Significance of defects found during high direct-voltage ramp tests

Abstract

High direct-voltage ramp tests, according to IEEE Std 95, are used to evaluate the condition of groundwall insulation in rotating machine windings. Evidence of possible defects has been found involving asphalt, polyester and epoxy bonded insulation systems. Some results reflect lack of cure or environmental conditions while other results are indicative of serious groundwall defects which may fail while the machine is in service. Action taken on the basis of the test results is discussed.