Interfacial Defect Detection of Three-Layer Structure in Composite Cross-Arms Using Active Infrared Thermography

With the development of transmission lines, composite cross-arms have become an integral part owing to their excellent insulation properties. In the process of its operation, composite cross-arms are prone to interface problems under the action of the force generated by the conductor, which can cause grid accidents. Active infrared thermography (AIT) is able to identify faults in composite materials by actively applying thermal excitation. In this work, the heat diffusion and temperature distribution of the three-layer structure of composite cross-arms are investigated using finite element simulation under continuous pulse or chirp thermal excitation. The temperature variation characteristics of different interface defects were compared. Under the effect of continuous pulse excitation, the defects can be detected by the temperature change at the defective and defect-free areas during the cooling process. As for the chirp thermal excitation, the defects can be identified by the temperature change at the peak and trough of the temperature rise process. The study shows that active infrared thermography can detect the interface defects in the composite cross-arms of the three-layer structure, laying the foundation for the actual defect detection.