Snip installation of lightning protection from a metal strip. What documents regulate the lightning protection device for buildings and structures. General provisions and design principles

Lightning protection is a set of measures aimed at reducing material damage and injury to people from lightning strikes.

Roof lightning protection device

Dangers from a lightning strike:

complete or partial destruction of structures and buildings, engineering networks;
failure of electrical appliances located in the lightning strike zone;
injury and death of living organisms that are inside or near the structure that was struck by lightning.

What is lightning?

Lightning poses a great danger to both humans and buildings and structures. Lightning is a high-power electrical discharge that, when hit, can destroy structures, disable electrical appliances and power lines. When erecting high-quality lightning rods, the number of injuries and destruction of structures and engineering networks is reduced. The nature of lightning is such that upon reaching the lower layers of the atmosphere, the strike falls on the highest point within the radius of the danger zone.

The main condition for the formation of thunderclouds is a rapid change in temperature and high humidity. Under such conditions, negatively charged cloud clusters appear in the atmosphere. Due to electrostatic induction on a moving charged cloud in the atmosphere, discharges are formed. Those. conditionally, it is a capacitor, and the distance between the cloud and the earth's surface is the gap between the plates. Over time, the electric field strength increases, and high structures (trees), ionizing the air, reduce the specific resistance and provoke lightning strikes to the ground.

Due to this property, structures have been developed that are able to take a blow and divert dangerous potential into the ground without damage and fires. Standards for the design and installation of lightning protection: PUE, instruction RD 34.21.122-87, GOST R IEC 62561.2-2014, SNiP 3.05.06-85. Lightning rods are a mandatory measure of protection against lightning strikes if the building is not located in an urban high-rise building, if there is a reservoir nearby, etc.

Striking factors of lightning

Primary. It is characterized by thermal and mechanical effects. Direct lightning strikes a building or power line, resulting in a fire hazard. Without additional equipment, it is impossible to protect yourself from the primary factor. A lightning protection device is required.

Lightning action: melting of metal structures (thickness less than 4 mm), partial or complete destruction of buildings made of concrete, brick and stone (due to mechanical impact). Rapid heating of structures causes stress in them, provoking explosions (instruction RD 34.21.122-87).

Secondary. When a discharge hits nearby structures, electromagnetic induction appears in the power grid, which can disable electrical appliances. To protect against a secondary factor, it is enough to disconnect all electronic devices from the network. This factor is impossible without the manifestation of the primary influence (instruction RD 21.122-87).

It appears as:

electrostatic induction, expressed by sparks between the metal surfaces of structures, electrical appliances. Caused by static charges from clouds on ground structures;
electromagnetic induction. Occurs during a lightning discharge due to a changing magnetic field. Induction causes heat closed loops, accompanied by heating that is not dangerous for equipment and people.

Because Lightning is an electric charge that moves along the path of least resistance. Protection against lightning strikes must effectively divert charges to the ground. When lightning strikes lightning rods, the current goes into the ground without causing damage to buildings inside and outside the protection zone.

The type of lightning protection depends on the type of building, electrical appliances, the type of grounding of the electrical network, the frequency of thunderstorms in the selected climatic region.

Rope lightning protection of the building

Buildings and structures, according to the need to build lightning protection, are divided into categories:

Category 1. Explosion and fire in buildings dangerous substances are not stored permanently. Hazardous substances are processed and stored openly or in unpackaged containers. The occurrence of explosions in such structures is accompanied by significant destruction and loss of life (RD).
Category 2. In buildings, hazardous substances are stored in sealed containers. Explosive mixtures are formed only in case of industrial accidents. The explosion is accompanied by minor damage, without human casualties (RD).
Category 3. A direct lightning strike causes fires, destruction of a large degree of buildings and engineering networks, damage to people and animals. Such buildings should be effective protection from direct lightning strikes (RD).

Protection Options

Active. The new kind protection against lightning strikes. Artificially attracts discharges to itself with the help of a built-in ionizer (RD).

Active lightning protection

Advantages:

100% performance;
exclusion of the appearance of a secondary factor of lightning damage.

Disadvantages:

Price.

Passive lightning rods. The peculiarity of the work is that lightning strikes it does not occur in all cases.

Disadvantages:

does not work in all cases.

Advantages:

high reliability;
low cost of work;
the possibility of building manually.

Type of protection (RD and GOST R IEC 62561.2-2014)

External type

Protects buildings from the primary factor of lightning impact - from destruction and fires. Allows you to intercept the discharges, and divert the blow to the ground.

