Lightning protection and the physics of discharge

The way of designing protection systems and of evaluating their exposure to lightning has been improved significantly, mainly during the last 50 years, thanks both to studies in the field and to laboratory research into long air gap breakdown. On the basis of the knowledge acquired, various models for lightning exposure evaluation have been developed, based on the description of the different phases of discharge development. The aim of this paper is to analyse three models in the case of negative lightning which is the most common event, especially in the case of structures not particularly high off the ground