Surface Charge Accumulation on Epoxy Insulator with Complex Surface Profile under DC Voltage in SF6/N2 Mixture

Epoxy insulator has been widely employed in Gas Insulated transmission Line (GIL) and Gas Insulated Switchgear (GIS). Surface charge accumulation on the insulator has been considered as a key point that affects the flashover voltage. In this paper, the surface charge accumulation behavior on real-sized insulator with a complex surface profile in 0.4 MPa SF6/N-2 mixture has been studied. The insulator as well as the electrode system was installed inside a sealed test chamber and DC stress of -10, -20, -30 kV was applied between the electrodes so as to charge the insulator. The accumulation mechanism has been demonstrated based on numerical simulation. The results showed that the surface charge was mainly negative in SF6/N-2 mixture. The charge speckles were mainly accumulated in the nonplanar region of insulator. The main reason for this phenomenon is the competition among bulk conduction, gas conduction and surface conduction.