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May 11, 2006
Subtitle (Arial 22)
Hydropower Refurbishment Alstoms Methodology
and Case Studies
Presented By Naresh Patel ( Electrical) Sreenivas.
V ( Mechanical)
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Introduction

• Alstom Power Hydro Products
• Descended from Neyrpic, ASEA, BBC, Alsthom
• Over 100 years experience in hydro industry
• Engg Mfgg in Americas, Europe Asia
• Presence in Asia Includes
• Turbine, Generator, Hydro Mech, PS, BoP
• Design Mfgg in Tianjin, China
• Design Mfgg in Vadodara, India

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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

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

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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

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GENERATOR LIFE CYCLE
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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

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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

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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

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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

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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

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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

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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

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Allatoona Stator Core 45 Years Old
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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

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STATOR-STEEL QUALITY
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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

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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 gt15 uprate

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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

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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, gt 95 dB
• Life extension / increased availability
• Scope new stators rotors - everything except
  shaft, brackets bearings

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Rocky Reach, Units 1-7

• Design Requirements
• High efficiency main design driver
• US55k / kW evaluation, US70k / kW penalty
• Airgap shape tolerances one half of IEC/CEA
  standard
• Low audible noise, lt80 dB 1 m from housing
• High evaluation for short outage

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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

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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

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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

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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

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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

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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

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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

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Turbine
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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)
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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
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Turbine methodology

• Stay vane and Wicket Gate Optimization

CFD remain the main tool for analysis
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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
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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
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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
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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
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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.
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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).
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St-Lawrence Rehab Project
Accurate manufacturing the reach the results
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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
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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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