DC Surface Flashover of Epoxy Resin/γ-Al2O3 Nanocomposites for Current Lead Insulation

The current lead insulation of the high temperature superconducting DC current limiter is in the terrible working environment of strong electric field and temperature gradient field from room temperature to liquid nitrogen (LN2) temperature. Bisphenol F epoxy resin, as a common terminal insulation material, is prone to surface flashover during equipment operation, which leads to premature failure of insulation. In order to improve the reliability of the terminal insulation system, epoxy resin/γ-Al2O3 nanocomposites were prepared. The dielectric constant, DC conductivity, trap distribution, partial discharge characteristics and DC surface flashover voltage of the nanocomposites at room temperature and in LN2 were measured and analyzed. The results show that with the increase of γ-Al2O3 nanoparticles content, the DC surface flashover voltage of the nanocomposites first increases and then decreases, and the partial discharge inception voltage generally increases. Appropriate γ-Al2O3 nanoparticles doping can effectively inhibit the generation and development of surface discharge.