 PAGE VIII

Btu Britishthermalunit

CEA ChugachElectricAssociation,Inc.

CIGRE InternationaledesGrandsReseauxElectriques

circuit Acircuitprovidesanelectricalpathwayfromapointofenergysupply(e.g.,ageneratororbattery)toapointofenergyuse(e.g.,motor,lighting,etc.),andthenbacktothepointofsupply.Withoutacompletepathwayfromsupplytouseandback,thecircuitwillnotfunction.Thepathwaycantakemanyforms.Mostcommonly,itismadeofmetallic(copperoraluminum)wires,butitcanalsousewater,theearth,orothermaterials.Theseothermaterialsaremostoftenusedonthereturnpathwaybacktothepointofsupply,wherethevoltagedifferentialrelativetothesurroundingenvironmentislow.

conductor Atypicallymetallicwireorcablethatisdesignedandfabricatedtoconductelectricitybetweentwolocations.

converter AnelectricaldevicethatconvertselectricityfromACtoDCand/orfromDCtoAC.“Converter”isamoregeneraltermforarectifierorinverter.

CVEA CopperValleyElectricAssociation,Inc.

DC directcurrent

directcurrent Directcurrentistheformofelectricitycommonlyusedinbattery‐powereddevicessuchascars,flashlights,etc.Thecurrentdoesnotappreciablyvarywithtime.

distributionclass

Referstolower‐voltageelectricalsystems.Definitionsvary,butsystemsoperatingatorbelownominal35kilovolts(kV)aregenerallyclassifiedasdistribution‐class.MostruralAlaskaintertiesfunctionastransmissionsystems,butoperateatdistribution‐classvoltages,typically14.4kV.

earthreturn Ameansofcompletinganelectricalcircuitbyusingtheearthasareturnpathinsteadofasecondwire.Inmanynations,thisapproachisfrequentlyusedinruralareaswhere(1)thecosttoinstallasecondwireforthereturnpathisprohibitivelyhighand(2)thelackofburiedutilitiesensuresthattechnicalissueswithgroundreturnareminimized.

EHS extra‐high‐strength

EPR ethylenepropylenerubber

fiberoptics Acommunicationsmethodthatconsistsofsendingpulsesoflightdownglassfibers.

FO fiberoptics

ft‐lb foot‐pound

gal gallon(s)

GEC GustavusElectricCompany

GFRP glass‐fiber‐reinforcedpolymer

GPS GlobalPositioningSystem

GVEA GoldenValleyElectricAssociation,Inc.


MAY 2012 PAGE IX

HEA HomerElectricAssociation,Inc.

hertz Aunitofhowrapidlysomethingoscillates,rotates,orrepeats.Onehertzisequaltoonecompletecyclepersecond.AlternatingcurrentelectricalsystemsintheU.S.operateat60hertz,or60cyclespersecond.

high‐impedancegroundfault

Afaultorshortcircuitbetweenahigh‐voltagewireandground.Anexampleofahigh‐impedancegroundfaultwouldbeaconductorthatfallstothegroundwithoutbreaking,landingoniceorice‐richsoils.Thesesoilsareverypoorconductors,thuslittleornocurrentmayshortcircuitintotheground.Becausethewiredidnotbreak,itcancontinuetotransmitenergybetweentheconverters.Thisenergizedwireposesahazardtoanypeopleoranimalswhohappenuponit.

high‐voltagedirectcurrent

Directcurrentelectricityatahighvoltagerelativetothesurroundingenvironment.

HMI human‐machineinterface

hotwork Workingonelectricalequipmentwhileitisenergized.

HVDC high‐voltagedirectcurrent

IEC InternationalElectro‐technicalCommission

IEEE InstituteofElectricalandElectronicsEngineers

IGBT insulatedgatebipolartransistor

inverter AnelectricaldevicethatcanconvertDCelectricityintoACelectricity.

IPEC InsidePassageElectricCooperative

KEA KodiakElectricAssociation,Inc.

kHz kilohertz(1,000hertz)

kilowatt 1,000watts.OnekWisthepowerconsumedbyten100‐wattincandescentlightbulbs.

kilowatt‐hour Thequantityofenergyequaltoonekilowatt(kW)expendedforonehour.

KoEA KotzebueElectricAssociation,Inc.

kV kilovolt(1,000volts)

kVA kilovolt‐ampere

kW kilowatt(1,000watts)

kWh kilowatt‐hour

LDE LineDesignEngineering,Inc.

LFL linefaultlocator

LIDAR lightdetectionandranging

litzwire Anelectricalwireorcablemadeofmultipleindividuallyinsulatedstrandsofwire.LitzwireisusedinhighfrequencyACapplicationsandisdesignedtoreducepowerlossescausedbyskineffectsandproximityeffectsthatoccurathighfrequencies.

LVAC low‐voltagealternatingcurrent


MAY 2012 PAGE X

MEA MatanuskaElectricAssociation

MHRC ManitobaHVDCResearchCentre

mm2 squaremillimeters

MOD motor‐operateddisconnector

monopolar Adirectcurrentcircuitthatoperatesonelegofthecircuitatanelevatedvoltageandthereturnlegatorneargroundvoltage.Thereturnlegcanuseametallicconductoror,inthecaseofearthorseareturnsystems,canusetheearthorseatocompletethecircuit.AnHVDCSWERcircuitisonetypeofmonopolarcircuit.

ms millisecond(s)

MSB Matanuska‐SusitnaBorough

MTDC multi‐terminaldirectcurrent

MVA megavoltamperes(onemillionvoltamperes)

MW megawatt(s)(1,000kilowatts)

MWh megawatt‐hours

NCC NomeChamberofCommerce

NEA NaknekElectricAssociation,Inc.

NEC NushagakElectricCooperative,Inc.

NESC NationalElectricalSafetyCode

NJUS NomeJointUtilityService

NLP NuvistaLightandPower,Inc.

NRECA NationalRuralElectricCooperativeAssociation

NSB NorthSlopeBorough

NWAB NorthwestArcticBorough

O&M operationsandmaintenance

OED CityofOuzinkieElectricDepartment

OMR&R OperationandMaintenance,Repair,Replacement,andRehabilitation

OPGW opticalgroundwire

PCB printedcircuitboard

PCE PowerCostEqualization

PLC powerlinecarrier

PPS PrincetonPowerSystems,Inc.

PSCAD PowerSystemsComputerAidedDesign

psf poundspersquarefoot

R&D researchanddevelopment

RCA RegulatoryCommissionofAlaska

rectifier AnelectricaldevicethatcanconvertACelectricityintoDCelectricity.


MAY 2012 PAGE XI

RMS root‐mean‐square

rootmeansquare

Therootmeansquarevoltageisthemeanabsolutevoltageoveranywholenumberofwaveformoscillations.Forasinusoidalwaveform(suchasnormalACelectricity),theroot‐mean‐square(RMS)voltageisthepeakvoltagedividedbythesquarerootof2.Nominal120voltsalternatingcurrent(VAC)electricitythushasapeakvoltageofabout+/‐170voltsrelativetoground.

RUS RuralUtilitiesService(USDA)

SAG StakeholdersAdvisoryGroup

SCADA supervisorycontrolanddataacquisition

seareturn Ameansofcompletinganelectricalcircuitbyusingthesea(ormoregenerallyrivers,lakes,andotherwaterbodies)asareturnpathinsteadofasecondwire.Thisapproachisfrequentlyusedonsubmarinecableswherethecostsavingsfromnotinstallingasecondcablejustifythisapproach.Seareturncanbeusedforsingle‐phaseACcircuitsorforDCcircuits.

SEAPA SoutheastAlaskaPowerAgency

SEC SoutheastConference

single‐wireearthreturn

Anothertermforanearthreturnorseareturncircuit.Thenameemphasizesthefactthatthesetypesofcircuitsonlyrequireonewire,ascomparedwithtwoormorewiresforothertypesofcircuits.

spurandbelt Acommonmethodofclimbingutilitypoles,trees,andsimilarobjects.Specialclimbingspursarestrappedontothefeetandalargebeltisfixedaroundtheclimber'swaist.Theclimberloopsthebeltaroundthepoleanddrivesthespursintothepole.Theclimberthen“walks”upthepolewiththespurs,andhitchesthebeltalongthepoleforsupport.

steppotential Avoltagegradientthatoccursatthegroundsurfaceduetoearthreturncurrents.Ifthevoltagegradientishighenough,itcanposeahazardtopeopleorwildlifesteppinginthevicinity.

strandedenergyresources

Energyresourceslocatedinremote,distant,orotherwiseisolatedareas“stranded”fromeither(1)integrationintomodernenergyinfrastructureandsupplychainsor(2)utilizationbylocalpopulationandindustrycenters.

SWAMC SouthwestAlaskaMunicipalConference

SWER single‐wireearthreturn

transmission‐class

Referstohigher‐voltageelectricalsystems.Definitionsvary,butinAlaskaACsystemsoperatingabovenominal35kVline‐to‐groundaregenerallyclassifiedastransmission‐class.MostruralAlaskaintertiesfunctionastransmissionsystems,butareoperatedatdistribution‐classvoltages.

twistedpair Agenerictermforcommunicationscablethatusesmultipleindividuallyinsulatedwires.Eachpairofwiresistwistedtogether,hencethename.

TWMR transmissionwithmetallicconductor‐returnpath

UAF UniversityofAlaskaFairbanks

USDA U.S.DepartmentofAgriculture


MAY 2012 PAGE XII

V volt

VAC voltsalternatingcurrent

VAR volt‐amperesreactive

VDC voltsdirectcurrent

VFT variablefrequencytransformer

volt Aunitofelectricalpotential.Sometypicalvoltagesarecarbattery:12volts(DC);alkalinebattery(AAA,C,D,etc.):1.5volts(DC);householdelectricity:120volts(ACRMS).

VSC voltagesourceconverter(s)

ZAE ZarlingAeroConsulting


MAY 2012 PAGE 1

1.0 INTRODUCTION

ThisreportpresentstheachievementsandfindingsofPhaseIIofthe“High‐VoltageDirectCurrent(HVDC)TransmissionSystemsforRuralAlaska”researchanddevelopment(R&D)program.

ThegoalofthisprogramistoimprovetheeconomicviabilityofAlaska’sruralcommunitiesbyprovidingmoreaffordableelectricitytransmissionalternatives.TheeffectofexcessiveenergycostscontinuestodegradethequalityoflifeinAlaska’sruralcommunitiesandplacestheseindigenouspopulationsatsevererisk.Nearly80%ofruralcommunitiesaredependentondieselfuelfortheirprimaryenergyneeds.Someofthepooresthouseholdsspent47%oftheirincomeonenergyin2008,morethanfivetimestheamountinAnchorage(CWN,2012).

Reducingthecostoflow‐power(1megawatt[MW]andless)intertiesbyusingHVDCsystemscanenableincreasedinterconnectionofruralcommunitiestoAlaska’sabundantenergyresources.HVDCintertieswillsupportmorecost‐effectivedevelopmentoflocalenergyresources,suchaswind,hydro,biomass,geothermal,hydrokinetic,gas,andcoal.

PhaseIIofthisprogramwasfundedbytheDenaliCommissionandcompletedbyPolarconsultAlaska,Inc.(Polarconsult)undercontracttotheAlaskaCenterforEnergyandPower(ACEP).ThisPhaseIIeffortandfinalreportfollowstheresultsofthePhaseIR&Dproject,completedin2009andsummarizedinPhaseI–PreliminaryDesignandFeasibilityAnalysisFinalReport(Polarconsult,2009).PhaseIofthisR&DprogramincludedevaluationofthetechnicalandeconomicfeasibilityoftheproposedHVDCsystem,includinglimitedprototypingandtestingoftheconvertertechnology.

PhaseIIoftheHVDCTransmissionSystemprogramincludeddesign,fabrication,andtestingoffull‐scaleprototypesoftheconverterandtransmissionsystemelements.ThePhaseIIeffortsinvolvedtheevaluationofdesign,efficiency,andfunctionalityoftheHVDCsystems.RuralAlaskaintertiealternativeswerealsoinvestigated,whichinvolvedcomparingHVDCtransmissionsystemstotheconventionalalternatingcurrent(AC)alternatives.ThePhaseIIfindingswereusedtofurtherdevelopconstructioncostestimatesandrefinetheeconomicanalysisofthetechnologydevelopedinPhaseI.PolarconsultistheprimecontractorandauthorofbothPhaseIandIIprojectreports.

Asaresultofongoingadvancesinpowerelectronics,small‐scaleHVDCintertiesarenowfeasible.ThisreporthasidentifiedoverheadandsubmarineHVDCtransmissionsystemsaseconomicallysuperioralternativestoconventionalACinterties.

AdditionalcostreductionscanberealizedbyintegratingHVDCsystemswithfutureexpansionofbroadbandfiber‐optictelecommunicationnetworks.ThissynergisticopportunitybetweenthetelecommunicationsandelectricindustriesisoneofseveralreasonsHVDCintertiescanhelpsurmounttheeconomicbarriersfacingAlaska’sruralcommunities.

ComparativeanalysisofHVDCtransmissionsystemswithconventionalACsystemsindicatessignificanttechnicalandeconomicadvantagesofHVDCsystems.InmanyruralAlaskaapplications,theuseofHVDCsystemswillsignificantlylowerintertiecosts.

Basedonthefavorablefindings,PolarconsultrecommendscontinuedworkonthisprojectthroughPhaseIIIworkactivities,includingdemonstrationoftheHVDCsystemonanAlaskautilitysystem.


MAY 2012 PAGE 2

1.1 REPORTORGANIZATION

PhaseIIofthisprojectaddressesawiderangeoftechnicaldisciplinesandsubjectmaterial.Forbrevity,thebodyofthisreportfocusesonthekeyfindingsandconclusionsthathaveresultedfromthiswork.In‐depthinformationpertainingtospecifictopicsisincludedinthereport’sappendices.

Thisreportisorganizedasfollows:

● TheExecutiveSummaryandtheAcronymsandDefinitionssectionsareincludedatthebeginning.

● Section1.0introducesthereport.

● Section2.0providesbackgroundinformationonAlaska’sruralenergyissuesandabriefexplanationofthestakeholders’rolesinthisphaseoftheproject.

● Section3.0isadescriptionoftheHVDCtransmissionsystem,whichincludesacomparisonofACandHVDCtransmission,overheadintertiealternatives,andsubmarinecableintertiealternatives.

● Section4.0discussesHVDCconverterstations.

● Section5.0evaluatesthedesignconceptsforoverheadinterties.

● Section6.0containstheeconomicevaluationofPhaseII.

● Section7.0providestheconclusionsandrecommendationsforthePhaseIIprototypingandtestingstudy.

Inaddition,thisreportcontainsthefollowingappendices,whichincludereportsgeneratedbyPolarconsult’ssubcontractorsforthisprojectasattachments:

● AppendixA HVDCOverview

● AppendixB EconomicAnalysis

● AppendixC ConceptualDesignofOverheadHVDCIntertieLines

● AppendixD ConceptualDesignforSubmarineCables

● AppendixE SWERCircuitsandHVDCSystemGrounding

● AppendixF HVDCPowerConverterDevelopment

● AppendixG HVDCSystemProtection,Controls,andCommunications

● AppendixH CandidateHVDCSystemDemonstrationProjects

● AppendixI StakeholderAdvisoryGroupInvolvementandMeetings

● AppendixJ Bibliography


MAY 2012 PAGE 3

1.2 ACKNOWLEDGEMENTS

Polarconsultacknowledgesandappreciatesthesupportandcontributionsofthemanyindividualsandentitiesthathaveparticipatedinthisproject.Theirsupport,insights,experience,andtechnicalanalysis remain invaluable to the continuing effort to bring lower‐costHVDC intertie systems toAlaskans.

MembersoftheteaminvolvedinthesecondphaseofHVDCintertiedevelopmentinclude:

● DenaliCommission(FundingAgency)

● ACEP(GrantManagement,EconomicAnalysis,Strategy)

● Polarconsult(ProjectManagement,StrategicVision,Design)

● PrincetonPowerSystems,Inc.(PPS)(ConverterDevelopment)

● UniversityofAlaskaFairbanks(UAF)/Dr.RichardWies(UAFQualityControlandTechnicalReview)

● AlaskaVillageElectricCooperative,Inc.(AVEC)(AlaskaIntegration/Practicality)

● StakeholdersAdvisoryGroup(Practicality/IndustryAcceptance)

● ManitobaHVDCResearchCentre(HVDCExpert)

● LineDesignEngineering(StructuralandCodeExpert)

● GolderAssociates(GeotechnicalExpert)

● Almita,Inc.(FoundationSupplier)

● ArcticFoundations,Inc.(AFI)(FoundationSupplier)

● ZarlingAeroConsulting(ZAE)(ThermalSoilsAnalysis)

● STG,Inc.(RuralIntertieContractor)

● Cabletricity,Inc.(SubmarineCable/HVDCExpert)

Inaddition,theStakeholdersAdvisoryGroup(SAG)membershaveplayedaninstrumentalroleinthisprogrambycontributingtheirtimeandyearsofexperience.TheSAGwaschairedbytheDenaliCommissionandfacilitatedbyACEP.SAGmembersinclude:

● AlaskaDepartmentofLabor(AKDOL)

● AlaskaEnergyAuthority(AEA)

● AlaskaPower&TelephoneCompany(AP&T)

● AlaskaPowerAssociation(APA)

● AVEC

● BeringStraitsNativeCorporation(BSNC)

● BethelElectricUtility(BEC)

● CopperValleyElectricAssociation,Inc.(CVEA)

● GoldenValleyElectricAssociation,Inc.(GVEA)

● HomerElectricAssociation,Inc.(HEA)

● InsidePassageElectricCooperative(IPEC)

● InstituteofNorthernEngineering(INE),UAF


MAY 2012 PAGE 4

● KodiakElectricAssociation,Inc.(KEA)

● KotzebueElectricAssociation,Inc.(KoEA)

● MatanuskaElectricAssociation(MEA)

● NaknekElectricAssociation,Inc.(NEA)

● NationalRuralElectricCooperativeAssociation(NRECA)

● NomeChamberofCommerce(NCC)

● NomeJointUtilityService(NJUS)

● NorthSlopeBorough(NSB)

● NorthwestArcticBorough(NWAB)

● NushagakElectricAssociation

● NuvistaLightandPower,Inc.(NLP)

● SoutheastConference(SEC)

● SouthwestAlaskaMunicipalConference(SWAMC)

● U.S.DepartmentofAgriculture(USDA)RuralUtilitiesService(RUS)

● UAF

1.3 DISCLAIMER

ThisreportwaspreparedbyPolarconsultsolelyfortheUAF.TheUAFhastherighttoreproduce,use,andrelyuponthisreportforpurposesrelatedtoinvestigatingthe“HVDCTransmissionSystemforRuralAlaskanApplications,”including,withoutlimitation,therighttodeliverthisreporttoregulatoryauthoritiesinsupportof,orinresponseto,regulatoryinquiriesandproceedings.ForthepurposesofthisDisclaimer,allpartiesotherthanPolarconsultandtheUAFare“thirdparties.”NeitherPolarconsultnortheUAFrepresent,guarantee,orwarranttoanythirdparty,expresslyorbyimplication,theaccuracy,suitability,reliability,completeness,relevance,usefulness,timeliness,fitness,oravailabilityofthisreportforanypurposeortheintellectualorotherpropertyrightsofanypersonorpartyinthisreport.

Thirdpartiesshallnotuseanyinformation,product,orprocessdisclosed,described,orrecommendedinthisreportandshallnotrelyuponanyinformation,statement,orrecommendationcontainedinthisreport.Shouldanythirdpartyuseorrelyuponanyinformation,statement,recommendation,product,orprocessdisclosed,contained,described,orrecommendedinthisreport,theydosoentirelyattheirownrisk.Tothemaximumextentpermittedbyapplicablelaw,innoeventshallPolarconsultortheUAFacceptanyliabilityofanykindarisinginanywayoutoftheuseorreliancebyanythirdpartyuponanyinformation,statement,recommendation,product,orprocessdisclosed,contained,described,orrecommendedinthisreport.

1.4 COPYRIGHTNOTICE

ThisreportiscopyrightprotectedbyPolarconsultandmaynotbereproducedinwholeorpartwithoutthepriorwrittenconsentofPolarconsult.


MAY 2012 PAGE 5

2.0 BACKGROUND

Energycoststhroughoutmostofrural1Alaskaaresignificantlyhigherthaninthestate’surbanareas.Overthepastdecade,ruralenergycostshaveescalateddramatically,tothepointwherelifeinmanyruralAlaskancommunitiesisinastateofeconomicperil.TheprimaryreasonsforthesehighenergycostsisruralAlaska’sdependenceondieselfuelforpowergenerationandheating,thelackofeconomiesofscaleinruralcommunities,andthetransportationchallengescommoninruralAlaska.

FormostruralAlaskancommunities,adiesel‐electricplantisthepowergenerationresourceofchoicesincetheseplantsandtheirsupportinginfrastructuresuchasbulkfuelfacilitiesarereadilyadaptedtotheneedsofrurallocalities.However,generatingelectricitywithdieselfuelisexpensiveduetothesecommunities’smallscaleandgeographicisolation.Consequently,ruralAlaskahassignificantlyhigherenergycostscomparedtocommunitiesinorconnectedwithAlaska’surbancenters.ThehighcostofruralenergynegativelyaffectboththequalityandsustainabilityoflifeinruralAlaska.

Manypowergenerationcostsarebeyondacommunity’scontrol.Thefuelpricefortheseplantsisdeterminedbyanincreasinglyvolatileglobalenergymarket.Inaddition,asubstantialcomponentofthefuelcostistransportation.Inrecentyears,thelimitedshippinganddeliverywindowscausedbyseasonaliceandlowwaterconditionsinmanypartsofthestatehaveresultedinvillagespayingrecordpricesforfuel.Interiorcommunities,locatedneartheupperlimitsofnavigablewaterwaysandthussusceptibletolowwaterconditions,paidasmuchas$11pergallonin2010(DCRA,2010).Severalruralcommunitiesfrequentlyflyinfuelduetoalackofreliablebargeaccessorservice.

Alternativestodieselgenerationoftenexistintheformoflocalenergyresourcessuchashydro,wind,geothermal,tidal,solar,gas,coal,andbiomass.However,manyofthese“strandedenergyresources”arenoteconomicallyviableduetothecostoftheconventionalACelectrictransmissionsystemsrequiredtointerconnectthemandtheprohibitivelyhighcosttodeveloptheselocalenergyresourcestoservesmallloads.HVDCintertiescanhelpsurmountbothofthesebarriersbyloweringthecosttoreachstrandedenergyresourcesandbyreducingthecosttointerconnectcommunities(ACEP,2012).

AlthoughcommercialHVDCtransmissiontechnologyhasbeenavailableforover50years,ithasbeenlimitedtolarge‐scaletransmissionoftenstothousandsofMWsofpower.ThesesystemsarefartoolargeandexpensivetousefortheinterconnectionofAlaska’sruralcommunities,whichtypicallyhaveloadsmeasuredinthehundredstothousandsofkilowatts(kWs).Currently,nocommerciallyavailableHVDCconvertersystemexiststhatissuitableforinterconnectingtheseruralcommunities.However,innovativetechnologiesinthepowerelectronicsindustryhavemadethedevelopmentoflow‐power,cost‐effectiveconvertersfeasible.

PolarconsulthasinvestigatedalternativestoACintertiesandfoundthatinmanyapplications,HVDCtransmissionsystemsusinginnovativepowerconversiontechnologiesofferthemosteconomicalsolutiontointerconnectwithstrandedenergyresources.Further,thereplacementofaconventionaloverheadACthree‐orfour‐wiretransmissionlinewithaone‐ortwo‐wireHVDC

1 RuralAlaskaforthepurposesofthisreportreferstoisolatedcommunitiesoffthemainroadsystemthathavehigh

energycostsduetotheirlocation,size,orotherfactors.


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transmissionlinehassignificantcostadvantages.Thechangeinoverheadinfrastructureresultsinreducedstructuralloads,allowingfewersupportstructurespermileoftransmissionline.ThedecreaseinmaterialsandconstructiontimeisoneofseveralreasonsthatoverheadHVDCintertiesarelesscostlythanACinterties.SubmarineandburiedHVDCintertiescanalsobelesscostlythantheirACalternatives.

2.1 PROGRAMOVERVIEW

TheHVDCdevelopmenteffortconsistsofthefollowingphases:

PhaseI–PreliminaryDesignandFeasibilityAnalysis(2008‐2009)

DuringPhaseI,PolarconsultevaluatedthetechnicalandeconomicfeasibilityoftheproposedHVDCsystem.TasksincludeddefiningtheHVDCsystem’spreliminarydesignparameters,definingdesignconsiderationsforthetransmissionandconvertercomponents,andestimatingcostsforthesesystems.PhaseIalsoincludedlimitedprototypingandsuccessfultestingoftheconvertertechnology.

PhaseII–PrototypingandTesting(2010‐2012)

PhaseIIincludedconstructionandtestingoffull‐scaleprototypesofthetransmissionandconvertersystems.ThiseffortvalidatedthedesignofthesesystemsandvalidatedthefeasibilityoftheconstructionmethodsnecessarytomakethesystemasuccessinruralAlaskaapplications.TheinformationfromPhaseIItestingwasusedtorefinetheconstructionmethodsanddevelopcostestimatesusedintheeconomicanalysisofthetechnologydescribedinthisreport.ThisreportisthefinaldeliverableforPhaseII.

PhaseIII–DemonstrationProject(Proposed)

PhaseIIIwillincludefulltestingoftheconvertersystem,includingthemanufacturerandthird‐partyfunctional,compliance,andperformancetestingneededtomovetheconvertertechnologyfromadvancedprototypestoacommercialproduct.PhaseIIIwillalsoincludeafull‐scalefielddemonstrationoftheHVDCtechnologyonautilitysysteminAlaska.Thespecificprojectdetailsaredependantonthecandidatelocationselectedfortheintertie.PhaseIIIisintendedtobethefinalproof‐of‐conceptproject,tobefollowedbycommercialdeploymentofthesystem.


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2.2 STAKEHOLDERADVICE

ThisprojectseekstodevelopahighlyinnovativepowertransmissiontechnologyfordeploymentinruralAlaskaapplications.Becausemanyaspectsofthissystemmarkadeparturefromacceptedpracticeinruralpowersystems,widespreadindustryunderstanding,aswellasacceptance,ofthistechnologyisconsideredcriticaltothesuccessofthiseffort.Additionally,theoverviewandfeedbackofindustryisconsideredcriticaltothesuccessfuldevelopmentoftheinnovativesystemsneededforthisHVDCtechnology.

TheDenaliCommissionandACEPrecognizedthatthebestmeanstoachievethisunderstanding,acceptance,andfeedbackwouldbetodirectlyengagethestakeholdersandend‐usersoftheproposedsysteminthedevelopmentstagesofthetechnology.Tothisend,aSAGwasformedaspartofthePhaseIIefforttofamiliarizeandfacilitatefeedbackfromindustryleadersonthedevelopmentofthissystem.

TheSAGisanadvisorybodycomprisedofrepresentativesofAlaska’sruralelectricutilityindustryandrelatedprofessionals.ThepurposeoftheSAGistoprovidecomments,feedback,review,andrecommendationstotheHVDCproject.TheSAGheldthefollowingthreemeetingsoverthecourseoftheproject:

● SAGMeeting#1–Fairbanks,Alaska‐‐April27,2010;

● SAGMeeting#2–Anchorage,Alaska–January14,2011;and

● SAGMeeting#3–Anchorage,Alaska–October25,2011.

Severaladditionaloutreachactivitiesoccurredoverthecourseoftheproject.Theseincluded:

● SoutheastConferenceMid‐SessionSummit–Juneau,Alaska(March2,2010);

● EmergingEnergyTechnologyForum–Juneau,Alaska(February14,2011);

● Brown‐BagWorkSession–Anchorage,Alaska(August29,2011);and

● HVDCConverterDemonstration–Lawrenceville,NewJersey(November14,2011).

AppendixIprovidesthefollowingdetailedinformationregardingSAGmeetingsanddiscussions:

● ListofSAGmembers;

● SummaryofSAGroleandpolicies;

● SummaryofkeyinformalcorrespondencebetweenSAGmembersandPolarconsultoverthecourseoftheproject;

● HandoutsfromthethreeSAGmeetings;and

● Handoutsfromothermeetingsandoutreachactivitiesconductedoverthecourseoftheproject.

AdditionaldetailsassociatedwiththeSAGmeetingsandproceedingsarepresentedinAppendixI.TranscriptsoftheSAGmeetingsareavailableuponrequest.


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3.0 HVDCTRANSMISSIONSYSTEMDESCRIPTION

HVDCtransmissionsystemscantakeonawidevarietyofconfigurations.Thissectiondescribesthoseconfigurationsrelevanttolow‐powerHVDCapplicationsinruralAlaskaapplications.

● Section3.1providesageneraloverviewofthehistoryofHVDCpowertransmissionandthemajorcomponentsofanHVDCtransmissionsystem.

● Section3.2providesageneraloverviewofthedifferentconfigurationsofHVDCsystemsforpowertransmissionapplications.

● Section3.3providesacomparisonofHVDCandACpowertransmissionalternatives.

● Section3.4providesadescriptionofoverheadlinealternativesforACandHVDCapplications.

● Section3.5providesadescriptionofsubmarinecablelinealternativesforACandHVDCapplications.

3.1 HVDCBACKGROUND

ThomasEdisonpioneeredthefirstutility‐scaleapplicationofelectricpowerinNewYorkCityinthe1880swithadirectcurrent(DC)electricutilitysystem.Concurrently,GeorgeWestinghousewasmarketinganACelectricutilitysysteminventedbyNikolaTesla.ACwasbettersuitedtosteppingupvoltages,whichisvitaltoeconomicalelectrictransmissionacrosstownandbetweencities.Bythe1890s,Westinghouse’sACsystemhadprevailedoverEdison'sDCsystem,andACbecametheindustrystandard.

Inthe1950s,technologicaladvancesenabledDCsystemstoreentertheelectricutilityindustry.Withthecommercializationofthemercuryarc‐valve,voltagetransformationofDCandconversionbetweenDCandACelectricityonalargescalebecamecost‐effective.ThisallowedutilitiestobeginusingHVDCtransmissionlinksintheirsystems.

BecauseofthehighcapitalcostoftheseearlyHVDCconverters,utilityusageofHVDCremainedlimitedtotransmissionfunctions.ACremainedtheindustrystandardforelectricitygeneration,distribution,andconsumption.

Today,HVDCconvertertechnologyhasadvancedtousehighefficiencysolid‐statehardware,andHVDClinksareusedforelectricaltransmissionthroughouttheworld.Thesmallestavailableutility‐gradeHVDCsystemsaredesignedtotransmitapproximately50MW2.Asaresult,thecurrentcommerciallyavailableHVDCconvertersareoversizedandprohibitivelyexpensiveforAlaskanintertiesthattypicallyrequirethetransferoflessthan1MW.Figure3‐1isanimageofalargeHVDCstation.

2“HVDCLite,”distributedbyABB,isoneexampleofthesmallerutility‐gradeHVDCsystems.


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HVDCtransmissionsystemsincludethefollowingmajorcomponents:

● HVDCConverterStations.EachconnectionpointbetweentheHVDCtransmissionlineandaloadcenterrequiresanHVDCconverterstation.TheconverterstationconvertstheHVDCelectricityintoACelectricitythatcanbemovedthroughalocalpowergridandused.Theconverterstationincludesthepowerconverters,groundingstations,communicationsandcontrolsystems,andprotectiveequipmentasrequiredbytheparticularsystemdesignrequirements.ThepowerconvertersarediscussedinAppendixF.ThegroundingstationsarediscussedinAppendixE.

● HVDCTransmissionLine.TheHVDCtransmissionlineistheoverheadwire,submarinecable,undergroundcable,orcombinationofthesethatconnectstheconverterstationstogetherandformsthetransmissioncircuit.Theconfigurationanddesignofthetransmissionlinewilldependonlocalconditionsandsystemrequirements.OverheadtransmissionlineconceptsarediscussedinAppendixC.SubmarinecabletransmissionlineconceptsarediscussedinAppendixD.

● ControlsandCommunications.TheHVDCtransmissionsystemrequiresameansofcommunicatingbetweentheconverterstationsandthecontrolthesystem.ThesimplestcontrolandcommunicationschemewouldusetheDClinevoltageasacontrolsignal.Thiswouldbesuitableforapoint‐to‐pointHVDCsystemthatfeedspowerinonedirection.Powerreversalovertheintertiewouldbepossiblewithmanualintervention.ControlandcommunicationoptionsforHVDCsystemsarediscussedinAppendixG.

Figure 3-1 Typical Large HVDC Station

5,000MW+/‐800kVHVDCYunnan‐GuangdongConverterStation.(TDW,2012)


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3.2 HVDCSYSTEMCONFIGURATIONS

ThevarioussystemconfigurationsforHVDCcanbeclassifiedintothreedifferentcategories,withseveraloptionswithineachcategory.Thethreecategoriesandmajoroptionsareshownbelow.Eachcategoryisdescribedinmoredetailinthefollowingsections.

TypesofHVDCUtilityPowerSystems

HVDCApplication‐HowtheHVDCtechnologyisused:

● Point‐to‐PointDCPowerTransmission

● MultiterminalDirectCurrent(MTDC)PowerTransmission

HVDCCircuit‐Howtheelectricityistransported:

● MonopolarwithSingle‐WireEarthReturn(SWER)

● MonopolarwithMetallicReturn

● Bipolar

IntertieType‐Howthewirestransportingtheelectricityareconfigured:

● Overhead

● Submarine

● Underground

3.2.1 HVDCSystemApplications

TherearethreebasicapplicationsofHVDCtechnologyintoday’selectricutilityindustry.Theseare:

● Point‐to‐pointpowertransmission.ThemajorityofHVDCsystemsinusetodayarepoint‐to‐pointtransmissionsystems.Thesetransportbulkenergy(100sor1,000sofMWs)overlongdistances(100sor1,000sofmiles)moreefficientlythanACtransmissionsystems.

Point‐to‐pointnetworkswillbeasignificantapplicationforthelow‐powerHVDCtechnologybeingdevelopedwiththisproject.

● Multiterminalpowertransmission.MTDCnetworksareamoreflexibleandcomplicatedapplicationofHVDCtransmissiontechnology.Insteadofthetwoterminalsinaconventionalpoint‐to‐pointHVDCsystem,MTDCsystemshavemorethantwoterminalsandcanroutepowertoorfromtheseterminalsasneeded.MTDCsystemsarecurrentlyreceivingsignificantindustryinterestastechnologyevolvestohandlethesemorecomplicatedsystemsandregionalgridsdemandthesuperiorperformanceandenhancedcapabilitiesthatMTDCsystemsofferoverACtransmissionnetworksforcertainapplications.Thereareahandfuloflarge‐scaleMTDCsystemsplannedorinoperation.ExamplesincludetheQuebec–NewEnglandMTDCsystemandtheSardinia–Corsica–ItalyMTDCsystem.

ManyregionalenergysolutionsinruralAlaskausingHVDCwillbeintheformofMTDCnetworks.ThepowerconvertersdevelopedforthisprojectcansupportMTDCoperation,providedsuitablecontrolsystemsandprotectiveequipmentarepresent.MTDCsystemsandcontrolconsiderationsarediscussedingreaterdetailinAppendixG.

Atthemostabstractlevel,anelectricalcircuitrequirestwocurrentpathways,normallymetalwires.Onewiregoesfromthepowersupplytotheload,andasecondwiregoesfromtheloadback


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INCREASING COST AND COMPLEXITY

1. Monopolar with earth return (SWER) 2. Monopolar with return conductor 3. Bipolar

tothepowersupply.Bothsingle‐phaseACandDCcircuitsrelyonthisbasicconfiguration.Thewirefromthepowersupplytotheloadisusuallyatanincreasedvoltagerelativetoground,andsoitisinsulatedforsafetyandtopreventshortcircuits.Thewirefromtheloadbacktothepowersupplyisusuallyatamuchlowervoltagerelativetogroundandisusually,butnotalways,insulated.

TherearethreetypesofHVDCcircuitsinusearoundtheworld.Eachofthesecircuitsmayutilizeoverheadwires,undergroundcables,submarinecables,oracombinationofthese.ThesethreecircuitsarelistedonFigure3‐2anddescribedonthefollowingpages.

Figure 3-2 Three Types of Interties Used in HVDC Systems

MorecomplexHVDCcircuitconfigurationsnormallyincorporateelementsofthesimplercircuitsforefficiency,reliability,redundancy,and/orsafety.Forexample,allbipolarHVDCsystemsincludeearthelectrodesandsometimesagroundconductorsotheycanoperateeitherpoleinmonopolarormonopolarSWERmodeduringmaintenanceoremergencies.Generally,themorecomplexbipolarcircuitconfigurationsareusedforlarge,importantintertieswheretheincreasedreliability,efficiency,andpowerthroughputcapabilityjustifythehighercostofthesesystems.

3.2.1.1 SingleWireEarthReturn(SWER)CircuitsSWERcircuitsusethesubsurfacegeologyasareturncurrentpathway.Seareturncircuitsaresimilartoearthreturncircuits.Theonlydifferenceisthatthesea,oranywaterbody,isusedasthepredominantreturncurrentpathway.Parallelpathways,suchastheseabed,arealsoavailableforcurrentflow.TheprimaryadvantagesofferedbySWERcircuitsinclude:

● Lowercosts(eliminatethesecondconductor).

● Higherefficiency(lowerelectricallosses).

TheprimaryconcernsassociatedwithSWERcircuitsinclude:

● Avoidingaccelerated“inducedcurrent”corrosionofburiedmetallicobjects.

● Aswithallelectricalsystems,safety.SWERcircuitsarewidelyusedforutilitytransmissionanddistributionofelectricityallovertheworld.NumerousHVDCintertiesareSWERcircuits,consistingofasinglehigh‐voltagecableandanearthorseareturntocompletethetransmissioncircuit.ManyoftheseareinstalledinclimatesandconditionssimilartoAlaska,notablyinScandinavia.Inmanynations,single‐phaseACSWERcircuitsareacceptedpracticeandareindustrystandardforservingruralareas.


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Twosingle‐phaseACSWERcircuitshavebeensuccessfullybuiltandoperatedinAlaska.TheseACSWERcircuitsdemonstratethatSWERisaproven,beneficial,andappropriatetechnologyforruralAlaskatransmissionapplications.

3.2.1.2 MonopolarHVDCCircuitUsingSWER

AmonopolarHVDCintertieusingSWER(seeFigure3‐3)forthereturnpathwaywillgenerallybethelowest‐costalternativeforHVDCpowertransmissioninruralAlaskaapplications.Thiscircuitconfigurationwillconsistofthefollowingmajorcomponents:

● AC/DCconvertermoduleinthegeneratingvillage.

● High‐voltageconductor.Thiscanbeanoverheadline,buriedcable,orsubmarinecable.

● DC/ACconverterinthereceivingvillage.

● Groundingelectrodesinbothvillagestocompletetheintertiecircuitusingearthreturn.

Figure 3-3 Monopolar HVDC Intertie Using SWER

TherearenumerousexamplesofmonopolarHVDCintertiesusingSWERcircuits.The500‐MWsubmarineHVDClinkcompletedbetweenVictoriaandTasmania,Australia,in2006isoneexampleofarecentlyconstructedSWERHVDCsystem.BipolarandmonopolarHVDCcircuitsarenormallydesignedtooperateinamonopolarSWERconfigurationwhenneededtomaximizesystemreliability.


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3.2.1.3 MonopolarHVDCCircuitwithReturnConductor

AmonopolarHVDCintertiewithareturnconductor(seeFigure3‐4)issimilartoamonopolarSWERHVDCintertie.Theprimarydifferenceisthattheearthreturnisreplacedwithadedicatedreturnconductortominimizeearthcurrentsinducedbytheintertie.Often,suchintertieswillstillhavetheearthelectrodesnecessarytooperateinSWERmodeandwilloperateinSWERmodeduringmaintenanceoremergencysituations.ThisHVDCcircuitconfigurationincludesthefollowingmajorcomponents:

● AC/DCconvertermoduleinthegeneratingvillage.

● High‐voltageconductor.Thiscanbeanoverheadline,buriedcable,orsubmarinecable.

● DC/ACconverterinthereceivingvillage.

● Returnconductor.Thiscanbeanunder‐builtlineonthehigh‐voltagepoles,aseparatecable,orincorporatedintothesamecableasthehigh‐voltageconductor,suchasaconcentricneutralonanACcable.

