음향신호의 유중 전파특성에 관한 연구

Abstract

This thesis dealt with the propagation characteristics of acoustic signal in insulation oil for the purpose of improving the reliability of acoustic emission (AE) method used for degradation monitoring of oil-immersed transformers. A discharge source was placed in insulation oil and AE sensors(140 kHz) were attached on the oil tank to study the changes of velocity and propagation path with the depth and distance. The average velocity was 1,436m/s and the velocity decreased with the increase of depth from the oil surface to 430mm. The propagation paths were classified into three sections by the shortest reflection path of the detected signal. The minimum distinguishable distance in each section was 70mm. In addition, with the application of average velocity and propagation path, a partial discharge (PD) positioning algorithm was designed using the time of arrival (TOA) based on LabVIEW program. It was also verified that PD with a magnitude over than 526.3pC can be detected by the AE sensors. The proposed algorithm could localize PD with a error below 2%, which was 2% higher than the conventional method.