Which condition increases the likelihood of flashover in polluted environments?

• A. Very low humidity
• B. Vacuum
• C. High humidity
• D. Very low temperature

Answer: (C)

Moisture turning polluted insulator surfaces into conductive paths is the key factor. In polluted environments, contaminants form a film that becomes highly conductive when humidity is high because water dissolves salts and creates an electrolyte. This lowers the surface resistance and increases leakage current along the surface, allowing an arc to jump across the insulator at a lower voltage. Dry conditions keep the film less conductive, so flashover is less likely; vacuum and very low temperature don’t promote the same surface conduction. Therefore, high humidity raises the likelihood of flashover in polluted environments.