Non-destructive Testing of Internal Defects in composite post insulators Using Microwave Technique

Firstly, this paper presents a novel microwave non-destructive testing technique for internal defects detection in composite post insulators. Secondly, based on the theory of uniform plane wave transmission in media, the propagation process of microwaves in composite post insulators and at the intersection is analyzed. By simplifying the complex structure of composite post insulators into a homogeneous dielectric layer, a mathematical model of the microwave transmission process inside composite post insulators and at the intersection is established. Finally, the microwave inspection platform was built using a vector network analyzer and a waveguide, and the sweeping frequency range was from 2GHz to 24GHz. The time domain and frequency domain waveforms obtained by measuring composite post insulators with different defect sizes and different defect types (air gap, metal, carbonization) were significantly differences, which proves the feasibility of microwave reflection method applied to the detection of internal defects in composite post insulators.