Research of a loop-type sensor embedded in an insulator in 252kV GIS for partial discharge measurement

It is found that a loop-type UHF sensor embedded in an epoxy insulator in GIS can be used for partial discharge measurement, but it has lower sensitivity in high frequency band than other inner UHF sensors. In order to find the best grounding mode of the loop-type sensor for PD detection, in this paper, 5 grounding modes are used to investigate their influences on the sensitivity of the loop-type sensor. Based on the results obtained above, the loop-type sensor, which is in best kind of grounding mode, is compared with that of the disc-type sensor and the helical sensor by using 4 kinds of the PD defects, including suspended discharge, spiked discharge, free metallic particles discharge, and fixed metallic particles discharge. The results show that the loop-type sensor has the highest sensitivity when it is grounded by two terminals separated by 120 degrees. The loop-type sensor has highest sensitivity compared with the disc-type sensor and the helical sensor, not only in low frequency bands but also in high frequency bands.