Partial discharge caused by interfacial defects of cable terminations is an important factor affecting insulating performance

which will seriously threaten operational safety of high-speed trains by causing a breakdown fault of vehicle-mounted cable terminations. Simulation combined with experimentation is adopted to study the evolution characteristic of interfacial defects inside 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. Results show that maximum field strength (MFS) at the defect is always located at the end of it. Evolution of the defects can be significantly divided into three stages based on the variation law of field strength and characteristics of partial discharge. A new feature of stage III is that volume of discharge in the third quadrant is significantly higher than in the first quadrant. PDEV in this stage is 51.41% lower than that of the defect-free cable termination and lower than operating voltage. Therefore

stage III is critical for detection of insulation state. Findings of the new characteristics and conclusions of the study provide strong support for improving operation and maintenance techniques of vehicle-mounted cable terminations.