Measurement and Diagnosis of PD Characteristics of Industrial Cable Terminations in Extreme Cold Environment

In the alpine region, there are many flashover failures of ethylene-propylene rubber (EPR) cable terminations due to cavity discharges in China high-speed railways (CHRs). The cable termination with cavity defects is used as test samples and a low-temperature PD test system is set up to study the characteristics of partial discharge (PD) of cavity defects in cable termination in those regions. Influences of the different temperatures on internal discharge in EPR insulation at -40°C and 20 °C have been analyzed. When the applied temperature dropped to -40°C, the PD initiation voltage and extinction voltage decreased by 31% and 28%, respectively, and the discharge pulse appeared at both positive and negative half-cycles. The results showed that, at 20 °C, the discharge was mainly caused by the internal discharge of the gas-filled cavity. Apart from the internal discharge of the gas-filled cavity, a marked trace of surface discharge was also detected at -40°C. Besides, the characteristics of PD development at -40°C are closely related to the discharge phase distribution and the asymmetry of the spectrum. The research can further reveal the development and evolution of PD of the gas-filled cavity and provides a basis for judging the severity of termination at low temperature.