● Groundingelectrodesinbothvillages.Thesewillnotnormallybeusedtocompletetheintertiecircuit,buttheywillbeusedduringmaintenanceoremergencies.

MonopolarreturnconductorsarewarrantedinareaswhereaSWERcircuitisnotviableordesirable.Generally,thisisduetotheriskofinducingcorrosioninburiedmetallicutilities.Thelackofsuitablegroundconditionsforeconomicalearthelectrodeswouldalsowarrantuseofareturnconductor.Usinganreturnconductorwiththesameelectricalresistanceasthehigh‐voltageconductorwillnearlydoubletheconductorlossesrelativetoaSWERtransmissioncircuit.

Figure 3-4 Monopolar HVDC Intertie with Return Conductor (SWER-capable for Backup)


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3.2.1.4 BipolarHVDCCircuit

AbipolarHVDCintertie(seeFigure3‐5)isgenerallythemostcostlyandmostreliableHVDCcircuitconfiguration.Itemploystwoparallelhigh‐voltageconductors,oneoperatedatpositivevoltageandthesecondatnegativevoltage.Thesystemrequirestwoconvertersateachendoftheintertie(fourtotal),comparedtooneconverterperendformonopolarcircuits(twototal).Thus,thebipolarHVDCconfigurationincludesthesemajorcomponents:

● TwoAC/DCconvertermodulesinthegeneratingvillage.One(+)andone(–).

● Twohigh‐voltageconductors.Thesecouldbeoverheadlines,buriedcables,orsubmarinecables.

● Athirdneutralconductortocarryanycurrentduetominorimbalancebetweenthepowertransmissionlevelsonthepositiveandnegativepoles.Somebipolarsystemsdonothaveaneutralconductorandinsteadrelyonthegroundingelectrodestobalancethepoles.

● TwoDC/ACconvertersinthereceivingvillage.One(+)andone(–).

● Groundingelectrodesinbothvillages.Thesewillnotnormallybeusedtocompletetheintertiecircuit,buttheywillbeusedtobalancethesystemandforSWERoperationduringmaintenanceoremergencies.

TheadditionalcostsofabipolarHVDCintertiearelargelyduetotheadditionalconvertersandthesecondhigh‐voltageconductor.AbipolarHVDCintertiewillberoughlytwiceascostlyasamonopolarHVDCintertie,butwithtwicethecapacityandincreasedreliability.

Theprincipaladvantageofabipolarintertiecomparedtoamonopolarintertieisincreasedreliability.Ifsomethingbreaksononeofthetwopoles,theotherpolecanbeoperatedasamonopolarintertie.Thiswillreducethepowertransfercapability,buttheintertiecancontinuetofunction.

FormanyruralAlaskaapplications,theadditionalcostofbipolarcircuitsisnotjustified.Operatingbackupdieselgeneratorsinvillageswouldbemorecost‐effectivethanconstructingabipolarHVDCintertie.

Figure 3-5 Bipolar HVDC Intertie (SWER-capable for Backup)


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3.2.2 HVDCIntertieTypes

HVDCintertiescanbebuiltusingoverheadwires,submarinecables,orundergroundcables.Combinationsofthesecanbeusedforasingleintertie.OverheadwireintertieoptionsarediscussedinSection3.4andAppendixC.SubmarinecableintertieoptionsarediscussedinSection3.5andAppendixD.UndergroundcableoptionsarediscussedinAppendixG.


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3.3 COMPARISONOFACTOHVDCTRANSMISSION

ThefollowingabbreviatedcomparisonispresentedtoillustratewhenanHVDCintertieisanticipatedtobeagoodalternativetoacomparableACintertieinruralAlaskaapplications.AmoredetailedcomparisonispresentedinAppendicesAandB.

HVDCAdvantages:

● Lowerper‐mileoverheadtransmissionlinecostthanAClines;

● Abilitytouseundergroundorsubmarinecablesforlongdistances;

● Bettercompatibilitywithmigratorybirdsduetofeweroverheadconductors(1or2wiresinsteadof3or4wires);

● Asynchronousconnection;and

● Lowerper‐mileconductorenergylosses.

HVDCDisadvantages:

● AnHVDCconverterismoreexpensive,requiresmoremaintenance,andislessreliablethanacomparableACtransformer;

● Convertercostsareabarriertoservingloadsalongthetransmissionlineroute;

● UnconventionaltechnologyandlimitedequipmentsupplierscomparedtoAC;

● HVDCconvertersgenerallyhavehigherenergylossesthanacomparableACtransformer;and

● HVDCintertiesmayhavefewerfundingopportunitiesthanconventionalAClinesbecausetheyareuncommon.

Implications:

● Ifanintertiemustemploylong‐distancesubmarineorburiedcables,HVDCoffersatechnicallysuperiorsolutiontoAC.ACcableintertiesarenottechnicallyfeasibleforlong‐distancetransmissionsystems.

● Wherebothsystemsaretechnicallyfeasible,thedecisionislargelyeconomic.AnHVDCintertiewillhavehigherterminalcostsandlowerper‐milecosts.Accordingly,anACintertieismorecost‐effectiveforshortinterties,andHVDCismorecost‐effectiveforlonginterties.Thelongertheintertie,thegreaterthecostsavingsofanHVDCversusACsystem.Theeconomiccrossoverpointisprojectspecificbutforthescaleofintertiesunderconsiderationinthisreport,itwillgenerallyoccuratadistanceof6and31miles.

● SincetheHVDCconvertersdevelopedunderthisprogramusenewtechnology,andbecauseitrepresentsadeparturefromconventionalACtransmissionsystems,substantialsavingswillbeafactorinencouragingutilitiestoadoptthistechnologyinlieuofprovenbutmorecostlyintertiesolutions.

● MostACintertiesareoverheadandmaynotbeenvironmentallyacceptableinmanypartsofAlaska.HVDCintertiesareeitherburiedorhavefewerwiresandstructuresandmaybemoreacceptablewithinrefugesandothersensitiveareas.


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3.4 OVERHEADINTERTIEALTERNATIVES

3.4.1 ConventionalACInterties

Thetypicalcostforconstructingaconventionaloverheaddistribution‐classACintertieinruralAlaskacanrangefromaslittleas$100,000permileinareaswithgoodlogisticsupportandtransportationinfrastructure(roadsystem,southeast)toover$600,000permile3inruralpartsofthestatewithchallenginglogisticsandlittleornotransportationinfrastructure(remoteinterior,northwest,orYukon‐Kuskokwimdeltaregions).Becauseofthisprohibitiveexpense,relativelyfewruralintertieshavebeenbuilt.

ThehighcostofruraloverheadACintertiesistheresultofseveralfactors.TwosignificantcostcontributorscommontomanyAlaskanintertieprojectsarelogisticsandfoundations.ACsystemsrelyonmulti‐wiretransmissionlines;thisleadstohighmaterialscostsandhighloadsplacedonstructuresandfoundations.ThestructuresneededtosupportthemultipleaerialwiresofanACsystemarecostly.TheresultingACintertieusuallyhasshortspans,250to400feetbeingtypical,thusresultinginmanytransmissioncomponentssuchaspoles,hardware,wire,andfoundationsthatmustbepurchased,shipped,installed,andmaintained.

Whenthecostsofshipping,geotechnicalconditions,constructionfactors,logisticsandenvironmentalrequirementsareallfactoredin,conventionalACconstructionoftenresultsinaprohibitivelyexpensiveintertie.Asaresult,manyruralcommunitiesaredeniedtheopportunitytobenefitfrominterconnectiontoeachotherorlocalenergyresources.

3.4.2 HVDCTransmissionInterties

PolarconsulthasinvestigatedalternativestoACintertiesandfoundthatinmanyapplications,HVDCtransmissionsystemsofferthemosteconomicalsolution.

ReplacingaconventionaloverheadACthree‐orfour‐wiretransmissionlinewithaone‐ortwo‐wireHVDCtransmissionlinehassignificantcostadvantages.Thechangeinoverheadinfrastructureresultsinreducedstructuralloadsthusallowingfewersupportstructurespermileoftransmissionline.ThedecreaseinmaterialsandconstructiontimeistheprimaryreasonoverheadHVDCintertiesaremoreeconomicallyviablethanACinterties.

AmonopolarHVDCintertiedesignedasaSWERcircuitneedsonlyasinglewirealoft,whichsignificantlyreducestheloadscomparedwithathree‐orfour‐wireACintertie.Usingasinglewireprofoundlysimplifiesthetransmissionlinedesign,whichtranslatestosignificantcostsavingscomparedwithanACline.

BecauseSWERcircuitsinduceareturncurrentintheearth,theyrequirespecialattentioninthedesignandplanningphasetoavoidadverseeffectsfromthisearthcurrent.Theprimaryconcernsare(1)thesteppotential4intheimmediatevicinityofthegroundingstationsand(2)acceleratedcorrosionofburiedmetallicobjectsinthevicinityofthereturncurrentpathwaysthroughtheearth.

3SeeSectionB.6.1inAppendixBforcostbasisinformation.4Avoltagegradientthatoccursatthegroundsurfaceduetoearthreturncurrents.Ifthevoltagegradientishighenough,itcanposeahazardtopeopleorwildlifesteppinginthevicinity.


MAY 2012 PAGE 18

InmostruralAlaskalocalities,theseconcernscanbereadilyaddressedthroughproperplanningandsystemdesign.

Becauseofthesespecialfactors,SWERcircuitsarenotallowedbytheNationalElectricalSafetyCode(NESC),whichistheapplicablecodeforelectricutilitytransmissionanddistributionsystems.PolarconsulthasdiscussedthisHVDCsystemandconceptindetailwiththestatecodeauthorityandfindsthatSWERcircuitscanbeapprovedonaproject‐specificbasisbyissuanceofacodewaiver.ThereisprecedentforcodewaiversbeingissuedforSWERsystemsinAlaska.TheuseofSWERcircuitsisdiscussedfurtherinAppendixEofthisreport.

Asanalternativetousinganearthreturncircuit,two‐wiremonopolarHVDClines(usinganoverheadwireasthereturncircuit)alsoachieveacostsavingsrelativetoACintertiesalthoughthesavingswilltypicallybelessthanforanHVDCSWERtransmissionline.

BipolarHVDCintertiesrequiretheuseoftwoadditionalconvertersbutcantransfertwicetheenergyofacomparablemonopolarsystem.Intheeventofaconverterfailureorlossofaconductor,abipolarsystemcanbeconfiguredtooperateasamonopolarSWERormonopolartwo‐wiresystem.Thisofferssignificantreliabilityadvantages;however,italsoincursthecostoftheadditionalconvertersandsecondhigh‐voltageconductor.Theadvantagesoftheincreaseincapacityandreliabilityaretheprimaryreasonsforuseofbipolarsystems.


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3.5 SUBMARINECABLEINTERTIEALTERNATIVES

AnotheradvantageofHVDCtransmissionoverACisitsintrinsicabilitytocarryenergybyburiedorsubmarinecableoverlongdistanceswithoutthetechnicallimitationsandadditionalequipmentrequiredforsimilartransmissionbyAC.MonopolarHVDCusingasinglecablecanconnectvillagesseparatedbylakes,bays,fjords,orlandswhereoverheadtransmissionisnotpractical,cost‐effective,ordesirable.Forthisreason,low‐powerHVDCtechnologyhassignificantimplicationsforinterconnectingcommunitiesinAlaskaseparatedbywaterbodies,particularlyinthesoutheast.

CabletricitywasretainedbyPolarconsultasasubconsultanttoinvestigatesubmarinecablesoptimizedforusewiththisHVDCsystem.AppendixDincludestheCabletricityreportdetailingresultsoftheirinvestigations.

Thereportbeginswithadescriptionoftheelectricalsystemtowhichthecableswillbeconnected,andthenadvancestotheregionalenvironmenttheymustwithstandandontodescriptionsofsubmarinecablestandards,cabledesigns,typicalinstallationmethods,andcostestimatesforacasestudy.

Cabletricityevaluatedsubmarinecablessuitablefor1‐MWmonopolarHVDCintertiesat50kilovolts(kV),withpotentialupgradeoftheconverterstationsto5‐MWserviceinamonopolarcircuit.Cabletricityalsoevaluatedthefeasibilityandcostofintegratingopticalfibersintothepowertransmissionsystemtoservethecommunicationsneedsofruralcommunities.Tomakethissystempractical,simplicityandreliabilityarecriticaldesignconsiderations.

Cabletricity’sinvestigationsfocusedonsinglecoreinsulatedconductorsubmarinecableswithearthorseareturnthatwouldbegenerallysuitablefortheruggedanddeepinter‐islandandfjordcrossingstypicalofsoutheastAlaska.Theobjectiveistoidentifysuitableconventionalorinnovativesubmarinecabledesignstomeettheoverallprojectobjectiveswherewatercrossingsarerequired.


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4.0 HVDCCONVERTERSTATIONS

4.1 OVERVIEW

TheHVDCconverterstationswillincludethemajorcomponentslistedbelow:

● HVDCpowerconverterssuchasthosebeingdevelopedbyPPS;

● Converterenclosures,whichmayconsistofdedicatedenclosuresoruseofanexistingbuilding,suchasanexistingpowerplant;

● Protection,control,andswitchingequipmentontheACandHVDCsidesoftheconverters;

● ACtransformers,dependingontheACinterfacevoltageandwiring;and

● Groundingstations,includingthegroundconductorfromtheconverterstationtothegroundingstation.

4.2 CONVERTERDEVELOPMENTOVERVIEW

PolarconsultsubcontractedwithPPSforthedevelopmentoftheHVDCpowerconverters.PPSwastaskedwiththedevelopmentofonefull‐scaleandfull‐functionality1‐MWpowerconverter,consistingoftwo500‐kilowatt(kW)modules.Developmentworkincludedpreparationofspecifications,design,construction,andtestingoftheprototypeconverter.

TheHVDCconverterisa1‐MWpowerconvertercapableofbidirectionalpowerconversionbetweenthree‐phase480voltsalternatingcurrent(VAC)and50kVHVDC.TheconvertercapacityisappropriatetosupplytheelectricalneedsofmostAlaskavillageseconomically.Incontrast,existingHVDCpowerconvertersystemsareonlyavailableatmuchlargertransmissioncapacities,startingatapproximately50MWandextendingupto1,000sofMWsofcapacity.

Each500‐kWPPSconverterconsistsoftwomodules:anair‐cooledlow‐voltagecabinet(Figure4‐1),andanoilcooledhigh‐voltagetank(Figure4‐2).ACpowercablesconnecttothelow‐voltagecabinet,whichconditionsthepowerandtransformsittoaspecialhigh‐frequencyAC,whichistransmittedtothehigh‐voltagetankviapowercable.Thehigh‐voltagetanktransformsthehigh‐frequencyACto50kVDC.Thehigh‐voltagetankhastwobushingsthatoutputupto500kWat50kVDC.Eitherbushingcanbegroundedtoproduceapositive50‐kVHVDCoutputoranegative50‐kVHVDCoutput.

MultiplePPSHVDCconverterscanbe“paralleled”toachievehigherpowertransmissioncapacitieswhereneeded.BasedonPhaseIIdevelopmentwork,thepriceofacommerciallyproduced1‐MWHVDCpowerconverterisestimatedtobe$250,000.Atleasttwo1‐MWconvertersareneededforacomplete1‐MWHVDCtransmissionsystem.

PPShassuccessfullydemonstratedoperationandpowerflowatthefull50kVDCinbothinverter(HVDCtoAC)modeandrectifier(ACtoHVDC)modeinacontrolledtestfacilitysetting.Thesetestingeffortsvalidatethedesignandbasicfunctionalityoftheconverter.

Inthecourseoftesting,PPSidentifiedtwohardwareproblemsthatpreventedfull‐powertestingoftheprototypeconverters.PPShasinvestigatedtheseproblemsandidentifiedtheactionsnecessarytocorrectbothproblems.TheproblemsandsolutionsarediscussedinAppendixF.


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Thefollowingfiguresillustratetheconverterfeatures:

o Figures4‐1and4‐2showthetwobasicmodulesthatmakeupacomplete500‐kWconvertersystem.ThesearefurtherdiscussedinAppendixF.

o Figure4‐3showsthetestsetupfortestingofthecentralresonantlinkcircuitinthehigh‐voltageDCtransformer.

o Figure4‐4showsthein‐airhighpotential(hi‐pot)testsetupofthehigh‐voltageDCtransformerassembly.Thistestidentifiedsomeinsulationdefectsthatwerecorrected.ThetestdemonstratedthattheDCtransformerassemblywillwithstandthevoltagesexperiencedatfulloperatingvoltageof50kVDC.

o Figure4‐5showsthedrysystemtestsetupandschematic.BeforetheDCtransformerwasimmersedinoil,itwastestedatlowvoltageinairtovalidatefunctionandfacilitatetroubleshooting.Thiswasprimarilydoneforconvenience,toavoidthedelaysandmessassociatedwithrepeatedlyimmersingtheDCtransformerinoilandremovingit.

o Figure4‐6showsacomplete500‐kWconvertermodule,consistingoftheHVDCtankandthelow‐voltagealternatingcurrent(LVAC)cabinet.

o Figure4‐7showsfourhigh‐voltagemeasurementprobesusedtomonitorthevoltagesatdifferentpointsintheDCtransformer.ThetestshowedexcellentvoltagesharingbetweentheDCtransformerstages,indicatingthatthesystemisperforminginaccordancewithdesign.Uniformvoltagesharingisakeysuccess,asitmeansthepowerelectronicscomponentswillnotbesubjectedtounevenvoltagesstresses.Excessivevoltagestressescouldseverelyshortenthelifeofthecomponents,reducingthereliabilityoftheconverter.


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Figure 4-1 Low Voltage Alternating Current (LVAC) Enclosure: Mechanical Layout

Notes:Cabinetsize:66”Wx42”Dx66”H;Cabinetweight:Approximately2,200pounds.


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Figure 4-2 HVDC Transformer Tank: Mechanical Layout

Notes:Tanksize:88”Wx39”Dx59.25”H;Tankweightwithoil:4,200pounds.


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Figure 4-3 Central Resonant Link Test Setup

Figure 4-4 Hi–Pot Test Setup for HVDC Transformer


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Figure 4-5 Dry System Inverter Mode Test Schematic and Setup


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Figure 4-6 System #1 HV Tank and LV Enclosure

Figure 4-7 System #1 Showing HV Measurement Probes


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4.3 ADDITIONALEQUIPMENT

4.3.1 ConverterEnclosure

WhiletheconverterspecificationspermittheconverterstobeinstalledoutdoorsinmostAlaskaenvironments,itisassumedthattheconverterswillbeinstalledinsideanenclosure.Thiswillprovideforacontrolledoperatingenvironmentandgreatersecurityfortheconverters,extendingtheirusefulservicelife.

Theconceptualdesignassumesthatamodular,prefabricatedenclosurewillbesenttothecommunitywiththetwo500‐kWpowerconverterunitsalreadyinstalled.Thisconvertermodulewillthenbesetinplaceonasuitablefoundation.

IncommunitiesthatwillbeprimarilyservedbyanHVDCintertie,itmaybeappropriatetolocatetheconvertersinsidetheexistingpowerhouseorothersuitableexistingstructure.Thiswouldhavethefollowingadvantages:

● Theexistingpowerhousemayalreadyhaveasuitablestep‐downtransformersizedforthefullcommunityload;

● Wasteheatfromtheconverterswouldprovideallorpartoftheheatforthepowerplantbuilding;and

● Achievesprojectcostreductionbyeliminatingtheneedforadedicatedconverterenclosureandpurchasingorleasinglandtositetheconverter.

4.3.2 ProtectionandSwitchyardEquipment

SwitchgearwillbeneededontheACsideoftheconverterstoisolateandprotecttheconverterfromtheACgridandtomonitorpowerflowbetweentheconverterandthegrid.

Similarisolation,protection,andmonitoringequipmentisneededontheHVDCsideoftheconverter.Ataminimum,manualdisconnectswitches(nonloadbreak),surgearrestors,andprotectivefusesareneededontheHVDCside.Moreautomatedcontrolapparatuscanalsobeused,butatincreasedcost.

4.3.3 ACTransformers

Thegridinterfaceonthepowerconvertersisthree‐phase480‐voltAC.Incommunitieswheretheconverterisconnecteddirectlytothe480‐voltpowerplantbus,notransformerisrequired.Incommunitieswheretheconverterconnectstothelocaldistributiongrid,astep‐uptransformerisrequired.Thetransformerwilltypicallybeathree‐phase480/12.47‐kVtransformer.

4.3.4 GroundingStations

AgroundingstationwillneedtobeprovidedateachHVDCconverterstation,regardlessoftheHVDCcircuitconfiguration.Theconceptualdesignofa1‐MW,50‐kVDCgroundingstationispresentedinAppendixE(FigureE‐1).


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5.0 DESIGNCONCEPTSFOROVERHEADINTERTIES

ThefollowingsummarizesdesigncriteriadevelopedfortheconceptualdesignoftheHVDCoverheadintertielines.DesigncriteriaandconceptualdesignsarepresentedindetailinAppendixC.

5.1 OVERHEADDESIGNAPPROACH

Theoverheadintertiedesignconceptspresentedrequiredconsiderationoftypicalsiteconditions,codes,utilityandlenderrequirements,constructionmethodologies,standarddesignpractices,andprojecteconomics.ThefollowingtwodesignapproachesforoverheadHVDCintertieshavebeenevaluated,eachwithacapacitytosupply1MWthroughamonopolar50‐kVDCsystem:

5.1.1 RUSDesignApproach,ModifiedforHVDCInterties

ThefirstconceptualdesignapproachisbasedontheuseofstructuresthatareconstructedinaccordancewithUSDARUS‐typeconstruction(RUSstandardpractice)forconventional12.4/24.9‐kVACdistributionlines.5TheseRUSstandardpracticesarecurrentlyusedtodevelopACintertiesthroughoutAlaskaandarewidelyacceptedbytheutilityindustry.HVDCtransmissionrequiresfewerconductorsthanAC,resultinginreducedloadsonthesupportingstructures.Asaresult,theconceptualdesignsdevelopedusingtheRUSapproachhavelongerrulingspansthantypicalAClines.ThisresultsinfewertransmissionstructuresfortheHVDCintertieandanassociatedcomparativereductioninconstructioncost.

5.1.2 Alaska‐SpecificDesignApproachforHVDCInterties

ThesecondconceptualdesignapproachtakesthelogisticandtechnicalchallengesofconstructioninruralAlaskaintoconsiderationandfocusesonmethodstoreduceconstructioncostswithoutcompromisingperformanceorlong‐termmaintainability.Thisdesignapproachincorporatescost‐savingfeaturesmadepossiblethroughHVDC‐specificdesignalternatives,materials,andconstructionmethods.DesignfeaturesofthisconceptincludetheuseofguyedcompositestructurestoallowsignificantlylongerrulingspansthanispossiblewithRUSstandardpractice.Thereducednumberofstructures,lesscostlyfoundations,andreducednumberofconductorsallresultinadditionalsavingscomparedwithintertiesbuiltinaccordancewithRUSstandardpractices.

ThefollowingthreeHVDCtransmissioncircuitconfigurationsareconsideredforeachoftheHVDCconceptualdesignapproaches:

● Monopolarsingle‐wiretransmissionwithearth‐returnpath(SWER);

● Monopolartwo‐wiretransmissionwithmetallicconductor‐returnpath(TWMR);

● Bipolartwo‐wiretransmission(2‐MWcapacity).

5 Inthisreport,theterm“RUSstandardpractice”referstooverheadintertielinedesignsbasedonthemethodsand

materialspresentedinRUSdesignmanualsfortransmissionanddistributionlineconstruction,includingbutnotlimitedto:REA,1982,RUS,1998,2002,2003a,2003b,2003c,and2009.


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SchematicfiguresareprovidedforeachoftheseconceptualdesignsinAppendixC.DetailedreportsthataddressvarioustechnicalaspectsoftheassumedconditionsandloadingsusedtodeveloptheseconceptualdesignsareprovidedasattachmentstoAppendixC.

5.2 GEOTECHNICALCONDITIONS

Basedontheanalysisdescribedbelow,conceptualfoundationdesignalternativesforaguyedpoleutilizethreethermoprobemicropilesforthepolebaseandhelicalanchorsfortheguys.TheoverheadsystemtestsiteinFairbanks,Alaska,featuresinstallationsofbothoftheseprototypefoundations.

5.3 ENVIRONMENTALLOADS

FivestandardNESCloadingcaseswereanalyzedforeachconceptualdesign.TheseloadcasesareconsideredsufficientformostruralAlaskaoverheadintertieapplications.Specificlocationsmaybesubjecttohigherand/orlowerwindand/oriceloadings.6Exceptwherespecificallystatedotherwise,eachoftheconceptualdesignspresentedinthissectioncomplywiththemoststringentoftheseloadconditions.

5.4 CONSTRUCTION,RUSSTANDARDPRACTICETheconceptualdesignsofoverheadintertielinespresentedinthissectionhavebeendevelopedtotakeadvantageofthefollowingfactors:

● Alaskacontractors,linecrews,andutilitylinepersonnelarefamiliarwithRUSstandardpracticematerials,designs,andconstructionpractices,thustheywillbemorefamiliarwiththetechniquesandproceduresforbuilding,maintaining,andrepairingtheselines.

● AlaskaalreadyhasmanymilesofRUSstandard‐practicedistributionandtransmissionlinesbuiltandinservicethroughoutthestate.Utilitiesunderstandtheperformancerecordandissueswiththistypeoflineconstruction.

● Utilitylenders,whichincludesRUS,understandandacceptRUSstandardconstructionpractice,whichcansimplifyobtainingfundsforconstructingnewinterties.

Totakeadvantageofthesefactors,conceptualdesignforHVDCpreservedRUSstandardpracticeconstructiontotheextentpossible,modifyingthepoletopassemblytoaccommodatetheconductor(s),insulator(s),andclearancesforHVDCoperation.TherulingspanisalsoincreasedtotakeadvantageofthefewerwiresandreducedstructureloadsassociatedwiththeHVDCcircuitconfigurations.

StructuralanalysisofconventionaloverheadHVDCtransmissionstructures(adaptedfromRUSstandardpractice)wasperformedbyPolarconsult.AconceptualdesignsummaryispresentedinAppendixCforeachofthelineconfigurationsproposed.

6 Section4.6ofthePhaseIFinalReportprovidesasummaryofenvironmentalloadingsaroundAlaska(Polarconsult,

2009)


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5.5 CONSTRUCTION,ALASKA‐SPECIFICCONCEPT

TheconceptualdesignsofoverheadintertielinespresentedinthissectionhavebeendevelopedtoreduceconstructioncostsonruralAlaskainterties.Costreductionisachievedthroughspecialattentiontothefactorslistedbelow.

● Minimizingtherelianceonheavyequipmentthatmustbemobilizedtoaconstructionsite.Iflighterequipmentorlocalequipmentcanbeusedforconstruction,mobilizationcostswillbeless,reducingprojectcosts.

● Maximizingtheflexibilityinconstructionmethodsandseasons.Bydesigningfortheuseofsmallerequipment,greateruseofhelicoptersforconstructionsupport,andsimilartechniques,all‐seasonconstructionbecomespossible,providingincreasedflexibilityforconstructiontechniquesandmethods.Thisincreasedflexibilitycreatesnewopportunitiestoincreaseutilizationofequipment,increasecompetitionforlineconstructionprojects,andreduceprojectcosts.

Thesefactorshavebeenincorporatedintotheconceptualdesignelementslistedbelow.

● Useoftallerstructuresandlongerspans.BecauseHVDCcircuitsrequireonlyoneortwowires,theycanutilizelongerspansthanacomparablethree‐orfour‐wireACcircuit.Increasingspansreducesthenumberofstructuresandfoundationsforagivenlengthofoverheadline,whichreducescosts.Withthisapproach,tallerstructuresareneededtomaintainrequiredclearancesbetweentheconductorandtheground.

● Useofglass‐fiber‐reinforcedpolymer(GFRP)polesinsteadofwoodorsteelpoles.GFRPpoleshavebeenusedforover50yearsinelectricutilityapplications7buthavelittletonohistoryinAlaska’selectricutilityindustry.GFRPpolesarelighterthanwoodorsteelpolessotheycanbetransportedbyasmallhelicoptersuchasaHughes500orBellUH‐1“Huey.”Theyarealsorot‐resistantanddonotleachtoxicpreservativesintothesoilsaroundthepole.ThePhaseIIprojectincludeddemonstrationofafield‐friendlyspliceforGFRPpoles,whichpermitstallpolestobeshippedinpartsandassembledinthefield.ThissplicecanalsobeusedforfieldrepairofdamagedGFRPpoles.

● Useofguyedstructuresinareaswheregeotechnicalconditionspreventcantileveredpolesfrombeingdirectlyburiedinthesoil.Acceptedpracticeforsuchconditionsistodriveasteelpileupto40feetdeepandthenfastenawoodpoletothesteelpile.Installingthesteelpilerequiresmobilizingacraneorotherheavyequipmenttotheprojectsite.Aguyedstructurecanbeinstalledinsuchconditionswithamuchsmallerbasefoundation,astheguyscarrymostofthemoment,andthestructurebasemostlycarriescompressiveloads.

7Ibrahim,2000.


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5.6 TESTINGOFOVERHEADDESIGNCONCEPTS

TheconceptualoverheaddesignsdescribedinAppendixCusecommerciallyavailableandacceptedmaterials,designs,andconstructionmethods.CertainaspectsoftheconceptualdesignspresentedrepresentinnovationsinoverheadlinedesignthatdonothaveaprovenrecordwithintheutilityindustryinAlaskaconditions.Inordertoevaluatetheperformanceofthesecomponents,theywereinstalledatatestsiteinFairbanks,Alaska.ThissectionsummarizestheobjectivesandinstallationoftheFairbanksTestSite.DetailsofthetestprogramarepresentedinAppendixC.

5.6.1 TestObjectives

TheprimarytestobjectivesoftheFairbanksTestSitearelistedbelow.

● Demonstrateperformanceandassemblytimeofaspliceforaconstant‐sectionGFRPutilitypole.

● Demonstrateinstallationandperformanceofmicro‐thermopilepolefoundations.

● Demonstrateinstallationandperformanceofmicro‐thermopileguyanchors.

● Demonstrateinstallationandperformanceofscrewguyanchors.

● DemonstratetheinstallationandperformanceoftheoverallguyedGFRPpolestructure.

● Demonstratemaintenanceandoperationalcharacteristics.

5.6.2 TestSite

ThetestsiteislocatedonprivatepropertysouthofFarmer’sLoopRoadandnorthofCreamers’FieldinFairbanks.Thesiteconsistsofwarmice‐richsiltypermafrostsoils.Thesitehasanorganiclayerconsistingofdeciduousshrubsandblackspruce.Peatwaspresentatdepthsof1to5feetbelowgroundsurface.TheactivelayerinSeptember2011extendedtoadepthof3feet,withstandingwaterencounteredwithinthevegetativematnearthesurface.Geotechnicalconditionsatthesitearecharacteristicofmarginalwarmpermafrostconditions,asfurtherdescribedinAppendixC.

Figures5‐1through5‐4showtheinstallationofinnovativematerialsandsystemsatthetestsiteinFairbanks.


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Figure 5-1 Installing Micro-Thermopile for Guy Anchor

ContractorGeoTekAlaska,Inc.drillingaholeforinstallationofamicro‐thermopileata45‐degreebatterangleusingaGeoProbe8040seriesdrillrig.Themicro‐thermopilewillserveasaguyanchorfortheprototypeguyed

GFRPpoleinstallationattheFairbanksTestSite.(Polarconsult,2011).


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Figure 5-2 Assembling the Prototype GFRP Pole Splice

ContractorCityElectric,Inc.installingthefieldsplicefortheprototypeGFRPpole.40‐footand20‐footGFRPpolesegmentsweresplicedtocreatethe60‐footpoleerectedatthesite.Thespliceslidesoverthepolesegmentsandcarriesmomentthroughcontactbetweenthepoleandsplicewalls.Verticalloadsarecarriedthroughthebuttendsofthepolesegments.Noglueoradhesiveisnecessaryforthesplicetodevelopthefullmechanicalstrengthofthepole.Thescrewsservetopreventdifferentialmovementbetweenthepoleandsplice.(Polarconsult,2011)


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Figure 5-3 Prototype GFRP Pole Foundation During Installation

DetailofprototypeGFRPpolebaseattheFairbanksTestSite.Theadapterplatewasadjustedduringinstallationsothehingeisorientedinlinewiththeguyanchorinthedistance(orangeflagging).Thiswillallowuseofthe

guyanchortolowerthepolewithawinchifneeded.(Polarconsult,2011)


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Figure 5-4 Prototype Pole at the Fairbanks Test Site

ViewoftheprototypeguyedGFRPpoleinstalledattheFairbanksTestSite.Thisphotographistakenatadistanceofapproximately25yardsfromthe60‐foot‐tallpole.Thefourguysandthepolesplicearevisibleinthis

photograph.(Polarconsult,2011)


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6.0 SYSTEMECONOMICS

TheextremevarietyofenvironmentalandtechnicalconditionsfoundacrossruralAlaskaresultsinasignificantvariationinintertiecosts.Thetypicalcostforconstructingaconventionaloverheaddistribution‐classACintertieinruralAlaskacanvaryfromaslittleas$100,000permiletoover$600,000permile8inpartsofthestatewithchallenginglogisticsandlittleornotransportation.Intertiecostvariationsalsoaffectsubmarinecables,undergroundcables,andotheroverheadintertieconfigurations.ThedetailsofsystemeconomicsarepresentedinAppendixB.

6.1 COSTCOMPARISONOFACANDHVDCOVERHEADINTERTIES

TwodistinctoverheadHVDCintertieconfigurationshavebeencomparedtoaconventionalACintertietoillustratearangeofHVDCintertieeconomicswithdifferentoverheaddesigns.ThetwoHVDCintertieconfigurationsare:

● Atwo‐wiremonopolarHVDCintertieusingRUSstandardpracticeconstructionmethods.ThisintertieconfigurationrepresentstheupperrangeofestimatedcostforanHVDCoverheadintertieinruralAlaskaapplications.

● AmonopolarSWERHVDCintertieusingAlaska‐specificconstructionmethods.ThisintertieconfigurationrepresentsthelowerrangeofestimatedcostforanHVDCoverheadintertieinruralAlaskaapplications.

TheestimatedcostforHVDCintertiesinmostruralAlaskaapplicationsisexpectedtofallbetweenthecostscitedforthesetwoconfigurations.

6.1.1 InstallationCostComparison

Figure6‐1presentstheestimatedinstalledcostrelativetotheintertielengthforthreedifferentkindsofintertiesbuiltinruralAlaskaconditions:

● AconventionalruralAlaskaintertie,

● Atwo‐wiremonopolarHVDCintertieusingRUS‐typeconstructionmethods,and

● AmonopolarSWERHVDCintertieusingAlaska‐specificconstructionmethods.

Additionally,Figure6‐1illustratestheeconomicbreak‐evenlengthandrelativeincreaseinsavingsforlongerHVDCinterties.ThepointsatwhichtheAC“costline”crosseseitheroftheHVDC“costlines”representstheeconomicbreak‐evenlength.TheestimatedHVDCcostsshowahypotheticalrangeofinstalledcostsanticipatedforlow‐power(under1MW)ruralAlaskaHVDCsystems.

8SeeSectionB.6.1inAppendixBforcostbasisinformation.


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Figure 6-1 Comparative Installed Cost: Overhead 1-MW HVDC and AC Interties

$0

$5,000,000

$10,000,000

$15,000,000

$20,000,000

$25,000,000

$30,000,000

$35,000,000

$40,000,000

$45,000,000

0 10 20 30 40 50 60 70 80 90 100

Intertie Length (miles)

Probab

le In

stalled Cost of Overhead HVDC vs. AC In

terties

AC Intertie (Standard RUS Construction)

HVDC Intertie (Monopolar, TWMR, Standard RUS Construction)

HVDC Intertie (Monopolar, SWER, Alaska‐Specific Construction)

BREAK‐EVEN COST FOR HVDC INTERTIES: 6 to 22 MILES

(INSTALLED‐COST BASIS)

Note: This chart is based on the assumptions and comparative system costs

presented in Appendix B. The break‐even point will vary for every intertie project.

COST SAVINGS

RANGE

AC

HVDC

HVDC


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6.1.2 Life‐CycleCostComparison

Operatingcosts,maintenancecosts,andelectricalefficiencyaffectthelong‐termeconomicvalueofanintertie.Table6‐1presentscomparativelife‐cyclecostsforhypothetical25‐mile‐longoverheadACandHVDCintertiesinruralAlaska.Alengthof25mileswasselectedasitconservativelyrepresentsthesavingsanticipatedforshortHVDCinterties.Theestimatedlife‐cyclecostfora25‐mile‐longHVDCintertierangesfrom79%to107%ofthelife‐cyclecostofanACintertie.

Table 6-1 Estimated Life-Cycle Costs for 25-mile Overhead AC and HVDC Interties

ParameterStandardRUSACIntertie

MonopolarTwo‐WireHVDCIntertie(RUSConstruction2)

MonopolarSWERHVDCIntertie

(Alaska‐SpecificDesign1)

CostofDiesel($/gallon[gal]) $7.00pergallon

GenerationEfficiency(kWh/gal) 13kWhpergallon

IntertieEfficiency4 97.7% 93.4% 94.5%

NetAnnualEnergyTransmission(kWh) 1,664,400

AnnualTransmissionLosses4(kWh) 38,300 133,000 114,000

AnnualizedValueofTransmissionLosses($) $21,000 $71,000 $61,000

IntertieDesignLife(years) 20years

IntertieAnnualOperationsandMaintenance(O&M)Costs

$40,000 $58,000 $54,000

EffectiveDiscountRate 3%

PresentWorthofTransmissionLosses $307,000 $1,063,000 $912,000

PresentWorthofO&MCosts $595,000 $867,000 $796,000

ConverterStationsInstalledCost $20,000 $2,080,000 $1,160,000

IntertieInstalledCost $9,480,000 $7,120,000 $5,340,000

EstimatedLife‐CycleCost $10,402,000 $11,130,000 $8,208,000

HVDCLife‐CycleCostasPercentofACLife‐CycleCost 107% 79%

PresentWorthSavings(Cost)ofHVDCvs.AC ($728,000) $2,194,000

Notes:1. “Alaska‐SpecificDesign”referstothedesignconceptspresentedinAppendixCofthisreport.2. “RUSConstruction”referstostandardRUSdesignandconstructionmethodsforACinterties,adaptedtoHVDC

applicationsasdescribedinAppendixCofthisreport.3. Allmonetaryvaluesarein2012dollars.4. Efficiencyandlossinformationincludesalltransmissionsystemcomponents.


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Figure6‐2illustratestheeconomicbreak‐evenlengthandrelativeincreaseinsavingsforlongerHVDCinterties.ThepointsatwhichtheAC“costline”crosseseitheroftheHVDC“costlines”representstheeconomicbreak‐evenlength.TheestimatedHVDCcostsrepresentahypotheticalrangeoflife‐cyclecostsanticipatedforlow‐power(under1MW)ruralAlaskaHVDCsystems.

Figure 6-2 Comparative Life-Cycle Cost: Overhead 1-MW HVDC and AC Interties

$0

$5,000,000

$10,000,000

$15,000,000

$20,000,000

$25,000,000

$30,000,000

$35,000,000

$40,000,000

$45,000,000

0 10 20 30 40 50 60 70 80 90 100


Probab

le Life‐Cycle Cost of Overhead HVDC vs. AC In

terties





(LIFE CYCLE COST BASIS)



AC

HVDC

HVDC

COST SAVINGS

RANGE


MAY 2012 PAGE 41

6.2 CASESTUDIES

Thecasestudiesinthissectionprovideproject‐specificexamplesoftheexpectedcostsandresultingbenefitsofusingHVDCsystemstointerconnectcommunitiesandresources.Thesecasestudiesrelyonexistinginformationregardingtheproposedintertieroutes,loads,andrelatedprojectinformation.Figure6‐3presentsafewofthemanypotentiallow‐powerHVDCprojectsitesthroughoutAlaska.

Figure 6-3 Location Map for Potential HVDC Project Sites

Forthepurposesofthisreport,twospecificHVDCprojectsiteswereselectedforevaluation.The“GreensCreek–Hoonah”andthe“Nome–PilgrimHotSprings”intertieprojectsaretypicalofthedesignapproachandeconomicscommontootherHVDCAlaskaninterties.Table6‐2summarizesthecasestudiesconsideredinthissection.


