Surface discharge resistance testing of dielectrics

In order to extract as much data as possible from corona resistance tests and to understand the material behavior, a test setup was built which allowed partial discharge data and videos to be acquired in parallel. A variety of polymer films were tested in different atmospheric conditions (humidity, closed or open configurations) with several ground electrode systems (varnish, sputter, etc.). Polymer films were coated with ceramic layers in order to increase the lifetime. It is shown that the partial discharges are modified by the material surface properties and the corona resistance test is hence not objective. However, the increased amount of experimental information allows a much better understanding of sample failure mechanisms than the recording of lifetime only. This is most important for the development of new materials