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The diagnosis algorithm using ultra high frequency (UHF) method with the higher-order electromagnetic wave (EM-wave) was examined as the advanced partial discharge (PD) diagnosis method in a gas insulated switchgear (GIS) in the former paper. Previous studies evaluated the characteristics of EM-waves propagated in a simple coaxial cylindrical pipe, or through an L-shaped or a T-shaped pipe formed by combining these. In the present study, components (a hand hole, a post-type spacer, etc.) present in an actual GIS structure were identified, and an evaluation done mainly through an analysis on what effects their presence has on the mode transformation of EM-waves propagated inside a GIS tank. The direction in which a GIS tank is bent is horizontal (0deg) in the L-shape structure. If there is either a post-type spacer or a shield ring inside, and the signal source is in the 0deg direction, the distribution of the EM-wave strength varied according to through the L-shape structure. Also in the case of a T-shaped structure, the distribution of the output after signals are transmitted through the T-shaped junction varied depending on each component. Based on these characteristics, the diagnosis algorithm for PD with higher-order mode EM-waves was improved taking into account the effects of various components existing in an actual GIS, and a PD diagnosis method more suitable for an actual structure was established.