Sensitivity of the UHF-method for defects in GIS with regard to on-line partial discharge detection

Abstract

This paper presents measurements which have been carried out to investigate the sensitivity of the narrowband ultra-high-frequency-method (UHF-method) for partial discharges (PD) in gas insulated substations (GIS). The narrowband UHF-method is compared to the conventional PD detection method according to IEC 270. The following defects were investigated under laboratory conditions: fixed protrusions; free particles, particles on spacers; gas-filled cavities; and floating electrodes. The PD signals are evaluated for the narrowband UHF-method and the IEC 270 method as a function of the electrical field strength. The results can be used to evaluate different field stress conditions and voltage levels in GIS. The measured results are discussed with regard to the online PD monitoring of GIS.