Effect of pollution distribution class on insulators flashover under AC voltage

The aim of this paper concerns the effect of pollution distribution class on insulators flashover under AC voltage. It results from the first category that the flashover voltage for the case of polluted insulators with non-uniform transversal distribution is higher by 21% compared with that obtained by uniform contamination. The peak flashover voltage of an insulating surface under periodic longitudinal pollution distribution is at maximum 30% lower than that obtained in the same isolation in the case of a uniform contamination. The third category showed the existence of a minimum alternating voltage. This is estimated at 42% of that found in the case where the tested insulators are uniformly polluted. The visualization of the electrical phenomenon showed that the minimum threshold voltage can be attributed to a maximum shortening of the lightly polluted portion of the insulator creepage distance before complete flashover. The separation of the electric precursor arc from the surface of the lightly polluted area of the tested insulator can be explained by the dominance of the repulsion thermal force over the adhesion electromagnetic force of the arc on the contaminated surface of the insulator.