About the breakdown and partial discharge behavior of different heat-resistant cast resins

Experimental investigations concerning the breakdown and the partial discharge behavior of six heat-resistant cast resin systems are presented and discussed. The tests were performed with two epoxy resin and an epoxy modified isocyanate system in combination with two different fillers. The breakdown strength of the materials was measured in both a uniform and a non-uniform electrical field. Furthermore the partial discharge inception voltage (PDIV) was determined by using a highly inhomogeneous electrode arrangement. All tests were performed in dependence on the temperature. The results show that wollastonite as filler can lead to a lower electrical strength of the molding material than silica flour. Furthermore, above the glass transition temperature (T_g), the electrical strength diminishes significantly and resin systems with a high T_g can have nearly constant electrical properties over a large temperature range