POWER TRANSFORMERS

ABB ELEKTR‹K SANAY‹ A.fi.

ABB worldwideABB is an electrical engineering company with global operations in approximately 1000 companies, withmore than 200,000 employees all araund the world. The ABB worldwide group operation is concentratedinto five business segments:• Power Plants• Power Transmission and Distrubition• Industrial and Building Systems• Transportation• Financial ServicesThese five business segments are in turn divided into 45 business areas, each responsible for globalstrategies, business plans and product development. A global group of this scope offers advantages ofscale in basic research, product development, low-cost manufacturing and management expertise. Yet ineach country, ABB operations are local and flexible. The art of being local worldwide, having technologicalleadership, customer focus and commitment to sustainable growth, has placed ABB in the forefront inmeeting it’s short and long term objectives.

ABB TurkeyABB has been active in Turkey since 1969, in the fields of hydro and thermal power generation, powertransmission and distribution, rotating machines and drive systems, rail transportation, and automationof industrial processes for Turkish industries.

ABB Elektrik Sanayi A.fi.ABB Elektrik Sanayi A.fi. is located in the Kartalarea on the Asian side of ‹stanbul.The main activites at the Kartal factory are:• Power Transformer production• Distribution Transformer production• Transformer ServicePower transformer production at ABB ElektrikSanayi A.fi. is one of 25 production facilities inthe ABB Business Area, Power Transformers.• LV panels are manufactured at Dudullu factory.

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INTRODUCTION

ABB Elektrik Sanayi A.fi. has been producing powertransformers since 1969 at the Kartal Factory. Duringthis time, ABB has been able to meet the increasedrating demands and fulfill customer requirements.Power transformers from 5 MVA up to 400 MVA and400 kV, are produced at the Kartal factory. Morethan half of the power transformer production isexported.

160 MVA 15.75/162 kVStep-up transformer

50 MVA 132/69/13.8 kVAutotrasformer

250 MVA 380 / 158 kV Autotransformer 40 MVA 150 ± 8 x 1.25 % / 10 ± 2 x 2.5 % kV transformer

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DESIGN

The specifications and individual requirements ofthe customer are the starting points for the designand production of each transformer. We combinethe customer’s requirements with a high level ofquality in the following design and productionphilosophy.

Highly standardized working methods are appliedthroughout the whole product range.

Transformers are custom made, using standardizedelements and components. Computers with verywell developed systems have taken over all thedesign and production routines. These systems andprocedures are based on the acquired know-howas well as the latest findings from both Researchand Development and the experience gained duringproduction.

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CORE

Tranformer cores are manuf›actured from cold rolledgrain oriented and silicon alloyed carbonless electricalsteel. Super-oriented and laser treated super-orientedsteels are also used in order to fulfill the customer’slow-loss and reduced noise level requirements.

Core form is the general comcept for our transformers.A boltless, sophisticated core design minimizes eddycurrent losses and gives thermal and mechanicalstability as well as low vibration and low soundlevel.

The core is built up by means of stepped sheets toform circular core cross section and 45° mitred jointsat the corners.The state of the art step-lap technique is also usedfor further reductions on core losses and noise level.Flat and thin insulation of the electrical steel sheetmakes it possible to improve the space factor withsubstantial improvement in losses and other no-loadparameters.

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Yoke plates are firmly pressed between core clampsto achieve the required friction forces in the cornerjoints. The lamination of large cores is held togetherby means of a semiconductive ASECOND fiberglasstape which has been wound under tension andcured to form a cylinder. For smaller cores, anepoxy-cementing technique is used. The windings

are kept under pressure by flitch plates for largercores and by tie-bolts for smaller ones. To preventmovement of core sheets during manufacture andtransport, special side-supports are placed at eachcorner.

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WINDINGS

Windings are designed to meet relevant standardsand specifications in respect to short-circuit strength,temperature-rise and insulation requirements.

The conductor material is paper covered high qualityelectrolytic copper. ›n the case where there are manystrands in the conductor bunch, continuouslytransposed cable can be used as a winding conductor.Disc winding is used for high voltage winding. Forhigher voltages the interleaved form of the disc

winding has a great advantage to increase seriescapacitances and consequently to obtain uniformtransient overvoltage distribution on the winding.

Helical type windings are used for most low-voltagewindigs. Each turn consists of a group of conductorswhich are continuously transposed to reduce eddylosses.

Regulating winding is a helical type of winding anddesigned in such a way that each tap windingsegment is evenly distributed over the entire lengthof the main windigs. By using such windings, theampere-turn distribution provides an electromagneticbalance regardless of the selected tapping position.

In order to reduce the leakage flux losses shuntblocks are placed on the top and bottom sides ofthe complete limb windig set and/or inside the tanksurface.

