Optimized design for insulator pollution performance, an easy to use method free of conventional limitations

Abstract

Designing insulators for high or modest contamination is complicated and object for simplification in order to make design and production easier. The limitations of creepage distance, CD, as design base has become recognized. Exaggerated with excesses in material and production, or insufficient with risk of failure in service, the end result is unavoidably increased total cost. The obvious restriction is that CD considers distance. The conductivity of a surface is, apart from the specific surface conductivity, dependent only on surface shape. Referred to as form factor when measuring test results and K-value, Kv, when used for design, this parameter describes the shape exactly and is the true design base. The problem is that Kv is mathematically complicated. Software development has enhanced CAE programs and solved this problem. But these programs are custom made and not readily accessible. Herein we present a method to determine insulators Kv in a manual but convenient way with acceptable results, valid for all insulator materials and processes. Examples are presented and evaluated for CD and Kv comparison. General conclusion is that replacing CD with Kv, while maintaining all other design parameters, will result in simultaneous cost and performance improvements.