Research Progress on Vacuum Surface Flashover of Solid Dielectrics

The issue of surface flashover limiting the electrical strength of composite insulating system in vacuum has received many attentions. This paper reviews the research progress of surface flashover in the recent years. Research results indicate that surface flashover performance of solid dielectrics in vacuum is influenced by many factors, such as the way of conditioning, surface and bulk properties of materials, the deposited charges in surface layer, electric field distribution of insulating system, etc. Mechanism implies that the essence of surface flashover is the charge transport behavior across gas-solid interface under high electric field, which involves charge trapping and de-trapping properties in dielectric surface layer, secondary electron emission properties, impact ionization of gas molecules and electron multiplication properties in gaseous phase (or desorbed gas). The development process and formation of surface flashover is a coupling effect of the above factors. Based on the above analysis, it is concluded that the improvement of surface flashover voltages can be achieved by changing the surface and bulk properties of materials as well as improving the electric field distribution of the whole insulation system.