The lightning rod directly perceives a direct lightning strike. Therefore, it must reliably withstand the mechanical and thermal effects of the current and the high-temperature lightning channel. The supporting structure carries a lightning rod and down conductor, combines all elements of the lightning rod into a single, rigid, mechanically strong structure. In electrical installations, lightning rods are installed near live parts that are under operating voltage. The fall of the lightning rod on the current-carrying elements of the electrical installation causes a severe accident. Therefore, the supporting structure of the lightning rod must have high mechanical strength, which would exclude cases of lightning rod falling on the equipment of power plants and substations in operation. The lightning rod must have a reliable connection with the ground with a resistance of 5-25 ohms to the spreading of the impulse current. The protective property of rod lightning rods is that they orient the leader of the emerging lightning discharge towards themselves. The discharge occurs necessarily at the top of the lightning rod, if it is formed in a certain area located above the lightning rod. This area has the form of an upward expanding cone and is called the 100% lesion zone.
It has been established by experimental data that the lightning orientation height H depends on the height of the lightning rod h. For lightning rods up to 30 meters high:
and for lightning rods with a height of more than 30 meters H=600 m.
where is the active part of the lightning rod, corresponding to its excess over the height of the protected object:
Figure 1.1 Protection zone of a single rod lightning rod: 1 - boundary of the protection zone; 2 - section of the protection zone at the level.
To calculate the protection radius at any point of the protective zone, including at the height of the protected object, the following formula is used:
where is a correction factor equal to 1 for lightning rods with a height of less than 30 meters and equal to higher lightning rods.
Protection zones of extended objects in which several lightning rods are used, it is advisable that the zones of their 100% defeat close over the object or even overlap each other, excluding the vertical lightning breakthrough to the protected object. The distance (S) between the axes of the lightning rods should be equal to or less than the value, determined from the dependency:
The protection zone of two and four rod lightning rods in the plan at the height of the protected object has the outlines shown in Figure 1.3, a, b.
The smallest width of the protection zone, the protection radius shown in the drawing is determined in the same way as for a single lightning rod, but is determined by special curves. Figure 1.2 shows the designs of lightning rods. If lightning rods with a height of up to 30 meters located at a distance, the smallest width of the protection zone is equal to zero.
Figure 1.2 Structures of rod lightning rods on reinforced concrete supports: a - from vibrated concrete; b - centrifuged concrete
Figure 1.3 Rod lightning rods on metal supports: a - wire lightning rod (supporting structure); b - rod lightning rod (supporting structure)
Figure 1.3 shows the designs of lightning rods on metal supports. The protection radii are determined in this case in the same way as for single lightning rods. The size is determined from the curves for each pair of lightning rods. The diagonal of a quadrilateral or the diameter of a circle passing through the vertices of a triangle formed by three lightning rods, according to the conditions of protection of the entire area, must satisfy the following dependencies:
For lightning rods less than 30 m high:
For lightning rods with a height of more than 30 m:
Free-standing rod lightning rods with metal supports are installed on reinforced concrete foundations. Down conductors for such lightning rods are load-bearing structures. On metal and reinforced concrete structures of outdoor switchgear, as a rule, lightning rods with metal bearing parts are installed. The design of their fastening is determined by the features of the outdoor switchgear design to which the rod lightning rod is attached. Typically, the design of lightning rods installed on outdoor switchgear structures is a steel pipe, often consisting of pipes of several diameters. Lightning rods with a height of more than 5 m at the base have a lattice structure made of angle steel. The potential at the lightning rod at the moment of discharge is determined by the dependence:
where is the impulse grounding resistance of the lightning rod 5-25 Ohm;
Lightning current in a well-grounded object.
The potential at the lightning rod is determined by:
where is the steepness of the current wave front;
- - lightning rod point at the height of the object;
- - specific inductance of the lightning rod.
To calculate the minimum allowable approach of an object to a lightning rod, one can proceed from the dependence:
where is the permissible impulse electric field strength in the air, assumed to be 500 kV / m.
Guidelines for surge protection recommend that the distance to the lightning rod be taken equal to:
This dependence is valid for a lightning current of 150 kA, a current slope of 32 kA/μs and a lightning rod inductance of 1.5 μH/m. Regardless of the calculation results, the distance between the object and the lightning rod must be at least 6 meters.
