Polymeric additions to HV conductors: some discharge effects

On traditional HV overhead lines, the fittings attached to the live conductors, such as spacers, have been largely metallic. The modern tendency, however, is to use polymeric additions, not only as spacers but also as aerodynamic spoilers, bird-flight diverters and bale hangers. It has long been realised that metallic fittings may cause stress concentrations and hence discharges, if they have sharply curved projections. Polymeric additions are known to reduce this phenomenon to some degree. The work described by the authors is aimed at measuring the scale of this effect and giving some guidance to designers on likely levels of stress for the inception of visual discharges