Electric fields along a post insulator: AC-measurements and calculations

Knowledge of the electric field distribution can deepen the understanding of the flashover behaviour of outdoor insulators. The AC electric field under dry conditions and during rain has been measured along a post insulator with a field probe. Corona activity from the flange carries the potential towards the boundary of the corona region: the `electrical geometry´ of the insulator is modified. The experimental results agree with field calculations based on this modified `electrical geometry´. UV photography supports the findings of the field measurements