The lightning discharge, which falls on the structural elements of the structure, is accompanied by an impressive electromagnetic effect. This, in turn, affects the functioning of electrical equipment in the most negative way. The design of a lightning protection system allows to reduce damage to cable conductors and minimize the likelihood of an object being struck by a strong charge.
Structure
A lightning rod is a passive protective measure that ensures the safe operation of facilities, preserves the health and lives of staff, residents under the devastating effects of the elements. Lightning protection systems consist of the following main elements:
- Receiver discharge.
- Down conductor.
- 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 collector, and ground. The principle of operation of such a system is quite simple. The lightning rod takes on a lightning strike, and then directs it to ground through the conductive paths of the down conductor. Ultimately, the discharge is quenched in the ground.
In turn, the active lightning protection system works on the principle of air ionization. Due to this effect, the discharge is intercepted. Active lightning protection systems consist of the same elements as passive ones. However, their radius of action is much larger and reaches about 100 meters. In this case, not only the object on which the system elements are mounted is protected, but also nearby buildings.
Active lightning protection is much more effective. Therefore, it is not surprising that this is the option that users in most developed countries prefer. However, the cost of such decisions is much higher.
Discharge Receiver Options
In the standard version, the full receiver is an ordinary metal pin that is mounted in a vertical 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 has a complex roof structure, in terms of increasing the level of safety, it is recommended that several discharge receivers be installed.
Separate options for lightning rods, which differ according to the design:
- Whip protection.
- Metal cable
- Lightning protection mesh.
Whip protection
If the structure contains a metal roof, in this case, the installation of a lightning protection pin system seems to be the right solution. Installation of the discharge receiver in the form of a standard metal rod is carried out at a height. The latter is connected to ground through down conductors.
The 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 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 system and grounding to protect from damage by a discharge of significant areas directly depends on the height of the pin. The area that the pin 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 lightning discharge receiver is in the form of a metal cable. The latter is pulled along the ridge of the roof. Its height 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 decision is the most difficult to implement. As a rule, it is applied to the roofs covered with tiles. The discharge receiver in this case 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 such a possibility, the use of bolt fasteners is allowed.
The installation of down conductors here is carried out 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 the collector elements is selected so that the current-conducting elements do not come in contact with 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 (expanded polystyrene, wood, plastic) in its construction, down conductors should be laid at a distance of about 15-20 cm from surfaces.This approach to the arrangement of a lightning protection system will help prevent fires during strong, 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 surge surges. Such funds are located in close proximity to the point of entry of the power cable into the facility.
Down conductor
It is an indispensable element of lightning protection systems. Designed to transfer charge to the ground loop.
The down conductor is a metal wire with a thickness of at least 6 mm, which attaches to the discharge receiver. The combination of both elements allows you to pay off loads up to 200,000 amperes. The most important condition for combining these structural components is the performance of highly reliable welding, which eliminates the likelihood of rupture of joints and weakening of fastenings under the influence of the wind when snow layers fall.
The down conductor is lowered along the walls of the object from the roof, fixing the conductor with brackets. The end of the metal wire goes to the ground loop. If the lightning protection system of buildings and structures involves the installation of several charge-conducting elements, they are placed at a distance of about 20-25 meters from each other at the maximum possible distance from doors and windows.
According to safety precautions, down conductors must not be bent sharply. The admission of such miscalculations increases the likelihood of a spark discharge in the event of a lightning strike. This, in turn, can lead to ignition of the structure.
When installing the lightning protection system, it is advisable to make the down conductor as short as possible. At the same time, it is recommended to install it closer to sharp protrusions, the edges of the pediments, and dormers.
Grounding
The grounding device is designed to provide effective discharge discharge into the ground. It consists of several interconnected electrodes clogged into the ground.
When putting the facility into operation, according to the rules, a common grounding should initially be 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 is excavated with a length of 3 m and a depth of at least 0.8 m. On the 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 design. At the end, the places of the welding elbows are painted, after which the grounding structure is clogged to the bottom of the trench.
Testing 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 the contacts between the air terminal, down conductors and ground is checked. All places of welding are tapped with a hammer.
Carrying out measurements of the resistance indicators of grounding conductors of individual lightning rods and bolted connections suggests the presence of special equipment registered in accordance with regulatory enactments.
Eventually
As you can see, there are several options for 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 the facility is commissioned does not provide for the creation of lightning protection. At least its presence is not a requirement. Therefore, the decision on the feasibility of equipping a building protection system against lightning is taken by each owner based on personal considerations.