Analysis of Electric Field Intensity in Gas Insulated Busduct

Gas insulated substations (GIS) have received great interest in the recent years. One of the advantages of GIS over conventional substations is their compactness which makes them a favourite for service in urban residential areas. These consists conductors supported on insulator inside on enclosure filled with sulphur hexafluoride (SF6) gas. 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 acquire charge due to the electric field intensity. Nearly 50 % of GIS failures are due to metallic conducting particles lifted by electric field and migrate to conductor or insulator initiating breakdown at voltages significantly below the insulation characteristics. This paper analyses the electric field intensity for different dimensional conductor and enclosures at various applied voltages in a three phase Gas Insulated Bus duct. Electric field intensity decreases with increase in diameter of enclosure