Detection and Diagnosis of Multiple-void Discharge Sources in On-site 550kV GIS Insulating Spacer

This article introduced a case of on-site detection, return test and diagnostic analysis of a multiple voids discharge in 550 kV GIS insulating spacer. First, the abnormal signal of the on-site 550 kV GIS insulating spacer is detected by employing the UHF method, whose UHF signal pattern presents as void discharge. After the replacement of the insulating spacer, the withstand voltage, partial discharge (PD) test, X-ray inspection, lightning impact test are applied to this insulating spacer. The pulse current and UHF method are combined together to investigate the discharge characteristics of multiple voids in this insulating spacer. The discharge characteristics including initial discharge voltage and the extinction voltage, are compared before and after the lightning impact voltage test. Finally, the UHF signals of this insulating spacer are clustered by multisource discharge separation method. It is found that, there are eight voids linearly distributed inside the insulating spacer. The amplitudes of UHF and pulse current signals are positively correlated, and the discharge spectrum characteristic changes from single-void discharge to multiple-void discharge with the increase of voltage. The PD initial voltage of the insulating spacer decreases while the PD extinction voltage keeps same after the lightning impact voltage test, and the signal amplitudes of the UHF and pulse current methods increase rapidly. The discharge multiple source separation shows that the UHF signal of the insulating spacer can be divided into two clusters, which is consistent with the two distribution areas of voids. This article provides on-site experience for insulation detection and diagnosis of GIS.