Study on relationship between optical signals and charge quantity of partial discharge under four typical insulation defects

In order to solve the problem of the optical method for detecting partial discharge (PD) in the electric equipment in quantity, the integral value of the signals from the optical method has been analyzed to reflect naturally the energy of light released by PD from the principle of the optical method, then a linear relationship between the integral value and the charge quantity of PD has been deduced to give a guidance to detect charge quantity of PD in Gas Insulated Switchgear (GIS). Afterwards, as the result of PD experiments on four typical insulation defects in GIS based on optical method coupled with impulse current method, the relationship between the average integral value of signal of the optical and the average apparent charge quantity presented linear. However, the relation curve of different defects might be distinct as the PD properties under different defects were distinct. Besides, the distance between two electrodes would also influent the linear relation. The longer the two electrodes separate, the greater the slope of the relation curve would be. Therefore, PD charge quantity might be calculated through optical signal when the defect type could be assured. Results all above shows that the type and level of PD could be determined using the optical method, hence the PD online monitoring and fault diagnosis based on the optical method is feasible.