tranformers manufacturing

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A word i trasormatio 6Power below the waves 33Trasormig idustr 45Sustainable and available 64

Special ReportTransormers

reviewABB The corporatetechnical journal


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2 ABB review special report

Trasormers are essetia pieces oeectrica equipmet that hep to trasmitad distribute eectricit eiciet adreiab. The aso hep maitai powerquait ad cotro, ad aciitate eectri-ca etworks. ABB is a goba eader i

trasormer techoogies that eabeutiit ad idustr customers to improvetheir eerg eiciec whie owerigevirometa impact. Our ke techoo-gies icude sma, medium ad argepower trasormers, as we as tractioad other specia-purpose uits adcompoets. I this specia report oABB Review, we preset some o theatest deveopmets ad iovatios romour wide rage o trasormers adcompoets, which ca be oud acrossthe etire power vaue chai ad arecritica compoets o the grid.


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Contents

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A word i trasormatioABB is the wor lds largest transormer manuacturer andservice provider

A egac o trasormatioABB is a leader in voltage and power breakthroughs

UHVDCMeeting the needs o the most demanding powertransmission applications

Respodig to a chagig wordABB launches new dry-type transormer products

The quiet ieABBs ultralow-noise power transormers

Power beow the wavesTransormers at depths o 3 km

Shrikig the corePower electronic transormers break new ground intransormation and transportation

Baace o powerVariable shunt reactors or network stability control

Workhorses o idustrIndustrial transormers in a DC environment

Smart trasormerTransormers wil l have to do a lot more than just convertvoltages

Composig with compoetsInnovative and high quality transormer components andservices or diverse needs

Sustaiabe ad avaiabe

Enhancing perormance and reducing environmentalimpact o existing transormer leets

Gree-R-TraoSaety makes a green transormation

Chagig tredsNew technologies or the evolving grid

Transormerapplications

Trends intransormation

Transormers intransormation

3Cotets


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ABB review special report4

Markus HeimbachHead o Transormers business unit

Berhard JuckerHead o Power Products division

Dear Reader,The commercial appl icat ion history o trans-ormers dates back to the end o the nine-teenth century. The worlds irst ull AC powersystem, built by William Stanley, was demon-strated using step-up and step-down trans-ormers in 1886. The transormer played acritical role in the outcome o the so-calledwar o currents, tilting the balance in avor o

Teslas AC vision. ABB (then ASEA) de liveredone o the worlds irst transormers in 1893,

integrating it with the irst commercial three-phase AC power transmission link anothero the companys innovations connectinga hydropower plant with a large iron-ore minein Sweden.

Today, with a presence in over 100 countries,more than 50 transormer actories and30 service centers, ABB is the worlds largesttransormer manuacturer and service providerwith an unparalleled global installed base anda vast array o power, distribution and special

application transormers. These transormerscan be ound wherever electricity is gener-ated, transported and consumed in powerplants and substations, industrial complexes,skyscrapers and shopping malls, ships and oilplatorms, locomotives and railway lines, windparks, solar ields and water treatment plants.

Their most important unction is to t ransormor adapt voltage levels, stepping them up orlong-distance high-voltage transmission romthe power plant, and stepping them down or

distribution to consumers. ABB transormerscontribute to grid stability and power reliability,while ensuring the highest saety standardsand striving to increase energy eiciency andreduce environmental impact.

Besides setting new records in transormerpower ratings or both AC and DC trans-mission, ABB has pioneered a number oinnovative transormer solutions over the past120 years. The most recent o these is thedevelopment o a 1,100 kV UHVDC converter

transormer the highest DC voltage level in

Editorial

Transormer pioneers

Bernhard Jucker Markus Heimbach

the world. This will enable up to 10,000 MWo power (the capacity o 10 large powerplants) to be transmitted eiciently overdistances as long as 3,000 km.

Earlier this year ABB also introduced a PETT a revolutionary traction transormer thatuses power electronics to reduce its size andweight while increasing the energy eiciencyo the train and reducing noise levels.

Other recent pioneering developments include1,200 kV AC technology, subsea transormersthat can supply power at a depth o 3,000 m,ultralow sound transormers or noise-sensi-tive environments, and innovative amorphouscore and biodegradable-oil-based transorm-ers. ABB has also introduced high-eiciencydistribution transormers, both liquid anddry-type, that can reduce energy losses by40 to 70 percent.

ABB cont inues to deve lop innovative assetoptimization, reurbishment and maintenancesolutions to serve the existing global installedbase.

ABB transormers can help customersaddress new challenges and opportunities likethe integration o renewables and distributedpower generation as well as accommodatingnew types o electrical loads such as datacenters and electric vehicles shaping theevolution o more lexible, stronger and

smarter grids.

We hope you enjoy reading this ABB Reviewspecial report in which many o ABBsaccomplished engineers share technologyperspectives across a range o applications.


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5Editoria


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MAx ClAESSEnS Histor is marked b a series o great ivetios that haveswept across societ, actig as steppig stoes i the emergece o the moderword. Most peope woud agree that re, the whee, moder trasportatio adcommuicatio sstems, cumiatig with the Iteret a have a pace i this ist.Mabe ess obvious but equa pivota is the arge-scae trasmissio ad

deiver o eectrica eerg over og distaces. This breakthrough that woudot have bee possibe without the trasormer. This artice takes a brie tour othe histor ad techoog behid the trasormer ad ooks at the dieret wasi which ABB has advaced ad appied it.

ABB is the worlds largest transormermanuacturer and service provider

A world intransormation


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7A word i t rasormat io

Power transorm-ers were the mainreason that thethree-phase ACtransmission sys-

tem could estab-lish itsel as themain T&D tech-nology around130 years ago.

dreds o volts. In the early 1880s, orexample, the Edison Illuminating Com-pany supplied 59 customers in LowerManhattan with electricity at 110 V DC.But the energy demand o the astgrowing cities and industrial centerscalled or an increase in power trans-mission capability.

The small steam- and hydro generatorswere no longer suicient and larger

power plants were erected more remote-ly rom the cities. Voltage levels hadto be increased tokeep nominal cur-rents on the powerlines moderate andreduce losses andvoltage drops. Thiswas the time othe birth o a newcomponent: thepower transormer.

In a transormer, two coils are arrangedconcentrically so that the magnetic ieldgenerated by the current in one coilinduces a voltage in the other. This phys-

Around 130 years ago a techni-cal revolution took place thatwas to be a vital step in thedevelopment o modern so-

ciety. That revolution was the commer-cial generation, transmission and usageo electrical energy. Nobody today canimagine a world w ithout electricity. How-ever, this article will start by taking thereader back to the early days when pio-neers like Thomas Edison and George

Westinghouse and their ideas werecompeting or the transmission systemo the uture: Should it be DC or shouldit be AC?

Very ear ly electr ical installations werelocal: The sites o generation and con-sumption were at most a handul o kilo-meters apart: Direct connections romthe steam- or hydro generators to theconsumers were in the range o hun-

ical principle can only be applied in ACsystems, as only a time-varying mag-netic ield is able to induce a voltage. Byusing a dierent number o winding turnsin the two coils, a higher or lower voltagecan be obtained. The ability to transormrom one voltage level to another onewas the main reason or the break-through o AC three-phase transmissionand distribution systems. These AC sys-tems operate at a requency high enough

that human short perception does notsee the time variation (lickering) and

low enough that switching equipmentcan be operated saely. The best com-promise was the well-known 50 or 60 Hzo the todays mains supplies.

Tite pictureTransorme rs are a vital l ink in the power transmis-sion and distribution chain.

The power transmissionbreakthrough would not havebeen possible without thetransormer.


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overvoltage impulse o a lightning strike.New coil designs mitigated these reso-nance eects.

Transormers are the main current-limit-ing element in case o short-circuit ail-ures in the transmission system. The so-called stray reactance, which representsthe magnetic lux outside o the mag-netic core limits the increase in current insuch an event. I high currents low

through the coils uncontrolled, mechani-cal orces try to press the coils apart,and may cause damage i the construc-tion is not suiciently robust.

Due to the resistance and inductance othe power lines themselves, the voltagelevel may vary depending on load condi-tions. This means that less voltagearrives at the receiving end o a powerline when the load is high. To keep thevoltage level within an acceptable range,

power transormers usually include anon-load tap changer to vary the numbero active winding turns o coil by switch-ing between dierent taps. In mediumvoltage (MV) distribution, this is usuallydone oine: This means the tap changersare adjusted once beore the transormeris energized and then remain fxed.

The increasing importance in recentdecades o UHV (ultra-high voltage) DCtransmission lines or high power trans-

mission over very long distances (greaterthan 1000 km) has made it necessary todevelop UHV-DC converter transormers,which are a huge challenge especially or

Transormers need an ampli ier or themagnetic ield so that the number owinding turns can be kept low. This am-pliier is the so-called magnetic core.It consists o erromagnetic iron, whichcontains microscopic elementary mag-nets that align to the transormers mag-netic ield as a compass needle aligns tothe Earths magnetic ield. The iron coreis made o many thin erromagnetic steelsheets that are electrically insulated

against each other and stacked. Thisreduces classical eddy losses. The useo special alloys and manuacturingmethods enables a minimum neededenergy to change polarity o the elemen-tary magnets.

