Two EPRI reports from 2004 and 2006 still offer generator-maintenance lessons: one surveyed 118 generators; the other found online partial-discharge and electromagnetic-interference tests useful for screening, but not a replacement for physical inspections.
The 2004 rotor report sets out 47 best practices and 27 lessons from its survey. It flags retaining rings, field windings and rotor forgings as recurring trouble spots; for retaining-ring flaws, it says ultrasound is not always reliable and recommends liquid-penetrant and eddy-current tests, plus material sampling. It also links generator cycling with main-lead, insulation and connector damage, and reports shorter rotor-life expectancy in units with higher reactive-power loads.
The 2006 monitoring study compared online partial-discharge and electromagnetic-interference results with inspections during major outages. Most testers’ assessments were rated “substantially correct,” while some were only “partially correct,” especially for lower-frequency PD. EPRI says monitoring can track trends and prioritize attention, but external sources, nonstandard measurement units and noninterchangeable vendor equipment complicate readings and leave interpretation dependent on specialists.
