Earth heterogeneity effects on the buried cable vulnerability to lightning

The authors analyze the effect of the earth heterogeneity on the surges induced within buried cables by a nearby lightning discharge. A general formulation for the lightning induced electromagnetic fields in a multilayer Earth is developed in frequency domain by using a monopole technique. This technique is performed by the use of the so called modified transmission line model. Furthermore some numerical examples are given to illustrate the effect of the Earth structure on the severity of the impact of lightning on buried lines. This analysis is performed on the basis of the variation of the peak value of the electromagnetic fields induced along the cable outer conductor