Ultrasonic detection of electric discharges

AT PRESENT the methods used to detect failures during factory tests of electrical apparatus are of sufficient sensitivity to detect all real faults that occur. However, these methods sometimes do not supply sufficient information for laboratory research and developmental tests of coil stacks and other types of insulation structures. In addition, the present methods have certain other disadvantages such as insensitivity to small corona discharges, sensitivity to high-capacitance charging currents and external circuit sparking, and no positive indication of the discharge location.