PERPETUAL PIONEERING Transforming history The ABB power story Thomas Fogelberg, Åke Carlsson

Imagine for a moment, a world with- out power : It would be a world without high- transmis- sion systems and there would be no means to economically transport electric power over long distances. Power supply infrastructure would have neither the economies of scale nor the pooling of reserves that it en- joys today. More recent developments that would not have occurred include international power trading and the large scale tapping of wind power in remote regions, with their respective benefits for customers and the envi- ronment. Growing concerns over grid reliability additionally reflect the need for transformers of sufficient capabili- ty and robustness. Without the trans- former, electrical power today would be less reliable, more expensive and more wasteful, and industries and homes would look quite different.

Through practically all the history of commercial transformers, ABB and its predecessor companies have been at the forefront of their manufacturing and ongoing development. In this article, ABB Review traces some highlights of this development.

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BB has always been well posi- 1000 km and 500 MW capacity. This distances between these and industri- Ationed to meet the demands of breakthrough in voltage and capacity alized areas. Even higher the power transformer market, rang- set a new standard in Europe 2 . were needed to make efficient use of ing from single pieces of equipment these power sources. In the second in point-to-point transmissions to vital This extra high voltage (EHV) strained part of the 1960s, the power company ingredients of interconnected power not only the design and manufactur- Hydro-Québec introduced 735 kV trans- systems sprawling over vast areas. ing capacity but was also a challenge mission (a level later called 800 kV). in testing. Long transmission lines Power and voltage development presented a risk of transient voltages. In the early 1950s, At the end of the nineteenth century, New and more stringent test proce- the transformer proved itself an indis- dures had to be established for the Sweden commissioned pensable component for competitive dielectric integrity. These new tests the world’s first 400 kV transmission of electric power. A were then incorporated into the ac- 20 kV setup was demonstrated at the ceptance tests of the transformers. transmission with a length electrotechnical exhibition in Frank- of about 1000 km and furt am Main in Germany in the year Soon much of Europe was following 500 MW capacity. 1891, proving the feasibility of power Sweden’s lead in adopting 400 kV transformers. Two years later, ASEA, EHV. The Canadian province of Que- one of ABB’s parent companies, sup- bec had a similar situation to Sweden, In the USA, the building of large plied one of the first commercial with limited fossil fuel but abundant thermal power plants gathered pace, three-phase transmissions in Sweden – hydro power, and large geographic with plants reaching block sizes of from a hydro power plant to a large 1000 MW and more. For such large iron ore mine some 10 km away. plants to be viable, the power had to 1 An early three-phase transformer built to be distributed over long distances a patent of Johan Wenström patent, the Transformers made it possible to gen- covering vast areas. A 765 kV system technical genius of the early years of ASEA. erate electric power at low voltages was therefore introduced in addition Wenström called his transformer triple- and then transform it to a higher level to an existing 345 kV system. converter at which transmission incurs consider- ably lower losses, and finally trans- While 765 kV systems were being form the voltage back to a safer level built, existing 500 kV systems were at the site of consumption. being extended. One example of development work on large intercon- Transformer manufacturing emerged nection transformers concerned the in most countries in Europe and in early 400 MVA single phase units rated the USA. ASEA, BBC, , 500/161 kV that were delivered to Westinghouse and other companies Tennessee Valley Authorities, TVA. rapidly gained expertise in the manu- facturing and installation of trans- The first deliveries from ASEA in Lud- formers 1 . At the time, these were all vika for this purpose used a five-limb domestic companies with technology core with three limbs wound in paral- of their own serving local state-con- lel. Later, the number of wound limbs trolled utilities in tight partnership. was reduced from three to two for the same rated power. Finally the last Countries such as Sweden delivery to the same specifi- with practically no domestic cation was built with one 2 The Harsprånget 400 kV generator step up transformers: fossil fuel reserves but ample wound main limb and the Single-phase units with three low voltage windings to serve three potential for hydro power – voltage regulation part on one generators in parallel, each generator rated 105 MVA albeit remote from the user – of the side limbs. On all these were especially eager to transformers, the high and make use of electric power low voltage windings were transmission. As transmission separated; ie, there was no distances increased, the auto connection. transmission voltage had to rise to keep losses down and In addition to saving man- to reduce the number of hours in manufacturing be- lines needed in parallel. cause of fewer wound limbs, the transition from the earlier In the early 1950s, Sweden to the later design reduced commissioned the world’s the total dry mass by a quar- first 400 kV transmission ter. Also the total losses with a length of about (no-load and load losses)

