BULB UNITSTHE COMPLETE SOLUTION FOR LOW HEADSPOWERAlstomHydroisthenumberoneglobal provider of clean power solutions accounting for around 25% of the worlds installed hydro base and offers the worlds most compre-hensiverangeofhydropowergeneration facilities and equipment. It is not surprising then that Alstom bulb units providethemostefficientsolutionwhen faced with very low and low heads up to 30m. Bulb units have now virtually replaced Kaplan turbines for low head situations.The name bulb comes from the shape of the upstream watertight casing which contains a generator located on a horizontal axis. Units are submerged in the water passage and, as theturbinesareusuallydoubleregulated, areabletohandlesignif icantdischarge variations. The straight water passage in the draft tube improves the hydraulic behaviour of the unit, and also results in a low submergence. This, in turn, allows for a reduction in size, cost and civil works requirements of up to 25%. There are hundreds of Alstom bulb units now in operation around the world with more than 35 large units commissioned in China alone during the last ten years.The company has been an ardent pioneer in thedevelopmentofbulbunitsintroducing many outstanding innovations in size, design and operational effciency and will continue the research and development programme to extend the application range. Both standard- ised and customised solutions are offered. Specifc technologies have been developed to adapt to customers needs and site surround-ings such as the use of mobile or fxed guide vanes and runner blades, shaft lines on 2 or 3 bearings, and pit turbine technology with a speed increaser. Alstom has gained outstanding knowledge andexperienceindesign,manufacturing, installation,commissioningandmanage-ment of complex bulb projects in a vast range of environmental conditions, making Alstom bulb units without doubt the worlds most reliable solution.ALSTOM BULB UNITSFOR BEST PERFORMANCEAlstom bulb units application rangeModel scale bulb runner2CONSTANT R&D TO MEET ENVIRONMENTAL CONCERNSAlstom is also committed to helping custom- ersbalancecommercialobjectiveswith environmental and social responsibilities.Increasing environmental concerns are taken into account resulting in fsh-friendly turb- ines. In bulb turbines fewer but longer blades decrease the fsh mortality, while maintaining effciency levels. Oil-free operations that prevent the pollution of rivers have also been developed, resulting for example in runners lubricated by water in many bulb units.PLANT INTEGRATORIn the field of power generation, Alstom is theplantintegratorspecialist,combining skills in component design, auxiliary systems, construction and plant optimisation. Alstoms answer to the markets growing need for turn- keysolutionsisauniquecombinationof in-house core components and customised plant solutions based on the integration of complementary packages. This original combination creates more value forcustomersthanthesimpleadditionof individual packages by optimising:Investment costs Lead timesPerformance and availability Retroft solutionsPlant life cycleCustomer value-drivenGLOBAL OPTIMISATIONAnAlstombulbuni tdeli versmaximum customervalueandreturnoninvestment. Equipment investigation and design is carried outbyexperiencedinterdisciplinaryteams as part of the total system optimisation.Alstoms global geographical coverage and the largest installed base allow the feedback ofexperiencetobetakenintoaccount foreachnewproject,whilstitslocalpre-sence guarantees a perfect understanding of regional variations.ThankstoaglobalR&Dorganisation,the maindesignparametersaredef inedby hydraulic, mechanical and electrical engineers working in close collaboration. This leads to improved results for the bulb outer dimension by considering and evaluating factors such as productivity, global effciency, civil work, investmentandreliabilityofthepower- generating unit. Theabilitytoof fertheworldsbroadest scope of power generation equipment and systems enables Alstom to deliver complete optimised solutions, from turbines and gen- eratorstocontrolsystemsandbalanceof plant, including a full turnkey service.The Alstom product range covers complete