This bas ic physical principle o trans-ormers is still the same today as it was130 years ago, but energy density, ei-ciency, costs, weight and dimensionshave drastically improved. This can be

compared to the history o cars and theinternal combustion engine: Here too thebasic principle has remained unchangedin 100 years, but technical progress hastransormed the scope o possibilitiesalmost beyond recognition. During theirst decades o electriication, the mainocus in transormer research and devel-opment was to increase power capacity(the power that can be transmitted byone unit). Furthermore, more and moreeects concerning voltage transients

became known that could endanger thetransormers insulation. These includeresonance eects in the coils that can betriggered by ast excitations such as the

Power transormertechnology madetremendous prog-ress during the last130 years.

1a The words argest trasormer i 1942 (220 kV / 120 MVA)Vrta substatio Stockhom, deivered b ASEA

1b The words rst 800 kV UHVDC power trasormer or the 2,000 kmxiagjiaba-Shaghai trasmissio ik, deivered b ABB i 2008

1 Trasormer deveopmet


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9A word i t rasormat io

usually have a orced internal convectionlow o air to ensure suicient cooling othe transormer core.

AMDT (amorphous metal distribut iontransormers) is an upcoming technologythat reduces losses inside the magneticcore. Although the amorphous materialsare still more expensive than standardgrain oriented steel, their application canbe justiied depending on how theselosses are capitalized over the lietime othe transormer.

Power trasormers

When the transmitted power exceedsaround 10 MVA, special designs arerequired to cope with the mechanicalorces o short circuit currents, higherinsulation levels and increased coolingrequirements. For these ratings, liquid-illed transormers are usually used. Theinsulation between the windings be-comes more and more demanding athigher voltages. Furthermore, resonanceeects inside the winding itsel have tobe considered to avoid insulation ailures

during highly dynamic impulse stressessuch as lightning strikes which mayreach amplitudes o one to two thou-sands kilovolt with a 1 s rise time.

the electric insulation system. The 800 kVUHV-DC Xiangjiaba-Shanghai line 1,or example, has a capacity o up to

7200 MVA, which is roughly comparableto the consumption o Switzerland.

Distributio trasormersOn the distribution level (transmittedpower up to 10 MVA) there are two maincategories o transormers 2: Liquidilled (using mineral oil or replacementluids such as synthetic or natural esters)and dry type. The liquid illed transorm-ers are the most compact and cost ei-cient solution, whereas dry type trans-

ormers are preerred in environmentswhere ire saety is o special importancesuch as, or example, underground sub-stations, mining sites, marine and someindustrial applications 3, 4.

Standard versions o distribution trans-ormers are cooled passively as the heatgenerated by losses is transported awayrom the core by natural convection othe insulation medium. In the case oliquid illed products, this heat is then

transported through the tank walls bythermal conduction and removed by thenatural or orced convection o air. Drytransormers in closed environments

Dry-type trans-

ormers are thepreerred technol-ogy or applica-tions in which iresaety is o specialimportance.

2a liquid ied

2b Dr-tpe

3 Dubais 868 m high Burj Khaia buidig isequipped with 78 ABB dr-tpe trasormers

2 Distributio trasormers come i twomai categories

4 Sige-phase poe-mouted trasormers,or sma power casses up to 167 kVA

5 Oe eampe o a etreme appicatio isthis 600 MVA / 230 kV phase shi ter


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Transormers with power ratings above

some ten MVA are a key element in thesupply o large regions or industrial areas.As a rule o thumb, it can be consideredthat one person has an average electricalpower demand o 1 kVA, which means,that a 400 MVA transormer transers thepower needed by 400,000, the equivalento a medium sized city. Such transormershave to comply with special requirementson saety and reliability and also have toprovide a very high efciency and lowsound level. In recent decades, high volt-

age DC lines have also become increas-ingly important, especially in large coun-tries such as China where they connectindustrial centers to the remote regionswhere the electricity is generated. ABBnow oers standard solutions or DC con-verter transormers or up to 800 kV DC.

A transormers located directly next to apower plant is called GSU (GeneratorStep-up Unit). A GSU transorms the elec-tric power rom the medium voltage o the

generators to the high voltage transmis-sion level.

To balance power ow between parallelpower lines, phase shiters can be used.

These are transormers (usually with a 1:1translation ratio) that adapt and control thephase angles o voltage and current tooptimize the power transmission capacityo the lines. Phase shiters exist up to apower rating o 1,500 MVA 5.

Today transormation efciencies o up to99.85 percent are achievable by usingspecial magnetic steel qualities and opti-mized designs. The heat losses, even at

these high efciencies, are still signifcant:For the 400 MVA unit mentioned above, orexample, it would be still around 600 kWunder ull load conditions. The cooling sys-tem thus remains a challenge. Additionally,the weight and size o such devices has tobe dimensioned careully since there are

limitations in the maximum transportationpossibilities in the dierent countries 6.

Tractio ad specia trasormersRailway vehicles use a special type otransormer that must be highly compact,reliable and robust. Operating requenciesvary (according to countries and systems)rom 16.7 Hz to 60 Hz with power classeso up to 10 MVA. To permit trains to crossborders between countries, traction trans-ormers must be compatible with the di-

erent requencies and power systems.ABB oers optimized solutions or all thesedierent railway applications, stretching upto high speed trains with their challengingneeds 7.

Moreover, ABB makes a variety o urthertransormers or special applications, orexample or subsea electrifcation or oroperating variable speed drives.

7 ABB is suppig the tractio trasormeror the ew Vearo D high speed trai

Ma CaessesABB Power Products, Transormers

Zurich Switzerland

[email protected]

6 ABB is the words argest trasormer mauacturer ad service provider, capabe odeiverig high-quait durabe products ad services a over the word

ABB t ransormers are ound wherever elect ricit y is genera ted, transported and consumed in powerplants and substations skyscrapers and shopping malls, ships and oil platorms, locomotives andrailway lines, wind parks and solar ields, water and wastewater plants. The worlds tallest building,the 828 meters high Burj Khalia in Dubai is equipped with 78 dry-type ABB transormers to ensurepower reliability 3.The nearby Dubai Founta in, which is i lluminated by 6.600 li ghts and shoots water150 meters into the air, is also equipped with ABB transormers.

For almost 120 years, ABB has produced commercial transormers and continued to enhance themby developing new technologies and materials that raise eiciency, reliability and sustainability to anew level.

ABB has set the world records or t he most powerul many times rom the worlds ir st tr ansormerso 400 kV and 800 kV in the 1950s and 1960s, to the most powerul UHVDC tr ansormers or the800 kV, 2000 km Xiangjiaba-Shanghai transmission link in China 2. By developing new high-peror-mance materials and using ire-resistant insulation liquids, ABB has improved the eiciency, saety andenvironmental riendliness o transormers. The new eco-riendly product lines can achieve energysavings o 40 50 percent.

For almost 120years, ABB hasproduced commer-cial transormers.

ABB has set theworld record orpower many times.


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ARnE HJORTSBERG, PIERAlVISE FEDRIGO, THOMAS FOGElBERG Powertrasormers are a ver importat part o ABBs busiess, as we asthat o the origia corporatios that came together to orm ABB. Thismerger created a uique opportuit to itegrate the vast eperiecesad dieret techica competecies rom a the oudig compaies.Prior to 1900, these compaies pioeered dieret aspects o powertrasormer deveopmet. I 1893, ASEA, oe o ABBs paret compa-ies, suppied oe o the irst commercia three-phase trasmissiosi Swede rom a hdro power pat to a arge iro ore mie some10 km awa. Trasormer mauacturig soo emerged i most cou-

tries i Europe ad i the Uited States. ASEA, BBC ad other prede-cessor compaies rapid gaied epertise i the mauacturig adistaatio o trasormers. Toda, ABB draws upo 700 ears ocombied eperiece o trasormer desig ad mauacturig.

ABB is a leader involtage and powerextensions

A legacy otransormation

A egac o t rasormat io


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ABB and its predecessor compa-nies have consistently stood atthe oreront o the manuactur-ing and development o com-

mercial transormers 1. As transmissiondistances rom remote generation in-

creased, the transmission voltage had torise to keep losses down and to reduce thenumber o lines needed in parallel. In theearly 1950s, Sweden commissioned ASEAor the worlds frst 400 kV transmissionsystem with a length o about 1.000 kmand 500 MW capacity. This breakthrough inextra high voltage (EHV) transmission set anew standard or Europe.

In the latter part o the 1960s, the Canadianprovince o Quebec ollowed suit. Similar to

the situation in Sweden, it too had abun-dant hydropower yet large geographic dis-tances between the power source andindustrial areas. Together, the power com-pany Hydro-Quebec and ABB developed a735 kV EHV transmission system. In theUnited States, large thermal power plants,rom which the power had to be distributedover long distances, were also being built.

This resulted in the introduction o a 765 kVsystem. In the early 1970s, the Tennessee

Valley Authority commissioned its frst

1,200 MVA power plant at Cumberland,Tennessee. ABB built the frst generatorstep-up transormers (rated 420 MVA) in asingle-phase design.

These transormers represented a technicalbreakthrough in terms o power capacity onone wound limb.

At the same time, ABB entered a develop-

ment program together with American Elec-tric Power (AEP) aiming or the highesttechnically easible AC transmission volt-age. For this purpose, ABB built a ull-sizesingle-phase network transormer or1,785 kV, rated at333 MVA. This testtransormer was in-stalled and suc-cessully operatedat the research acil-ity until completion

o the research pro-gram 2. Similardevelopment pro-grams occurred inother countries. For example, a ull-size

ABB transormer and shunt reactor wasbuilt in Italy or 1,000 kV and installed atthe ENEL test station Suvereto.