MAY 2012 PAGE 42

Table 6-2 Summary of Case Studies

HVDCIntertieCaseStudy

TransmissionCircuit

IntertieType

HVDCIntertieCost

Estimate1

ACIntertieCost

Estimate1

EstimatedHVDCSavings1

PercentCapitalCost

Savings

GreensCreek–Hoonah

5‐MWmonopolarHVDCcircuitwithseareturn2

SubmarineCable

$22.2million

$49million

$26.8million 55%

Nome–PilgrimHotSprings

5MWbipolarHVDCcircuit

OverheadLine

$25.7million

$36.3million

$10.6million 29%

Notes:

1. Allcostestimatesarepresentedin2012dollars.

2. Thecasestudyprovidesasubmarineandoverheadintertiecapacityof5MWandconverterstationcapacityof2MW.ThisprovidesanamplemarginforloadgrowthinHoonah.Theconverterstationcapacitycanbeupgradedasneededin500‐kWincrementsupto5MW.

6.2.1 Green’sCreek–HoonahCaseStudy

AnintertiebetweenGreensCreek,ontheAlaskaElectricLightandPowerCompany(AEL&P)gridthatservesJuneau,andthevillageofHoonah,anisolatedmicro‐gridoperatedbytheIPEC,hasbeenunderconsiderationforoveradecade.AEL&PandtheIPEChavecompletedextensivestudiesanddesignworkonthisintertie.Studiesidentifieda25‐mile‐longACsubmarinecableandapproximately4milesofoverheadlinenearHoonahasthemosteconomicalmeanstocompletethisinterconnection.9TheproposedintertierouteisshownonFigure6‐4.

Asthedevelopmentofthisprojectcontinued,thecostsoftheACsubmarinecablehaveescalated,untiltheprojectwasfinallyputonholdduetoitsexcessivecost.Hoonahiscurrentlyexploringlocalhydropowerresourcestoreduceitsenergycostsbutcontinuestoviewanintertieasthebestlong‐termsolutionforitsenergyneeds.

ThisHVDCsystemrepresentsatechnologicaladvancethatcanreducethecostoftheGreensCreek–HoonahintertieandincreaseitseconomicfeasibilityascomparedwithHoonah’sotherenergyoptions.Thefollowingsubsectionsofthiscasestudyprovideahigh‐levelanalysisofthemeritsofanHVDCintertieforHoonah.

Forthepurposesofthiscasestudy,a5‐MWmonopolarHVDCtransmissioncircuitwithseareturnwasselectedtoconnectHoonahwithGreen’sCreek.Thiscircuitconsistsof25milesofsubmarinecableand4milesofoverheadline.Amonopolarcircuitwasselectedbecauseitisexpectedtobetheleast‐costintertiesolutionbetweenHoonahandGreen’sCreek.Otherpotentialconfigurations,suchasabipolarHVDCcircuitutilizingtwosingle‐conductorcables,wouldbemoreexpensivethanthemonopolardesignselected.

9(PowerEngineers,2004)


MAY 2012 PAGE 43

Theestimatedcapitalcostsincludea5‐MWtransmissioncircuit(submarinecableandoverheadline),and2‐MWconverterstationsatHoonahandGreen’sCreek.Theconverterstationscanbeupgradedto5MWbyadding500‐kWconvertermodulesasHoonah’sloadincreases.IfHoonah’sloadgrowsbeyond5MW,asecondsubmarinecablecanbeinstalledtoprovidea10‐MWbipolartransmissionsystem.

Figure 6-4 Greens Creek – Hoonah Intertie Route

6.2.1.1 EconomicAnalysis

Table6‐3presentstheeconomicanalysisfortheGreensCreek–Hoonahintertiealternatives.TheestimatedinstalledcostfortheHVDCintertieis$22.2million,ascomparedtothecostof$49millionforaconventionalACintertie.TheACintertiecostestimateisbasedonthe2009estimatedcostof$37.5million10adjustedto2012dollars.

10IPEC,2009.


MAY 2012 PAGE 44

Table 6-3 Estimated Cost for a Greens Creek – Hoonah HVDC Intertie

CostItem EstimatedCost

PreconstructionRight‐of‐wayacquisition,engineering,survey,permitting $1,600,000

Administration/Management $900,000

HVDCConverterStations(powerconverters,seaelectrodes,enclosures,ACandDCsidestationequipment) $2,700,000

SubmarineCableSupplyandInstallation $12,400,000

OverheadHVDCLine:SpaaskiBaytoHoonah $900,000

Contingency(onentireproject,25%)1 $3,700,000

TotalEstimatedCost $22,200,000

Notes:1.Acontingencyof25%isappliedtothecostsdevelopedforthisprojectbasedontheuncertaintiesassociatedwiththeproject.Asignificantamountofworkhasalreadybeendonetocharacterizethebathymetryandseafloorconditionsalongtheproposedcableroute.


MAY 2012 PAGE 45

Table6‐4presentsestimatedbenefit‐costratiosfortheGreensCreek–Hoonahintertieunderseveralloadgrowthscenarios.ThisanalysisindicatesacleareconomicadvantagetoanHVDCintertiebasedonreasonableloadgrowthforecastsforHoonah.

Table 6-4 Estimated Benefit-Cost Ratio of Greens Creek – Hoonah HVDC Intertie

ItemLoadGrowthScenario

ExistingLoad 165%Growth 200%Growth6

AnnualHoonahEnergyGeneration(kWh/yr)1 5,150,000 8,500,000 9,780,000

AEL&PAvoidedCostofEnergy(Juneau)2 $0.06perkWh

IPECAvoidedCostofEnergy(Hoonah)1 $0.20perkWh

IntertieOutageRate3 2%

AnnualHoonahSavings4 $707,000 $1,170,000 $1,340,000

IPECOperation,Maintenance,Repair,ReplacementandRehabilitation(OMR&R)AnnualCosts5 $90,000 $90,000 $100,000

NetAnnualSavings(Cost) $617,000 $1,150,000 $1,340,000

IntertieLifeandDiscountRate 30years,3%

PresentWorthofAnnualSavings(Costs) $12,070,000 $21,090,000 $24,500,000

EstimatedInstalledCost $22,200,000 $22,200,000 $22.200,000

EstimatedBenefit‐CostRatio 0.54 0.95 1.10

Notes:

1. BasedonPowerCostEqualization(PCE)reportsfor2007through2009(AEA,2010a).

2. ApproximateAEL&Penergycost.IPEChascapacity,sonodemandorcapacitychargesareincluded.

3. Assumedvalue.

4. AnnualsavingsarebasedonthedifferentialcostofenergyanddonotconsidereconomicbenefitsinHoonahfromlowercostenergy,oreffectstoAEL&Pofincreasedenergysales.

5. IPEC’sestimatedoperations,maintenance,repair,androutinereplacementcostsincludecostsfortheconverterstations,savingsfromdecreasedoperationandoverhaulofthedieselpowerplantinHoonah,andaone‐timecablerepaireventoverthe30‐yearanalysisperiod.

6. Hoonah’speakloadsundera200%loadgrowthscenariowouldexceedthe2‐MWcapacityoftheintertieconverterstations.Intertiethroughputisreducedby5%toreflectdieselgenerationinHoonah.


MAY 2012 PAGE 46

6.2.2 PilgrimHotSprings–Nome

PilgrimHotSpringsisageothermalresourcelocatedapproximately60milesnorthofNome.IthasbeenproposedasapowersourcetoreduceNome’srelianceondieselfuelforelectricalgeneration.ACEPiscurrentlystudyingthePilgrimHotSpringsgeothermalresourcetobettercharacterizetheresource’spotentialforpowergenerationandotherapplications.ForpurposesofsizingthetransmissionlinefromPilgrimHotSprings,anelectricalgeneratingcapacityandtransmissioncapacityof5MWisassumed,basedonconversationswithACEP’smanagerforthePilgrimHotSpringsassessmentproject.11TheproposedtransmissionrouteisshownonFigure6‐5.

AbipolarHVDCcircuitusingoverheadlineswasselectedfortheHVDCintertie.Thebipolarconfigurationwasselectedbecauseitprovidesincreasedreliabilitycomparedtoamonopolarlineatareasonableadditionalcost.

ConceptualpowerlinecostsforoverheadACandHVDCintertieswereestimatedtoevaluatethebenefitsofconnectingPilgrimHotSpringstoNomeusinganHVDCintertie.ThecostestimatesindicatethatanHVDCtransmissionlinewouldcost29%lessthananACtransmissionline.

Aroutingstudywasnotperformedaspartofthiscasestudy.Powerlineswereroutedalongtheexistingroadcorridor.Thisisassumedtobetheleast‐costrouteforthepowerlines,astheroadcanbeusedtosupporttheconstructionandlong‐termmaintenanceoftheline.Aroutingstudymayidentifyotherroutesthataremorefavorableduetogeotechnical,landstatus,environmental,orotherfactors.

11PersonalcommunicationwithMarcusMager,2012.


MAY 2012 PAGE 47

Figure 6-5 Prospective Transmission Route from Pilgrim Hot Springs to Nome


MAY 2012 PAGE 48

6.2.2.1 EconomicAnalysis

Table6‐5presentstheeconomicanalysisforthePilgrimHotSprings–Nomeintertiealternatives.TheestimatedinstalledcostfortheHVDCintertiealternativeis$25.7million,ascomparedtothecostof$36.3millionforaconventionalACintertie.

NoinformationisavailablefortheinstalledcostofageothermalpowerplantatPilgrimHotSpringsorthecostoftheenergyitwouldgenerate,soabenefit‐costratiooftheintertiealternativeswasnotevaluated.

Table 6-5 Estimated Installed Cost for a 5-MW Pilgrim Hot Springs – Nome Intertie

CostItem

EstimatedInstalledCostforBipolarHVDC

Intertie

EstimatedInstalledCostforACIntertie

EstimatedHVDCSavings

PercentCostSavings

PreconstructionActivities(right‐of‐wayacquisition,design,survey,permitting)

$3,400,000 $3,400,000 ‐ ‐

Administration/Management $1,000,000 $1,300,000 ‐ ‐

ConverterStationConstruction $4,600,000 $3,000,000 ‐ ‐

OverheadIntertieConstruction $10,800,000 $20,200,000 ‐ ‐

Contingency(30%)1 $5,900,000 $8,400,000 ‐ ‐

TotalEstimatedCost $25,700,000 $36,300,000 $10,600,000 29%

Note:1. A30%contingencywasappliedtothecostsforthisprojectbecausenoinformationwasavailableforthe

transmissionroute.Thislackofdatacreatesrisksduetofactorssuchaslandavailability,geotechnicalconditions,structural(windandice)loadings,andenvironmental(bird,wildlife,andaesthetics)factors.Someoftheserisksaremitigatedbytheuseofcostdatafortherobustconceptualdesigns(i.e.,Alaska‐specificconstruction)usedfortheHVDCsystem.TheAlaska‐specificconceptualdesignisassumedtobeadequatefortheexpectedgeotechnicalandstructuralconditionsalongtheroute.Environmentalandlandavailabilityissues,whichcouldrequirealongerrouteordeparturefromtheroadcorridor,poserelativelygreaterrisksthanlinedesignconsiderations.Thenetresultofthesefactorsresultsinthe30%contingencyusedforthecasestudyeconomics.


MAY 2012 PAGE 49

7.0 CONCLUSIONSANDRECOMMENDATIONS

7.1 CONCLUSIONS

PhaseIIhasdemonstratedthattheconvertertechnologyistechnicallyviableandthetransmissionsystemiseconomicallyfeasible.KeyPhaseIIfindingsare:

● Low‐powerHVDCconvertertechnologyisexpectedtobecommerciallyavailableat$250perkilowattperconverter.

● Estimatesofconstructioncostsforaconceptual25‐mileoverheadHVDCintertieindicatecapitalcostsavingsofapproximately30%comparedwithaconventionaloverheadACintertie.Estimatedlife‐cyclecostsrangefrom79%to107%ofthelife‐cyclecostofanACintertie.

● LongeroverheadHVDCintertiescanexpectcapitalcostsavingsofupto40%.

● SignificantsavingsarepossibleforsubmarinecableandundergroundcableapplicationsusingHVDCsystems.Estimatedcapitalcostsavingsona25‐milelow‐powerHVDCsubmarinecableintertieareover50%comparedtoACalternatives.

BasedonPhaseIIfindings,thebenefitsoflow‐powerHVDCsystemsforAlaskaaresubstantial,andcontinueddevelopmentofthissystemisrecommended.

7.2 OPPORTUNITIESANDBARRIERS

BasedonanalysisandstudyconductedduringthisPhaseIIproject,PolarconsulthasconcludedthatthisHVDCtechnologypresentsthefollowingopportunitiesforAlaska’sutilityindustryandruralcommunities:

● Lessexpensiveruralelectricinterties,leadingtolower‐costenergyandincreasedenergyindependenceforruralcommunities.

● Interconnectiontocurrentlystrandedenergyresources.

● Interconnectioncostsavingsbycombiningruralelectricandtelecommunicationsinterties.

Thesuccessfulcommercializationandadoptionoflow‐powerHVDCtechnologyinAlaskarequiresovercomingthefollowingbarriers:

● Completionofthecommercialdevelopmentanddemonstrationoftheconvertertechnology.Continueddevelopmentoftheprototypeconverters,culminatinginindependenttestingoftheconvertersanddeploymentonanAlaskautilitysystem,isneededtoprovethattheconvertersareacommerciallyviabletechnology.

● Acceptanceanduseoflow‐powerHVDCtechnologybyAlaska’sutilityindustry.Continuedinvolvementofin‐stateandinternationalstakeholderswiththeon‐goingdevelopmentofthistechnologyisconsiderednecessarytosurmountingthisbarrier.

● DevelopmentanddemonstrationofstandardsandcontrolprotocolsforMTDCtransmissionnetworks,whichareneededtobuildcost‐effectiveregionalHVDCpowernetworksinruralAlaska.


MAY 2012 PAGE 50

7.3 RECOMMENDATIONS

Basedontheconclusionsandfindingsofthisproject,thefollowingactionsarerecommended.

PhaseIIIprogramactivities:

● Continueddevelopmentofthepowerconvertertechnologytocommercializetheexistingprototypeconverterdesign.SolicitationofadditionalHVDCconvertermanufacturersiswarrantedtoencouragediversityofsuppliersandcompetition;

● Independenttestingoftheconverterstovalidateefficiencyandperformance,followedbydeploymentonanAlaskanutilitysystemtovalidatefunctionalityandreliabilityinacommercialsetting;

● FurtherdevelopmentofMTDCtransmissionsystemsinterconnectionandcontroltechnologies;and

● Continuedinvolvementofin‐statestakeholdersinthedevelopmentofthistechnology.

Stakeholderactions:

● Incorporatelow‐powerHVDCtechnologyintoAlaska’sregionalandstatewideenergyplansandpolicies;

● ContinuecoordinationwiththeStateofAlaskatoallowaproject‐specificwaiveroftheNESCtoallowtheuseofSWERcircuits;

● EncourageplannedruralpowerandtelecommunicationsintertiestoincorporateHVDCtechnologyintheireconomicandtechnicalanalysis,aswellastheirenvironmentalandpermittingreviewprocesses;

● Engagethetelecommunicationsindustrytoraiseawarenessofthesynergiespossiblebetweenlow‐powerHVDCtransmissionandfibernetworksinruralAlaska;and

● Collaboratewithinternationalstakeholderstoidentifysynergiesandlessonslearnedfromparalleltechnologydevelopmentefforts.Coordinateondevelopmentofapplicablepolicies/standardsandidentificationofmarketstohelpexpeditethecommercializationandreducethecostsoflow‐powerHVDCsystems.


MAY 2012 PAGE A-1

APPENDIXA

HVDCOVERVIEW


MAY 2012 PAGE A-2

Thispageintentionallyblank.


MAY 2012 PAGE A-3

TABLEOFCONTENTS

A.1 HIGH‐VOLTAGEDIRECTCURRENT(HVDC)TECHNOLOGY..................................................................5

A.2 SINGLE‐WIREEARTHRETURN(SWER)CIRCUITS...................................................................................7 A.2.1 WHYUSESWER?.............................................................................................................................................................7

A.3 SWERINALASKA.....................................................................................................................................................8 A.3.1 BETHEL–NAPAKIAKACSWERLINE..........................................................................................................................8 A.3.2 KOBUK–SHUNGNAKACSWERLINE..........................................................................................................................8 A.3.3 FUTUREOFSWERINALASKA........................................................................................................................................8

A.4 HVDCFORALASKA.................................................................................................................................................9


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MAY 2012 PAGE A-5

A.1 HIGH‐VOLTAGEDIRECTCURRENT(HVDC)TECHNOLOGY

High‐voltagedirectcurrent(HVDC)convertertechnologyhasadvancedtousehigh‐efficiencysolid‐statehardware,andHVDClinksareutilizedforelectricaltransmissionthroughouttheworld.Whilethetechnologyhasadvancedconsiderablysincethe1950s,utilityapplicationofHVDCremainslimitedtotransmissionfunctions.Thesmallestutility‐gradeHVDCsystemsaredesignedtotransmitapproximately50megawatts(MW)12.SomenotableHVDCinstallationsinclude:

● SwedishMainlandtoGotlandIsland:20MW,100kilovolt(kV),monopolarsubmarinecablewithseareturn.Commissionedin1956,thiswasoneofthefirstHVDCintertiesinstalledintheworld.Thisoriginalsystemwasdecommissionedin198713.

● PacificIntertie–Celilo,Oregon,toSylmar,California:846‐mile,3,100MW,500kV,bipolaroverheadline.Commissionedin1970.

● BritishColumbiaMainlandtoVancouverIsland,Canada:45‐mile,682MW,260‐280kV,bipolarsubmarineandoverheadsystem.Thefirstpolewascommissionedin1968,andasecondpolewascommissionedin197714.

● NelsonRiverBipolarSystem,NelsonRiverHydroComplextoSouthernManitoba,Canada:TwobipolartransmissionsystemsoperatebetweenthehydropowerprojectsalongtheNelsonRiverinnorthernManitobaandWinnipeginthesouthernpartoftheprovince.Thefirstsystemisa540‐mile,1,620MW,450kVoverheadbipolarcircuitcommissionedin1977.Thesecondisa560‐mile,1,800MW,500kVoverheadbipolarcircuitcommissionedinstagesbetween1978and1985.Notably,bothsystemstraversepermafrostterrainsimilartothatfoundinAlaskaandcanoperateinSWERmode,moving1,000sofamperesofcurrentthroughearth‐return15.

● Cross‐SoundCable,NewHaven,Connecticut,toLongIsland,NewYork:24‐mile,330MW,150kVbipolarsubmarinecable.Commissionedin2002,thiscableusesABB'sHVDCLitetechnology.BothHVDCconductorsandafiber‐optictelecommunicationscablearebundledintoasinglecabletosimplifyinstallation16.

● England–FranceCrossChannelIntertie:38‐mile,160MW,100kVbipolarsubmarinecable.Theoriginalsystemwascommissionedin1961andreplacedin1986byalargersystemoperatingat270kVand2,000MW.Abipolarsystemwasoriginallyinstalledtoreducemagneticanomaliesthatcouldinterferewithshipping.

● Sardinia–Corsica–ItalianMainland,Italy:500MW,200kVbothearthandseareturns.Thefirst200MWpoleofthissystemwascommissionedin1965.Asecond300MWpolewasinstalledin1992.Thissystemisunusualbecauseitisamultipointsystem(servingthreeloadcenters),unlikemostHVDCinterties,whichtransmitpowerbetweenonlytwopoints.

12“HVDCLite,”distributedbyABB,isoneexampleofthesmallerutility‐gradeHVDCsystems.13 Theoriginalsystemusedon‐shoregroundinggridstocompletethetransmissioncircuitviaseaand/orseabedpathways.This

firstHVDClinkwasaugmentedbyasecond150MWmonopolarHVDClinktotheislandin1983,andathird150MWmonopolarlinkin1987.Today,thesetwonewercircuitsareoperatedtogetherasabipolartransmissionlink.

14 Thefirstmonopolarlineisratedfor312MWat260kV,andthesecondmonopolarlineisratedat370MWat280kV.15 http://www.hydro.mb.ca/corporate/facilities/ts_nelson.shtml16 CrossSoundCableConnectorProjectLiterature,www.abb.com


MAY 2012 PAGE A-6

● Fiveback‐to‐backHVDCconverterstations17interconnecttheTexasgridandU.S.electricgridinneighboringstates.Mostofthesestationswerecommissionedinthe1980s.Becauseofthesestations,TexashasanasynchronousgridconnectiontotheremainderoftheLower48.

● ThreeGorgesDamtoShanghai,China:530‐mile,3,000MW,500kV,bipolaroverheadline.FourHVDClinesareplannedbetweenThreeGorgesandChina'seasterncoastalregions.Thefirstbipolarcircuitwascommissionedin2003andthesecondin2006.

● VictoriatoTasmania,Australia:500MW,400kV,monopolarsubmarinecablewithseareturn.Commissionedin2005.

● SwedentoGermany,BalticCable:600MW,450kV,withearthreturnviadeepholeelectrodes.Commissionedin1993.

HVDClinkscanbesuperiortohigh‐voltagealternatingcurrent(AC)linksforseveralkeyreasons:

● HVDClinksarelesscostlyand/ormoreefficientthanAClinksundercertaincircumstances.

● Longintertiesutilizinginsulatedcables(asforsubmarineapplications)arepossiblewithHVDCelectricity,butprohibitivelydifficultwithACelectricityduetocablecapacitanceandreactivepowerlosses.

● HVDClinksprovideanasynchronousconnectionbetweenACelectricalgrids.Analogoustoaclutchonamechanicalsystem,anHVDCintertieallowseachACsystemtooperateatitsownphaseandfrequencyandstillallowpowertransferbetweenthesystems.ThiscanincreasethestabilityofbothACgrids.

● Foragivenpowertransferrequirement,HVDCintertiescanrequirelessright‐of‐waythancomparableACinterties.Theycanalsohaveavarietyofotherregulatory,permitting,orenvironmentaladvantagescomparedtoACinterties.

BecauseofthehighcostoftheconvertersystemsnecessarytoconvertHVDCtoamorereadilyusedACwaveform,HVDCisgenerallylimitedtotransmissionapplications.Accordingly,mostorallutilityHVDCsystemsinusetodayarepoint‐to‐pointtransmissionlines,withnointermediatetake‐offpointsorsubstationsforcommunitiesenroute.

Forthesmall‐scaleruralAlaskaHVDCapplicationsconsideredinthisstudy,thereisstillaneconomicbarrierduetothecostoftheHVDCconverters(estimatedat$250,000perMWin2012dollars).Forexample,aremotelodgeorfishcamplikelycannotjustifythecosttotaptheHVDCline,butmostvillagescan.

AsHVDCintertiesareconsideredforruralAlaskaapplications,utilitiesmaydesiretoextendACdistributionasanunderbuildoroverbuildonanoverheadHVDCline.Similarly,otherutilitiesmaydesiretoutilizetheoverheadstructurestoco‐locatetheircables.Thispracticeispossiblesolongasapplicablecoderequirementsandsafetyprovisionsarefollowed.Itmaybedesirabletouseconventionalconstructionintheimmediatevicinityofvillagestofacilitatecolocationofmultipleutilitycables,transitioningtoadifferent,optimizedoverheadstructureforHVDConceawayfromthevillage.

17 ThefiveHVDCsystemsarethe220‐MWback‐to‐backNorthDCTie,600‐MWback‐to‐backEastDCTie,36MVAback‐to‐back

EGPSDCTie,150MVAback‐to‐backRAILDCTie,and80MVALaredovariablefrequencytransformer(VFT)Tie.(www.ercot.com).


MAY 2012 PAGE A-7

A.2 SINGLE‐WIREEARTHRETURN(SWER)CIRCUITS

Initssimplestform,anelectricalcircuitrequirestwocurrentpathways,typicallywires.Onewiregoesfromthepowersupplytotheload,andasecondwiregoesfromtheloadbacktothepowersupply.Bothsingle‐phaseACandDCcircuitsrelyonthisbasicconfiguration.Thewirefromthepowersupplytotheloadisusuallyatanincreasedvoltagerelativetoground,andsoitisinsulatedforsafetyandtopreventshortcircuits.Thewirefromtheloadbacktothepowersupplyisusuallyatamuchlowervoltagerelativetogroundandthusisusuallybutnotalwaysinsulated.

Insingle‐wireearthreturn(SWER)circuits,thewirethatservesasthesecondcurrentpathwayfromtheloadbacktothepowersupplyisreplacedwithasuitable,convenient,andsafecurrentpathway.Inthemostgeneralcase,this“non‐wire”pathwaycanbeacarortruckchassis,themetalhandleofaflashlight,theearth,naturalwaterbodies,orotherobjectsthatcansafelycompletetheelectricalcircuit.

Seareturncircuitsaresimilartoearthreturncircuits.Theonlydifferenceisthatthesea,oranywaterbody,isusedasthepredominantreturncircuitpathway.Parallelpathways,suchastheseabed,arealsoavailableforcurrentflow.

A.2.1 WhyUseSWER?

TheprimaryadvantagesofferedbySWERcircuitsinclude:

● Lowercosts(eliminatethesecondconductor).

● Higherefficiency(lowerelectricallosses).

TheprimaryconcernsassociatedwithSWERcircuitsinclude:

● AvoidingcorrosionofburiedorsubmarinemetallicobjectsinthevicinityoftheSWERcircuit.

● Aswithallelectricalsystems,safety.

SWERcircuitsarewidelyusedforutilitytransmissionanddistributionofelectricityallovertheworld.NumerousHVDCintertiesareSWERcircuits,consistingofasinglehigh‐voltagecableandanearthorseareturntocompletethetransmissioncircuit.ManyoftheseareinstalledinclimatesandconditionssimilartoAlaska,notablyinScandinavia.Inmanynations,single‐phaseACSWERcircuitsareacceptedpracticeandareindustrystandardforservingruralareas.

NationsandjurisdictionsthatuseSWERACcircuitstoservetheirruralareaseconomicallyincludethefollowing18,19.

● Australia(over100,000milesinservice)

● Cambodia(Electricite’duCambodge)

● NewZealand

● Vietnam

● Laos(Electricite’duLaos)

● SouthAfrica(EskonDistribution)

18 “SingleWireEarthReturnforRemoteRuralDistribution,ReducingCostandImprovingReliability.”ConradW.Holland.

MaunsellLtd.,AnAECOMCompany.19 “SingleWirePowerinAlaska.”StateofAlaska,DivisionofEnergyandPowerDevelopment.R.W.RutherfordAssociates.1982.


MAY 2012 PAGE A-8

● Saskatchewan

● India

● Brazil

A.3 SWERINALASKA

Atleasttwosingle‐phaseACSWERcircuitshavebeensuccessfullybuiltandoperatedinAlaska.TheseACSWERcircuitsdemonstratethatSWERisaproven,beneficial,andappropriatetechnologyforruralAlaskatransmissionapplications.

A.3.1 Bethel–NapakiakACSWERLine

In1981,a10.5‐mile14.4kVsingle‐phaseACSWERlinewasconstructedtoconnectthesmallvillageofNapakiaktotheCityofBethel.Thislineusedbipodstructurestosuspenda7#8Alumoweldconductor.

Thislinewasconstructedatacostof$23,000permile(1980$)andoperatedsuccessfullyformanyyears.Arguably,thelinehadtwoshortcomings,neitherrelatedtoitsSWERoperation:(1)thestructuraldesignofthelinereliedupontheconductortoprovidelongitudinalsupporttothebipodpolesbetweendeadends,andonatleastoneoccasionaconductorbreakcausedaseriesofstructurestofalldown;and(2)overtime,theloadinNapakiakexceededtheline'scapacity.However,thelinewasanunqualifiedsuccessatdemonstratingthatSWERcanreducethecostsofpowertransmissioninruralAlaska.

Commonmisperceptionsaboutthislinehavegivenitanegativereputation,whichisoftenincorrectlyattributedtoits“innovative”SWERdesign.Thelinedidsufferhighlosses,butthesecanbeattributedtounmeteredloadsinNapakiakandthepoorconditionofthedistributionsysteminNapakiak.

TheAlaskaEnergyAuthorityreplacedtheBethel‐Napakiaklinewithaconventionalthree‐phaselinein2010.Theinstalledcostofthisreplacementwasapproximately$344,000permilein2012dollars,approximatelythreetimesgreaterthantheinflation‐adjustedcostoftheoriginalline20.

A.3.2 Kobuk–ShungnakACSWERLine

A10‐milesingle‐phaseACSWERlinewasconstructedtoconnectthevillageofShungnaktoKobukinnorthwesternAlaska.ThelineandtheSWERsystemworkedsuccessfully;however,thesupportstructureswereconstructedoflocalsprucetrees,andeventuallythebasesrotted.LiketheBethel–NapakiakSWERline,thislinealsosuccessfullydemonstratedSWERviabilityinpermafrostregions.In1991,this10‐milelinewasreplacedwithaconventionalthree‐phase7.2/12.4kVAClinewithpolesattachedtodrivensteelH‐pilesatacostof$1.1million,orabout$110,000permilein1991dollars21.

A.3.3 FutureofSWERinAlaska

ThetransitionofmostAlaskavillagestothree‐phasedistributionsystemshasdiminishedthevalueofsingle‐phaseACSWERinterties.ACphaseconverterswouldbenecessarytointerfacetheintertiewithoneorbothvillagegrids.Inaddition,thenationalelectricalcodesadoptedbytheStateofAlaskadonotallowtheuseofSWERcircuitsforroutinepowertransmissionordistribution.Perhapsbecauseofthesefactors,thereiscurrentlyagenerallackofinterestinSWERtechnologyinAlaska.

20 (AEA,2007);(DC,2010).21 Petrie,Brent.AlaskaVillageElectricCooperative,Inc.PersonalCommunication.February2008.


MAY 2012 PAGE A-9

Despitesuchfactors,SWERcircuitsremainaprovenandcost‐effectiveoptionforruralAlaskaapplications,andtheywarrantseriousconsideration.CoupledwithHVDC,SWERofferscostandtechnicaladvantagesthathavethepotentialtorevolutionizeruralpowertransmissioninAlaska.

AffordableenergyisavitalunderpinningofcreatingasustainableeconomicbaseforAlaska'sruralareas.Affordabletransmissioniskeytoachievingaffordableenergy,andthecouplingofSWERandHVDCpresentsthebrightestopportunityforachievingaffordabletransmissioninAlaska.Accordingly,thefutureofSWERinAlaskaisverypromising.

A.4 HVDCFORALASKA

ThelistofexistingHVDCprojectsinSectionA.2illustratesthefactthattoday'scommercialHVDCtechnologyremainslimitedtolarge‐scaletransferofelectricity,normallymeasuredinthe100sor1,000sofmegawatts.SuchtechnologyhasverylimitedapplicationinAlaska,asourlargestutilitygrid,alongtherailbelt,hasapeakloadofwellunder1,000MW.Mostruralloadsaremeasuredinthe100sofkW.

ThelackofcommercialHVDCtechnologyinthekilowattclassnecessaryforruralAlaskaapplicationsmeansthatthenumerousbenefitsofferedbyHVDCtransmissionarenotpresentlyavailabletoAlaska'sruralcommunities.ThekeyobjectiveandimpetusforthisprojectistolowerthecostofruralAlaskaintertiesbyextendingthereachofcommerciallyavailableHVDCtechnologydowntothekilowattclassneededtoserveAlaska'sruralenergytransmissionneeds.

TheapplicationsforthistechnologyinAlaskaarenumerousandinclude:

● ConnectingBethelandnearbyvillageswithawindfarmalongtheBeringSeacoast.

● ConnectingvillagesalongtheYukonRiversuchasKoyukuk,Nulato,Ruby,andKaltagwiththeproposedToshibanuclearbatteryinGalena.

● Connecting25southwesterncommunitiestoaproposed25‐MWgeothermalplantnearKingSalmon.

● ConnectingNorthSlopecommunitiessuchasAtqusukwithBarrowtoshareinthelow‐costelectricityderivedfromBarrow’sgasfields.

● DevelopingthegeothermalresourceatPilgrimHotSpringsandtransmitthepowertoNomeviaHVDCintertie.

● CompletingconnectionsintheSoutheastIntertieviaanaffordableHVDCsubmarinecable.

A.3.9 DesignConsiderationsforSmallAlaskaHVDCInterties

ManyofthetechnicalaspectsofdesigningandbuildingsmallHVDCintertiesinAlaskaaremuchthesameasforbuildingintertiesanywhere.ThesingledominatingfactorthatsetsconstructioninruralAlaskaapartislogistics.Mostprojectshavelittleornosupportinfrastructure,rangingfromthebasicssuchasmodernlodgingforworkerstoavailabilityoftransportationinfrastructure,heavyequipment,skilledlabor,andsoon.

ManymajorconstructionprojectsaddressthelogisticalchallengesofruralAlaskabyimportingeverythingnecessarytogetthejobdonebyconventionalmeans.Thisworks,butisverycostly.

Adifferentsolutiontothelogisticschallengeistotailorthedesigntouseavailablelocalresourcestotheextentpossible.Thisisaverychallengingproposition,buttherewards–lowerconstructioncosts–aresubstantial.Ingeneralterms,designingforAlaskalogisticsmeans:


MAY 2012 PAGE A-10

● Usematerialsandequipmentthatarereadilyshippedbycommontransportationmethods,suchassmallcargoaircraft22.Usematerialsandconstructionmethodsthatcanutilizesmall,lowgroundpressureequipmenttoenableconstructionduringsummerorautumnthawedconditions.

● Usematerialsandconstructionmethodsthatemploylocallyavailableequipmentfortransportandconstructionasmuchaspossible.

● Reducetheamountofconstructionandfabricationrequiredinthefieldandontheline.Pre‐manufactureandpreassemblebeforeshippingtothevillagesorinthevillagesbeforeshippingtothefieldtoreducecostsandincreasequality.

● Optimizetheconstructionandassemblymethodstoemploylocallyavailablelabor.

22 ThelargestcargoaircraftsuitableforAlaskalogisticplanningisaHerculesC‐130,butmanyvillageairstripscannot

accommodateaHercules.AmoreuniversalcargoaircraftforremoteAlaskaprojectsisaSherpaSD‐330orsimilarsmallcargoaircraft.


MAY 2012 PAGE B-1

APPENDIXB

ECONOMICANALYSIS


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MAY 2012 PAGE B-3

TABLEOFCONTENTS

B.1 INTRODUCTION........................................................................................................................................................7

B.2 ECONOMICANALYSIS............................................................................................................................................8 B.2.1 COMPARATIVECOST:ACVERSUSHVDCOVERHEADINTERTIES.............................................................................8 B.2.2 INSTALLATIONCOSTCOMPARISON................................................................................................................................8 B.2.3 LIFE‐CYCLECOSTCOMPARISON...................................................................................................................................10

B.3 COSTANALYSISBASIS.........................................................................................................................................12 B.3.1 GENERATIONANDLOADASSUMPTIONS......................................................................................................................12 B.3.2 SYSTEMEFFICIENCYASSUMPTIONS.............................................................................................................................12 B.3.3 OPERATION,MAINTENANCE,ANDREPAIRASSUMPTIONS.......................................................................................12 B.3.4 ECONOMICASSUMPTIONS..............................................................................................................................................13 B.3.5 INSTALLEDCOSTASSUMPTIONS...................................................................................................................................13

B.4 CASESTUDIES.........................................................................................................................................................14 B.4.1 GREEN’SCREEK–HOONAHCASESTUDY....................................................................................................................14 B.4.2 PILGRIMHOTSPRINGS–NOME....................................................................................................................................19

B.5 DETAILEDHVDCINTERTIECOSTINFORMATION..................................................................................23 B.5.1 OVERHEADINTERTIECOSTDETAIL.............................................................................................................................23 B.5.2 SUBMARINECABLEINTERTIECOSTDETAIL...............................................................................................................25 B.5.3 UNDERGROUNDCABLEINTERTIECOSTDETAIL........................................................................................................25 B.5.4 CONVERTERSTATIONCOSTDETAIL............................................................................................................................26

B.6 DETAILEDACINTERTIECOSTINFORMATION........................................................................................30 B.6.1 COSTBASELINESFOROVERHEADACINTERTIES......................................................................................................31 B.6.2 COSTBASELINEFORSUBMARINECABLEACINTERTIES..........................................................................................33


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MAY 2012 PAGE B-5

LISTOFTABLES

TableB‐1 EstimatedLife‐CycleCostsfor25‐mileOverheadACandHVDCInterties.......................10

TableB‐2 SummaryofCaseStudies......................................................................................................................14

TableB‐3 EstimatedCostforanGreensCreek–HoonahHVDCIntertie...............................................17

TableB‐4 EstimatedBenefit‐CostRatioofGreensCreek–HoonahHVDCIntertie..........................18

TableB‐5 EstimatedInstalledCostfora5‐MWPilgrimHotSprings–NomeIntertie.....................22

TableB‐6 EstimatedCostfora25‐mileOverheadHVDCIntertie............................................................24

TableB‐7 EstimatedCostsfora25‐mileUndergroundHVDCIntertie..................................................26

TableB‐8 1‐MWHVDCConverterStationCostEstimate.............................................................................27

TableB‐9 HVDCConverterEnclosureCostDetail...........................................................................................27

TableB‐10 SwitchgearandSwitchyardCostDetail..........................................................................................28

TableB‐11 HVDCGroundingStationCostDetail................................................................................................29

TableB‐12 CostBaselinesforRemoteAlaskaACIntertieConstruction..................................................30

TableB‐13 EstimatedCostsforOverheadACInterties...................................................................................31

TableB‐14 InstalledCostsofRecentRemoteAlaskaOverheadACInterties.........................................32

TableB‐15 InstalledCostsofRecentRemoteAlaskaSubmarineCableInterties.................................33


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LISTOFFIGURES

FigureB‐1 ComparativeInstalledCost:Overhead1‐MWHVDCandACInterties.................................9

FigureB‐2 ComparativeLife‐CycleCost:Overhead1‐MWHVDCandACInterties............................11

FigureB‐3 GreensCreek–HoonahIntertieRoute............................................................................................15

FigureB‐4 ProspectiveTransmissionRoutefromPilgrimHotSpringstoNome................................20


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B.1 INTRODUCTION

TheextremevarietyofenvironmentalandtechnicalconditionsfoundacrossruralAlaskaresultsinasignificantvariationinintertiecosts.Thetypicalcostforconstructingaconventionaloverheaddistribution‐classalternatingcurrent(AC)intertieinruralAlaskacanvaryfromaslittleas$100,000permileinareaswithgoodlogisticsupportgeotechnicalconditionsandtransportationinfrastructure(roadsystem,southeast)toover$600,000permile23inpartsofthestatewithchallenginglogisticsandlittleornotransportationinfrastructure(remoteinterior,northwest,orYukon‐Kuskokwimdeltaregions).

Intertiecostvariationsalsoaffectsubmarinecables,undergroundcables,andotheroverheadintertieconfigurations.

Thisappendixprovidesthefollowingeconomicanalyses:

● ComparativepresentworthanalysisofconceptualACandhigh‐voltagedirectcurrent(HVDC)interties;

● CasestudiesofAlaskaHVDCinterties;

● EstimatedcostsforconceptualHVDCinterties;and

● BaselinecostsforruralAlaskaACinterties.

23SeeSectionB.6.1forinformationonthecostbasisofruralAlaskaACinterties.


MAY 2012 PAGE B-8

B.2 ECONOMICANALYSIS

ThissectionevaluatescomparativecostsforconceptualACandHVDCinterties.BecauseHVDCintertiesincurtheaddedexpenseofconverterstations,shortHVDCinterties(underapproximately6to31miles)willgenerallynotbecost‐effectivecomparedwithACinterties,dependingonproject‐specificconditions.

Astheintertielengthincreases,thelowerper‐milecostofthetransmissionlineoffsetstheadditionalcostofthepowerconverters.HVDCintertiesshorterthanacertaineconomic“break‐even”lengthwillbemorecostlythanacomparableACintertie.TherelativesavingspossiblewithanHVDCtransmissionsystemincreasesforintertielengthsabovethisbreak‐evenlength.

Basedonspecificprojectconditions,andontheassumptionsandanalysisdescribedherein,theconceptualbreak‐evenlengthforoverheadintertiesisapproximately6to22milesonaninstalled‐costbasis,and12to31milesonalife‐cyclecostbasis.Theconditionsandassumptionsusedtodeveloptheseeconomicbreak‐evenlengthestimatesareprovidedinthisappendix.

