Influence of Shed Profile on the Pollution Performance of Porcelain Insulators

Over the years, pollution performance of insulators have become synonymous with the creepage distance of the insulators. Accordingly, the utility specifications insist the requirement of creepage distance as an important parameter when specifying insulator requirements. This has led to a belief that the increase in creepage by default guarantees improved pollution performance of insulators. Though this is true to an extent, the underlying factors that actually lead to this improved performance have not been fully studied and understood. However, the IEC standards pertaining to selection & dimensioning of insulators specify certain key parameters that influence the pollution performance of the insulators under different service conditions. This paper attempts to elaborate on the various parameters of shed profile and their impact in determining the pollution performance of porcelain insulators. The influence of the s/p ratio in particular has been analyzed in detail and the results of artificial pollution testing are reported.