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, and 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 toward analyzing the greatest number of types of structures, the analysis is complex and laborious because of the multitude of parameters to be used. The aim of this article 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 to simplify the International Electrotechnical Commission (IEC)/EN method. We introduce an effective parameter: the per unit (p.u.) risk value related to the tolerable risk. The applications of the suggested simplified formulas to real cases have provided results that absolutely coincide with the values calculated by applying the IEC/EN formulas. Table 1 list the symbols used in this article.