Estimation of Lightning Incidence to Overhead Transmission Lines

Abstract

General expressions for the estimation of lightning incidence to overhead transmission lines on the basis of electrogeometric and generic models are introduced, which consider, besides transmission-line geometry, lightning crest current distribution and, based on the recently proposed statistical model, interception probability distribution. An application to typical 115 kV up to 765 kV and large scale 500 kV and UHV overhead transmission lines is performed and the computed results, varying significantly among lightning attachment models, are validated through comparisons with field data from literature; the IEEE Std 1243 overestimates significantly lightning incidence to shield wires of large scale transmission lines. The expected annual number of lightning strikes to shield wires of transmission lines depends on lightning crest current distribution; this dependence, easily quantified with the aid of the introduced general expressions, is not considered by the relevant IEEE standard. Lightning incidence results are discussed in the context of the backflashover rate of overhead transmission lines.