Discharge characteristics of typical defects in GIS based on electro-thermal coupling

Partial discharge (PD) is the main cause of insulation failure in gas insulated switchgear (GIS). The actual operating environment of GIS equipment is complex, and temperature is one of the important environmental factors affecting the PD characteristics of GIS. In order to clarify the influence of temperature on PD characteristics of typical defects in GIS, a joint acquisition platform for PD information under electro-thermal coupling conditions is established in this paper. Surface metal contamination, insulator air gap defects, suspension electrode and metal protrusion defects are set up. And the PD signals of four defects at various temperatures and voltage levels are collected by pulse current method and ultra-high frequency (UHF) method. Results show that at the same voltage level, the temperature increasing has the most significant impact on PD characteristics of insulator air gap defect, and has the least impact on suspension electrode defects. The PD inception voltage (PDIV) decreases by about 15.5% on average, and the average growth rate of discharge capacity is 59% for four defects with temperature from 25°C to 75°C. The maximum discharge amplitude increases by more than 1.2 times, and the discharge frequency increases on average by 4.85 times. The discharge signals phase distribution becomes more random and dispersed, and the discharge density and intensity also increase. At various PDIV levels, high temperatures substantially reduce dielectric strength, thereby facilitating partial discharges. The research results of this paper can provide a basis for PD monitoring and diagnosis of GIS equipment in complex environments.