Behavior of Metallic Particles in a Single Phase Gas Insulated System with Dielectric Coated Electrodes

Abstract

The development of compressed gas insulated switchgear (GIS) equipment has progressed rapidly. Conducting particles in transmission and switching equipment insulated by compressed sulphur hexafluoride (SF6) can result in loss of as much as 90% of the gas dielectric strength. These particles may be free to move in the electric field or may be fixed on the conductors, thus enhancing local surface fields. In a horizontal coaxial system with particles resting on the inside surface of the enclosure, the motion of such particles is random but the randomness depends on the coefficient of restitution and angle of incidence when approaching the coaxial conductors. The power industry has utilized several methods to control and minimize the effect of particle contamination in GIS. One such technique is to apply a dielectric (high resistivity) coating to the inside surface of the outer GIS enclosure. The electric field necessary to lift a particle resting on the inside surface of a GIS enclosure is much increased due to the coating. The simulation of the particle movement was carried under different AC voltage levels for coated and uncoated cases. The results have been presented and analyzed.