Turbine/Generator Upgrades and Maintenance

1. Turbine/Generator Upgrades and Maintenance

2. Topics • Turbine Blading & Steam Path Upgrades • Turbine Stop / Control Valve Upgrades • Turbine Control System Modernization • Generator Improvements

3. Steam Path Improvements • More than 20 units in plan for upgrade • Efficiency gain • Aerodynamic blade profiles • Improved inter-stage sealing • Reduction of sidewall secondary flow losses • Reduction in future O&M costs • Extend time between overhauls • Reduction of solid particle erosion damage • Less coal burned

4. Glen Lyn 6 Series 235MW (GE) HP/IP • Nine (9) Units (Subcritical, 1957 - 1961) • Integral control valve chest girth weld creep • Purchased complete spare in 1990 • Exchanged on other 8 units (1991 – 2004) • New rotors – replaced “C” grade materials • New nozzles, diaphragms (Rows 1,9,10,12) • Reassemble non-outage; 4-week reduction • Cost = $8 Million (US) first unit installed, approx. • Cost = $4 Million (US) subsequent units, approx.

6. Glen Lyn 6 Series 235MW (GE) HP/IP • Results • Restored CV chest with improved girth weld • Improved HP efficiency by 1.5% - 2.0% • 2.5 MW and 35.28 kcal/kWh (140 Btu/kWh) gain • Erosion minimized, reduced repairs • Extended inspection intervals to 10-11 years • Re-inspections begun in 2001 confirm benefit

7. 1300 MW Series (Alstom) HP • Six (6) Units (Supercritical, 1973 – 1989) • Use of spare rotor/inner casing assembly • Replaced all stationary/rotating rows (28) • Reuse rotor and re-round inner casing • Modified seal strips for steam swirl stability • Cost = $6 Million (US) per unit installed, approx. • Results • Blading Efficiency > 92.0%, increase of 4.7% • 20 MW and 28.5 kcal/kWh (113Btu/kWh) • Improved rotor stability against steam swirl • 3 Units completed - - 1 with premature degradation

8. 600,800 MW Series (GE) HP/IP • Eight (8) Units (Supercritical, 1967 – 1972) • To date, four have been converted • New nozzles, diaphragms, seals • Reblade spare rotor; reuse shells • Cost = $6.5 Million (US) per unit installed, approx. • Results • 82.8% - 86.3% HP section efficiency • 11MW gained on 800MW Series • 600 MW Series HP fell short of expectations by up to 3.5% due to overstated recoverable losses by OEM.

9. Effect of Advanced Design Steam Path

10. Big Sandy Unit 1 HP-IP/SFLP • One (1) unit, W design (Subcritical, 1963) • HP turbine complete and IP/SFLP turbine rotor and inner casing – install 2008 • Inefficient original design • Internal components subjected to erosion and distortion • Creep damage evident • No spare blade rings or rotors

11. Original Design Issues Efficiency Turn-around (Pressure Loss) Curtis Stage (Poor Efficiency) Conventional Cylindrical Airfoil (Poor Efficiency)

12. Existing Maintenance Issues Large Dia. Inner Casing (CrMo casting) (Distortion, Rubbing) Reliability L-0 Shrunk-on Disc (SCC Potential) Stage 1 Blade Root Distortion Stages 2-4 Blade Untwist IP/SFLP Rotor 44 years Old L-0 Blade Fatigue Life (Blade Failure) Large Blade Ring (Distortion, Rubbing, Blade Leaning)

13. New HP Section Design ACC Packing (Active Clearance Control) Separately supported blade rings and balancing ring Integral Inner Casing Monoblock No Bore Rotor 3-D Reaction Blades (ISB) Rateau control stage

14. New IP/LP Section Design ACC Packing (Active Clearance Control) Separately-Supported Blade Rings 25in ISB Mono block no bore rotor No Shrink-fit 3-D Reaction Blades (ISB) Integral Inner Casing

15. Big Sandy Unit 1 Expectations • Anticipated Results • Improved reliability and design efficiency • HP efficiency +4.1% to 88.9% • IP efficiency +3.1% to 94.6% • Expect +18 MW at original design steam flow • Includes replacement throttle/governor valves • Installed cost $18Million (US), approx.