Rope lightning rod. The values of the coefficients k and z are taken depending on the allowable probability of a lightning breakthrough into the protection zone. The probability of a lightning breakthrough into the protection zone is equal to the ratio of the number of lightning discharges into the protected structure to the total number of lightning discharges into the lightning rod and the protected structure. If the probability of a lightning breakthrough into the protection zone is 0.01, then the coefficient is 1, and with an acceptable probability of 0.001, i.e., the protective zones of lightning rods are somewhat smaller than the protective zones of rod lightning rods. The shape of the protection zone of two parallel wire lightning rods up to 30 m high. The outer boundaries of the protection zone of each wire are determined in the same way as for a single wire lightning rod. Depending on the design of the supports, one or two cables can be used, tightly attached to the metal support or to the grounding metal slopes of the wooden supports. To protect the cable from overburning by lightning current and to control the grounding, the support of the cable is made using one suspension insulator shunted with a spark gap. The efficiency of cable protection is the higher, the smaller the angle formed by the vertical passing through the cable and the line connecting the cable with the outermost of the wires. This angle is called the protective angle, taking its value within
The protection zone of two wire lightning rods with a height of more than 30 m. The method of constructing a protection zone for this case is the same as for wire lightning rods up to 30 m high, but at a distance from the top, the zone is truncated in the same way as for single wire lightning rods. The width of the protective zone, which excludes direct damage to the wires at the level of their suspension height, is determined by the dependence:
This dependence is valid for a cable suspension height of 30 m and below.
First, let's understand the essence of the concept. Lightning rod means the same thing lightning protection or Lightning protection and different from lightning rod, which is often called only the lightning-receiving part of the protection system for buildings and structures. That is lightning rod- this is a "lightning rod + down conductor + grounding", or an external component of the system. If you look at the scheme of any complex lightning protection, whether it is a private house or an industrial, office and administrative building, then this is its part, which is designed specifically for protection against direct lightning strikes.
Designs (types) of lightning rods
In total, there are 3 basic schemes: rod (figures a, b), cable (c) and lightning rod in the form of a lightning protection mesh (or mesh) (d). The combined scheme involves a combination of basic options.
By the number of identical lightning protection parts - single, double, etc.
According to the nature and place of installation, the rods are divided into lightning rods, prefabricated rods, which can be installed on flanges, brackets, special supports, or stand alone. Air-termination masts usually have a telescopic design and a method of installation on or in the ground.
Cable is a cable stretched between supports. The contour can be anything, including closed. It essentially includes the simplest and cheapest version of a lightning rod for a private house or summer cottage, when instead of a cable, a conductor with a radius of 8-10 mm (aluminum, steel or copper, depending on the material and color of the roof) is pulled at a distance at least 20 mm from the ridge itself, bring its ends beyond the extreme points to a distance of about 30 mm and bend slightly upward.
Lightning protection mesh is used on flat or slightly sloped roofs.
So, as we said, the external lightning protection system can be isolated from the building (separately standing lightning rods or cables, as well as neighboring structures that act as natural lightning rods), or can be installed on the protected building and even be part of it.
Calculation of a lightning rod
The choice of lightning rods is recommended to be made with the help of special computer programs capable of calculating the probabilities of a lightning breakthrough and a protection zone based on the dimensions of buildings, roof plans and structural elements on it. That is why it is more reliable to contact specialized organizations that will quickly give you various options and configurations of lightning rods.
Although, if the configuration of the protected object allows you to get by with the simplest lightning rods (single rod, single cable, double rod, double cable, closed cable), their dimensions can be determined independently, using the instructions specified in Instructions SO 153-343.21.122-2003 and RD 34.21.122 -87 protection zones.
An object is considered protected if it completely falls into the protection zone of the lightning protection device, which is assigned the required level of reliability.
Protection zone of a single rod lightning rod (according to SO 153-34.21.122-2003)
The standard protection zone in this case is a circular cone with a vertex that coincides with the vertical axis of the lightning rod. The dimensions of the zone in this case are determined by 2 parameters: the height of the cone h 0 and the radius of its base r 0 .
The table below shows their values depending on the required protection reliability for lightning rods up to 150 m high from ground level. For high altitudes, it is necessary to use special programs and calculation methods.
For other types and combinations of lightning rods, see the variations in the calculation of protection zones in chapter 3.3.2 of SO 153-343.21.122-2003 and Appendix 3 of RD 34.21.122-87.
