Frequency domain analysis of electromagnetic wave radiated from partial discharge

Detecting ultra-high frequency (UHF) signal method is becoming more and more popular in the area of monitoring partial discharge (PD) in power transformers. In order to learn the characteristics of the signal, we should pay attention to the frequency spectrum of electromagnetic (EM) wave, which may be influenced by power transformers' inner structures, such as core and winding. In this paper, both with obstacle standing in the propagation way or not, the frequency spectrum of UHF signals radiated from PD source was simulated and compared. It's concluded that, for EM waves radiated from the same PD source, their frequency spectrums are different because of obstacle. In addition, the inner structure of transformer changes the cavity resonance frequency, which may influence frequency spectrum of UHF signals. In order to investigate the mechanism, the resonance frequencies both in situations of removing and setting the core are simulated and compared. Simulation results indicate that resonance frequency changes when there is one core in tank.