32037922 switch yard equipments switching schmes layouts

8/6/2019 32037922 Switch Yard Equipments Switching Schmes Layouts

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EHV SWITCHYARD

EQUIPMENTS, SWITCHINGSCHMES & LAYOUTS


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Switchyard Type

Conventional Air Insulated Type.

Gas Insulated type.

Outdoor Gas Insulated type.


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Selection of Bus Switching Scheme

PRE-REQUISITES

1)System security2)Operational flexibility

3)Simplicity of protection arrangements

4)Ability to limit short circuit levels (ease ofsectionalizing)

5)Maintenance Its effect on systemsecurity

6)Ease of extension

7)Total land area

8)cost


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DESIGN GUIDELINES CONTD

OPTIONS/ALTERNATIVES

1)Single sectionalised bus

2)Main and transfer bus

3)Sectionalised Main bus with transfer bus

4)Sectionalised double main and transferbus

5)Double Bus Scheme

6)Ring bus

7)One and a half breaker

8)Double bus, double breaker


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CONTD

DESIGN PRACTICES/PHYLOSOPHY

1) Consideration in Selection of Bus

Switching Scheme

2) Comparison ofSchemes

a)Sectionalized main bus with transfer bus(Scheme-I)

b)Sectionalized double main andtransfer bus (Scheme-II)

c) One and a half breaker (Scheme-III)


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DISCUSSIONS OF SCHEMES

SCHEME1

Main and Transfer Bus Scheme


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SCHEMES CONTD

SCHEME 2

Sectionalised Double Main and Transfer Bus Scheme


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SCHEMES CONTD

SCHEME 3

One and Half Breaker Bus Scheme


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SystemSecurity(Reliability

i) feeder fault

ii) Bus fault

iii)Redundancy indesign

Main & Transfer

i) requireoperation ofone breaker

ii) supply wouldbe interrupted

until all thefeeders aretransferred tothe healthy bus

iii) No alternatepath

(Offline

redundancyavailable)

Double Main &Transfer

i) requireoperation of

one breaker

ii) supply wouldbe interrupteduntil all thefeeders aretransferred tothe healthy bus

iii) No alternatepath

(Offlineredundancyavailable)

One & HalfBreaker

i)requireoperation oftwo breakers

ii) continuity ofsupply is

maintainedbecause eachcircuit gets fedthrough twopaths

iii) Alternatepath is

available(Onlineredundancyavailable)


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OperationalFlexibility:

SimplicityofProtectionArrangements

AbilitytolimitShortCircuitLevels (Easeof

Sectionalizing)

Switching operation

to take out the

breaker from the bay

more extensive

Protectionarrangementinvolves AC &DC

switching .

Sectionalising ofbus bars or

introduction ofreactors in buseswith a view tolimit short circuitlevel is adoptable.

Switching operation

to take out the

breaker from the

bay more extensive

Protectionarrangementinvolves AC &DCswitching & bus

differentialprotection iscomplicated as itinvolves CTswitching.

Sectionalising of

bus bars orintroduction ofreactors in buseswith a view tolimit short circuitlevel is adoptable.

A breaker can be

taken out of service

without the need for

additional switching

Protectionarrangement issimplified as noAC &DCswitching involve

and Busdifferentialprotection issimple.

Sectionalising ofbus bars or

introduction ofreactors in buseswith a view tolimit short circuitlevel is adoptable.


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Easeofextension

Totallandarea

Cost

Switchyard shallbe suitable forfuture extensionwithout loss of

feeders. Thisscheme isflexible for suchfuture additions

This schemeoccupy more orless the sameland area as ofthe other twoschemes.

one breaker perfeeder isrequired




one breaker perfeeder isrequired




Three breakerper 2 feeder isrequired


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Switchyard layout

Objective:

Substation layout consists essentially inarranging a number of switchgear

components in an orderly pattern governed bytheir function and rules of spatial separationas described in electrical single line diagram.

Pre-requisites:

1) single line diagram

2) general layout plan of power plant

3) orientation of line evacuation

4) control room building


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LAYOUT CONTD

Options/Alternatives

The layout will vary for the

following:1) Switching schemes

2) Type of insulation - AirInsulated/Gas Insulated.


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LAYOUT CONTD

DesignPhilosophy/Practice

1)Space around the switchyard

2)Switchyard location3)Switchyard fencing.