Now, to determine whether your object X falls into the protection zone, we calculate the radius of the horizontal section r x at a height h x and postpone it from the lightning rod axis to the extreme point of the object.
Rules for determining protection zones for objects up to 60 m high (according to IEC 1024-1-1)
The SO Instruction contains a methodology for designing lightning rods for conventional structures according to the IEC 1024-1-1 standard, which can only be accepted if the calculations for it are more “rigid” than the requirements of this Instruction.
According to it, the following 3 methods can be applied for different cases:
- protective corner method for simple shapes or small parts of large structures
- fictitious sphere method for structures of complex shape
- protective mesh in general and in particular for surface protection
The table for different categories (levels) of lightning protection (more about categories or classes here) shows the corresponding values of the parameters of each of the methods (fictitious sphere radius, maximum permissible protection angle and grid cell step).
Protection angle method for roof superstructures
The angle value is selected according to the graph on the diagram for the corresponding height of the lightning rod, which is measured from the protected surface, and the lightning protection class of the building.
The protection zone, as mentioned above, is a circular cone with a vertex at the top of the lightning rod.
Dummy sphere method
It is used when it is difficult to determine the size of the protection zone for individual structures or parts of the building using the protective corner method. Its boundary is an imaginary surface, which is outlined by a sphere of the selected radius r (see the table above), if it were rolled over the top of the structure, bypassing the lightning rods. Accordingly, an object is considered protected if this surface does not have common points of intersection or touch with it.
Lightning mesh
This is a conductor laid on top of the roof with a cell pitch selected depending on the lightning protection class of the building. In this case, all metal elements on the roof (antiaircraft lights, ventilation shafts, air intakes, pipes, etc.) must be connected to the grid. Otherwise, it is necessary to mount additional lightning rods for them. More details about the design features and installation options can be found in the material "Lightning protection on a flat roof".
The cell step according to Russian standards is chosen based on the category of lightning protection of the building (it can be less, but not more).
The lightning protection mesh is mounted subject to a number of conditions:
- conductors lay the shortest paths
- during a lightning strike, the current for tapping to ground must be able to choose at least 2 different paths
- in the presence of a ridge and a roof slope of more than 1 to 10, the conductor must be laid along it
- no parts and elements made of metal should protrude beyond the outer contour of the mesh
- the outer contour of the wire mesh is required, mounted along the edge of the roof perimeter, and the edge of the roof must protrude beyond the dimensions of the building
Materials and sections of lightning rod conductors
The materials used for the production of lightning protection equipment and down conductors are galvanized and stainless steel, copper and aluminum. They are subject to the requirements of corrosion resistance and mechanical strength, if a protective coating is used, then it must have good adhesion to the base material.
The table shows the requirements for the profile of conductors and rods in terms of the minimum cross-sectional area and diameter (according to GOST 62561.2-2014)
Installation of a lightning rod for a private house and an industrial building
Let's consider what installation elements usually include an external lightning protection system. The figures below show examples of a lightning rod for a private house and an industrial building.
The corresponding numbers here indicate the following products and their names:
Round and flat conductors, cables
Lightning protection components on flat roofs, jumpers and compensators
Lightning protection components on pitched roofs, roof conductor holders
Lightning protection components on metal roofs, roof conductor holders
Down conductors, holders of down conductors
Earth entry rods, connecting conductors, manholes, conductor holders
Gutter terminals, terminals, connection components
Lightning rods, components
Isolated lightning protection
Installation can be divided into three stages: installation of the lightning-receiving part of the external lightning protection system (lightning rods and their fastening elements), laying down conductors (roofing and facade part of the building) and earthworks for grounding. As a rule, for all companies, the cost of work is a certain percentage of the price of materials.
MZK-Electro company offers excellent prices for lightning rods and accessories. The range of products in our warehouse is more than 1,500 positions, the purchase is carried out directly under dealer contracts from direct manufacturers, which implies mandatory certification and warranty. All products have the necessary quality certificates and a guarantee. We are also engaged in the design and installation of any lightning protection systems for buildings and structures, both for private homeowners and industrial enterprises. You can get acquainted with our prices in the corresponding section.
Cost calculation
Our facilities
JSC "Mosvodokanal", Sports and recreation complex of the rest house "Pyalovo"
Address of the object: Moscow region, Mytishchi district, village. Prussians, 25
Type of work: Design and installation of an external lightning protection system.
