Detections of ultrasonic sensor and PMT on partial discharge in oil under DC voltage

In the light of the characteristics of DC partial discharge, a set of typical DC partial discharge simulation model in the converter transformer was designed and built. This paper applies non-electrical measuring methods :ultrasonic sensor and photoelectric detection means such as photomultiplier tube (PMT) to test the partial discharge signals. Non-electrical measuring methods have strong ability of resistance to electromagnetic interference. The test results show that the ultrasonic sensor detect the real-time changes of the signal effectively, and the overall trend of the average largest amplitude of ultrasonic pulse will rise with the voltage increases, but the duration and the intensity of each signal may not be detected effectively by this means. However, PMT can be used to detect the intensity of amplitude of the signal under different voltage, and can monitoring the discharge duration sensitively. PMT can be used to measure the amplitude of initial discharge voltage and the initial discharge development time. Its measurement data can provide basis for the optimization of converter transformer insulation structure.