Nondestructive Testing of Porcelain Post Insulators Using Active Infrared Thermography

In recent years, accidents of porcelain post insulators fracture due to their internal defects often occur, which severely endanger the security and stability of the power system. The traditional ultrasonic testing method requires power off, and the effect and efficiency are barely satisfactory. In this study, a novel approach based on active infrared thermography is proposed to test and evaluate the state of porcelain post insulators. More specifically, an external source of energy is employed to heat the specimen being detected and the thermal front propagates through the object. Due to different thermal properties between defective and sound area, the thermal contrast evolution on the surface of the object can be monitored by a thermographic camera. The recorded data are analyzed by image processing technology to yield information about defect size and depth. The validity of the proposed testing method is proved by a series of experiments performed on specimens containing defects of different sizes at different depths. It is concluded that the active infrared thermography testing method is attractive owing to its quick, contactless, full-field imaging and quantitative defect estimation capabilities.