Multi-factor evaluation and end grading systems for high voltage stator windings

End-grading systems used to reduce the sharp voltage gradient on the surface of stator insulation as it emerges from the end of the core slot are subject to damage from thermal, electrical, and mechanical stresses during service operation. Suggested laboratory methods for evaluating and forecasting the long-term service performance of different end-grading systems have been generally inadequate and unreliable. The successful applicant of a two-factor accelerated test procedure is described, and plans for a three-factor procedure, now being implemented, are presented