For a 220kV substation with 35kV capacitive voltage transformer secondary voltage abnormal drop fault, this paper introduces the structure of capacitive voltage transformer and its working principle. Then, combined with fault phenomenon, diagnostic test data, equipment disintegration inspection, the cause of the fault as ferromagnetic resonance overvoltage causing insulation breakdown of the differential and angular coils is analyzed and determined. Finally, some suggestions are put forward for the infrared temperature measurement and secondary voltage monitoring in the daily operation and maintenance inspection to improve the reliability of capacitive voltage transformer operation.

capacitive voltage transformer  /  voltage anomaly  /  ferromagnetic resonance  /  insulation breakdown