Investigations of diagnostic tools for insulation systems of high voltage rotating machines

In this work the results of extensive investigations on the behaviour of a solid insulation system for rotating high voltage machines with thermal class F (155°C) will be reported, which was subjected to a thermal overstress (215°C) in repeated cycles. The test parameters should represent the thermal deteriorating effects of the insulation system in service on an accelerated basis, in order to evaluate the condition of the insulation system in a non-destructive manner. The results indicate how the changes in electrical and dielectric properties of insulation take place during the accelerated aging test.