Research on External Partial Discharge of Transformer Bushing Based on UHF Method

The main function of the transformer bushing is to support and connect the transformer lead-out line. In recent years, bushing faults have occurred frequently but there is not good online monitoring method for bushing. The ultra-high frequency (UHF) detection method has the characteristics of strong anti-interference ability and no influence on equipment operation while achieving non-contact measurement. This paper has studied the phenomenon of the bushing by artificially setting the partial discharge fault on the 35kV bushing, and the improved time difference algorithm is used to locate the partial discharge source, forming a preliminary analysis method and research ideas for the bushing. The UHF signals of Phase Resolved Pluse Sequence (PRPD) of the bushing corona discharge is mainly concentrated between 30°~80° and 210°~260°, and the amplitude is relatively dispersed, and the stable discharge in one cycle with the tap suspended discharge has a wider distribution range and a smaller relative amplitude, since the tap is closed to the flange, partial discharge occurs at a lower voltage, and the signals are distributed between 0° and 100°, 170°~250° and 330°~360°, but the discharge charge is relatively small. The analysis of the received signal of the UHF sensors can determine the time difference of the signal reaching different sensors, and the specific position of the PD source can be calculated by the time difference with a few centimeters error from the actual position.