Research on the evolution characteristics of interfacial defect inside the vehicle-mounted high-voltage cable termination for high-speed trains

The partial discharge caused by the interfacial defects of cable terminations is an important factor affecting the insulating performance, which will seriously threaten the operational safety of high-speed trains by causing the breakdown fault of vehicle-mounted cable terminations. Simulation combined with experimentation is adopted to study the evolution characteristic of the interfacial defect inside the cable termination for high-speed trains. A simulation model and test samples of high-voltage cable terminations with prefabricated air gap and carbon trace defects are constructed. The results show that the maximum field strength (MFS) at the defect is always located at the end of it. The evolution of the defects can be significantly divided into three stages based on the variation law of field strength and the characteristics of partial discharge. A new feature of stage III is that the volume of discharge in the third quadrant is significantly higher than that in the first quadrant. The PDEV in this stage is 51.41% lower than that of the defect-free cable termination and lower than the operating voltage. Therefore, stage III is critical for the detection of insulation state. The findings of the new characteristics and the conclusions of the study provide strong support for improving the operation and maintenance techniques of vehicle-mounted cable terminations.