Subtitle (Arial 22)

1. May 11, 2006 Subtitle (Arial 22) Hydropower Refurbishment – Alstom’s Methodology and Case Studies Presented By Naresh Patel ( Electrical) Sreenivas.V ( Mechanical) - Add text to be highlighted here -

2. Introduction • Alstom Power – Hydro Products • Descended from Neyrpic, ASEA, BBC, Alsthom • Over 100 years experience in hydro industry • Eng’g & Mfg’g in Americas, Europe & Asia • Presence in Asia Includes: • Turbine, Generator, Hydro Mech, P&S, BoP • Design & Mfg’g in Tianjin, China • Design & Mfg’g in Vadodara, India

3. The Need for Refurbishment Repair, Modernize & Uprate • Repair – Equipment failure results in units out of service / operating at derated output • Most compelling of refurbishment drivers • Issue – Return to full service quickly • Solution – Often a temporary “band-aid” • If ‘quick fix’ not possible, modernize and uprate options should be considered

4. We should have done this last year as a planned outage!

5. The Need for Refurbishment Repair, Modernize & Uprate • Modernize – Apply new technology, materials and calculation techniques • Normally done in conjunction with other refurbishment work • Example – Uprate field-coil insulation during a stator rewind • Example - Install self-lubricating bushings during runner replacement

6. The Need for Refurbishment Repair, Modernize & Uprate • Uprate – Increase the output capability of the generating unit • Most economically feasible of drivers • Typically 15 to 40% uprate without civil-works modification • Minimum scope usually involves runner replacement and new stator core & winding • BoP modifications have to be considered

7. GENERATOR LIFE CYCLE

8. Refurbishment Methodology General Philosophy • Refurbishment presents more challenging design requirements than that of new units • Interfaces between old & new equipment have to be considered • Existing unit must be synthesized • Collection of reliable data for existing units is absolutely necessary for a successful project

9. Refurbishment Methodology Data Collection • Review of specification and data from spec • Site visit absolutely necessary for: • Measurements and visual inspection of unit • Assess the installation environment & limitations • Collection of additional data, eg maintenance records, test & operational data, OEM drawings, etc. • Discussion of refurbishment requirements and Q & A with customer engineers • Duration of site visit is scope dependent and can last from a few hours to a few days

10. Generator Specific Methodology Proposal Design • Refurbishment of the generator and turbine parts will be presented here separately, but the shaft coupling is an important interface for matching of capability and maximum speed. Generator and turbine design are performed together • Relatively short time for design • Synthesis of existing design required with accurate model of components to be kept • Model of existing design is modified for refurbished parts • Modeling is only rigorous enough to ensure the solution will work and to guarantee performance

11. Generator Specific Methodology Basic and Detailed Design • Continuation of the proposal design • A second site visit is essential • Additional generator testing may be required to validate the model of existing unit • Analysis is much more rigorous and can include electromagnetic & mechanical FEM studies • Interface issues are resolved during detailed design

12. Generator Specific Methodology Synthesis of Existing Generator • Required data are rarely all available • Physical model is created from dimensions given in spec and from site visit • Electromagnetic model, including excitation requirements and reactances are correlated to test & operational data • Thermal model, including ventilation configuration and airflow are correlated to measured temperatures & losses • Throughout the synthesis, measured data are used to deduce unknown dimensions and material properties • Additional tests may be required after award of contract

13. Modeling of the Refurbishment New Winding • Small scope with very little design space • Optimize temperature (output) and efficiency • Slot dimensions are fixed so the only variables are: • Insulation thickness (design for hipot or VET) • Strand dimensions • Typically a 15% uprate is possible if replacing asphalt bars or coils • Upgrade field insulation during outage

14. Modeling of the Refurbishment New Core & Winding • This scope allows a change in winding configuration • Important to identify core-replacement need at time of tendering through inspection or El Cid test or by the age of the core

15. Allatoona Stator Core ~ 45 Years Old

16. Modeling of the Refurbishment New Core & Winding • This scope allows a change in winding configuration • Important to identify core-replacement need at time of tendering through inspection or El Cid test • Possible to achieve large increase in efficiency

17. STATOR-STEEL QUALITY

18. Modeling of the Refurbishment New Core & Winding • This scope allows a change in winding configuration • Important to identify core-replacement need at time of tendering through inspection or El Cid test • Possible to achieve large increase in efficiency • Possible to eliminate noise problems • Keying and clamping system should be replaced • Effective soleplate modifications not usually possible unless frame also replaced, i.e. new stator

19. Modeling of the Refurbishment New Poles and Field Coils • In conjunction with a new stator & ventilation modifications, can allow up to a 40% uprate • Torque transmission of other components plus BoP has to be checked explicitly for >15% uprate

20. Modeling of the Refurbishment Refurbishment with Larger Scope • Begins to look like design for a new machine with fewer interfaces, fewer dimensional and performance limits • In these cases, the limits are given by the civil works and balance-of-plant components • Optimization of performance and output has much higher opportunity

21. Generator Case Studies Rocky Reach, Units 1-7 • Customer – Chelan County PUD, Washington State • Existing unit - 120 MVA, 15 kV, 90 rpm, 0.95 pf • Airgap instability • Stator-core buckling • Increase of efficiency • Some units noisy, > 95 dB • Life extension / increased availability • Scope – new stators & rotors - everything except shaft, brackets & bearings

