Thermal response of coated steel conductors under surge currents taking the skin effect into account

A previous paper (Maksiejewski, 1993) discussed the assessment of the lightning response of bimetallic cylindrical conductors. The author shows that the considerations for bimetallic conductors cannot be applied fully for conductors with very thin outer layers, as in the case of coated conductors. The specific problems connected with the calculations for the coated steel conductors used in lightning protection are described. The results extend the application of the author´s previous paper. The thermal calculations for coated conductors require the phenomenon of thermal diffusion to be taken into account. Zinc coated steel conductors (galvanised steel conductors) of dimensions recommended by the British Standard code of practice as a lightning conductor, i.e. with diameter 8.0 mm, are discussed. The analysis shows that, for a 5% peak current probability level, galvanised steel conductors of this size are more than adequate for protection against negative lightning strokes. However, galvanised steel conductors of the above dimensions are barely adequate for protection against positive lightning strokes