Research progress on surface flashover phenomena across solid insulation in vacuum

The electric strength of composite insulation system is always determined by the surface flashover phenomena of its insulating materials, which greatly limits the overall performance of many electrical and electronic systems. The state-of-the-art of flashover across solid insulation in vacuum is reviewed. It is considered as a kind of complex interface (the boundary of electrode and material) and surface (the surface of material) physical phenomena occurred under high electric field. Essentially flashover process reveals the charge behaviors under high field, consisting of two processes, i.e., the bulk (inside surface layer of a material) and outside (on and above surface of a material) processes. It is needed to synthetically consider the influential factors such as relative permittivity, electric resistivity, secondary electron emission behavior and surface trap distribution of insulation, henceforth to propose the general evaluation system for characterizing and mending flashover characteristics, and to ultimately understand new physical phenomena and efficiently control them.