Research on Temperature Characteristics of DC Surface Flashover in Vacuum

Polymer is an excellent electrical insulating material with well corona-resistance, such as polyimide. It has been widely applied in power system insulation, aerospace industry, marine electrical equipment and microelectronics. In this paper, DC surface flashover experiments under different temperature of polyimide are studied in vacuum to reveal the surface flashover mechanism in order to enhance the reliability of polymer in complex engineering environments. It is found that the DC surface flashover voltage firstly decreased then increased and finally decreased again with the increasing of temperature in the range of 193~353K. The flashover voltage reached the maximum at 313K and minimum at 273K, respectively. The experiment also found that flashover voltages are significantly enhanced in high temperature region (313~373 K) compared that in lower temperature region (193~273 K). The experiments indicate that the thermal electron emission near the cathode, the charge transportation of dielectric insulators and thermal activation degassing are three important factors for polymer surface flashover voltage as the temperature increased, and the thermal activation degassing which is the most critical factor affecting the surface flashover characteristics in vacuum.