Composition of lightning protection: A lightning protection mesh is laid on the flat roof of the protected structure. The two chimneys are protected by installing lightning rods 2000 mm long and 16 mm in diameter. Hot-dip galvanized steel with a diameter of 8 mm (section 50 sq. mm in accordance with RD 34.21.122-87) was used as a lightning conductor. The down conductors are laid behind the downpipes on clamps with clamping terminals. For down conductors, a conductor made of hot-dip galvanized steel with a diameter of 8 mm was used.
GTPP Tereshkovo
Address of the object: Moscow city. Borovskoe sh., communal area "Tereshkovo".
Type of work: installation of an external lightning protection system (lightning-receiving part and down conductors).
Accessories: manufactured by OBO Bettermann.
Execution: The total amount of hot-dip galvanized steel conductor for 13 facilities in the facility was 21.5000 meters. A lightning protection mesh is laid along the roofs with a cell spacing of 5x5 m, 2 down conductors are mounted at the corners of buildings. Wall holders, intermediate connectors, holders for a flat roof with concrete, high-speed connecting terminals were used as fastening elements.
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LIGHTNING WIRE - a device for protecting buildings and structures from direct lightning strikes. M. includes four main parts: a lightning rod that directly perceives a lightning strike; down conductor connecting the lightning rod with the ground electrode; ground electrode through which the lightning current flows to the ground; the bearing part (support or supports) intended for fixing the lightning rod and down conductor.
Depending on the design of the lightning rod, rod, cable, mesh and combined lightning rods are distinguished.
According to the number of jointly acting lightning rods, they are divided into single, double and multiple.
In addition, at the location of M. there are separate, isolated and not isolated from the protected building. The protective action of lightning is based on the property of lightning to strike the highest and well-grounded metal structures. Due to this property, a protected building that is lower in height is practically not struck by lightning if it enters the M protection zone. The M protection zone is the part of the space adjacent to it and with a sufficient degree of reliability (at least 95%) providing protection for structures from direct strikes lightning. Most often, rod M is used to protect buildings and structures.
Rope lightning is most often used to protect buildings of great length and high-voltage lines. These M. are made in the form of horizontal cables fixed on supports, along each of which a current collector is laid. Rod and cable M. provide the same degree of reliability of protection.
As lightning rods, you can use a metal roof, grounded at the corners and along the perimeter at least every 25 m, or a steel wire mesh with a diameter of at least 6 mm superimposed on a non-metal roof, having a mesh area of up to 150 mm2, with knots fixed by welding, and grounded just like a metal roof. Metal caps are attached to the grid or conductive roof above the chimneys and ventilation pipes, and in the absence of caps, wire rings specially applied to the pipes.
M. rod - M. with a vertical arrangement of the lightning rod.
M. cable (extended) - M. with a horizontal arrangement of the lightning rod, fixed on two grounded supports.
LIGHTNING PROTECTION ZONES
Usually, the zone of protection is designated by the maximum probability of a breakthrough corresponding to its outer border, although the probability of a breakthrough decreases significantly in the depth of the zone.
The calculation method makes it possible to construct a protection zone for rod and wire lightning rods with an arbitrary value of the breakthrough probability, i.e. for any lightning rod (single or double), you can build an arbitrary number of protection zones. However, for most public buildings, a sufficient level of protection can be provided using two zones, with a breakthrough probability of 0.1 and 0.01.
In terms of reliability theory, the breakthrough probability is a parameter that characterizes the failure of a lightning rod as a protective device. With this approach, the two accepted protection zones correspond to the degree of reliability of 0.9 and 0.99. This reliability assessment is valid when an object is located near the border of the protection zone, for example, an object in the form of a ring coaxial with a lightning rod. For real objects (ordinary buildings), on the border of the protection zone, as a rule, only the upper elements are located, and most of the object is placed in the depth of the zone. The assessment of the reliability of the protection zone along its outer border leads to excessively low values. Therefore, in order to take into account the mutual arrangement of lightning rods and objects existing in practice, protection zones A and B are assigned in RD 34.21.122-87 an approximate degree of reliability of 0.995 and 0.95, respectively.
Single rod lightning rod.