During the last ew years the need or evenhigher capacity long-distance transmissionhas resulted in renewed interest in ultrahigh

voltage alternating current (UHVAC) voltag-es in the range o 1,000 to 1,200 kV AC inChina and India, and the development o800 and 1,100 kV ultrahigh voltage direct

Tite picture1,100 kV ultrahigh voltage direct current transormerin the ABB HVDC test acility

1 Puig the Gotad cabe ashore i 1950. The power ik coected the isad to Swedesmaiad power grid, supportig the deveopmet o the isads ecoom

ABBs HVDC technologyhas had a truly revolutionaryimpact on the way that

electric energy is deliveredall over the world.

current (UHVDC) has resulted in ABBemerging as a major player in pushingtransormer technology to new levels.

The TraoStar techoog patormIn August 1987, the Swedish ASEA and theSwiss BBC companies merged and ormed

ABB. Shortly aterward, ABB merged thetransormer manuacturing parts o West-inghouse in the United States, which also

included the ormer General Electric trans-ormer technology, as well as Ansaldo inItaly and several Spanish actories. NationalIndustri in Norway and the Finnish companyStrmberg had become part o ASEA just

beore the merger. Together, these compa-nies contained a very large portion o all thepower transormer knowledge and experi-ence in the world.

Ater the merger, a number o task orcesand research and development groupswere established to evaluate the experience

and best practices rom a wide range opreviously independent transormer manu-acturers. Major objectives were lowercosts, shorter production times, higher


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13A egac o t rasormat io

racy and major suppliers with commonmaterial specifcations, testing and qualitymanagement system. This concept is nowused or large power transormers in all

ABB plants globally. Since the inception oTraoStar, more than 15,000 power trans-ormers have been produced; o these,2,000 units are very large generator step-up(GSU) transormers and intertie transorm-ers. More than 1,000 power transormers omore than 60 MVA rating are producedevery year. This unique business concept

has allowed ABB to amass design andmanuacturing experience in a truly globalway, or continuous process improve-ment 4.

Since ABB is also one o the worlds majorsuppliers o all types transormer compo-nents insulation materials and kits, tapchangers, bushings, and electronic controlequipment the company is in a uniqueposition to control product quality and per-ormance.

Servig the ew eectric power marketsSince the inception o ABB in the late 1980sseveral major changes in the electric power

quality and reduced test room ailures.These objectives have remained the mainocus or ABBs continued transormerdevelopment. As a result, ABB succeededin uniying its technology into a commonplatorm, TraoStar, and today it oers prod-ucts with the same high standard o qualitywherever in the world the transormers aremanuactured 3. The TraoStar techno-logy platorm includes the ollowing keyingredients: Common design rules based on

experience rom all ABB predecessorcompanies

Common design system and designtools

Common manuacturing processes,equipment and tools

Common quality and ailure analysissystems

Common eedback and continuousimprovement programs

Common training and educationsystems

ABB launched the common concept, Trao-Star, more than 15 years ago, with integrat-ed engineering tools, manuacturing accu-

ABB has promotedand successullyperormed moreshort-circuit teststhan any other

supplier.

2 The 1,785 kV utrahigh votage trasormer istaed at the USAEP-ASEA test statio (USA)


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Institute o Electrical and Electronics Engi-neers (IEEE) and other commissions, spec-iy the requirements on power transormersand how their perormance should be veri-

fed. There is, however, extensive evidencethat many transormers are not as short-circuit proo as assumed. Failures causedby short-circuits are still a major cause otransormer outages, and ailure rates varywidely between dierent countries and sys-tems, depending on network characteris-tics and equipment installed.

Dierent networks have varying problems.In rapidly developing regions with increas-ing demand or electric power, more and

more generating capacity and interconnec-tions are added to existing systems. How-ever, the western world is characterized byexpanding cross-border electricity trade,integration o wind and other renewables,changing load ows and aging compo-nents. Several o these circumstancesmean that old as well as new transormerswill be exposed to even more demandingsevere short-circuit stresses.

Assurig trasormer quait

ABB has continued its predecessors activeparticipation in international bodies such asCIGRE (the International Council on LargeElectric Systems), IEC and IEEE helping toestablish stringent standards on test levelsand test procedures to veriy transormerperormance and quality under variousoperational conditions. Successul actoryacceptance testing o new transormersis necessary but not in itsel sufcient todemonstrate service quality in all respects.Dielectric perormance is very well covered

by appropriate international standards thathave been developed over the years.

es. A very rapid build-out o manuacturingcapacity occurred particularly in Asia, caus-ing a substantial overcapacity at the endo the period, with new imbalances and

instabilities in material prices. ABB, with itsglobal position and common technology,emerged as a major orerunner during thisperiod.

In the present market, utilities and otherpower transormer buyers have a muchmore complex procurement process. Manyo their local manuacturers and sub-suppli-ers are gone and many new unproven play-ers have emerged. The local service sup-port organizations have been transormed

or are no longer available. Economic pres-sure has increased and new load patternsand highly loaded networks are challengingdemands on the reliability and stability othe networks. Sae and reliable operation isa key but requires a procurement processor transormers and other equipment thatcan correctly identiy quality products. Thisis a ormidable challenge. ABB supports itscustomers in this new challenge by deliver-ing a very well proven and reliable productwith verifed quality properties as well as a

stable service and support organization.

Power sstem reiabiitModern power systems are increasinglycomplex with a large number o individualcomponents. To ensure reliable operation, itis essential that the key elements, such aslarge power transormers, have a very highdegree o availability, minimizing the outag-es o individual components or wholeblocks o power generation.

The ability to withstand short-circuits is rec-ognized as a very crucial unction o powertransormers in the network. The Interna-tional Electrotechnical Commission (IEC),

markets have occurred. As the originaldomestic, country-based networks havebeen built out and matured, markets wereopened up and deregulated in the westernworld to promote competition and efcientinterconnections and creation o regionalnetworks and markets. This evolution led toa change in relations between transormermanuacturers and buyers, rom local tomore global relations, and with a greaterocus on economic aspects on both sides.

As a result, manuacturers also had to

become more global, leading to consolida-tion and concentration o the industry. ABBwas perectly prepared or this develop-ment, and emerged as the world leader inpower transormers.

Simultaneously, the emerging markets inAsia and South America started to have amajor inuence, and later dominated thedemand or power transormers. The rapidbuild-out in China and later India and otheremerging markets created a boom period

or transormers during the frst decade othe new century, causing very high materialprices or copper and core steel, and longdelivery times and various other imbalanc-

The uniqueTraoStar business

concept hasallowed ABB toamass design andmanuacturingexperience in atruly global way.

3 TraoStar

ABBs kowedgebase is buit rom the 700 ears ocombied eperiece rom severa compaies icudig:

ASEA National Industri

Ansaldo/Ital Trao/IEL/OEL/OTE Strmberg

BBC Westinghouse

GE, United States

ABB utilizes a common design and manuacturing platorm in all 13 power transormer actories worldwide.ABB has delivered more than 14,500 power transormers (over 17,000,000 MVA) based on TraoStar,including over 20,800 kV UHVDC units and over 500,735 kV to 765 kV AC units to all major global markets.

Through continuously improved design and manuacturing procedures, ABB has reduced test ailures by50 percent between 2000 and 2010. As a result, ABBs short-circuit withstand is now more than twice ashigh as the market average.


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actors. In high-voltage systems, the mostprobable type o SC is a single-line-to-earthashover, normally due to environmentalconditions such as a lightning strike on theline, etc. The relative severity o the dierenttypes o aults depends on the characteris-tics o the system, in particular on the SC

impedance value o the transormer and theSC apparent power o the system.

Forces and related withstand criteria inwindings can be split into two components:radial orces and axial orces.

The ailure modes or radial orcesinclude: Buckling o inner windings Stretching o outer windings Spiraling o end turns in helical windings

The ailure modes or axial orces include: Mechanical collapse o yoke insulation,

press rings and press plates, and coreclamps

Conductor tilting Conductor axial bending between

spacers Possible initial dielectric ailures inside

windings, ollowed by mechanicalcollapse

The SC orces are calculated in ABB withadvanced computer programs based ondetailed fnite element methods (FEM) thatalso take into account axial displacements

The areas o thermal and mechanical integ-rity, however, are arenas where design andproduction weaknesses can pass testswithout being detected. ABB has thereoremade specifc eorts in design, production,supply chain and testing philosophy o largepower transormers to veriy thermal and

mechanical perormance. A key measure othe mechanical integrity o the transormer

is a short-circuit test, which ABB has pro-

moted and successully perormed morerequently than any other supplier.

Mechanical rigidity o the transormer willbecome one o the most vital perormanceactors or the uture.

There are three reasons or this: The ability to withstand short-circuit (SC)

stresses Seismic requirements Transport handling

SC orces give rise to mechanical orceson windings that can reach hundreds otons in milliseconds. The current peaks andthe corresponding orces depend on many

4 High-votage direct curret (HVDC)

By the early 1950s, developments in current conversion technology led byASEA, ABBs Swedish orerunner, enabled the company to build the worlds frstcommercial HVDC power link between the Swedish mainland and the island oGotland 2.

