Interface defect detection for composite insulators based on infrared thermography axial temperature method

Interface quality is one of the most important properties of composite insulators, and is hard to be effectively detected. Poor interface quality may lead to interface discharge or insulator fracture and hence threatens the safety of power systems. In order to detect interface defects of in-service composite insulators, 15 samples were collected from transmission lines in this paper. The dry power frequency voltage test and the steep-front impulse voltage test were conducted. The surface temperature after dry power frequency voltage test was recorded by infrared thermography. Then a method for quantitative characterization of composite insulator interface defects based on infrared thermal image axial temperature was proposed. By defining heating section according to temperature level of each sample, we summarized temperature distribution characteristics, including characteristics on location, length and maximum temperature point of heating sections. Our results show that the connection zone of composite insulators is prone to generate interface defects. Temperature analysis together with steep-front impulse voltage test results indicate that interface defects of test samples can be judged by the following three features of heating sections, namely, temperature rise (ΔT) above 80 K, ΔT above 20 K with 10 cm in length, and ΔT above 10 K with 40 cm in length.