Partial discharge measurement for transformer insulation using wide and narrow band methods in ultra high frequency range

The ultra high frequency (UHF) detection method of partial discharge (PD) is presented in this paper. The log spiral and conical sensors were developed and used with a spectrum analyzer to detect PDs. Measurements of signals produced by two artificial PD defects were carried out in both broad and narrow band frequency ranges. The effectiveness of the sensors was compared and shown in this paper. Both sensors are capable of detecting the signal emitted by artificial PD defects. The phase resolved partial discharge (PRPD) results from the UHF detection method show strong similarity to those obtained from the conventional IEC 60270 measurement system. For the same PD level, the conical sensor shows higher signal magnitude but the log-spiral sensor offers better noise rejection at frequency below 300 MHz. Both sensors are capable of detecting PDs with magnitude above 30 pC.