When the arc deterioration is discussed、includingmelting，decomposition and evaporation of the electricalinsulating materials，it is considered to be related tothe temperature rise on the insulator surface due to thearc. Eventually， it is considered that the appraisal ofarc resistance of electrical insulating materials is decidedfrom the point of heat-proof of insulator surfaceto the arc.From these points of view，the appraisal coefficientof arc resistance m characterized the properties to theare over the insulating material was defined and the appraisalof are resistance were done in the use of m.This coefficient is a function of the thermophysical materialcharacteristics and is independent of the dischargeparameters and dimensions of the test device.In short， the appraisal of arc resistance is possibleonly by obtaining the thermophysical properties of insulatingmaterials.It should be noted that this proposed criterion is obtainedfrom the absence of phase transformations in thematerial， which transformations cannot be allowed.
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