An Ultrasonic Phased Array Method for Detecting the Internal Defects in Composite Insulators by Using the Concave Probe

The internal defects in composite insulators, for example void, delamination, and interface debonding, can lead to partial discharge, flashover, and even result in cracking and breakdown, threatening the safe operation of power system. In this study, various defects were artificially made in the 10 kV composite insulators. The ultrasonic phased array method was employed to detect these defects, by using a concave probe designed to ensure complete coupling between the probe detection surface and the curved insulator surface. The results show that these artificial defects can be detected through the detection ultrasonic images. Moreover, compared to previous studies, a smaller through-hole (0.3 mm diameter) in the housing and a smaller through-hole (0.5 mm diameter) in the core can be successfully detected. Additionally, the depths of defects can be determined from the detection images, and the deviations in depth for the defects were less than 9.3%. Moreover, the resolution for detecting the through-holes in the housing is enhanced.