electromechanicalandhydro-mechanical equipment for new hydropower plants, as well as for the rehabilitation of existing plants.DISTRIBUTED CONTROL SYSTEM Alstom has a proven worldwide experience in control systems for the power industry. Over 500thermal,hydraulicandnuclearunits have been equipped in 25 years.Taking advantage of its in-depth knowledge of the hydro power plant processes, Alstom has developed a comprehensive control and instrumentation system, providing modern operating control for hydro power plants. Alstomsautomationproduct,commonly knownasALSPAP320system,isthe most suitable system to control and monitor Alstom hydro power plant. The system comprises three major parts: Centralog provides the operator control inter- face and control room environment with high availability and high performances Controbloc automation cells execute the controlandprotectionfunctionsofthe machines and connect to the process. The use of feldbuses allows geographical distribution of the equipment Controcad provides a set of advanced engin- eering tools both for the design offce and the on-site high quality documentationALSPA P320 provides many features and benefitsfortheplantownerandoperator including: Hi-techtechnologies:objectoriented engineering, internet, feldbusIntuitive, user friendly operator interfaceModular design conceptAdaptable multifunction controllersDistributed control architecture Open system architecture based on inter-national standards Highperformance,communicationnet-works Integrated comprehensive Plant Manage-ment System (integration of Alstom expert software)HydroprocessCentralisedplantanddammanagement software are embedded in the central super-vision system, providing a set of functions managingtheactiveandreactivepower production of the power plant as well as the dam and the reservoir water level. Al stomsengineeringdepar t menthas acquiredavastexperienceincontroland instrumentationsystemsforallkindsof hydro power plants. Its expertise in providing tailormadesolutionsguaranteesoptimal plant control implementation.General design of a bulb unitNina Power station (China)3Alstom has developed advanced technology to optimise all hydraulic parameters. This ensures that turbine designs perfectly match the targeted characteristics of a given pro-ject, while taking into account any necessary constraints.Duringthehydraulicdesignphase,unit per f or mancesar epr edi ct edt hr ough theoreticalinvestigationandexperimental developments. Each component of the turbine is fnely tuned, from intake, stay vanes and distributor, to runner and draft tube. Alstoms objective is to optimise effciencies, minimise dimensions and reduce downstream head losses.THEORETICAL INVESTIGATION AND SCIENTIFIC CALCULATIONS Alstom has developed many software codes to perfect shape design, from classical ones to those based on full 3D surface generation using global optimisation algorithms. These permit the exploration of new design families and allow the best shapes to be verifed on a test rig.During the design process, deep numerical investigationsusingthelatestCFDcodes (ComputationFluidDynamics)arecarried out. These simulate the fow in the turbine overthewholeoftheexpectedoperating range and help to determine the best adapted turbine shape. They allow the accurate determination of all hydraulic parameters, such as load analysis, effciency and cavitation behaviour.HYDRAULIC DESIGNState-of-the-art facilities and toolsfor optimised designsDownstream velocity feldTurbine pressure feld4MODEL AND SITE TESTINGOnce a design has been defned theoretically, its performance is validated by model tests in an Alstom Global Technology Centre.Two recent test rigs, one of which has been inoperationsince2003,areusedforbulb turbines,withup-to-datecalibrationtools and automated acquisition systems.Theseadvancedf aci l i t i espermi tver y accurate measurements that are also a key tool for performance improvement and act as afurthercompletecheckofturbinebehav- iour, including effciency, output, cavitation, runaway and torque on blades.Once all the investigations are completed, the full scale turbine is manufactured and tested on site if required. It is due to this continuous process of research, design and