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May 11, 2006
Subtitle (Arial 22)
Hydropower Refurbishment –
Alstom’s Methodology and Case Studies
Presented By
Naresh Patel ( Electrical)
Sreenivas.V ( Mechanical)
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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 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. Short term analysis (Basic studies with simple tools)
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. Deeply analysis and experience of specialist to reach targets
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. CFD remain the main tool for analysis
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. Good Accuracy between CFD calculation and model test
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