Detection of Internal Defects of Full-Size Composite Insulators Based on Microwave Technique

In this article, a detection method based on microwave technique is proposed to detect the internal defects of composite insulators. Based on this method, an automatic detection system is developed for full-size composite insulator. In the experiments with 110-kV composite insulators, three types of defects, namely the air-gap defect, carbonization defect, and conductive defect, are artificially made, and they are located exactly by the developed automatic defect detection system. It is found that, due to the dielectric constant and magnetic permeability properties, the conductive defect can be detected easily, whereas the carbonization defect is the most difficult one to be detected among all three defects. In addition, a real defective 500-kV composite insulator from transmission line after years of operation is also detected by the developed system and the results are consistent with the infrared imaging method. According to the test results, the developed system is efficient, labor-saving, and robust. It can have a great potential in the quality control of composite insulators.