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were reduced by about 20 percent. sulted in renewed interest for voltages 3 The 1785 kV UHV transformer installed at After completion of these deliveries, in the range of 1000 to 1200 kV in the AEP-ASEA test station outside South the customer started to acquire and China and India. Bend, USA. The transformer is installed install auto-connected transmission on an insulated platform to study the effect transformers whose specifications of line voltages up to 2200 kV phase-to- were otherwise the same. The majority of transformers are built phase on the core type concept – a concept In the early 1970s, TVA commissioned that today can be described as cylin- its first 1200 MVA power plant at Cum- der-shaped windings arranged con- berland, Tennessee. ABB Ludvika built centrically on a cylinder-shaped core. the generator step-up transformers An alternative design concept is the (rated 420 MVA) to a single-phase de- so-called shell type concept where the sign. These transformers represented a windings have a rectangular shape technical breakthrough in terms of and segments of low and high voltag- power capacity on one wound limb. es are more or less interleaved. For certain applications the shell type At the same time, ABB Ludvika concept has found a viable position; launched a development program to- eg, large generator transformers with gether with American Electric Power, special requirements. The large differ- AEP, – the largest private power com- ence in production techniques for the pany in North America – with the aim two designs makes it feasible to have of finding the highest technically fea- different workshops for the two con- sible transmission voltage. For this cepts. ABB has therefore allocated the purpose, ABB built a full-size single- production of most of its shell type phase network transformer whose transformers to its factory in Spain. highest voltage was 1785 kV, rated at 333 MVA. The transformer had one Restructuring of manufacturing footprint wound limb, and with a core extend- Power transformers were previously ed to three wound limbs on a five- considered to be more or less strate- 4 1000 kV test setup with transformer limb core, the capacity would have gic products, and several countries and shunt reactor at ENEL research been 1000 MVA per phase; ie, a total deemed it important to have domestic station in Italy capacity of 3000 MVA for a complete manufacturing capacity. Thus ASEA three-phase bank. The transformer established close ties with existing was installed and operated at the re- transformer manufacturers and estab- search facility jointly run by ABB and lished new factories in several coun- AEP. The transformer served success- tries such as Germany, South Africa, fully until completion of the research USA, Canada, Norway and Brazil. program 3 . BBC, with transformer factories in Germany and Switzerland, established Similar development programs were a factory in Brazil. Westinghouse sup- also embarked upon by some of ported the build-up and provided ABB’s other predecessor companies – know-how to factories in Italy, Spain aiming to achieve transformer designs and Australia. capable of handling transmission volt- ages of 1000 kV and above. One ex- Power transformers are complex “engi- 5 One of six converter transformers installed ample is a full-size transformer and neered-to-order” products requiring at the receiving end of the Pacific intertie shunt reactor built in Italy for 1000 kV competence and experience in engi- transmission serving the Los Angeles area and installed at ENEL test station neering and manufacturing. Such a Suveto 4 . business should be built up around de- fined instructions which are reflected Changing patterns in power produc- in tools in engineering and production. tion and grid build-up deferred the move to still higher transmission volt- In order to make efficient use of avail- ages and extreme transformer capaci- able resources, design and production ties. Voltages higher than 400 kV in methods were unified for all factories Europe and 800 kV on other conti- within the group. ASEA’s Ludvika fac- nents have so far not been commis- tory served as a technical resource sioned for commercial operation. The and gave advice and support on tech- need for high capacity, long distance nical and manufacturing issues. Once transmission – eg, to reach large and a year – or more often when needed – remote hydro power stations – has re- the technical and manufacturing man-