B.2.1 ComparativeCost:ACversusHVDCOverheadInterties

TwodistinctHVDCintertieconfigurationshavebeencomparedtoaconventionalACintertietoillustratethedifferenceinprojecteconomics.ThetwoHVDCintertieconfigurationsare:

● Atwo‐wiremonopolarHVDCintertieusingU.S.DepartmentofAgriculture(USDA)RuralUtilitiesService(RUS)‐typeconstructionmethods.ThisintertieconfigurationrepresentstheupperrangeofestimatedcostforanHVDCoverheadintertieinruralAlaskaapplications.

● Amonopolarsingle‐wireearthreturn(SWER)HVDCintertieusingAlaska‐specificconstructionmethods.ThisintertieconfigurationrepresentsthelowerrangeofestimatedcostforanHVDCoverheadintertieinruralAlaskaapplications.

ThecostforHVDCintertiesinmostruralAlaskaapplicationsareexpectedtofallbetweenthecostestimatescitedforthesetwoconfigurations.

B.2.2 InstallationCostComparison

FigureB‐1presentstheestimatedinstalledcostrelativetotheintertielengthforthreedifferentkindsofoverheadintertiesbuiltinruralAlaskaconditions:

● AconventionalruralAlaskaintertie,

● Atwo‐wiremonopolarHVDCintertieusingRUS‐typeconstructionmethods,and

● AmonopolarSWERHVDCintertieusingAlaska‐specificconstructionmethods.


MAY 2012 PAGE B-9

Inaddition,FigureB‐1illustratestheeconomicbreak‐evenlength,andrelativeincreaseinsavingsforlongerHVDCinterties.ThepointsatwhichtheAC“costline”crosseseitheroftheHVDC“costlines”representstheeconomicbreak‐evenlength.TheestimatedHVDCcostsrepresentahypotheticalrangeofinstalledcostsanticipatedforlow‐power(under1megawatt[MW])ruralAlaskaHVDCsystems.

Figure B-1 Comparative Installed Cost: Overhead 1-MW HVDC and AC Interties

$0

$5,000,000

$10,000,000

$15,000,000

$20,000,000

$25,000,000

$30,000,000

$35,000,000

$40,000,000

$45,000,000

0 10 20 30 40 50 60 70 80 90 100


Probab

le In

stalled Cost of Overhead HVDC vs. AC In

terties





(INSTALLED‐COST BASIS)



COST SAVINGS

RANGE

AC

HVDC

HVDC


MAY 2012 PAGE B-10

B.2.3 Life‐CycleCostComparison

Operatingcosts,maintenancecosts,andefficiencyaffectthelong‐termeconomicvalueofanintertie.TableB‐1presentscomparativelife‐cyclecostsforhypothetical25‐mile‐longoverheadACandHVDCintertiesinruralAlaska.Alengthof25mileswasselectedasitrepresentsthesavingspossibleusingarelativelyshortHVDCintertie.Theestimatedlife‐cyclecostfora25‐mile‐longHVDCintertierangesfrom79%to107%ofthelife‐cyclecostofanACintertie.

Table B-1 Estimated Life-Cycle Costs for 25-mile Overhead AC and HVDC Interties

ParameterStandardRUSAC

Intertie

MonopolarTwo‐WireHVDCIntertie(RUSConstruction2)

MonopolarSWERHVDCIntertie

(AlaskaSpecificDesign1)

CostofDiesel($/gal) $7.00pergallon

GenerationEfficiency(kWh/gal) 13kWhpergallon

IntertieEfficiency4 97.7% 93.4% 94.5%

NetAnnualEnergyTransmission(kWh) 1,664,400

AnnualTransmissionLosses4(kWh) 38,300 133,000 114,000

AnnualizedValueofTransmissionLosses($) $21,000 $71,000 $61,000

IntertieDesignLife(years) 20years

IntertieAnnualO&MCosts $40,000 $58,000 $54,000

EffectiveDiscountRate 3%

PresentWorthofTransmissionLosses $307,000 $1,063,000 $912,000

PresentWorthofO&MCosts $595,000 $867,000 $796,000

ConverterStationsInstalledCost $20,000 $2,080,000 $1,160,000

IntertieInstalledCost $9,480,000 $7,120,000 $5,340,000

ESTIMATEDLIFE‐CYCLECOST $10,402,000 $11,130,000 $8,208,000

HVDCLIFE‐CYCLECOSTASPERCENTOFACLIFE‐CYCLECOST 107% 79%

PRESENTWORTHSAVINGS(COST)OFHVDCVS.AC ($728,000) $2,194,000

Notes:1. “Alaska‐SpecificDesign”referstothedesignconceptspresentedinAppendixCofthisreport.2. “RUSConstruction”referstostandardRUSdesignandconstructionmethodsforACinterties,adaptedtoHVDCapplications

asdescribedinAppendixCofthisreport.3. Allmonetaryvaluesarein2012dollars.4. Efficiencyandlossinformationincludesalltransmissionsystemcomponents.


MAY 2012 PAGE B-11

FigureB‐2illustratestheeconomicbreak‐evenlength,andrelativeincreaseinsavingsforlongerHVDCinterties.ThepointsatwhichtheAC“costline”crosseseitheroftheHVDC“costlines”representstheeconomicbreak‐evenlength.TheestimatedHVDCcostsrepresentahypotheticalrangeoflife‐cyclecostsanticipatedforlow‐power(under1MW)ruralAlaskaHVDCsystems.

Figure B-2 Comparative Life-Cycle Cost: Overhead 1-MW HVDC and AC Interties

$0

$5,000,000

$10,000,000

$15,000,000

$20,000,000

$25,000,000

$30,000,000

$35,000,000

$40,000,000

$45,000,000

0 10 20 30 40 50 60 70 80 90 100


Probab

le Life‐Cycle Cost of Overhead HVDC vs. AC In

terties





(LIFE CYCLE COST BASIS)



AC

HVDC

HVDC

COST SAVINGS

RANGE


MAY 2012 PAGE B-12

B.3 COSTANALYSISBASIS

B.3.1 GenerationandLoadAssumptions

Thefollowinggenerationandloadassumptionsareusedasthebasisofthecostanalysis:

● Energytransmittedoverallintertieconfigurationsisassumedtobegeneratedbyadiesel‐electricplantoperatingataconstantefficiencyof13kilowatt‐hours(kWh)pergallon;

● Thepriceofdieselisassumedtobe$7.00pergallon;and

● Noescalatorisappliedtothepriceoffuelovertime.

B.3.2 SystemEfficiencyAssumptions

ThefollowingcircuitpathisassumedfortheACintertiecase:

● Generationat480voltsalternatingcurrent(VAC)incommunity“A”;

● Stepupto7.2/12.47kilovolts(kV)ACatthepowerplantincommunity“A”;and

● Transmissionat7.2/12.47kVACtothereceivingcommunity“B.”

ThefollowingcircuitpathisassumedfortheHVDCintertiecases:

● Generationat480VACincommunity“A,”

● Conversionfrom480VACto50kVdirectcurrent(DC)atthecommunity“A”powerplant,

● Transmissionat50kVDCtothereceivingcommunity“B,”

● Conversionfrom50kVDCto480VACatthepowerplantincommunity“B,”and

● Step‐upfrom480VACto7.2/12.47kVACincommunity“B.”

Thefollowingadditionalassumptionshavebeenmade:

● Bothloadpathsincludeasingle480Vto7.2/12.47kVACtransformer;thecomparativeanalysisdoesnotneedtoconsiderlossesinthistransformer.

● IntertielinelossesarebasedontheoperatingvoltagesandconductorsdescribedinAppendixCforeachintertieconfiguration.

● TwodifferentHVDCconverterefficiencieswereusedtocharacterizetherangeofcomparativeeconomicsforHVDCinterties:

● TheRUS‐basedHVDCintertiecaseusesaconverterefficiencyof96.2%,whichistheefficiencypublishedbyPrincetonPowerSystems,Inc.(PPS)fortheprototypeconverterat50%load(seeAppendixF).

● TheAlaska‐specificHVDCintertiecaseusesahigherconverterefficiencyof97.2%.Thishypotheticalefficiencyresultsinimprovedcomparativeeconomicperformance.

● Transmissionsystemlossesarevaluedbasedontheavoidedcostoffuel.Allotherutilitycostsareassumedtobefixedandnotaffectedbytransmissionsystemlosses.

B.3.3 Operation,Maintenance,andRepairAssumptions

Anannualbudgetof$7,500to$12,300perconverterisprovidedformaintenance,repair,andscheduledcomponentsreplacement.ForHVDCinterties,the$12,300figureisusedfortheRUS‐basedHVDCintertiecase,and$7,500isusedfortheAlaska‐specificHVDCintertiecase.The$7,500perconverter


MAY 2012 PAGE B-13

maintenance,repair,andreplacementbudgetisbasedontheexpectedlifeandreplacementcostofmajorcomponents.Thesecomponentsincludethepowerelectronicsboards,controller,andothermajoritemsthatareexpectedtorequirereplacementduringthe20‐yearlifeofthesystem.SeeAppendixFfordetailsonconvertercomponentlifeandreplacementcosts.

Anannualmaintenanceandrepairbudgetof$1,500permileisassumedforallthreeoverheadintertieconfigurations.

B.3.4 EconomicAssumptions

Adiscountrateof3%hasbeenappliedtobringfuturecashflows(linelosses;OperationandMaintenance,Repair,Replacement,andRehabilitation[OMR&R]costs)topresentvalues.Forpurposesofthiscomparativeanalysis,aprojectlifeof20yearsisusedforallinterties,andnosalvagevalue,disposal,orreplacementcostareconsideredattheendofthe20‐yearlife.

B.3.5 InstalledCostAssumptions

TherangeofinstalledcostsdevelopedfortheconverterstationsinSectionB.5wasusedforthecomparativeeconomicanalysis.ForHVDCinterties,aninstalledcostof$1,040,000perstationisusedfortheRUS‐basedHVDCintertiecase,and$580,000isusedfortheAlaska‐specificHVDCintertiecase

Therangeofinstalledcostsforthethreeintertieconfigurationsarebasedontheestimatedintertiecostspresentedinthefollowingsectionsofthisappendix.


MAY 2012 PAGE B-14

B.4 CASESTUDIES

Thecasestudiesinthissectionprovideproject‐specificexamplesoftheexpectedcostsandresultingbenefitsofusingHVDCsystemstointerconnectcommunitiesandresources.Thesecasestudiesrelyonexistinginformationregardingtheproposedintertieroutes,loads,andrelatedprojectinformation.

TableB‐2summarizesthecasestudiesconsideredinthissection.

Table B-2 Summary of Case Studies

HVDCIntertieCaseStudy

TransmissionCircuit

IntertieType

HVDCIntertieCost

Estimate1

ACIntertieCost

Estimate1

EstimatedHVDCSavings1

PercentCapitalCost

Savings

GreensCreek–Hoonah

5‐MWmonopolarHVDCcircuitwithseareturn2

SubmarineCable

$22.2million $49million

$26.8million 55%

Nome–PilgrimHotSprings

5MWbipolarHVDCcircuit

OverheadLine

$25.7million

$36.3million

$10.6million 29%

Notes:

1. Allcostestimatesarepresentedin2012dollars.

2. Thecasestudyprovidesasubmarineandoverheadintertiecapacityof5MW,andconverterstationcapacityof2MW.ThisprovidesamplemarginforloadgrowthinHoonah.Theconverterstationcapacitycanbeupgradedas‐neededin500kWincrementsupto5MW.

B.4.1 Green’sCreek–HoonahCaseStudy

AnintertiebetweenGreensCreek,ontheAlaskaElectricLightandPower,Inc.(AEL&P)gridthatservesJuneau,andthevillageofHoonah,anisolatedmicro‐gridoperatedbytheInsidePassageElectricCooperative,Inc.(IPEC)hasbeenunderconsiderationforoveradecade.AEL&PandIPEChavecompletedextensivestudyanddesignworkonthisintertie.Studiesidentifieda25‐mile‐longACsubmarinecableandapproximately4milesofoverheadlinenearHoonahasthemosteconomicalmeanstocompletethisinterconnection.24TheproposedintertierouteisshownonFigureB‐3.

Asthedevelopmentofthisprojectcontinued,thecostsoftheACsubmarinecablehaveescalated,untiltheprojectwasfinallyputonholdduetoitsexcessivecost.Hoonahiscurrentlyexploringlocalhydropowerresourcestoreduceitsenergycostsbutcontinuestoviewanintertieasthebestlong‐termsolutionforitsenergyneeds.

ThisHVDCsystemrepresentsatechnologicaladvancethatcanreducethecostoftheGreensCreek–HoonahintertieandincreaseitseconomicfeasibilityascomparedwithHoonah’sotherenergyoptions.Thefollowingsubsectionsofthiscasestudyprovideahigh‐levelanalysisofthemeritsofanHVDCintertieforHoonah.

24(PowerEngineers,2004)


MAY 2012 PAGE B-15

Forpurposesofthiscasestudy,a5‐MWmonopolarHVDCtransmissioncircuitwithseareturnwasselectedtoconnectHoonahwithGreen’sCreek.Thiscircuitconsistsof25milesofsubmarinecableand4milesofoverheadline.Amonopolarcircuitwasselectedbecauseitisexpectedtobetheleast‐costintertiesolutionbetweenHoonahandGreen’sCreek.Otherpotentialconfigurations,suchasabipolarHVDCcircuitutilizingtwosingle‐conductorcables,wouldbemoreexpensivethanthemonopolardesignselected.

Theestimatedcapitalcostsincludea5MWtransmissioncircuit(submarinecableandoverheadline),and2MWconverterstationsatHoonahandGreen’sCreek.Theconverterstationscanbeupgradedto5MWbyadding500kWconvertermodulesasHoonah’sloadincreases.IfHoonah’sloadgrowsbeyond5MW,asecondsubmarinecablecanbeinstalledtoprovidea10MWbipolartransmissionsystem.

Figure B-3 Greens Creek – Hoonah Intertie Route


MAY 2012 PAGE B-16

B.4.1.1 ConceptualDesignBasis

B.4.1.1.1 Load

Hoonah’sannualkWhgenerationisapproximately5,000to5,500megawatt‐hours(MWh).ThepeakloadinHoonahisestimatedat1,200kW.25Aninitialintertiepowercapacityof2,000kWwouldserve100%ofthecommunity’sexistingneedsandprovidea67%marginforfutureloadgrowth(forhandlingpeakload).

B.4.1.1.2 ConceptualIntertieDesign

AmonopolarHVDCintertiecircuitwithsea‐returnisconsideredfortheconceptualdesignoftheGreensCreek–Hoonahintertie.Theintertiehasaninitialcapacityof2,000kW,buttheproposedsubmarinecablecanbeoperatedat5,000kWbyinstallingadditionalmodularpowerconvertersandrelatedupgradesateitherendoftheHVDCsystem.Ahigher‐capacityupgradeto10MWispossiblethroughfurtherconverterstationexpansionandinstallationofasecondcabletoformabipolarHVDCsystem.TheinitialHVDCsystemwouldconsistofthefollowingmajorcomponents:

● AnHVDCconverterstationatHawkInletontheGreensCreekendoftheintertiewitharatedcapacityof2,000kW.Thisstationwouldrequirea69‐kVto480‐volt(V)step‐downtransformer,four500‐kWHVDCconvertermodules,aseareturnelectroderatedfor40amperesofcurrent,andassociatedcontrolsandprotectiveequipment.

● 25milesofmonopolarHVDCsubmarinecable.Thiscablewouldhavearatedcapacityof5MWat50kVDC(100amperes).Thiscablewouldincludea35squaremillimeter(mm2)copperconductor,across‐linkedpolyethylenedielectric,anextrudedleadalloysheath,andtwolayersofcounter‐laidgalvanizedsteelarmorwire.26Afiber‐opticbundleisassumedtobeincludedeitherinthecableconstructionorwithinoneofthearmorwirepositionstofacilitatebroadbandcommunications.

● AsubmarinecablelandingstationatSpasskiBaynearHoonah.ThisstationwouldhousetheshoreendofthesubmarinecableandtransitiontoanoverheadHVDCconductor.Thestationwouldalsoincludeasecondsea‐returnelectrodetocompletethesea‐returncircuit.

● A3.5‐mileoverheadmonopolarHVDCtransmissionlinewithmetallicreturnfromSpasskiBaytotheexistingHoonahpowerhouse.Thistwo‐wireoverheadlinewouldhaveonewireat+50kVDCandthesecondwireclosetoearthpotential.

● Asecond2,000‐kWHVDCconverterstationadjacenttotheexistingHoonahpowerhouse.Thisstationwouldhousethefour500‐kWHVDCpowerconvertersandanACtransformertoconverterthe480VACoutputto4,160VACtointerfacewiththepowerplantbusvoltage.

25AEA,2010a;AEA,2010b26SeeFigure2inAttachmentD‐1toAppendixDofthisreport.


MAY 2012 PAGE B-17

B.4.1.2 EconomicAnalysis

TableB‐3presentstheeconomicanalysisfortheGreensCreek–Hoonahintertiealternatives.TheestimatedinstalledcostfortheHVDCintertieis$22.2million,ascomparedtothecostof$49millionforaconventionalACintertie.TheACintertiecostestimateisbasedonthe2009estimatedcostof$37.5million27adjustedto2012dollars.

Table B-3 Estimated Cost for an Greens Creek – Hoonah HVDC Intertie


PreconstructionRight‐of‐wayacquisition,engineering,survey,permitting $1,600,000


HVDCConverterStations(powerconverters,seaelectrodes,enclosures,ACandDCsidestationequipment) $2,700,000

SubmarineCableSupplyandInstallation $12,400,000

OverheadHVDCLine:SpaaskiBaytoHoonah $900,000

Contingency(onentireproject,25%)1 $3,700,000

TotalEstimatedCost $22,200,000

Notes:1.Acontingencyof25%isappliedtothecostsdevelopedforthisprojectbasedontheuncertaintiesassociatedwiththeproject.Asignificantamountofworkhasalreadybeendonetocharacterizethebathymetryandseafloorconditionsalongtheproposedcableroute.

27IPEC,2009.


MAY 2012 PAGE B-18

TableB‐4presentsestimatedbenefit‐costratiosfortheGreensCreek–Hoonahintertieunderseveralloadgrowthscenarios.ThisanalysisindicatesacleareconomicadvantagetoanHVDCintertiebasedonreasonableloadgrowthforecastsforHoonah.

Table B-4 Estimated Benefit-Cost Ratio of Greens Creek – Hoonah HVDC Intertie

ItemLoadGrowthScenario

ExistingLoad 165%Growth 200%Growth6

AnnualHoonahEnergyGeneration(kWh/yr)1 5,150,000 8,500,000 9,780,000

AEL&PAvoidedCostofEnergy(Juneau)2 $0.06perkWh

IPECAvoidedCostofEnergy(Hoonah)1 $0.20perkWh

IntertieOutageRate3 2%

AnnualHoonahSavings4 $707,000 $1,170,000 $1,340,000

IPECOperation,Maintenance,Repair,ReplacementandRehabilitation(OMR&R)AnnualCosts5 $90,000 $90,000 $100,000

NetAnnualSavings(Cost) $617,000 $1,150,000 $1,340,000

IntertieLifeandDiscountRate 30years,3%

PresentWorthofAnnualSavings(Costs) $12,070,000 $21,090,000 $24,500,000

EstimatedInstalledCost $22,200,000 $22,200,000 $22.200,000

EstimatedBenefit‐CostRatio 0.54 0.95 1.10

Notes:

1. BasedonPowerCostEqualization(PCE)reportsfor2007through2009(AEA,2010a).

2. ApproximateAEL&Penergycost.IPEChascapacity,sonodemandorcapacitychargesareincluded.

3. Assumedvalue.

4. AnnualsavingsarebasedonthedifferentialcostofenergyanddonotconsidereconomicbenefitsinHoonahfromlowercostenergy,oreffectstoAEL&Pofincreasedenergysales.

5. IPEC’sestimatedoperations,maintenance,repair,androutinereplacementcostsincludecostsfortheconverterstations,savingsfromdecreasedoperationandoverhaulofthedieselpowerplantinHoonah,andaone‐timecablerepaireventoverthe30‐yearanalysisperiod.

6. Hoonah’speakloadsundera200%loadgrowthscenariowouldexceedthe2‐MWcapacityoftheintertieconverterstations.Intertiethroughputisreducedby5%toreflectdieselgenerationinHoonah.


MAY 2012 PAGE B-19

B.4.2 PilgrimHotSprings–Nome

PilgrimHotSpringsisageothermalresourcelocatedapproximately60milesnorthofNome.IthasbeenproposedasapowersourcetoreduceNome’srelianceondieselfuelforelectricalgeneration.ACEPiscurrentlystudyingthePilgrimHotSpringsgeothermalresourcetobettercharacterizetheresource’spotentialforpowergenerationandotherapplications.ForpurposesofsizingthetransmissionlinefromPilgrimHotSprings,anelectricalgeneratingcapacityandtransmissioncapacityof5MWisassumed,basedonconversationswithACEP’smanagerforthePilgrimHotSpringsassessmentproject.28TheproposedtransmissionrouteisshownonFigureB‐4.

AbipolarHVDCcircuitusingoverheadlineswasselectedfortheHVDCintertie.Thebipolarconfigurationwasselectedbecauseitprovidesincreasedreliabilitycomparedtoamonopolarlineatareasonableadditionalcost.

ConceptualpowerlinecostsforoverheadACandHVDCintertieswereestimatedtoevaluatethebenefitsofconnectingPilgrimHotSpringstoNomeusinganHVDCintertie.ThecostestimatesindicatethatanHVDCtransmissionlinewouldcost29%lessthananACtransmissionline.

28PersonalcommunicationwithMarcusMager,2012.


MAY 2012 PAGE B-20

Figure B-4 Prospective Transmission Route from Pilgrim Hot Springs to Nome

B.4.2.1 ConceptualDesignBasis

Aroutingstudywasnotperformedaspartofthiscasestudy.Theintertierouteisassumedtofollowtheapproximately70‐mileroadcorridorfromNometoPilgrimHotSprings.Thisisassumedtobetheleast‐costrouteforthepowerlines,astheroadcanbeusedtosupporttheconstructionandlong‐termmaintenanceoftheline.Aroutingstudymayidentifyotherroutesthataremorefavorableduetogeotechnical,landstatus,environmental,orotherfactors.

Forthisanalysis,thetransmissionroutedistanceisassumedtobe60miles.


MAY 2012 PAGE B-21

B.4.2.1.1 Load

Nome’saverageannualelectricityusageisapproximately3,500kW,andmonthlypeakdemandisbetween4and10MW.TheassumedsizeofthePilgrimHotSpringsgeothermalpowerplantisassumedtobe5MW.Theintertieisthereforeassumedtohaveacapacityof5MWandoperateatbetween2and5MW,dependingoninstantaneousdemandinNome.

B.4.2.1.2 ConceptualACIntertieDesign

TheconceptualdesignfortheACintertieisathree‐wire69‐kVACoverheadlineseton45‐footwoodpoleswitharulingspanof400feet.Allpolesareassumedtobefastenedtosteelpilefoundationsformomentsupportandtoresistfrostjackingforces.

TheACtransmissionsystemwouldconsistofthefollowingmajorcomponents:

● A5‐MWgeothermalpowerplantatPilgrimHotSpringsgeneratingat4,160V.

● Asubstationandswitchyardtoincreasevoltagefrom4,160Vto69kV.

● Anapproximately60‐mile‐longoverheadintertiefromPilgrimHotSpringstoNome.

● AsubstationandswitchyardinNometoisolateNomefromthetransmissionlineandstepdownthevoltagefrom69kVto12.47kVfordistributioninNome.

B.4.2.1.3 ConceptualHVDCIntertieDesign

TheconceptualdesignfortheHVDCintertieisabipolarcircuitoperatingat+50and–50kVDC.Thetwocircuitswouldbesupportedonaguyedglass‐fiber‐reinforcedpolymer(GFRP)polefittedwithacrossarmandsuspensioninsulators.Arulingspanof1,000feetisassumed.ThedesignissimilartothatshownonFigureC‐9.

TheHVDCtransmissionsystemwouldconsistofthefollowingmajorcomponents:

● A5‐MWgeothermalpowerplantatPilgrimHotSpringsgeneratingat480V.Itmaybepreferabletoinsteadgenerateat4,160Vandhaveastep‐downtransformertothe480Vinterfacevoltagetothepowerconverters.

● AbipolarHVDCconverterstationconsistingoftwobanksoffive500‐kWpowerconverters.Eachbankwouldforma2.5‐MWpoleonthebipolartransmissionsystem.

● Anapproximately60‐mile‐longbipolarHVDCtransmissionlinefromPilgrimHotSpringstoNome.

● AsecondbipolarHVDCconverterstationinNome.

● AnACtransformertostepuptheACoutputfromtheconvertersfrom480Vupto7.2/12.47kVfordistributioninNome.


MAY 2012 PAGE B-22

B.4.2.2 EconomicAnalysis

TableB‐5presentstheeconomicanalysisforthePilgrimHotSprings–Nomeintertiealternatives.TheestimatedinstalledcostfortheHVDCintertiealternativeis$25.7million,ascomparedtothecostof$36.3millionforaconventionalACintertie.

NoinformationisavailablefortheinstalledcostofageothermalpowerplantatPilgrimHotSpringsorthecostoftheenergyitwouldgenerate,soabenefit‐costratiooftheintertiealternativeswasnotevaluated.

Table B-5 Estimated Installed Cost for a 5-MW Pilgrim Hot Springs – Nome Intertie

CostItemEstimatedInstalledCostforBipolarHVDCIntertie

EstimatedInstalledCostforACIntertie

EstimatedHVDCSavings

PercentCostSavings

PreconstructionActivities(right‐ofwayacquisition,design,survey,permitting)

$3,400,000 $3,400,000 ‐ ‐

Administration/Management $1,000,000 $1,300,000 ‐ ‐

ConverterStationConstruction $4,600,000 $3,000,000 ‐ ‐

OverheadIntertieConstruction $10,800,000 $20,200,000 ‐ ‐

Contingency(30%)1 $5,900,000 $8,400,000 ‐ ‐

TotalEstimatedCost $25,700,000 $36,300,000 $10,600,000 29%

Note:

1. A30%contingencywasappliedtothecostsforthisprojectbecausenoinformationwasavailableforthetransmissionroute.Thislackofdatacreatesrisksduetofactorssuchaslandavailability,geotechnicalconditions,structural(windandice)loadings,andenvironmental(bird,wildlife,andaesthetics)factors.Someoftheserisksaremitigatedbytheuseofcostdatafortherobustconceptualdesigns(i.e.,Alaska‐specificconstruction)usedfortheHVDCsystem.TheAlaska‐specificconceptualdesignisassumedtobeadequatefortheexpectedgeotechnicalandstructuralconditionsalongtheroute.Environmentalandlandavailabilityissues,whichcouldrequirealongerrouteordeparturefromtheroadcorridor,poserelativelygreaterrisksthanlinedesignconsiderations.Thenetresultofthesefactorsresultsinthe30%contingencyusedforthecasestudyeconomics.


MAY 2012 PAGE B-23

B.5 DETAILEDHVDCINTERTIECOSTINFORMATION

B.5.1 OverheadIntertieCostDetail

ThisreportconsidersdifferentoverheaddesignconceptsforHVDCinterties.Thissectionpresentsarangeofestimatedcostsfortheseconcepts.

Thetwo‐wiremonopolarintertieadaptedfromstandardRUSpracticeisestimatedtohavethehighestinstalledcost.Incontrast,themonopolarSWERintertiebasedonAlaska‐specificdesignconceptsisestimatedtohavethelowestinstalledcost.

TableB‐6presentsabreakdownoftheestimatedinstalledcostsfor25‐mileoverheadintertiesinruralAlaskausingthedesigncasesandconceptspresentedinAppendixC.


MAY 2012 PAGE B-24

Table B-6 Estimated Cost for a 25-mile Overhead HVDC Intertie

CostItemMonopolarSWER,AlaskaSpecificConstruction

Two‐WireMonopolarHVDC,RUS–BasedConstruction

Per‐MileCost ProjectCost Per‐MileCost ProjectCost

PreconstructionRight‐of‐wayacquisition,design,survey,permitting $58,000 $1,450,000 $56,000 $1,400,000

Administration/Management $13,000 $325,000 $17,000 $425,000

Materials(intertieonly) $48,000 $1,200,000 $47,000 $1,175,000

ConverterStations(onper‐milebasis) $62,000 $1,550,000 $62,000 $1,550,000

Shipping $15,000 $375,000 $25,000 $625,000

Mobilization/Demobilization $37,000 $925,000 $94,000 $2,350,000

Labor $67,000 $1,675,000 $71,000 $1,775,000

TotalCost $300,000 $7,500,000 $372,000 $9,300,000

Note:Lineitemcostsincludeanembedded25%contingency.


MAY 2012 PAGE B-25

B.5.2 SubmarineCableIntertieCostDetail

Anumberofsite‐specificfactorsinfluencethecostofsubmarinecableapplicationsforHVDCapplicationsinAlaska.Thesearethefollowing:

● CablelayingvesselsarespecializedequipmentthatmustbemobilizedtoAlaska.MobilizingthesevesselstoAlaskaiscostlyandprojectdependant.Mobilizationcostsresultinshortsubmarineintertiesbeingsignificantlymoreexpensiveonaper‐milebasisthanlongsubmarineinterties.

● Marinetrafficinfluencessubmarineintertiecosts.Shallowercableroutesmustconsidercommercialfishingactivity,anchoring,andrelatedmarinetrafficthatmayposeahazardtothecable.

● Theseafloorconditionsalongthecableroutealsoinfluencecosts.Steepslopes,ruggedexposedrock,orunstableslopeswilltendtoincreasecostsorprojectrisk.

● Thedepthofthecableroutewillinfluencecosts.Deeperroutesrequirestronger,heavier,andmorecostlycables,whichinturncanrequirelarger,moreexpensivecablelayingvessels.

Asaresult,agenericper‐milecostoflow‐powersubmarinecablesisnotmeaningfulwithoutconsiderationoftheproject‐specificfactors.

B.5.3 UndergroundCableIntertieCostDetail

Anumberofsite‐specificfactorswillstronglyinfluencethetechnicalfeasibilityandcostofundergroundcableapplicationsforlow‐powerHVDCapplicationsinAlaska.Thesearethefollowing:

● Presenceofgroundsusceptibletofrostcrackingorpolygonalcracking.Thesegroundcrackscanimposelargetensionforcesoncablesandcausemechanicalfailureofthecable,resultinginelectricalfaults.

● Geotechnicalconditionsalongthecableroutewillinfluencethecostofcableinstallation.

● Steepterrainorotherlocalconditionsmaypreventuseofundergroundcable.

EstimatedcostsforHVDCintertiesusingundergroundcablesarepresentedinTableB‐7.


MAY 2012 PAGE B-26

Table B-7 Estimated Costs for a 25-mile Underground HVDC Intertie

CostItem EstimatedPer‐MileCost

PreconstructionRight‐of‐wayacquisition,design,survey,permitting $45,000


Materials(intertieonly) $80,000

Converterstations(onpermilebasis) $62,000

Shipping $20,000

Mobilization/Demobilization $10,000

Labor $20,000

TotalCost $250,000

Note:Lineitemcostsincludeanembedded25%contingency.

TheestimatedcostsinTableB‐7arebasedonthefollowingassumptions:

● Terrainandconditionsaresuitableforuseofatrack‐mountedtrenchersuchasaDitchWitchRT115Quad,whichcancutatrenchthroughfrozengroundduringthewintermonthsovermostterrain;

● 1/0fullconcentricneutraljacketed35‐kVACcablewithethylenepropylenerubber(EPR)dielectricina2‐inchduct;

● Awaterblockingantifreezegelcompoundisused;

● Afiber‐opticcableinductisinstalledinthesametrench;

● Limitedbrushingisnecessarytocleartheroute;

● Cablereelsarespottedalongthelinewithahelicopter;and

● Thecableinstallationdepthisaminimumof18inches.

B.5.4 ConverterStationCostDetail

TheHVDCconverterstationswillincludethemajorcomponents:

● HVDCpowerconverters;

● Converterenclosures,whichmayconsistofdedicatedenclosuresoruseofanexistingbuilding,suchasanexistingpowerplant;

● ProtectionandswitchingequipmentontheACandHVDCsidesoftheconverters;

● ACtransformers,dependingontheACinterfacevoltageandwiring;and

● Groundingstations,includingthegroundconductorfromtheconverterstationtothegroundingstation.

Theestimatedinstalledcomponentcostsfora1‐MWmonopolarHVDCconverterstationispresentedinTableB‐8.Therangeofcostsisbasedonthepresenceofexistinginfrastructureandproject‐specificconditions.


MAY 2012 PAGE B-27

Table B-8 1-MW HVDC Converter Station Cost Estimate


1‐MWHVDCPowerConverter $220,000to$280,000

ConverterEnclosure $40,000to$160,000

AC‐SideandHVDC‐SideProtectiveandSwitchingEquipment $100,000to$190,000

1‐megavoltamperes(MVA)ACTransformer(7.2/12.4kV–480V) $0to$30,000

GroundingStation $100,000to$170,000

Contingency(25%) $120,000to$210,000

Total,1‐MWHVDCConverterStation $580,000to$1,040,000

B.5.4.1 ConverterCostDetail

BasedonPhaseIIdevelopmentefforts,PPSestimatesthatthecommercialcostoftheHVDCpowerconverterswillbe$250,000+/‐10%per1‐MWpowerconverter.PPSstatesthatasmanufacturingvolumesincrease,theper‐convertercostshoulddecrease.PPSforecastsa5%to10%discountat10unitsanda20%to30%discountat100units.SeeAppendixFforamoredetaileddiscussionofconvertercosts.

B.5.4.2 ConverterEnclosureCostDetail

Estimatedcostsassumethatamodular,prefabricatedenclosurewillbesenttothecommunitywiththetwo500‐kWpowerconverterunitsalreadyinstalled.Thisconvertermodulewillthenbesetinplaceonasuitablefoundation.EstimatedcostsarelistedinTableB‐9.

Table B-9 HVDC Converter Enclosure Cost Detail


PowerConverterEnclosure $68,000

Foundation $30,000

Labor $27,000

Shipping $35,000

Total,1‐MWHVDCConverterEnclosure $160,000


MAY 2012 PAGE B-28

IncommunitiesthatwillbeprimarilyservedbyanHVDCintertie,itmaybeappropriatetolocatetheconvertersinsidetheexistingpowerhouseorothersuitableexistingstructure.Thiswouldhavethefollowingadvantages:

● Theexistingpowerhousewouldalreadyhaveastep‐downtransformersizedforthefullcommunityload,

● Wasteheatfromtheconverterswouldprovideallorpartoftheheatforthepowerplantbuilding,and

● Thiswouldachieveprojectcostreductionbyeliminatingtheneedforadedicatedconverterenclosureandtheneedtopurchaseorleaselandtositetheconverter.

B.5.4.3 SwitchgearandSwitchyardEquipmentCostDetail

SwitchgearisrequiredontheACsideoftheconvertersforisolationandprotectionpurposes.Dependingonthedesireddegreeofsystemautomation,theswitchgearmayalsointerfacebetweentheconvertercontrolsandthepowerplantcontrolstoallowremotedispatchofgeneratorsandtheHVDCpowerconverter.

Similarisolation,protection,andmonitoringequipmentisneededintheHVDCswitchyardontheHVDCsideoftheconverter.Ataminimum,manualdisconnectswitches(nonloadbreak),surgearrestors,andfusesarerequired.CurrentandvoltagesensorsareneededontheHVDClineaswell.

EstimatedswitchgearandswitchyardcostsarepresentedinTableB‐10.

Table B-10 Switchgear and Switchyard Cost Detail


ACSwitchgearSection(Fuses,DisconnectSwitches[loadbreak]) $25,000to$35,000

HVDCManualDisconnectSwitch(nonloadbreak) $2,000to$20,000

HVDCSurgeArrestor $10,000to$15,000

HVDCFuse $2,000to$8,000

ACandDCSensors $30,000to$48,000

OtherMaterials $12,000to$16,000

Shipping $5,000to$18,000

Labor $14,000to$20,000

Total,1‐MWHVDCConverterStationSwitchgearandSwitchyard $100,000to$190,000


MAY 2012 PAGE B-29

B.5.4.4 ACTransformerCostDetail

Thegridinterfaceonthepowerconvertersisthree‐phase480‐VAC.Incommunitieswheretheconverterisconnecteddirectlytothe480‐Vpowerplantbuss,noadditionaltransformerisrequired.Incommunitieswheretheconverterconnectstothelocaldistributiongrid,astep‐uptransformerisrequired.Thetransformerisassumedtobeathree‐phase480/12.47kVtransformer.

B.5.4.5 GroundingStationCostDetail

AgroundingstationwillneedtobeprovidedateachHVDCconverterstation,regardlessoftheHVDCcircuitconfiguration.Theconceptualdesignofa1‐MW50kVDCgroundingstationispresentedinAppendixE.EstimatedcostsforthisstationarepresentedinTableB‐11,andinclude1mileofoverheadlinebetweentheconverterstationandthegroundingstation.

Costsforgroundingstationswilldependonthelocalgeotechnicalconditions,thedistancebetweentheconverterandgroundingstations,andotherfactors.

Table B-11 HVDC Grounding Station Cost Detail

CostItem ConceptualCost

SiteInvestigations $26,000to$33,000

Materials $25,000to$45,000

Labor $34,000to$46,000

Equipment $7,000to$12,000

Shipping $8,000to$34,000

Total,1‐MWHVDCGroundingStation $100,000to$170,000


MAY 2012 PAGE B-30

B.6 DETAILEDACINTERTIECOSTINFORMATION

ThissectionpresentscostbaselinesforremoteAlaskaACintertiestoallowcomparisontotheHVDCalternativespresentedinthisreport.CostbaselinesforACintertieprojectsweredevelopedusingtwomethods.Thefirstmethodwastodevelopconceptualcostestimatesconsideringunitcostsforlabor,materials,mobilization,etc.Thesecondmethodwastoreview,whereavailable,theactualcostsofrecentrelevantACintertieprojectsinAlaska.Forbothmethods,twotypesofintertieswereanalyzed:

1. OverheadintertielinesinarcticandsubarcticregionsofwesternAlaska.Theseregionspresentsomeofthegreatestgeotechnicalandlogisticalchallenges;therefore,theytendtohavethehighestinstalledcostsforoverheadinterties.

2. SubmarinecableintertiesinruralAlaska.FormanypartsofAlaska,andinparticularthesoutheast,submarinecablesaretheonlyviablemeansofbuildingapowerintertie.

ThecostbaselinesaresummarizedinTableB‐12.

Table B-12 Cost Baselines for Remote Alaska AC Intertie Construction

TypeofACElectricIntertie1CostBaselineby

UnitCost/QuantityMethodCostBaselinefromRecent

ProjectExperience

OverheadInterties2 $440,000permile $450,000permile+/‐50%

SubmarineCableInterties3 N/A $1,300,000permile+/‐35%

Notes:1. Intertiepowercapacitywillaffectcost.Seesubsequentnotesforthespecifictypesofintertiesconsideredtodevelop

theseconceptualcosts.2. IntertiesarestandardRUSthree‐phase14.4/24.9kVconstruction,usingsteelpilefoundations.3. Intertiesaresingle‐bundledthree‐conductorarmoredcable.


MAY 2012 PAGE B-31

B.6.1 CostBaselinesforOverheadACInterties

B.6.1.1 CostBaselineforOverheadACIntertiesUsingUnitCostsandQuantities

AcostbaselinefortypicalACtransmissionsystemshasbeenestimatedfor10‐mileand25‐mileintertieconcepts.Theseconceptsarebasedonastandardfour‐wirethree‐phase14.4/24.9kVRUSpowerlineusingdrivensteelpilefoundations.TheestimatedinstalledcostsarepresentedinTableB‐13.

Table B-13 Estimated Costs for Overhead AC Interties

CostItem10‐MileIntertie 25‐Mileintertie

Per‐MileCost

ProjectCostPer‐MileCost

ProjectCost

PreconstructionRight‐of‐wayacquisition,design,survey,permitting

$61,000 $610,000 $39,000 $975,000

Administration/Management $18,000 $180,000 $18,000 $425,000

Materials $71,000 $710,000 $71,000 $1,775,000

Shipping $36,000 $360,000 $33,000 $825,000

Mobilization/Demobilization $136,000 $1,360,000 $125,000 $3,125,000

Labor $111,000 $1,110,000 $111,000 $2,675,000

TotalCost $440,000 $4,400,000 $397,000 $9,875,000

Theper‐milecostofoverheadACintertiesdecreasesastheintertiegetslonger.Thisisinfluencedbythefollowingfactors:

● Thescopeandcomplexityofenvironmental,right‐of‐way,design,andpermittingissuesfortheproject.