22. Rocky Reach, Units 1-7 Design Requirements • High efficiency – main design driver • US$55k / kW evaluation, US$70k / kW penalty • Airgap shape tolerances one half of IEC/CEA standard • Low audible noise, <80 dB 1 m from housing • High evaluation for short outage

23. Rocky Reach, Units 1-7 Design Solutions – High Efficiency • 30% more active material than benchmark, • Increase frame OD to accommodate larger core & frame – radial clearance in housing reduced to limit • Losses & temperatures very low, so ventilation system can be optimized for efficiency not cooling • Airgap reduced to allowable SCR limit of 0.8 • Relative to existing machine, the efficiency was increased by 0.5% to almost 99%

24. Rocky Reach, Units 1-7 Design Solutions – Airgap Stability & Shape • Rim shrunk for full, off-cam runaway speed • Oblique elements used on spider and frame • Double dovetail design used for precise setting of stator keybars • Rotor poles individually shimmed to high circularity tolerance

25. Rocky Reach, Units 1-7 Design Solutions – Noise & Outage Time • Frame & stator core stiffened with radial depth and higher core clamping pressure • Outage reduced by constructing both rotor and stator in erection bay • Last (fourth) unit had only 45 days between commercial service of existing and refurbished units • All guaranteed performance requirements were met

26. Generator Case Studies Crystal Power Plant, Unit 1 • Customer – US Bureau of Reclamation, Colorado • Existing unit - 28 MVA, 11.0 kV, 257 rpm, 1.0 pf • Realize uprate potential • Increase reactive capability for black-start, line charging • Generator and turbine refurbishment for reduced maintenance costs • New rating – 35 MVA, 0.9 pf

27. Crystal Power Plant, Unit 1 Design Requirement • Contract requirement for 80 K field-temperature rise • Existing unit had 75 K limit, which it could not meet • 25% increase in MVA • Power factor change from unity to 0.9 over excited • 12.5% increase in MW

28. Crystal Power Plant, Unit 1 Interface Requirements / Design Space Restrictions • Existing soleplates • Housing diameter • Rotor outer diameter and axial length • Upper bracket and deck plates

29. Crystal Power Plant, Unit 1 Design Solutions – Field Temperature-Rise Limit • Do all possible to reduce excitation requirements • Re-insulate field with Class F material • Increase series turns by 20% - tooth x-section reduction more than compensated • Increase radial depth of stator core • Reduce airgap length • Performance testing last year measured a field- temperature rise of 78 K

30. Turbine

31. Turbine methodology Tender stage • Simplified analysis of main components (Spiral case, stay vanes, distributor, runner and draft tube); • Geometrical comparison between existing design and manufacturing references; • Hydraulic transient calculation; • Cavitation studies; • Search solutions for specifics problems (frequent mechanical failures, silt abrasion, operational instability and others) • Define the future turbine performance (guarantees) Short term analysis (Basic studies with simple tools)

32. Turbine methodology Design stage • Measurement of existing performance • Deeply inspection of all components of machine • Fluid Dynamic analysis of the static components (Spiral Case, Stay Vane, Distributor and Draft tube) • Design of some new profiles to improve the flow behavior (stay vane, wicket gates and draft tube) • Comparison of existing and new design (CFD) • Development of new runner (genetic algorithm) • Model test to validate the results Deeply analysis and experience of specialist to reach targets

33. Turbine methodology Stay vane and Wicket Gate Optimization CFD remain the main tool for analysis

34. Turbine methodology Draft tube study Stream Line analysis Existing Modified Flow velocity in a sectional elevation view of the existing draft tube elbow. When technically available modification in Draft tube provide good results

35. Turbine methodology Runner development “Classical” runner “Final” runner Blade profile is developed using an evolutionary algoritm and the experience of a hydraulic engineer Good Accuracy between CFD calculation and model test

36. St-Lawrence Rehab Project • St-Lawrence Power Project • 32 propeller units (16 NYPA and 16 OPG) • Two turbine designs : • BLH : 8 runners Ø5.8m (229 in.) 77.5 85 kHp(63.4MW) • AC : 8 runners Ø6.1m (240 in.) 79 kHp • Targets: • - Increase overall efficiency • - Translation of the peak efficiency to higher load • - Reduction of erosion by cavitation • - Increase of the stability of the turbine Ambitious targets

37. St-Lawrence Rehab Project • Main modification  New Runner • Development using the Alstom methodology • Twisted blade shape Runner developed to reach targets and solve the old design problems

38. St-Lawrence Rehab Project Sigma break curve at full load up to the maximal flow allowed by contract near the rated net head for the refurbishment of ST. LAWRENCE Power Plant.

39. St-Lawrence Rehab Project • Acceptance model test : cavitation New runner Old runner New & Existing runner for St. LAWRENCE power plant at the rated net head, full load and plant sigma value (model runner manufactured by ASTRÖ).

40. St-Lawrence Rehab Project Accurate manufacturing the reach the results

41. St-Lawrence Rehab Project New rated output : 63.4 MW Cavitation behavior improved Better stability Best efficiency in the higher load After commissioning confirmation of targets

42. Conclusion • Refurbishment is required to extend life of aging equipments and increase the value of equipment to the owner in terms of performance (higher output and efficiency, greater availability) • Presented Alstom case studies demonstrate the methodology success • Integration between Generator and Turbine is essential for good results in refurbishment projects • Alstom methodology has been efficient for projects in all the corners of the world