Partial discharge analysis of gas insulated systems at high voltage AC and DC

Partial discharge (PD) measurements are commonly used for monitoring and diagnostics of AC gas insulated systems (GIS). Because of the growing importance of DC GIS, a research project was started focused on the measurement and interpretation of PD signals obtained under DC stress. Results are presented using IEC60270 and unconventional methods through UHF antenna and high frequency current transformer (HFCT) on three different PD generating defects in a GIS chamber. The results of the PD analysis of the defects are compared for AC and DC stress. Phase resolved partial discharge patterns (PRPD) are used for the HVAC analysis, whereas time resolved partial discharge patterns (TRPD) are used for HVDC analysis. Finally, relevant characteristics of PD patterns in HVAC and HVDC are presented and related with the physical phenomena of the discharges.