Acoustic Waveguides for Sensing and Locating Electrical Discharges in High Voltage Power Transformers and Other Apparatus

For safety and convenience, ultrasonic corona sensors are mounted on the outer surface of power transformer tanks, and consequently, can only receive ultrasound from internal electrical discharges after attenuation through the oil and tank wall. In order to reduce this attenuation and maximize the detected signal, it was thought that low-loss acoustic waveguides would be helpful as a means to transmit the ultrasonic emissions from internal discharges to an external sensor. To assess the feasibility of this idea, the attenuation and frequency characteristics of several forms of guides were determined by measuring the acoustic emissions from sparks in air and oil.