Effect of SF6 pressure on the sensitivity of partial discharge detection of typical defects in GIS

Abstract

The gas pressure of gas insulated switchgear (GIS) is the key factor affecting the sensitivity of partial discharge (PD) detection. In this paper, four defect models, tip, suspension, void, surface, are constructed on the PD experimental platform. PD experiments are carried out at different pressures, 0.2 MPa-0.5 MPa. Ultra-high frequency (UHF), high-frequency current transform (HFCT) and acoustic emission (AE) methods are used, and the sensitivity of HFCT and AE methods for PD signal detection is compared. The results show that SF6 pressure is a key parameter affecting tip discharge, suspension discharge and surface defect discharge. Under these defects, the partial discharge initial voltage (PDIV) is proportional to SF6 pressure, and the discharge amplitude and pulse number are inversely proportional to SF6 pressure. For the void defect, the change of external SF6 pressure does not affect the void gas pressure, and thus does not significantly affect the cavity discharge intensity. The HFCT method can effectively detect suspension defects, however, it cannot detect the PD signals of void and tip defects. As the SF6 pressure decreases, the sensitivity of HFCT method to detect surface defects increases, although the sensitivity is not comparable to that of the UHF method. The AE method can detect suspension and tip defects effectively, but cannot detect PD signals of void and surface defects. The detection sensitivity of the AE method for tip defects gradually increases with the decrease of SF6 pressure. When the pressure is 0.2 MPa, the detection sensitivity is equivalent to that of the UHF method.

Keywords

• gas insulated switchgear (gis)
• partial discharge
• insulation defect
• sf6 pressure
• sensitivity
• discharge detection