Ultrasonic Detection and Location of Electric Discharges in Insulating Structures [includes discussion]

This paper describes a simple method for detecting and locating impulse and low-frequency corona, and breakdowns in some types of insulating structures and apparatus. Essentially, it is an adaptation of sonar techniques of triangulation and ranging. For impulse, it is applicable to steep-front and chopped-wave tests as well as full-wave tests. It is capable of locating corona or failures in many cases with accuracy. It is useful primarily for laboratory techniques or applications where ambient background and specimen magnetostriction noises are either known or can be controlled carefully. Its use during factory impulse tests of transformers is limited because of the ultrasonic-magnetostriction noise, which is developed in the core during the voltage application.