The protection zone of a single rod lightning rod with a height h is a circular cone (Fig. A3.1), the top of which is at a height h0 1.1. Protection zones of single rod lightning rods with height h? 150 m have the following overall dimensions. Zone A: h0 = 0.85h, r0 = (1.1 - 0.002h)h, rx = (1.1 - 0.002h)(h - hx/0.85). Zone B: h0 = 0.92h; rx \u003d 1.5 (h - hx / 0.92). For zone B, the height of a single rod lightning rod for known values of h and can be determined by the formula h = (rx + 1.63hx)/1.5. Rice. P3.1. Protection zone of a single rod lightning rod: I - the boundary of the protection zone at the hx level, 2 - the same at ground level Single wire lightning rod. The protection zone of a single wire lightning rod with a height h? 150 m is shown in fig. P3.5, where h is the height of the cable in the middle of the span. Taking into account the sag of the cable with a cross section of 35-50 mm2, with a known height of supports hop and span length a, the height of the cable (in meters) is determined: h = hop - 2 at a< 120 м; h = hop - 3 at 120< а < 15Ом. Rice. P3.5. Protection zone of a single wire lightning rod. The designations are the same as in Fig. P3.1 The protection zones of a single wire lightning rod have the following overall dimensions. In order to ensure the safety of people, the safety of structures, equipment and materials from the thermal, mechanical and electrical effects of lightning, a special system of protective security measures has been developed - lightning protection, which is a complex of technical solutions and special devices. Requirements for the organization of lightning protection systems for buildings and structures located on the territory of the Russian Federation are regulated by the following regulatory documents: When developing a system of protective measures for objects against lightning strikes, design organizations can be guided by the provisions of any of these instructions or use a combination of them. A full range of lightning protection measures for ground facilities implies a combination of external systems - protection against direct lightning strikes and internal lightning protection - protection devices against secondary influences (pickup and surge). External lightning protection provides a minimal chance of a direct lightning strike into the building, thereby protecting it from damage. It takes on a lightning strike, which is then diverted into the ground. The complex of measures of the external lightning protection system includes three elements: Lightning rod (lightning rod, lightning rod) is a device designed to intercept lightning. The principle of operation of the lightning rod is that the lightning strike falls on the highest and well-grounded metal structures. Therefore, if the object is located in the protection zone of the lightning rod, then it will not be struck by lightning. Down conductor- a device that drains the lightning current from the lightning rod to the ground. It is installed on the wall of the structure and downpipes. It is a copper-plated wire or strip that stretches from the lightning rod to the ground electrode. grounding conductor- a device that drains 50% or more of the lightning current that has passed through the down conductor to the ground. The remaining current is distributed along the communications adjacent to the structure. The grounding conductor is the only element of external lightning protection immersed in the ground. Grounding electrodes can be elements of different sizes, materials and shapes that meet the requirements of regulatory documents. An external lightning protection system can be installed both on the protected object itself and in isolation: in the form of separate lightning rods and neighboring structures that act as natural lightning rods. The lightning protection system is organized according to the principle of maximum use of natural lightning rods. In cases where the security they provide is insufficient, they are combined with specially installed elements (artificial lightning rods). The simplicity of the devices, the absence of the need for special maintenance and the relatively reliable protection of the object from lightning strikes have provided the most widespread lightning rods in practice. There are the following types of passive lightning rods: Lightning rods are made of various materials: aluminum, copper, stainless or galvanized steel, taking into account the minimum sections for each of them in accordance with regulatory documents. Rod lightning rods-masts mounted on towers An lightning rod (or lightning rod) is a vertical device, usually from 1 to 20 meters high, on or near the roof of a structure, installed in such a way that the protection zone covers the protected object. Special clamps used when installing masts allow them to be fixed to both vertical (wall) and horizontal (ground, roof) surfaces. Two down conductors are mounted from each mast. If the lightning rod is located on the roof of the structure, then the grounding device used is a horizontal circuit, which is reinforced at the points of down conductors with vertical ground electrodes. The grounding device of free-standing masts is performed by three vertical grounding conductors, interconnected according to the “chicken paw” type. Rod lightning rods (masts) are chosen mainly for the protection of small buildings, not