This study aims to propose a defect diagnosis method for distribution cable intermediate joints based on microwave reflection. The research focuses on 10 kV cold-shrink-type distribution cable intermediate joints, employing both simulation analysis and experimental methods. Firstly, a microwave defect detection model for intermediate joints is derived. CST simulations are conducted to analyze the variation of the reflection coefficient (S11) under different detection frequencies, defect depths, and defect types. Next, flat plate and real prototype samples of intermediate joints with defects such as insulation scratches, conductive impurities, and moisture ingress are fabricated. A microwave reflection detection platform is established to test the artificially defective samples. Reflection voltage signals corresponding to different defects are obtained. The concept of the relative value of the reflection voltage difference is then introduced, resulting in significant changes in the detection results, which effectively indicate the presence of different defects. Finally, the reflection voltage signals under different defect sizes, silicone rubber thicknesses, detection distances, and detection angles are studied. The results show that this method is capable of detecting defects as small as 2 mm in width and 0.2 mm in depth. The silicone rubber thickness, detection distance, and detection angle significantly affect the detection results. This demonstrates that microwave reflection signals can effectively identify the type and severity of defects within cable intermediate joints, and the method can be extended to detect internal defects in other layered composite insulation structures.
Deng et al. (Mon,) studied this question.
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