Pattern analysis of partial discharges in SF6 GIS

The measurement of partial discharge (PD) of several faults in gas-insulate d system (GIs) is discussed. Phase-resolved PD patterns have been measured using three different PD detection measuring systems: according to the IEC 270 recommendations, a VHF/UHF measuring system with narrow band filtering, and the UHF measuring system with wide band filtering. PD patterns are com pared using computer-based discrimination tools. The influence of the selec ted center frequency on the PD patterns is discussed for the narrow band VH F/UHF measuring system. The influence of the number and type of cIs compone nts between the discharging defect and the capacitive coupler on the shape of the PD patterns is analyzed. For several GIs components the signal reduc tion is studied. It was found that the shape of PD patterns is independent on the used PD detection circuit and the propagation path of the PD signals , As a result, discrimination and classification of PD distributions of sev eral studied defects are possible using digital tools.