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Revelstoke, CanadaHarnessing thepower of waterGenerating electricity from the power of water represents largeamounts of clean, renewable energy. Seventy-one percent of theearth’s surface is covered by water. So far, the installed world shydropower potential is 4 million GWh/year. There remains ahuge hydropower potential of 16 million GWh/year.2

Hydropower is a clean, renewable and environmentally friendlyenergy source – with low carbon dioxide emissions. Hydropower plants have the highest operating efficiency of allrenewable energy generation systems. They are largelyautomated, and operating costs are relatively low. Hydroelectric power plants also play an important role in waterresource management, flood control, navigation, irrigation andin creating recreational areas.Customer focused and innovativeVoith is a leading full-line supplier and an industry leader inthe production of generators as well as trusted partner forequipping hydropower plants all over the world. Our portfolioof products and services covers the entire life cycle and allmajor components of hydropower plants: Generators Turbines Pumps Automation systems Spare parts Steel structural components Maintenance and training services Digital solutions for intelligent hydropowerGlobal expertsAs part of our international network, each Voith facility operates under the same cutting-edge platform and is equippedwith consistent best-in-class processes and tools. Thisnetwork also ensures that we can meet special customizedrequirements – from individual components to project planning, through project management and plant maintenance.With branches and production facilities for electrical andhydraulic machines and components in Europe, Asia, Northand South America, we are close to our customers and activein all major hydropower markets worldwide.Technical reliability with highest quality standardsVoith has been known for quality right from the start. We striveto continuously meet our own high aspirations in terms ofquality: Our global certification is based on well-known international standards (ISO) for quality management environmentalprotection as well as occupational health and safety. Moreover, we have developed our own methods for quality assurance and work according to them. In this way, future generations will continue to benefit from the quality of our work.A world-class laboratoryUsing state-of-the-art technologies and innovative digitalsolutions, we are committed to developing customized longterm solutions in hydropower in the years to come. At theVoith Hydro Engineering Center, scientists, engineers andmeasurement technicians access more than 100 years ofknow-how and can make use of one of the most modernhydraulic laboratories in the world. Combined with the deepdomain knowledge that evolved over decades from more than40 000 units delivered to customers, this environment pavesthe way to innovations of the existing product portfolio as wellas new technologies.3

CharacteristicsFor well over a century, Voith has supplied the world’s largest andmost powerful hydroelectric units with respect to both performanceand size. As we push the envelope in hydropower technology, Voithfocuses on customized solutions for utilities.Power demand increases with the expansion of the economyand improved living standards. Following this trend, thecapacity of generating units has also increased, growing from6.25 MVA at Necaxa in 1903 up to 840 MVA at Three Gorgesin 1997 and now to more than 855.6 MVA at the Xi Luo Duand even 944.5 MVA at the Wu Dong De power station. Theseare the most powerful generators designed and manufacturedby Voith today.To improve optimum project economics, higher unit capacitymachines are often used in order to reduce the number ofunits at each plant. For compact machines, direct water cooling is very effective. Within the renewable energies, pumpedstorage plants play a new role with the use of variable speedtechnology to directly support grid control.Frades II is a milestone in hydropower: thanks to their variablespeed based of DFIM (Doubly Fed Induction Machine), thepumped storage units designed and supplied by Voith canadapt their number of revolutions continuously and take orprovide power from and to the grid.4Above this, the asynchronous motor generators can also beutilized for frequency stabilization of the grid. The highly sensitive control systems react to grid variations within milliseconds, can tap the kinetic energy of the flywheel masses of themotor generators, and provide immediately energy to the grid,or respectively absorb energy from it. Facing variations in thegrid, the motor generators react extremely fast and in the caseof faults can compensate v oltage drop accordingly – and thus enhance security of power supply.With a maximum continuous output of 433 MVA and a speedrange from 350 rpm to 381.2 rpm, those are the most powerful variable speed motor generators in Europe built so far.Another milestone in hydropower is the powerhouse atLimberg I in Austria. The built-in synchronous full invertermachine provides a maximum continuous output of 81.5 MVAand a speed range from 400 rpm to 750 rpm.

History of generators and motor generatorsRating (MVA*)1 1001 008611200751000314921900 1910 1920 1930 1940 1950 1960Projects1 Necaxa, Mexico2 Herdecke, Germany3 Suiho, China4 Vianden, Luxembourg5 Furnas, Brazil6 El Chocon, Argentina7 Rottau / Malta, Austria8 Wehr, Germany9 Santo Antonio, Brazil10 Jirau, Brazil11 Riel (SC**), Canada12 Raccoon Mountain, USA13 Paulo Afonso IV, Brazil14151617181920212223242519701980Helms, USABath County, USASamrangjin, South KoreaBath County MOD, USAFrades II (DFIM***), PortugalChang Long Shan, ChinaBelo Monte, BrazilGuri II, VenezuelaItaipu, Brazil / ParaguayThree Gorges, ChinaXi Luo Du, ChinaWu Dong De, ydrogen* Mega volt ampere** Synchronous Condenser*** Doubly Fed Induction Machine5

