Acoustic detection of partial discharges in insulation oil

In this paper, we performed an insulation diagnosis technique for oil-immersed power transformers by an acoustic detection method. Electrode system such as needle to plane electrode was fabricated to simulate a defect of power transformers. In addition, the frequency spectrum of acoustic signals with partial discharge (PD) in insulating oil was analyzed. From the FFT result, the frequency spectrum of the acoustic signals measured by a wide and a narrow band AE sensors were distributed in the range of 50-170 kHz. Therefore, a narrowband AE sensor with a resonant frequency of 140 kHz is suitable for the diagnosis of oil-immersed power transformers. We could find the position of the PD source with an error margin of 10% in the experiments by calculating the position of the PD occurrence using the time difference of arrival measured by five AE sensors.