Detection of Carbonization Defects in Composite Insulated Cross-Arms Using Active Microwave Thermography

Composites are widely used in composite insulation cross-arms because of their excellent electrical, mechanical, and aging resistance properties. Due to its long-term operation in the outdoor environment, the composite interface is prone to carbonization defects under high voltage and force. In this study, the active microwave thermography (AMT) combined with a feature extraction algorithm is used to separate the areas corresponding to different physical processes of the defects inside the composites. The principles of microwave heating, thermal diffusion, and thermal feature division are investigated, and the thermophysical processes in the active microwave thermal imaging process are described. Furthermore, the method's effectiveness for defect feature extraction and thermal feature division is verified by conducting tests on bonded panels with artificial interfacial defects, and different feature extraction algorithms are quantitatively compared. The result shows that AMT can provide an effective way to detect internal carbonization defects in composites.