Lightning transient response of bifurcation structure pylon and its empirical expression with high accuracy

This paper studies the transient responses to a lightning surge terminating on towers with a bifurcation structure and presents new empirical formulas for estimating the respective lightning performance. The multi-stage segmentation is adopted for down-lead modeling, and mutual coupling and parasitic capacitance are considered. By discussing the influence degree of these factors, we propose a simplified down-lead system for formula expression. These formulas are derived from the lattice diagram method, and the original lattice diagram method recommended by CIGRE is also compared. Taking the simulation results as standard, the results derived from the proposed method show a good match with the simulation values, due to the consideration of the down-lead bifurcation configuration. The critical current (I _c) at the full range of front time is obtained, and the errors for the Y-shaped pylon by the new method are much less than that of the CIGRE method when the lightning front time is in the 97.5 % confidence interval. Finally, the Monte Carlo method is employed to verify the superiority of the new empirical formulas.