of complex architecture. The design of a cable lightning rod consists of two masts and a steel cable stretched between them. The ends of the cable adjoin one down conductor with a grounding conductor of the "chicken paw" type. With the correct location of the support masts, lightning discharges go into the ground outside the protected object. Cable lightning protection is widely used for low buildings. Rod and wire lightning rods are divided into single, double and multiple, forming a common protection zone of the object. Multiple lightning rods are used to protect large buildings or several structures that occupy a large area. Lightning protection mesh installed on the roof of the building The design of the lightning rod is made in the form of a grid of metal rod on the roof of the protected structure. The lightning protection mesh is laid on the roof of the building with a step (cell size) from 5x5 m to 20x20 m, depending on the lightning protection category of the object. A common question that arises when designing is whether it is possible to lay a lightning protection mesh directly on the roof of the roof. In fact, the mesh can be laid directly on the roof or under the insulation (see paragraph 2.11. in instructions RD 34.21.122-87). According to instructions SO 153 3.2.2.4. if the temperature rise is dangerous for the object, then the distance between the down conductor and the combustible roof or wall must be more than 0.1 m. In this case, the metal clamp may be in contact with the combustible wall. If the wall or roof is combustible, but the temperature increase is not dangerous for them, then fastening directly to the wall is allowed. The choice of the type of lightning rod depends on which category the building belongs to according to the lightning protection device. For lightning protection of buildings belonging to category I, lightning protection masts or wire lightning rods are used, For lightning protection of category II buildings with a non-metal roof, lightning protection masts or wire lightning rods are used, installed in isolation or on the protected object itself, see clause 2.11 in RD 34.21.122-87. In this case, a prerequisite is to provide a protection zone in accordance with the requirements of the table given in the article and Appendix 3 in RD 34.21.122-87. If lightning protection devices are located at the facility, then at least two down conductors are required for each lightning protection mast or wire lightning protection rack. To ensure lightning protection of structures, the roof slope of which does not exceed 1:8, a lightning protection mesh can be used. For lightning protection of buildings belonging to category III, one of the above methods is used (lightning protection masts, lightning rods or mesh) in compliance with applicable requirements. The choice of the number and height of rod and wire lightning rods should be made by calculating their protection zones. A single wire lightning rod provides a protection zone in the form of an isosceles triangle, the apex of which is at a height h0 The calculation of the protection zones of rod and cable lightning rods is carried out according to CO 153-343.21.122-2003. Based on the foregoing, we conclude that the choice of the type of lightning rod must be made based on the structures of buildings and structures and their roofing materials, with the obligatory consideration of the lightning protection category and compliance with all the necessary requirements of RD 34.21.122-87 and CO 153-343.21.122-2003 . The widespread use of rod lightning rods is due to the simplicity and relative cheapness of their manufacture. Basically, lightning protection masts are chosen to protect small buildings, not complex architecture. For lightning protection of large buildings or several structures occupying a large area, multiple lightning rods are used. The presence of an installed external lightning protection system is not a guarantee of complete protection against all lightning effects. To protect against secondary consequences, it is necessary to protect the object in a complex way: elements of external lightning protection, as well as internal lightning protection, which is a combination of surge protection devices (SPD). see also: The basis of a wire lightning rod, as the name implies, is a galvanized metal (usually steel is used) cable. At the same time, it is recommended that its cross-sectional area be equal to at least 35 square meters. mm. Cable lightning rods are used where other options are quite difficult to install, for example, on long roofs and high-voltage lines. However, sometimes they are placed in small cottages. One of the disadvantages of a wire lightning rod is that the wire is visible on the roof, but it can be disguised if desired. In some situations, wire lightning rods can be placed not on the protected object itself, but near it. Cable lightning protection is of two types: For a single one, only two masts are enough, between which a cable is stretched. And each mast at the same time has a connection with its own down conductor, ground electrode and lightning rod. In certain cases, four masts are installed on the building at once. They are connected by two cables, and so that they are parallel to each other at the same height. When lightning strikes, they act together as a whole - this is a double wire lightning rod.
