Electrical Treeing Characteristic Influenced by Particle Size of Silica Filler in the Epoxy Resin

Abstract

Polymeric insulating materials such as epoxy resin are commonly used to electric power equipment. And additives and fillers are traditionally used to improve the mechanical, thermal properties, and sometimes electrical properties. To understand electric treeing properties, the time to breakdown is measured using a CCD camera. The average tree propagation speed in the sample with silica filler of 80 µm in size decreased with the increase of the filler occupancy ratio. On the other hand, the average tree propagation speed in the sample with silica filler of 48 µm in size increased with the increase of the filler occupancy ratio. It was considered that the increase in the effective length between electrodes and the field relaxation of tree tip were caused by the bigger filler size in the sample with silica filler of 80 µm in size. In the case of the sample with silica filler of 48 µm in size, it was considered that the tree propagation effect at the interface between the filler and epoxy which brought to faster tree propagation speed became dominant.