Simulation of propagation characteristics in three-phase-type GIS

Based on the Helmholtz equation, the wave functionsof three-phase-common-type tank GIS are solved. It is shown that, due to the existence of the structural misalignment, any single normal mode of a perfectcoaxial structure no longer simultaneously satisfies both the outer and inner boundary conditions;Through the finite element analysis (FFA), the electric field distribution of the partial discharge(PD) electromagnetic wave(EM-wave) leak from insulating spacer and the effect of the metal bolts on the leaking EM-wave are analyzed, the simulation shows that when the PD occurs between the high voltage conductor and the tank, theelectric field distribution of PD EM-wave leaking from the insulating spacer adjacent to the PD source is non-uniform, which is different from the situation of PD occurs between the high voltage conductors. Thestructure formed by bolts and flanges has shielding effectiveness to the leaking EM-wave. Theshielding effectiveness to the leaking EM-wave´s low frequency componentis higher than that to the high frequency component. Also the structure forms a slot antenna and has a resonant frequency, at which the output of externally leaking EM-wave is higher and enables more sensitive measurement.