The design of a wire lightning rod, as well as its installation, in most cases is a rather complicated task that requires the involvement of professionals. Even at the design stage, it is imperative to carry out - that is, to determine the specific area of \u200b\u200baction and other parameters. The calculation is carried out according to rather complex formulas, in which, in particular, the following indicators should be taken into account: The installation itself must strictly comply with the rules for the installation of electrical installations (PUE), and therefore has many subtleties that an unprepared person may not know about. The cables are connected to the masts and down conductors with bolt clamps. Two of these clamps are required for each connection. If the roof is finished with flammable materials (plastic, wood, etc.), then the cables should be at a distance of 10-15 centimeters from the surface. In addition, some elements of the future lightning protection should be connected by welding, and the cross section of the weld should be at least three times higher than the nominal section of the cable. It is undesirable that the spans be more than 15 meters; in order to avoid this, it is recommended to install additional supports. The lightning rod supports must be equipped with a small wire ring through which the wire will pass. Supports and masts must be strong enough to support the weight of the structure in strong gusts of wind. It is also worth remembering that the smaller the angle between the imaginary vertical passing through the cable and the line connecting the cable to the outer wire (this is called a protective angle, and its value, according to standards, should be 20-30 degrees), the more effective the cable will be. lightning rod. In addition to cable, there is also rod and mesh lightning protection. The mesh one is the most difficult in execution, and the rod one, like the cable one, is quite simple in design. A distinctive feature of the rod system is the presence of a vertical pin, which takes on a lightning strike. Practice shows that they protect a much smaller area than cable ones, and therefore many people stop at the second option of these two. It is a compromise between a conventional pin (mast) and a mesh. Ultimately, the choice of this or that lightning protection will depend on the specifics of the building or structure, the state of electrical appliances, the type of grounding of the electrical network, the frequency of thunderstorms in a particular climatic zone.
Regulatory regulation
Lightning protection elements
Internal lightning protection includes a complex of surge protection devices (SPDs) and performs the functions of limiting the magnetic and electric fields of lightning, thereby preventing sparks inside the protected object.2. Lightning rod as part of a lightning protection system
Rod lightning rod (mast)
Down conductors are mounted around the entire perimeter of the lightning rod in increments of 10 to 25 m (depending on the level of protection). The type of roof of the protected structure (soft or hard) determines the method of attaching the "mesh" to the roof surface. Subject to the condition of a non-combustible base, the lightning protection mesh can be laid in the "roofing pie". The ground electrode for this type of lightning rod is a closed horizontal circuit, reinforced at the points of down conductors.3. Categories of lightning protection
The standards establish three categories of lightning protection devices depending on the explosive and fire hazard, capacity, fire resistance and purpose of the protected objects, as well as taking into account the average annual duration of thunderstorms in the geographical area of the object, see the categories of lightning protection in table No. 1 from paragraph 1.1. in RD 34.21.122-87:
Buildings and constructions
Location
Type of protection zone when using rod and wire lightning rods
Category of lightning protection
Buildings and structures or parts thereof, the premises of which, according to the PUE, belong to zones of classes B-I and B-II Throughout the USSR Zone A I
The same classes B-Ia, B-Ib, B-IIa With the expected number of lightning strikes per year of a building or structure N> 1 - zone A; at N≤1 — zone B II
Outdoor installations that create a zone of class B-Ig according to the PUE Throughout the USSR Zone B II
Buildings and structures or parts thereof, the premises of which, according to the PUE, belong to zones of classes P-I, P-II, P-IIa For buildings and structures of I and II degrees of fire resistance at 0.1 2-zone A III
Small buildings located in rural areas of III-V degrees of fire resistance, the premises of which, according to the PUE, belong to zones of classes P-I, P-II, P-IIa In areas with an average duration of thunderstorms of 20 hours per year or more at N -
III
Outdoor installations and open warehouses, creating a zone of classes P-III in accordance with the PUE In areas with an average duration of thunderstorms of 20 hours per year or more At 0.12 - zone A III
Buildings and structures of III, IIIa, IIIb, IV, V degrees of fire resistance, in which there are no premises classified according to the PUE to zones of explosive and fire hazardous classes Same At 0.12 - zone A III
Buildings and structures made of light metal structures with combustible insulation (IVa degree of fire resistance), in which there are no premises classified according to the PUE to zones of explosion and fire classes In areas with an average duration of thunderstorms of 10 hours per year or more At 0.12 - zone A III
Small buildings of III-V degrees of fire resistance, located in rural areas, in which there are no premises classified according to the PUE to zones of explosion and fire classes In areas with an average duration of thunderstorms of 20 hours per year or more for III, IIIa, IIIb, IV, V degrees of fire resistance at N -
