Phase angle calculation for UHF partial discharge detection in segment acquisition mode

Phase angle of PD pulse is an important parameter of PD pattern, and its accuracy determines the effectiveness of PD pattern recognition based on phase-resolved distribution analysis. In this paper, a novel phase angle calculation method for UHF PD detecting systems in segment acquisition mode is proposed. This method use a synchronous circuit to output UHF marker signals with certain frequency characteristics to represent the rising edge of zero-crossing points of power frequency signal. The UHF PD detection system receives both marker signals and PD pulses, and records the occurrence time of all of the UHF pulse signals. Those two types of signals could be separated and marked by calculating their different time-frequency characteristic parameters using fuzzy clustering method. Then the phase angle of PD pulses could be calculated from the time difference between the UHF PD pulses and the neighboring zero-crossing points of power frequency signal. This method realizes the phase angle calculation of UHF PD signals without sampling power frequency signal, which greatly simplifies the structure of the system and reduces its requirements for data processing. The validity of the method is verified by experimental application in Laboratory.