Calculation of lightning-induced overvoltages on urban overhead lines above a lossy ground plane - appraisal of the shielding effect of nearby buildings

This paper presents an analysis of the reduction effect on the amplitude of lightning-induced overvoltages in an overhead line due to nearby buildings. Such an affect can be appraised by means of a finite element method (FEM) model. A method already proposed by the authors, based on the use of weighting functions applied to the static, induction and radiation terms of the expressions of the lightning electromagnetic field for the case of flat, perfectly conducting terrain, is extended to the case of ground with finite conductivity. Such a method allows to avoid the computational effort associated with the use of the FEM model. Moreover, the paper shows the influence of the cross-section dimension and the exterior faces conductivity of the building on the reduction effect. The analysis is presented for different lightning return stroke current waveforms, line-to-stroke location distances, and return stroke velocities.