Third part of the article "Lightning rods on the roof (lightning protection of the roof)"


Ascertaining of imperfection of lightning protection theory won't make the life of the designers easier.  They need to protect constructions on the roof today. The builders don't have time to wait until the scientific theory is developed. The national regulatory documents do not suppose anything good in fact. Lightning protection mesh is considered to be a panacea from all the diseases. It is put on the roof of almost all buildings, on those with reinforced concrete slabs as well. It is impossible to understand where this practice came from. In any case, it is not reasonable to blame the regulatory documents. Read carfully the "Instructions for lightning protection"  AD 34.21.122-87. Point 2.11 of this instruction states: "Protection from direct lightning strikes of buildings and structures of II category with non-metal roof should be executed by separate or installed on the protected object rod or catenary wire lightning rods..With a pitch of the roof not more than 1:8 lightning protection mesh can be used...". You see, installation of lightning protection mesh is prescribed only to dielectric roofs in order to protect people and equipment on the top level or in the attic. It results in a limitation of the roof pitch, which many people do not understand. Take a look at fig. 4. At a large pitch, the human may get close to the network conductor, which is inacceptable on the conditions of a back flashover.

Fig. 4. Where does lightning protection mesh function

Fig. 4. Where does lightning protection mesh function

It remans to decide if reinforce concrete slab looks like dielectric roof.



E. M. Bazelyan, DEA, professor
Energy Institute named after G.M. Krzyzanowski, Moscow


Read more "4. Multi-electrode lightning protection system"


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