Impact of Lightning Impulse on Electric Field Stress of Spacer in Single Phase Gas Insulated Busduct

During the last two decades, for reliable power supply, GIS have found a broad range of application in power systems because of their high reliability, easy maintenance, small space requirement, etc. Gas insulated sub-stations employs a superior dielectric gas, SF6 at moderate pressure for phase to phase and phase to ground insulation. Several troubles and system outages in GIS have been reported world-wide due to insulation failures which resulted in the intensification of electric field along the spacer surface and especially at the triple point electrode – spacer – gas. Hence, it was required to reduce the rate of insulation failure. In this work, Conventional cone type spacer geometry is taken for which field study has been done. Electric field stresses developed by the cone type spacer on the surface of the spacer and also at the triple junction is determined. It is found that the electric field stress at the surface of the spacer is maintained uniform, the electric field stress at the critical junctions formed by the conductor, solid insulator and SF6 gas is not maintained at minimum value. Metal inserts are considered as a means to reduce the stress at the triple point junction. The impact of Lightning Impulse on the Electric Field Stress along the spacer is carried and the reduction of stress is mitigated with the insertion of Metal Inserts.