Using diagnostic technology for identifying generator winding maintenance needs

Abstract

Detecting deterioration in generator winding insulation can help hydro O M staff plan needed maintenance. One approach is analyzing the partial discharge (small electrical sparks) activity in the insulation; the more of this activity, the closer the winding is to failure. Instruments are available for measuring partial discharge during normal generator operation. Ontario Hydro is saving millions of dollars in avoided rewinds using this approach. By performing stator winding maintenance on an as-required but planned basis-based on data from partial discharge analysis (PDA)-Ontario Hydro has experienced a net savings of $4.2 million per year in rewind costs. (This savings is based on 150 hydraulic generators where the average rating is 40 MW). The savings are achieved through timely preventive maintenance practices such as rewedging and repair to extend the life of a generator and avoid premature rewinding. Ontario Hydro also has reduced its number of outages owing to confidence that maintenance personnel have in PDA analysis of the generator winding condition.