Identification of striking distance considering the velocity ratio and competition among the leaders

The striking distance is an important parameter to design a reliable lightning protection system. To protect an object against direct strikes, an improved leader progression model combined fractal geometry and the leader initiation criteria proposed by M. Becerra is introduced to determine the striking distance on a given structure. Both the deterministic and stochastic features of the lightning leader are considered and more detailed three-dimensional numerical simulation of the leader discharge is achieved due to the application of extended grid. Some of the basic methods and strategies are outlined and the influence on protection zone caused by leader velocity ratio is analyzed. Moreover, a comparative analysis of the results obtained through the improved model, the rolling sphere method and the Cooray model is performed. The results indicate that the presented method is closer to the natural lightning and the selection of the breakdown point is actually a complex competitive process among numerous upward leaders.