Effect of the presence of epoxy spacer on transmission rate of electromagnetic wave propagating through T-branch of 66 kV GIS model tank

This paper deals with the influence of the presence of the epoxy spacer on the transmission rate of partial discharge (PD) induced electromagnetic (EM) wave propagating through TBranch of 66 kV GIS model tank. The partial discharge sources are a particle on the conductor and a free particle on the tank. PD induced EM wave was measured by ultrahigh frequency (UHF) sensors and observed by the oscilloscope and the spectrum analyzer. A low pass filtering (LPF) process for the cut off frequency of TE11 mode was used to eliminate the higher order mode above TE11 of the detected signal. In addition, a high pass filtering (HPF) process for the cut-off frequency of TE11 mode was used to eliminate the lower frequency component below TE11 of the detected signal. We discussed the effects of the T-branch and the effect of the presence of the epoxy spacer on the peak to peak amplitude Vpp of the propagating EM wave before and after the LPF and HPF processing. We compared the transmission rate (TR) of the propagating EM wave before and after LPF and HPF processing through T-branch in straight direction (TRS) with TR of EM wave before and after the LPF and HPF processing turning at a right angle at the T-branch (TRT) in the presence and in the absence of the epoxy spacer. The results showed that the transmission rate (TR) of EM wave in the presence of the spacer was generally lower than one without spacer. TR of a particle on the conductor was higher than TR of a particle on the tank. TRT was larger than TRS. It was found that TR of low frequency component (TRLF) of EM wave signal was higher than TR of high frequency component (TRHF) with and without epoxy spacer.