During a lightning strike, lightning rods take over the current and divert it through the system to the ground, where the energy is completely dissipated.

External lightning protection of the building

Requirements for lightning protection - with proper design and installation of the system, complete safety is ensured outside and inside the building.

Types of external protection (instruction RD 34.21.122-87):

mesh lightning rod;
lightning rod;
stretched lightning wire.

Cable construction for protection against lightning strikes

Components of lightning protection (RD and GOST R IEC 62561.2-2014):

Lightning rods are structures that intercept the discharge. Usually made of metal of stainless steel, copper or aluminium.
Descents (down conductors) - metal releases, through which the discharge is diverted from the lightning rod to the ground electrode.
An earthing conductor is a protective earthing device consisting of conductive materials that are in contact with earth. Has an outer and underground part(ground loop).

internal type

Protects houses from a secondary factor of influence of an electric current. Consists of a number of devices (SPD). The purpose of the devices is to prevent the failure of household electrical appliances from overvoltages in the mains, which are caused by lightning strikes.

Overvoltages can be caused by direct (when lightning strikes a building or a power transmission line) and indirect (strike in the immediate vicinity of structures or power lines) lightning discharges.

According to the type of hit, several types of surges are distinguished:

1 type. Caused by direct blows, represent the greatest danger.
2 type. Caused by indirect current shocks, the stored energy is 20 times lower than in type 1 surges.

SPD types according to GOST R 50571.26-2002

1 type. Able to withstand current loads completely from the received lightning discharge. Type 1 SPDs are recommended for installation in countryside with overhead power lines in buildings with lightning rods, in separate buildings located in close proximity to high objects.

2 type. Used in conjunction with type 1. Devices are not able to withstand lightning strikes. Permissible voltage surge is 1.5..1.7 kV.
3 type. SPD type 3 is used after protection of the 1st and 2nd stage. Designed for installation at the consumer: surge protectors, automation devices on household electrical appliances (boilers, etc.).

SPDs are installed together with circuit breakers to prevent burnout and fire in the electrical panel. Long-term overvoltages can damage the SPD.

Introductory automata with a rated operating current of less than 25A can act as SPD protection (GOST R 50571.26-2002).

Lightning protection is connected according to two schemes:

With safety priority. SPD is not destroyed, lightning protection works smoothly. When lightning strikes, it completely turns off consumers.
With continuity priority. In this case, switching off consumers is unacceptable; lightning strikes turn off lightning protection.

When installing devices, it is necessary to maintain a minimum allowable distance of 10 m, which provides the necessary inductance for the operation of the machine of a higher level.

Type 1 surge protective device

Joint installation of SPDs of 1st and 2nd stages in one housing is possible (GOST R 50571.26-2002). For each grounding system, SPDs have been developed in accordance with their design.

Rod lightning rod

It is installed on the roof of buildings so that the structure is higher than all other points. To maintain the aesthetics of the appearance of the house, the lightning rod should be installed on a free-standing support (tree).

As a lightning rod (according to the PUE) they use: angle steel 50x50, round steel with a cross section of more than 25mm 2.

As a lightning rod, it is also permissible to use a metal pipe with a diameter of 40..50 mm with cuts welded at both ends.

The number of lightning rods is chosen according to the calculation, depending on the size of the structure. For houses with an area of less than 200 m 2, one design is sufficient. For buildings with an area of more than 200 m 2, it is necessary to install two rods, the distance between which should not exceed 10 m. To prevent current from flowing into the house, the rod is fixed on the roof with insulating materials, for example, wooden blocks, etc.

Earthworks for lightning protection

Rope lightning rods

They are used to protect buildings and structures of great length and high-voltage power lines, i.e. for narrow, long structures.

The main element is a metal cable, which is suspended along the entire length of the roof. It is fixed on wooden supports so that there is no contact with the roof surface. On all sides of the building, down conductors are constructed in the amount of at least 2.

For lightning rods use galvanized steel rope TK with the required design section, but not less than 35 mm 2. The design of lightning rods from a cable is carried out taking into account the area on ice and the requirements of the PUE. The coverage area of this type of lightning rod has the form of a trihedral prism, the upper face of which will be a stretched cable on the roof of buildings. If the roof has a large slope or several structures different heights, it is necessary to install rod lightning rods due to the reduction of financial costs.

In the case of rod and wire lightning rods, the distance from the nearest structures must be at least 15 m, or the installation is supposed to be on different sides of the building.

