The mesh method in lightning protection analyzed from a lightning attachment model

Based on the well-known rolling sphere method, international standards recommend the location of the external lightning protection system of structures. The design of the external lightning protection system of structures of height of less than 60 m can be done by installing a mesh on top of a roof of the structure or by creating a mesh with wires at certain distance from the roof of the structure. The prospective downward leader current that the mesh can incept depends on the size of the mesh and the current magnitude is given as recommendation in the international standards. This paper analyses the relation prospective negative downward leader current vs. mesh size from a lightning attachment model. The model is applied to a perfectly grounded structure with maximum height of 50 m protected by two different external lightning protection systems recommended by the international standards. The results showed difference on magnitude of the prospective downward leader current the standards recommend and the ones obtained using the lightning attachment model for meshes of shorter size. Discrepancies concerning the minimum downward leader current that can be incepted by a mesh made by wires located at certain distance from the ground structure and a mesh located on top of the building are obtained.