Analysis of Insulation Defects in Two 66 kV Plug-In Cable Terminals

In view of two insulation defects in 66 kV plug-in cable terminals, test results of AC withstand voltage test, partial discharge detection, cable terminal disassembly, glass transition temperature test and X-ray imaging detection were analyzed comprehensively. Results showed that improper installation of stress cone at A-phase cable terminal led to the gap between stress cone and epoxy sleeve, as well as discharge fault in AC withstand voltage test. Impurities in epoxy sleeve of C-phase cable terminal caused distortion of the electric field and abnormal partial discharge. In addition, some relevant solutions were proposed, defects could successfully eliminated by remaking and installing cable terminals. Carrying out AC withstand voltage test with partial discharge measurement and simultaneously using joint detection method combining a variety of partial discharge measurement methods could effectively improve the accuracy of cable terminal defect diagnosis, which could be of great significance for ensuring safe operation of the cable line.