Mesh lightning rods

They are made of steel (aluminum) wire with a cross section of 6 mm in the form of cells with an area of \u200b\u200bnot more than 150 mm 2 so that the mesh does not have points of contact with the roof (6..8 cm from the surface). The mesh is stretched over the entire roof area along insulated supports, with a total size of at least 6x6m. Down conductors are laid at the corners of the building for every 25 m of the perimeter.

All protruding parts of the structure must fall into the protective area of lightning rods. All ventilation and flue pipes must be included in the lightning protection zone, provided that they are protected by special structures.

Separately standing lightning rods apply in the following cases:

it is necessary to protect several buildings with one structure;
it is impossible to equip lightning rods on the roof.

Metal lightning rods are used to protect buildings over 30 m high.

Down conductors

The task of the down conductors is to effectively discharge the charge from the lightning rod to the grounding structure.

As down conductors, a steel wire with a diameter of 6 mm, a metal tape with a wall of at least 2 mm and a width of 30 mm are used.

Provided that the walls do not contain conductive elements, the down conductors are fixed along the wall in any place, subject to the proximity clearance to doors and windows. To fix the structure, bolting and welding are used.

The number of current collectors is taken based on the number of lightning rods. For rods, they are taken equal to the number of rods, for mesh and cable, the minimum number is at least 2.

grounding

One circuit is being built with a common ground electrode system. The simplest design is a triangular ground loop. Peaks - vertical electrodes hammered into the ground to a depth of 3m. The optimal distance between the peaks is 3m.

Horizontal grounding (connecting the vertices of a triangle into a single structure) is laid to a depth of at least 0.5 m. The connection is made exclusively by welding.

Installation of lightning protection

For private houses, passive rod lightning protection is most often constructed.

Preparatory work:

First of all, it is necessary to take all measurements: the width, height of the house, the estimated radius of protection (for lightning rods).
After that, it is necessary to determine the height of the lightning rod, the method of fixing it.
The length of the down conductor is calculated after determining the installation point of the lightning rod. The path from the point of impact to ground should be the shortest possible, therefore, the design of complex structures is not recommended, connections in the form of a ring are prohibited.
The grounding element, according to the PUE and SNiP, must be located at a distance of at least 1 m from the wall of the building, must not cross footpaths and the porch.

After making accurate calculations of the length and grounding structure, it is necessary to proceed directly to construction and installation work.

Grounding device:

For grounding, angle steel 50x50 (GOST 8509-93) or flat steel 40x4 (GOST 103-76) is used. Round steel can also be used.
The ground loop is made in the form of a polygon, into the vertices of which vertical electrodes with a length of at least 2 m are hammered. The vertices of the triangle are connected by strip steel welding into a single metal structure.

Lightning rod installation:

Installed on the roof of the building wooden poles, installation on which completely eliminates the contact of the rod with the roof of the building.

Down conductor installation:

The last stage is the installation of a down conductor and the connection of all lightning protection elements. Down conductors are mounted on special structures - skates, which also exclude contact with the surface of the house.
After completion of excavation and construction and installation works, it is necessary to measure the resistance of the lightning rod and the compliance of the obtained values with the calculated ones.
For wooden houses the process of building a lightning rod system is similar. All elements of the lightning protection structure must be 150 mm away from the wall plane.

Lightning protection for wooden houses

Internal protection of buildings and structures

SPDs protect electrical equipment from surges and large inductive loads.

Sources of impulse surges during a thunderstorm:

DSL (direct lightning strikes) into the lightning protection device, strikes into nearby power lines;
lightning strikes near objects.

SPDs are installed in residential and administrative buildings, industrial facilities. It is mandatory to include an SPD in the power supply scheme in country houses, with one- and two-story buildings in the area (GOST R 50571.26-2002).

Benefits of using an SPD:

reliable protection against impulse surges;
low cost devices.

The principle of operation of the devices is based on the nonlinearity of the current-voltage characteristic. With a significant increase in voltage, the varistor retains the ability to pass electric current.

Devices fail after several protection trips. The SPD must be checked after each operating cycle.

Fuses for protection against heavy currents are included in the circuit in front of the SPD.

In networks up to 1 kV, three stages of overvoltage protection are provided:

SPD 1 stage. Class B. Designed for current surges up to 100 kA. Installed in prepared metal cabinets in the input-distribution device or on the main electrical panel.
SPD 2nd stage. Class C. Amplitude of impulse currents is 15..20 kA. They are used in areas completely protected from direct lightning strikes. The installation is provided in switchboards at the inputs to buildings and premises.
SPD 3 stages. Class D. Designed to protect equipment from residual overvoltage currents. Installation is provided directly in front of electrical appliances, the minimum allowable distance is 5m.