4)Clearance.

i) phase to earth clearance

ii) phase to phase clearanceiii) section clearance

iv) ground clearance


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TABLE I: INSULATION LEVELS & CLEARANCE

REQUIREMENTS AT DIFFERENT VOLTAGE LEVELS

NOMINA

L

SYSTEM

VOLTAG

E

KV

INSULATION LEVELS HIGHESTSYSTEM

VOLTAGE

KV

MINIMUM CLEARANCE GROUNDCLEARA

NCE

(MM)

SECTIONAL

CLEARA

NCE

(MM)

HEIGHTOF

SUPPOR

TS (mm)LIGHTNING

IMPULSE

LEVEL

(kVp)

SWITCHING

SURGE

LEVEL

(kVp)

POWER

FREQUEN

CY

IMPULSE

LEVEL

(kVrms)

BETWEEN

PHASE

AND

EARTH

(MM)

BETWE

EN

PHASES

(MM)

33

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132

220

400

765

170

325

650

1050

1425

2100

-

-

-

-

1050

1550

70

140

275

460

630

830

36

72.5

145

245

420

800

320

630

1300

2100

3500

6400

320

630

1300

2100

4000

9400

3700

4000

4600

5500

8000

--

2800

3000

3500

4300

6500

10300

2500

2500

2500

2500

2500

2500


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Clearance contd

5)Equipmentspacing

a) Ease of maintenance/removal ofequipment.

b) Equipment foundation & theircable trenches.

c) Distance between LA andequipment based on theprotection reach of LA.

d) The spacings are generally keptin order to achieve

various clearances specified

at Table-I.


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Clearance contd

6) Busbars:The bus bars of 400 kV switchyard are generally made up 4 IPSaluminum tube or Quad Moose rated for 3000 A.The bus bars of 220/132kV switchyard are generally made up of 3 IPSaluminum tube or quad/ twin moose conductor. Bus bars are placed atright angles to the feeders for tapping the power.

7)Equipment Interconnection

8)Spacer spans and locations

9) Connection Level

10) Land &Road Layout

11)Sequence and mounting of line traps


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Clearance contd.

12) Control Room Layout

13) Lighting System

14) Cabling Philosophy

15) Gravel Filling

16)Earthing System

17) Lightning Protection System


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EVOLVING A SUBSTATION

LAYOUT

LAYING OUT A SUBSTATION INVOLVESSTEP-BY-STEPPROCEDURE. MOST IMPORTANT POINTS TO BECONSIDERED ARE BRIEFLY DESCRIBED BELOW:

THE IMPORTANT ELECTRICAL PARAMETERS AREESTABLISHED BY THESYSTEMDESIGN. THEMAINPARAMETERS ARE:

1) THE VOLTAGE AND BASIC INSULATION LEVEL ORSWITCHING SURGE LEVEL., THESITE AND CLIMATICCONDITIONS, THEMETHOD OF CIRCUIT CONNECTION,

ANDSWITCHING OVER-VOLTAGE CONDITIONS.

2) THE BUS BARSYSTEMDIAGRAM, THE NUMBER OFCIRCUITS AND THEIRPURPOSE I.E. THE CONTROLOF GENERATORS, TRANSFORMERS, FEEDERS, ETC.

THEDIAGRAMSHOULD INCLUDEDETAILS OF

EXTENSIONS AND FUTURE CONVERSION TO ADIFFERENT BUS BAR SYSTEM, IF INTENDED.


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EVOLVING A SUBSTATION

LAYOUT

1) THE CONTINUOUS CURRENT RATING OF THE BUS BARSAND CIRCUITS.

2) THESHORT CIRCUIT RATING OF BUS BARS ANDEQUIPMENTS.

3) PARTICULARS OF REACTORS, NEUTRAL EARTHINGEQUIPMENT ANDREACTING, InterconnectingTransformers REQUIRED.

4) METHOD OF CONNECTION OF CIRCUITS, WHETHER BYOVERHEAD LINES OR BY CABLES.

5) DETAILS OF LIGHTNING PROTECTION EQUIPMENT.

6) DETAILS OF PROTECTIVEEQUIPMENT, DETERMININGTHE INSTRUMENT TRANSFORMERSREQUIREMENTS,CARRIER CURRENT EQUIPMENT ETC.


