From the series of articles "Lightning protection of residential and public buildings - answers to frequently asked questions in the design".
The standard IS-153-34.21.122-2003 gives no instructions for that. The older document AD 34.21.122-87 classifies residential and office buildings to the last III category of lightning protection and even then in exceptional cases. It will be necessary to talk to the customer again, explaining to him that the recent Russian regulations IS-153-34.21.122-2003 operates with the protection zones with reliabiliy F = 0.9 and higher. At the reliability P, annually Netc = NM(1 - F) of lightning will break passing lightning rods by and will strike into the protected building. This is equivalent to an average of one direct impact in
(1)
years of operation. For an average unprotected cottage, with an expected 1 lightning strike in Тlight = 50 years of operation, the installation of lightning rods with reliability of 0.9 will increase the estimated time up to 500 years (on practice slightly less because installation of a lightning rod, although low, will increase the maximum height of the building, and , consequently, the frequency of lightning strikes). Even by the standards of English mansions it is quite a decent time in which lightning would be not the first on the list of other dangerous hazards. I think it will suit your customer, moreover, that at the reliability of 0.9 it is possible to get along with the simplest and cheapest solution because, for example, installation of a pair of relatively low air terminals, and even better - catenary wire over the ridge of the roof with the elevation of 1.5 - 2 meters.
The situation with high-rise buildings is not so obvious. According to the estimates that have been made up, a 10-storey building will get a lightning strike in about 6 years of operation. Its roof protection with the reliability of 0.9 (of course, if it is needed) will force to focus on one of its damage on average in about 60 years (the note about strengthening of storm activity at the expense of height increase of the lightning rods is valid here), but not in 5 centuries . Nevertheless, it is hardly advisable to complicate lightning protection, in order to achieve greater reliability. The building of modern construction will hardly suffer from contact with lightning, neither will the reinforced concrete roof. It is only necessary to worry about the equipment on the roof. But the 50 - 60 years - it is quite decent numbers in comparison to the guaranteed service life of any modern domestic appliances.
E. M. Bazelyan, DEA, professor
Energy Institute named after G.M. Krzyzanowski, Moscow
Read more "What is better - a series of lightning rods of small excess or one high?".
Useful materials:
- Series of articles about lightning protection for beginners
- Series of webinars about grounding and lightning protection with Professor E. M. Bazelyan
- Elements of external lightning protection
- Consultations on the selection, design and installation of grounding and lightning protection systems
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