● Thequalityofaccesscorridorsalongtheintertieroute.Theestimatedcostsassumethatper‐milelaborcostsareindependentofintertielength.

● Theconstructionplanandschedule.Theestimatedcostsassumethatper‐milemobilization/demobilizationcostsdecreaseslightlywithincreasingintertielength.

Thisreportfindsthatper‐milecostsfortypicaloverheadACintertiesdecreaseapproximately10%astheintertielengthincreasesfrom10to25miles.Further,anadditionaldecreaseof5%occursfrom25to50miles.Costsareconstantonaper‐milebasisfrom50to100miles.


MAY 2012 PAGE B-32

B.6.1.2 CostBaselineforOverheadACIntertiesUsingComparableProjectCosts

ConstructioncostdatacompiledforsevenremoteoverheadintertielinesbuiltinwesternAlaskaoverthepast20yearsarepresentedinTableB‐14.ThelinesselectedareconsideredrepresentativeofthemostdifficultlogisticalandgeotechnicalconditionscommoninAlaska.BasedonTableB‐14,theconceptualper‐milecostforaremoteAlaskaoverheadACintertieis$450,000permile,+/‐50%(2012$).

ThecostdataarepresentedasageneralcostbaselineforremoteAlaskaoverheadinterties.

Table B-14 Installed Costs of Recent Remote Alaska Overhead AC Interties

IntertieProjectInstalledCost1

YearBuilt

Length

(miles)Per‐MileCost(2012$)2

Kobuk–Shungnak3 $1.1M 1991 11 $276,500

ToksookBay–Tununak4,5 $2.0M 2005 6.6 $440,200

Nunapitchuk–OldKasigluk–AkulaHts.5,6 $1.9M 2006 4.2 $594,400

ToksookBay–Nightmute7,8 $6.9M 2009 18 $495,800

Bethel–Napakiak5,9 $3.1M 2010 10.5 $344,400

BrevigMission–Teller10 $4.7M 2011 6.8 $730,200

Emmonak–Alakanuk11 $2.9M 2011 11 $267,300

AverageCostperMile,2012Dollars: $449,800

AverageCostperMile,(ExcludingHighestandLowest‐CostProjects): $430,300

Notes:1. Installedcostsareinnominaldollarsatthetimeofconstruction.Duetothelimiteddetailandvarietyofsourcesforcost

data,itisnotalwayspossibletodiscernifcostsforagivenprojectincludepreconstruction,construction,sharedmobilizationwithseparatebutconcurrentprojects,andsimilarcomplicatingfactors.Adjustingfortheseunknownfactorsmayincreaseordecreasetheprojectcostthatispresentedinthetable.

2. Projectcostsareadjustedto2012dollarsusingacustomescalatorbasedonAlaskalaborcostsandcommoditypricesrelevanttooverheadintertieconstruction.

3. Estimatedcostfortheproject.TheprojectconsistedofreplacinganACSWERintertiewithaconventionalRUSACintertie(Petrie,personalcommunication,2012).

4. TheprojectconsistedofanewoverheadACintertie(DenaliCommission,2008b).5. EntireintertiewassetonH‐pileorroundpilefoundations(DenaliCommission,2008a,2008b,and2010).6. TheprojectconsistedofreplacinganexistingoverheadACintertiewithanewoverheadACintertie.Thecostwas

reducedby$300,000forstep‐downtransformersforservicesalongtheintertieroutethatarenotpartofthe“intertie”cost(DenaliCommission,2008a)

7. TheprojectconsistedofanewoverheadACintertie(DenaliCommission,2009).8. Approximately30%ofintertieissetonsteelpilefoundations(DenaliCommission,2009).9. TheprojectconsistedofreplacinganACSWERintertiewithaconventionalRUSACintertie(DenaliCommission,2010).10. TheprojectconsistedofanewACintertieincludingoverhead,underground,andsubmarinecablesegments.Cost

includespreconstructionandbudgetedconstruction(DenaliCommission,2011).11. Thisistheestimatedcostforaproposedintertiebuiltin2011.Theintertieprojectsharedmobilizationcostswith

concurrentinstallationofwindturbinesinEmmonak(AVEC,2008).


MAY 2012 PAGE B-33

B.6.2 CostBaselineforSubmarineCableACInterties

ConstructioncostdatawerecompiledforthreeACsubmarinepowercablesinstalledorproposedinAlaskaoverthepast15years;thesedataarepresentedinTableB‐15.Veryfew“low‐power”ACsubmarinecableshavebeenbuiltinAlaska–thecablesinTableB‐15eachhaveacapacityof10to15MW.Theselineswerereviewedbecausetheyarethesmallestsubmarinecableswithavailablecostdata.Theindicatedconceptualper‐milecostforaACsubmarineintertieinAlaskais$1,300,000permile,+/‐35%(2012$).

Submarinecablecostsareprojectdependentandhaveasignificantcostvariability.Shortcableprojectsinparticularcanbeexpectedtohavesignificantlyhigherper‐milecostduetothefixedmobilizationcostofspecializedcable‐layingvessels.

ThecostdataprovideageneralcostbaselineforremoteAlaskasubmarinepowercables.

Table B-15 Installed Costs of Recent Remote Alaska Submarine Cable Interties

IntertieProjectInstalledCost1

YearBuilt/Proposed

Length(miles)

Per‐MileCost(2012$)2

Haines–Skagway3 $5.86M 1998 15 $880,000

Homer–SouthKatchemakBay5 $2.5M 2001 4.5 $1,200,000

Green’sCreek–Hoonah4 $37.5M 2009 29 $1,700,000

AverageCostperMile,2012Dollars: $1,300,000

Notes:1. Installedcostsareinnominaldollarsatthetimeofconstruction.Duetothelimiteddetailandvarietyofsourcesforcost

data,itisnotalwayspossibletodiscernifcostsforagivenprojectincludepreconstruction,construction,sharedmobilizationwithseparatebutconcurrentprojects,andsimilarcomplicatingfactors.Adjustingfortheseunknownfactorsmayincreaseordecreasetheprojectcostthatispresentedinthetable.

2. Projectcostsareadjustedto2012dollarsusingacustomescalatorbasedonAlaskalaborcostsandcommoditypricesrelevanttopowerlineconstruction.

3. TheHaines‐Skagwaycablehasamaximumdepthof1,500feetandaratedcapacityof15MW(INEEL,1998).4. TheGreen’sCreek–Hoonahcablehasnotbeenbuiltduetoitscost.Installedcostsarethemostrecentestimates

available.Thiscablerouteincludesdepthsto2,600feet.Costsincludeapproximately4milesofoverheadline(IPEC,2009).

5. TheHomer–SouthKatchemakBaycablehasamaximumdepthof600feetandaratedcapacityofapproximately12MW(AJOC,2001).


MAY 2012 PAGE B-34



MAY 2012 PAGE C-1

APPENDIXC

CONCEPTUALDESIGNOF

OVERHEADHVDCINTERTIELINES


MAY 2012 PAGE C-2



MAY 2012 PAGE C-3

TABLEOFCONTENTS

C.1 INTRODUCTION........................................................................................................................................................7 C.1.1 RURALUTILITIESSERVICE(RUS)DESIGNAPPROACH,MODIFIEDFORHVDCINTERTIES................................7 C.1.2 ALASKA‐SPECIFICDESIGNAPPROACHFORHVDCINTERTIES..................................................................................7

C.2 DESIGNCRITERIAFOROVERHEADINTERTIELINES.............................................................................8 C.2.1 GEOTECHNICALCONDITIONS...........................................................................................................................................8 C.2.2 ENVIRONMENTALLOADS.................................................................................................................................................8

C.3 CONCEPTUALDESIGNOFOVERHEADHVDCTRANSMISSION,RUSSTANDARDPRACTICE10 C.3.1 CONVENTIONALACINTERTIEDESIGN........................................................................................................................10 C.3.2 MONOPOLARSINGLE‐WIRETRANSMISSIONWITHEARTH‐RETURNPATH(SWER),CONVENTIONALLYBUILT

............................................................................................................................................................................................13 C.3.3 MONOPOLARTWO‐WIRETRANSMISSIONWITHMETALLICCONDUCTOR‐RETURNPATH(TWMR),

CONVENTIONALLYBUILT...............................................................................................................................................16 C.3.4 BIPOLARTWO‐WIRETRANSMISSION,CONVENTIONALLYBUILT...........................................................................19

C.4 CONCEPTUALDESIGNOFOVERHEADHVDCTRANSMISSION,ALASKA‐SPECIFICMETHODS22 C.4.1 MONOPOLARSINGLE‐WIRETRANSMISSIONWITHEARTH‐RETURNPATH(SWER,ALASKA‐SPECIFICDESIGN

............................................................................................................................................................................................23 C.4.2 MONOPOLARTWO‐WIRETRANSMISSIONWITHMETALLICCONDUCTOR‐RETURNPATH(TWMR),ALASKA‐

SPECIFICDESIGN.............................................................................................................................................................26 C.4.3 BIPOLARHVDCINTERTIELINE,ALASKASPECIFICDESIGN...................................................................................29 C.4.4 CONCEPTUALDESIGNANALYSIS...................................................................................................................................32 C.4.5 MAINTENANCEMETHODS..............................................................................................................................................33

C.5 CONCEPTUALDESIGNANALYSIS...................................................................................................................35 C.5.1 STRUCTURALDESIGN......................................................................................................................................................35 C.5.2 FOUNDATIONDESIGN.....................................................................................................................................................35 C.5.3 ANALYSISOFTHERMOPROBEPERFORMANCE............................................................................................................35 C.5.4 ELECTRICALDESIGN.......................................................................................................................................................44

C.6 TESTINGOFOVERHEADDESIGNCONCEPTS............................................................................................49 C.6.1 TESTOBJECTIVES............................................................................................................................................................49 C.6.2 TESTSITE.........................................................................................................................................................................49 C.6.3 INSTALLATION..................................................................................................................................................................49 C.6.4 MONITORING....................................................................................................................................................................50

APPENDIXCATTACHMENTS...........................................................................................................................................63 ATTACHMENTC‐1:ZARLINGAEROCONSULTING(ZAE)THERMALANALYSISOFTHERMOPILE.....................................63 ATTACHMENTC‐2:ARCTICFOUNDATIONS,INC.(AFI)SHOPDRAWINGS............................................................................91


MAY 2012 PAGE C-4



MAY 2012 PAGE C-5

LISTOFTABLES

TableC‐1 ConceptualDesignDataforConventionalACIntertieLine....................................................12

TableC‐2 ConceptualDesignDataforConventionallyBuiltMonopolarSWERHVDCIntertieLine..........................................................................................................................................................................15

TableC‐3 ConceptualDesignDataforConventionallyBuiltMonopolarHVDCwithMetallicReturn..........................................................................................................................................................................18

TableC‐4 ConceptualDesignDataforConventionallyBuiltBipolarHVDCIntertieLine...............21

TableC‐5 ConceptualDesignDataforAlaska‐SpecificMonopolarSWERHVDCIntertieLine....25

TableC‐6 ConceptualDesignDataforAlaska‐SpecificMonopolarMetallic‐ReturnIntertieLine28

TableC‐7 ConceptualDesignDataforAlaska‐SpecificBipolarHVDCIntertieLine..........................31

TableC‐8 SummaryofResultsfromThermoprobeModelingbyZAE....................................................37


MAY 2012 PAGE C-6

LISTOFFIGURES

FigureC‐1 TangentPoleforConventionalACIntertieLine..........................................................................11

FigureC‐2 ConventionalTangentPoleforMonopolarSWERHVDCIntertieLine..............................14

FigureC‐3 ConventionalTangentPoleforMonopolarHVDCwithMetallicReturn...........................17

FigureC‐4 ConventionalTangentPoleforBipolarHVDCIntertieLine...................................................20

FigureC‐5 Alaska‐SpecificTangentPoleforMonopolarSWERHVDCIntertieLine..........................24

FigureC‐6 Alaska‐SpecificTangentPoleforMonopolarMetallic‐ReturnIntertieLine....................27

FigureC‐7 Alaska‐SpecificTangentPoleforBipolarHVDCIntertieLine...............................................30

FigureC‐8 PrototypeMicro‐ThermopileTripodPoleFoundation............................................................38

FigureC‐9 ShopDrawingofPrototypeGFRPPoleBaseAdapterforMicro‐ThermopileFoundation(Sheet1of3)..............................................................................................................................................39



FigureC‐12 GalvanizedScrewAnchorswith8‐InchFlights...........................................................................43

FigureC‐13 TypicalBipolarHVDCTransmissionLineUsingSuspensionInsulators...........................45

FigureC‐14 TypicalTangentStructureUsingPostInsulators.......................................................................46

FigureC‐15 TypicalAngleStructureUsingSuspensionandPostInsulators...........................................47

FigureC‐16 TypicalTangentStructureUsingSuspensionandPostInsulators......................................48

FigureC‐17 InstallingMicro‐ThermopileforGuyAnchor...............................................................................51

FigureC‐18 SettingMicro‐ThermopileGuyAnchorwithSandSlurryBackfill.......................................52

FigureC‐19 InstallingMicro‐ThermopileforGuyAnchor...............................................................................53

FigureC‐20 Micro‐ThermopilesStagedatFairbanksTestSiteforInstallationofPrototypeFoundations..........................................................................................................................................................................54

FigureC‐21 Micro‐ThermopileTripodforPrototypePoleFoundation.....................................................55

FigureC‐22 InstallingHelicalScrewAnchorforGuyAnchor.........................................................................56

FigureC‐23 GuyAttachedtoMicro‐ThermopileFoundation.........................................................................57

FigureC‐24 AssemblingthePrototypeGFRPPoleSplice.................................................................................58

FigureC‐25 InstalledGFRPPole,Micro‐Thermopiles,andAdapterPlate.................................................59

FigureC‐26 PrototypeGFRPPoleFoundationDuringInstallation..............................................................60

FigureC‐27 PrototypePoleattheFairbanksTestSite......................................................................................61

FigureC‐28 PrototypePoleattheFairbanksTestSite......................................................................................62


MAY 2012 PAGE C-7

C.1 INTRODUCTION

Theconceptualoverheadtransmissionlinedesignalternativespresentedinthisappendixrequiredconsiderationofsite‐specificconditions,codes,utilityandlenderrequirements,constructionmethodologies,standarddesignpractices,andprojecteconomics.

Twoconceptualdesignapproachesforoverheadhigh‐voltagedirectcurrent(HVDC)intertieshavebeenevaluated,eachwithacapacitytosupply1megawatt(MW)at50kilovolts(kV)DC:(1)U.S.DepartmentofAgriculture(USDA)RuralUtilitiesService(RUS)designapproach,modifiedforHVDCinterties;and(2)Alaska‐specificdesignapproachforHVDCinterties.Eachisdescribedbelow.

C.1.1 RuralUtilitiesService(RUS)DesignApproach,ModifiedforHVDCInterties

ThefirstconceptualdesignapproachisbasedontheuseofstructuresthatareconstructedinaccordancewiththeRUSstandardpracticesforconventional12.4/24.9kilovolt(kV)alternatingcurrent(AC)distributionlines.29TheseRUSstandardpracticesarecurrentlyusedtodevelopACintertiesthroughoutAlaskaandarewidelyacceptedbytheutilityindustry.HVDCtransmissionrequiresfewerconductorsthanAC,resultinginreducedloadsonthesupportingstructures.Asaresult,theconceptualdesignsdevelopedwiththeRUSapproachhavelongerrulingspansthantypicalAClines.ThisresultsinfewertransmissionstructuresfortheHVDCintertieandanassociatedcomparativereductioninconstructioncost.

C.1.2 Alaska‐specificDesignApproachforHVDCInterties

ThesecondconceptualdesignapproachtakesthelogisticandtechnicalchallengesofconstructioninruralAlaskaintoconsiderationandfocusesonmethodstoreduceconstructioncostswithoutcompromisingperformanceorlong‐termmaintainability.Thisdesignapproachincorporatescost‐savingfeaturesmadepossiblethroughHVDC‐specificdesignalternatives,materials,andconstructionmethods.DesignfeaturesofthisconceptincludetheuseofguyedcompositestructurestoallowsignificantlylongerrulingspansthanispossiblewithRUSstandardpractice.Thereducednumberofstructures,lesscostlyfoundations,andreducednumberofconductorsallresultinadditionalsavingscomparedwithintertiesbuilttoRUSstandardpractices.

ThefollowingthreeHVDCtransmissioncircuitconfigurationsareconsideredforeachoftheHVDCconceptualdesignapproaches:

● Monopolarsingle‐wiretransmissionwithearth‐returnpath(SWER);

● Monopolartwo‐wiretransmissionwithmetallicconductor‐returnpath(TWMR);

● Bipolartwo‐wiretransmission.

Schematicfiguresareprovidedinthisappendixforeachoftheseconceptualdesigns.Detailedreportsthataddressvarioustechnicalaspectsoftheassumedconditionsandloadingsusedtodeveloptheseconceptualdesignsareprovidedasattachmentstothisappendix.

29 Inthisreport,theterm“RUSstandardpractice”referstooverheadintertielinedesignsbasedonthemethodsandmaterials

presentedinRUSdesignmanualsfortransmissionanddistributionlineconstruction,includingbutnotlimitedto:REA,1982,RUS,1998,2002,2003a,2003b,2003c,and2009.


MAY 2012 PAGE C-8

C.2 DESIGNCRITERIAFOROVERHEADINTERTIELINES

ThefollowingdesigncriteriahasbeendevelopedasabasisfortheconceptualdesignoftheHVDCoverheadintertielines.

C.2.1 GeotechnicalConditions

Basedontheanalysisdescribedbelow,conceptualfoundationdesignalternativesforaguyedpoleutilizethreethermoprobemicropilesforthepolebaseandhelicalanchorsfortheguys.TheconceptualfoundationdesignalternativesarepresentedonFiguresC‐9throughC‐11.Theoverheadsystemtestsiteincludesinstallationofbothoftheseprototypefoundations,aswellasthermoprobemicropilesandscrewanchorstorestraintheguywires.

PolarconsultcontractedwithGolderAssociates,Inc.(Golder)toidentifyandcharacterizethemostcommongeotechnicalconditionsthatposethegreatesttechnicalandeconomicchallengesforruralAlaskaoverheadintertielinesascurrentlydesigned.

Insummary,GolderidentifiedthreeconceptualgeotechnicalconditionsrepresentingthegreatesteconomicchallengeforruralAlaskaoverheadinterties.Thesearesummarizedbelow.

Profile“A”:Icy,“warm”permafrostcomprisedprimarilyoflow‐plasticitymineralsiltbelowanactivelayerwithhigherorganiccontent.Thepermafrosttemperatureintheupper15feetbeneaththeactivelayerwouldhaveamaximumtemperature(occurringinlateautumn)of31.0to31.5°F.Theactivelayerisassumedtobeapproximately3.5feetthick,consistingoforganicsoilsandsurfacepeat.Surfacevegetationintheprojectfootprintisassumedtoremainundisturbedbylineconstruction.ThisprofileisintendedtorepresentagenericgeotechnicalprofileinthelowerYukonandKuskokwimareas.

Profile“B”:Warmanddegradingpermafrost,primarilylow‐tomoderate‐plasticitymineralsiltwithelevatedporewatersalinity.Taliksorthinunbondedsoillayersmaybepresentinthefrozensoilmatrixwithin15to20feetbelowgrade.Temperaturesareexpectedtoaverage31.5to31.8°Fintheuppermost15feetbelowtheactivelayer.Degradingpermafrostconditionsareexpectedbelowtheactivelayerinsomeareasalongtheintertiealignment.Surfacevegetationintheprojectfootprintisassumedtoremainundisturbedbylineconstruction.ThisprofileisintendedtorepresentagenericgeotechnicalprofilealongcoastalareasofwesternAlaska.

Profile“C”:Thawedorunfrozenmineralsoil,generallysandywithsiltcontentsof20%to40%totaldryweight.Highlydegradedpermafrostwithsignificantthawedzonesispresentbelowtheactivelayer.Soilmoisturecontentsrepresentsaturatedconditionsandnosignificantporewatersalinityispresent.Ahigherorganiccontentactivelayerispresent,withgrasses,brush,andtreesforvegetation.Theactivelayerisapproximately5feet.ThisprofileisintendedtorepresentagenericgeotechnicalprofilealongthepermafrostmarginininteriorAlaskaorinlandareaswithsignificantpermafrostdegradation.

C.2.2 EnvironmentalLoads

Thefollowingloadingswereanalyzedforeachconceptualdesign:

Case1:NationalElectricalSafetyCode(NESC)250B=½inchofice,4poundspersquarefoot(psf)wind.

Case2:NESC250C=noice,120mphwind.


MAY 2012 PAGE C-9

Case3:NESC250D=¼inchofice,80mphwind.

Case4:Highice=1inchice,nowind,30degreesFahrenheit(°F).

Case5:Noiceorwind.

TheseloadcasesareconsideredsufficientformanyruralAlaskaoverheadintertieapplications.Specificlocationsmaybesubjecttohigherand/orlowerwindand/oriceloadings.30Exceptwherespecificallystatedotherwise,eachoftheconceptualdesignspresentedinthissectioncomplywiththemoststringentoftheseloadconditions.

30 Section4.6ofthePhaseIFinalReportprovidesasummaryofenvironmentalloadingsaroundAlaska(Polarconsult,2009)


MAY 2012 PAGE C-10

C.3 CONCEPTUALDESIGNOFOVERHEADHVDCTRANSMISSION,RUSSTANDARDPRACTICE

Theconceptualdesignsofoverheadintertielinespresentedinthissectionhavebeendevelopedtotakeadvantageofthefollowingfactors:

● Alaskacontractors,linecrews,andutilitylinepersonnelarefamiliarwithRUSstandardpracticematerials,designs,andconstructionpractices,thustheywillbemorefamiliarwiththetechniquesandproceduresforbuilding,maintaining,andrepairingtheselines.

● AlaskaalreadyhasmanymilesofRUSstandard‐practicedistributionandtransmissionlinesbuiltandinservicethroughoutthestate.Utilitiesunderstandtheperformancerecordandissueswiththistypeoflineconstruction.

● Utilitylenders,whichincludesRUS,understandandacceptRUSstandardconstructionpractice,whichcansimplifyobtainingfundsforconstructingnewinterties.

Totakeadvantageofthesefactors,conceptualdesignforHVDCpreservedRUSstandardpracticeconstructiontotheextentpossible,modifyingthepoletopassemblytoaccommodatetheconductor(s),insulator(s),andclearancesforHVDCoperation.TherulingspanisalsoincreasedtotakeadvantageofthefewerwiresandreducedstructureloadsassociatedwiththeHVDCcircuitconfigurations.

StructuralanalysisofconventionaloverheadHVDCtransmissionstructures(adaptedfromRUSstandardpractice)wasperformedbyPolarconsult.Aconceptualdesignsummaryispresentedinthefollowingsectionsforeachlineconfiguration.

C.3.1 ConventionalACIntertieDesign

ConventionalACintertiedesignsforlow‐power(under1MW)ruralAlaskaACintertielinesareconsideredinthisstudyforthefollowingreasons:

1. ThemajorityofexistingruralAlaskaintertiesarebuiltperRUSstandardpractice.Thus,thisconventionalACoverheadlineconfigurationisthebaselineforcomparisonsofcapitalcost,electricalefficiency,andothermetricsbywhichtheHVDCintertiesystemsareevaluatedinthisreport.

2. TheRUSstandardpracticeconstructionthatisusedformostACintertielinesinruralAlaskahasbeenusedinthisreportasthebasisforconceptualdesignofconventionallybuiltHVDCintertielines.

MostruralAlaskaACintertielinesaredesignedandconstructedperRUSstandardpractice,whichtypicallyusesdirect‐burialcantileveredwoodpoles.31Manyintertielines,suchasthoseintheYukon‐Kuskokwimregion,cannotusedirect‐burialcantileveredwoodpoledesignsduetotheadversegeotechnicalconditions.Intheseproblemareas,thewoodpoleiscommonlyattachedtoasteelpiledriventoadepthofasmuchas40feettoprovideanadequatefoundationforthecantileveredpole.Thewoodpolesaretypically35to45feetinlength,dependingonthesiteconditionsandlinedesign.

ThepolessupportastandardRUStangentpole‐topassemblyaspresentedonFigureC‐1.TheconceptualdesigndataforthistypeoflineconstructionisprovidedinTableC‐1.

31 SeeRUS,1998;RUS,2005.


MAY 2012 PAGE C-11

Figure C-1 Tangent Pole for Conventional AC Intertie Line

ImageCredit:RUS,1998


MAY 2012 PAGE C-12

Table C-1 Conceptual Design Data for Conventional AC Intertie Line

I. GENERAL INFORMATION

PROJECT: CONCEPTUAL 1 MW HVDC LINESUMMARY OF CONCEPTUAL DESIGN DATA LINE IDENTIFICATION: VOLTAGE:

RUS STD. AC CONSTRUCTION 14.4 / 24.9 KV AC

THREE‐PHASE 14.4 / 24.9 Kv AC INTERTIE TYPE

STANDARD RUS CONSTRUCTION THREE PHASE AC DIST LINE < 1 MW

TYPE OF TANGENT STRUCTURE: BASE POLE:

WOOD POLE 35 FT CLASS 1

DESIGNED BY: POLARCONSULT ALASKA (CONCEPT DESIGN)

II. CONDUCTOR DATA TRANSMISSION COMMON NEUTRAL

SIZE: 1/0 (raven) 1/0 (raven)

STRANDING: 6/1 6/1

MATERIAL: ACSR ACSR

DIAMETER (IN): 0.398 0.398

WEIGHT (LBS/FT): 0.145 0.145

RATED STRENGTH (LBS): 4,380 4,380

III. DESIGN LOADS

NESC LOADING DISTRICT: HEAVY TRANSMISSION (LBS/FT) COMMON NEUTRAL (LBS/FT)

a. ICE (IN.): (vertical) 0.5 in. radial 0.5 in. radial

b. WIND ON ICED COND (PSF): (transverse) 4.0 psf 4.0 psf

c. CONSTANT K: (resultant + K) 0.3 psf 0.3 psf

EXTREME ICE (NO WIND): (vertical) 1.0 in. radial 1.0 in. radial

EXTREME WIND (NO ICE): (transverse) 120 mph 30.6 psf 120 mph 30.6 psf

EXTREME ICE + WIND:

ICE: (vertical) 0.25 in. radial 0.25 in. radial

WIND: (transverse) 80 mph 13.6 psf 80 mph 13.6 psf

IV. SAG & TENSION DATA

RULING SPAN: 250 ft.

SOURCE OF SAG/TENSION DATA: SOUTHWIRE SAG10 TRANSMISSION COMMON NEUTRAL

TENSIONS (% RATED STRENGTH) INITIAL FINAL INITIAL FINAL

NESC a. UNLOADED TEMP: 60 F lbs: 1,333 642 1,333 642

30% 15% 30% 15%

NESC b. LOADED TEMP: 0 F lbs: 2,190 2,190

50% 50%

MAXIMUM ICE TEMP: 30 F lbs: 2,488 2,488

HIGH WIND (NO ICE) TEMP: 60 F lbs: 1,875 1,875

UNLOADED LOW TEMPERATUR TEMP: ‐20 F lbs: 1,868 1,868

SAGS (FT)

NESC DISTRICT LOADED TEMP: 0 F 3.61 3.61

UNLOADED HIGH TEMP TEMP: 212 F 3.56 3.56

MAXIMUM ICE TEMP: 30 F 5.93 5.93

LOADED 1/2" ICE, NO WIND TEMP: 32 F 3.73 3.73

V. CLEARANCES

MINIMUM CLEARANCES TO BE MAINTAINED AT: EXTREME ICE LOADING

CLEARANCES IN FEET RAILROADS ROADS CULTIVATED AREAS (REMOTE AREAS) ADD'L ALLOWANCE

TRANSMISSION CLR. TO GROUND NA 21.2 21.2 5.0

VI. RIGHT OF WAY

WIDTH: 30 FT. AT EXTREME WIND, FINAL SAG, AREAS WITH TYP. STRUCTURES ADJ. TO ROW

WIDTH: 35 FT. AT EXTREME WIND, FINAL SAG, CLEARANCE TO VEGETATION AT LINE ELEV.


MAY 2012 PAGE C-13

C.3.2 MonopolarSingle‐WireTransmissionwithEarth‐ReturnPath(SWER),ConventionallyBuilt

TheRUSstandardpracticeforanAClineconstruction(FigureC‐2)canbeadaptedforamonopolarSWERHVDCline.Thenecessarychangesarelistedbelow:

● Eliminationofthefour(orthree)conductors,insulators,andthecross‐armassembly.

● Additionofasingleconductorratedforthestructuralloadsandelectricalrequirementsoftheline.Aluminumconductorsteelreinforced(ACSR)4/0Penguinwasselectedfortheconceptualdesign.

● Addasinglelinepostinsulatorratedfornominal50kVDCandthestructuralloadsfromtheconductors.A115kVACNGKpolymerlinepostinsulator(#L4‐SN321‐15U)wasselectedfortheconceptualdesign.32

● Increasetherulingspanbetweenthepolesfrom250feet(typicalforAClines)to500feet.

Atangentpole‐topassemblyforaconventionallybuiltmonopolarHVDCSWERintertieisshownonFigureC‐2.TheconceptualdesigndataforthistypeoflineconstructionisprovidedinTableC‐2.

32 TheinsulatordesignisconsideredconservativeandisanticipatedtobeadequateformostregionsofAlaska.Insulatorsrated

atalowervoltagemaybeappropriateforsomeintertielines.


MAY 2012 PAGE C-14

Figure C-2 Conventional Tangent Pole for Monopolar SWER HVDC Intertie Line


MAY 2012 PAGE C-15

Table C-2 Conceptual Design Data for Conventionally Built Monopolar SWER HVDC Intertie Line



RUS STD. AS HVDC SWER 50 KV HVDC

MONOPOLAR HVDC OVERHEAD INTERTIE, SWER CIRCUIT TYPE

STANDARD RUS CONSTRUCTION MONOPOLAR HVDC SWER





SIZE: 4/0 'PENGUIN' (NONE)

STRANDING: 6/1

MATERIAL: ACSR

DIAMETER (IN): 0.563

WEIGHT (LBS/FT): 0.291

RATED STRENGTH (LBS): 8,350

III. DESIGN LOADS


a. ICE (IN.): (vertical) 0.5 in. radial (NONE)

b. WIND ON ICED COND (PSF): (transverse) 4.0 psf

c. CONSTANT K: (resultant + K) 0.3 psf

EXTREME ICE (NO WIND): (vertical) 1.0 in. radial

EXTREME WIND (NO ICE): (transverse) 120 mph 31.1 psf

EXTREME ICE + WIND:

ICE: (vertical) 0.25 in. radial

WIND: (transverse) 80 mph 13.8 psf





NESC a. UNLOADED TEMP: 60 F lbs: 1,999 1,142 (NONE)

24% 14%

NESC b. LOADED TEMP: 0 F lbs: 4,175

50%

MAXIMUM ICE TEMP: 30 F lbs: 4,982

HIGH WIND (NO ICE) TEMP: 60 F lbs: 3,915

UNLOADED LOW TEMPERATUR TEMP: ‐20 F lbs: 3,013

SAGS (FT)

NESC DISTRICT LOADED TEMP: 0 F 9.71

UNLOADED HIGH TEMP TEMP: 212 F 11.32

MAXIMUM ICE TEMP: 30 F 14.06

LOADED 1/2" ICE, NO WIND TEMP: 32 F 10.44

V. CLEARANCES




VI. RIGHT OF WAY




MAY 2012 PAGE C-16

C.3.3 MonopolarTwo‐WireTransmissionwithMetallicConductor‐ReturnPath(TWMR),ConventionallyBuilt

ThestandardRUSdesignforanAClinecanbeadaptedforamonopolarHVDClinewithmetallicreturn.Necessaryadaptationsarelistedbelow:

● Eliminatethefour(orthree)conductors,insulators,andthecross‐armassembly.

● Increasetherulingspanfortheintertielinefromatypical250feetupto500feet.

● Addonecantileveredlinepostinsulatorratedfornominal50kVDCandthestructuralloadsfromtheconductors.115kVACNGKpolymerlinepostinsulators(#L4‐SN321‐23)wereselectedfortheconceptualdesign.

● Addoneoffsetneutralbracketforthemetallicreturnconductor.

● Addtwoconductorsratedforthestructuralloadsandelectricalrequirementsoftheline.ACSR4/0Penguinwasselectedfortheconceptualdesignforbothhigh‐voltageconductors.

Atangentpole‐topassemblyforthisconceptualdesignisshownonFigureC‐3.TheconceptualdesigndataforthistypeoflineconstructionisprovidedinTableC‐3.


MAY 2012 PAGE C-17

Figure C-3 Conventional Tangent Pole for Monopolar HVDC with Metallic Return


MAY 2012 PAGE C-18

Table C-3 Conceptual Design Data for Conventionally Built Monopolar HVDC with Metallic Return



RUS STD. AS HVDC TWMR 50 KV HVDC

MONOPOLAR HVDC INTERTIE ‐ TWMR CIRCUIT TYPE

(METALLIC RETURN) MONOPOLAR HVDC ‐ METALLIC RETURN

STANDARD RUS CONSTRUCTION TYPE OF TANGENT STRUCTURE: BASE POLE:




SIZE: 4/0 'PENGUIN' 4/0 'PENGUIN'

STRANDING: 6/1 6/1

MATERIAL: ACSR ACSR

DIAMETER (IN): 0.563 0.563

WEIGHT (LBS/FT): 0.291 0.291


III. DESIGN LOADS







EXTREME ICE + WIND:







NESC a. UNLOADED TEMP: 60 F lbs: 1,999 1,142 1,999 1,142

24% 14% 24% 14%


50% 50%




SAGS (FT)





V. CLEARANCES




VI. RIGHT OF WAY




MAY 2012 PAGE C-19

C.3.4 BipolarTwo‐WireTransmission,ConventionallyBuilt

ThestandardRUSdesignforanAClinecanbeadaptedforabipolarHVDCline.Necessaryadaptationsarelistedbelow:

● Eliminatethefour(orthree)conductors,insulators,andthecross‐armassembly.

● Increasetherulingspanfortheintertielinefromatypical250feetupto500feet.

● Addtwocantileveredpostinsulatorsratedfornominal50kVDCandthestructuralloadsfromtheconductors.A115kVACNGKpolymerlinepostinsulator(#L4‐SN321‐15U)wasselectedfortheconceptualdesign.

● Addtwoconductorsratedforthestructuralloadsandelectricalrequirementsoftheline.ACSR4/0Penguinwasselectedfortheconceptualdesignforboththehigh‐voltageandmetallic‐returnconductors.

Atangentpole‐topassemblyforthisconceptualdesignisshownonFigureC‐4.TheconceptualdesigndataforthistypeoflineconstructionisprovidedinTableC‐4.


MAY 2012 PAGE C-20

Figure C-4 Conventional Tangent Pole for Bipolar HVDC Intertie Line


MAY 2012 PAGE C-21

Table C-4 Conceptual Design Data for Conventionally Built Bipolar HVDC Intertie Line



RUS STD. AS BIPOLAR HVDC +/‐ 50 KV HVDC

BIPOLAR HVDC INTERTIE TYPE

STANDARD RUS CONSTRUCTION BIPOLAR HVDC




II. CONDUCTOR DATA TRANSMISSION + 50 kVDC TRANSMISSION ‐ 50 kVDC

SIZE: 4/0 'PENGUIN' 4/0 'PENGUIN'

STRANDING: 6/1 6/1

MATERIAL: ACSR ACSR

DIAMETER (IN): 0.563 0.563

WEIGHT (LBS/FT): 0.291 0.291


III. DESIGN LOADS

NESC LOADING DISTRICT: HEAVY TRANSMISSION (LBS/FT) TRANSMISSION (LBS/FT)






EXTREME ICE + WIND:





SOURCE OF SAG/TENSION DATA: SOUTHWIRE SAG10 TRANSMISSION TRANSMISSION



24% 14% 24% 14%


50% 50%




SAGS (FT)





V. CLEARANCES




VI. RIGHT OF WAY




MAY 2012 PAGE C-22

C.4 CONCEPTUALDESIGNOFOVERHEADHVDCTRANSMISSION,ALASKA‐SPECIFICMETHODS

TheconceptualdesignsofoverheadintertielinespresentedinthissectionhavebeendevelopedtoreduceconstructioncostsonruralAlaskainterties.Costreductionisachievedthroughspecialattentiontothefactorslistedbelow.

● Minimizingtherelianceonheavyequipmentthatmustbemobilizedtoaconstructionsite.Iflighterequipmentorlocalequipmentcanbeusedforconstruction,mobilizationcostswillbeless,reducingprojectcosts.

● Maximizingtheflexibilityinconstructionmethodsandseasons.Bydesigningfortheuseofsmallerequipment,greateruseofhelicoptersforconstructionsupport,andsimilartechniques,all‐seasonconstructionbecomespossible,creatingnewopportunitiestoincreaseutilizationofequipment,increasecompetitionforlineconstructionprojects,andreduceprojectcosts.

Thesefactorshavebeenincorporatedintotheconceptualdesignelementslistedbelow.

● Useoftallerstructuresandlongerspans.BecauseHVDCcircuitsrequireonlyoneortwowires,theycanutilizelongerspansthanacomparablethree‐orfour‐wireACcircuit.Increasingspansreducesthenumberofstructuresandfoundationsforagivenlengthofoverheadline,whichreducescosts.Withthisapproach,tallerstructuresareneededtomaintainrequiredclearancesbetweentheconductorandtheground.

● Useofglass‐fiber‐reinforcedpolymer(GFRP)polesinsteadofwoodorsteelpoles.GFRPpoleshavebeenusedforover50yearsinelectricutilityapplications33buthavelittletonohistoryinAlaska’selectricutilityindustry.GFRPpolesarelighterthanwoodorsteelpolessotheycanbetransportedbyasmallhelicoptersuchasaHughes500orBellUH‐1“Huey.”Theyarealsorot‐resistantanddonotleachtoxicpreservativesintothesoilsaroundthepole.ThePhaseIIprojectincludeddemonstrationofafield‐friendlyspliceforGFRPpoles,whichpermitstallpolestobeshippedinpartsandassembledinthefield.ThissplicecanalsobeusedforfieldrepairofdamagedGFRPpoles.

● Useofguyedstructuresinareaswheregeotechnicalconditionspreventcantileveredpolesfrombeingdirectlyburiedinthesoil.Acceptedpracticeforsuchconditionsistodriveasteelpileupto40feetdeepandthenfastenawoodpoletothesteelpile.Installingthesteelpilerequiresmobilizingacraneorotherheavyequipmenttotheprojectsite.Aguyedstructurecanbeinstalledinsuchconditionswithamuchsmallerbasefoundation,astheguyscarrymostofthemoment,andthestructurebasemostlycarriescompressiveloads.

ThefollowingsectionsdescribeconceptualdesignsusingtheseAlaska‐specificmethodsforthefollowingtypesofHVDCcircuits:

● MonopolarSWER;

● MonopolarTWMR;

● Bipolartwo‐wiretransmission.

Inallcases,theconceptualdesignspresentedinthefollowingsectionscomplywiththedesigncriteria,loadfactors,andstrengthfactorssetforthinSectionC.2ofthisappendixandbyRUS.34

33Ibrahim,2000.34 RUS,2009


MAY 2012 PAGE C-23

C.4.1 MonopolarSingle‐WireTransmissionwithEarth‐ReturnPath(SWER,Alaska‐SpecificDesign

TheAlaska‐specificconceptualdesignforamonopolarHVDClineconsistsofthefollowingelements:

● Single19#10Alumoweldconductorinstalledatarulingspanof1,000feet.

● Asinglelinepostinsulatorratedfornominal50kVDCandthestructuralloadsfromtheconductors.A115kVACNGKpolymerlinepostinsulator(#L4‐SN321‐15U)wasselectedfortheconceptualdesign.35

● A14‐inch‐diameter,0.375‐inchwall,50‐foot‐tallGFRPpole.Thispolecanbeincreasedto70feetifneededwithoutmodificationforspansupto1,500feetorforincreasedgroundorterrainclearances.

● Fourguysattachedtothepoletopinstalledata45‐degreeangletotheconductoranda45‐degreeangletoground.

● Guyanchorsconsistingoftwoflightsof8‐inchscrewanchorsdriven10to15feetintotheground.

● Apolebasefoundationconsistingofthree1½‐inchby25‐footthermoprobemicropilesinstalledtoadepthof20feet.Theremaining5feetserveasthethermoproberadiator.

