Investigation of disc-type sensors using the UHF method to detect partial discharge in GIS

The disc-type UHF sensor is considered among the simplest couplers for partial discharge (PD) detection in gas-insulated switchgear (GIS). This paper mainly focuses on the improvement of the sensitivity of the disc-type sensor. Disc-type sensors with different dimensions were tested on a 220 kV model GIS to find the critical parameters that determine the sensitivity of the sensor. The waveform of the PD signal and the twoport insertion loss were measured to see the amplitude of the output signal and the transmission rate on different frequencies. The FD-TD method was used to investigate the dimension factors in detail along with the effect of the dimension of the tank in which the sensors are installed. The transformation process between the TEM mode and the higher-order modes of the electromagnetic (EM) wave was also simulated to investigate the receiving efficiency of the disc-type sensors for different propagation modes. The results showed that the diameter of the disc and the ratio of the height of the disc to the thickness of the insulation were the most critical parameters that determined the sensitivity of the disc-type sensor.