Wang, Pei, Yanyan Bao, Yongliang Yao, Yueyi Wang, Pin Jiang, Yushuo Wu, Pengzhen Wu, and Shuaibing Li. "THz Non-Destructive Testing Method for Internal Moisture Defects in Composite Insulators." IEEE Access 14 (2026): 7204-7216.
ABSTRACT
The presence of internal moisture defects at the interface between the core rod and skirt has been identified as a primary factor contributing to the failure of composite insulators. However, effective detection methods for such defects remain to be fully developed. In order to address this issue, the present paper puts forward a non-destructive testing method based on terahertz technology. Firstly, composite insulator samples containing moisture defects were fabricated in order to simulate real-world defects. Subsequent experimental testing yielded the terahertz time-domain/frequency-domain characteristics and imaging features of different samples. The optical parameters of the defective samples were extracted using an extended fourth-order Dedye model. The particle swarm optimization (PSO) method was then employed to overcome the limitations of traditional nonlinear fitting methods in dispersion models. Finally, based on the fitted parameters, time-domain finite-difference time-domain (FDTD) simulations were performed to invert the internal moisture defects within composite insulators in the terahertz frequency band, thus validating the accuracy of the experimental results. The findings demonstrate that the simulation inversion results align with actual test data, thus confirming that terahertz time/frequency domain parameters can effectively characterize internal moisture defects in composite insulators. The time-frequency domain characteristics facilitate qualitative analysis of defect occurrence and quantitative calculation of defect thickness. When combined with terahertz imaging results, this approach facilitates rapid determination of the location and geometric dimensions of moisture defects. Consequently, it achieves non-destructive testing of internal moisture defects in composite insulators, ensuring operational reliability and providing technical support for their safe and stable operation.
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