The research of partial discharge measurements at ultra high frequency in GIS

Internal partial discharges (PD) may be very harmful to gas insulated substations (GIS) and should be detected and eliminated. Measuring the ultra high frequency (UHF) signals from partial discharges in GIS is a sensitive, effective method to detect the intensity of the discharge. The equivalent models of analysing the UHF resonances in GIS chambers are presented. Calculation results are obtained by using the EMTP program. The PD resonances in both the time and frequency domains are picked up by a coupler built on to the hatch cover plate and an embedded electrode and spacer. These results are also obtained theoretically through Fast Fourier transforms (FFT) and Wigner transforms (WGT). The results of experiments and theoretical analyses fairly agree. The measurement at UHF is free from external electric interference and is very useful and practicable for online monitoring.<>