Detection of Small Defects in Composite Insulators Using Terahertz Technique and Deconvolution Method

After a long-term operation, defects may occur in composite insulators and threat the safe operation of power transmission. To secure the power transmission system, it would be beneficial to detect the defects in their initial stage. In this article, the terahertz technique combined with a deconvolution method was proposed, and a terahertz time-domain spectroscopy system was built. To validate the method proposed, three types of defects, namely, single air gap defect, inclusion defect, and double-layer air gap defect were artificially prepared and tested. According to the test results, it was found that compared with the traditional terahertz method, the air gap size that could lead to pulse overlapping was reduced from 1.22 to 0.57 mm. After the deconvolution process, air gap defect as small as 0.173 mm could be distinguished due to the shape characteristics of unipolar pulse. It was also found that when the defect was damp, the obtained waveform near the defect became smooth. The results of this article demonstrate that terahertz time-domain spectroscopy (THz-TDS), combined with the deconvolution method, can have high potential in the detection of defects in composite insulators.