Partial discharge of cable termination on electric multiple unit of China high-speed railway below zero-degree centigrade

摘要

Ethylene propylene rubber (EPR) cable terminations have great potential in improving the operational reliability of electric multiple units, for their high elasticity and low loss. However, the breakdown of EPR cable terminations frequently occurred in northwestern China during winters. In this study, tests were conducted to investigate the effect of temperature (-40 to 20 degrees C) on partial discharges (PDs) characteristics, characteristic transition temperature, and breakdown process of cable termination. In samples with no artificial defects, it was found that the average PD inception voltage (PDIV) decreased obviously by 45% when temperature reduced from 20 degrees C to -40 degrees C. Meanwhile, the PD amplitude increased rapidly with decreasing temperature. The symmetric phase resolved PD pattern also changed from turtle-like' to wing-like' shape with decreasing temperature. Differential scanning calorimetry results indicated that the decrease of mechanical mismatching between EPR and stress control tube (SCT) at low temperature led to decreasing PDIV. A physical model of electric field (EF) distribution within cracks on EPR/SCT interface inside the termination was designed. Distortion of the EF by simulation was consistent with the discharge channel in the test. These results showed that the decreasing temperature had significant influences on the PD initiation of EPR cable termination.