testing that Alstom remains the world leader in innovative bulb unit technology.Alstom has more than 100 years of exper- ience in the expert analysis and production of speed governing products.The speed governor is the brain of hydraulic turbines.Itfulflsalltherequirementsand needs of hydraulic turbine applications.These systems fulfl various functions:Speed governi ng i n i sol at ed or i nt er- connected networks Fast unit start and speed stability control under no-load operating conditions Automaticunit/networksynchronisation throughrunnerblades,guidevanesor downstream gate controlFlow or load regulation Efficiencyoptimisationwithrespectto head and load Autonomous sluicing operation at variable or steady fowsBlade/guide vane cam relationshipNEYRPICT.SLG(TurbineSpeedLoad Governor) is the latest product developed by Alstom.Itisinterfacedwithanautomated system to ensure fexibility of use.Designedtooperateinthemostextreme environments,themainbenefitsareits highlevelofadaptability,robustnessand reliability.GOVERNING SYSTEMUniversal turbine test rigT.SLG governor with actuatorsDedicated bulb test rig5To ensure the safety and reliability of all units, Alstom carries out a continuous mechanical R&D programme on all turbine parts. Duringmechanicaldesign,thecomplete bulb structure is analysed by Finite-Element calculationscoveringstresses,deflections and eigenfrequencies to check the static and dynamic behaviour of the entire unit.STAY RINGThe stay ring is the sole support structure of the unit. This provides many advantages:Weightsandverticalloadsareevenly distributed in civil engineering structuresAxialforcescarriedtotheanchorare limited to hydraulic loadsCivil works are simplifedThetwoverticalarmsofthestayringare hollow for generator bus bar outlet and piping. This also allows easy access to the shaft seal for adjustments.DISTRIBUTOR The conical distributor comprises 16 moving guide vanes. They are guided on self lubricat- ing bearings and controlled by an operating ring.To ensure continuous operational safety, the distributor can be closed under both normal and runaway conditions.Foruni t swi thadownstreamgate,the operating ring is actuated by two push-pull servomotors. Shear pins are used as safety devices for the guide vanes.Inthecaseofnodownstreamgatebeing installed,theservomotorsuseacounter weight to close the guide vanes safely.A self-resetting device is then used instead of a shear pin, to avoid the unit shutting down in the event of a guide vane jamming.WHAT IS DIFFERENT ABOUT ALSTOM HYDRO PELTON TURBINES? MechAnIcAL DeSIgn Safety and ReliabilityFinite-Element dynamic analysis6RUNNERS UP TO 9M DIAMETERRunner design is one of the most important tasks that Alstom carries out when optimising a unit for each project.Blades can be directional, driven by a moving servomotor cylinder located inside the runner hub.Runner hubs are normally flled with oil, but for environmentally sensitive locations, water may be used as a lubricant.SHAFT LINE AND BEARINGS Tworadialbearingsensurethedynamic stability of the horizontal shaft line during operation.The combined axial-radial bearing is located next to the centre of gravity of the generator rotor. It carries the weight of the rotor and the force of the unbalanced magnetic pull when the machine is in normal operation.Incaseofdoublerotorearthfault,huge rotating forces act not only on the bearing, but also on the bearing and bracket supports. The axial bearing is designed for steady-state conditions of the turbine and also for dynamic hydraulic transients.Theturbineguidebearingissupportedby a semicircular plate that allows it to follow the shaft movements. Generator and turbine bearings are both shell type bearings.Thrust and counter-thrust bearing pads are designed to handle the axial hydraulic force. The counter-thrust bearing is stressed for a few seconds in case of load rejection.Thethrustbearingpadsaresupportedby membranes to ensure even load distribution, independent of the shaft movements.Bearingandthrust-bearinglubricationis carried out by gravity from an oil tank located above the unit. This very simple process has proven to be extremely reliable.DOWNSTREAM GATEA draft tube gate provides a reliable