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 (Al
2
O
3
). 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-Al
2
O
3
/ epoxy composite, 60%wt micro-Al
2
O
3
/ epoxy composite and 2%wt nano- 60% wt micro-Al
2
O
3
/ epoxy composite. It was found that nano-micro- Al
2
O
3
/ epoxy composite is higher in both dielectric strength and PD resistance than micro-Al
2
O
3
/ epoxy composite.