Propagation Characteristics Analysis of Transformer Partial Discharge Signal Based on Bushing External Sensor

Partial discharge detection is one of the main means to discover the insulation defects of transformers and casings. The existing partial discharge UHF detection methods mostly adopt the internal installation method, which limits the size of the sensor and needs to reform the transformer structure. The detection sensitivity of the external casing UHF detection method is greatly related to the installation position of the sensor. Therefore, this paper first establishes the simulation model of electromagnetic wave propagation in casing; secondly, the dynamic process of electromagnetic wave propagation and the signal strength of typical azimuth electromagnetic wave are shown. It is found that the electromagnetic wave propagates outward with the flange gap and the top guide rod as the main radiation source. Thirdly, the influence of flange gap width on UHF detection is analyzed. Finally, the simulation and experiment are combined to obtain that the flange and the vicinity of the elevation are reasonable installation positions of UHF sensors.