Reduction of Electric Field Stress on the Surface Contour and at the Triple Junction in UHVAC GIS by Spacer Design Optimization

Abstract

Abstract The conical spacers made of epoxy resin are widely used in Gas Insulated System(GIS) for electrical insulation as well as mechanical support to the conductor. Electric stress on the surface of the spacer as well as at the triple junction is of major concern while designing the spacer for the Ultra High Voltage Alternating Current (UHVAC) GIS. To reduce the possibility of the flashover, the tangential field at the concave and convex surfaces is to be within limits. This paper presents a stepwise method for the reduction of the electric field at the spacer surface and at the triple junction by geometry shape optimization. The electric field has been calculated by solving Laplacian equation by Finite Element Method(FEM). Optimization has been realized by incorporating Nelder-Mead(NM) algorithm with FEM solution. The tangential field at the concave and convex surface of the conical spacer has been optimized by changing the shielding ball shape and metal inert in the spacer as well as by changing the curvature and thickness of spacer near to the high voltage conductor. The results demonstrate the reduction in the principle stress for the optimized geometry shape and the stress at the triple junction. The improvement in the electric field uniformity for the spacer surface is seen in the final optimized geometry