Ultrasonic imaging of electrical trees in organic insulating materials

In this paper, we report that the contour plot or the projection plot of a ball-(or "Broccoli"-) and a bush-type tree in polyethylene can be obtained by mechanically scanning the ultrasonic transducer over the sample and by subsequent processing of the ultrasonic signals reflected from the treeing region. The images of such types of trees were found to coincide with those obtained by an optical method.