LIGHTNING PROTECTION OF BUILDINGS WITH PENTHOUSES

ZANDZ Technical center told you many times how to protect blocks of flats from lightning. We would like to talk specifically about houses with penthouses on the top floors, when designing their lightning protection, it is necessary to consider some peculiarities.

Penthouse owner buys not a flat only, but the area on the roof where he can stay and put his belongings. Due to a frequent staying of people on the roof, especially in summer, lightning protection of penthouses should be very carefully observed.

Solution with mesh won't fit due to aesthetic and rational reason. Nobody wants to see conductors of down conductors going all over the roof area or near. Except mesh, the only possible variant to protect a building with a penthouse is to use rod lightning rods.

We offer you to study the solution developed by ZANDZ Technical Center.

Task

Calculate lightning protection of a building with penthouses

Solution

Calculations of lightning protection are made in accordance with the following documents:

1. "Electric Installation Code" EIC 7th ed. (hereinafter - EIC).
2. "Instructions for organization of lightning protection of buildings, structures and industrial communications" IS 153-34.21.122-2003 (hereinafter IS).
3. "Instructions for lightning protection of buildings and structures" AD 34.21.122-87 (hereinafter - AD).

Lightning arresters are used for protection of structures from lightning strikes. A lightning arrester usually consists of a lightning rod, intercepting the lightning strike, a down conductor and a ground electrode. All these elements allow to safely drain lightning current into the ground without a damage for the protected object.

A building with a penthouse is a traditional structure in terms of lightning protection according to IS and belongs to category 3 according to AD.

Description of lightning protection system for a building with penthouses

The set of measures to provide the required lightning protection is offered by the following solutions:

1. Installation of 8 rod lightning rods 10 m high, fixed to the wall, is performed. It is taken into account that 2 m of the lightning rods height is used for fixation.
2. Lightning arresters are also interconnected for the arrangment of two down conductors from each lightning arrester with the help of galvanized steel wire 8 mm in diameter.
3. Fixation of down conductors is performed (installation distance 0.6-1 m):
   • to the wall – with a GL-11703A clamp;
   • on a flat roof by means of GL-11711 clamps.
4. Connection and branching of down conductors is carried out with the help of GL-11551A clamps.

The set of measures to ensure provision of the necessary requirements to the grounding device is offered by the following solutions:

1. Installation of a grounding device consisting of a horizontal electrode (galvanized tape with the cross-section of 4x30 mm), 0.5 meter deep, laid as a contour around the building 1 m from the walls.
2. Grounding circuit along the object's perimeter is used as a ground electrode system.
3. Interconnection of horizontal electrodes is carried out by using clamp ZZ-005-064.
4. The down conductor is connected to the galvanized tape protruding from the ground with the help of GL-11562M clamp.

The layout of elements in the lightning protection system and the grounding device is shown in Figure 1. Protection zone corresponds to zone B of the AD.

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