Influence of GIS Tank Size on First-incoming PD-induced Electromagnetic Wave in Terms of Risk Assessment of GIS

The authors have investigated insulation diagnostic technique for gas-insulated switchgear (GIS) by detecting partial discharge (PD) signals, particularly PD current, PD-induced electromagnetic wave and AE signal. So far, we have experimentally shown that discharge type such as streamer and leader-type discharge can be discriminated by introducing an amplitude ratio of the positive peak value to the negative one of the first-incoming electromagnetic wave with UHF method in the 66kV model GIS. In this paper, we investigate the influence of GIS tank size on propagation properties of PD-induced electromagnetic wave by finite difference time domain (FD-TD) method to derive a criterion to discriminate discharge type. From the calculated results, we discuss the influences of GIS tank size and sensor position on discrimination of discharge type in terms of risk assessment of GIS with focusing on the influence of higher TE modes, especially TE11 mode, of propagating electromagnetic wave.