Atangentpole‐topassemblyforthismonopolarHVDCSWERintertieconceptualdesignisshownonFigureC‐5.TheconceptualdesigndataforthistypeoflineconstructionisprovidedinTableC‐5.

35 TheinsulatordesignisconsideredconservativeandisanticipatedtobeadequateformostregionsofAlaska.Insulatorsrated

atalowervoltagemaybeappropriateforsomeintertielines.


MAY 2012 PAGE C-24

Figure C-5 Alaska-Specific Tangent Pole for Monopolar SWER HVDC Intertie Line


MAY 2012 PAGE C-25

Table C-5 Conceptual Design Data for Alaska-Specific Monopolar SWER HVDC Intertie Line



AK SPECIFIC HVDC SWER DES. 50 KV HVDC

MONOPOLAR HVDC OVERHEAD INTERTIE, SWER CIRCUIT TYPE

ALASKA‐SPECIFIC CONSTRUCTION MONOPOLAR HVDC SWER


GUYED FRP POLE 45 FT FRP POLE



SIZE: 19#10 ALUMOWELD (NONE)

STRANDING: 19#10

MATERIAL: ALUMOWELD

DIAMETER (IN): 0.509

WEIGHT (LBS/FT): 0.449

RATED STRENGTH (LBS): 27,190

III. DESIGN LOADS


a. ICE (IN.): (vertical) 0.5 in. radial (NONE)

b. WIND ON ICED COND (PSF): (transverse) 4.0 psf

c. CONSTANT K: (resultant + K) 0.3 psf

EXTREME ICE (NO WIND): (vertical) 1.0 in. radial

EXTREME WIND (NO ICE): (transverse) 120 mph 32.2 psf

EXTREME ICE + WIND:

ICE: (vertical) 0.25 in. radial

WIND: (transverse) 80 mph 14.3 psf


RULING SPAN: 1,000 ft.



NESC a. UNLOADED TEMP: 60 F lbs: 8,071 6,798 (NONE)

30% 25%

NESC b. LOADED TEMP: 0 F lbs: 11,246

41%

MAXIMUM ICE TEMP: 30 F lbs: 12,637

HIGH WIND (NO ICE) TEMP: 60 F lbs: 10,075

UNLOADED LOW TEMPERATUR TEMP: ‐20 F lbs: 9,736

SAGS (FT)

NESC DISTRICT LOADED TEMP: 0 F 15.97

UNLOADED HIGH TEMP TEMP: 212 F 13.73

MAXIMUM ICE TEMP: 30 F 23.85

LOADED 1/2" ICE, NO WIND TEMP: 32 F 15.02

V. CLEARANCES




VI. RIGHT OF WAY


WIDTH: 70 FT. FOOTPRINT OF 4‐GUYED STRUCTURE, GUYS AT 45 DEGREES TO LINE

WIDTH: 95 FT. FOOTPRINT OF 4‐GUYED STRUCTURE, GUYS IN LINE AND NORMAL TO CONDUCTOR.



MAY 2012 PAGE C-26

C.4.2 MonopolarTwo‐WireTransmissionwithMetallicConductor‐ReturnPath(TWMR),Alaska‐SpecificDesign

TheAlaska‐specificconceptualdesignforamonopolarHVDCline(FigureC‐6)canbeadaptedforatwo‐wiremonopolarHVDClinewithmetallicreturn.Thenecessarychangesarelistedbelow:

● IncreasetheGFRPpoleheightfrom50feetto65feet.NochangeisneededinthepolesectionormaterialundertheloadcaseslistedinSectionC.2.

● Additionofasecond19#10Alumoweldconductorsupportedbyanoffsetbracket15feetbelowthetopofthepole.Atthisattachmentpoint,thissecondconductorwillhaveadequateclearancefromtheguys,ground,andthehigh‐voltageconductorunderallloadconditionslistedinSectionC.2ofthisappendix.

● Maintaintherulingspanat1,000feet.

Atangentpole‐topassemblyforaconventionallybuilttwo‐wiremonopolarHVDCintertieisshownonFigureC‐6.TheconceptualdesigndataforthistypeoflineconstructionisprovidedinTableC‐6.


MAY 2012 PAGE C-27

Figure C-6 Alaska-Specific Tangent Pole for Monopolar Metallic-Return Intertie Line


MAY 2012 PAGE C-28

Table C-6 Conceptual Design Data for Alaska-Specific Monopolar Metallic-Return Intertie Line




MONOPOLAR HVDC OVERHEAD INTERTIE TMWR CIRCUIT TYPE

(METALLIC RETURN) MONOPOLAR HVDC WITH METALLIC RETURN

ALASKA‐SPECIFIC CONSTRUCTION TYPE OF TANGENT STRUCTURE: BASE POLE:




SIZE: 19#10 ALUMOWELD 19#10 ALUMOWELD

STRANDING: 19#10 19#10

MATERIAL: ALUMOWELD ALUMOWELD

DIAMETER (IN): 0.509 0.509

WEIGHT (LBS/FT): 0.449 0.449


III. DESIGN LOADS







EXTREME ICE + WIND:








30% 25% 30% 25%


41% 41%




SAGS (FT)





V. CLEARANCES




VI. RIGHT OF WAY

WIDTH: 60 FT. FOR EXTREME WIND, FINAL SAG, AREAS WITH TYP. STRUCTURES ADJ. TO ROW



WIDTH: 60 FT. FOR EXTREME WIND, FINAL SAG, CLEARANCE TO VEGETATION AT LINE ELEV.


MAY 2012 PAGE C-29

C.4.3 BipolarHVDCIntertieLine,AlaskaSpecificDesign

TheAlaska‐specificconceptualdesignforamonopolarHVDCline(FigureC‐7)canbeadaptedforatwo‐wirebipolarHVDCline.Thenecessarychangesarelistedbelow:

● IncreasetheGFRPpoleheightfrom50feetto55feet.Nochangeisneededinthepolesectionormaterial.

● Eliminatethepost‐topinsulatorandaddtwo8‐foot‐longcross‐arms.APowertrusion#SH2096100Norequalwasselectedfortheconceptualdesign.

● Installtwosuspensioninsulatorsoffeachendofthecross‐arm.A115‐kVACNGKsuspensioninsulator#251‐SE510‐EEorequalwasselectedfortheconceptualdesign.

● Use19#10Alumoweldastheconductorforboththepositiveandnegativepolesofthecircuit.

● Maintainthesamespanlengthof1,000feet.

Atangentpole‐topassemblyforanAlaska‐specificbipolartwo‐wireHVDCintertieisshownonFigureC‐7.TheconceptualdesigndataforthistypeoflineconstructionisprovidedinTableC‐7.


MAY 2012 PAGE C-30

Figure C-7 Alaska-Specific Tangent Pole for Bipolar HVDC Intertie Line


MAY 2012 PAGE C-31

Table C-7 Conceptual Design Data for Alaska-Specific Bipolar HVDC Intertie Line




BIPOLAR HVDC INTERTIE TYPE

ALASKA‐SPECIFIC CONSTRUCTION BIPOLAR HVDC





SIZE: 19#10 ALUMOWELD 19#10 ALUMOWELD

STRANDING: 19#10 19#10

MATERIAL: ALUMOWELD ALUMOWELD

DIAMETER (IN): 0.509 0.509

WEIGHT (LBS/FT): 0.449 0.449


III. DESIGN LOADS







EXTREME ICE + WIND:








30% 25% 30% 25%


41% 41%




SAGS (FT)





V. CLEARANCES




VI. RIGHT OF WAY

WIDTH: 60 FT. FOR EXTREME WIND, FINAL SAG, AREAS WITH TYP. STRUCTURES ADJ. TO ROW



WIDTH: 55 FT. FOR EXTREME WIND, FINAL SAG, CLEARANCE TO VEGETATION AT LINE ELEV.


MAY 2012 PAGE C-32

C.4.4 ConceptualDesignAnalysis

Theconceptualdesignofoverheadtransmissionstructuresandfoundationsconsideredmethodsforconstruction,long‐termoperation,maintenance,repair,andreplacementoftheHVDCtransmissioninfrastructure.

C.4.4.1 ConstructionMethods

Thecost‐reductionpotentialofHVDConruralAlaskaprojectsmayberealizedusingoptimizedconstructionmethods.

Theuseoflightweightoverheadstructuresandfoundationsallowssignificantlatitudefortheconstructionandmaintenanceofthelines.Theuseofhelicopterstostagethematerialsandconstructionequipmentbecomespossible.

ConventionalACtransmissionlineconstructionistypicallyperformedinthewintertosupporttheheavyequipmentrequiredforconstruction.Thisequipmentoftenincludeslargepile‐drivingordrillingmachinesthatcanonlybeoperatedonfrozenground.Theresultingwinterconstructionschedule,combinedwithsummermobilizationoftheequipment,contributessignificantlytothehighcostofACinterties.

ACtransmissionstructuresandfoundationsareusuallybasedonacantileverpoledesign.Forthelow‐strengthgeotechnicalconditionsfoundinmuchofruralAlaska,thisdesignapproachisinefficientcomparedtotheuseofaxiallyloadedguyedstructuresproposedintheHVDCconceptualdesign.

TheHVDCconstructionapproachcanutilizeHughes500orBellUH‐1typehelicopters,whicharecommonlyavailableinAlaska.Thesehelicoptershaveaslingcapacityofapproximately1,000and3,000pounds,respectively.TheHVDCcompositepolestructures,guywires,screwfoundations,thermoprobefoundations,andothertransmissioncomponentscanbereadilystagedbythesehelicopters.Installationequipmentandotherconstructiontoolsareavailableinsizesthatcanbeliftedbyhelicopter.

Inaddition,thisconstructionapproachinvolvestheuseoftracked,low‐ground‐pressurevehicleswithattachmentsoptimizedfortheinstallationoftheHVDCfoundationsanderectionofthecompositepolestructures.TheidealvehiclewouldbesimilartoahydraulicallydrivenBBCarrier.TheBBCarrierwasapredecessorofNodwelltrackedvehicles,butmuchsmaller36.Thehydraulicdrivesystemcanbeusedtopowerdrills,winches,spades,impactdrivers,andotheronboardequipmentusedforlineconstruction37.

C.4.4.2 RecommendedConstructionApproach

ThefollowingnarrativesetsforththegeneralconstructionapproachrecommendedfortheconceptualoverheadHVDCintertiedesignpresentedherein.Preferredconstructionmethodsforanyspecificintertiewilldifferfromthisapproachandwillaffectconstructioncosts.

1. Identifyandprocurepropertyrightstotheintertiealignment.Standardpracticesforthiseffortareappropriateandarenotduplicatedhere.

36 TheBBCarrierwasmanufacturedinthelate1950sandearly1960sbyBombardier.Itisnolongerinproductionandisquite

raretoday.Itfeaturedagrossvehicleweightofabout2,000pounds,apayloadcapacityofabout1,000pounds,andagroundpressureoflessthanonepsi.Itsdrivetrainusedaplanetarytransmission,maintainingpowertobothtracksduringturns,whichreducedthetendencyofthesevehiclestodamagefragiletundravegetation.

37 A20,000to30,000‐ft‐lbhydraulicimpactdriverheadonasmallboomwouldbeusefulfordrivingfoundationscrewanchors.


MAY 2012 PAGE C-33

2. Sendanengineeringcrewandsurveypartytosurveythelineanddeterminepolelocationsinthefield.Surveyingandpreliminarylinedesignmaybecompletedbeforehandbyremotemethods(e.g.,lightdetectionandranging[LIDAR]survey).Theengineeringcrewwillconductgeotechnicaltestingateachpolesitetodeterminethetypeoffoundationrequired.Asappropriate,theengineeringcrewmayadjustpolelocationsbasedonencounteredconditions.

3. Orderandshipmaterialstotheprojectsite.Dependingontheproject,oneorbothvillageswillbeusedasthebaseofoperations.Itmaybecost‐effectivetopreassemblepoleorfoundationunitspriortoshippingtothesite.

4. Prepareandinstallpolefoundations.Dependingontheproject,polefoundationsmaybeshippedreadytoinstallormayrequiresomeassemblyinthevillage.Oncereadytodeploytothefield,thefoundationsforeachpole(polebaseandthreeguyfoundations)willbeairliftedtothepolesitebyhelicopter.Asmalllow‐ground‐pressurevehiclewillbeusedtoinstallthefoundations.Dependingontheterrain,thisstagemayoccurduringthelatewinterorsummermonths.Thegroundvehiclewillremaininthefield,andpersonnelandconsumableswillbetransportedtothevehicledailybyair.Thiswillreducetransittimes.

5. Prepareandassemblepoles.Thiswilloccurinoneorbothvillagesandmayincludesplicingthepoles,attachingthepoletopandbasehardware,attachingthepostinsulatorandstringingblocks,andattachingtheguywiresandhardware.Anassembledpolewillbepackagedinamannersuitableforairliftandclearlylabeledsoitisdeployedtotheproperfoundation.

6. Poleinstallation.Eachassembledpolewillbeairliftedbyhelicoptertothepole'sfoundation.Thepolewillbespottedonthegroundbythehelicopterandagroundcrew.ThegroundcrewwilluseanA‐frameandtheirsmall,low‐ground‐pressurevehicletoerectthepoleusingtwooftheguyanchorsashoistpoints.Alternatively,thehelicoptercouldbeusedforfastererectingandsecuringofthepole.Oncethepoleiserected,plumbed,andguystensioned,thecrewwilldrivetothenextfoundationsite.Dependingonhelicopterlogistics,itmaybecost‐effectivetoemploytwogroundcrewsforthisactivity.Groundcrewsandconsumableswillbemobilizedtothelinedailybyhelicopter.

7. Stringingandsettingtheconductor.Thestringinglinewillbedeployedbyhelicopter.Onceinplace,theconductorwillbestagedbyhelicopteranddeployedbygroundcrews.AHughes‐500canliftapproximately2,000feetofconductoratatime.Oncetheconductorisstrung,groundcrewswillascendeachpoletoset,tension,andfixtheconductor.Armorwrapandvibrationdamperswillbeinstalledatthistime.

C.4.5 MaintenanceMethods

Thissectiondiscussestheconceptualmaintenanceandrepairmethodsthatareappropriateforthelong‐span,tall‐poleHVDCSWERoverheadintertie.Whilesometopicsmaybegenerallyapplicabletothemaintenanceandrepairofoverheadinterties,thisdiscussionfocusesonandisspecifictothisparticularintertiedesignconcept.

Fiberglasspolescannotbeclimbedusingthespur‐and‐beltmethodcommonlyemployedtoclimbwoodpoles.Instead,apulleyandcableorropesystemwouldbeanintegralpartofthefiberglasspole.Thepulleywouldbeinstalledinthepoletop,andthecablewouldtraveldownthepoleinterior.Thelinecrewisenvisionedtouseaharnessandwinchapparatustoattachtothepoleapparatusandusethissystemtoliftalinemantothepoletopformaintenance.


MAY 2012 PAGE C-34

Thisapproachoffersseveraladvantagescomparedwithconventionalpoleclimbingmethods.

● Theequipmentandinherentsafetyoftheapproachenableslessexperiencedcrewstoascendthepoles.

● Pole‐topmaintenanceiseasierorpossibleduringcolderweatheroradverseconditions.

● Ascent,descent,andtop‐siteworkisfasterbecausethecrewisnotasfatigued.

● Workislessphysicallydemanding,reducingthelikelihoodoffatigue‐relatedaccidents.


MAY 2012 PAGE C-35

C.5 CONCEPTUALDESIGNANALYSIS

Themajorityofthedesignanalysisfortheoverheadtransmissionconceptspresentedinthisstudyfollowsestablisheddesignpracticesthatarefoundinindustryliterature.38ThissectiondiscussesspecificaspectsoftheconceptualdesignofHVDCsystemsthatareuniquetoAlaskaandwarrantmoredetaileddiscussion.

C.5.1 StructuralDesign

PolarconsultcontractedwithLineDesignEngineering,Inc.(LDE)forassistanceinthestructuralandcodeanalysisofAlaska‐specificoverheadHVDCtransmissionstructuredesignconcepts.

C.5.2 FoundationDesign

PolarconsulttaskedGolderwithdevelopingconceptualfoundationdesignsfortherepresentativesoilsandgeotechnicalconditionsdiscussedinthisreport.Golderproposedthreefoundationdesignconceptsthatprovideeconomicalfoundationoptionsforsupportingguyedpowerpolesintherepresentativegeotechnicalconditions.Thesearesummarizedbelow.

● Passivelycooledthermoprobemicropiles,installedunderthepoletoreceivecompressiveloads.ArcticFoundations,Inc.(AFI)wasidentifiedasanexperiencedmanufacturerofsuchfoundationsystems.

● Small‐diameterhelicalanchors,installedunderthepoletoreceivecompressiveloadsorinstalledattheguystoreceivetensionloads.Thermopilescouldbeinstalledadjacenttotheseanchorstodecreasetemperaturesinthebearingsoils,whichwillincreasetheanchorstrength.

● Smaller‐diameter(4‐to6‐inch)verticalpilesforbothpolesandguys,installedwithimpacthammersusingsmallertrackedrigs.Thermopilescouldbeinstalledadjacenttotheseanchorstodecreasetemperaturesinthebearingsoilsandincreasepilestrength.

Existingconventionalfoundationmethodsweremaintainedforconventionalintertielineconstruction.Thisconsistsofeitherdirectburialofawoodpoleinsuitablesoilsorfasteningawoodpoletoadrivensteelpileinthemoredifficultgeotechnicalconditions.

Forguyedpowerpoles,asetofthree1½‐inch‐diameterthermoprobemicropilesinstalledtoadepthof20feetwitha5‐footradiatorsectionabovegroundareusedastheconceptualdesignforthepolebase,andhelicalanchorsareusedastheconceptualdesignforthepoleguys.

C.5.3 AnalysisofThermoprobePerformance

PolarconsultcontractedwithZarlingAeroEngineers(ZAE)tomodeltheseasonalthermalperformanceofapassivecoolingelementsuchasathermoprobemicropile.ZAEmodeledawarmpermafrostconditionanalogoustoGolder’sgeotechnicalProfile“C”usingthickandthinorganiclayersandcurrentclimatedataformarginalpermafrostintheFairbanksarea.Thermoprobeswiththermalconductancesof1.0Britishthermalunit(Btu)/hr‐ft‐°Fand2.0Btu/hr‐ft‐°Fwereconsidered.39ZAEalsoevaluatedtheeffectofplacinga4‐inch‐thicklayerofrigidinsulationonthegroundsurfacewithin4feetofthethermoprobe.

38RepresentativepublicationsincludeRUS,2001;RUS,2003a;RUS,2009;Naidu,1996;KZK,2006;Skrotzki,1980;Southwire,2008;andThrash,2007.39The1.5‐inch‐diameter,25‐foot‐longthermoprobesinstalledattheFairbanksTestSite(seeSectionC.6ofthisappendix)haveanestimatedthermalconductanceof0.3Btu/hr‐ft‐°F(AFI,2011).


MAY 2012 PAGE C-36

ZAErepeatedthisanalysiswithwarmerclimateconditionstoforecasttheperformanceofthethermoprobesunderawarmingclimateinthe2060to2069decade.TheresultsoftheseanalysesaresummarizedinTableC‐8.ZAE’stechnicalanalysisandreportisincludedasAttachmentC‐1tothisappendix.

TableC‐8presentsthefollowingmodelresultsthatdirectlypertaintothestructuralperformanceofthethermoprobes:

1. Maximumdepthoftheactivelayer(occursinlatefall).Thisdefineshowmuchoftheupperportionofthethermoprobeisinthawed,structurallyweaksoilsthatprovidedlimitedlateralsupporttothethermopile.Forstructuralanalysis,thisportionofthethermoprobeisassumedtobeanunsupportedcolumnthatmustbestiffenoughtotransfercompressiveloadsfromthetopofthethermoprobedowntothepermafrostregionwithoutbuckling.

2. Averagemaximumtemperatureofthepermafrost1footfromthethermopileinearlyfall(maximumannualtemperature).Thisdefinestheminimumstrengthofthesoilaroundthethermoprobeandthebearingstrengthofthethermopiletoresistbothcompressiveandtensionloads.

TheresultsofZAE’sanalysis(TableC‐8)areexplainedbelow.Itisimportanttoemphasizethattheseresultsarespecifictothesoilparameters,thermoprobeperformance,andclimateconditionsmodeled.Othermodelinputsmayproducesignificantlydifferentresults.

1. Underthegeotechnicalconditionsmodeled,a4‐inchlayerofrigidfoaminsulationinstalledatthesurfaceandextendingradiallyoutfromthethermoprobefor4feetcanreducethemaximumdepthoftheactivelayerby1to2feet.Duetothemodeststructuralbenefit,expectedcost,anddifficultyofinstallingandmaintainingsuchaninsulationassembly,thisinsulationelementisnotincludedintheconceptualfoundationdesigns.

2. Underallgeotechnicalconditionsmodeled,thethermoprobelowersthesoiltemperatureimmediatelysurroundingthethermoprobethroughouttheyear.Thiseffectismostpronouncedduringthewintermonthswhenthethermoprobeisextractingheatfromthesoilandcoolsthesoilbyupto5°Fsurroundingthethermoprobe.Thiscoldbulbpersiststhroughthesummer,resultinginanend‐of‐summerresidualthermalanomalyofafew1/10ths°Finthesoilsurroundingthethermoprobe.Thisresultsignificantlyenhancesthecompressiveandtensioncapacityofthethermoprobeduringthewinterandspringmonthsandproducesalesser(anddecreasing)enhancementthroughthesummerandintofall.Thethermoprobeimmediatelystartscoolingthesurroundingsoilsuponthereturnoffreezingnighttimeconditionsinthelatefall.


MAY 2012 PAGE C-37

Table C-8 Summary of Results from Thermoprobe Modeling by ZAE

Thermoprobeconductance=1.0Btu/hr‐ft‐°F Thermoprobeconductance=2.0Btu/hr‐ft‐°F ThinOrganicLayer ThickOrganicLayer ThinOrganicLayer ThickOrganicLayer

ExistingClimateConditions (Fairbanks,1971–2000)

4”SurfaceInsulation

NoSurfaceInsulation


NoSurfaceInsulation


NoSurfaceInsulation


NoSurfaceInsulation

Maximumdepthofactivelayerwithoutthermoprobe(atthermoprobe)1 6.5feet 3feet 6.5feet 3feet

Maximumdepthofactivelayerwiththermoprobe(atthermoprobe) 5.1feet 6.5feet <1foot 3feet 5feet 6.0feet <1foot 3feet

Averageearlywintersoiltemperatureonefootfromthermoprobe 30°F 30°F 30°F 30°F 28°F 28°F 28°F 28°F

Endofsummer/earlyfalltemperaturesonefootfromthermoprobe 30‐35°F 30‐35°F 30‐32°F 30‐34°F 30‐35°F 30‐35°F 29‐33°F 29‐34°F

Projected2060‐2069ClimateConditionsforFairbanks(+2.7°Fincreaseinannualmeantemperature)

Maximumdepthofactivelayerwithoutthermoprobe(atthermoprobe)1 8feet 8feet 3.5feet 3.5feet NA NA NA NA

Maximumdepthofactivelayerwiththermoprobe(atthermoprobe) 6.5feet 7.5feet 1foot 3.5feet NA NA NA NA

Averageearlywintersoiltemperatureonefootfromthermoprobe 31°F 31°F 31.5°F 31.5°F NA NA NA NA

Endofsummer/earlyfalltemperaturesonefootfromthermoprobe 31‐37°F 31‐37°F 31‐34°F 31‐35°F NA NA NA NA

SeethefullZAEreport,AttachmentC‐1tothisappendix,formoredetailedinformation. 1 Temperatureat11feetfromthermoprobe,whichisthelimitofthemodelgraphicsinthereport.NA: Notanalyzed.


MAY 2012 PAGE C-38

C.5.3.1 ThermoprobeConceptualDesign

AFIdevelopedconceptualthermopiledesignsbasedonthestructuralloadsgivenfortheAlaska‐specificintertiestructures.ThedesignandfabricationsheetsfortheAFIthermopileareincludedasAttachmentC‐2.

Polefoundationsusingeitherasingle3‐inchthermopileorasetofthree1½‐inchthermopilesarebothpractical.1½‐inchthermopilescanbeinstalledbysmallerequipmentthana3‐inchpile,althoughthematerialcostandinstallationtimewillbothbesomewhathigherthanforasingle3‐inchthermopile.Onsomeprojects,theuseofsmallerequipmentisexpectedtoresultinsufficientsavingsinspiteoftheincreasedmaterialandlaborcosts.

FiguresC‐9throughC‐11presenttheadapterplatedevelopedtomateaGFRPpoletothree1½‐inchthermopiles.FigureC‐8belowshowstheprototypeinstallationofthispolefoundationdesigninstalledatthefoundationtestsiteinFairbanks.TheFairbankstestingisdescribedingreaterdetailinSectionC.6ofthisappendix.

Figure C-8 Prototype Micro-Thermopile Tripod Pole Foundation

Fairbanks,Alaska.Polarconsult,2011

FINALREPORT,VERSION1.1 POLARCONSULTALASKA,INC.HVDCTRANSMISSIONSYSTEMFORRURALALASKANAPPLICATIONSPHASEII–PROTOTYPINGANDTESTING

MAY 2012 PAGE C-39

Figure C-9 Shop Drawing of Prototype GFRP Pole Base Adapter for Micro-Thermopile Foundation (Sheet 1 of 3)


MAY 2012 PAGE C-40



MAY 2012 PAGE C-41



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MAY 2012 PAGE C-43

C.5.3.2 ScrewAnchorConceptualDesign

BasedontheconceptualdesignanalysispreparedbyGolder,screwanchorsfittedwithtwoflightsof8‐inchhelicesanddriventoadepthof10to15feetbelowthegroundsurfacewillbesuitableforanchoringmostguys.IntheconceptualsoilspresentedbyGolder,theseanchorscanbeinstalledwithatorqueof10,000to15,000foot‐pounds.Guysatanglestructuresordeadendsmayrequiretwoormoreanchors.RepresentativescrewanchorsareshownonFigureC‐12.

Figure C-12 Galvanized Screw Anchors with 8-Inch Flights

Palletofgalvanizedscrewanchorswith8‐inchflights.SimilaranchorsaresuitableforrestrainingguysforAlaska‐specifictransmissionstructuresinmanychallengingsoils.(Polarconsult,2011;PhotographcourtesyofAlaska

FoundationTechnology,Inc.)


MAY 2012 PAGE C-44

C.5.4 ElectricalDesign

C.5.4.1 Conductor

A1‐MWtransmissioncapacityat50kVDCequatestoanominalpeakampacityof20amperes.Overloadorfaultconditionsarehigher.TheeconomicallyallowableconductorlossesontheHVDClineweresetat3%lossesat100%nominalcapacity.Fora25‐mile,1‐MW,two‐wiremonopolarintertie,thisisapproximatelyequivalentto1.5ohmsperconductor‐mile.TherequiredconductorresistanceisthesameforamonopolarSWERtransmissioncircuit,providedthatthegroundinggridsandearthreturnpathwayhaveatotalresistanceequaltoorlessthan37.5ohms.

Thestructuralrequirementsoftheconductorarepartofalargertechnicalandeconomicanalysisoftheoverheadsystemdesign.ForruralAlaskaintertielines,longerspansandfewerfoundationswillgenerallyresultinloweroverallcapitalcosts.Thisdesigndecisioncallsforstrongerconductorstowithstandthehigherstressesfromenvironmentalloadsandtallerpolestomaintaingroundclearancesundermaximumsagconditions.

ForconventionallybuiltHVDCintertiedesignconcepts,thesedesignconsiderationsresultedintheselectionofa4/0ACSRPenguinconductorforallHVDCcircuitconfigurations.

ForAlaska‐specificHVDCintertiedesignconcepts,thesedesignconsiderationsresultedintheselectionofa19#10AlumoweldconductorforallHVDCcircuitconfigurations.

C.5.4.2 Insulators

InsulatorsinDCapplicationsaremoresusceptiblethanACinsulatorstotheaccumulationofcontaminationontheinsulatorsheds.Thisisduetothepresenceofastaticelectricfieldaroundthehigh‐voltageconductor,whichattractschargedparticlestowardtheconductor.ThisattractionofchargedparticlesresultsinmoreparticleslandingonandcontaminatingtheinsulatorthanoccursoncomparableACsystems.ThisisbecausethealternatingelectricfieldaroundanACconductordoesnotimpartanetattractiontochargedparticles.

Periodicrainsandotherweathereventscandislodgetheseparticlesfromtheinsulatorsheds.Variousspecialcoatingscanalsohelptorepelparticles.Iftheinsulatorprovidesasufficientlylongleakagepathtoaccommodatetheaccumulatedcontamination,thennoactionisrequired.Insomeclimates,itisnecessarytowashtheinsulatorsperiodically.Thiscanbedonefromsuitablyequippedhelicoptersorlinetrucks.

OnmostruralAlaskaintertielines,washinginsulatorswouldbecostprohibitive,andwhenpossible,theinsulatorsshouldbedesignedtowithstandlong‐termaccumulationofcontamination.DesignguidanceforHVDCinsulatorsindicatethatinsulatorsratedfor34.5to42kVACserviceareadequatefor50kVDC,dependingonthedegreeofenvironmentalcontaminationandself‐cleaningconditionsthatexistalongtheintertieroute.40

DuetothewiderangeofenvironmentalconditionspresentinAlaska,averyconservativeconceptualinsulatordesignhasbeenadoptedtoprovideasubstantialallowanceforinsulatorcontamination.Indiscussionswithinsulatormanufacturers,insulatorsratedfor115kVAChavebeenselectedfortheconceptualdesign.Thisprovidesaleakagepathlengththatismorethan2.7timesthepublishedguidanceforHVDCtransmissioninsulators.Specificprojectsmaybeabletorealizesomecostsavingsbyusing

40Arrillaga,1998.Page256‐257.


MAY 2012 PAGE C-45

lower‐voltageinsulatorsiftheyaredistantfromcoastalregions(saltspray),activerivers(blowingdust),glaciers(blowingdust),aridregions(lackofcleansingrains),andsimilargeographicorclimaticcharacteristics.

MostHVDClinesarebipolarsystemswithtwohigh‐voltageconductors(FigureC‐13).Atypicaleconomicdesignsolutionforatwo‐conductoroverheadintertielineusessuspensioninsulators.InamonopolarSWERoverheadsystem,themosteconomicaldesigncallsforalinepostinsulatoratopasinglestructure.

Figure C-13 Typical Bipolar HVDC Transmission Line Using Suspension Insulators

HVDCcrossover,NorthDakota.Source:http://upload.wikimedia.org/wikipedia/commons/b/ba/HVDC_Crossover_North‐Dakota.jpg.

Atthespans,voltages,andenvironmentalloadsconsideredforthisapplication,acompositelinepostwitha3.5‐inch‐diameterpultrudedfiberglasscoreandsiliconeshedsarenecessarytowithstandthevertical,lateral,andlongitudinalmechanicalloadsplacedontheinsulator.Aninsulatorsuchaspartno.L4‐SN321‐15UmanufacturedbyNGK,Inc.orsimilarproductsaresuitableforthisapplication.Certainloadconditions,suchasunbalancedsheddingof1‐inchradialiceona1,000‐footspan,exceedtheratedstructuralcapacityofthisinsulator.


MAY 2012 PAGE C-46

Forspecificprojects,thislimitationcanbeaddressedinseveralways(e.g.,lessstringentdesignloads,reducedinsulatormargin,shorterspans,etc.).Manufacturersaredevelopingstrongerlinepostinsulators(4.0‐and4.5‐inchcores)thatwillbeadequateforallloadcombinationsconsideredinthisstudy.Itisestimatedthatthesewillbecommerciallyavailableby2014orthereafter.

Alternateinsulatorconfigurationscanalsobeusedtocircumventthestructurallimitationsofexistinglinepostinsulators.FiguresC‐14throughC‐16presenttwopotentialinsulatorconfigurationsthatusesuspensioninsulatorstoreducetheloadingsonalinepostinsulator.Theseconfigurationscanbeadaptedforuseonanyoftheconceptualoverheaddesignspresentedinthisappendix.Suspensioninsulatorsarelesscostlythanthelinepostinsulators;however,thesemorecomplicatedassemblieswillrequiremorelabortoinstall.

Figure C-14 Typical Tangent Structure Using Post Insulators

CantileveredwoodpoletangentstructureforanACtransmissionline.Postinsulatorsareusedtocarryallthree‐phaseconductors.Thepost‐topinsulatorcarrieslongitudinalandlateralforcesinbending,andthetwosideinsulatorscarryverticalandlongitudinalforcesinbending.TheseapplicationsaresimilartothoseshownonFigureC‐3andFigureC‐4.


MAY 2012 PAGE C-47

Figure C-15 Typical Angle Structure Using Suspension and Post Insulators

GuyedsteelpoleanglestructureforanACtransmissionline.Suspensioninsulatorsareusedtocarrytheconductortension,andapostinsulatorisusedtoholdtheconductoroffofthesupportstructure.Availablepostinsulatorsarenotstrongenoughtobeusedasapost‐topinsulator(asonFigureC‐4orC‐14)inthistypeofapplication.(Polarconsult,

2012)


MAY 2012 PAGE C-48

Figure C-16 Typical Tangent Structure Using Suspension and Post Insulators

Cantileveredwoodpoletangentstructurefora115kVACtransmissionline.Notetheuseofasuspensioninsulatorintensionandpostinsulatorincompressiontocarrytheweightoftheconductor.Thebaseofthepostinsulatorishingedtoallowsomelongitudinalmovementoftheconductor.Thepostinsulatoralsocarriesmostofthelateralwindloadsontheconductor.Thisinsulatorconfigurationcanbeusedforsingle‐ordouble‐wireHVDCcircuitconfigurations.Aback

guycouldbeusedtoreducethenetmomentonthepoleandfoundation.(Polarconsult,2012)


MAY 2012 PAGE C-49

C.6 TESTINGOFOVERHEADDESIGNCONCEPTS

Mostelementsoftheconceptualoverheaddesignsdescribedinthisappendixutilizecommerciallyavailableandacceptedmaterials,designs,andconstructionmethods.CertaincomponentsoftheconceptualdesignspresentedinSectionC.5representinnovationsinoverheadlinedesignthatdonothaveaprovenrecordwithintheutilityindustry.Inordertoevaluatetheperformanceofthesecomponents,theywereinstalledatatestsiteinFairbanks,Alaska.ThissectiondescribestheobjectivesandinstallationoftheFairbanksTestSite.

C.6.1 TestObjectives

TheprimarytestobjectivesoftheFairbanksTestSitearelistedbelow.

1. Demonstrateperformanceandassemblytimeofaspliceforaconstant‐sectionGFRPutilitypole.

2. Demonstrateinstallationandperformanceofmicro‐thermopilepolefoundations.

3. Demonstrateinstallationandperformanceofmicro‐thermopileguyanchors.

4. Demonstrateinstallationandperformanceofscrewguyanchors.

5. DemonstratetheinstallationandperformanceoftheoverallguyedGFRPpolestructure.

C.6.2 TestSite

ThetestsiteislocatedonprivatepropertyoffFarmer’sLoopRoadnorthofCreamers’FieldinFairbanks.Thesiteconsistsofwarmice‐richsiltypermafrostsoils.Thesitehasanorganiclayerconsistingofdeciduousshrubsandblackspruce.Peatwaspresentatdepthsof1to5feetbelowgroundsurface.TheactivelayerinSeptemberextendedtoadepthof3feet,withstandingwaterencounteredwithinthevegetativematnearthesurface.

Geotechnicalconditionsatthesitearecharacteristicofmarginalwarmpermafrostconditions,generallyconsistentwithconceptualgeotechnicalprofile“C”developedbyGolderanddescribedinSectionCofthisappendix.

C.6.3 Installation

Keyitemsinstalledatthetestsitearedescribedinthissection.

C.6.3.1 SoilTemperatureProbes

Thesitehastwosoiltemperaturemonitoringprobes.Eachprobeisa¾‐inchPVCpipeinsertedintoadrillholethatextendsto25feetbelowgrade.Oneholeislocatedadjacent(1.0footaway)tothemicro‐thermopiletripodpolefoundationandwillbeusedtomonitorthethermaleffectsofthethermopilesandvegetationclearing.Thesecondholeislocatedapproximately50feetawayinanundisturbedblacksprucestandandwillbeusedtocollectbaselinesoiltemperaturedata.

C.6.3.2 Glass‐Fiber‐ReinforcedPolymer(GFRP)Pole

Thesitehasone60‐foot‐tallguyedglass‐fiber‐reinforcedpolymer(GFRP)pole.TheGFRPpolehasaroundsection,is12inchesindiameter,andhasa0.5‐inchwall.TheGFRPpoleismanufacturedbyPowertrusions,Inc.TheGFRPpoleconsistsofa40‐footand20‐footsectionconnectedbyafullmoment‐carryingslip‐onexternalsplice.Thesplicedoesnotrequireanyglueorsolventtodevelopbearingormomentcapacity.Bearingiscarriedbyphysicalcontactofthebutt‐endsofthepolesegments.Momentis


MAY 2012 PAGE C-50

carriedthroughmechanicalcontactbetweenthepoleandsplicewalls.Thespliceisheldinplaceby#14¼‐inch‐diameterx1½‐inch‐longzincplatedTekshexwasherheadscrewsdrivenaroundtheperimeterofthespliceintoeachpolesegment.ThepoleattheFairbankssiteisincompression.Powerlinepolessubjecttoupliftwouldneedtodesignthespliceconnectionfortensionloads.

C.6.3.3 GFRPPoleFoundation

TheGFRPpolefoundationisamicro‐thermopiletripodwithanadapterpiecetofitthepoleontothemicro‐thermopiles.ShopdrawingsoftheadapterpiecearepresentedonFigureC‐9throughC‐11.Theadapterpiece:

● Featuresanintegralhingeassemblytoraiseorlowerpolesinthefield,

● Providesgeneroustolerancesforbatteranglesandplacementofthemicro‐thermopiles,and

● Providesfullflexibilityinorientationofthehingeanglerelativetothetripodangle(sothepolecanberaisedorloweredinlinewithaguyanchorregardlessofhowthepolefoundationmicro‐thermopilesareoriented.

C.6.3.4 Guys

TheGFRPpoleissecuredbyfour3/8‐inchextra‐high‐strength(EHS)guylinessetat90degreestoeachotherand45degreestoground.Theguysandguyhardwareisconventional.AFUTEKmodelLSB4000loadcellisriggedintooneguywireoneachaxistomeasureguywiretension.

C.6.3.5 GuyAnchors

FourdifferentguyanchorsareinstalledattheFairbankssite.

1. A25‐foot‐longby1½‐inch‐diametermicro‐thermopile,installedata45‐degreeangletothegroundsurface(directlyin‐linewiththeguy).Thisanchorresistsguytensionsolelywithskinfriction.Theanchorisinstalledwiththetop5feetabovegroundastheradiatorsection.

2. A25‐foot‐longby1½‐inch‐diametermicro‐thermopile,installedata70‐degreeangletothegroundsurface.Thisreducedanglefromverticaliseasiertoinstallbutplacesamomentonthemicro‐thermopile.

3. Astandard8‐inchdouble‐flightscrewanchor.Thescrewanchorwasdriven15feetbelowgroundsurfaceata45‐degreeangle,placingtheanchorflightsapproximately10feetbelowgrade.

4. Astandard6‐inchswampanchor.Theswampanchorisscrewedintothesoilbyadriverodthatisthenwithdrawn.Theanchorattachestotheguywireviaagroundcable.Thistypeofanchorislesssusceptibletofrostheavethanthethreeotheranchorsdescribedabove.

C.6.4 Monitoring

Polarconsultwillcontinuetomonitortheinstallationatthetestsiteforperformance.

1. Monitorseasonalfluctuationsinsoilthermalprofilestoestablishbaselinethermalprofilesandtheperformanceofthemicro‐thermopiles.

2. Monitorguywiretensionsanddifferentialelevationsofguywiresandpolefoundationtoidentifycreepinthefoundations.

3. MonitorperformanceoftheGFRPpoleandsplice.


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Figure C-17 Installing Micro-Thermopile for Guy Anchor

ContractorGeoTekAlaska,Inc.drillingaholeforinstallationofamicro‐thermopileata45‐degreebatterangleusingaGeoProbe8040seriesdrillrig.Themicro‐thermopilewillserveasaguyanchorfortheprototypeguyedGFRPpole

installationattheFairbanksTestSite.(Polarconsult,2011).


