The crack under flange is the key factor inducing insulator fracture. This work introduces the pulsed thermography (PT) to detect the surface cracks of porcelain insulator hidden under the flange. A pulsed thermography system with darkroom and fast infrared camera was designed and built. The effectiveness of the method was demonstrated by the experiment of artificial samples. The thermal response was determined as the radiation difference between the defect area and defect-free area. Feature images were obtained according to the time point of the maximum thermal response. It is verified that the maximum metal layer depth applied by this method is 4-6mm under the temperature resolution of 18mK. The time domain feature images obtained by detection were optimized by Lucy-Richardson literation to improve the visual effect, so that the narrow defects and defect boundaries could be more accurately distinguished.

Porcelain Insulator,Cracks Detection,Pulsed Thermography,Lucy-Richardson Iteration,diameter depth ratio