15.07.15
External lightning protection is designed to take on lightning strikes and divert current into the ground, thereby protecting facilities from damages. Properly designed and installed system of external lightning protection minimizes the chance of a direct lightning strike into an object and keeps it safe. Any system of external conventional (passive) lightning protection consists of the following elements:
Air terminal mast
Lightning protection mesh
Catenary wire lightning protection
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Lightning rod (Also known as: lightning arrester, lightning discharger) - the first element in contact with the lightning current. This device, which, as the name implies, takes the lightning strike upon itself. Despite the possibility of using natural lightning rods - elements of the building or nearby structures, artificial elements are more commonly used. Depending on the construction of objects and their roofing materials, artificial lightning rods can be of various forms (types):
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air terminal mast is a vertical lightning rod from 1 to 20 or more meters high and installed in such a way that the protection zone covers the protected object. Air terminal mast can be on the roof of the building or located next to it. Special clamps are used for the installation of mast, allowing to fix masts to vertical surfaces (walls) and horizontal (ground, roof). The materials of which the lightning rods are made are aluminum, copper, stainless steel, galvanized steel. Minimum cross sections of lightning rods are prescribed in the regulations for each material.
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Lightning protection mesh (mesh lightning rod) is located on the roof of buildings. Mesh step (mesh sizes) is determined by the categories of lightning protection, to which includes the object belongs and ranges from 5x5 to 20x20 m. Lightning protection mesh material, as in the case with air terminal mast may be aluminum, steel or copper.
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wire (catenary wire lightning protection). It represents a wire stretched between two masts. The object can be protected by several wires. Material of such a lightning rod is the same as in the other two cases.
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Selection in favor of a design happens on the base of the object structure and type of the object. However, the deciding factor, as a rule, is the desire of the customer (from the economic and aesthetic point of view), that does not always meet the requirements of GOST. In frequent cases, combinations of different types of lightning rods are possible.
Examples of air terminal masts
Great choice of lightning rods is presented on a separate page.
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The second element- part of the external lightning protection is a down conductor. It represents a wire stretching from a lightning rod to the ground electrode system. It can be installed on the wall and sewer pipe. It performs the function of draining lightning current to the ground. The requirements from p.3.2.2 are applied to the placement of down conductors, their number, the distance to the windows and doors, as well as the distance between the down conductors. Instructions on lightning protection of buildings, structures and industrial communications Industry Standard 153-34.21.122-2003. Structural elements of buildings can be used as down conductors.
Copper-bonded wire and tape can be used as down conductors.
down conductor
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Ground electrode is the only element of external lightning protection, submerged in the soil. It perform the function of lightning current drainage (50% and more), that came from a down conductor into the ground (see. p. 4.5). The remaining 50% are usually spread over the communications of the building (cable shells, water pipes and so on). In this regard, the ground electrode is composed of several ground electrodes installed as separate "points" for lightning protection. These electrodes are connected to each other with the help of grounding wire or tape, and, together with the grounding conductor connected to the down conductor, form a grounding device. The elements of different shape, size and material are used as a grounding electrode. However, they should also meet the requirements:
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Security level |
Material |
Cross-section, mm2 |
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of the ground electrode |
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I-IV |
Steel |
80 |
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I-IV |
Aluminum |
Not used |
|
I-IV |
Copper |
50 |
The number of grounding electrodes and their depth can vary depending on soil resistivity. Thus, for installation in ordinary loam soil with a specific resistance, 2 electrodes 3 meters each should be enough, in contrast to sandy soil, where the depth and the number of grounding electrodes can increase several times. The right amount of ground electrodes starts at 2, and the minimum length of each - from 3 meters (regulated by the AD 34.21.122-87).
Ground electrode
To arrange reliable grounding as part of external lightning protection, ZANDZ ready grounding kits are used. Ground electrodes on the base of these kits can be easily installed by one person, and do not require welding!
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For advice on equipment and calculations of grounding and lightning protection, please contact our technicians!
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