Characteristics of external loop sensor located near bushing on partial discharge measurement

Partial discharge (PD) monitoring technique using UHF method becomes more popular because of its higher S/N ratio. Amongst novel sensors, loop sensor could be a candidate for PD detector to measure UHF signal emitted from PD source. This paper gives the experiment result on characteristics of loop sensors. The characteristics of three loop sensors with varying diameter were examined using a spectrum analyzer and a network analyzer to obtain frequency characteristic and S11 parameter, respectively. Then, PD experiment was conducted on 66 kV GIS model having floating electrode and free metallic particles as its PD source. The loop sensors were placed far external to GIS busing to measure leaked PD signal from it. The influences of the sensor diameter and the sensor locating distance from GIS bushing on PD detection sensitivity were also examined. Based on IEC-60270 standard measurement, the highest sensitivity of 30 pC was obtained from this research. The result suggests that higher sensitivity could be achieved with proper shielding and suitable filter design against external noise.