Assessment of lightning induced voltages in buried cables for SPD implementation

The transient behavior of a cable, such as a communication line, entering a building subjected to a lightning stroke is investigated using the electromagnetic field theory approach. The field theory method used is essentially an extension of antenna theory to low frequencies. The computation of transient voltages is carried out using the MultiFields software package. The article focuses on the transient induced voltages at the boundary of two different lightning protection zones as required by the IEC 62305-3 standard. The main objective is to provide a computational analysis for the Surge Protection Device (SPD) implementation regarding the lightning equipotential bonding. Induced voltages are computed as well as the electric field in the air gap between the cable and the reinforcement rebar. SPDs and air break down voltages cause-effects are discussed briefly. Influences of several parameters are studied. Different waveforms with various peak values of current surges are examined. In this paper, authors demonstrate the importance of some parameters on the analysis of the transient ground potential rises to the lightning stroke for sparking risks prevention. Time domain results are shown as static 2D plots.