Dynamic Simulation of Lightning Attachment to Earthed Overhead Transmission Line Structures

In this paper a novel method is presented to investigate lightning stroke attachment to earthed overhead transmission line structures. This method is based on the dynamic simulation of lightning downward leader movement toward the ground in three dimensions. To perform the simulation, a three-dimensional model for clouds, towers, wires, and a perfectly conducting ground is created. A stepping approach is also introduced in accordance with the field observations of negative downward lightning leaders to model the downward leader movement toward the ground. In each step of the leader movement, the electric field is computed numerically in all points of the simulation space and in three dimensions. Meanwhile, stable positive upward leader inception from some test points on earthed structures is tracked by means of an adopted precise model of the leader—streamer system to find the ultimate striking point. The main computational volume is occupied by an electric field calculation, which is performed using the charge simulation method. A direct movement model for the downward leader is also simulated and compared with the stepping approach. The percentage of strokes that attach to the phase wires, ground wires, and towers is extracted using this method. The maximum return stroke current for the strokes that attach to the phase wires is also computed by this dynamic simulation and is compared with the traditional methods that are available for transmission line lightning performance investigation.