protective system for bulb units.The downstream gate is suffciently remote from the runner to have a limited effect upon thedesignofthedrafttube.Itsshapeis designed to avoid the accumulation of solid deposits on the side grooves.Downstream gate functions are:Protection against runaway conditions Downstream isolation during unit dewater- ingSluice operationForunitswithoutcontroldevices(f ixed distributor),thedownstreamgatealso initiates unit starting, coupling, progressive loading and shutdown.Since the draft tube is embedded into concrete as a frst stage, the stay ring is set into the civil engineering structures. Then the shop-assembleddistributorisfitted.Theshaft, pre-ftted with bearings, thrust bearing and counter-thrust bearing, is then inserted into the assembly.The shaft line is adjusted on site so that the generator rotor and the turbine runner are centred on the theoretical axis of the unit.An initial adjustment is made by eccentration of the guide bearings following the shaft line calculation. The fnal process is completed on site, centring the stator on the rotor and the runner chamber on runner blades.Thefollowingoperationsarecarriedout simultaneously: Erection of rotor, stator and bulb nose in the upstream pit Erection of the runner hub, blades, turbine cone and runner discharge in the down- stream pitErection of accessoriesErection TimeOPTIMISATIONRunner erectionBulb shaft line and bearings assembly7Alstom design concepts ensure reliability in all operating circumstances taking account of the bulb units sensitivity to instability and vibrations due to the horizontal position of the generator. They have been developed to handle conditions such as roundness and air gap concentricity, and have been success-fully applied in bulb units up to 60 MVA. STATOR DESIGNAlstomstatordesignsincorporatespecial V- shapedel ement swi t hsi gni f i cant operational advantages. They guarantee the necessary stiffness required of the structure, with less radial height compared with trad- itional design concepts. They also ensure the necessaryspacebetweenstatorcoreand casingrequiredforefficientaircirculation through the cooling slots. The Alstom stator key bar design, in combina-tion with the spring effect of V-elements and stator core pressing system, provides vital protection against stator core buckling.ROTOR With the introduction of oblique elements forhydroelectricgeneratorstwodecades ago, Al s t oml aunchedane wer ai n large generator design, offering outstanding mechanical performance.Oblique arms connect two concentric annular parts, the rotor hub and the rotor rim, allowing them to turn in relation to each other. The application of oblique elements on the rotor provides improved radial precision and a uniform air gap under all load conditions.Oblique elements are used in the rotor spider toprovideoptimumresilienceregarding thermalexpansion,centrifugalforceand operational torques. Compared to classical designs with radial arms, oblique arms offer many advantages. Machinetorqueonlystressesthearms in the tensile direction while oblique arms absorb rim expansion due to centrifugal force and thermal dilatation by allowing rotation oftheriminrelationtothehub.Alstom rotor design also permits stacked rotor rims without shrink ft to the rotor spider. ADvAnceDGENERATOR DESIGNBulb generator rotor with oblique arms8VPI INSULATION SYSTEM Thereli abili t yofthest atorwindingi s determinedprimarilybythequalityofits insulation.Ageneratorisheavilystressed thermall y,electricall yandmechanicall y duringoperation.Thismakestheheaviest demands on insulation. The MIcADuR vacuum pressure impreg- nationsystem(vPI)hasbeenusedby Alstom for more than 40 years. Thes ys t emhasbeencont i nuousl y researched and further developed and has produced excellent results on all machines even under severe conditions.The uniform VPI production process ensures a high insulation quality with the following properties: The requirements of temperature class F are met Highdielectricstrengthandvoltageen- durance values with low loss factors Provensystemforalltypesofelectrical machines up to 30 kVExcellent corona-resistance Very good resistance to oil, water and other coolantsExcellent mechanical