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Laboratory tests were conducted to determine the dc flashover characteristics of clean, artificially, and naturally contaminated transmission line suspension insulators. Direct current flashover of clean and contaminated insulators in the fog chamber is a linear function of string length up to 350 kV. Comparative data are presented on a number of specimens for clean-wet and contaminated insulators in the fog chamber. BPA's fog chamber tests on artificially contaminated insulators are equivalent to severe natural contamination.
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Scarborough et al. (1967) studied this question.
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