COMPARATIVE TEST METHOD FOR TRANSMISSION-LINE INSULATION DESIGN FOR POLLUTED AREAS.

This paper presents a new test method for comparing contaminated insulators for which field performance data is not available with insulators having a known field performance. The comparison is based on the laboratory performance of a test insulator chain and a reference chain. The contaminated test and reference specimens are installed in a fog chamber, energized in parallel and exposed to equal wetting. The ratio of the number of times when only the insulator chain with the new type of insulators flashes over to the number of times when both insulator chains flash over, offers a direct quantitative comparison between the two chains. In addition, good agreement was found between the results of the comparative test method in the laboratory and long-term field-test data. Finally the application of the newly developed test method to transmission-line insulation design is presented together with results of tests on different types of insulators.