유중 부분방전의 음향검출에 관한 연구

Abstract

This thesis describes the frequency spectrum, positioning and propagation characteristics of the acoustic signals produced by the partial discharge(PD) in applying an acoustic detection technique for on-line insulation diagnosis of oil filled transformers.

Some defects were simulated by needle-to-plane, plane-to-plane and floating electrode systems. The acoustic signals were analyzed using a wideband AE sensor with frequency ranges of 100[kHz]∼1[MHz] and narrowband AE sensor with resonant frequency of 140[kHz].

A decoupler and an amplifier were designed to detect and amplify only the acoustic signals. The decoupler separates the acoustic signal from the DC source without any distortion, and the amplifier produces a gain of 40[dB] in frequency ranges of 11[kHz]∼4[MHz] at -3[dB].

From the experimental results, it was confirmed the frequency spectrums of the acoustic signals were 50[kHz]∼180[kHz] for the needle-to-plane, 50[kHz]∼200[kHz] for the plane-to-plane and 50[kHz]∼150[kHz] for the floating electrode system. Using the three AE sensors, the positioning error of the PD was calculated to be within 3[%]. Also, output voltage, as a function of applied discharge magnitude, was linear, while the measured sensitivity of this experimental configuration was 23.65[mV/pC].

Therefore, this paper concludes that the acoustic detection technique for on-line insulation diagnosis of oil filled transformers could be used reliably.