Wet tracking and erosion evaluation of non-ceramic insulation for outdoor use

This paper is a further report on a continuing project at the Westinghouse R&D Laboratory. Studies of insulation surface conduction and tracking at this laboratory using small specimens, a fog chamber, etc. had been proceeding for more than two decades prior to the initiation in 1965 of an outdoor testing rack at the R&D Center, which is in the Pittsburgh area. Experience with various tracking tests1 including the Dust and Fog Test (ASTM D2132) and modifications thereof which were initiated at Westinghouse, the Differential Wet Tracking Test (ASTM D2302), which was developed at Westinghouse R&D, and the Liquid-Contaminant Inclined Plane Tracking and Erosion Test (ASTM D2303) which was developed at the General Electric Co. Laboratories. All were extensively tried on many resin materials, particularly mineral filled epoxy resins. These tests indicated that there were a number of materials which were essentially nontracking under the most severe levels of each test.