The lightning discharge, which falls on the structural elements of the structure, is accompanied by an impressive electromagnetic effect. This, in turn, adversely affects the functioning of electrical equipment. Designing a lightning protection system allows you to reduce damage to cable conductors and minimize the likelihood of hitting an object with a strong charge.
Structure
Lightning rod is a passive protective measure that ensures the safe operation of facilities, preserves the he alth and lives of personnel and residents during the destructive effects of natural disasters. Lightning protection systems consist of the following main elements:
- Discharge receiver.
- Sink.
- Ground loop.
Types of lightning protection
Currently, active and passive lightning protection systems are distinguished. The traditional - passive version consists of a discharge receiver, a current-carrying element and grounding. Operating principlesuch a system is quite simple. The lightning rod takes on a lightning strike, after which it directs it to ground through the conductive paths of the down conductor. Ultimately, the discharge is extinguished in the ground.
In turn, the active lightning protection system works on the principle of air ionization. Due to this effect, the interception of the discharge occurs. Active lightning protection systems consist of the same elements as passive ones. However, their range is much larger and reaches about 100 meters. In this case, not only the object on which the elements of the system are mounted, but also nearby buildings are protected.
Active lightning protection is much more effective. Therefore, it is not surprising that this option is preferred by users in most developed countries. However, the cost of such solutions is much higher.
Options for discharge receivers
In the standard version, the full receiver is an ordinary metal pin, which is mounted in a vertical position on the roof of the structure. It is extremely important to fix this element at the highest, open point of the roof. If the building has a complex roof structure, in terms of increasing the level of security, it is recommended to install several discharge receivers.
Separate variants of lightning rods are distinguished, which differ according to their design:
- Pin protection.
- Metal cable.
- Lightning mesh.
Pin protection
If the structure contains a metal roof, then the correct solution is to install a pin lightning protection system. The discharge receiver in the form of a standard metal rod is mounted on a hill. The latter is connected to ground via down conductors.
Pin protection can be presented in the form of a round metal rod with a cross section of at least 8 mm or a strip piece of metal with parameters 25 x 4. The length of the element receiving the discharge should be such that its end rises above the highest point of the object by about 2 meters.
The ability of the lightning protection and grounding system to protect large areas from being struck by a discharge directly depends on the height of the pin. The area that a rod lightning rod can 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 lightning discharge receiver is made in the form of a metal cable. The latter is pulled 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 tension the cable, which are isolated from the discharge receiver. This method is also applicable to buildings with wooden roofs and roofs in the form of ceramic tiles.
Mesh protection
This solution is the most difficult to implement. howas a rule, it is applied to the roofs covered with tiles. In this case, the discharge receiver is a wire mesh laid on the roof of the building. The cross section of electrical conductors in this case should be at least 6 mm, and the cell pitch should be about 6 x 6 m.
The considered system is connected to the down conductor and the grounding element by welding. In the absence of this possibility, the use of bolted fasteners is allowed.
Installation of down conductors here is performed using round steel wire. They are laid in the direction of grounding along the walls and roof of the building, fixing the electrical conductors with special brackets.
The route for placing down conductor elements is selected in such a way that conductive elements do not come into contact with doors, windows, porches, metal garage doors, and other structures that people can interact with during the operation of the facility.
If a building contains an abundance of flammable materials (polystyrene foam, wood, plastic) in its structure, down conductors should be laid at a distance of about 15-20 cm from the surfaces., prolonged thunderstorms.
In this case, an internal lightning protection system can also be installed, which involves the installation of special arresters that can protect electrical equipment from surges. Such facilities are placed in close proximity to the entry point of the power cable into the facility.
Sink
Acts as an obligatory element of lightning protection systems. Designed to transfer charge to the ground loop.
The current lead is a metal wire with a thickness of at least 6 mm, which is connected to the discharge receiver. The combination of both elements allows you to extinguish loads up to 200,000 Amps. The most important condition for combining these structural components is the performance of highly reliable welding, which eliminates the possibility of rupture of joints and loosening of fasteners under the influence of wind, when falling snow layers.
The current lead is lowered along the walls of the object from the roof, fixing the conductor with brackets. The end of the metal wire is directed to the ground loop. If the lightning protection system of buildings and structures involves the installation of several charge-conducting elements, they are located at a distance of about 20-25 meters from each other at the maximum possible distance from doors and windows.
According to safety regulations, down conductors must not be sharply bent. The assumption of such miscalculations increases the likelihood of a spark discharge in the event of an object being struck by lightning. This, in turn, can cause the structure to ignite.
When installing a lightning protection system, it is desirable to make the down conductor as short as possible. At the same time, it is recommended to install it closer to the sharp ledges, the edges of the gables, dormers.
Grounding
The grounding device is designed to ensure efficient discharge discharge to the ground. It consists of several interconnected electrodes hammered into the ground.
When an object is put into operation, according to the rules, a common ground must be initially provided for all electrical appliances connected to the network. If it is not there, preparing the element is not so difficult. For this, a steel or copper conductor with a cross section of 50-80 mm is taken. A trench 3 m long and at least 0.8 m deep is dug. On opposite sides of the recess, rods are driven in, which are connected using a steel crossbar by welding. A down conductor is attached to the resulting structure. Finally, the places of the welding elbows are painted, after which the grounding structure is hammered to the bottom of the trench.
Checking lightning protection systems
Testing the discharge discharge system involves visual inspection of structural elements, as well as measurement of resistance indicators. Externally, the reliability of the connection of contacts between the lightning rod, down conductors and grounding is checked. All welds are tapped with a hammer.
Measuring the resistance of grounding conductors of individual lightning rods and bolted connections requires the presence of special equipment registered in accordance with regulations.
In the end
As you can see, there are several options for lightning protection of an object. These or other solutions are selected depending on the breadth of the budget, the nature of the structure, the need to ensure a certain level of security.
Currently, the development of power supply projects when putting an object into operation does not provide for the creation of lightning protection. At least its presence is not a requirement. Therefore, the decision on the appropriateness of arranging a system to protect the building from lightning strikes is made by each owner based on personal considerations.
