Electric Field and Sheilding Effect Analysis of 1100kV DC SF6 Gas Insulated Wall Bushing

UHVDC wall bushing is a key equipment which connects valve hall and DC yard, and it loads total voltage and current. In this paper, concerning the charge relaxation process and weakly ionized gas conductivity model (based on natural ionization, ion migration and diffusion motion), the electric field simulation model of wall bushing was established, the shielding effect regulated by single/double layer shield structure (SLSS/DLSS) were studied. The result indicated that: The DLSS, compared to SLSS, can significantly reduce the field strength on both sides of the insulator and surface of the internal electrode. The electric field distribution on the air side of the insulator under DC voltage is not affected by the different configuration (SLSS or DLSS) of the inner shield electrode, but the DLSS can still reduce the surface of the inner electrode of the casing relative to the SLSS. This work is aim to report the regulating effect on field distribution by DLSS under different voltages in details, which can provide a basic reference for insulating structure design of 1100kV UHVDC SF6 gas-insulated wall bushing.