A field calibration method based on forward transport coefficient for UHF partial discharge detection sensors in GIS

To ensure the effectiveness of ultra-high-frequency (UHF) method on the on-line monitoring and live detecting of partial discharge (PD) for the gas-insulated metal-enclosed switchgear (GIS), this paper proposes a field calibration method for the UHF PD detection sensors in GIS, which is based on the forward propagation coefficient in the microwave network theory. Firstly, on a full-scare test platform of a 252 kV GIS, the forward propagation coefficients between several pairs of UHF sensors were measured, which agreed well with the frequency spectrum characteristics calculated by the pulse injecting method indirectly and those of PD with different defect types. Then, the criterion corresponding to the detection sensitivity of 5 pC for the proposed method was studied, that is the mean value of forward propagation coefficient between 300MHz and 1.5GHz is not less than -75 dB. Finally, the proposed method including the criterion was applied to the field calibration for the sensitivity of the PD online monitoring UHF sensors in an 1100 kV GIS. Through the above research, differentiated arrangement of UHF sensors was suggested for the on-line monitoring and live detecting of PD in GIS.