The defect detection of GIS spacer based on frequency-domain ultrasonic method

The high sensitivity defect detection technology is urgently needed for health condition assessment of the operating GIS spacers. In this study, we propose the sweeping frequency ultrasonic method to detect the defect of GIS spacers. A three-dimensional simulation model considering the spacer with and without metal shield is established. Two kinds of piezoelectric transducer are used as the emitting and receiving probe respectively, located opposite to each other on the enclosure of the GIS. The sweeping frequency signal is energized on the surface of the emitting piezoelectric transducer. The ultrasonic wave propagation characteristic on spacers with metallic particle and crack defects are obtained. The results reveal that the ultrasonic wave propagates through the spacer directly to reach the receiving transducer. The received time-domain ultrasonic wave magnitude is higher on defective spacer than that on raw spacer, but still hard to be taken as the evaluate the heath condition of the spacer. The obtained frequency-domain signal differs obviously, where the main frequency of the raw spacer, the spacer with metallic particle and the spacer with crack is about 101kHz (103kHz without metal shield), 40kHz (56kHz without metal shield) and 46kHz (30kHz without metal shield). It is hoped this study could inspire novel idea on online detection of GIS spacers.