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agers met for an exchange of informa- and d.c.-potential applied on the stand to benefit from the use of high- tion and to learn the latest news on valve side of the transformer implied er voltages than are currently avail- development work. Engineers from new technical challenges for the trans- able. The environmental advantages the different companies were often former engineer. The harmonics give lie in the lower transmission losses invited to Ludvika for training and rise to additional losses, which need and the reduction in land use for the education, and highly skilled Ludvika to be taken into account and mini- right of way. engineers were given the opportunity mized to avoid dangerous local over- to serve in leading positions in the heating in the transformer. The d.c.- The phase shifter individual companies. potential on valve windings results in The power flow in highly meshed a dielectric stress pattern different high voltage transmissions needs to Design rules and manufacturing proce- from the stresses generated by the be controlled to achieve an efficient dures were documented in special normal a.c.-voltages. load distribution between power lines standards or instructions covering indi- in parallel. The load in the individual vidual phases in the process of build- Several transformer tech- ing transformers. This way of working 6 400 kV quadrature booster with a made it possible to accumulate sub- nologies as well manufac- throughput capacity of 1630 MVA, stantial experience in each phase of turing plants and proce- installed in the Italian network for power the design and manufacturing of the control of the interconnection between power transformer. The large total dures had to be unified Italy and France production base additionally made it within the shortest possi- possible to maintain and support a ble time – and this without comprehensive development team. lessening the momentum The close cooperation between the of normal production. individual manufacturing units contin- ued after the forming of ABB. All par- ticipating units were given access to The design of the modern converter common information and support transformer has its origin in the units from all employees within the ABB built for the Itaipu project in Brazil group. The IT tools used in design in the 1980s. A d.c. transmission volt- and engineering are now the same age of 600 kV was achieved with two around the globe. series-connected converters. In this means of connection, the transformers Long distance transmissions for the upper bridge must be capable 7 A reactor from 1923, built for short circuit For improved utilization of existing of a dielectric withstand of 600 kV. protection and control lines and rights of way, three types of There are a total of 24 single-phase equipment have emerged: HVDC con- converter transformers at each end of verter transformers, phase-shifters and the HVDC transmission, with a total shunt reactors. capacity of 6000 MW. The transformer is built as a single phase unit with two HVDC converter transformers valve side windings, one for delta Transmission with HVDC has several connection and the other for wye con- advantages when it comes to long-dis- nection (both being needed to reach tance transmission. The mode was the necessary phase split). The two first used on long cable transmissions valve side windings are built on sepa- to reduce the need to mitigate the rate limbs on a common core and act excessive voltage build-up along the electrically as two independent trans- cable caused by reactive power in an formers1). a.c. transmission. In HVDC transmis- sions, the power transformer not only In 2004, ABB delivered single-phase modifies the voltages to permit power units with a rating of 620 MVA to the to be exchanged between the a.c. and Pacific Intertie (USA) for a d.c. trans- d.c. systems; it also transforms the mission voltage of 500 kV 5 . These a.c.-voltage from a three-phase system are the largest converter transformers Footnotes to a six-phase system. This permits manufactured so far. 1) Parallel to the HVDC transmission, an 800 kV the harmonics generated by the valve a.c.-transmission runs from Itaipu to the Sao Paolo currents to be reduced. Furthermore, Presently ABB is in the final stage of area – this was mainly built by the BBC factory in Mannheim. the transformer acts as a barrier for the development of converter trans- 2) See also Asplund, G., Ultra high voltage transmis- the d.c.-potential, preventing d.c.-volt- formers for 800 kV d.c. transmis- sion, Alternative scenarios for long distance bulk 2) age from entering the a.c.-system. sions . Long point-to-point transmis- power transmission – 800 kV HVDC and 1000 kV Current harmonics from the valves sions, especially in China and India, HVAC, ABB Review 2/2007 pp. 22–27.

