Ultrasonic detection is an important means of gas insulated substation equipment internal defect detection. This paper analyzes the abnormal ultrasonic signal of a voltage transformer in a 220kV GIS substation in Jiangsu Province. According to the rising trend and the characteristic maps of signal detection results, it is inferred that there may be obvious floating or vibration defects accompanied by slight corona inside the gas chamber. Combined with the disassembly results, it was found that the nylon bolts and nuts were loose, the tightening torque of the iron core steel sheets was invalid, the position of the shielding plate was shifted, and the shielding case had pits and scratches. Comparing the results of energized test and disassembly, it verifies the effectiveness of partial discharge ultrasonic detection in discovering early hidden dangers in gas insulated substation equipment.

voltage transformer;energized test;abnormal ultrasonic signal;vibration defect