III
Computing center buildings, including those located in urban areas In areas with an average duration of thunderstorms of 20 hours per year or more Zone B II
Livestock and poultry buildings and structures of III-V degrees of fire resistance: for cattle and pigs for 100 heads or more, for sheep for 500 heads or more, for poultry for 1000 heads or more, for horses for 40 heads or more In areas with an average duration of thunderstorms of 40 hours per year or more Zone B III
Smoke and other pipes of enterprises and boiler houses, towers and derricks for all purposes with a height of 15 m or more In areas with an average duration of thunderstorms of 10 hours per year or more -
III
Residential and public buildings, the height of which is more than 25 m higher than the average height of surrounding buildings within a radius of 400 m, as well as detached buildings more than 30 m high, more than 400 m away from other buildings In areas with an average duration of thunderstorms of 20 hours per year or more Zone B III
Free-standing residential and public buildings in rural areas with a height of more than 30 m Same Zone B III
Public buildings of III-V degrees of fire resistance for the following purposes: preschool institutions, schools and boarding schools, hospitals of medical institutions, dormitories and canteens of health and recreation institutions, cultural, educational and entertainment institutions, administrative buildings, railway stations, hotels, motels and campsites Same Zone B III
Open entertainment facilities (auditory halls of open cinemas, grandstands of open stadiums, etc.) Same Zone B III
Buildings and structures that are monuments of history, architecture and culture (sculptures, obelisks, etc.) Same Zone B III
Category I lightning protection
see point 2.1. in RD 34.21.122-87. A prerequisite is the provision of a type A protection zone in accordance with the requirements of Annex 3.II category of lightning protection
As a material for the manufacture of lightning protection mesh, steel wire with a diameter of at least 6 mm is used. A structure with a cell spacing of no more than 6x6 m is laid on the roof of the building over or under refractory materials. Metal structures rising above the roof of the building must be attached to the lightning protection mesh, and not metal structures must be equipped with additional lightning protection devices, also fixing them with the "mesh".
Structures with metal trusses, the roofs of which are built using refractory materials, do not require the installation of lightning protection devices. The metal roof of the buildings itself acts as a lightning rod. At the same time, it is necessary to equip all non-metallic elements of the object of protection rising above the roof with lightning protection devices. Down conductors are mounted from a metal roof or lightning protection mesh with a step of 25 m along the perimeter of the building. For all types of lightning rods used to protect buildings of category II, it is mandatory to fulfill the requirement of paragraph 2.6 in RD 34.21.122-87.III category of lightning protection
If possible, metal structures of the protected object itself are used as a down conductor. A prerequisite for this is a continuous electrical connection in the joints of structures with the rest of the elements of the external lightning protection system (lightning rods and ground electrodes). Down conductors located outside the building must be mounted at a distance of no more than 3 m from the entrances or in places not accessible to people.
Normative documents on the organization of lightning protection of ground facilities do not provide for any requirements for the distance between a separate lightning rod and the object of protection, its underground utilities. When using a lightning protection mesh for buildings of category III, it is necessary to provide for a step of its cells no more than 12 x 12m.4. Protection zones of rod and wire lightning rods
Under the protection zone is understood the area of a given geometry in the vicinity of the lightning rod, on which the probability of a direct lightning strike into an object located there will not exceed a given value.
To ensure the lightning protection of the building at the level of required reliability, the entire volume of the protected object must be located in the protection zone of the lightning rod.
A single lightning protection mast provides a protection zone for the structure in the form of a circular cone with a height h0 
5. Selecting the type of lightning rod
Carrying out lightning protection of buildings with the help of rod and cable lightning rods, they are positioned in such a way that the object would be entirely in their protection zones, calculated for each type of lightning rod according to CO 153-343.21.122-2003.
When choosing a lightning protection mesh, it is important to consider that the mesh spacing (mesh sizes) is determined by the lightning protection categories, see RD 34.21.122-87.
For complex lightning protection of objects, combined types can be used, for example, wire rods. Often, the "mesh" is combined with rod lightning rods, which provides quite reliable protection.
Cable lightning rods are chosen to protect very extended objects. In terms of economic parameters, the arrangement of structures by them is comparable to rod lightning protection devices, however, during operation they proved to be less reliable.Types and features
The nuances of the calculation
Mounting
Rope extension is possible only by mooring with an overlap length of at least one and a half meters. In order to protect the cable from being burned by lightning current and to make the grounding of the supports more reliable, a suspension insulator with a so-called spark gap is used.Comparison with other options
