The national utility (Originally Eskom), had undertaken comprehensive evaluation of coating materials over a number of years at their Koeberg Insulator Pollution Testing Station. Situated on the west coast of the South Africa, the various energized samples are exposed to the extreme marine conditions characteristic of the site. Physical degradation, leakage current amplitudes and flashover occurrence are closely monitored. As an example of the results achieved at this facility, Figure 1 shows the relative cumulative leakage current flow on three identical insulators – two of which are coated with different brands of silicone rubber and the third left un-coated. It is evident that the silicone rubber significantly improves the insulator performance and, further, that the extent of the improvement is dependent on the type of rubber used.
The performance of a porcelain insulator coated with CharCoat IC compared to dimensionally identical units but of different materials, is illustrated in Figure 2. It is interesting to note that the leakage currents on the coated porcelain are significantly less than even the silicone rubber composite unit. This is not only due to the excellent hydrophobicity and hydrophobicity transfer rate of CharCoat IC but also the more efficient thermal transfer possible through the coating layer to the ceramic substrate.
*Originally Tested as Insilcote HV2000