Performance Improvement of Insulators in a Gas-Insulated System

The solid-electrode-gas interface has a critical influence on the withstand voltage of the insulating gap. The geometrical shape of the insulator plays a major factor in the enhancement of the electric field and therefore determines the withstand voltage capability of the dielectric. A concave shaped insulator, suitable for GIS, has been examined theoretically to determine the best contact angle between the dielectric and the conductor to yield an improved withstand voltage. An experimental verification has been conducted by extensive measurements of the surface flashover in sulphur hexafluoride and in nitrogen. It is found that the withstand voltage capability can be increased by up to 20%, at high gas pressure, compared to a rectangular cylindrical insulator post.