Role of nano-filler on partial discharge resistance and dielectric breakdown strength of micro-Al2O3 / epoxy composites

Epoxy resin often suffers lower dielectric breakdown strength if micro-fillers are loaded. It might be possible to raise the once lowered breakdown strength, if nano-fillers are added. In this paper, such performances were investigated on model specimens consisting of alumina (Al₂O₃). First of all, PD (partial discharge) behavior on the surfaces of samples was clarified in the insulation system consisting of a flat copper electrode attached on an epoxy substrate. Then, on the basis of finding, the breakdown strengths were investigated by using a sphere to sphere electrode structure with a flat sample inserted. Several materials consist of neat epoxy, 5 %wt nano-Al₂O₃/ epoxy composite, 60 %wt micro-Al₂O₃/ epoxy composite and 2 %wt nano- 60 % wt micro-Al₂O₃/ epoxy composite. It was found that nano-micro- Al₂O₃/ epoxy composite is higher in both dielectric strength and PD resistance than micro-Al₂O₃/ epoxy composite.