Infrared temperature measurement is one of the important approaches to online detection of insulator operation status. In this study

the heat generation mechanism of an insulator and the principle of infrared thermal imagining were analyzed. Experiments of infrared temperature measurement were conducted for the porcelain insulator strings with a zero insulator at different position of the string

and for the polluted and clean strings. The results indicate that: 1the thermogram contains catastrophe as pollution or zero insulator exists; 2in the thermogram

the average temperature difference between the zero insulator and the adjacent insulator reaches its maximum when the zero insulator locates near the high voltage side

the average temperature difference reaches its minimum when the zero insulator locates in the middle part

and it is between the maximum and minimum when the zero insulator locates near the low voltage side. Therefore

zero insulator and polluted insulator can be identified rapidly by high accuracy infrared thermal imaging system based on infrared temperature measurement technology.