Effect of Extremely Cold Weather and Shrinkage Stress on Interfacial Discharge Between Epoxy and Silicone Rubber in HV Cable Terminations

Gas-insulated switchgear (GIS) cable terminations have higher failure rates at low temperatures. In this study, a 110-kV full-size GIS cable termination model is developed to investigate this failure mechanism. The coupling characteristics of the thermal and mechanical stress distributions in the termination are analyzed. A pressure-controlled interfacial discharge experimental setup is established, and the partial discharge characteristics and damage features of tracking are investigated for different interface pressures. At temperatures as low as −40 °C, pressure distortion is observed at the interface between the stress cone and epoxy bushing, such that the interface pressure can drop below 0.1 mPa. The tracking at low interface pressures has a higher growth rate and fewer and finer branches than at high interface pressures. The accumulated damage area tends to develop from the epoxy resin toward the silicone rubber. As the interfacial pressure drops, the characteristics of the partial discharge change from those for internal discharge type to those for coexistence between internal discharge and surface discharge. Finally, a scheme for tracking development and damage under different interface pressures is proposed to explain the failure process for cable termination in an extremely cold environment, which is highly consistent with the characteristics of actual failure.