Deteriorated parts of insulator stings in high voltage transmission lines can constitute a threat to the safety of power grid. For studying the infrared heating characteristics of deteriorated porcelain insulator

a series of experiments aer set up to study the influence of the deteriorated insulator’s resistance

location along the strings and environmental relative humidity on infrared detection. Moreover

additional experiments are carried out on a string containing two pieces of deteriorated insulators to investigate the different heating phenomena between normal and low-resistance insulators. The heating mechanism of the steel cap in the infrared image is analyzed further by using the finite element analysis simulation. The experimental and simulation results show that the relationship between temperature rise of deteriorated insulator and its impedance is nonlinear

the max rise will be reached when the resistance is 30 MΩ; the deterioration on both ends of the insulator string are easy to be detected; the excessive high relative humidity may lead to incorrect detection; the heating area of normal insulator is at the lower part of its steel-cap and temperature of its porcelain rises by approximately 1.2 ℃. As for deteriorated insulators

the temperature rise along its steel-cap is evenly distributed

and its porcelain remains almost the same temperature as being tested before. The related study results have provided a reference for the infrared detection of deteriorated insulators.