Since this installation, ABB has continued to develop HVDC technology, replac ingthe ragile mercury-arc valves in the 1970s with semiconductor devices.

ABB maintains its lead in HVDC technology and to date, has installed60,000 MW o HVDC transmission capacity in 70 projects, and is a marketleader in the manuacture o high-voltage transmission cable as well.

ABBs HVDC technology has had a truly revolutionary impact on the waythat electric energy is delivered all over the world.

Some o the worlds biggest cities, including Los Angeles, So Paulo, Shanghaiand Delhi, rely on HVDC transmission to deliver huge amounts o electricity,

oten rom thousands o kilometers away, with remarkable efciency and minimalenvironmental impact.

ABBs achievements using this remarkable technology include the worldslongest and most powerul HVDC installation, the Xiangjiaba- Shanghai powerlink currently under construction in China, which will deliver 6,400 MW oelectricity over 2,000 km (shown here) and the worlds longest undergroundcable transmission system, the 180 km Murraylink HVDC Light project in

Australia see picture 1b page 8.

The improvements achieved by ABB drives in energy efciency, productivity andprocess control are truly remarkable. In 2008, ABBs installed base olow-voltage drives saved an estimated 170 TWh o electric power, enough tomeet the annual needs o 42 million European households and reduce globalCO2 emissions by some 140 million metric tons a year. That is like taking more

than 35 million cars o the road or a year. As society aces the challenge oreducing environmental impact while meeting rising demand or electricity, ABBsdrives will be making a positive contribution to a better world.

ABBs short-circuitwithstand is overtwice as high as themarket average.


16/76


Due to the high investment costs o SC testequipment, such test acilities are available

in only a handul o locations in the world.The test requires power capacities in therange o a large power grid together withsophisticated control and measuring equip-ment. One such acility is KEMA in theNetherlands, where a number o SC testswere carried out on behal o ABB. In spiteo the high cost, ABB has perormed a largenumber o such tests to guarantee quality.35 ABB TraoStar power transormers odierent designs have been SC tested, witha ailure rate as low as 11 percent 5.

KEMA reports presented at CIGRE andother technical conerences show the totaltest ailure rates or power transormers tobe 28 percent o the perormed SC tests orthe whole industry [1]. ABBs test recordover the last 16 years has been 5 ailuresout o approximately 50 tests, or only10 percent. When the ABB test results arecompared to the result o all other manuac-turers the remaining manuacturers showSC test ailure rates several times higher

than ABB.

Future ambitio or ABB quait eortsIn the uture, new ways o rating transorm-ers through better control o the thermalcapability can help reduce the use o ex-pensive materials. New standards shouldtake the load profle into account, and allowor more exible specifcations to deal withmore complex load patterns. This will re-quire the integration o more intelligence.Other possibilities are to urther increase the

mechanical, thermal and dielectric integrityo transormers to better equip them todeal with the greater stresses that will aectuture networks. Since transormers stand

caused by workshop tolerances and pitcho helical type windings.

Windings are dimensioned or maximumcompression orces, where dynamic eectsare included. An extremely important ea-ture o ABBs SC technology is that innerwindings subject to radial compression aredesigned to be completely sel-supporting-with regard to collapse by ree buckling.

This means that the mechanical stability othe winding is determined by the propertieso the copper and conductor geometryonly, a cautious design principle that has

served ABB very well.

Short-circuit stregth vericatioThe new IEC Standard 60076-5 (2006-2)provides two options or veriying the trans-ormers ability to withstand the dynamiceects o a SC: A ull SC test perormed at a certifed

laboratory A theoretical evaluation o the ability to

withstand the dynamic eects o SCevents based on the manuacturers

design rules and construction experi-ence, in line with the new IEC guidelines.

or a substantial part o the network losses,energy efciency programs will urther re-

quire transormer designs and technologywith lower losses.

For more inormation about ABBs trans-ormer technologies, please see A world intransormation on page six o this specialreport.

Pieravise Fedrigo

ABB Power Products, Transormers

Sesto S. Giovanni (Milan), Italy

[email protected]

Are Hjortsberg

ABB Corporate ResearchBaden-Dtwill, Switzerland

[email protected]

Thomas Fogeberg


Ludvika, Sweden

[email protected]

5 TraoStars short-circuit reiabiit is more tha twice the idustr average

5a ABBs TraoStar trasormers

MVA (rated)

Numberoftransformers

12

10

8

6

4

2

02550 50100 100200 >200

TraoStar rated 25 MVA or higher,short circuit tested 19962011

31 out o 35 tested units 25 MVA were passed between1996 and 2011, corresponding to 11 % test ailures.

Initially not ok

Initially ok

5b Trasormers tested b KEMA

MVA (rated)

Numberoftransformers

12

40

32

24

16

8

02550 50100 100200 >200

All transormers rated 25 MVA or higher,tested by KEMA 1996-2009

Total test ailures 28 %

Initially not ok

Initially ok

Reereces[1] Smeets, R.P.P., te Paske, L.H. (2010)

Fourteen Years o Test Experience with Short

Circuit Withstand Capability o Large PowerTransormers. Travek VII th In ternational Sc ienceand Technical Conerence on Large Power

Transormers and Diagnosti c Systems, Moscow,Russia.

ABB draws upon

700 years o com-bined experienceo transormerdesign and manu-acturing.


17/76

17UHVDC

THOMAS FREyHUlT, MATS BERGlUnD,

KE CARlSSOn HVDC (high-votagedirect curret) power trasmissiois a eiciet ad cost competitivewa o trasmittig arge amoutso eectricit over og distaces.

ABB has etesive eperiece withHVDC techoog, ad has deveopedad buit coverter trasormersor the most demadig projects,icudig products or utrahigh-vot-age trasmissios. 800 kV UHVDC(utrahigh-votage direct curret)trasmissio was put ito commerciaservice i 2010; 1,100 kV UHVDC isow beig deveoped. This articecosiders some importat steps ithe desig ad deveopmet o

techoog or the most demadigpower trasmissio appicatios.

Meeting the needs o the most demanding

power transmission applications

UHVDC

technology, driven by the immediate needor transmission assets. Compoundingthe pressure, stringent reliability require-ments are a prerequisite o these verylarge transmission projects.

Trasmissio basicsThe State Grid Corporation o China putthe world`s irst 800 kV DC transmissionsystem into commercial operation in2010. It is a 2,000 km long power linewith a capacity o 6,400 MW, generatedby a large hydropower plant in Xiangjiabaand transmitted to Shanghai. The AC toDC converters are built as 800 kV dou-ble circuits with eight series-connected,six-pulse converters. The transormersare single phase, two-winding units. In

total, 24 converter transormers areneeded at both the sending and receiv-ing ends.

Depending on the position o the trans-ormers within the converter, our dier-ent designs are needed with dierentDC voltage ratings (800, 600, 400 and200 kV) where the transormers connect-ed to the uppermost and lowermostbridges had to be built or the highestDC potential 2.

For the Xiangjiaba to Shanghai projectABB des igned and buil t transormers orthe receiving station. The transormers

The need or electric power israpidly increasing in the devel-oping world. Power sourcesclose to consumption centers

have already been harnessed, and pres-ent eorts are exploring ways to generate

and move power rom urther away, espe-cially sources o renewable energy. Devel-oping countries such as China, India andBrazil have large populations and aremodernizing quickly, but closing the gapwith the developed world will require alarge amount o electric power.

HVDC is the most environmentally riendlyand economical way o transmitting largeamounts o electric power. Comparedwith AC, DC transmission needs much

narrower right-o-ways, while higher volt-ages reduce both electricity losses andthe cost o building large-scale powerlines. As generation takes place urtherand urther away, higher and higher trans-mission voltages are required. The high-est DC transmission voltage has almostdoubled during the last decade 1.

The swit pace o economic developmentin certain regions has meant the time todevelop equipment to support higher

transmission voltage levels has been veryshort. Chinese customers in particularhave pressed or rapid development anddelivery o the frst projects using UHVDC


18/76


Pioeerig workIn the late 1970s, ABB did pioneeringwork in this area when the frst set otransormers or 600 kV DC transmissionwas delivered to the Itaipu HVDC projectin Brazil.

The transormer concept used or Itaipuhas been a template or most HVDCconverter transormers: a single-phase

design, with two wound limbs and twoouter limbs or the return ux. The wind-ings are arranged concentrically with thevalve winding on the outside. The linewinding is divided into two coils the oneor the tapped part is located closest tothe core, ollowed by the nontapped sec-tion. This arrangement is benefcial or thetopology o the valve-side, which requires

AC as well as DC insulat ion.

The basic Itaipu concept has undergone

continuous improvements, such as valve-side bushings protruding directly into thevalve hall. Eliminating the need or separatebushings between the transormer terminal

The design o the valve is such that therate o current increase must be con-trolled when the valve starts carrying cur-rent. The rate o increase largely dependson the transormer reactance, which alsohas to be ulflled within narrow limits ortwo individual transormer units.

The high content o current harmonicsrequires special attention be paid to con-

trolling additional and stray losses in thetransormer, when it comes to total lossesand the risks o local overheating inthe windings and metallic componentsexposed to stray ux rom windings andinternal current carrying leads.

In order to optimize the reactive powerneeded or the operation o the converter,depending on load variations the systemdesigner generally specifes a large rangeo voltage ratio variation between the line

and valve sides.

or the higher voltages were designedand manuactured in Ludvika, Sweden.

