Pulsed infrared thermography to inspect the internal defects of composite insulators

A non-destructive testing method for internal defects detection is desperately needed due to wide and increasing application of composite insulators in the power grid. In this study, a novel approach based on pulsed infrared thermography was investigated with the aim of testing and evaluating the state of composite insulators. In pulsed infrared thermography, an external source of energy is required to induce a temperature difference between defective and nondefective areas in the specimen under examination. The thermal changes can be detected with an infrared camera and recorded for later analysis. The recorded data is analyzed by images sequence processing technology to yield information for the recognition quantification of internal defects. Preliminary study based on experimental tests in laboratory concerning the detection of plate specimen with flat-bottom holes was conducted. The validity of the proposed testing method is proved with a series of experiments performed on specimens containing defects of different sizes at different depths. It is concluded that pulsed infrared thermography is attractive and promising for detecting internal defects of composite insulators because of its rapid, contactless, remote imaging and quantitative defect estimation capabilities.