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Winding Insulation:

All the insulation materials used in the winding toform the required insulation and oil cooling ductswithin the winding, are made of high quality electricalpressboard intended for use in transformers. Theinsulation, between the windings and between thewinding to the core is of the oil-pressboard barriersystem. The dielectric strength of this system isdecisively better than the oil duct system with thesame distance.

Winding Production:

Specific and modern machinery and tooling isused for accurate and precise production ofwindings.After the winding operation is completed, thewindings are dried out in the insulating material.The dried windings are compressed and heightadjusted under compression. These processeswil l increase the dielectr ic withstandingcapability of the insulation material and make

the windings more stable and strongeragainst short-circuit forces.

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ASSEMBLY

The windings are assembled on the core in theassembly area, which is constantly maintained clean.All connections from the windigs to the tapchangerand bushings, are made by paper insulated cablesand busbars, and those are braced by pressboardprofiles to provide required insulation distancesbetween the conductors and earth, and to makethem stronger against short-circuit forces. The jointsare made by high frequency brazing technology andcarried out by trained personnel with brazingcertification. In regular intervals, some joints are

submitted to a recognized testing laboratory forquality checks. As the windings can take in moistureduring the assembly process, a forther drying processis applied to the complete active part, and a finalpressing operation is carried out on the windings.After putting the active part into the tank, filteredand degassed new oil is filled into the transformerunder vacuum. Particle reduction by circulation andfine filtering of the oil increases the dielectricalwithstand capability of internal insulation of thetransformer.

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TANK

The tank, cover and conservator are manufacturedof steel plate. The complete tank together with allflanged connection is capable of withstandinghydrostatic over pressure and full vacuum.

Double welding is used where the oil tightness isrequired. The weldings are made by qualified welderswith welding certification. All the weldings arechecked with a penetrant liquid and with the x-rayswhen necessary.

Oil sealing is provided by an O-ring nitril rubbergasket system. Nonmagnetic steel is used aroundthe high current carrying bushings to reduce theeddy-current losses.The surface of the tank, cover and conservator arecleaned from rust and other impurities by grid-blasting, with a surface quality of at least Sa 2.5according to Swedish Standards.The inside of the tank is covered with oil resistantpaint and the outer surfaces are painted with epoxybased two-component paints.

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MAIN ACCESSORIES

ON-LOAD TAP-CHANGERS

In most of the transformers on-load tap-changers(OLTC) are used. Available types of on-load tap-changers are in-tank type, which can be built in thetransformer tank and out-of-tank type, which canbe installed on one side of the transformer tank.The diverter switch of the on-load tap-changer is ina separate oil compartment. The on-load tap-changeris operated by means of a motor-drive mechanism.

DE-ENERGIZED TAP-CHANGERS

De-energized tap-changers are used in most of thestep-up transformers and, upon customers request,in some of the step-down transformers.

BUSHINGS

The bushings for voltages below 52 kV and forcurrents below 4500A are normally made of porcelain.For higher voltages and higher currents oilimpregnated condenser type bushings which arepartial discharge free up to test voltage are used.The long creepage distance requirements can bemet by the shed form of anti-fog type.

Some importantfeatures of on-loadtap-changers:• High-speed

transition resistortype

• Very short arcingtime

• Contact life will bethe same as theeconomical life ofthe transformer withnormal operationfrequency

• Minimummaintenance

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COOLING EQUIPMENTCooling class ONAN/ONAF (OA/FA)• Vacuum proof radiators• Shut-off valves are provided on the connection

between the radiator and the transformer tank.• At ONAF (FA) cooling, the forced air stream is

produced by fans with low noise level.

Cooling class OFAF (FOA)• The heat exchangers with the fans.• The oil pump is driven by a totally oil immersed

motor

Cooling class OFWF (FOW)• Tube and plate heat exchangers are used• To prevent any contamination of the oil by water

and/or outside moisture, each cooler is madewith leakage protection, double wall or doubletube.

OIL PRESERVATION SYSTEM

For large transformers and upon customers requestfor medium-size transformers, the conservator isprovided with a rubber sack. Normally, an openconservator system is used for small and medium-size transformers. In case of high contaminationand/or high humidity at the site, the transformersare equipped with rubber sacks.

OIL

The oil used in the transformers fulfills therequirements of IEC 296.

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STANDART SUPERVISORY AND CONTROL EQUIPMENT

• Control cabinetcontaining contactors and protective devices forcooling equipment and/or terminal blocks for thesupervisory and control equipment.

• Top oil temperature-indicatorwith up to four isolated and separately adjustableelectrical contacts and a sensor placed in an oil-tight pocket on the cover.

