Partial Discharge Characteristics During Treeing Process in Silicone Rubber at 20 and −100 °C

In the operation of high temperature superconducting cable, the temperature in current lead or connector with traditional cable varies from -196 °C to above 0 °C. As a main reason of the insulation aging, electrical tree characteristics change with the temperature. In this paper, partial discharge (PD) signals of electrical tree are detected by a high-frequency current transformer. The experimental temperature was set to be 20 °C and -100 °C. To analyze the PD signal, the phase resolved partial discharge (PRPD) is calculated. Besides, the multiscale permutation entropy (MSPE) is also employed to characterize the nonlinear dynamic feature. The result indicates that the low temperature suppresses the PD, which will influence the PRPD. At -100 °C, PD starts occuring at the phase from 90 °C to 135°, and then it begins to occur at 270° after 10 min. However, PD occurs at 90 °C and 270° when the temperature is 20 °C. The MSPE can characterize the different treeing stage obviously. At both 20 °C and -100 °C, the stable MSPE value in the first 20 min is close to each other and becomes scattered in the next 40 min.