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PREPARATION OF BASIC

LAYOUT

WHILEMEETINGALLTHE NEEDSESTABLISHEDTHEFOLLOWINGIDEALSSHOULD BEAIMEDATIN MAKINGTHEBASICCIRCUITLAYOUT.

MINIMUMGROUNDAREA

MINIMUMQUANTITIES OF CONDUCTOR, JOINTSANDSTRUCTURE

MINIMUM NUMBER OF INDEPENDENTINSULATORS,ESPECIALLYIN THE BUS BAR ZONE.

AFTERHAVINGDETERMINEDTHEELECTRICALCLEARANCE BE

USEDAROUGHCIRCUITLAYOUTISMADE. SEVERALPOSSIBLEALTERNATIVESAREPREPARED FROM WHICHTHEMOSTSUITABLE ONE WILL BESELECTED. SOMEVARIATIONIS NEEDED,TO MEETTHEREQUIREMENTS OF DIFFERENTTYPES OF CIRCUIT.

ITISALSO NECESSARYTO CALCULATESHORTCIRCUITANDATMOSPHERIC FORCESTO DETERMINETHESTRESSESIN

CONDUCTORS,INSULATORSANDSTRUCTURES. THESEHELDIN DECIDINGTHEMOST OPTIMUMDIMENSIONS.


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PURPOSE OF EARTHING

THE OBJECT OF EARTHING IS TO MAINTAIN ALOW POTENTIAL ON ANY OBJECT.

THEP

URP

OSE OF A EARTHING SYSTEM IN ASUBSTATION AREA IS TO LIMIT THEPOTENTIALGRADIENT WITHIN AND IMMEDIATELY OUTSIDETHE AREA IS A VALUE, SAFE FOR THE WORKINGPERSONNEL. SAFETY IS TO BEENSURED UNDERNORMAL AS WELL AS ABNORMAL OPERATING

CONDITION.


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REQUIREMENTS OF A GOOD

EARTHING SYSTEM

FOLLOWING BASIC REQUIREMENTS ARE TO BESATISFIEDSO AS TOENSURE A PROPER ANDSOUNDEARTHING SYSTEM.

1) THEEARTHRESISTANCE FORTHESWITCHYARDAREASHOULD BELOWERTHAN ACERTAIN LIMITING VALUERAIN ORDER TO ENSURETHATA SAFEPOTENTIAL

GRADIENTISMAINTAINEDIN THESWITCHYARDAREAANDPROTECTIVERELAYEQUIPMENT OPERATESATISFACTORILY. FORMAJORSWITCHYARDSANDSUBSTATIONSIN INDIA,THISLIMITINGVALUE OF EARTHRESISTANCE (RA)ISTAKEN TO BELESSTHAN 0.5 OHM.

2) THEGROUNDINGCONDUCTORMATERIALSHOULD BECAPABLE OF CARRYINGTHEMAXIMUMEARTH FAULT

CURRENT WITHOUT-OVERHEATINGANDMECHANICALDAMAGE. THEMAXIMUM FAULTLEVELIN THE 400 KVSYSTEMHAS BEEN ESTIMATEDTO BE 40 KAANDTHISVALUE OF FAULTCURRENTTO USEDISTHEDESIGN OFEARTHMAT FORTHE 400 KVSUBSTATION.


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REQUIREMENTS OF A GOOD

EARTHING SYSTEM

ALL METALLIC OBJECTS WHICH DO NOT CARRYCURRENT AND INSTALLED THESUBSTATION SUCHASSTRUCTURES, PARTS OF ELECTRICALEQUIPMENTS, FENCES, ARMOURING ANDSHEATHSOF THE LOW VOLTAGEPOWER AND CONTROL

CABLESSHOULD BE CONNECTED TO THEEARTHING ELECTRODESYSTEM.. THEDESIGN OF THE GROUND CONDUCTOR

SHOULD TAKE CARE OF THEEFFECT OFCORROSION FOR THE TOTAL LIFESPAN OF THEPLANT.


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Switchyard Equipments.

Circuit Breaker.

Disconnectors (Isolators)

Current Transformers. Capacitor Voltage Transformers

(CVT).

Lightning Arrestors.

Post Insulators. Wave Traps


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General Parameters

Dielectric Parameters .(IEC 694)

- Power Frequency Voltage.

- Lightning Impulse Voltage.- Switching Impulse Voltage.

- Corona Extinction Voltage.

- RIV Level.


