Decay characteristics of residual dc voltage for 1000 kV GIS

Volume and surface resistivity are varied by temperature and electric field strength of an insulator. As change of the insulator electric field strength is very small during residual dc voltage measurement, insulator resistivity depends on temperature. So insulator resistivity is estimated by fundamental characteristics of resistivity as a function of temperature. Then the decay time constant of residual dc voltage for l000 kV GIS is calculated by resistivity based on the calculated insulator resistance for the temperature. Finally the measured decay time constant is compared with the calculated one.