몰드 변압기 내부 온도 추정을 위한 초음파 전파 특성 분석

According to electrical accident statistics, transformer types account for a large proportion of accidents in high-voltage electrical facilities. Various methods are used to diagnose the condition of electrical facility in on-line(uninterrupted), such as detecting infrared thermal imaging, ultraviolet, and ultrasonic sound. However, it is difficult to detect internal defects in cast-resin transformer because the outside is sealed with epoxy. This problem can be solved by utilizing the characteristics of the transmission, reflection, and propagation speed of ultrasonic waves. This paper proposes a temperature estimation method using ultrasonic waves to detect a small temperature rise in the early stage of internal short at the primary winding. Ultrasonic propagation characteristics according to the thickness and temperature changes of epoxy was obtained through experimentation and analysis.