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General Parameters (Contd.)

Rated Current.

Short Time Current.

Creepage Distance.


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Circuit Breakers Type (IEC: 62271-100)

MOCB.

ABCB.

SF6

Rated operating duty cycle- O-0.3 sec-

CO-3 min.-CO Operating mechanism

Total Break Time

Pre Insertion Resistor ( 300-450)


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Disconnectors

HCB Type.

Double Break Type.

Pantograph type. Vertical Break type.

Provision ofEarth Switches.

Motor / manual operated. Gang operated/Single pole type.


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Current Transformer ( IEC 0044, IS

2705)

Dead tank/Live tank type.

Bar Primary type.

Ring Type.

No. of Cores.

Ratio.

Accuracy.

rated primary current

Rated burden for metering

Knee Point voltage


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Capacitor Voltage Transformer (IEC

0044, IS 56)

Capacitance.

Voltage Ratio.

No. Of Cores. Accuracy.

Output Burden

Rated Secondary Voltage


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Lightning Arrestor ( IEC 60099)

Gap Type / Gapless Type.

Voltage Rating.

Energy Capability. Monitoring.

Location.

Nominal Discharge Current.


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Post Insulators

Voltage Rating.

Cantilever Strength.

Fixing Details.


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Wave Trap (IEC 60353)

Rated Inductance(0.5/1.0 mH).

Rated current.

Band Width. Coupling (Phase to Phase).


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SWITCHYARD AUXILIARY SYSTEMS

CONTROL ROOM

HVAC FORCONTROL ROOM

A RELIABLE 415V AC SUPPLY ( LT SWGR)

220 V & 48 V DC SUPPLY( BATTERY &BATTERY CHARGER)

POWER & CONTROL CABLE

LIGHTING ( Yard lighting & indoor lighting of

control room) Other items-Clamps, connectors , Insulator strings ,

BMK etc.


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192

69 ~10%400kV GIS

275kV GIS

Trfr

Trfr 2 Trfr3 Trfr4 SVC Trfrs

400kV AIS

275kV AIS

COMPARASON BETWEEN AIS ANDGIS SUBSTATION

FOOTPRINT FOR HECTOR


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INDOORGIS


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OUTDOORGIS - SEISMIC AREAS


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Conductor

Phase Spacing

PHASE SPACING


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OVERHEAD STRUNG BUSBARS


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9,81.mi

fs

SAGDUE TO CONDUCTOR

fs = 9,81.mi.Lc2

8.T

fs = maximum conductor sag (m)

mi = mass of conductor (kg/m)

Lc = conductor span length (m)

T = tension per conductor (N)

T

Lc


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LOW PROFILE SUPPORTEDTUBULAR BUSBAR SUBSTATIONS


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TUBE SAG EXCESSIVE INCORRECTLY SELECTED


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TYPICAL TUBULAR BB BUS SECTION BAY


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MMM

Attraction Repulsion

CANTILEVER FORCES DUE TO FAULT CURRENT

COMBINATION SUPPORT STRUCTURE FOR 3 PHASES


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F S

TUBE

TUBULAR BUSBAR EXPANSION CLAMP


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TRANSFORMER FIRE AT MINERVA


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Upgradation of transmission voltage

from 400kV AC to 765kV AC.

Presently the highest AC Transmission voltage is 400kV only.NTPC is fully geared up for implementing next AC voltage of765kV.

Advantages: Step up from generation voltage to 765kV.

High Capacity Transmission to the order of 2500MW per linewith lower right of way requirement. 765kV Transmission system is techno economically better

option whenever power transmission system requires multipoint tapping at various location for catering the loadrequirement of high growth area.

765kV system offers low transmission losses, resulting inhigher utilisation of generating capacity and optimises the

resource required for capacity addition.


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((((


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ADOPTION OF CONTROLLED SWITCHING OF TRANSFORMER AND

REACTORS.

Switching of transformer, shunt reactors, capacitors and uncharged overhead

lines is normally a 'three phase' process, where all three phases are switched

simultaneously. The actual circuit closing or opening instant is left up to

chance. This results in high inrush currents or switching surges causing undue

repercussions to switchgear equipment and networks system. For overcoming

this the switching in and out is done at desired point on wave so that theovervoltages are reduced.


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765KV CIRCUIT BREAKER


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THANK YOU!

32037922 switch yard equipments switching schmes layouts

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