Real-Time PD Identification in Diagnosis of GIS Using Symmetric and Asymmetric UHF Sensors

A new practical method for real-time insulation diagnosis of gas-insulated switchgear (GIS) has been developed and introduced. A notable technique, which takes the output ratio of a symmetric ultra-high-frequency (UHF) sensor (e.g., a loop electrode) to an asymmetric one (e.g., a conical coupler), makes it possible to immediately identify defects and also to eliminate noises because the output ratio of those UHF sensors strongly depends on the radial position of the GIS. It would be remarkably effective for dc power transmission, intermittent partial discharge (PD), and sequential risk assessment based on each identified PD pulse, which would support condition-based maintenance.