A Dual-Function Measurement System for Detection of Very Fast Transient and Partial Discharge

The measurements of very fast transient (VFT) in power systems are crucial for fault analysis and location, especially in gas-insulated switchgear (GIS). However, most of the existing GIS is not equipped with the built-in VFT sensor. In China, the ultrahigh-frequency (UHF) sensor has been widely installed in GIS. This article presents a dual-function measurement system designed for detecting VFT and partial discharge (PD) using an UHF sensor. In laboratory amplitude-frequency response tests, the bandwidth of VFT measurement channel was calibrated to range from 0.27 Hz to 90.29 MHz. The UHF sensor can be used as a PD sensor after the VFT measurement, and the sensing characters of PD are not affected by the VFT measurement channel. In practical application, this system was installed in a 500-kV pumped storage power plant. The switching transient voltages during breaker switching operations were successfully measured with a built-in UHF sensor. The maximum overvoltage was found to be 1.40 p.u. This dual-function measurement system provides great potential for accurately measuring VFT without the need for additional sensor installation, which is particularly practical and convenient for already operational GIS substations.