New Development for Detecting Partial Discharge Using an UHF Method and Its Application to Power Apparatus in Japan

摘要

Insulation diagnosis has been widely applied worldwide in factories and on-site tests to assure the quality of power equipment. Detection of electromagnetic signals in the ultra-high-frequency (UHF) band from a partial discharge (PD) has been widely studied as a highly sensitive insulation diagnostic method for gas-insulated switchgear (GIS). Many of these studies are based on measurements with actual devices and a few systematic theoretical examinations of the basic characteristics of individual sensors and electromagnetic wave propagation [1]. The most frequently authorized method for detecting PD applies the conventional test standard defined by IEC 60270. The conventional method focuses on the kHz band, although the UHF method, which has been recommended by "CIGRE TF15/33.03.05" [2], uses wide-frequency components from the MHz to GHz ranges. Besides factory and on-site tests for quality assurance, PD monitoring systems have been developed and the UHF method is also applied by manufacturers. The UHF method, however, raises technical difficulties for quality assurance and product development, i.e., the measurement principle is totally different from IEC 60270; calibration is complicated due to attenuation and reflection; and, TE/TM modes propagate inside GIS. Many research studies using the UHF method are cited in this paper to solve the above difficulties with comparative calibration using the UHF method and IEC 60270 [3-5], sensitivity check of PD-detecting coupler in UHF range [6-9], risk assessment based on estimation of defect size [10-13], and advanced classification and quantification method for PD [14, 15].