Monitoring of generator condition and some limitations thereof

Historically turbine-generator condition was monitored by rather primitive instrumentation, e.g., ammeters, voltmeters, temperature sensors. More advanced instrumentation devices have been added in the last 25+ years, e.g., partial discharge, turn-short flux probe, core monitors. But there still remains little or no detection capability for some of the major deterioration mechanisms, e.g., bar vibration without partial discharge, stator bar clip liquid leaks, series/phase joint copper cracking, developing field turn cracks, field insulation abrasion/cracks, retaining ring corrosion and cracks, field forging cracks. This paper will discuss root causes and progression rates of some generator deterioration mechanisms. The resulting negative impact on generator reliability of extending the periods between outage inspections can be high. Advantages of remaining with the historic 5-year period between outages will be illustrated.