Analysis of Time-Frequency Characteristics of PD Electromagnetic Wave Based on Electromagnetic Simulation

The electromagnetic wave excited by Partial Discharge (PD) suffers severe signal fading caused by equipment, free space and the effects of multipath, when it propagates from PD source to Ultra-High Frequency (UHF) sensor. These effects make the waveform and energy of the signal received by the sensor greatly differing from the original signal. In order to accurately obtain the time-frequency characteristics of the PD pulse signal received by the sensor, analyze the factors affecting its change and searching about PD source location and pattern recognition, it is necessary to analyze the radiation mechanism and propagation process of PD electromagnetic wave deeply. This paper carried out the research on propagation characteristics of PD pulse in the space of substation based on the electromagnetic simulation. The paper firstly used the equivalent model of electric dipole to analyze the basic principle of PD electromagnetic wave radiation, and then simulated the propagation of PD electromagnetic waves in a real open-type substation 3D model based on CST microwave studio, which is an electromagnetic simulation platform. The oscillation, time delay and frequency spectrum of PD electromagnetic wave detected by probes at different distances from PD source were analyzed on E-plane and H-plane in UHF frequency band. The simulation results show that the electromagnetic simulation can obtain the changing rule of the time-frequency characteristics about PD electromagnetic wave propagation, and also explain that the different propagation distance and the complexity of channel in propagation path can greatly affect the time-frequency characteristics of PD electromagnetic wave. Meanwhile, the simulation results also provide guidance for PD sensor positioning in the substation and parameters setting. And some proposals for time delay algorithm selection in PD location are offered as well.