Discharge characteristics of composite insulation system with floating electrode and solid insulator in vacuum

For the development of vacuum interrupters for their higher voltage application in power transmission systems, it is necessary to clarify the discharge characteristics of composite insulation systems with a shield (floating electrode) and a solid insulator in vacuum. In this paper, we focus on the composite discharge patterns via the shield and the solid insulator. For cathode-shield-insulator-anode (c-s-i-a) and cathode-insulator-shield-anode (c-i-s-a) electrode configurations, the discharge can be classified into two independent processes: breakdown in vacuum gap and surface flashover on the solid insulator. Furthermore, we have found that the breakdown development time increases with the increase in the gap length and the surface flashover development time depends on the voltage peak after flashover inception, which are consistent with discharge development characteristics for individual gap breakdown and surface flashover, respectively. These results are significant to understanding and discriminating the composite discharge patterns and discharge path in vacuum interrupters.