Partial Discharge Charge Estimation In Gas-Insulated Substations Using Electric and Magnetic Antennas

Abstract

Partial discharges (PD) measurements provide an estimation of the severity of the insulation degradation; additionally, it is used as a unit of standardization. Up to now, only the IEC 62478 briefly mentions partial discharge measurements using electromagnetic sensors in gas-insulated substations (GIS). The IEC60270 standard provides a method for PD charge measurement when the test object approximates to a lumped element; PD in SF 6 are in the range of nanosecond, and given the GIS length, it behaves as a transmission line. This work compares different sensors (commercially available and developed by the authors) used for measuring PD charge magnitude in GIS. The sensors’ sensitivity, time resolution, and charge estimation accuracy are tested in a full-scale 420 kV GIS. A nanosecond rise time pulse was connected to the GIS through a transition cone to provide a good PD representation. The pulse was measured by electric and magnetic sensors installed in mounting holes located in different sections of the GIS, and a directional coupler was used as a reference to the injected pulse. This work demonstrates that the charge magnitude can be extracted using different sensors, harmonizing the reading from different measuring systems. The results show the possibility of a standardized method for on-line PD measurements and routine and after-installation tests.