27.10.14 ,
Our company got an interesting question: is it possible to use the cross on the dome of the church as a lightning rod? We are answering this question!
This question can be solved by referring to the "Instructions for lightning protection of buildings, structures and industrial communications" of the industry standard 153-34.21.122-2003.
Paragraph 3.2.1.2 describes the conditions of using building structural elements as natural lightning rods. These elements' parameters must meet the requirements placed to conventional lightning rods.
First of all, the material of the cross must be a current-carrying conductor; it can only be metal in the conditions of modern technological solutions. Consequently, modern crosses made of fiberglass and old ones of wood can not be considered for lightning protection purposes. Crosses of stainless and structural steel should comply with the minimum sizes and cross- sections. Thickness of the steel wall should not be less than 2.5 mm, and the total cross-section must be at least 50 mm2. For stainless steel the indexes are a bit lower: wall thickness - 2 mm, cross section - 50 mm2. Size data are taken according to GOST R IEC 62561.2-2014.
For the organization of a complete external lightning protection system, it is necessary to make down conductors to the grounding device from crosses or metal structures on which they are installed.
In addition, it is necessary to check if the entire volume of the building is protected by such a natural lightning rod and if installation of additional conventional lightning rods is required.
Useful links:
- External lightning protection
- Webinar series about grounding and lightning protection with Professor E.M.Bazelyan
- Lightning protection grounding
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