siemens - Public Service Commission

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Time for cleaning, painting
Belly cover installation
Fresh crew for reassembly
Ops must own ventilation test
Obtain MSDS and chemical list early
Replace bushings and CTs
Tom Schubert - Manager Global Generator Service Engineering
Industry Trends and fleet demographics
Global Overall Electrical yearly output 9% Increase over 5 years
Average US base load is currently 32 years in service
This base 20-40 years in service equates to approximately 80% of total base load
30-40 years is approximately 45% of US base load
Typical Life Cycle for large frame generators is 30-40 years
Alex Christodoulo - Manager Generator Services Engineering
Modernizing and Servicing generator stators
Overview of Water and Hydrogen cooled stator
Recommended maintenance to extend life cycle an additional 30 years
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Stator Windings - End connection strand cracking, End winding loosening, parallel ring
looseness, and phase lead cracks. These are caused by thermal stresses and age
degradation, mechanical forces caused by electromagnetic forces in natural fiequency
ranges. Transient damage caused by severe fault etectro-mechanical stresses. These
mechanisms can today be controlled by the advancement of material composition and
design modeling. Generator is designed to withstand a 3 phase short.
Stator Core - Only 5 Major core losses over last 50 years, foreign object 5, Over fluxing
5, Looseness 3, Installation 1, Unknown 1.
Recommended Maintenance
El-cid < 1 OOmilliamp - look for hot spots with thermo vision inspection
Shorted laminations - grind out make field repairs or terminate
Core Looseness and Length - through bolts may bottom out need to add more iron plates
Core End Iron heating - new designs are more adequately cooled
End Shield laminations - end shield replacement
3 Options
Onsite Stator rewind and corc refurbishment
Onsite Stator rewind and core replacement with donut stacking replacement
Onsite replacement with seed or new components
PEF-NCR-00788