propertiesOtherVPIinsulationsystemscanalsobe provided.AIR COOLING SYSTEMThe closed air ventilation system is designed for safe operation at maximum output and maximum river water temperature.To guarantee high unit availability, the cooling system is generally installed with a redundant complete cooling device.Inordertoprovidemaximumvalueto customers, Alstom offers integrated solutions in combination with the secondary cooling circuit. Thanks to its vast experience in bulb generatordesign,Alstomalwaysdelivers maintenance-free and reliable solutions. Areliableexcitationsystemisthekey totrouble-freegeneratoroperation.It ensures fast and effcient reactive power and voltage control, and the best possible generator performance overall.Alstomautomaticvoltageregulatorsand excitation systems have been produced for more than 35 years with the installation of 2,850 systems controlling 315,000 MVA in 130 countries.To guarantee optimal results, all Alstom gen- erators come with a high quality excitation system as a standard. Formediumandhighspeedmachines, brushless excitation systems are provided. Synchronousmachinesaresuppliedwith rotating diodes. This supplies DC-current to the rotor without any brushes or slip rings, which are commonly subject to wear and tear. Both solutions are equipped with the latest automaticvoltageregulation(P320AVR) technology.AllAlstomstaticexci tationsystemsin- corporatestate-of-the-arttechnologyand the required redundancy provision.FieldEXCITATIONWedging of the stator bar in stator core9WORLDWIDEProject highlightsCANADABromptonville 1997 - 1 unit, 11MW, run. dia.: 3.75m.Saint Lambert 1995 - 1 unit, 6.2MW, run. dia.: 4.50m.USAWorumbo 1989 - 2 units, 10 MW, run. dia.: 4.25m.Greenup 1982 - 3 units, 25 MW, run. dia.: 6.10m.Rock Island 1978 - 8 units, 58 MW, run. dia.: 7.40m.BRAZILOurhinos 2004 - 3 units, 15MW, run. dia.: 4.25m.Canoas 1999 - 6 units, 27MW, run. dia.: 4.70m.Igarapava 1999 - 5 units, gen.: 44 MvA.AUSTRIAPfarrwerfen 1995 - 2 units, gen.: 11 MvA.CROATIACakovec 1982 - 2 units, 42 MW, run. dia.: 5.40m.FRANCESaint Egreve 1990 - 2 units, 23.4 MW, run. dia.: 5.60m.Argentat 1989 - 1 unit, 17 MW, run. dia.: 4.10m.Sault Brenaz 1986 - 2 units, 23 MW, run. dia.: 6.25m.Chautagne/Belley 1980 - 4 units, 46 MW, run. dia.: 6.40m.Caderousse 1975 - 6 units, 32 MW, run. dia.: 6.90m.Sauveterre 1973 - 2 units, 33 MW, run. dia.: 6.90m.La Rance 1966 - 24 units, 10 MW, run. dia.: 5.35m.GERMANYHeidelberg 1997 - 2 units, 2 MW, run. dia.: 3.35m.Guttenbach 1992 - 1 unit, 3 MW, run. dia.: 3.16m.HUNGARYTisza 1973 - 4 units, 7 MW, run. dia.: 4.30m.LUXEMBOURGSchengen 1995 - 2 units, 2.4 MW, run. dia.: 3.50m.PORTUGAL Crestuma 1987 - 3 units, 43 MW, run. dia.: 6.80m.TURKEYSeyan 2 1992 - 3 units, 3 MW, run. dia.: 3.50m.SWITZERLANDRheinfelden 2007 - 4 units, gen.: 25 MvA.Ruppoldingen 2000 - 2 units, gen.: 12 MvA.La Rance, France 196610Alstomhasequippedmorethan250bulb unitsintheworldforatotaloutputof approximately 5,000 MW.SOUTH KOREANam Gang 2000 - 2 units, 7 MW, run. dia.: 3.00m.Paldang 1999 - 4 units, 31.5 MW, run. dia.: 5.20m.CHINAChangZhou2007-3uni t s,42. 9MW,run.dia.: 7.50m.Tong Wan 2007 - 4 units, 46.2 MW, run. dia.: 7.10m.Qiao Gong 2007 - 4 units, 58.5 MW, run. dia.: 7.45m.Wu Jin Xia 2007 - 4 units, 36.1 MW, run. dia.: 7.00m.ZhiGangLaKa2005-4units,39.0MW,run.dia.: 6.10m.Ni Na 2003 - 4 units, 41.0 MW, run. dia.: 6.00m.Hongjiang 2003 - 5 units, gen.: 47 MvA.GongChuan2001-2uni t s,22. 2MW,run.dia.: 5.50m.Sha Xian 1999 - 3 units, 16.5 MW, run. dia.: 4.90m. INDIA SoneLinkCanal1986-6unit s,2MW,run.dia.: 3.22m.Rock Island, USA 1976 Wu Jin Xia, China 200511ALSTOM Hydro4, avenue Andr Malraux92309 Levallois Perret Cedex - FRANCEwww.power.alstom.com/hydroPWS/BPROB/BLBNTS09/eng/HYD/01.09/FR/6786 ALSTOM 2009. All rights reserved. Information contained in this document is provided without liability for information purposes only and is subject to change without notice. No representation or warranty is given or to be implied as to the completeness of information or ftness for any particular purpose. Reproduction, use or disclosure to third parties, without express written authority, is strictly prohibited. - Photo credits: Alstom 2009 - Design & Layout: www.kineka.com.