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lines is governed by the phase dis- of a device transforming power from The modern shunt reactor was intro- placement between the nodes in the one voltage level to another, but its duced in the late 1960s using compo- transmission system. A phase-shifter similarity in construction and manu- nents and technology from the core provides a means to control this dis- facturing makes it a highly suitable type transformer 8 . placement and thus the load flow. product for a transformer plant. The design of the modern Such a phase-shifter is installed in The reactor found its application in series with the power line and has an the early part of the last century as an converter transformer has outgoing voltage equal to the incom- efficient piece of equipment for the its origin in the units built ing voltage but with a (variably) shift- control of overcurrents and thus short ed phase angle. With only a limited circuit protection 7 . for the Itaipu project in need in phase-angle shift, the com- Brazil in the 1980s. plexity of the phase-shifter can be Long-line transmissions as well as ex- reduced to produce a quadrature volt- tensive cable networks on high volt- age only and the apparatus will be age generate a substantial amount of Industrial transformer called a quadrature booster 6 . Physi- reactive power. If not balanced, criti- A substantial segment of the ABB cally a quadrature booster is built as cal voltage rises develop during low product family is made up of large two transformers: one magnetizing loads. A reactor (the shunt reactor) transformers for industrial applica- unit and one series unit3). installed between the power line and tions, such as furnace transformers earth provides an efficient means to and rectifier transformers 9 . These The shunt reactor control and balance such reactive gen- transformers are characterized by the The reactor (sometimes called induc- eration. Essentially, the shunt reactor comparatively low voltage on the sec- tor) is not a transformer in the sense acts as a sink for reactive power. ondary side – but have appropriately high currents. Load currents of 60 kA or more are not unusual. These high Repairing an HVDC transformer in Drommen, Norway currents with their high harmonic contents pose significant challenges, especially in terms of high magnetic fluxes around exit leads within the tank and around the airside part of the leads.

In furnace transformers, the high currents are accompanied by frequent short circuits during the initial phase of the heating of the steel in the melt- ing pot. The resilience to such short circuit forces and the requirement for large regulating ranges call for special care in design and manufacture.

Forming ABB In August 1987, the Swedish ASEA and the Swiss-German BBC decided to merge and jointly form the ABB company. Shortly afterwards, ABB was also able to acquire the transformer manufacturing segments of Westing- 8 A 150 Mvar shunt reactor in the 9 An air-cooled rectifier transformer house in the USA, Ansaldo in Italy Swedish 400 kV grid rated 91.74 MVA and Spanish factories. The National Industry in Norway and the Finnish Strömberg had become part of ASEA just before the merger.

In fact, ABB can today, through its various predecessors, claim the com- bined experience of 700 years of transformer manufacturing Factbox . Several transformer technologies as well manufacturing plants and proce- dures had to be unified and made

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to work together within the shortest exploration of innovative transformer cooled windings based on cable tech- possible time – and this without less- designs. Studied design concepts in- nology (two units in service). By em- ening the momentum of normal pro- cluded superconducting transformers barking on these and similar more or duction. This was truly a gargantuan (a 630 kVA saw one year of service) less speculative projects, ABB has task. with HTSC4) winding conductors, high acquired a vast quantity of knowledge voltage foil-wound windings (three that it also applies to conventional A number of task forces and R&D units in service), large dry and air- transformer technology. And even if groups were established to evaluate the individual technologies and to se- Factbox TrafoStarTM, 700 years of pedigree lect the most viable ones. Although the principle of transformer technolo- gy is universal, there are many differ- ABB can today look back on the combined predecessors in its global, common business ences in the fine-tuning. Major objec- experience of 700 years of transformer concept: TrafoStarTM-platform. tives were lower costs, shorter pro- manufacturing, having inherited designs and duction time, and higher quality mea- expertise from the following companies: Each TrafoStarTM transformer follows com- sures in terms of test room failures. Asea mon engineering, supply chain and manu- It was important to package all design Ansaldo / Ital Trafo / IEL / OEL / OTE facturing rules. A modularized construction and production variables into a seam- BBC allows a high level of re-use, reducing factory less engineering IT system supporting GE, USA throughput time, while minimizing variation customized engineering and manufac- National Industri and achieving highest quality. The production turing. Strömberg of 1400 units a year provides a base for a Westinghouse unique performance and key parameter anal- ABB succeeded in unifying its tech- and more … ysis, permitting continuous improvements in nology, and today offers the same all plants. product and high standard of quality These 700 years reflect the knowledge ABB wherever the transformer is manufac- has of different technologies in transformer ABB’s customers do not benefit only through tured, be it in Germany, Canada, Bra- design and manufacturing, combined with the new transformers the company delivers. zil, India or China. Power transform- service experience in the networks around The broad knowledge base, now document- ers are expected to deliver reliable the world. ed in the TrafoStarTM concept, permits ABB service for 30 to 40 years in all types to provide service and support on all of networks. ABB draws on this considerable knowledge- 400,000 power transformers now in service base and combines the best practices of its around the world. Several of the participating manufac- turing plants needed substantial reno- vation and modernization to fulfill the ABB is delivering reliable power transformers by ... ABB standard when it came to clean- Low loss and low Strict sound active part Building blocks liness and competence for building quality control (core and windings) in parametric measurements transformers meeting today’s require- modules Hot-spots ments. Many new greenfield invest- under control ments were made permitting a quick Low life-cycle costs ramping up of production using this common technology base and with Outstanding short-circuit Low partial discharges substantial help from engineering strength test support teams. ABB established an record engineering training school in Germa- Low-loss core ny: the Knowledge Communication Center.