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Figure C-18 Setting Micro-Thermopile Guy Anchor with Sand Slurry Backfill

Settingmicro‐thermopileguyanchorwithasandslurry.(Polarconsult,2011)


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Figure C-19 Installing Micro-Thermopile for Guy Anchor

ContractorGeoTekAlaska,Inc.drillingaholeforinstallationofamicro‐thermopileata45‐degreebatterangleusingaGeoProbe8040seriesdrillrig.Themicro‐thermopilewillserveasaguyanchorfortheprototypeguyedGFRPpole

installationattheFairbanksTestSite.(Polarconsult,2011).


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Figure C-20 Micro-Thermopiles Staged at Fairbanks Test Site for Installation of Prototype Foundations

1½‐inch‐diameterby25‐foot‐longmicro‐thermopilesusedforpolebaseandguyanchorsystemsforaprototypeguyedGFRPpoleinstalledattheFairbanksTestSite.Threemicro‐thermopilesareusedatthepolebase,andoneeachfortwo

ofthefourguyanchors.(Polarconsult,2011)


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Figure C-21 Micro-Thermopile Tripod for Prototype Pole Foundation

Micro‐thermopiletripodforprototypepolefoundation.Thefourthpipeatleftisasoiltemperaturemonitoringwellthatisusedtomonitorthethermal‐affectedzonearoundthethermopiles.Thereisasecondsoiltemperaturemonitoringprobelocatedapproximately40feetfromthepolebase(notshowninphoto)thatisusedtoestablishthebaseline

thermalprofileofthesite.(Polarconsult,2011)


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Figure C-22 Installing Helical Screw Anchor for Guy Anchor

ContractorCityElectric,Inc.installingahelicalscrewanchorwithtwo8‐inchflights.Theanchorwasdriven15feetintothegroundata45‐degreebatterangle.Theanchorwillbeusedtosecureoneofthefourguysontheprototype

GFRPpoleinstalledattheFairbanksTestSite.(Polaconsult,2011)


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Figure C-23 Guy Attached to Micro-Thermopile Foundation

GuywiresupportingtheinstalledprototypeGFRPpoleattheFairbanksTestSite.Theguyanchorisamicro‐thermopileinstalledata20‐degreebatterangle.Thisguywireincludesaloadcelltomonitorguywiretension.Theloadcellreaderisattachedtothecellandisvisibleinthephoto(blackandyellowdevicebelowtheguywire).Polarconsult,2011.)


MAY 2012 PAGE C-58

Figure C-24 Assembling the Prototype GFRP Pole Splice

ContractorCityElectric,Inc.installingthefieldsplicefortheprototypeGFRPpole.40‐footand20‐footGFRPpolesegmentsweresplicedtocreatethe60‐footpoleerectedatthesite.Thespliceslidesoverthepolesegmentsandcarriesmomentthroughcontactbetweenthepoleandsplicewalls.Verticalloadsarecarriedthroughthebuttendsofthepolesegments.Noglueoradhesiveisnecessaryforthesplicetodevelopthefullmechanicalstrengthofthepole.Thescrews

servetopreventdifferentialmovementbetweenthepoleandsplice.(Polarconsult,2011)


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Figure C-25 Installed GFRP Pole, Micro-Thermopiles, and Adapter Plate

DetailofprototypeGFRPpolebaseattheFairbanksTestSite.Thecustom‐designedbaseplateaccommodatesthevariableangleandlocationofthethreemicro‐thermopilesandincludesahingesothepolecanbeloweredifneeded.Thebaseplateallowsforadjustmentofthehingeorientationduringinstallationsoaguyanchorcanbeusedtowinch

thepoledown.(Polarconsult,2011)


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Figure C-26 Prototype GFRP Pole Foundation During Installation

DetailofprototypeGFRPpolebaseattheFairbanksTestSite.Theadapterplatewasadjustedduringinstallationsothehingeisorientedinlinewiththeguyanchorinthedistance(orangeflagging).Thisallowsuseoftheguyanchorto

lowerthepolewithawinchifneeded.(Polarconsult,2011)


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Figure C-27 Prototype Pole at the Fairbanks Test Site

ViewoftheprototypeguyedGFRPpoleinstalledattheFairbanksTestSite.Thisphotographistakenatadistanceofapproximately200yardsfromthe60‐foottallpole.(Polarconsult,2011)


MAY 2012 PAGE C-62

Figure C-28 Prototype Pole at the Fairbanks Test Site

ViewoftheprototypeguyedGFRPpoleinstalledattheFairbanksTestSite.Thisphotographistakenatadistanceofapproximately25yardsfromthe60‐foottallpole.Thefourguysandthepolesplicearevisibleinthisphotograph

(Polarconsult,2011)


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APPENDIXCATTACHMENTS

AttachmentC‐1:ZarlingAeroConsulting(ZAE)ThermalAnalysisofThermopile


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AttachmentC‐2:ArcticFoundations,Inc.(AFI)ShopDrawings


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AttachmentC.2.1 ArcticFoundations,Inc.(AFI)ShopDrawingforPile


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AttachmentC.2.2 ArcticFoundations,Inc.(AFI)ShopDrawingforGuyAnchor


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APPENDIXD

CONCEPTUALDESIGNFORSUBMARINECABLES


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TABLEOFCONTENTS

APPENDIXDATTACHMENT...............................................................................................................................................5 ATTACHMENTD‐1:CABLETRICITYHVDCTRANSMISSIONSYSTEMSFORRURALALASKAAPPLICATIONSDCPOWERCABLES

FOR1–5MWCONVERTERS............................................................................................................................................5


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APPENDIXDATTACHMENT

AttachmentD‐1:CabletricityHVDCTransmissionSystemsforRuralAlaskaApplicationsDC

PowerCablesfor1–5MWConverters


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APPENDIXE

SWERCIRCUITSANDHVDCSYSTEMGROUNDING


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TABLEOFCONTENTS

E.1 SINGLE‐WIREEARTHRETURN(SWER)CIRCUITS...................................................................................7

E.2 SYSTEMGROUNDING.............................................................................................................................................7

APPENDIXEATTACHMENTS.............................................................................................................................................9 ATTACHMENTE‐1:HVDCGROUNDELECTRODEOVERVIEW...................................................................................................9 ATTACHMENTE‐2:GROUNDINGSTATIONFIGURE...................................................................................................................25


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LISTOFFIGURES

FigureE‐1 GroundingStation....................................................................................................................................27


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E.1 SINGLE‐WIREEARTHRETURN(SWER)CIRCUITS

Themosteconomicalapplicationsoflow‐powerhigh‐voltagedirectcurrent(HVDC)systemsinAlaskawillusemonopolarcircuitswithsingle‐wireearthreturn(SWER).AlaskahasadoptedtheNationalElectricSafetyCode(NESC)toregulatethedesignandinstallationofutilitygradeelectricsystems.TheNESCdoesnotallowtheuseofSWERcircuits.Thisruleisbasedonconsiderationsoflifesafety(avoidanceofsteppotentialhazards)andeconomics,asDCSWERcircuitscancauseacceleratedcorrosionofnearbyburiedmetalinfrastructuresuchaspipelines.

SWERcircuitsaresuccessfullyusedonACandDCcircuitsinmanyinternationaljurisdictions.InmanyruralAlaskaapplications,theuseofHVDCSWERcircuitsisasafeandappropriatetechnologythatcansavesignificantcosts.ThereisaprocesstoobtainwaiverstotheNESCrulesthatwillpermittheinstallationofSWERcircuits.TwoACSWERsystemsbuiltinthe1980ssuccessfullyobtainedsuchwaivers.

PolarconsultsubcontractedwiththeManitobaHVDCResearchCentre(MHRC)topreparealetterreportsummarizingthetechnicalandcodeissuesassociatedwiththeappropriateuseofSWERcircuits.ThatreportisincludedasAttachmentE‐1tothisappendix.

E.2 SYSTEMGROUNDING

Aconceptualdesignforalow‐powerHVDCgroundingstationsuitableforusewiththeproposedHVDCtransmissionsystemisincludedintheattachmenttothisappendix.


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APPENDIXEATTACHMENTS

AttachmentE‐1:HVDCGroundElectrodeOverview


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AttachmentE‐2:GroundingStationFigure


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Figure E-1 Grounding Station


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APPENDIXF

HVDCPOWERCONVERTERDEVELOPMENT


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TABLEOFCONTENTS

F.1 CONVERTERDEVELOPMENT.............................................................................................................................7 F.1.1 INTRODUCTION..................................................................................................................................................................7 F.1.2 CONVERTERSIZINGANALYSIS........................................................................................................................................7 F.1.3 CONVERTERTESTRESULTS...........................................................................................................................................10

F.1.3.1 FiberOpticTriggeringSysteminHigh‐VoltageTank..............................................................10 F.1.3.2 IGBTSwitchesinHigh‐VoltageTank...............................................................................................10

APPENDIXFATTACHMENTS...........................................................................................................................................13 ATTACHMENTF‐1:PPSHVDCPOWERCONVERTERREPORT...............................................................................................13


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LISTOFFIGURES

FigureF‐1 TypicalLoadDurationProfileforanAlaskaVillage....................................................................8

FigureF‐2 PeakLoadsinAlaskaVillages(2007–2009).................................................................................9


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F.1 CONVERTERDEVELOPMENT

F.1.1 Introduction

Thehigh‐voltagedirectcurrent(HVDC)converterdevelopedunderthisprojectisa1‐megawatt(MW)powerconvertercapableofbidirectionalpowerconversionbetweenthree‐phase480voltsalternatingcurrent(VAC)and50kilovolts(kV)HVDC.TheconvertercapacityisappropriatetosupplytheelectricalneedsofmostAlaskavillages.Incontrast,existingHVDCpowerconvertersystemsareonlycosteffectiveatmuchlargertransmissioncapacities,startingatapproximately50MWandextendingupto1,000sofMWsofcapacity.

MultipleHVDCconverterscanbe“paralleled”toachievehigherpowertransmissioncapacitieswhereneeded.BasedonPhaseIIdevelopmentwork,thepriceofacommerciallyproduced1‐MWHVDCpowerconverterisestimatedtobe$250,000.Atleasttwo1‐MWconvertersareneededforacomplete1‐MWHVDCtransmissionsystem.

ThisappendixpresentsPrincetonPowerSystems,Inc.’s(PPS’s)finaldeliverablesforconverterspecification,design,andtestplanunderPhaseIIoftheHVDCtechnologydevelopmentprogram(AttachmentF‐1).

PPShassuccessfullydemonstratedoperationoftheprototypeconvertersatthefull50kVDCandpowerflowinbothinverter(HVDCtoAC)modeandrectifier(ACtoHVDC)modeinacontrolledtestfacilitysetting.Thesetestingeffortsvalidatethedesignandbasicfunctionalityoftheconverter.

Inthecourseoftesting,PPSidentifiedtwohardwareproblemsthatpreventedfull‐powertestingoftheprototypeconverters.PPShasinvestigatedtheseproblemsandidentifiedtheactionsnecessarytocorrectbothproblems.TheproblemsandsolutionsarediscussedinAttachmentF‐1tothisappendix.

PPSiscontinuingtoworkonthehardwaremodificationsneededtocorrectthepriortechnicalproblems.Duetothelonglead‐timetoobtainsuitablereplacementinsulatedgatebipolartransistor(IGBT)switches,theconvertermodificationsandtestingarenotexpectedtobecompleteduntillate2012.PPSwillissueasupplementalreportdetailingtheresultsoffinalPhaseIItestingwhentestingiscompleted.ThissupplementalreportandthefullyoperationalconverterswillbePPS’sfinaldeliverableunderPhaseIIofthisresearchanddevelopment(R&D)project.

F.1.2 ConverterSizingAnalysis

TheelectricalloadcharacteristicsofruralAlaskancommunitiesthatarethetargetofthisprojectwereevaluated.ThecapacityoftheHVDCintertiesystemwasbasedonthelikelypeakloadsandloaddurationprofilesoftheselectedcommunities.

Thedurationofpeakloadsprovidesaneconomicbasisfordesigncapacityoftheintertie.Ingeneral,theintertieisdesignedtominimizethelinelossesatpeakloads.TheloaddurationprofileforHooperBayispresentedonFigureF‐1.ThisprofileisrepresentativeofruralAlaskancommunitieswithapeakloadof760kW,andwillgenerallyapplytoothercommunities.Somecommunities,suchasthosewithfishprocessors,willhaveloadprofilesdifferentthanthatshownonFigureF‐1.


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Figure F-1 Typical Load Duration Profile for an Alaska Village

0

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0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Percent of Time Load is Equaled or Exceeded

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Polarconsult,201241

ThepeakloadsofruralAlaskacommunitiesparticipatinginthePowerCostEqualization(PCE)programwerereviewedtodeterminetheappropriatepowercapacityfortheHVDCintertiesconsideredforthisstudy.ThedistributionofpeakloadsispresentedonFigureF‐2.

Basedonthisanalysis,a1‐MWpowerintertieisanappropriateconceptualcapacityforthemajorityofruralAlaskainterties.Formaximumreliabilityandflexibility,thepowerconverterspecificationscallfora1‐MWunitcomprisedoftwo500‐kWmodulesoperatinginparallel.Theconvertermodulescanbeconnectedtooperateinparallel,thusprovidingadditionalcapacityuptoafewMWswherenecessary.IntertiesdesignedformorethanafewMWsmaywarrantreevaluationoftheACinterfacevoltage(480volts[V]forthe500‐kWpowerconvertermodule).

41DatageneratedforHooperBayusingtheAlaskaVillageElectricLoadCalculator(NREL,2005)


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Figure F-2 Peak Loads in Alaska Villages (2007 – 2009)

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(2) 1 MW HVDC CONVERTERS USED FOR BIPOLAR INTERTIE, ADEQUATE FOR 82% OF COMMUNITIES.

1 MW HVDC CONVERTER, ADEQUATE FOR 76% OF COMMUNITIES.

1 MW HVDC CONVERTER WITH 500KW MODULE FAILURE, ADEQUATE FOR 60% OF COMMUNITIES.

Source: 2009 Power Cost Equalization Data, Alaska Energy Authority


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F.1.3 ConverterTestResults

Inthecourseoftestingtheprototypeconverters,PPShassuccessfullydemonstratedoperationatthefull50kVDCandpowerflowinbothinverter(HVDCtoAC)modeandrectifier(ACtoHVDC)mode.Inthecourseoftesting,PPSidentifiedtwohardwareproblemsthatpreventedcompletionofPhaseIItestingoftheprototypeconverters,includingdemonstrationoffullpoweroperation.PPShasinvestigatedtheseproblemsandidentifiedtheactionsnecessarytocorrectbothproblems.Theproblemsandsolutionsaresummarizedbelow.

F.1.3.1 FiberOpticTriggeringSysteminHigh‐VoltageTank

Afiberopticnetworkisusedtotriggerthesolid‐stateIGBTswitchesinsidethehigh‐voltagetank.Testingrevealedproblemswiththetriggeringtimingandreliabilityofthistriggeringsystem.Investigationdeterminedthatthelensesusedinthefiberopticsystemexhibitexcessivelyhighsignalloss,causingtheobservedtimingandreliabilityissues.PPShasidentifiedandtesteddifferentlensesandisproceedingtoreplacethelensesinbothprototypeconvertermodulestosolvethisproblem.

F.1.3.2 IGBTSwitchesinHigh‐VoltageTank

TheIGBTswitchesinthehigh‐voltagetankwerefoundtoenterthermalrunawaywhentheprototypeconverterisoperatedatlow‐powerlevelsininverter(HVDCtoAC)mode.Investigationhasdeterminedthattheseswitchesdonotperforminaccordancewiththemanufacturer’sspecifications.Consultationswiththemanufacturerhasnotproducedanacceptableremedy,andPPShasconcludedthattheseIGBTscannotbeusedforthisapplication.PPShasidentifiedalternateIGBTsthatmeetthetechnicalandeconomiccriteriaofthisproject,andisproceedingtoupgradetheconverterswiththeseswitches.Becausetheswitchesoperateatadifferentvoltagethantheoriginalswitchesandhaveadifferentformfactor,redesignofthehigh‐voltagestageboardsisnecessary.

Becauseofthehardwareproblemsidentified,PPShasnotyetcompletedconvertertesting.FinaltestingispendingreceiptofnewIGBTs.

FigureF‐3showsasimplifiedschematicillustratingthecurrentdevelopmentstatusoftheconverter’sbasicfunctionalmodes.


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Figure F-3 Simplified Schematic Illustrating Technical Progress


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APPENDIXFATTACHMENTS

AttachmentF‐1:PPSHVDCPowerConverterReport


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APPENDIXG

HVDCSYSTEMPROTECTION,CONTROLS,ANDCOMMUNICATIONS


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TABLEOFCONTENTS

G.1 INTRODUCTION........................................................................................................................................................7 G.1.1 POINT‐TO‐POINTSYSTEMS.............................................................................................................................................7 G.1.2 MULTITERMINALHVDC(MTDC)SYSTEMS...............................................................................................................7

G.2 PROTECTIVEHARDWARE...................................................................................................................................7

G.3 COMMUNICATIONS.................................................................................................................................................7 G.3.1 FAULTDETECTION............................................................................................................................................................8 G.3.2 INFRASTRUCTURE..............................................................................................................................................................8

G.4 OVERHEADINTERTIECOMMUNICATIONOPTIONS................................................................................9 G.4.1 OPTICALGROUNDWIRE..................................................................................................................................................9 G.4.2 POWERLINECARRIER......................................................................................................................................................9 G.4.3 WRAPPEDFIBER‐OPTICCABLE......................................................................................................................................9 G.4.4 SEPARATETELECOMUNDERBUILD................................................................................................................................9

G.5 UNDERGROUNDCABLEINTERTIEOPTIONS..............................................................................................9

G.6 SUBMARINECABLEINTERTIEOPTIONS....................................................................................................10

G.7 BROADBANDINTEGRATION............................................................................................................................10

APPENDIXGATTACHMENTS...........................................................................................................................................11 ATTACHMENTG‐1:MHRCTASK3,HVDCSTATIONHARDWARERECOMMENDATIONS..................................................11 ATTACHMENTG‐2:MHRCTASK2,MULTI‐TERMINALHVDCTECHNICALREVIEW........................................................25 ATTACHMENTG‐3:MHRCTASK5,CARRIERCOMMUNICATIONS........................................................................................45


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LISTOFTABLES

TableG‐1 CommunicationsOptionswithHVDCInterties.........................................................................G‐8


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G.1 INTRODUCTION

Thisappendixdiscusseselectricalprotection,controls,andcommunicationsrequirementsneededtooperatethehigh‐voltagedirectcurrent(HVDC)systemsdiscussedinthisreport.Therearecertainminimumprotection,control,andcommunicationprovisionsrequiredofanyHVDCsystem.

Initssimplestform,theprotection,controls,andcommunicationsprovisionsmaybemanuallyoperated.Thisapproachissimplertomanageandlesscostlytoinstallandmaintainthanfullyautomatedsystems,butisgenerallylimitedtopoint‐to‐pointinterties.

Theprotection,controls,andcommunicationsneedsofmorecomplexmultiterminalHVDC(MTDC)systemsrequirestheuseofautomatedcontrolsforoperation.Therequirementforautomatedcapabilitiesaremorecostlyandcomplicatedtooperate.

G.1.1 Point‐to‐PointSystems

ManyruralHVDCintertiesmaybenefitfromapoint‐to‐pointHVDCsystem.Low‐power(<1MW)point‐to‐pointmonopolarHVDCsystemscanautomaticallyregulatepowerflowovertheHVDCsystembymonitoringtheHVDCvoltage.Nocommunicationsbetweentheconvertersareneededtoachievethisbasicpowertransferfunction.Existingcommercialtelecommunicationsnetworksinthecommunitiescanbeusedtoprovidesomedegreeofmonitoringandcontrolfunction.

G.1.2 MultiterminalHVDC(MTDC)Systems

MTDCnetworksbydefinitionhavemorethantwoHVDCconverterstationsconnectedtoagivenHVDCline.EachoftheconverterstationsiscapableofaddingorsubtractingpowerfromtheHVDCline.

MTDCnetworksareprojectedtobethelowestcostintertiesolutionformanyoftheruralenergynetworksunderconsideration.Theseregionsincludeinterconnectionofseveralsoutheastcommunities,theadjacentcommunitiesintheYukon‐KuskokwimDelta,andothersintheBristolBayarea.Accordingly,thetechnicalfeasibilityofMTDCnetworksisofparticularinterestforAlaska’sutilityindustry.

G.2 PROTECTIVEHARDWARE

RecommendationspreparedbytheManitobaHVDCResearchCentre(MHRC)discussthegeneralDC‐sideHVDCconverterstationhardwarenecessaryforbasicoperationandprotectionoftheHVDCsystem.ThisinformationispresentedinAttachmentG‐1tothisappendixandistitled“TechnicalNoteonHVDCStationHardware.”

ProtectiveAC‐sidehardwarewillincludefusesorbreakers,disconnects,andcontrolsasneededtointegratewiththelocalgeneratingplant.Project‐specificdesignisnecessaryastheseinterfacescanrangefrombasicandmanuallyoperatedtohighlyintegratedandautomated,dependingontheneedsoftheparticularapplication.ThepowerconvertersdevelopedbyPPSsupportstandardcommunicationprotocolstoallowintegrationwithoverallcontrolsystems.

G.3 COMMUNICATIONS

Communicationsareusedformonitoringofconverterstationstatus,economicdispatchofdistributedgenerationassets,faultdetectionontheHVDCnetwork,andrelatedutilityfunctions.Systemsoftenincludededicatedvoiceanddatacircuitstofacilitatecommunicationsbetweendifferentpartsoftheutilitytransmissionnetwork.


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G.3.1 FaultDetection

WithoutdifferentialcurrentmonitoringbetweentheHVDCconverterstations,ifthetotalcurrentintotheHVDCsystem(faultcurrent+loadcurrent)islessthantheratedsystemcurrent(20amperesfora1‐MWintertie),therectifyingconverterwillnotbeabletodistinguishthefaultloadfromanormalloadandwillcontinuetoinputpowerintotheHVDClinetomaintaintheHVDCvoltage.Ifthefaultcurrentishighenoughtoexceedthecapacityoftherectifyingconverter,thentheconverterwilltripandannounceafault.

Theresultisthatalowimpedancefaultcangenerallybedetectedbytheanomalouslyhighpowerdraw,whereasahighimpedancefaultcanremainundetectedindefinitelywiththisscheme.Timelydetectionandcorrectionisthereforedesirablewherepractical.

ACsystemsexperiencesimilarproblemsdetectinghighimpedancefaults,sothistypeofriskisnotwithoutprecedentonutilitysystems.Theremotenessandlackofpeopleinthevicinityofthesetransmissionlinesisafactorthatshouldbeconsideredwhenutilitiesevaluatethisrisk.Aproject‐specificanalysisshouldbeconductedforeveryintertietoevaluatethecostoffaultdetectioncapabilitiesagainsttherisksassociatedwithundetectedfaults.

Detectionofpersistenthighimpedancefaultsrequires,ataminimum,slow‐speedcommunicationbetweentheconverterstationsanddifferentialcurrentmonitoring.Ifthefaultimpedanceissohighthatthefaultcurrentisbelowtheerrorofthedifferentialcurrentdetectionmethod(ascouldbethecaseforadownedconductorlyingonice,forexample),thefaultmayremainunnoticedevenwiththisdetectionregimeinplace.Theonlypracticalwaytoidentifysuchfaultsisbyphysicalinspectionoftheintertieline.FaultdetectionisdiscussedintheMHRCTechnicalNoteonHVDCStationHardwareRecommendationsincludedasAttachmentG‐1tothisappendix.

G.3.2 Infrastructure

AllremoteAlaskacommunitieshaveaccesstobasictelephoneserviceandbroadbandinternetservice.Ataminimum,theseservicesareprovidedthroughgeosynchronoussatelliteplatforms.Dependingontheprojectlocation,communitiesmaybeservedbyexistingmicrowaverelaysystems,copperwirenetworks,fiber‐opticnetworks,oracombinationofthese.

Theslowestcommunicationoptionavailablestatewideisgeosynchronoussatellite‐basedcommunicationswithaninherentlatencyofatleast250millisecondsforone‐waycommunications.Thislatencyarisesfromthetraveltimeforasignaltoreachtheorbitingsatelliteandreturntoearth.SignalprocessingattheEarthstationsoraboardthesatelliteaddtothislatency.

Thiscommunicationsmethodwouldbesufficientforabasicdifferentialcurrentmonitoringprotocolandforcertainsupervisorycontrolanddataacquisition(SCADA)functionsforanHVDCintertie.

Optionsforintegrateddedicatedcommunicationscircuitsarediscussedin‘TechnicalNoteonCarrierCommunications,”preparedbyMHRC,includedasAttachmentG‐3tothisappendix.

Thecost‐effectivenessofsuchoptionswilldependonthetypeofHVDCintertie,andonthespecificconfigurationoftheHVDCline.TableG‐1summarizesthethreebasicHVDCintertieconfigurationsandpotentiallysuitablecommunicationstechnologiesforeach.

Table G-1 Communications Options with HVDC Interties

Intertie Type Communications Option


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Overhead Conductor Optical Ground Wire (OPGW) Carrier

Wrapped fiber-optic cable Separate telecom underbuild

Underground Cable Separate fiber-optic cable in same trench Fiber-optic circuit bundled into power cable

Submarine Cable Fiber-optic cable in conductor tube Fiber-optic cable in armor strand

G.4 OVERHEADINTERTIECOMMUNICATIONOPTIONS

G.4.1 OpticalGroundWire

Opticalgroundwire(OPGW)isatypeofelectricalconductorthathasaluminumconductorstrandssurroundingastainless‐steeltubeattheconductor’score.Opticalfibersareroutedthroughthestainless‐steeltube.OPGWiscommonlyusedasanoverheadgroundingwireonACtransmissiontowersforlightningprotection.

Dependingontheapplication,OPGWmaybesuitableforuseasthecurrent‐carryingconductoronanHVDCtransmissionline.Onepotentiallysignificantdrawbackwouldbetheincreasedcomplexityofrepairingconductorbreaksduetothestainless‐steeltubeandopticalfibers.Theneedforspeciallytrainedpersonnelandequipmenttorepairthistypeofconductorcouldsignificantlydelaytherepairofaconductorbreak,reducingthereliabilityofthetransmissionline.

TheMHRCTechnicalNoteincludedasAttachmentG‐3tothisappendixdiscussesOPGWapplicationsinmoredetail.

G.4.2 PowerLineCarrier

Powerlinecarrier(PLC)isameansofusingacurrent‐carryingconductorinanintertiecircuittocarryadatasignalaswell.Acoilisusedtomagneticallyinduceadatawaveformontotheconductor,andasecondcoilisusedtoreceivethewaveform.PLCsystemshavebeenimplementedonHVDCcircuitsandarediscussedintheMHRCTechnicalNoteinAttachmentG‐3.

G.4.3 WrappedFiber‐OpticCable

Opticalfiberpackagesareavailablethatcanbewrappedoveramessengerwire,suchasthepowerconductor.Therearetwopotentialdrawbackswiththisoption.Thefirstisthattheopticalfibercablewouldincreasethewindexposureandicingsurfaceoftheconductor,increasingenvironmentalloadingsontheoverheadsystem.Thesecondisthatthepresenceoftheopticalfibercablewouldcomplicatetherepairofbrokenconductors.

G.4.4 SeparateTelecomUnderbuild

DependingonthetypeofoverheadlineconstructionusedfortheHVDCintertieline,aconventionaltelecommunicationsunderbuildmaybeappropriate.Thiscouldusefiberorcopperdependingonthespecificcircumstances.

G.5 UNDERGROUNDCABLEINTERTIEOPTIONS


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ThemoststraightforwardmeansofaddingcommunicationstoanundergroundcableHVDCintertieistoincludeaseparatefiber‐opticorcoppercable.Fiberopticswouldbepreferredifasingle‐wireearthreturn(SWER)circuitisused,asitwouldnotpickupthereturncurrent.Conventionaldesignandconstructionpracticesaresuitableforinstallationofco‐locatedundergroundcommunicationandpowercables.

G.6 SUBMARINECABLEINTERTIEOPTIONS

Therearethreegeneraloptionsforbundlingtelecommunicationswithsubmarinepowercables.Allthreeutilizefiberoptics,andareacceptedpracticeforsubmarinepowerand/ortelecommunicationcables.Thesemethodsare:

● Replacingoneormoreofthearmorwiresonthesubmarinecablewithahollowstainless‐steeltubeandroutingopticalfibersthroughthetube(s).

● Utilizingahollowcoppertubeasthecurrent‐carryingconductorandroutingopticalfiberswithinthecoppertube.Thisisacommoncableconstructionontransoceanicfiber‐opticcables.

● Insertingastainless‐steeltubebetweentwolayersofthesubmarinecable,typicallybetweentheleadsheath(ifsoequipped)andthepolyethyleneoutercablejacket.Opticalfibersareroutedthroughthistube.

G.7 BROADBANDINTEGRATION

ThereisanopportunitytointegratebroadbandcommunicationswithcertainHVDCintertieprojects.Wherefeasible,combiningpowerandtelecommunicationsconnectivityintoasingleprojectcansignificantlyincreasethebenefitsofanintertieprojectanddeliverbothcapabilitiesatalowercostthanpossiblethroughindividualprojects.

Thisopportunityisparticularlypromisingforundergroundandsubmarinecableapplications.Inmanyapplications,theincrementalcostofincludingafiberopticbundlewitheitherpowercableisexpectedtobemodestcomparedtotheresultingbenefits.AttachmentD‐1discussesthisopportunityinthecontextofsubmarinecables.


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APPENDIXGATTACHMENTS

AttachmentG‐1:MHRCTask3,HVDCStationHardwareRecommendations


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AttachmentG‐2:MHRCTask2,Multi‐TerminalHVDCTechnicalReview


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AttachmentG‐3:MHRCTask5,CarrierCommunications


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APPENDIXH

CANDIDATEHVDCSYSTEMDEMONSTRATIONPROJECTS


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TABLEOFCONTENTS

H.1 INTRODUCTION........................................................................................................................................................7

H.2 DEMONSTRATIONPROJECTOBJECTIVES.....................................................................................................7

H.3 CRITERIAFORDEMONSTRATIONPROJECTSITES...................................................................................8

H.4 POTENTIALDEMONSTRATIONPROJECTS.................................................................................................10 H.4.1 SUMMARYOFPROJECTSCONSIDERED.........................................................................................................................10 H.4.2 HVDCDEMONSTRATIONPROJECTSONEXISTINGACDISTRIBUTIONLINES.......................................................12

H.4.2.1 DillinghamtoAleknagikACLineConversion(DemonstrationOnly)...............................12 H.4.2.2 EurekaACLineConversion(DemonstrationOnly)..................................................................12 H.4.2.3 HopeSubstationtoHopeACLineConversion(DemonstrationOnly).............................12 H.4.2.4 Homer–SeldoviaACLineConversion(DemonstrationOnly)............................................13

H.4.3 HVDCDEMONSTRATIONPROJECTSONNEWACDISTRIBUTIONLINEEXTENSIONS.........................................13 H.4.3.1 GVEAPhillipsRoadLineExtension..................................................................................................14 H.4.3.2 GVEACummingsRoadLineExtension...........................................................................................14 H.4.3.3 MEAtoIndependenceMineLineExtension.................................................................................14

H.4.4 HVDCINTERTIEPROJECTS...........................................................................................................................................15 H.4.4.1 BarrowtoAtqasukHVDCIntertie.....................................................................................................15 H.4.4.2 NometoTellerandBrevigMissionHVDCIntertie....................................................................15 H.4.4.3 PilgrimHotSpringstoNomeHVDCIntertie................................................................................15 H.4.4.4 St.Michaels–StebbinsHVDCIntertie.............................................................................................16 H.4.4.5 St.Mary’stoMountainVillageHVDCIntertie..............................................................................16 H.4.4.6 DillinghamtoManokotakHVDCIntertie.......................................................................................16 H.4.4.7 NewStuyahok–EkwokHVDCIntertie...........................................................................................16 H.4.4.8 Kodiak–OuzinkieHVDCIntertie......................................................................................................16 H.4.4.9 Green’sCreektoHoonahHVDCIntertie........................................................................................17 H.4.4.10 PetersburgtoKakeHVDCIntertie....................................................................................................17 H.4.4.11 GustavustoGlacierBayNationalParkIntertie(HVDCDemonstrationOnly)..............17

H.4.5 PROJECTMAPS.................................................................................................................................................................18


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LISTOFTABLES

TableH‐1 TypesofHVDCDemonstrationProjectsandFactorsforEach................................................9

TableH‐2 PotentialHVDCDemonstrationProjects........................................................................................10


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LISTOFFIGURES

FigureH‐1 LocationMapforPotentialDemonstrationProjectSites........................................................11

FigureH‐2 VicinityMapforDemonstrationProjectsnearDillingham.....................................................18

FigureH‐3 VicinityMapforEurekaACLineConversion................................................................................19

FigureH‐4 VicinityMapforHopeACLineConversion...................................................................................20

FigureH‐5 VicinityMapforSeldoviaACLineConversion.............................................................................21

FigureH‐6 VicinityMapforDeltaJunctionACLineExtension....................................................................22

FigureH‐7 VicinityMapforDeltanaACLineExtension.................................................................................23

FigureH‐8 VicinityMapforIndependenceMineACLineExtension.........................................................24

FigureH‐9 VicinityMapforBarrow–AtqasukHVDCIntertie.....................................................................25

FigureH‐10 VicinityMapforDemonstrationProjectsnearNome...............................................................26

FigureH‐11 VicinityMapforSt.Michaels–StebbinsHVDCIntertie...........................................................27

FigureH‐12 VicinityMapforSt.Mary’s–MountainVillageHVDCIntertie..............................................28

FigureH‐13 VicinityMapforNewStuyahok–EkwokHVDCIntertie..........................................................29

FigureH‐14 VicinityMapforKodiak–OuzinkieHVDCIntertie.....................................................................30

FigureH‐15 VicinityMapforGustavusandHoonahHVDCInterties...........................................................31

FigureH‐16 VicinityMapforKake–PetersburgHVDCIntertie....................................................................31


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H.1 INTRODUCTION

Thisreportincludestheevaluationofpotentialprojectsfordemonstrationofthehigh‐voltagedirectcurrent(HVDC)technologyinPhaseIII.Thiseffortconsistedofthefollowingmajoractivities:

● Definingtheprimaryobjectivesofademonstrationproject;

● Definingthekeycriteriaforcandidateprojects;

● Identifyingpotentialintertieprojects;

● Contactinglocalstakeholderstogatherinformationaboutthoseprojects;and

● EvaluatingtheprojectsforsuitabilityasademonstrationofthisHVDCtechnology.

Thisappendixsummarizesandpresentsthefindingsfromtheseactivities.Aspecificsitehasnotbeenselectedforademonstrationprojectatthistime.Polarconsultwillcontinuetoworkwiththevariousprojectstakeholderstoidentifyaspecificdemonstrationprojectinthefuture.

H.2 DEMONSTRATIONPROJECTOBJECTIVES

PolarconsultworkedwiththeStakeholder’sAdvisoryGroup(SAG),individualstakeholders,Polarconsultsubcontractors,andotherinterestedentitiesoverthecourseofPhaseIItorefinetheobjectivesofthePhaseIIIdemonstrationprojectfortheproposedHVDCsystem.

Definingtheseobjectiveswasamajortopicofdiscussionatthe2ndSAGMeeting,heldinAnchorageonJanuary14,2011.AseriesofconferencecallswereheldwithmembersoftheSAGinJanuaryandFebruary2011torefinetheobjectivesofthedemonstrationprojectandthecandidatesitesidentifiedbyPolarconsult.

Theseeffortsestablishedthefollowingaskeyobjectivesofthedemonstrationproject:

● FacilitateexpeditiousadvancementoftheproposedHVDCsystem.Ademonstrationprojectthatcannotbeimplementedforyearsduetoprohibitivecost,regulatoryimpediments,orsimilarfactorscouldundulydelaycommercialacceptanceofthesystemandwidespreaddeploymentinAlaska.

● Demonstratetostakeholders(Alaskautilities,policymakers,regulators,etc.)thattheHVDCconverterisfunctional,robust,andpracticalunderthelogistical,electrical,andenvironmentaloperatingconditionstypicalofruralAlaskaapplications.

● Demonstratethatinnovativeaspectsofthetransmissionlineconstruction,suchasuseofsingle‐wireearthreturn(SWER)circuitsinpermafrostregions,newoverheadlinedesignsormaterials,andsimilarsystemelementsarereliable,cost‐effective,andappropriateforruralAlaskaintertieapplications.

OneofthekeyinsightsprovidedbytheSAGwasthatthecommercializationplanfortheproposedsystem,includingthedemonstrationphase,shouldbedesignedinameasuredmannerthatincrementallydemonstratesandprovesupthevarioustechnicalaspectsofthesystem.Itwassuggestedthatasingleoverlyambitiousdemonstrationprojectthatfeaturesseveralinnovativetechnologiesincreasestheriskthatanyonenoncriticaltechnicalfailuremaybecomeinterpretedasafailureoftheoverallsystem.

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fromadvancedprototypestoacommercialproduct.PhaseIIIwillalsoincludeafullscalefielddemonstrationoftheHVDCtechnologyonautilitysysteminAlaska.Thespecificprojectdetailsaredependantonthecandidatelocationselectedfortheintertie.PhaseIIIisintendedtobethefinalproof‐of‐conceptproject,tobefollowedbycommercialdeploymentofthesystem.

H.3 CRITERIAFORDEMONSTRATIONPROJECTSITES

PhaseIIIdemonstrationswillpresentafullyfunctionalreal‐worldHVDCtransmissionlineusingtheconvertertechnologydevelopedinthisproject.AvailableinventoriesofAlaskaintertiecandidatesarepresentedinDistributingAlaska’sPower(WHPacific,2008)andRuralAlaskaElectricUtilityIntertiesSurvey(Neubauer,1997).

Polarconsultconductedanextensivereviewofpotentialcandidatedemonstrationprojects,startingfromtheseresourcesandothercurrentinformation.Theresultinglistofpotentialdemonstrationprojectsisnotcomprehensive,astherearenumerousopportunitiesforruralAlaskapowerinterties,butitdoesprovidearepresentativeselectionofgeographicandtechnicalcriteriafordemonstrationsites.Threetypesofdemonstrationprojectswereconsidered,listedbelow.KeyfactorsaboutthesuitabilityofthesetypesofprojectsaresummarizedinTableH‐1.

1. NewRuralAlaskaHVDCIntertie.ThisoptionwouldbeafullyfunctionalHVDCintertiedemonstration.ItwouldconsistofbuildinganewintertiebetweentwoAlaskavillages,orpossiblybetweenalargergridandavillage.

2. NewACDistributionLineExtensionOperatedasHVDCforTrialPeriod.Thisoptionwouldbeanewalternatingcurrent(AC)distributionlineextensionfromanexistingsystemtoanewarea.ThelineextensionwouldbeoperatedasanHVDClineforthedemonstrationperiod,andthenconvertedtoACafterthedemonstrationprojectconcluded.

3. ExistingACDistributionLineExtension,ConvertedtoHVDCforDemonstrationThenSwitchedBacktoAC.ThisoptionwouldconvertanexistingACdistributionlinetoHVDCforthedemonstrationproject.ThelinewouldbeconvertedbacktoACafterthedemonstrationprojectconcluded.


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Table H-1 Types of HVDC Demonstration Projects and Factors for Each

Projects

Factors

Permanent HVDC Intertie Between Two Alaska

Villages

(Operate as HVDC)

AC Distribution System Extension

(Operate as HVDC, then convert to AC)

Existing AC Distribution Line

(Convert to HVDC, then revert to AC)

Function Intertie limited to power transmission (no services along intertie route)

Power Capacity

Peak load limited to 500 kW (to utilize existing prototype converters)

Cost & Length Intertie length of 10+ miles

to achieve cost savings over an AC intertie

Minimize intertie length (to maintain affordable budget and help avoid funding delays)

Schedule

3 to 5+ years

Requires (design, permitting, right-of-way,

funding, etc.)

1-3+ years

(May require right-of-way acquisition, design, permitting,

funding, etc.)

+/- 1 year

(Existing right-of-way, should require fewer permits and design,

funding, etc.)

Benefits

1. HVDC demonstration.

2. New intertie lowers utility costs to both communities.

1. HVDC demonstration.

2. Utility/public receive an AC line extension.

1. HVDC demonstration only. Hosting utility incurs costs and customers incur

service interruptions.

Organizational Complexity

Two utilities involved, may require RCA involvement and regulatory oversight.

