Frequency Characteristics of Electromagnetic Waves Radiated from GIS Apertures

Partial discharge (PD) measurement using electromagnetic waves by antennas is a promising technique for diagnosing the insulation performance of gas-insulated switchgear (GIS). In order to establish highly sensitive diagnosis techniques of GIS insulation, frequency characteristics of electromagnetic waves, which are determined by GIS apertures such as insulating spacers and bushings, should be clarified. In this paper, we measure the electromagnetic waves radiated from different GIS apertures and also analyze them using the transient analysis program "PSpice." Comparing the measurements with the theoretical analyses, we investigate the relationship between the GIS aperture configuration and the radiated electromagnetic wave spectrum from the aperture. We also discuss how the aperture condition contributes to the radiation characteristics of electromagnetic waves. Finally, we conclude that the electromagnetic waves radiated from the GIS aperture are based on different radiation mechanisms in frequency.