The remaining units were manuacturedby ABBs partners in China.

Sstem requiremets or coverter

trasormersThe basic unct ion o the converter trans-ormer is to adjust the line voltage o the

AC side to the HVDC transmission volt-age. In addition, it must ulfll other spe-cifc requirements, including: A galvanic separation between the DC

and AC systems Specifed short-circuit impedance High content o current harmonics Large range o voltage regulation

In conventional AC/DC converters, thetransormer acts as a barrier to preventDC voltage rom entering the AC network.One o the transormer windings is con-nected to the AC side, which is also calledthe line-side winding. The other winding isconnected to the converter valves, calledthe valve-side winding.

DC voltage results in additional demandson the insulation structure in comparisonto AC voltages. Ater long and dedicated

research and development, ABB hasdeveloped a successul insulation systemsuitable or the highest transmission volt-ages or AC as well as DC.

1 Some o ABBs ke HVDC projects

Itaipu 3,150 MW / 600 kV DC Brazil 1982

Three Gorges projects 3,000 MW / 500 kV DC China 2003

Xiangjiaba Shanghai 6,400 MW / 800 kV DC China 2010

Ningdong Shandong 4,000 MW / 660 kV DC China 2011

Jinping Sunan 7,200 MW / 800 kV DC China 2012

North East Agra 6,000 MW / 800 kV DC India 2015

Hami Zhengzhou 8,000 MW / 800 kV DC China 2014

Zhundong Chengdu 10,000 MW / 1,100 kV DC China 2015

2 Basic arragemet o trasormers adcoverters

500 kV AC

800 kV DC

Earth

0200 kV

200400 kV

400600 kV

600800 kV

+800 kV DC

3 Measuremet setup


19/76

19UHVDC

ing application are well-known, at least ormoderate voltage levels.

The stress pattern or a DC voltageapplied between electrodes will have asimilar distribution in the initial phase aterthe application o the voltage. Ater theinitial state, the electric stress patterngoes through a transient state, fnallyending up in a steady state, oten aterseveral hours. In contrast to AC, thematerial parameters that govern behaviorunder DC stress display larger variation

and the back-

ground physics isvery complex. Vari-ations o materialparameters anddesign have largeconsequences orthe electric stressoccurring insidethe transormers,and this is why in-

sulation structures have to be designedand manuactured with great care to

achieve a reliable result.

ABB has developed the means to accu-rately measure stresses in models o theinsulation systems used in HVDC con-verter transormers.

Electric stress in more complex insulationstructures can be modeled and measuredusing the electro-optic Kerr eect. Polar-ized light passing through transormer oilchanges its polarization state depending

on the electric stress applied. Detection othe phase shit between light componentsparallel and perpendicular to the electricfeld allow measurements o the magnitude

and the interior o the valve hall helped toreduce the cost and complexity o station

layouts. In addition, step porcelain bushinghousing was replaced by composite mate-rial, and within the bushing compressedgas replaced oil. These new materials re-move the risk o disastrous consequencesin the event o a bushing ailure.

AC ad DC stressesThe stress patterns or AC voltage be-tween two electrodes are airly straight-orward. The stresses o dierent materi-

als in combined insulations dependprimarily on the permittivity o the individ-

ual materials. In order to reach reliableoperation, the stresses or each o theinsulating materials must not exceed arecommended value. The insulation struc-tures in an HVDC converter transormerare built up rom cellulose-based solidinsulation and mineral oil as an insulationand cooling medium. The ree distance ina liquid insulating material must be con-trolled by intermediate insulation barriersto reduce the risk o abnormal voltagebreakdowns. In short, predicting stress

distributions caused by AC waveorms isstraightorward, and the material param-eters are stable under dierent operatingconditions. The physics and its engineer-

ABB has developed themeans to accurately measurestresses in models o theinsulation systems used inHVDC converter transormers.

4 800 kV coverter trasormer


20/76


sions 4. Over time, models were ex-posed to very demanding operational and

test conditions to ully demonstrate reli-able perormance. Special attention waspaid to components with complicatedgeometry, like windings and the connec-tion between the valve winding and bush-ing. An intricate balance between solidand uid insulation has to be achieved inthe design o the transormer insulation.

The HVDC bushing was another compo-nent needing special attention. As its airside enters the valve hall, it is essential

that a breakdown not lead to fre or dam-age rom shattered pieces o the bushing.

For that reason, the insulation systemaround the bushing lead is a condenserbody, and the space between the bodyand the cylinder-shaped insulator is flledwith compressed gas. Silicon sheds areextruded on the tube outside to permitindoor or outdoor use.

Scientifc advances have not only been

made in transormer insulation, but alsobushings. Challenges similar to those inoil and cellulose insulation also exist in airinsulation systems. An ABB innovationenabled the electric feld to be measuredon the surace o an insulator on thebushing o an HVDC transormer. Simula-tion models are calibrated by actual mea-surements, and special phenomena areintegrated into the bushing design.

Tests

A transormer is subject to delivery testsater it is manuactured, assembled andinstalled on site. These tests are or verif-cation o dielectric and operational re-

and direction o the electric feld. The lownumerical value o the Kerr constant o

transormer oil, and airly moderate feldstress in the uid phase o the insula-tion places stringent requirements on themeasurement system to achieve sufcientaccuracy to measure magnitude anddirection o the electric feld 3.

The Kerr cell measurement has givenABB valuable inormation about the stressdistribution in multibarrier insulation sys-tems used in high-voltage power trans-ormers in transient as well as steady-

state conditions. For a more accurateanalysis the distribution o space chargeshas to be considered, especially or a bar-rier system with small ducts between theindividual barriers. The traditional methodo resistive steady-state distribution hasimportant limitations, and reliable insula-tion structures cannot be developedbased only on such a theoretical method.However, calculation models based ontrue charge transport behavior developedby ABB and calibrated by real measure-

ments are the basis or all design rulesconcerning reliable insulation structuresor all ABB converter transormers today.The chaege o UHVDC

Although ABB had all the basic knowl-edge in-house, it was also necessary toacquire hands-on experience with thecharacteristics o vital components in thetransormers, as well as external connec-tions, particularly on the valve side. Forthat purpose, a ull-scale test model was

built, complete with tank, windings, inter-nal connections and valve-side bushingsor the development o equipment or usein both 800 kV and 1,100 kV DC transmis-

It was necessary to

acquire hands-onexperience with thecharacteristics ovital components inthe transormers.

5 Additioa dieectric tests or the vave widigtogether with correspodig votages ad duratios

Poarit reversa

966 kV

90

120

1,600 kV

2,000

120 165 60

902 kV

t (ms)t (ms)

t (ms) t (s)

1,246 kV

Appied DC votage

Appied AC votage

Appied switchig surge


21/76

21UHVDC

external terminals o the winding are con-nected together and the voltage is applied

to the two terminals simultaneously.

During the test with applied DC voltage,the level o partial discharge is measured.During the transient period ater theapplication o voltage, there may beoccasional charge movements within the

insulation system.These movementsgive rise to a no-ticeable partial dis-charge signal on

the valve-side ter-minals. The phe-nomenon is wellknown and recog-nized in currentstandards. The in-dustry has there-ore accepted anupper limit on thenumber o occa-

sions such bursts o partial discharge cantake place during the tests. Furthermore,

the requency o bursts must diminishduring the course o the test.

The word eeds UHVDCDriven by economic growth, demand orpower and the need to efciently integraterenewable power generation, it is clearrom developments in AC networks thatUHVDC will have a major role to play aspower systems evolve. The expansion othis role is also clear rom the interest inextending the capabilities o UHVDC

transmission in the recent years. GivenUHVDCs very high ratings, it is essentialthat these valuable assets operate saely,reliably and efciently.

quirements set orth in the unit`s specif-cations, as well as the internal ABB qual-

ity assurance program.

Compared with a conventional powertransormer in the AC network, an HVDCconverter transormer must be tested orthe ability o valve-side windings to with-stand DC voltages. In operation, the valve

windings are exposed to an AC voltageand a superimposed DC voltage. A DC

transmission must be able to handle theast transition o power rom one directionto the other. Such transitions also mean aswitch in converter polarity, rom positiveto negative, and vice versa 5.

Operation with continuous DC voltage,superimposed AC voltage and DC polarityreversal will be reected in additional di-electric tests o the valve-side windings;tests with DC voltage, tests with AC volt-age and tests with switching surge voltage

are in accordance with IEC standards. Allour types o test are considered to benontransient, with a uniorm voltage alongthe valve winding. For that reason, the two

ABB has the proven tools and expert iseneeded to design and manuacture reliable

UHVDC converter transormers. This solidtechnology background ensures that evenin the ast-developing UHVDC area, cus-tomers can be sure that ABB equipment isdesigned, tested and built to the higheststandards o operational stability. O theUHVDC projects awarded globally, ABB isby ar the largest supplier and is deter-mined to maintain this lead with urtheradvances in the technology 6.

So what is the next step or UHVDC?

China has clearly expressed an ambitionto achieve even higher DC transmissionvoltages. That ambition has materializedin an R&D program or 1,100 kV UHVDCtransmission, which o course requires arange o dierent equipment, includingconverter transormers built to supportthese record-breaking UHVDC transmis-sions. Rising to the challenge o thesevery ambitious development plans, ABBwas the frst to qualiy HVDC convertertransormer technology at the 1,100 kV

voltage level as well, but how that cameabout in detail is a story or another day the continuing story o ultra-efcient,ultrahigh-voltage direct current electricitytransmission.

