Application of Partial Discharge Testing to Hydro Generator Maintenance

An improved partial discharge test to ascertain hydraulic generator winding condition, has been in use for the last 7 years. The test, which can be done by generating station staff without disrupting operation, has been applied to about 140 machines in eight North American utilities. Partial discharge testing is one of the main reasons Ontario Hydro has an exceptionally low winding replacement/major repair rate. Examples of results culled from thousands of tests are presented.. The use of the partial discharge test for planning winding maintenanGe and gauging the effectiveness of repairs is discussed.