Lightning Impulse Breakdown Characteristics in Epoxy Resin Filled with Precipitated ZnO Varistor Granules

Insulators of the spacer have been studied to relax the electric field in order to downsize gas insulated switchgears (GISs). We have been researching to make electric field relaxation of solid insulation material by filling with ZnO varistor granules. In our previous study, when we applied positive lightning impulse voltage to epoxy resin filled with precipitated ZnO varistor granules, distortion happened in voltage waveforms before breakdown. In this study, we investigated the breakdown and resistance characteristics of epoxy resin filled with precipitated ZnO varistor granules when the dent part of voltage occurred. As the result, both distortion voltage and breakdown voltage were almost proportional to the gap length. Furthermore, it can be seen that the calculated resistance gradually decreases as the applied voltage increases at each gap length.