Thomas Frehut

Mats Bergud


Ludvika, Sweden

[email protected]

[email protected]

The authors acknowledge the contr ibution to this

article o the late ke Carlsson, ABB Senior Trans-

ormer Specialist.

6 Success stor: the words most poweru UHVDC coverter trasormer

ABB has successully developed and tested a 1,100 kV UHVDC converter transormer, breaking therecord or the highest DC voltage level ever achieved, which means more electricity can be transmittedefciently over even longer distances.

The Xiangjiaba-Shanghai link commissioned by ABB is the world`s frst commercial 800 kV UHVDCconnection picture 2 o page 8. It has a capacity o 6,400 MW and at just over 2,000 km is the longestpower link o its kind in operation. The new 1,100 kV converter transormer technology just tested willmake it possible to transmit more than 10,000 MW o power over distances as long as 3,000 km.

Higher voltage levels enable the transport o larger amounts o electricity across very long distances withminimal losses, using HVDC technology. Converter transormers play a critical role in HVDC transmis-sion, serving as the vital interace between the DC link and the AC network. The development o1,100 kV transormers addresses several technology challenges, including the sheer size and scale othe units, electrical insulation including bushings and thermal perormance parameters.

UHVDC transmission is a development o HVDC, a technology pioneered by ABB more than 50 yearsago, and represents the biggest capacity and efciency leap in more than two decades.

Driven by economic growth,demand or power and the

need to eiciently integraterenewable power generation,it is clear that UHVDC willhave a major role to play aspower systems evolve.


22/76

MARTIn CARlEn Respodig to ewrequiremets i a chagig word,

ABB is compemetig its portoiowith ew dr-tpe trasormer prod-ucts that hep make eectricit suppsstems more eciet, reiabe, sae

ad evirometa ried.

ABB launches new dry-type transormer products

Responding

to a changingworld

ABB recently complemented its port-olio with new products that will playa major role in uture transmission anddistribution (T&D) systems. ABB alsooers a broad portolio o specialty prod-ucts or many, oten specialist, applica-

tions 1.

Eiciec, space ad reiabiitcoutsCustomer interest in products that areboth economically and ecologically ef-cient inspired ABB to develop a dry-typetransormer product amily that exceedsexpectations in these areas. The EcoDrytransormer amily provides ultra-efcient

products with loss values that easily meetor exceed industry standards or legal re-quirements. EcoDry enables customers toselect a product optimized or a specifc

ABB began developing dry-type transormers or mediumvoltage applications in the1970s, recognizing that oil-

ree technologies help transormerscomply with the highest saety standards

or people, property and the environ-ment. Using dry-type transormers,electric substationscan be placed incommercial or in-dustrial buildingswithout undue con-cern about ire risk.

They are easy toinstall and mainte-nance ree.

ABB dry-type trans-ormers have evolvedinto what we nowcall standard dry transormers. They aremostly used to distribute electricity to endusers, and are available with dierent coiltechnologies: Vacuum Cast Coil (VCC): high quality,

well-protected windings Vacuum Pressure Impregnation (VPI):

allows eicient cooling

Resibloc: ultimate mechanicalstrength, qualiied or extremeclimactic conditions ( 60 C)


Customer interest in productsthat are both economicallyand ecologically eicientinspired ABB to develop adry-type transormer product

amily that exceeds expecta-tions in these areas.


23/76

23

rather low average load o 20 percent [1].EcoDryBasic has lower losses than low-loss,oil-immersed distribution transormers.

In industrial processes, transormers re-quently run at nearly maximum capacity.In its EcoDry99Plus transormer, ABB hasdeveloped design enhancements thatreduce transormer losses by 30 percentor more.

EcoDryUltra combines eatures, reducingboth no-load and load loss, and providingultimate efciency over the whole loadrange. In the event o strongly varying

loads, or example in solar and wind powergenerating applications, or or operatingthe transormer at medium load, EcoDryUltrais the ultimate choice.

Although EcoDry transormers requiremore materials in construction, energysavings over the equipment`s lietime morethan compensates or this, and makes thisproduct a winning solution environmental-ly, as demonstrated by lie cycle assess-ment (LCA) [2] 3.

Another way to increase transormer ex-cellence that also enables compact instal-lations and reduced losses is with the

application, minimizing the cost o relatedinvestments.

Transormer losses occur in two areas:frst, the load independent no-load loss,which occurs in the iron core due to thecyclic change o magnetization resultingrom the connected AC voltage; and sec-ondly, the load loss, which depends on theelectrical resistance in the transormerwindings and on the actual transormercurrent. Overall, this produces an efcien-cy curve that is load dependent. When thetransormer load is low, the no-load losswill dominate, whereas at high load, the

load loss is dominant. Analysis o the totalownership cost (TOC) [2] will help in theselection process 2.

EcoDryBasic substantially reduces no-loadloss with a core made o amorphousmetal. The no-load loss o the EcoDryBasicis 30 percent that o the no-load lossin dry-type transormers itted with nor-mal steel laminate cores. And these sav-ings add up: when a small, 1,000 kVAdry-type transormer is operated or

20 years, CO2 emissions are reducedby 140,000 kg, which is equivalent toburning 60,000 liters o oil. Utility distri-bution transormers oten operate at a

1 Additioa dr-tpe trasormer ad reactor products

3 lie cce aasis perormed or a stadard dr trasormer ad a EcoDrtrasormer (1,000 kVA, 20 percet oad) (seeABB Review2/2012, p.46)

4 A triaguar woud core which cosists o three idetica corerigs. let: perspective mode. Right: mode see rom above

2 Compariso o TOC (tota owership cost) o stadard ad EcoDramorphous meta core trasormers (seeABB Review2/2012, p.47)

Capitalized loss First costs A = $ 10 W; B = $ 2 W

0 50 100 150 200

Standard

EcoDry

Relative costs (%)

Standard dry

EcoDryBasic Relative environmental impact (%)

0 20 40 60 80 100

Global warming potential(kg CO2-equiv.)

Acid iica tion p otentia l(kg SO2-equiv.)

Eutrophication potential(kg phosphate-equiv.)

Human toxicity potential

(kg DCB-equiv.)

Ozone layer depletionpotential (kg R11-equiv.)

Photochem. ozone creationpotential (kg ethene-equiv.)

Rectiier and converter transormers

Transormers or marine applications

Transormers or wind turbines

Air-core reactors

Iron-core reactors

Transormers and reactors or rolling stock

Respodig to a chagig word


24/76

In this symmetrical, triangular set-up, eacho the three core legs is linked directly tothe other two, and eature symmetrical and

short distances or the magnetic ux. Inaddition to the usual rectangular path viathe core rings, the ow o ux is also pos-sible via the triangular arrangement oyokes. I the magnetic ux in the yoke sec-tions o one o the core rings becomes toolarge and the yoke saturates, the ux canpass through the other two core rings,amounting to a ux through the threeyokes arranged in a triangle.

The TriDry triangular confguration enables

compact installation with a reduced oot-print and up to 20 percent less weight 5.

The symmetry o the technology resultsin transormers o the highest reliability,reduced in-rush current, reduced soundlevels, reduced magnetic stray felds andreduced losses 6.

Standards or losses or minimum efciencyvalues or transormers are dierent in di-erent countries. China is well advanced byhaving defned dierent efciency classes,

including standards or amorphous trans-ormers, or a number o years. In Europe,dierent loss classes or dry-type trans-ormers have been introduced only recent-

TriDry transormer. This small revolution intransormer technology uses a triangularcore confguration which restores the sym-

metry o three-phase AC systems. Similarto a generator or motor where the polesare arranged in a circular confguration,

TriDry phases also have a circular arrange-ment 4. This diers rom conventionaltransormers with a planar layout, wherethe phases arranged side by side resultin dierences between middle and outerphases, incomplete utilization o corematerial, and other defciencies.

The core o a TriDry transormer is wound

rom a continuous strip o magnetic steelwithout any joints, thereore avoiding therelated losses. The width o the steel sheetvaries in order to produce an almostD-shaped cross section o a core ring.

Three core rings o almost rectangularshape are mounted together to orm athree-phase core with triangular shape.Each core leg is made up o two D-shapedparts rom two core rings combined,resulting in a circular cross section. Sincethe core cannot be opened, the windings

are directly wound onto the core and vac-uum casting is also done directly onto thecore.


5 TriDr coiguratio reduces weight adootprit

6 Characteristics ad ratigs o ABB dr-tpe distributio trasormers

7 loss casses accordig to En 50541-1 ad positioig o TriDr ad EcoDr product amiies

The core o a

TriDry transormeris wound rom acontinuous strip omagnetic steelwithout any joints,thereore avoidingthe related losses.

