Flashover Characteristics Along the Epoxy Resin Insulator under DC Voltage in SF6 Gas

In order to promote the flexibility about the selection of transmission corridor, DC gas insulated transmission line (GIL) can be utilized to substitute part of the overhead line or cable in special environment. Key factors that greatly threaten the insulation level of GIL are surface charge accumulation along the insulator surface and electric field distortion under DC voltage. In this paper, the cone-plane electrode assembly has been established to simulate the electric field distribution of the coaxial cylindrical configuration in GIL. Key factors that affect the insulator´s flashover characteristics in SF6 gas under DC voltage are investigated mainly from the view of the filler and geometry of epoxy resin insulators. Results show that among epoxy resin insulators with no filler, alumina and silica, surface dielectric strength of silica filled insulators is the most excellent in both short-term flashover and long-term withstand voltage tests. Also, the attention points in optimizing cone-plane electrode assembly based epoxy resin insulator for DC GIL and the method to approximately acquire charging time constant of insulator have been put forward.