A laboratory test for tracking and erosion resistance of HV outdoor insulation

A new laboratory test for evaluating the tracking and erosion performance of HV outdoor polymeric insulating materials is described. The materials evaluated include various formulations of HTV (high temperature vulcanized) silicone rubber and polyolefin polymers. The test is based on combining some features of the ASTM D2132 DF (dust and fog) test and the ASTM D2303 IP (inclined plane) test. The new test employs IP test geometry, IP test equipment, and IP specimen plaques. The plaque is coated with a mixture of clay and salt similar to the contaminant of the DF test and identical to the contaminant used in the IEC dean fog test to rate ceramic insulators for use in contaminated environments. A liquid contaminant with a conductivity similar to that of the DF test is applied to the test specimen in the same way as in the IP test. Data collected from the field on the maximum concentration of insoluble and soluble ionic materials on surfaces of contaminated insulators which have been for 21 years in contaminated regions, provide a basis for choosing the minimum concentration of the solid contaminant to apply to the specimens. This choice also serves to define, at least tentatively, the geographical area where the results of this test have significance. It is expected that this test could be used also for screening materials and obtaining a relative ranking of the tracking and erosion resistance of various materials. Measurements of the leakage current via a computerized data acquisition system, and the discharge activity with a high speed camera were performed, and have resulted in a better understanding of the onset of material degradation.