Calculation of deposited charge and electric stress at insulator in SF6 gas

Conical insulator in a gas-insulated substation is considered to withstand DC electric stresses that cause the ion charge deposition. The field distribution across this insulator with long creepage paths and field distortion due to the deposition of charge on the insulator surface is calculated on a geometry model by finite element techniques. The applied voltage was a IEC standard surge wave and the charge deposition was dependent on the electric field between the busbar and the insulator concave surface. The results of field analysis were verified by the standard measurements on high voltage insulators in a real scale SF6 gas compartment.