Effect of Overhead Shielding Wires on the Lightning-Induced Voltages of Multiconductor Lines Above the Lossy Ground

In this paper, we study the effect of overhead shielding wires on the lightning-induced voltages of two typical multiconductor lines configurations at distances from 50 to 1000 m from the lightning channel, considering perfect and lossy ground, respectively, by using the 2-D finite-difference time-domain method and Agrawal field-line coupling model. The results show that the effect of overhead shielding wires on the lightning-induced voltages is closely related to the finite ground conductivity (σ) and the observation distance (d) from the lightning channel. For the ground conductivity ranging from 0.1 to 0.001 S/m, the values of shielding factor (SF) range about from 0.7 to 0.8 for vertical configuration, and range about from 0.6 to 0.7 for horizontal configuration, within distances from 50 to 1000 m from the lightning channel. Also, we have compared the SF values predicted by using Rusck simplified formula with ours in this paper, and it is noted that the Rusck simplified formula underestimates the SF values and the errors may be above 10% under poor ground conductivities of 0.001 S/m when distances larger than 500 m.