Simulation of propagation characteristics of higher order mode electromagnetic waves in GIS

Numerical simulation of electromagnetic fields was performed to investigate the transmission and reflection characteristics of electromagnetic waves excited by partial discharge through spacers, L-shaped sections of a GIS bus structure. The resonance frequencies of a cavity between spacers agreed roughly with the experiment. The modes of electromagnetic wave are shown to transform to different modes, e.g., from TE11 to TE21 mode, after transmission and reflection through L-shaped sections of a GIS. The frequency intervals of the resonance in tank´s longitudinal direction for a L-shaped section are different between horizontal and vertical excitation of partial discharge source. The two characteristics, mode transformation and the dependence of resonance frequency on excitation direction, were confirmed experimentally