The application of ultra-high-frequency partial discharge measurements to gas-insulated substations

This paper deals with the application of the ultra high-frequency method (UHF-method) for the detection of partial discharges (PD) in gas-insulated substations (GIS). First, a review of the GIS-relevant part of the theory of electromagnetic wave propagation in the UHF-range (300 MHz-3 GHz) is given. New information considering the attenuation due to reflections of UHF signals at spacers is presented. For the sensors used to pick up the UHF signals inside the GIS, a new description of an antenna valid in the UHF range is introduced. The second part of this paper presents measurements with the UHF method to compare the sensitivity to the conventional PD detection method according to IEC-270. Practical conclusions are drawn from these new results for the application of the UHF method for onsite testing and online PD monitoring of GIS