TriDr

Compact, efcient, sae

Core: Triangular,continuously wound core

Coils: VCCround

Voltage: 1.136 kVPower: 1002,500 kVA

Special technical characteristics:symmetrical transormer

Benefts: Low lossDierent andcompact ootprintLow magnetic stray felds

EcoDr

Ultra-efcient transormer

Core: Amorphous 3-leg Evanscores, or stacked core

Coils: VCC, Resiblocrectangular

Voltage: 1.136 kVPower: 1004,000 kVA

Special technical characteristics:Amorphous core

Benefts: Minimum lossesMost interesting solutionin case o medium or highelectricity costsEnvironmentally benefcial

Stadard dr trasormer

Well proven and highest reliability

Core: Stacked core,3-leg

Coils*: VCC, VPI or Resiblocround, rectangular or oval

Voltage: 0.140.5 kVPower: 540,000 kVA

Special characteristics:Well-established and proven

Benefts: Non-ammableand sel-extinguishingNo maintenanceHigh short-circuitstrengthEasy installationLow-loss designs possible

Stadard

EcoDr Basic

TriDr

No-load loss (NLL)

A0-50%

Bk

Ak

Ak-20%Loadloss

A0 B0 C0

EcoDr Ultra EcoDr 99Plus

Note: Some products may not be available globally.


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25Respodig to a chagig word

ammable, does not need an enclosure,

and is comparable in size and weight tooil-immersed transormers. Due to its castaluminum windings, it is also not a targetor thet.

Creating the PoleDry transormer requiredsome special considerations. Eliminatingthe air gap between the primary and sec-ondary windings, which is typical o dry-type transormers, removed the risk ocontamination or ingress o animalsbetween coils, and is very important or

ensuring high reliability in an outdoor trans-ormer. PoleDry is thereore manuacturedwith solid insulation between the windings,and utilizes hydrophobic cycloaliphaticepoxy (HCEP) to encapsulate the wind-ings. This epoxy provides superior outdoorperormance in other applications, and isalso outstanding in terms o resisting fre,UV rays, erosion and external tracking.Bushings are cast together with the wind-ings, and are ully integrated to prevent anywater penetration. Simulations and experi-

mental tests were done to control the elec-tric felds, optimize the design and avoidany tracking on the surace. A fnal impor-tant eature is the cores special corrosionprotection.

PoleDry has been tested in the harsh out-door environment o ESKOMs KoebergInsulator Pollution Test Station (KIPTS) inCape Town, South Arica. KIPTS is close(30 meters) to the sea, which provides anenvironment that includes plenty o expo-

sure to UV, rain, wind and sand erosion,industrial pollution, salt-laden moisture,and wildlie 10. Coils and cores weretested in a salt-og chamber, which allows

ly, with the launch o EN 50541-1. Note

that the losses o the EcoDry amorphoustransormer are hal those o the best lossclasses specifed by EN50541-1 7, 8.Goig overheadOverhead distribution is common in manycountries and in rural areas. It is an easyand ast way to set up an electricity distri-bution grid and provide power to consum-ers. Transormers, or stepping down thevoltage used in overhead power lines tothe level needed by customers, are directly

mounted on the poles.

Traditionally, pole-mounted transormersare oil-immersed units. The oil makes verygood insulation, but presents environmen-tal and saety risks. I the transormer tankruptures or leaks due to an internal ailureor external damage, the liquid will run outand contaminate the ground. This is espe-cially problematic in protected water areas,in rivers and lakes, or public and nationalparks. In addition, leaking transormers will

also soon stop working.

In some countries, the thet o copper or oilrom pole-mounted transormers is an im-portant issue. Electric utilities not only haveto replace the damaged units, but alsoclean up and dispose o the oil-contami-nated ground, which is oten much moreexpensive than replacing the transormeritsel. And the risk related to inammableoil is an issue, especially in residential andorested areas.

To eliminate these problems, ABB devel-oped PoleDry, a dry-type transormer orpole-mount applications 9. It is non-

8 EcoDr amorphous trasormers provideutimate eciec over the whoe oad rage

9 PoeDr is a dr-tpe trasormer orpoe-mout appicatios

10 Characteristics ad ratigs o PoeDrtrasormer ad outdoor testig at KIPTS

Ultimate saety in overhead distribution

Core: Stacked core, 3-leg

Coils*: VCC, with cycloaliphatic outdoor epoxy

Voltage: 1.124 kV

Power: 50315 kVA, 3-phase

Special technical characteristics:

No air-gap between primary and secondary coil

Integrated bushings

Corrosion resistant core protection

Benets: Dry-typetransformerforpole-mount

application with size and weight

comparable to oil-flled unit

EnvironmentallyfriendlyUnattractiveforcoppertheft


26/76

risk o any piece o electrical equipmentailing can never be completely exclud-ed, the consequence o such a ailuremay be heavily dependent on the tech-nology used. With new dry-type trans-ormers, it is possible to minimize the

consequences o such occurrences.

Voltage classes or dry-type transormerstypically range up to 36 kV, and their ap-plication is mainly in the distribution grid.Following intensive research, ABB has in-troduced HiDry72, a dry-type transormeror the 72.5 kV voltage class. This meansdry-type transormers are now availableor sub-transmission voltage levels 12,13. Urbanization and the rapid growth omegacities requires more and more pow-

er in downtown areas, and using highervoltages to deliver it is benefcial.

Dry-type transormers are easily in-stalled in buildings or underground, anddo not require costly additional protec-tive equipment or other inrastructures,such as oil pits, etc. Since vacant spacein big cities is limited and expensive,these types o transormers not onlyprovide optimized perormance, butalso an improved appearance.

A number o new concepts had to be in-troduced in order to produce a dry trans-ormer at this voltage level, including

controlled and accelerated cycling be-tween phases with salt og, clean og andUV radiation up to 50 times as intense asnatural UV radiation [4]. The frst 20 com-mercial units, three-phase transormerswith a 100 kVA power rating and with 15 or20 kV primary voltage, are destined or theItalian utility, ENEL.

Goig udergroudAn opposi te approach was necessaryor the submersible transormer. Thisunit is suitable or underground installa-tions, in vaults or subways which areoccasionally, or requently, looded withwater 11.

An example o submersible transormerinstallations is the network transormersused in the city o New York (NYC). Thesethree-phase transormers with power rat-

ings o 500 to 2,500 kVA are connectedto a network protector, and serve loads inNew Yorks downtown. They are typicallyplaced in vaults under grates in the side-walks. In the event o heavy rain thevaults, which do not have drainage sys-tems, can become partially or ully ood-ed. In addition, all surace debris washedo rom the streets ends up in the vaults.

In traditional oil-immersed network trans-ormers, internal aults or short circuits

can lead to large, street-level explosionsand ires, which can cause signiicantharm to people and property. For thisreason Consolidated Edison (ConEd),the electric utility in New York, approached

ABB and asked or a dry version o thesetransormers. Pilot dry network trans-ormers have now been in operationsince the middle o 2011.

An important prerequisite was the drytransormers had to ft the dimensions o

the existing vault dimensions. They alsohad to contain a grounding switch inte-grated with the VCC transormer in arobust tank. This enables easy groundingin case the network requires maintenancework. The dry transormer itsel is mainte-nance ree, and is designed to be lowsound emitting or urban environments.Multiple arc-ault testing was required byConEd in order to prove the unit`s saety.

Feedig power-hugr cities

A burning transormer in an urban area,producing smoke and umes and widelyvisible to the public is a nightmare sce-nario or T&D operators. Although the

11 Submersibe dr-tpe trasormer oretwork appicatio


Dry-type trans-ormers are easilyinstalled in build-ings or under-ground, and do

not require costlyadditional protec-tive equipment orother inrastruc-tures.

Saety or environment and people


Coils: VCC, high temperature insulation system

Voltage: 1.117.5 kV

Power: 1001,000 kVA


Mounted in completely sealed enclosure

Low sound level

Benefts: Transormer installation can be ooded

Non-ammable and sel extinguishing

Applicable as network transormer

No risk o oil spills


27/76

27Respodig to a chagig word

The launch o ABBs new dry-type trans-ormer products addresses an important

need or sae and environmentally-riend-ly power products usable in a variety oapplications, including urban settingsand environmentally sensitive areas 14.It is now possible to use dry-type trans-ormers in certain applications or thevery irst time, thanks to ABB innovationsthat have increased energy eiciencyand made higher voltages possible incompact outdoor and submersible in-stallations.

directly cooled by air. The higher tem-perature rise o the dry-type transormer

makes cooling more eicient due toa higher temperature gradient andincreased radiative cooling at highertemperatures.

However, since dry technology requireslarger dielectric clearance distances, thecore and thereore also the mass o thedry-type transormer is slightly larger,which also results in a somewhat in-creased no-load loss. The load loss iscomparable to the load loss o an oil

transormer, so total losses are onlyslightly larger with a dry-type transor-mer.

HiDry72 transormers can be providedwith an on-load tap changer. They havehigh short-circuit strength, thanks tostrong reinorcement o the coils by thesolid insulation material and their cylin-drical geometry.

They are su itable or substa tion retroit s,

or or new installations, and parallelingwith existing oil transormers is possi-ble. Besides inner city and undergroundsubstations, HiDry72 is a perect choiceor power plant applications, substa-tions in or close to buildings, in cavernsor in protected water areas, and indus-trial applications such as chemicalplants or oil and gas installations. Forexample, two HiDry72 transormers rated25 megavolt ampere (MVA), 66/13.8-11.9 kV with on-load tap changers will

be installed in the new Estdio FonteNova in Salvador, Bahia, Brazil, which isone o the stadiums hosting the 2014FIFA Soccer World Cup.

shielding rings in the windings; conduc-

tive shielding pieces or the clamps andmagnetic yokes; rounded corners inwindings and shields; and an optimizednumber o barriers and barrier arrange-ments to control the electric ield in theinsulating air. The combination o numer-ical simulations and experimental testingon model devices and ull-size prototypetransormers helped ABB create com-petitive designs.

