A simplified method for the risk analysis of protection against lightning. Theory and a case study

Lightning strikes can cause physical harm to people and damage inside commercial, industrial and residential structures. The risk of damage from lightning depends on the dimensional and environmental characteristics of the structure, the number of people and their permanence in the structure, their reaction to a possible fire as well as the density of lightning strikes to the ground in the structure location. The assessment of the prospected risk determines the need for protective measures if it is higher than the tolerable value. The standard IEC/EN 62305-2 proposes a method to calculate the probable average annual loss in a structure due to lightning flashes. Since the standard is oriented towards analyzing the greatest number of types of structures, the analysis is complex and laborious due to the multitude of parameters to be used. The aim of this paper is to facilitate an easy understanding of the basic parameters to consider and to introduce an analysis aimed at typical cases of buildings in urban environments in order to simplify the IEC/EN method; it is introduced an effective parameter, the risk value in per unit related to the tolerable risk. The application of the suggested simplified formulas to real cases have provided results that coincide absolutely with the values calculated by applying the IEC/EN formulas.