Surface flashover mechanism and its application to diagnosis in vacuum interrupter

The application of vacuum interrupters and vacuum circuit breakers for higher voltage level is strongly expected. In electrical insulation in vacuum, surface flashover on solid insulator is one of the main problems for the higher voltage vacuum interrupters. In this paper, through the review of our recent researches, we discuss on the initiation and development mechanisms of flashover in the configuration with electric field distribution almost perpendicular to the dielectrics surface. Usually, the flashover was begun by exclusive electron emission at the cathode; however, the large charging on the dielectric surface before the flashover allowed the flashover initiated by secondary electron emission avalanche to occur. The development characteristics of surface flashover agreed with the electron-stimulated outgassing mechanism. The flashover development characteristics were applied to the discharge diagnosis in vacuum, and the effectiveness of our proposed discharge discrimination method was verified.