Stress calculation at distorted field of high voltage insulator in SF6

GIS (gas insulated substations) conical insulators from a cast epoxy resin were considered in their shape to withstand AC and DC stresses. The transient field distributions across these insulators with long creepage paths and field distortions due to the depositions of charge on the insulator surfaces were calculated on a model using finite element technique. The influence of shapes of insulator and surrounding electrodes was calculated and test results verified this approach in the analysis of high voltage insulators in SF6. A fast improvement in shapes of insulator and surrounding electrodes can be achieved due to realistic simulation of gas behaviour.