16. LP Turbine Performance Retrofits • AEP experience driven by reliability issues • Stress Corrosion Cracking on blades, disks and Low Cycle Fatigue on blade attachments • Flow limit for L-1 rotating blade causes curtailment • LP turbine exhaust limit = 140 mm HgA (5.5 in HgA) • Frequently caused summer time curtailments Solution = LP Turbine Upgrade

17. LP Turbine Performance Retrofits • Four (4) BB73 W LP steam paths “ruggedized” • Improved material properties to resist SCC and LCF • Aerodynamic improvements to blades and inlet / exhaust flow guides • Improved seal design to reduce leakage • Full load capable to 203 mm HgA (8 in HgA) backpressure • Improved performance: 3.4MW, 22.4 kcal/kWh (89 Btu/kWh)

18. Stop/Control Valve Upgrades • Material Damage • Thermal fatigue, creep • Reliability • Tight shutoff, leaks • Maintenance • Weld repair to valve body, seats, bolt holes • Design Improvement • Improve O&M • Reduce pressure drop

19. 1300 MW Series SV/CV Upgrades • Original Design • Pressure drop across combined valves = 5.1% • Limited steam flow at VWO + 5% overpressure • Significant solid particle erosion damage • Expensive repairs performed every 2-3 years

22. 1300 MW Series SV/CV Upgrades • New Design • Separate stop and control valve chambers • Actual pressure drop across valves = 2.08% • Achieved 32 MW increased generation capability without changing boiler conditions • Updating valve actuators to digital controls

23. Turbine Control System Upgrades • Converting original MH and analog EH controls to digital • Integrated into plant Distributed Control System • Reuse or modify hydraulic systems • Use fire resistant fluids • Expectations • Enhanced control • Fewer unit trips • Faster startup/ramp rates • Online testing of turbine valves and protective devices

24. Turbine Control System Upgrades • Results • Smooth, rapid rollups to synchronous speed • CV position and load ramping optimized by stress probe • CV stroke ramped according to test throttle pressure • Improved reliability during protective device checks • Lower peak speeds reached during turbine trip • Reduction in boiler tube leaks due to “soft” trips All contribute to improved reliability and performance

25. Generator Improvements • Inspection Intervals (typical) • Field in-place ( 5 years) • Field removed (10 years) • Perform routine cleaning, testing, repairs • Goal: Achieve high reliability through design life of insulation systems

26. Generator Rewinds • Rewinds Offer Opportunity for Improvement • Required for reliability and maintenance purposes • Efficiency improvements are small added benefit • Stator Windings • Asphalt stator bar insulation replaced with modern epoxy-mica insulation • Potential for increased copper cross-section in original slots • Improved cooling gas or water flows reduce operating temperature and extend design life • Stator Cores • Inspect and test for looseness, hot spots, resonance • Several cores replaced (full, partial) • Reference papers available in Breakout Session

27. Generator Rewinds • Fields • Replace retaining rings with 18Mn 18Cr material • Improve end turn blocking design and materials • Restore/replace copper and replace all insulation • Optimize cooling gas flow

28. Summary • AEP has been retrofitting turbine generator equipment with efficiency improvements for more than 15 years. • Experience with OEM and non-OEM solutions. • Economic benefit drives the HP and IP turbine retrofits. • Must consider design improvement vs. restoration improvement. • Turbine valve design could provide upgrade potential. • Turbine control integration can produce thermal benefits. • Reliability benefit drives the LP turbine and generator retrofits (typically). Some small efficiency improvements are possible.

29. Breakout Session • Two Sessions on Tuesday Afternoon • Expert Attendees • Steve Molick – Turbine Services Manager • Jim Michalec – Staff Engineer, Generators • Alex Manukian – Sr. Engineer, Turbines • Jim Cable – Sr. Engineer, Turbines, Controls • Dan Sculley – TG&PSE Manager

30. Questions