Modelling and Simulation of Trajectories of a Wire Like Particle in a Three Phase Common Enclosure Gas Insulated Busduct (GIB) with Image Charges

Abstract: In recent years, SF6 gas insulated switchgear (GIS) has become more widespread in electrical power substations and GIS rated from 66 to 1100kV are working successfully. The GIS is used in closed vessels, isolated from the atmosphere. This gives it intrinsically high insulation reliability because there is no contact with dirt or contaminates. To assure even better reliability, measures must be taken against metallic particle contamination. Some of these in use include changes in the manufacturing environment, modification of the structures, careful cleaning of the GIS both during and after assembling, etc. Even at most measures are taken to eliminate particle contamination effect metallic particle contamination in a compressed Gas Insulated Busduct (GIB) system Is inevitable and may substantially lower the corona onset and breakdown voltages of the system. The random movement of metallic particles in a GIB system plays a crucial role in determining the insulation performance of the system. In this study a statistical approach has been used to evaluate the probability of SF6 insulation breakdown due to the presence of contaminating metallic particles. Under 50-Hz AC voltage, the particle motion is complex, and under appropriate conditions, the particle may cross the gaseous gap from the lowfield region near the outer enclosure to the high-field region near the central conductor. For the commonly encountered size of metallic particles in practical Gas Insulated systems, such a crossing of the gaseous gap takes several cycles of the 50-Hz voltage. In order to determine the particle trajectories in a threephase common enclosure GIB) an outer enclosure of diameter 500 mm and inner conductors of diameters 64 mm spaced equilaterally are considered. Wire like particles of aluminum and copper has been considered to be present on enclosure surface of a three-phase bus duct. A method based on particle movement is proposed to determine the particle trajectory in GIS or GIB for a three phase common enclosure while the image charge effects of the conductors are considered. The motion of the wire particle was simulated using the charge acquired by the particles, the macroscopic field at the particle site, the drag coefficient, Reynold’s number and coefficient of restitution. The computation of particle movement has been carried out on bare electrode system for different voltages. The results have been presented and analyzed.