Abstract:Partial discharge (PD), as a common fault of transformer, can reduce the loss and improve the reliability of power supply if it can be found in time and restored to normal operation state. In this paper, the propagation characteristics of ultra high frequency(UHF) electromagnetic wave caused by partial discharge in transformer box and the influence of transformer box structure and iron core winding on the transmission of electromagnetic wave signal are analyzed by using UHF detection method and finite difference time domain (FDTD) method. On the software XFDTD, the electromagnetic wave of the partial discharge radiation is simulated in the transformer, and the PD signal arrival time delay caused by the obstacle is predicted, and the difference between the theoretical delay and the theoretical delay is calculated to evaluate the influence on the positioning accuracy of the transformer PD and to analyze it. The simulation results show that the estimation of differential delay is achieved when the PD signal introduced in the presence of obstacles exists in the data output from the two models. Conclusion the transformer box has attenuation effect on the electromagnetic wave, so the sensor should be placed inside the transformer, and the core also has distortion and attenuation effect on the electromagnetic wave. The simulation results show that from the data results of the two models, it is found that the estimated differential delay occurs when the introduced PD signal arrives in the presence of obstacles. The conclusion is that the transformer box has a damping effect on the electromagnetic wave, so the sensor should be placed inside the transformer, the iron core also has distortion and attenuation effect on the electromagnetic wave.