Interpretation of PD in GIS using spectral analysis

This paper reports on VHF/UHF detection of partial discharges in SF/sub 6/ gas insulated substations (GIS). A measuring circuit for this purpose consists of a spectrum analyser connected to a high frequency sensor inside the tested GIS. In particular the use of a spectrum analyser for PD measurements is described and its applicability is validated. Using several examples measured on GIS, the interpretation of frequency spectra is explained. It is shown that characteristic key values obtained from the frequency spectra can be very useful for trend analysis of PD measurements.