Suppression of very fast transient over voltages in Gas insulated Substations an Experimental Investigation

Abstract

In Gas Insulated Systems (GIS), Very Fast Transient Over voltages (VFTOs) are caused mainly due to switching operations and newlineinternal insulation flashovers. These VFTOs can reach to high amplitude and steepness. The generated VFTO s can also lead to secondary breakdown in GIS. Further they may give rise to electro-magnetic interference (EMI). The VFTOs cause the following effects. The electromagnetic interference effect during Disconnector switching results newlinefailure of electronic and control circuits connected to GIS. Dielectric strength of SF 6 gas is reduced under VFTO, if non-uniform electric field is formed by the metallic particles. VFTOs results failure of insulation of components such as bushings and transformers. The suppression of VFTOs in GIS has been a long standing problem. newline