Lightning protection systems: design and installation

The discharge of lightning, which falls on the structural elements of the structure, is accompanied by an impressive electromagnetic effect. This, in turn, has a very negative effect on the functioning of electrical equipment. To reduce the damage to the cable conductors and minimize the likelihood of an object being struck by a heavy charge allows the design of a lightning protection system.

Structure

The lightning rod is a passive protective measure that ensures the safe operation of facilities, preserves the health and lives of the personnel, tenants in the event of destructive effects of the natural disaster. There are lightning protection systems of the following main elements:

• Receiver discharge.
• A current collector.
• Earthing circuit.

Types of lightning protection

Currently, the active and passive lightning protection systems are isolated. The traditional - passive version consists of a discharge receiver, a current collector and grounding. The principle of functioning of such a system is quite simple. The lightning conductor takes over the lightning stroke, and then directs it to ground through the conductive paths of the current lead. Eventually the discharge is extinguished in the ground.

In turn, the active lightning protection system operates on the principle of ionization of air. Due to this effect, the interception of the discharge occurs. There are active lightning protection systems of the same elements as the passive ones. However, the radius of their action is much larger and reaches about 100 meters. In this case, under protection is not only the object on which the elements of the system are mounted, but also nearby structures.

Active lightning protection is much more effective. Therefore, it is not surprising that this is the preferred option for users in most developed countries. However, the cost of such solutions is an order of magnitude higher.

Types of discharge receivers

In the standard version, the full receiver is a conventional metal pin that is mounted in an upright position on the roof of the structure. It is extremely important to fix this element in the highest, open point of the roof. If the structure is characterized by a complex roof structure, in terms of increasing the level of safety, installation of several discharge receivers is recommended.

There are separate versions of lightning receivers, which differ according to the design:

• Pin protection.
• A metal cable.
• Lightning protection net.

Whip protection

If the structure contains a metal roof, then the correct solution is the installation of a lightning protection pin system. Installation of the discharge receiver in the form of a standard metal rod is carried out on a hill. The latter is connected to ground by means of current leads.

The pin protection can be presented in the form of a round metal rod with a section of at least 8 mm or a strip segment of metal with parameters of 25 x 4. The length of the receiving element should be such that its ending rises above the highest point of the object by approximately 2 meters.

The height of the pin position directly affects the ability of the lightning protection system and grounding to protect against significant damage to the area. The area that the lightning rod is able to protect is defined as a circle with a radius identical to the height of the rod.

Cable protection

In the presence of a roof covered with slate, the receiver of the lightning discharge is made in the form of a metal cable. The latter is stretched along the ridge of the roof. The height of its location should be at least 0.5 meters from the surface.

If it is necessary to create the most reliable protection, metal supports are used to pull the cable, which are isolated from the discharge receiver. This method is also applicable for buildings with wooden roofs and roofs in the form of ceramic tiles.

Mesh protection

This solution is the most difficult to implement. As a rule, it is used for roofs covered with tiles. Receiver discharge in this case is a wire mesh, laid on the roof of the building. The cross section of the electrical conductors in this case should be at least 6 mm, and the step of the cells is of the order of 6 x 6 m.

This system is connected to the current collector and the grounding element by welding. If this is not possible, bolt fasteners may be used.

The installation of the current collectors is carried out using round steel wire. They lay them towards the ground on the walls and roof of the building, fixing the electrical conductors with special staples.

The route for placing the elements of the current collector is selected in such a way that the conductive elements do not touch the doors, windows, porch, metal garage doors, other structures that people can interact with during the operation of the object.

If the building contains an abundance of flammable materials (polystyrene foam, wood, plastic) in its construction, the conductors of the current collector should be laid at a distance from the surfaces of about 15-20 cm. Such an approach to the arrangement of the lightning protection system will avoid the occurrence of fires in strong, prolonged thunderstorms.

In this case, an internal lightning protection system can also be installed, which involves the installation of special arresters capable of protecting electrical equipment from impulse overvoltages. Similar means are placed in close proximity to the point where the power cable enters the object.

Current collector

Acts as an obligatory element of lightning protection systems. It is designed to transfer the charge to the ground loop.

A current collector is a metal wire with a thickness of at least 6 mm, which is connected to a discharge receiver. The combination of both elements allows you to repay loads of up to 200,000 amperes. The most important condition for combining these structural components is the performance of highly reliable welding, which eliminates the possibility of breaking the joints and loosening the anchorages under the influence of wind, when falling snow layers.

A collector is lowered on the walls of the object from the roof, fixing the conductor with clamps. The end of the metal wire is routed to the ground loop. If the lightning protection system of buildings and structures involves the installation of several conductive elements, they are located at a distance of about 20-25 meters from each other at the maximum possible distance from the doors and windows.

According to safety precautions, the current collectors are not allowed to bend sharply. The admission of such miscalculations increases the likelihood of a spark discharge in the event of an object being struck by lightning. This, in turn, can lead to the ignition of the structure.

When installing a lightning protection system, it is advisable to make the current collector as short as possible. At the same time, its installation is recommended to be made closer to the sharp projections, the edges of the pediments, the auditory windows.

Earthing

The grounding device is designed to ensure efficient discharging of the discharge into the ground. It is a combination of several electrodes clogged into the ground.

When the facility is put into operation, according to the rules, a general grounding for all electrical appliances connected to the network must be provided initially. If it does not, prepare the element is not so difficult. To do this, take a steel or copper conductor section of 50-80 mm. Excavated trench length of 3 m and a depth of at least 0.8 m. On opposite sides of the grooves are driven rods, which are connected with a steel bar by welding. A current collector is connected to the received structure. At the end of the place, the welding knees are painted, after which the grounding structure is clogged to the bottom of the trench.

Checking lightning protection systems

Testing discharge discharge system involves visual inspection of structural elements, as well as measurement of resistance values. Externally, the reliability of the connection of the contacts between the lightning receptacle, current leads and ground is verified. All welding places are taped with a hammer.

Carrying out of measurements of indicators of resistance of earthing switches of separate lightning rods and bolted connections assumes availability of special equipment registered in accordance with regulatory enactments.

Eventually

Apparently, there are several variants of lightning protection of the object. These or other decisions are selected depending on the breadth of the budget, the nature of the structure, the need to ensure a certain level of security.

At present, the development of electricity supply projects when putting the facility into operation does not provide for the creation of lightning protection. At least, its presence is not a mandatory requirement. Therefore, the decision on the appropriateness of the arrangement of the structure protection system against lightning damage is taken by each owner on the basis of personal considerations.