Effects of High Magnetic Field on Partial Discharge and Flashover Behavior of Epoxy Resin

High-field magnets use epoxy resin as the insulation for superconducting coil terminals. Surface flashover on the interface between the gas and solid insulation will cause insulation failure. In this paper, effects of high magnetic field on surface partial discharge and surface flashover of the epoxy resin are investigated. Experimental results show that high magnetic field causes the decrease of relative permittivity and further changes the electric field distribution along the surface of epoxy resin. Surface partial discharge behavior is directed by both the decrease of surface electric field at the interface and the decrease of breakdown voltage of air gap in high magnetic field. Lorentz force begins to play a role during the extension of electron avalanche by changing the migration of charge carriers and weakening the equivalent effect of the normal electric field near the triple junction. Opposite trends are observed with the increase of magnetic flux density when the direction of Lorentz force is parallel or perpendicular to the surface of epoxy resin.