Fundamental principles and application of diagnosis for GIS using partial discharge measurements

This article deals with the present status and future trend of the development of partial discharge (PD) measurement using UHF technique and diagnosis technology in GIS by focusing on recent activities and results from our laboratory. Intensive research has been conducted on insulation diagnosis of electric power apparatus such as gas-insulated switchgears (GIS) and transformers by detecting partial discharge (PD) signals, especially the UHF signal, with the electromagnetic (EM) wave propagation mode characteristics considered. When applying the UHF method to the apparatus insulation diagnostics, it is necessary to investigate the effects of the structure and components of GIS such as turnoff part and a spacer on the EM wave propagation in GIS. It is because the EM wave propagating in GIS is affected by a discontinuity part of impedance such as L-shaped structure, T-branch, spacers and so on. Therefore, it is important for reliable diagnosis technique to clarify TE and TEM mode propagation characteristics at the impedance discontinuity part in GIS.