• Winding temperature indicator (thermal image)with up to four adjustable electrical contacts.

• Gas operated relayis normally located on the pipe connection fromtransformer tank to conservator. The shut-offvalves are placed on both sides of the relay. Therelay has electrical contacts for gas collectionand/or sudden oil rush from transformer tank toconservator.

• Pressure relief devicewith electrical contact.

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• Oil level indicatorwith electrical contactsfor too low and toohigh oil levels.

• Dehydrating breather

SUPERVISORY AND CONTROL EQUIPMENT (UPON REQUEST)

Following accessories can be supplied upon request.• Automatic voltage regulation• Equipment for parallel operation of on-load tap-changers• Current transformers• Cable boxes• Remote indication of instruments• Transmitter for remote temperature indication• Transmitter for remote tap-position indicator• Surge arresters mounted on a bracket placed on the transformer tank• Protective capacitors with supporting brackets placed on the tank

• Valvesfor filling, draining,filtering and sampling of the oil.

• Pressure relayfor tap changer

• Bi-directional wheels, flat base or skids.

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TESTING

The following routine tests are performedon the transformers in accordance withIEC and other national standards:

• Winding resistance

• Voltage ratio and check of phase vectorrelationship

• Measurement of load losses andimpedance voltages

• Measurement of no-load losses and no-load current

• Dielectric routine tests

• Tests on on-load tap-changers, whereappropriate

• Measurement of insulation resistance

• Measurement of capacity and tangentof insulation loss angle.

The type and special tests which areporformed on request are as below:

• Temperature-rise test

• Lightning impulse test

• Switching impulse test

• Induced over-voltage test with partialdischarge measurements

• Measurement of zero-sequenceimpedance

• Measurement of acoustic sound level

• Measurement of the power taken by thefan and oil pump motors

All of our transformers are tested to verify they have been designed and constructed to withstand conditionsstipulated by international and national standards.

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TRANSPORTATION AND INSTALLATION

Upon request, a transformer can be transported fromthe factory to the installation site.

Before transport of the transformer, important partsand accessories, such as bushings, conservator,cooling equipment and other minor items aredismantled and properly packed, seaworthy packingwhen necessary. An impact recorder is placed onthe main body of the transformer for overseastransportation, upon customer request. The mainbody, for large and some medium-size transformers,is transported without oil and filled with dry nitrogen.The transformer oil is transported in specially treateddrums.Transport and erection activites, depending on theweight and size of the transformers, are carefullyplanned and executed by highly qualified personnel.

Our skilled engineers and technicians carefullyprepare the transformer for service operations at theinstallation site. All the dismantled parts andaccessories are reassembled during erection. Thedry nitrogen, which has been filled for transport, issucked out, and the filtered and degassed new oilis filled in to the transformer under vacuum. A finalon-site test is performed to ensure a long and trouble-free operation of the transformer.Upon request, regular inspection and maintenanceof the transformer can be done by our servicespecialists on site.Oil sample can also be taken by our service staffand chromatographic gas analysis dissolved in theoil is done to check the condition of the transformer.On service and transformer mainetance, training ofthe customer’s personnel can be carried out at ourfactory or at any site in accordance with customerrequiremets.

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RESEARCH AND DEVELOPMENT

Concentrated points in research and development activities areadvanced insulation systems, loss reduction, more compacttransformer design and increased efficiency. To reach these goals,we benefit mainly from ABB BA Power Transformers Researchand Development Center and the other research centers andlaboratories within and outside ABB. Some research projects arealso executed in cooperation with qualified universities.

Theoretical aspects of a transformer development project arecarried out by experienced engineers who have expertise in theirrespective fields. Results are verified by running full scale testingin order to avoid extrapolation mistakes.

The development of manufacturing techniques is also a part ofresearch and development activities. The manufacturing techniquewhich affects the quality and reliability of a transformer is carriedout in close cooperation with design, production and developmentengineers.

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QUALITYASSURANCE SYSTEM

Our Quality Assurance system is based upon the procedures andinstructions in force within the company, from marketing andsales to site service of delivered products.

The quality assurance system of ABB Elektrik Sanayi A.fi. meetsISO 9001 requirements and was certified by internationallyaccredited certification bodies.

Our ultimate quality goal is customer satisfaction. Our productsmust be in conformity with customer specification.

ABB Elektrik Sanayi A.fi.Power TransformersKartal FactoryEsentepe Mh. Milangaz Cad. No:52 34870 Kartal-İstanbul/TÜRKİYETelephone : +90 216 528 22 00 e-mail : info@tr.abb.comTelefax : +90 216 353 88 07 web : www.abb.com/tr

+90 216 353 94 55

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