Influence of water and defects on abnormal temperature rise of composite insulator

• In this paper, the influnce of both water and defects on the abnormal temperature rise of composite insulator is studied. • The grating detection system for the temperature rise of composite insulator’s surface is set up. And the temperature rise of composite insulator before, after water immersion, and after water immersion and drying are accurately measured. • The internal defects of composite insulator are clearly detected by the phased array ultrasonic testing system. And the phased array ultrasonic recognition model for internal defects of insulator is proposed. • The transverse anatomical test of composite insulator is carried out to verify the results of the temperature rise test and the phased array ultrasonic testing test. Water and defects of composite insulator may cause its abnormal temperature rise, which seriously affects the safety of power grid. In this paper, the temperature rise tests of a 110 kV composite insulator before, after water immersion, and after water immersion and drying are firstly carried out. Then a phased array ultrasonic detector is used to detect the internal defects of the insulator. And the phased array ultrasonic recognition model for internal defects is proposed. Finally, the transverse anatomical test is carried out to verify the defects of composite insulator obtained by the temperature rise test and the phased array ultrasonic testing test. The results show that the temperature rise of composite insulator after water immersion is higher than that before water immersion. The maximum temperature rise of the insulator after water immersion is 1.2 ℃. And there is no temperature rise after drying. The defect between the sheath and the core rod at the temperature rise position after immersion is detected by the phased array ultrasonic testing. Cracks and discharge defects are observed anatomically. The accuracy of identification model is proved. And it provides an effective method for nondestructive detection of internal defects of composite insulator in the laboratory. According to the results of temperature rise test, ultrasonic detection and anatomical test, the high water content of the composite insulator sheath is one of the reasons for the slight temperature rise of the insulator. And water and defects are the direct reasons for the obvious temperature rise of composite insulator.