Design criteriaVoith is setting milestones with its generator technology.Customers benefit from our deep understanding of sophisticatedengineering and conceptual competence in project execution.And at the same time, our engineers incorporate the causeand effects of the related components of the entire plant. Wemaster the interplay of thinking outside the box and traditionalengineering in order to provide a highly reliable generator thatoffers the state-of-the-art technology.We keep in mind what customers are looking for: efficiency,easy handling, absolute reliability. Two of the world’s mostpowerful synchronous generators are part of the Xi Luo Dupower plant in China with a maximum output of 855.6 MVA at125 rpm and the Wu Dong De power plant with a maximumoutput of 944.5 MVA at 90.9 rpm.Generators and motor generatorsRating (MVA)950Wu Dong DeThreeGorgesGrandCoulee850750Xi Luo DuItaipu 50 HzGuri IIItaipu 60 Hz650Air-cooling550Revelstoke 5Bath County MODBath CountyRaccoon Mountain450Water-coolingSamrangjin350Frades II DFIMHelmsGuangzhou IISilzRodund II newRodund II250ChongpyongWehrMalta150Akköy II5000100200Air-cooled generatorsWater-cooled generators6300400500600Air-cooled motor generatorsWater-cooled motor generators7008009001 000 Speed (rpm)

Frades II, PortugalThe following design criteria influence the generator’smain dimensions In order to ensure a long and reliable operation, it isessential that operational temperatures are aligned withthe allowable limits of the materials, especially those ofthe winding with respect to the applied insulation system. The required moment of inertia must be provided withinthe given stator bore dimensions:– to enhance the grid stability and improve the LVRT(Low Voltage Ride Trough) characteristic– to increase the time until the power unit achieves therunaway speed– to reduce the water hammer pressure– to guarantee turbine regulation at shutdown At runaway speed the mechanical stress incurred bythe rotating parts shall be designed within the maximumallowable stresses of the specific material and loaduniverse for static as well as dynamic integrity. A safety margin is provided between the first critical speedand the unit’s runaway speed. A shorter and lighter rotorhelps to achieve this margin. For air-cooled machines, a shorter core length and a largerdiameter might be suitable for uniform cooling along theentire core length and windings.water-cooled units at Itaipu (Brazil / Paraguay) rated at823.6 MVA and the 840 MVA units at Three Gorges (China).These records have been broken with the totally air-cooledgenerators for the Xi Luo Du power station (China) with a ratedoutput of 855.6 MVA and for the Wu Dong De power plant(China) with a rated output of 944.5 MVA.All Voith generators are designed and manufactured withthe latest state-of-the-art technology including the use ofVacuum Pressure Impregnation (VPI) for the stator bars andcoils. Rated voltages up to 25 kV are part of our standardproduction.3D generator modelsVoith has vast references in water-cooled machines and hasdesigned the world’s largest and most powerful air-cooledhydropower generators, including Guri II (Venezuela) ratedat 805 MVA and the 672 MVA units at Grand Coulee II (USA),as well as the world’s largest and most powerful directly7

Our Service –Part of YourBusiness.1Keep your energy flowingHyService and modernizationOver decades, generators have been running reliably. To ensurecontinuous and first-class operation in the future, extensive serviceand maintenance will be indispensable to prevent or solve yourproblems effectively.8

21 Manual bar assembly into a 70-year-old stator with semi-closedslot in a generator workshop of Voith Hydro, Norway2 Application of end-winding reinforcementVoith offers comprehensive and tailor-made first-class serviceand moderniztion solutions. Reliable service management incorporates the idea of thinking forward. Our HyService teamsat Voith offer repairs, spare parts, preventive maintenance,inspections and assessments. Our focus is clear: Voith is yourpartner to extend the lifetime of your hydropower plant at anypoint of its life cycle. And we want to keep it running smoothly. As an experienced service partner, we support you in anypart of the plant’s operation. Reliable. Experienced. Availableall around the world.Consider our modernization project of the pumped storageplant Wehr in southern Germany. By completely renewing themotor generators, Voith increased the efficiency and especially the reliability of the machines. This included the refurbishment of the stator and rotor using modern state-of-the-artcalculation methods, materials and design features. During theBath County modernization that started in 2005, we deliveredsix new state-of-the-art stator windings and later six completely new rotors; each motor generator now has a rated output of530 MVA instead of the original 389 MVA.This helped, among other modernization measures, to reestablish Bath County as the pumped storage power plantwith the highest power output in the world. For a successfulmodernization such as these examples, you have to considerthe complete design of the plant and at the same time investigate the different options for service, refurbishment andrenewal of every single part of your generators. We at Voithdevelop new, high-quality parts and refurbish existing parts todeliver what you really need. For instance, our engineers thinkof individual solutions to deliver the outstanding Micalasticinsulation from our modern factories in Mississauga (Canada),São Paulo (Brazil) or Shanghai (China).Get in touch with us! Contact:HyService@Voith.com9