Temperature dependence of return voltage characteristics

Recently the return voltage measurements have been proposed fir the diagnostics-on the high voltage equipment characterising the dielectric properties of insulation systems. The application of return voltage method at the diagnostics of the "V current tran&nners are presented in this paper. The return voltage characteristics such as maximum of return voltage, the initial slope ofreturnvoltage and the time to peak value dependencies on charging time are discussed. These characteristics vary depending on the ageing changes of the insulation. That indicate for a possible applicability of the technique for assessing the state oftransformer insulation. The investigations oftemperature influence on the return voltage characteristics were aimed to determine the state of the insulation under operating conditions. The theoretical analysis ofthe results allows to calculate the temperature of insulation that corresponds to the thermal breakdown of insulation.