Study on performance of HFCT and UHF sensors in partial discharge detection

The partial discharge (PD) which is caused by the deterioration of insulation of high voltage (HV) equipment is a progressive degradation that often starts with small current but finally leads to destruction of HV system. Exact detection and measurement of PD occurrence is thus very important. Since the PD pulses have wide frequency band, the PD measurement methods with higher frequency resolution is needed. Two kinds of popular measurement methods: high frequency current transformer (HFCT) and ultra high frequency (UHF) like sensor are tested under different sampling frequency in this paper. Comparisons of their performance in time and frequency domain are done. The results show that both measurement systems have their own characteristics: the UHF-like sensor with wider frequency spectrum is more sensitive than HFCT, but the HFCT which is directly connected to HV apparatus can detect PD pulses with higher magnitude.