Analysis of particle movements in a single phase gas insulated busduct with various operating conditions

Gas insulated sub-station systems offer a compact, cost-effective, reliable and maintenance-free alternative to the conventional air insulated sub-station systems. The voltage withstands capability of SF₆ bus duct is strongly dependent on field perturbations, such as those caused by conductor surface imperfections and by conducting particle contaminants. These particles can either be free to move in the GIS bus or they may stick either to an energized electrode or to an insulator surface. If a metallic particle crosses the gap and comes into contact with the inner electrode or if a metallic particle adheres to the inner conductor, the particle will act as a protrusion on the surface of the electrode. Consequently, voltage required for breakdown of the GIS may be significantly decreased. An optimized design of GIS by changing the inner and outer diameter is considered for analysis. It is required to be done because competitive prices of several manufactures of GIS and cost of gas are increasing. The results will have a bearing on the extent of reduction of inner diameter of the HV electrode and the overall volume. This will provide information on the extent of particle movement for the same condition of the gas and particle geometry. The effect of various parameters like radii, length of particles, co-efficient of restitution, pressure in the busduct, applied voltage and inner conductor radii has been examined and presented.