Applications of insulation resistance and high direct voltage ramp tests to the assessment of insulation systems of hydrogenerator stator bars and coils

Abstract

The paper discusses the application of the insulation resistance and polarization index and the high direct voltage ramp tests to the assessment of the integrity of insulation of hydrogenerator stator bars and coils. In the paper, examples of continuously recorded insulation resistance and current measured during the high direct voltage ramp tests are presented for epoxy-mica insulated stator bars of hydrogenerators. The paper defines also new parameters for the interpretation and comparison of various test data obtained from the insulation resistance and the high direct voltage ramp tests