Effects of macromodeling on the simulation of transient events caused by direct lightning to overhead power lines

This paper aims at assessing the relevance of the coupling effects among the main components of overhead power lines in their lightning response, namely, tower, grounding electrodes, and shield wire(s). Mutual coupling effects are investigated by simulation, using an electromagnetic model. The analyses are performed in the frequency and time domain, by considering, respectively, the input impedance at the node of current injection and the overvoltages rising at the same node. The study is conducted considering different configurations for current excitation and three arrangements of grounding electrodes, with the corresponding soil properties. From the analysis of the results, it appears that the effects of electromagnetic coupling among the considered system components affects only marginally the lightning response of the line, being much less relevant than the effects of the uncertainties on the values of electrical parameters of the local soil. This confirms the validity of the macromodeling approach and denotes that the accuracy of the results is overall dependent on the suitability of models adopted for each component; in particular, the proper representation of the grounding system is proven as essential to the successful prediction of overvoltages at the tower top.