On the possible variation of the lightning striking distance as assumed in the IEC lightning protection standard as a function of structure height

• IEC standard utilizes Electro-Geometrical Method (EGM) in designing lightning protection systems of structures.
• EGM neglects the effects of connecting leaders in lightning attachment to structures.
• SLIM is utilized to study how the striking distance and the attractive radius vary as a function of structure height.
• Adhering to the IEC standard gives rise to a conservative design of lightning protection system.
• Collection Volume Method (CVM) exaggerates the attractive radii and compromises the safety in lightning protection.

The effect of structure height on the lightning striking distance is estimated using a lightning strike model that takes into account the effect of connecting leaders. According to the results, the lightning striking distance may differ significantly from the values assumed in the IEC standard for structure heights beyond 30 m. However, for structure heights smaller than about 30 m, the results show that the values assumed by IEC do not differ significantly from the predictions based on a lightning attachment model taking into account the effect of connecting leaders. However, since IEC assumes a smaller striking distance than the ones predicted by the adopted model one can conclude that the safety is not compromised in adhering to the IEC standard. Results obtained from the model are also compared with Collection Volume Method (CVM) and other commonly used lightning attachment models available in the literature. The results show that in the case of CVM the calculated attractive distances are much larger than the ones obtained using the physically based lightning attachment models. This indicates the possibility of compromising the lightning protection procedures when using CVM.