On-site partial discharge test of medium voltage switchgear by time of arrival method

A substation of Dongguan Power Supply Bureau which contains 22 switchboards are surveyed with partial discharge (PD) instruments. During the inspection, it is found that both the transient earth voltage (TEV) and acoustic signal of one switchboard is much stronger than that of all the others. Therefore, we have initial suspicion that there existed PD signal in the switchboard and then came the PD source location stage of the switchboard which employed a 4-channel high speed oscilloscope to obtain the original time domain PD waveforms. By using time of arrival algorithm to analyze the large amount of PD waveforms data, we eventually confirmed that the signal did come from this switchboard. Finally, the switchboard was disassembled and the PD location checked. And the disassembled result verifies the authors' speculate.