Effect of pollution distribution class on insulators flashover under AC voltage

• We examine the insulator pollution performance as a function of AC flashover current.
• Transversal, periodic longitudinal and non-periodic longitudinal distributions are studied.
• In case 1, the flashover voltage is 21% higher than that under uniform distribution.
• In case 2, the flashover voltage is 30% lower than that under uniform distribution.
• In case 3, the flashover voltage is 42% lower than that under uniform distribution.

The aim of this paper concerns the effect of pollution distribution class on insulators flashover under AC voltage. Three scenarios of non-uniform pollution distribution were studied: transversal, longitudinal periodic and longitudinal non-periodic. These scenarios are commonly seen in the field with in-service insulators located near polluting sources and at sites with prevailing winds.In the first scenario, the flashover voltage of polluted insulators under non-uniform transversal distribution is 21% higher than that under uniform contamination. In such a case, the insulator can withstand the voltage stresses much better than under uniform contamination conditions. The flashover voltage of an insulating surface under periodic longitudinal pollution distribution is at maximum 30% lower than that obtained in the same insulation in the case of a uniform contamination. The third scenario has shown the existence of a minimum flashover voltage which is 42% lower than that obtained in a uniform distribution. Laboratory tests revealed that the minimum flashover voltage can be attributed to the maximum shortening of the weakly polluted creepage distance of the insulator before its full flashover. In a so unfavorable situation, it will be necessary either to proceed to a re-dimensioning of the insulation based on their performance under non-uniform contamination or take preventive measures of pollution control of the insulators.