A Comparison of Contamination Test Methods for DC Line Insulators

The performance of insulators under contaminated conditions is a main parameter on the cost of dc lines. A study was made to find a meaningful way to rank in the laboratory various shapes of insulators. Three basic methods were compared, the first two having a uniform contamination, while the third method features non-uniform dust contamination sprayed on energized insulators. The importance of some test parameters of the third method, such as the humidification duration, are shown to have a great influence on the ranking of various shapes. It is also shown that the type of measurements and the interpretation of the results, lead to different rankings. For any given method, the shape of the insulators has a large influence; for a given flashover ver voltage the length of the most effict insulator is about half of the length of the worst with the same leakage distance.