The effect of inserting two clean discs in a polluted 275 kV AC string: an experimental investigation

This paper investigates the effect of a nonuniform distribution of a conductive surface layer along the length of a 275 kV cap and pin insulator string. The worst case is when one or two clean discs are inserted in a polluted string. A high electric field then exists across the clean discs, distorting the field to such an extent that localised flashover occurs across the clean discs.