The increased manufacturing volume Rigid resulting from the formation of ABB core made it possible to initiate several clamping development programs, including the Gasket system for superior tightness

Footnotes 3) A quadrature booster uses a shunt transformer to Leak-free and phase-shift the supply voltage by 90 ° (hence the robust tank term quadrature). The output of this shunt trans- Continuously former is tapped, permitting the amplitude to be transposed Surface protection for every cables varied. A series transformer is then used to add this environmental condition Precise winding tolerances to the main circuit. 4) HTSC: High Temperature Superconductor

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the market has still not fully accepted duced the risk of unforeseen opera- western world. The existing capacity these innovations, the solutions are tional difficulties during a long service was more or less sufficient for cover- available. life. ing demand. The abundant availability of oil reduced the need to convert In view of the total capacity of the After the merger, ABB had developed energy supplies into electricity. This newly formed ABB, the transformer a range of transformers covering the led to overcapacity in the power segment could continue its predeces- full transmission chain, from genera- transformers market. sor’s active participation in interna- tion to the outlet socket in the resi- tional bodies such as CIGRÉ, IEC and dential home. The transformers used At the same time, the economy in the IEEE. This participation has made it in the last steps of this chain are gen- Pacific Rim as well as in the Far East possible to establish standards on test erally called distribution transformers. picked up and the need for electric levels and test procedures to verify These transformers are more or less power surged. Transformer plants in transformer integrity under various bulk products built to suit the net- Europe and North America had to operational conditions. The applica- work topology in each individual close while new ABB factories were tion of stringent quality requirements r egion of the world 10 . established in China and India. in design and manufacturing has re- ABB makes full use of its knowledge What about the future? and capacity in developing and manu- Transformers based on the induction More than the sum of its parts: assembling a facturing strategic transformers materi- principle will remain the base of volt- transformer als and components in special plants. age conversion for many decades to In this respect, high quality products come. Changes in the materials used such as transformer boards and wind- will help reduce both costs and better ing insulation kits manufactured ac- control of thermal capability. These cording to the company’s own tech- developments will affect conductor nology must be mentioned. ABB is materials as well as solid and liquid also one of the world’s major suppli- insulation materials; however, no sub- ers of all types of tap changers and stitutes for the electrical steel and the bushings. The company’s own tech- transformer core are in sight. nology in transformers, insulation materials, tap changers, bushings and In the future, new ways of rating up-coming transformer electronic transformers through better control of control places ABB in a unique posi- the thermal capability will help reduce tion in being able to offer a complete the use of expensive materials. Trans- product portfolio in transformers and former specifications must evolve to provides a strong basis for future place more emphasis on the load pro- development. file, future growth and emergency loadings – with the hottest areas for In the late 1980s and aging being covered by new stan- dards. The new ways in which such 1990s, expansion and international standards will rate trans- 10 An ABB in Brazil build-up of generation and formers will require the integration of more intelligence. Other goals are transmission slowed to further increase the mechanical, down in the western thermal and dielectric integrity of world while new ABB transformers – to make them better equipped to deal with the greater factories were established stresses that will affect future net- in China and India. works.

Geographical shift in production The impact of the formation of ABB Thomas Fogelberg was largely limited to Europe, where ABB AB, Power Transformers most of the transformer manufacturing Ludvika, Sweden plants were located. Later on, acquisi- [email protected] tions on the North American continent followed. Åke Carlsson Former Senior Electrical Engineer However, in the late 1980s and 1990s, ABB AB, Power Transformers expansion and build-up of generation Öhr Klockaregård and transmission slowed down in the S-342 64 ÖR, Sweden

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