An interpretation of arc and track resistance test methods by the power density concept

Electrical insulation used in circuit breakers and various switching devices may be subjected to periodic arcing in the vicinity of moving contacts. Other insulating components are frequently under voltage stress and become susceptible to surface tracking when surface contaminants are present. It has been necessary for the insulation engineer to develop test methods for evaluating the arc and track resistance of electrical insulating materials so that these materials can be properly applied. The resulting test methods have differed depending upon the nature of the intended application, the philosophy of the investigator, apparatus cost limitations and the general desire for universal acceptability. Experience has shown that only a limited amount of correlation can be found between test results obtained from any two or more test methods described in this paper. It has been observed that such factors as arc intensity, electrode configuration and spacing, and arcing time greatly affect the test results. In an effort to create a better understanding of the correlation or lack of correlation between test results from the various arc and track resistance tests, the “power density concept” was postulated by L. Mandclcorn¹.