A Predictive Model of Negative Lightning Discharge and Return Stroke
Résumé
The prediction of the parameters characterising the negative lightning discharge and the return stroke is of a great interest for the protection of populations and structures in temperate regions where most cloud to ground lightning discharges (80 to 90% of lightning shots) are of negative polarity. Disposing of a model enabling to predict the impact points and the distance of striking down by lightning should permit to prevent the dangerous effects on engineering systems. Contrary to the positive lightning for which many theoretical models are available, researches to derive models for the negative lightning are still at their earlier stages, due to the complexity of the mechanisms involved in the negative lightning propagation process. This contribution is in the continuity of our previous work related to the positive long discharge in air gaps and positive lightning. A self-consistent dynamic model of negative lightning discharge taking into account the different phases of the propagation (i.e., the initiation of the first corona, the negative and space leaders and the junction of leaders) and return stroke is presented. This model uses LCR line electrical network parameters derived from electromagnetic field, physical laws and gas discharge theories. It enables to determine the main macroscopic parameters of the negative discharge (current and corresponding charge, propagation velocities, potential drop along its channel, power and energy injected into the gap and a trajectory of the discharge plotted in 3D in real time obtained from a probabilistic distribution) and the associated return stroke (current and charge, velocity ...). Different cloud – ground distances are considered. The computed results are discussed with respects to the experimental data reported in the literature.