Partial discharge measurement in DC GIS: comparison between conventional and UHF methods

The detection, identification and localization of defects are essential to ensure the service reliability of Gas Insulated Switchgear (GIS). Partial discharge (PD) measurement is well-known as one of the most effective technique for defect detection and identification in electrical insulation systems. PD measurement according to IEC standard 60270 is known as the conventional technique, in which PD is quantified in terms of apparent charge. Moreover, non-conventional technique, like UHF detection, can also be used for partial discharge measurement to enhance the signal/noise ratio in GIS. For AC electrical insulating systems both techniques are effectives, widely used and give the same signature of defect. Unfortunately, very little information is available for DC systems, especially regarding the comparison of the defect fingerprint between the two methods. The aim of this paper is to investigate the partial discharge signals recorded with both conventional and UHF methods in DC voltage. The results showed that the defect fingerprints are similar between the conventional measurement and the UHF measurement, regardless the UHF antenna position in the equipment.