Metallic particle dynamics in a single phase gas insulated busduct with coated electrodes under lightning impulse superimposed on power frequency voltage

摘要

Conducting particles in transmission and switching equipment insulated by compressed sulphur hexafluoride (SF_6) 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. 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 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. Transient over voltages due to lightning and switching surges cause steep build-up of voltage on transmission lines and other electrical apparatus, therefore it is necessary for the GIS also to withstand such voltages without breakdown of insulation. Lightning impulse voltage of 1050 kV is superimposed on power frequency voltages of 75 kV, 100 kV, 132 kV and 145 kV are applied to 1-Phase Gas Insulated Bus (1-Phase GIB) and the maximum movement of aluminum, copper, and silver particles is determined. The movement patterns are also determined with and without Monte-Carlo simulation for movement of particle in axial and radial directions. The results are presented and analyzed.