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May 11, 2006 Hydropower Refurbishment – Alstom’s Methodology and Case Studies Presented By Naresh Patel ( Electrical) Sreenivas.V ( Mechanical)

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Presentation on theme: "May 11, 2006 Hydropower Refurbishment – Alstom’s Methodology and Case Studies Presented By Naresh Patel ( Electrical) Sreenivas.V ( Mechanical)"— Presentation transcript:

1 May 11, 2006 Hydropower Refurbishment – Alstom’s Methodology and Case Studies Presented By Naresh Patel ( Electrical) Sreenivas.V ( Mechanical)

2 - 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 - 3 - 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 The Need for Refurbishment

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

5 - 5 - 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 The Need for Refurbishment

6 - 6 - 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 The Need for Refurbishment


8 - 8 - 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 Refurbishment Methodology

9 - 9 - 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 Refurbishment Methodology

10 - 10 - 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 Generator Specific Methodology

11 - 11 - 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 Generator Specific Methodology

12 - 12 - 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 Generator Specific Methodology

13 - 13 - 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 Modeling of the Refurbishment

14 - 14 - 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 Modeling of the Refurbishment

15 - 15 - Allatoona Stator Core ~ 45 Years Old

16 - 16 - 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 Modeling of the Refurbishment


18 - 18 - 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 Modeling of the Refurbishment

19 - 19 - 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 Modeling of the Refurbishment

20 - 20 - 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 Modeling of the Refurbishment

21 - 21 - 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 Generator Case Studies

22 - 22 - 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 Rocky Reach, Units 1-7

23 - 23 - 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% Rocky Reach, Units 1-7

24 - 24 - 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 Rocky Reach, Units 1-7

25 - 25 - 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 Rocky Reach, Units 1-7

26 - 26 - 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 Generator Case Studies

27 - 27 - 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 Crystal Power Plant, Unit 1

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

29 - 29 - 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 Crystal Power Plant, Unit 1

30 - 30 - Turbine

31 - 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 - 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 - 33 - Turbine methodology CFD remain the main tool for analysis Stay vane and Wicket Gate Optimization

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

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

36 - 36 - St-Lawrence Rehab Project St-Lawrence Power Project –32 propeller units (16 NYPA and 16 OPG) Ambitious targets 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

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

38 - 38 - ST. LAWRENCE 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. St-Lawrence Rehab Project

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

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

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

42 - 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

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