Research on Built-In Coupling Sensor for Partial Discharge Signal Detection in Cable Joints

Aiming at the complex structure of cross-linked polyethylene(XLPE) power cable joints and the characteristics of partial discharge(PD) easily caused by insulation defects, the paper designs and develops an improved built-in coupling sensor based on capacitive coupling effect. Firstly, by constructing the equivalent circuit model of the sensor, the transfer function of the sensor is calculated, and the factors affecting the detection performance of the sensor are comprehensively analyzed. Secondly, based on the analysis of the detection performance of the sensor, the design scheme of the effective detection frequency band of the sensor is determined, and the structural size of the sensor is determined, including the width of the ring electrode and the thickness of the insulating cushion of the sensor. Finally, the key performance test experiments are carried out on the developed sensor. The test results show that the effective detection frequency band of the sensor is $1 \sim 300$ MHz, and the effective detection sensitivity is 5pC, which can effectively detect the internal PD signal of the cable joint.