Partial discharge characteristics in aged EPR, 15 kV rated cables

Several 15-kV rated, EPR cables subjected to aging processes were examined for partial discharge (PD). These cables were subjected to different load cycling while fully immersed in water to obtain different aging conditions. PD initiated in these cables then was measured at rated and elevated voltages. Correlation then was examined between the PD signature and the type of insulation defect. This achieved by comparing the PD frequency, magnitude and phase angles of different insulation defects. Correlation between the PD level and the ac-breakdown voltage of these cables also was presented in this paper. The same investigations also were repeated on several cables removed from service after 15-20 years of service.