Single utility involvement (to reduce interconnection or

regulatory issues).

Single utility involvement (to reduce interconnection or

regulatory issues).

Technical

Intertie connections at 480-V bus of existing

power plants.

Intertie connections at distribution voltage. Step

up/down transformers required.

Intertie connections at distribution voltage. Step

up/down transformers required.

kW:kilowatt

RCA:RegulatoryCommissionofAlaska

V:volt


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H.4 POTENTIALDEMONSTRATIONPROJECTS

H.4.1 SummaryofProjectsConsidered

TheintertiesprojectsreviewedbyPolarconsultarelistedbycategoryinTableH‐2andshownonFigureH‐1.Moredetailedinformationandpreliminarymapsofpotentialintertieroutesareprovidedonthefollowingpages.

Table H-2 Potential HVDC Demonstration Projects

RuralAlaskaMicrogrids MajorAlaskaGrids

New HVDC Intertie

Build as HVDC; keep as HVDC after demonstration.

Barrow – Atqasuk (NSB) Pilgrim Hot Springs – Nome (NJUS)St. Mary’s – Mountain Village – Pilot

Station (AVEC) Dillingham – Manokotak (NEC) New Stukahok – Ekwok (AVEC) Kodiak – Ouzinkie (KEA - OED)

Kake – Petersburg (IPEC/SEAPA)

Hoonah – Green’s Creek (IPEC/ AEL&P)

AC Line Extension

Build as HVDC; convert to AC after demonstration.

Gustavus – Glacier Bay Nat’l Park (GEC)

Delta Junction (GVEA) Deltana (GVEA)

Independence Mine (MEA)

Existing AC Line Demonstration

Convert to HVDC; revert to AC after demonstration.

Dillingham – Aleknagik (NEC) Glennallen – Eureka (CVEA) Canyon Creek – Hope (CEA)

Homer – Seldovia (HEA)

AcronymsandAbbreviations:

NEC NushagakElectricCooperative,Inc.

NSB NorthSlopeBorough

NJUS NomeJointUtilityService

IPEC InsidePassageElectricCooperative,Inc.

SEAPA SoutheastAlaskaPowerAgency

GEC GustavusElectricCompany

AVEC AlaskaVillageelectricCooperative,Inc.

CEA ChugachElectricAssociation,Inc.

HEA HomerElectricAssociation,Inc.

CVEA CopperValleyElectricAssociation,Inc.

KEA KodiakElectricAssociation,Inc.

OED CityofOuzinkieElectricDepartment

MEA MatanuskaElectricAssociation,Inc.

GVEA GoldenValleyElectricAssociation,Inc.


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Figure H-1 Location Map for Potential Demonstration Project Sites


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H.4.2 HVDCDemonstrationProjectsonExistingACDistributionLines

ThissectionprovidesoverviewsofpotentialHVDCdemonstrationprojectsthatwouldbeimplementedonexistingACdistributionlines.TheAClinewouldbeconvertedtoHVDCserviceforthedemonstrationproject,andaftertheHVDCdemonstrationiscompleted,thelinewouldberevertedtoACservice.Thecandidateintertiesareorganizedgeographically,movingfromnorthwesttosoutheast.

H.4.2.1 DillinghamtoAleknagikACLineConversion(DemonstrationOnly)

Thisisanexisting,approximately25‐mile‐long,three‐phaseACintertiethatprovideselectricservicetoAleknagikfromNushagakElectricCooperative’sdieselgeneratorsinDillingham(FigureH‐2).ThelineisunderstoodtobeofstandardRuralUtilitiesService(RUS)construction,insulatedto34.5kilovolts(kV)butoperatedasa7.2/12.4‐kVintertie.ThisexistinglinewouldbeconvertedtoHVDCoperationforademonstrationperiod,andthenrevertedtonormalACoperationafterthedemonstrationiscompleted.

TheloadinAleknagikisnotknown.Ifitexceeds500kilovolt‐amperes(kVA),theneitheradditionalintertiecapacityordieselgeneratorsinAleknagikwouldberequired.

Theexistinginsulatorsontheintertieshouldbesufficientforserviceat50kVDC.Becausethelineisinsulatedat34.5kV(approximatelyequalto60kVDC),theremaybeissueswithbuildupofcontaminationunderastaticDCelectricfieldleadingtoarcingovertheinsulators.Ifthisbecameanissue,theinsulatorswouldneedtobecleaned.AnalysisiswarrantedtoseeiftheHVDCintertievoltageshouldbereducedtoavoidthisproblem.VoltagereductionwouldalsodecreasethepowerthroughputcapabilityoftheHVDCconverters.

H.4.2.2 EurekaACLineConversion(DemonstrationOnly)

Thisisanexisting,approximately50‐mile‐long,single‐phase,14.4‐kVdistributionlineownedandoperatedbyCopperValleyElectricAssociation,Inc.(CVEA)servingthecommunitiesandresidentswestofGlennallen,Alaska(FigureH‐3).ThedemonstrationprojectwouldconsistofconvertingasegmentofthislinetoHVDCoperationforthedemonstrationperiod,thenconvertingitbacktoACoperation.

ThegeotechnicalconditionsalongthislinearebelievedtobefavorablefortestingaSWERconfigurationinpermafrostsoilsalthoughanappropriatelinesegmentwouldneedtobeidentifiedforSWERoperation.

ThepeakloadontheHVDCsegmentofthelinewoulddependonwherethedemonstrationwouldtakeplacealongtheline.Apeakloadof167kVAorlesswouldbepreferredtoallowuseofthe500‐kVAprototypeconverters.

PreliminarydiscussionswereheldwithCVEAinFebruary2011regardingthisdemonstrationproject.Aspecificsitewasnotidentified,butCVEAwasgenerallysupportiveofhostingtheHVDCdemonstrationproject,providedthatitdidnotdamageutilityassetsornegativelyimpactcustomersandwasrevenue‐neutraltotheutility(Botulinski,privateconversation,2011).

H.4.2.3 HopeSubstationtoHopeACLineConversion(DemonstrationOnly)

Thisisanexisting,approximately20‐mile‐long,singlephase,14.4‐kVdistributionlineownedandoperatedbyChugachElectricAssociation,Inc.(CEA)servingthecommunityofHopeonTurnagainArmnearAnchorage(FigureH‐4).Hopehasapeakloadofapproximately300kilowatts(kW).CEAisplanningamultipartupgradeofthislinetoaddressreliabilityissues.Thefirstpartofthisupgradeprojectwouldrebuildandrelocateapproximately4milesoftheintertiestartingattheHopeSubstationneartheHope


MAY 2012 PAGE H-13

JunctionontheSewardHighway.CEAestimatesthatthisprojectwouldbereadyforconstructionin2013(Jenkins,privateconversation,2011).Thedemonstrationprojectwouldcoordinatewiththelineupgrade.

Thedemonstrationprojectwouldrequiretransformersoneitherendofthedemonstrationsegmenttoconvertbetween14.4kVandthe480‐VACinterfaceofthepowerconverters.Inaddition,becausethe14.4‐kVlineissinglephase,theconvertercapacitywouldbereducedbyapproximately1/3to167kVA.ThiscouldbeaddressedeitherwithincreasedconvertercapacityoroccasionaloperationoftheexistingdieselgeneratorinHopetomeetpeakloads.

CEAissupportiveofhostingtheHVDCdemonstrationproject,providedthatitdidnotdamageutilityassetsornegativelyimpactcustomersandwasrevenue‐neutraltotheutility.Whilethisintertieappearstechnicallyfeasible,lesscomplicatedHVDCdemonstrationprojectslikelyexistwithinthestate.

H.4.2.4 Homer–SeldoviaACLineConversion(DemonstrationOnly)

ThisisanexistingdistributionlineownedandoperatedbyHomerElectricAssociation,Inc.(HEA),servingthecommunitiesonthesouthsideofKatchemakBayfromHalibutCovetoSeldovia.Thelineisthree‐phase,24.9‐kVACstartinginHomer.ItcrossesKatchemakBaywitha4.5‐mile‐longcableinstalledin2001,andthencontinuesasanoverheadlinetothesouthbaycommunities(FigureH‐5).TheoverheadlineisacombinationofconventionalRUSconstructionandtreecable.Loadonthisdistributioncircuitisapproximately1,100kVA(McDonough,privateconversation,2011).

TheconceptforthisdemonstrationprojectwouldbetooperatetheexistingsubmarinecableasanHVDCcableforthedemonstrationproject.Therearetwochallengeswiththisconcept:

1. Thepeakloadonthecircuitisapproximatelytwicethecapacityoftheprototypeconverters.ThiswillrequireloadsharingbetweenHEAthroughtheHVDClinkanddieselsonthesouthsideofthecable.Thisisnotatechnicalchallenge;however,itwillresultinsignificantcoststhatthedemonstrationprojectbudgetwouldneedtoabsorb.500kWofcontinuousdieselgenerationfora6‐monthdemonstrationperiodwouldcostapproximately$700,000.Abetteralternativeatthispricemaybetobuildtwomore500kWconvertermodules,increasingtheHVDCintertiecapacityto1,000kW.

2. Theexistingsubmarinecableisonlyratedfor24.9kVAC.Thisisapproximatelyequalto43kVDC,lessthanthenominalHVDCsystemvoltageof50kV.Twopossibleremediesexistforthis.IfHEAcanbeassuredthatthecablewilloperateat50kVDCwithoutilleffect,thenthedemonstrationprojectcouldproceed.GiventhatcablesaretypicallysubjectedtoDCvoltagesontheorderof50to100kVduringacceptancetests,itseemslikelythatthiswouldbepossible.Thenatureoftheseassuranceshasnotbeendefined.ThesecondremedyistodecreasetheoperatingvoltageoftheHVDCintertie.PPShasindicatedthattheconvertersoftwarecanbeprogrammedtoreducetheDCvoltage;however,thiswilldecreasethepowerratingoftheconverters.Loweringthevoltagefrom50to40kVwouldlowerthepowerratingofaconvertermodulefromapproximately500to400kVA.

HEAissupportiveofhostingtheHVDCdemonstrationproject,providedthatitdidnotdamageutilityassetsornegativelyimpactcustomersandwasrevenue‐neutraltotheutility.Whilethisintertieappearstechnicallyfeasible,lesscomplicatedHVDCdemonstrationprojectslikelyexistwithinthestate.

H.4.3 HVDCDemonstrationProjectsonNewACDistributionLineExtensions

ThissectionprovidesoverviewsofpotentialHVDCdemonstrationprojectsthatwouldbeimplementedonpurpose‐builtACdistributionlineextensions.AftertheHVDCdemonstrationiscompleted,thelinewouldbeconvertedtoACserviceandwouldbealastingbenefittotheutilityandnewlyservedcustomers.Thecandidateintertiesareorganizedgeographically,movingnorthwesttosoutheast.


MAY 2012 PAGE H-14

H.4.3.1 GVEAPhillipsRoadLineExtension

Thisprojectwouldbeanapproximately1.75‐milesingle‐phaseoverheaddistributionextensiontoserveseveralresidencesattheendofPhillipsRoadinDeltaJunction,withintheGoldenValleyElectricAssociation,Inc.(GVEA)servicearea(FigureH‐6).ThelineextensionwouldbebuiltasastandardACdistributionline,operatedasanHVDCintertiefordemonstrationpurposes,andthenturnedovertoGVEAforsubsequentoperationasanACdistributionline.

GVEAandtheresidencesattheendofthelinewouldbothlikelycontributefundsorin‐kindservicestothelineextension.Totalcontributionisestimatedat$50,000,andthelinebuild,excludinganycostsassociatedwiththeHVDCdemonstration,isbudgetedat$140,000.Aright‐of‐waywouldneedtobeobtainedfortheproject,whichwouldtakeanestimated6to12months.

TheprojectislocatedincloseproximitytotheTrans‐AlaskaPipelineSystem,andassuchwouldlikelynotbesuitablefordemonstrationofSWERoperation.Thepeakloadoftheresidencesattheendofthelineislikelylessthantheapproximately167‐kVAcapacityofthe500‐kWprototypeconvertersinsingle‐phaseoperation.

GVEAisverysupportiveofhostingtheHVDCdemonstrationproject,providedthatitdidnotdamageutilityassetsornegativelyimpactcustomersandwasrevenue‐neutraltotheutility,beyondthein‐kindconstructioncontributionsthatGVEAofferedforthelineextension(Wright,privateconversation,2011).

H.4.3.2 GVEACummingsRoadLineExtension

Thisprojectwouldbeanapproximately4‐to6‐milesingle‐phaseoverheaddistributionextensiontoserveseveralresidencesattheendofCummingsRoadinDeltana,withintheGVEAservicearea(FigureH‐7).ThelineextensionwouldbebuiltasastandardACdistributionline,operatedasanHVDCintertiefordemonstrationpurposes,andthenturnedovertoGVEAforsubsequentoperationasanACdistributionline.

GVEAandtheresidencesattheendofthelinewouldbothlikelycontributefundsorin‐kindservicestothelineextension.Totalcontributionisestimatedat$60,000,andthelinebuild,excludinganycostsassociatedwiththeHVDCdemonstration,isbudgetedat$560,000.Aright‐of‐waywouldneedtobeobtainedfortheproject,whichwouldtakeanestimated6to12months.

Thepeakloadoftheresidencesattheendofthelineislikelylessthantheapproximately167‐kVAcapacityofthe500‐kWprototypeconvertersinsingle‐phaseoperation.

GVEAisverysupportiveofhostingtheHVDCdemonstrationproject,providedthatitdidnotdamageutilityassetsornegativelyimpactcustomersandwasrevenue‐neutraltotheutility,beyondthein‐kindconstructioncontributionsthatGVEAofferedforthelineextension(Wright,2011).

H.4.3.3 MEAtoIndependenceMineLineExtension

Thisprojectwouldbeanapproximately5.5‐mileundergroundACdistributionlinefromtheendofMatanuskaElectricAssociation,Inc.(MEA)’sexistingHatcherPassdistributionlineuptotheIndependenceMineStateHistoricalPark(StatePark)(FigureH‐8).ThelinewouldbebuiltasanACdistributionfeeder,operatedasanHVDClineforthedemonstrationproject,andthenrevertedtoACoperation.


MAY 2012 PAGE H-15

Easementsforthefirstapproximately2milesofthelineextensionarependingfromtheAlaskaDepartmentofNaturalResources(ADNR)andMatanuska‐SusitnaBorough(MSB)foraproposedhydroelectricprojectlocatedalongtheroute.42Neweasementswouldberequiredfortheremainingapproximately3.5milestotheStatePark.TheintertiewouldeliminatetheneedfordieselgenerationattheStateParkduringthesummermonths.ThehydroelectricprojectdeveloperandADNRDivisionofParksandRecreationbothmaysupportthisprojectwithmatchingfunds.

Whencontactedregardingthisproject,theStateParkwassupportive(Biessel,privateconversation,2011).Threeprivateentitieslocatedneartheparkexpressednointerestinconnectingtotheline.Whencontactedregardingthisproject,MEAexpressedconcernsaboutitsstaffavailabilitytosupportthisproject(Kuhn,privateconversation,2011).

H.4.4 HVDCIntertieProjects

ThissectionprovidesoverviewsofpotentialHVDCintertiesbetweenruralAlaskacommunities.Theintertiesareorganizedgeographically,startinginthenorthwestandmovingtothesoutheast.

H.4.4.1 BarrowtoAtqasukHVDCIntertie

This75‐mile‐longoverlandintertiewouldconnectAtqasuk,whichuseshigh‐costdieselforelectricity,toBarrow,whichgenerateselectricityfromlow‐costnaturalgas(FigureH‐9).ThisprojectcouldincludeconversionofAtqasuktoelectricheatingtoachievegreaterbenefits.TheNorthSlopeBoroughiscurrentlystudyingthisintertie.IftheHVDCtechnologyiscommerciallyavailableinatimelymanner,itcouldbeusedonthisintertie.Ifitisnot,theintertiewouldbebuiltasathree‐phaseACline.

H.4.4.2 NometoTellerandBrevigMissionHVDCIntertie

Thisapproximately75‐mile‐longoverlandintertiewouldconnectTellerandBrevigMission—whichbothgenerateelectricitywithdieselfuel—toNome,whichgenerateselectricityfromdieselandsomewind(FigureH‐10).TheAlaskaVillageElectricCooperative,Inc.(AVEC)recentlybuiltanintertiebetweenTellerandBrevigMission.IfthePilgrimHotSpringsgeothermalresourceisdevelopedandislargeenoughtosupplyNomeaswellasTellerandBrevigMission,itcouldsignificantlyreduceelectriccostsinthesevillages.

H.4.4.3 PilgrimHotSpringstoNomeHVDCIntertie

ThegeothermalresourceatPilgrimHotSpringscouldprovideelectricityforNome.Oneofthechallengeswiththisrenewableenergyconceptisthecostoftheapproximately60‐miletransmissionlinebetweenPilgrimHotSpringsandNome(FigureH‐10).UsingthisHVDCtechnologycouldreducethecostsofthisintertie,improvingprojecteconomics.OnepotentialhurdleforthisdemonstrationprojectcandidateisthatthePilgrimHotSpringsresourcehasbeententativelyestimatedat5megawatts(MW).Thisislargerthanthecapacityoftheprototypeconverters,andapproximatelyten500‐kWconverterswouldbeneededateachendoftheintertie.PPShasindicatedthatparallelingthismanyconverterstogetheristechnicallyfeasiblebutthisfunctionhasnotbeenverifiedatthistime.ACEPisassessingthegeothermalresourceatPilgrimHotSprings,whichwillhelpdeterminehowmuchpowercanbederivedfromtheresource(Mager,privateconversation,2011).

42ThedeveloperofthishydroelectricprojectisanaffiliatedinterestofPolarconsultAlaska,Inc.


MAY 2012 PAGE H-16

H.4.4.4 St.Michaels–StebbinsHVDCIntertie

Thisapproximately10‐mile‐longoverlandintertiewouldconnectSt.MichaelsandStebbins,twovillagesservedbytheAVEC,allowingAVECtoeconomizebyconsolidatingbulkfuelandgenerationassetsandoperationsatonevillage(FigureH‐11).Thereisgoodmarineaccesstobothvillages.TherelativelyshortdistanceofthisintertiereducesthesavingsofanHVDCintertiecomparedwithanACintertie.

H.4.4.5 St.Mary’stoMountainVillageHVDCIntertie

Thisapproximately26‐mile‐longoverlandintertiewouldconnectSt.Mary’sandMountainVillageontheYukonRiver,allowingAVECtoeconomizebyconsolidatingbulkfuelandgenerationassetsandoperationsatonevillage(FigureH‐12).Thereisgoodaccesstobothvillages,andanexistingroadbetweenthemwouldfacilitateconstructionoftheoverheadintertie.

H.4.4.6 DillinghamtoManokotakHVDCIntertie

Thisapproximately20‐mile‐longintertiewouldconnectManokotaktoDillingham(FigureH‐2).ThisintertiewouldallowtheDillinghamandManokotakelectricutilitiestoconsolidateoperations,loweringcostsinManokotak,andimprovingtheeconomiesofscaleforbothutilities.Inaddition,Dillinghamiscurrentlystudyingtwohydroelectricresources,LakeGrantandLakeElva,whichwouldprovidestable,low‐costelectricity.Iftheseprojectsarebuilt,ratesinManokotakwouldbesignificantlyreducedwiththisintertie.AnintertiebetweenManokotakandDillinghamhasbeenstudiedinthepast(Polarconsult,1986)buthasnotbeenconstructed.TheproposedHVDCtechnologycouldreducecostsfortheintertie,improvingprojecteconomics.

H.4.4.7 NewStuyahok–EkwokHVDCIntertie

Thisapproximately8‐mileoverlandintertiewouldconnectthesetwoAVECvillages,allowingAVECtoeconomizebyconsolidatingbulkfuelandgenerationassetsandoperationsatonevillage(FigureH‐13).TherelativelyshortdistanceofthisintertiereducesthesavingsofanHVDCintertiecomparedwithaconventionalACintertie.

H.4.4.8 Kodiak–OuzinkieHVDCIntertie

Thisapproximately8‐mile‐longsubmarinecableintertiewouldconnectOuzinkiewiththeKodiakElectricAssociation,Inc.(KEA)grid(FigureH‐14).Ouzinkiegenerateselectricitywithacombinationofhydroanddiesel.KEAgenerateselectricityfromacombinationofhydro,wind,anddiesel.DuetothedifferentgenerationsourcesandeconomyofscaleontheKEAsystem,KEA’selectricratesaresignificantlylowerthanOuzinkie’s.TheintertiewouldbenefitKEAbyincreasingloadandwouldbenefitOuzinkiebyreducingrates.KEAandOuzinkiehavealreadystudiedanoverlandintertiewithashortACcablecrossingofNarrowStrait(Dryden&Larue,2011).Theestimatedcostsoftheshortcablecrossingareasignificantportionofthetotalprojectcost,inpartduetothemobilizationcostsofspecializedequipmentforcableinstallation.Itmaybemorecost‐effectivetoinstallasubmarineHVDCcablefortheentireroute.

ThisintertieappearstobeasuitablecandidateforanHVDCdemonstrationproject.TheeconomicbenefitstoOuzinkieappeartobesignificant(Totemoff,privateconversation,2011).AsubmarineHVDCcableusingthetechnologydevelopedinthisprojectappearstobealessexpensiveoptionthantheoverhead/cablecrossingoption.Ouzinkie’speakloadisapproximately400kW,withinthecapacityoftheprototypeconverters.Furtherconversationswiththeprojectstakeholdersarewarranted.


MAY 2012 PAGE H-17

H.4.4.9 Green’sCreektoHoonahHVDCIntertie

This26‐mile‐longsubmarineintertiewouldconnectHoonahtoAlaskaElectricLightandPowerCompany(AEL&P)’sJuneaupowergrid,providinglower‐costpowertoHoonah(FigureH‐15).TheintertieisagoodlengthforHVDCandwouldprovideaclearbenefittoHoonah.Theintertiehasbeenunderconsiderationforseveralyears,andsignificantengineeringstudieshavealreadybeencompleted.TheintertieisuneconomicusingACtransmissionorexistingHVDCtechnology.TheproposedHVDCtechnologycouldreducecostsfortheintertie,improvingprojecteconomics.

H.4.4.10 PetersburgtoKakeHVDCIntertie

Thisapproximately60‐mile‐longsubmarineandoverlandintertiewouldconnectKakewiththePetersburg‐Ketchikangrid(FigureH‐16).TheintertiewouldallowKaketoconvertfromhigh‐costdieselelectricitytolow‐costhydroelectricity,andwouldbepartoftheproposedsoutheastintertiegrid.UsingHVDCcouldreducecostsbyallowinglongerspans,buriedcable,orincreaseduseofsubmarinecable.Whilea1‐MWmonopolarHVDCintertiewouldbesufficienttoserveKake,futureextensionofthesoutheastintertietoSitkaordevelopmentofnearbyhydropowerresourcescouldincreasetheloadonthisintertietotensofmegawatts.

H.4.4.11 GustavustoGlacierBayNationalParkIntertie(HVDCDemonstrationOnly)

Withthecompletionofthe800‐kWFallsCreekHydroelectricProjectin2009,Gustavusnowhasexcesshydropower.TheheadquartersofGlacierBayNationalPark,locatedapproximately5to10milesfromGustavus,continuestorelyondieselgenerationforelectricity(FigureH‐15).ConnectingtheparkheadquarterswithGustavuswouldallowtheParktoreducefuelconsumptionandoperatingcostsandwouldallowGustavustoincreaseitsratebaseandpowersales,loweringoverallrates.AburiedHVDCcablewouldbepreferabletooverheadAClinesinthepark,whereaestheticsareamajorfactor.Duetotherelativelyshortlength,anHVDCintertiemaynotbecost‐effectivecomparedtoanACintertie.


MAY 2012 PAGE H-18

H.4.5 ProjectMaps

Figure H-2 Vicinity Map for Demonstration Projects near Dillingham


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Figure H-3 Vicinity Map for Eureka AC Line Conversion


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Figure H-4 Vicinity Map for Hope AC Line Conversion


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Figure H-5 Vicinity Map for Seldovia AC Line Conversion


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Figure H-6 Vicinity Map for Delta Junction AC Line Extension


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Figure H-7 Vicinity Map for Deltana AC Line Extension


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Figure H-8 Vicinity Map for Independence Mine AC Line Extension


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Figure H-9 Vicinity Map for Barrow – Atqasuk HVDC Intertie


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Figure H-10 Vicinity Map for Demonstration Projects near Nome


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Figure H-11 Vicinity Map for St. Michaels – Stebbins HVDC Intertie


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Figure H-12 Vicinity Map for St. Mary’s – Mountain Village HVDC Intertie


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Figure H-13 Vicinity Map for New Stuyahok – Ekwok HVDC Intertie


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Figure H-14 Vicinity Map for Kodiak – Ouzinkie HVDC Intertie


MAY 2012 PAGE H-31

Figure H-15 Vicinity Map for Gustavus and Hoonah HVDC Interties

Figure H-16 Vicinity Map for Kake – Petersburg HVDC Intertie


MAY 2012 PAGE H-32



MARCH 2012 PAGE I-1

APPENDIXI

STAKEHOLDERADVISORYGROUPINVOLVEMENTANDMEETINGS


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MARCH 2012 PAGE I-3

TABLEOFCONTENTS

I.1 INTRODUCTION........................................................................................................................................................7

I.2 LISTOFSAGMEMBERS.........................................................................................................................................8

I.3 SUMMARYOFSAGROLEANDPOLICIES.......................................................................................................9 I.3.1 POLICIESANDPROCEDURES............................................................................................................................................9

I.3.1.1 Formation......................................................................................................................................................9 I.3.1.2 ScheduledMeetings...................................................................................................................................9 I.3.1.3 Organization.................................................................................................................................................9 I.3.1.4 Communication...........................................................................................................................................9 I.3.1.5 Termination................................................................................................................................................11

I.4 STAKEHOLDERADVISORYGROUP(SAG)MEETINGPRESENTATIONMATERIALS.................12 I.4.1 SAGMEETING#1–FAIRBANKS,ALASKA(APRIL27,2010)................................................................................12 I.4.2 SAGMEETING#2–ANCHORAGE,ALASKA(JANUARY14,2011)........................................................................32 I.4.3 SAGMEETING#3–ANCHORAGE,ALASKA(OCTOBER25,2011).......................................................................53

I.5 HANDOUTSFROMOTHERMEETINGSCONDUCTEDDURINGTHEPROJECT...........................105 I.5.1 SOUTHEASTCONFERENCEMID‐SESSIONSUMMIT–JUNEAU,ALASKA(MARCH2,2010)............................107 I.5.2 EMERGINGENERGYTECHNOLOGYFORUM–JUNEAU,ALASKA(FEBRUARY14,2011).................................113 I.5.3 BROWN‐BAGWORKSESSION–ANCHORAGE,ALASKA(AUGUST29,2011)...................................................125 I.5.4 HVDCCONVERTERDEMONSTRATION–LAWRENCEVILLE,NEWJERSEY(NOVEMBER14,2011).............145

I.6 ADDITIONALMEETINGS.................................................................................................................................151


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MARCH 2012 PAGE I-5

LISTOFTABLES

TableI‐1 ListofSAGMembers.................................................................................................................................8

TableI‐2 SummaryofCorrespondencewithSAGMembers......................................................................10


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MARCH 2012 PAGE I-7

I.1 INTRODUCTION

ThisappendixprovidesthefollowingdetailedinformationregardingtheStakeholdersAdvisoryGroup(SAG)formedforPhaseIIoftheHigh‐VoltageDirectCurrent(HVDC)DevelopmentProgram:

● ListofSAGmembers;

● SummaryofSAGroleandpolicies;

● SummaryofkeyinformalcorrespondencebetweenSAGmembersandPolarconsultoverthecourseoftheproject;

● HandoutsandtranscriptsfromthethreeSAGmeetings;and

● Handoutsfromothermeetingsandoutreachactivitiesconductedoverthecourseoftheproject.

Meetingtranscriptsareavailableseparately.


MARCH 2012 PAGE I-8

I.2 LISTOFSAGMEMBERS

Table I-1 List of SAG Members

Company First Name Last Name Position

Denali Commission Denali Daniels SAG Chair Alaska Center for Energy and Power (ACEP) Gwen Holdmann ACEP Director Alaska Center for Energy and Power (ACEP) Jason Meyer ACEP Project Manager Alaska Center for Energy and Power (ACEP) Brent Sheets SAG Member Polarconsult Alaska, Inc. Joel Groves Project Manager Polarconsult Alaska, Inc. Earle Ausman President Polarconsult Alaska, Inc. David Ausman Vice President Princeton Power Systems, Inc. (PPS) Darren Hammell Executive Vice President Alaska Department of Labor (AKDOL) Daniel Greiner Alt. SAG Member Alaska Department of Labor (AKDOL) Alvin Nagel SAG Member Alaska Division of Community and Regional Affairs (DCRA) Percy Frisby SAG Member Alaska Energy Authority (AEA) David Lockhard SAG Member Alaska Power & Telephone Company (APT) Bob Grimm SAG Member Alaska Power Association (APA) Marilyn Leland SAG Member Alaska Village Electric Cooperative, Inc. (AVEC) Meera Kohler SAG Member Alaska Village Electric Cooperative, Inc. (AVEC) Brent Petrie Alt. SAG Member Bering Straits Native Corporation (BSNC) Jerald Brown SAG Member Bethel Electric Utility (BEC) Bob Charles SAG Member Copper Valley Electric Association (CVEA) Robert Wilkinson SAG Member Dillingham Nels Andersen SAG Member Golden Valley Electric Association, Inc. (GVEA) Brian Newton SAG Member Homer Electric Association, Inc. (HEA) Brad Janorschke SAG Member Inside Passage Electric Cooperative (IPEC) Jodi Mitchell SAG Member Institute of Northern Engineering (INE, UAF) Ron Johnson SAG Member Kodiak Electric Association, Inc. (KEA) Darron Scott SAG Member Kotzebue Electric Association, Inc. (KoEA) Brad Reeve SAG Member Matanuska Electric Association (MEA) Joe Griffith SAG Member Matanuska Electric Association (MEA) Trivia Singaraju Alt. SAG Member Naknek Electric Association, Inc. (NEA) Donna Vukich SAG Member Nat’l. Rural Electric Cooperative Association (NRECA) Tom Lovas SAG Member Nome Chamber of Commerce (NCC) Mitch Erickson SAG Member Nome Joint Utilities (NJUS) John Handeland SAG Member North Slope Borough (NSB) Kent Grinage SAG Member Northwest Arctic Borough (NWAB) Ingemar Mathiasson SAG Member Nushagak Electric Association Mike Favors SAG Member Nuvista Light and Power, Inc. (NLP) Bob Charles SAG Member Southeast Conference (SEC) Robert Venables Alt. SAG Member Southeast Conference (SEC) Shelly Wright SAG Member Southwest Alaska Municipal Conference (SWAMC) Andy Varner SAG Member U.S. Department of Agriculture (USDA) Rural Utilities Service (RUS) Eric Marchegiani SAG Member University of Alaska Fairbanks (UAF) Richard Wies SAG Member


MARCH 2012 PAGE I-9

I.3 SUMMARYOFSAGROLEANDPOLICIES

I.3.1 PoliciesandProcedures

TheSAGisanadvisorybodycomprisedofrepresentativesofAlaska’sruralelectricutilityindustryandrelatedprofessionals.ThepurposeoftheSAGistoprovidecomments,feedback,review,andrecommendationstotheHVDCDevelopmentProgram,awardedbytheDenaliCommission(Commission),managedbytheAlaskaCenterforEnergyandPower(ACEP),andcontractedtoPolarconsultAlaska,Inc.(Polarconsult).

I.3.1.1 Formation

TomaintainindependenceoftheSAG,ACEPidentifiedmembersforparticipation,withconsiderationofrecommendationsfromPolarconsultandtheDenaliCommission.AfinalcandidatelistwassentoutforcommenttoPolarconsultandforwardedforapprovaltotheDenaliCommission.

I.3.1.2 ScheduledMeetings

PerthescopeofworkunderUAF–PolarconsultContract#10‐0055,theSAGformallyconvenedthreetimesoverthecourseoftheHVDCProject.Perthescopeofworkandbudget,thecostofconveningthesemeetingswastheresponsibilityofPolarconsult.Fundingformembertravelandparticipationcostswasnotprovided.Themeetingswereconvenedinamannerconducivetoremoteparticipationofmembers.ThemeetingdateswereApril28,2010;December1,2010;andJuly15,2011.

TheagendaforthesemeetingswassetbyACEP,withinputfromPolarconsultandtheDenaliCommissionandfinalapprovalbytheDenaliCommission.

I.3.1.3 Organization

TheSAGshallconsistoftheChair(theDenaliCommission)andmembers.TomaintainequalityontheSAG,individualorganizationsmayholdonlyonememberposition.Upto30SAGmemberswillbeallowed,thefinalnumberdeterminedbasedonthelevelofinterest.Ifatanytimeoverthecourseoftheprojectoneofthemembersresignsorisnolongeractive,ACEPwillinviteanotherindividualtofillthisposition,withtheapprovaloftheDenaliCommission.Membersmaydesignateproxiesfromwithintheirorganizationtoattendmeetings.

ACEPencouragesorganizationsandindividualsnotselectedfortheSAGtoparticipateinformallyinthisproject.Publiccommentisalwayswelcomeandane‐maillistandforumwillbemadeavailableontheACEPprojectwebsite.

I.3.1.4 Communication

Atcertainprojectmilestones,oruponrecommendationfromACEP,Polarconsultshallsolicitcomments,review,andrecommendationstotheHVDCprogram.AllformalcommunicationbetweenPolarconsultandtheSAGshallbethroughtheChair,withinclusionofACEP.PolarconsultisfreetocontactthewholeSAGformallyorcontactindividualSAGmembersinformally,astheneedarises.AllinformalcommunicationwillnotrepresenttheadviceorrecommendationsoftheSAG.Intheinterestsofpromotingmaximumfeedbackfromtheindustry,confidentialcommunicationswillbeacceptedwherethereisademonstratedneedtomaintainconfidentiality.

TableI‐2providesasummaryofcorrespondencewithSAGmembersrelatedtothisproject.


MARCH 2012 PAGE I-10

Table I-2 Summary of Correspondence with SAG Members

Date SAG Member Participants Subject Summary

Jan.–Feb. 2010 MEA

Trivi Singaraju (MEA) Gary Kuhn (MEA)

Joel Groves (Polarconsult)

Demonstration Project Sites

Discussing potential HVDC demonstration project sites.

Jan.–Feb. 2010 CVEA Chris Botulinski (CVEA)

Earle Ausman (Polarconsult) Demonstration Project Sites


Jan.–March 2010

At Large Citizen

Nels Anderson Earle Ausman (Polarconsult)



Jan.–March 2010 CEA

Ed Jenkin (CEA) Dave Ausman (Polarconsult) Joel Groves (Polarconsult)

Earle Ausman (Polarconsult)



Jan.–March 2010 HEA

Brad Zubeck (HEA) Kathy McDonough (HEA) Joel Groves (Polarconsult)



May–June 2010 NWAB Ingemar Mathiasson (NWAB)


International examples of

electric codes

Mr. Mathiasson used his contacts in Sweden to request examples of international electric codes with

regard to SWER circuits, HVDC, and related rural electric issues.

July–October

2010 AVEC

Brent Petrie (AVEC) Bill Thomson (AVEC) Mark Tietzel (AVEC)

Joel Groves (Polarconsult) Earle Ausman (Polarconsult)

HVDC Converter Specification

Discussions and comments from AVEC on draft specification for

HVDC power converter.

July–October

2010 UAF/ACEP

Richard Wies (UAF) Jason Meyer (ACEP)


HVDC Converter Specification

Discussions and comments from AVEC on draft specification for

HVDC power converter.

August 2010 AVEC Mark Teitzel (AVEC) Joel Groves (Polarconsult)

Conceptual Design of

Overhead Line

Request for examples of environmental loadings used on

previous AVEC interties, performance of these projects.

September 2010 IPEC Peter Bibb (IPEC)

Joel Groves (Polarconsult) Demonstration Project Sites


October–November

2010 GVEA

Mike Wright (GVEA) Searl Burnett (GVEA)


Conceptual Design of

Overhead Line

Site visit to review design, performance, and failure modes of

guyed Y and X towers on transmission lines between

Fairbanks and Healy.

November 2010 AVEC

Brent Petrie (AVEC) Joel Groves (Polarconsult)




December 2010 SEC

Shelly Wright (SEC) Robert Venables (SEC)




January 2011 APT

Bob Grimm (APT) Earle Ausman (Polarconsult) Joel Groves (Polarconsult)





Date SAG Member Participants Subject Summary

January 2011 NWAB

Ingemar Mathiasson (NWAB) Brent Petrie (AVEC)




January 2011 RUS Eric Marchegiani (RUS)

Joel Groves (Polarconsult) Demonstration Project Sites


January 2011 Multiple Multiple SAG Members Demonstration

Project Sites

Teleconference with SAG members on HVDC demonstration project

sites.

January–March 2011 GVEA

Mike Wright (GVEA) Joel Groves (Polarconsult)




March 2011 AVEC

Bill Thomson (AVEC) Joel Groves (Polarconsult)

Earle Ausman (Polarconsult) Randy Wachal (MHRC)

HVDC Controls and integration

Discussions among Polarconsult, Manitoba, and AVEC on system controls and integration needs.

May–June 2011 CVEA

Chris Botulinski (CVEA) Earle Ausman (Polarconsult) Joel Groves (Polarconsult)

HVDC Test Site Discussions looking for a test site for HVDC pole and foundations.

June 2011 UAF

Richard Wies (UAF) Jason Meyer (ACEP)


Examples of cold regions design for overhead HVDC

Visit of Chinese delegation regarding design of HVDC line across the

Tibetan Plateau.

June–July 2011 GVEA

Mike Wright (GVEA) Joel Groves (Polarconsult)

Earle Ausman (Polarconsult) HVDC Test Site Discussions looking for a test site for

HVDC pole and foundations

July 2011 AKDOL

Al Nagel (AKDOL) Dave Greiner (AKDOL) Randy Wachal (MHRC)


SWER circuit safety.

Discussions with Alaska Department of Labor regarding HVDC SWER

circuits and soliciting comments on the SWER analysis prepared by

Manitoba.

November 2011 AVEC Pam Lyons (AVEC)

Joel Groves (Polarconsult) Converter

Shipping Cost

AVEC assistance on obtaining shipping costs to move prototype

converters to Alaska.

Nov, 2011 – Jan 2012 AVEC

Meera Kohler (AVEC) Mark Tietzel (AVEC) Brent Petrie (AVEC)


Cost data for past AC projects

Discussions from November 2011 through January 2012 regarding details of cost data for remote

Alaska AC intertie projects built over the past decade.

December 2011 AKDOL

Al Nagel (AKDOL), Dave Greiner (AKDOL), Jason

Meyer (ACEP), Joel Groves (Polarconsult)

SWER circuit safety.

Discussions with Alaska Department of Labor regarding HVDC SWER

circuits and NESC code.

I.3.1.5 Termination

TheSAGshallbeformallyterminatedupontheendoftheprojectissuedfromtheDenaliCommission.



I.4 STAKEHOLDERADVISORYGROUP(SAG)MEETINGPRESENTATIONMATERIALS

I.4.1 SagMeeting#1–Fairbanks,Alaska(April27,2010)



I.4.2 SAGMeeting#2–Anchorage,Alaska(January14,2011)



I.4.3 SAGMeeting#3–Anchorage,Alaska(October25,2011)



I.5 HANDOUTSFROMOTHERMEETINGSCONDUCTEDDURINGTHEPROJECT



I.5.1 SoutheastConferenceMid‐SessionSummit–Juneau,Alaska(March2,2010)



I.5.2 EmergingEnergyTechnologyForum–Juneau,Alaska(February14,2011)



I.5.3 Brown‐BagWorkSession–Anchorage,Alaska(August29,2011)



I.5.4 HVDCConverterDemonstration–Lawrenceville,NewJersey(November14,2011)



I.6 ADDITIONALMEETINGS



ThefollowingadditionalmeetingswereheldduringthecourseofthisprojectregardingaHVDCtransmissionsysteminruralAlaska.

● SoutheastConferenceMid‐SessionSummit–Juneau,Alaska(MARCH2,2010)

● EmergingEnergyTechnologyForum–Juneau,Alaska(February14,2011)

● Brown‐BagWorkSession–Anchorage,Alaska(August29,2011)


MARCH 2012 PAGE J-1

APPENDIXJ

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