72.5 kV dry-type transormers require

a ootprint similar to oil transormers.While cooling equipment and radiatorsin oil transormers require considerablespace, dry-type transormer coils are

14 Success stor: power reiabiit or thewords taest buidig

When it was completed in January 2010,Burj Khalia in Dubai became the worldstallest building with 164 loors and a totalheight o 828 meters. To ensure powerreliability throughout the enormous building,it is equipped with 78 ABB dry-typetransormers, which are renowned ortheir mechanical strength and reliabil-

ity picture 4 page 9.

The nearby Dubai Founta in, which isilluminated by 6,600 lights and shootswater 150 meters into the air, is alsoequipped with ABB transormers. It is theworlds largest ountain.

12 Eectric ied itesit i a 10 MVA,72.5 kVA dr-tpe trasormer

13 Characteristics ad ratigs o ABBsHiDr trasormer or subtrasmissio

Marti Care


Zrich, Switzerland

[email protected]

Reereces

[1] Targosz, R., Topalis, F., et al, (2008). Analysis oExisting Situation o Energy Eicient Transorm-ers Technical and Non-Technical Solutions,Report o EU-IEE project SEEDT.

[2] Carlen, M., Oeverstam, U., Ramanan, V.R.V.,Tepper, J., Swanstrm, L. , Klys, P., Striken, E.,(2011 June). Lie cycle assessment o dry-typeand oil-immersed distribution transormers withamorphous metal core, 21st Int. Con. onElectricity Distribution, paper 1145, Frankurt.

[3] Singh, B., Hartmann, Th., Pauley, W.E., Schaal,S., Carlen, M., Krivda, A. (2011, June) Dry-typetransormer or pole mounted application, 21stInt. Con. on Electricity Distribution, paper 952,Frankurt.

[4] Krivda, A., Singh, B., Carlen, M., Hartmann, T.,Schaal, S., Mahonen, P., Le, H., ( 2011)

Accelerated tes ting o outdoor powerequipment, Con. Electrical Insulation andDielectric Phenomena, Acapulco, Mexico.

It is now possible

to use dry-typetransormers incertain applicationsor the very irsttime, thanks to

ABB innovationsthat have increased

energy eiciencyand made highervoltages possiblein compact out-door and submers-ible installations.

3D simuatio o the eectric ed itesit i a10 MVA 72.5 kV dr-tpe trasormer ad dieec-tric testig o the trasormer beod the imits

HiDr

Getting power into cities


Coils: VCC, Resibloc

Voltage: 40.572.5 kV

Power: 1,00063,000 kVA


Dry-type transormer or sub-transmission

(72.5 kV voltage class)

Benefts: Inner-city and underground installation

Water protection and fre risk areas

oil & gas and industrial applications


28/76



29/76

29The quiet ie

The

quiet lie

RAMSIS GIRGIS, MATS BERnESJ

Everoe is amiiar with the char-acteristic hum that trasormersproduce. I sparse popuated areas,this droe wi disturb ew, but iurba areas it ca be o cocer ad

ca eve a ou o oca oise evereguatios. Probab the strictestoise ordiace i the word iseorced i new york Cit, so, whe

ABB recet produced a umber otrasormers or the oca powerutiit, these had to be ver quietideed. This required a sigiicateort b ABB to deveop a uder-stadig o the processes ivoved isoud geeratio, trasmissio adradiatio i trasormers. Such

kowedge has eabed ABB tosupp successu ow- ad u-traow-oise trasormers to mamajor cities aroud the word.

ABBs ultralow-noise power transormers

Transormer hum is characterizedby several pure tones. The re-quency o a number o these is inthe range where the human ear is

most sensitive. Moreover, transormer noise,being o tonal character, causes irritation

and discomort. There are three sources osound/noise in power transormers:

Core oise

Core noise is caused by the magneto-striction property o core steel. It hascomponents atmultiples o 100 or120 Hz (or 50 Hzand 60 Hz trans-ormers, respec-tively). The relative

magnitudes o thenoise at the variousharmonics is de-pendent on corematerial, core ge-ometry, operatingux density andhow close the resonance requencies othe core and tank are to the excitingrequencies 1.

Cooig equipmet oise

Fan and pump noise is mostly broadbandwith insignifcant low requency tones.

load oise

Load noise is mainly generated by theelectromagnetic orces that result romthe interaction o the load current in thewindings and the leakage lux producedby this current. Another source o load

noise is tank vibrations caused by theleakage lux impinging on tank walls.

The main requency is twice the supplyrequency, ie, 100 Hz or 50 Hz trans-ormers and 120 Hz or 60 Hz trans-ormers.

Transormer load noise increases with theload. Also, at higher loads, ans ramp upand add urther noise 2.

Desig eatures o

ABB ow-oise trasormersPower transormers o ABBs present de-sign generation typically have noise levelsthat are signifcantly lower than those built

Power transormers oABBs present design

generation typically havenoise levels that are signii-cantly lower than thosebuilt 20 or 30 years ago.

Tite picture

Transorme rs si tuated in urban settings o ten haveto comply with very strict noise regulations.

Through comprehens ive techno logy developmenteort, ABB has been able to produce transormersthat comply with the strictest regulations around.


30/76


Sound panels or enclosures covering theentire tank, or parts thereo, have been

used or transormers that must ulfll verylow levels o noise. Winding resonance is avoided and

winding designs that provide or lowermagnitudes o leakage ux are used.

Tank vibrations are signifcantly reducedby shielding against leakage ux.

Lownoise ans, or soundabsorbingelements at the inlet and outlet, reducean noise. In the case o ultralow-noisetransormers, ans may not be usedat all.

CoEd trasormer requiremetsConsolidated Edison (ConEd) is a powerutility serving New York City. In order tosatisy the stringent limits that the city ordi-nance imposes on all sources o noisein the city, the ConEd specifcation or newpower transormers has stringent noiserequirements:

A 15 to 20 dB lower total noise levelthan is typical or corresponding sizeso transormers.

Guaranteed noise levels not to be

exceeded at 100 percent voltagecombined with 100 percent load or atmaximum over-excitation combinedwith 40 percent load.

20 or 30 years ago. Some o the moreimportant means to achieving these low

levels o transormer noise are: Transormer cores are now designed toprovide a more uniorm distribution omagnetic ux with a lower content oux harmonics in the core and core

joints. Detailed 3-D magnetic feldmodeling allows optimization o thecore and, thus, minimized core noise.

The core is held together by a clampingstructure that provides uniorm pressureon the core laminations while avoidinglocal deormations. ABBs inhouse

tools calculate the vibrations o thecore, taking dierent modes o vibra-tions and mechanical resonance, aswell as the complex orces exciting athreephase transormer core, intoaccount.

By careully considering the dynamicproperties o the transormer core andtank, it is possible to successullyde-couple corevibrations romthe tank. Also, a

number otechniques thatattempt toreduce thetransmissibility othe core vibra-tions, and hencethe resultingsound radiation, are exploited.

Both core and tank resonances areavoided. This entails accurate pre-deter-mination o resonance requencies.

Acoustic simulations, verifed by scalemodels and ull-size experiments, providethe tools needed to avoid core and tankresonances and reduce sound radiation.

The ConEd require-

ments impose otherdesign restrictions,such as tight limitson weight, widthand height to per-mit transportationin Manhattan.

1 Tpica requec spectrum o oise produced b a 60 Hz powertrasormer (lp = soud pressure eve)

ABB invested a signiicantR&D eort and were rewardedwith a contract rom ConEdto produce the irst ultralow-noise 93 MVA transormers.

30

40

50

60

70

80

120 240 360 480

Frequency (Hz)

Lp

(dB)

600 720 840 960 1080 12000

0

10

20

30

40

50

60

70

Soundlevel(dB(A)

0 25 250

2 noise compoets ad tota oise o a 250 MVA trasormer

MVA

50 75 100 125 150 175 200 225

Core noise

Fan noise

Load noise

Total noise


31/76

31The quiet ie

Accurate calculation o the requencyspectrum, and total spectrum, o corenoise at dierent operating core uxdensities.

Accurate calculation o core, tank andwinding resonances to ensure these aresufciently removed rom the main

exciting requencies o the transormervibrations.

Accurate calculation o load noise ordierent types, arrangements anddimensions o winding as a unction ocurrent density and or dierent tankshielding types.

Eective methods to reduce all compo-nents o transormer noise and anunderstanding o the contribution oeach.

Proper transormer mounting tech-

niques and a ull understanding o theirimpact on the dierent requencycomponents o the transormer noise.

Accurate indoor measuring techniquesor very low noise levels in a actoryenvironment in the absence o a soundroom or testing the transormer.

More accurate calculations allow opti-mized design margins and improve theeasibility o meeting such tough peror-mance specifcations 3, 4.

A success storAs o spring 2003, ABB had the technolo-gy to design low-noise transormers, but

Limits are enorced not only on the totalnoise levels but also on each individualrequency component o the transormernoise. Taken together, the maximum allow-able noise levels o the requency compo-nents correspond to a total noise level oabout 54 dB(A) at 100 percent voltage and

ull current. In comparison, transormers othis size would typically have noise levels inthe 70 dB(A) range or no-load (core plusans) noise alone. This dem

tranformers manufacturing

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