Study of partial discharge electromagnetic wave signal leakage characteristics of transformer oil-paper insulated bushings

In order to reasonably evaluate the effectiveness of UHF sensor arrangement in online monitoring of partial discharge of bushing, it is necessary to study the electromagnetic wave propagation characteristics of partial discharge UHF in the bushing. In this paper, a three-dimensional model of a real transformer bushing is established, the XFDTD software is used to simulate the raised seat defects and internal capacitive core defects of the bushing, field strength sensors are arranged at different locations inside and outside the bushing, and the propagation process of partial discharge UHF signals leaking from the oil-paper insulated bushing to the external free space is simulated and analyzed. The results show that the time difference between the signals received by the field strength sensors at different locations is not significant and can be neglected in practice. The partial discharge electromagnetic wave signal generated by the bushing elevated seat defect leaks from the upper porcelain sleeve to the external space, and the leaked electromagnetic wave energy is mainly gathered at the upper and lower ends of the upper porcelain sleeve. The partially discharged electromagnetic signal at the capacitor core inside the bushing will propagate along the coaxial waveguide structure formed between the capacitor screens towards the two ends of the capacitor core, the downward propagating electromagnetic wave energy is confined within the elevated seat, the upward propagating electromagnetic wave energy propagates from the top of the upper porcelain bushing to the external space, the leaked electromagnetic wave energy is mainly concentrated at the top of the upper porcelain bushing. The simulation results provide ideas for optimizing the arrangement of external antenna sensors for UHF detection of partial discharges in transformer oil-paper insulated bushings.