SPD selection parameters according to GOST R 50571.26-2002:

rated voltage of the network;
long-term permissible operating voltage of the protective device - the highest voltage that can be applied before the protection operation time;
varistor leakage current;
protection response time;
pulse current;
maximum voltage value when current flows through the SPD;
classification stress;
maximum pulse discharge current - the maximum current load, during the passage of which the device remains operational.

The distance delay between devices is necessary to guarantee the time delay and provide an impulse for the operation of the next protection stage:

between SPDs of the 1st and 2nd degree - at least 10m;
between SPDs 2 and 3 stages - at least 5 m;
between SPDs of the 3rd class (between themselves) - at least 1m.

Each SPD must be connected to the grounding device by a separate conductor.

A 3-stage SPD protects devices at a distance of up to 10 m. If it is necessary to protect the network further, the installation of the following device is required.

For reliable protection of buildings and structures, it is necessary to use internal and external protection from lightning. Surge protection devices will not perform their functions if there are no effective lightning rods.

Video about lightning protection

For country houses a high-quality lightning protection system is extremely important, because helps to prevent the destruction of houses and damage to property. The construction of passive lightning protection systems can be done by hand, in accordance with the requirements of the PUE. Active defenses require high qualifications and cannot be arranged without the help of specialists.

INSTRUCTIONS
FOR LIGHTNING PROTECTION OF BUILDINGS AND STRUCTURES

RD 34.21.122-87

Moscow GNIEI them. Krzhizhanovsky, 1987

Moscow GOSENERGONADZOR 1995

Look Clarification of the Department for Supervision in the Electric Power Industry of Rostekhnadzor on the joint application of the "Instructions for lightning protection of buildings and structures" (RD 34.21.122-87) and "Instructions for lightning protection of buildings, structures and industrial communications" (SO 153-34.21.122-2003)

3. LIGHTNING CONSTRUCTIONS

APPENDIX 1 BASIC TERMS

APPENDIX 2 CHARACTERISTICS OF THE INTENSITY OF LIGHTNING ACTIVITY AND THE LIGHTNING PROBLEM OF BUILDINGS AND STRUCTURES

APPENDIX 3 LIGHTNING PROTECTION ZONES

MANUAL TO "INSTRUCTIONS FOR LIGHTNING PROTECTION OF BUILDINGS AND STRUCTURES"

1. BRIEF DATA ON LIGHTNING DISCHARGE AND THEIR PARAMETERS

2. CHARACTERISTICS OF THUNDERING ACTIVITY

3. NUMBER OF LIGHTNING STRIKES OF GROUND FACILITIES

4. DANGEROUS EFFECTS OF LIGHTNING

5. CLASSIFICATION OF PROTECTED OBJECTS

6. MEANS AND METHODS OF LIGHTNING PROTECTION

7. PROTECTIVE ACTION AND LIGHTNING PROTECTION ZONES

8. APPROACH TO REGULATION OF LIGHTNING PROTECTION GROUNDING

9. EXAMPLES OF PERFORMANCE OF LIGHTNING PROTECTION OF VARIOUS OBJECTS

Developer State Research Energy Institute. G.M. Krzhizhanovsky

Instructions for the device of lightning protection of buildings and structures. RD 34.21.122-87

The instruction establishes a set of measures and devices to ensure the safety of people (farm animals), protect buildings, structures, equipment and materials from explosions, fires, destruction when exposed to lightning. The instruction is obligatory for all ministries and departments.

Designed for professionals designing buildings and structures.

FOREWORD

Requirements of this Instruction binding on all ministries and departments.

The instruction establishes the necessary set of measures and devices designed to ensure the safety of people (farm animals), the protection of buildings, structures, equipment and materials from explosions, fires and destruction, possible under the influence of lightning.

The instruction must be observed when developing projects for buildings and structures.

The instruction does not apply to the design and installation of lightning protection for power lines, the electrical part of power plants and substations, contact networks, radio and television antennas, telegraph, telephone and radio broadcasting lines, as well as buildings and structures whose operation is associated with the use, production or storage of gunpowder and explosives.

This Instruction regulates lightning protection measures performed during construction and does not exclude the use of additional lightning protection means inside the building and structure during reconstruction or installation of additional technological or electrical equipment.

When developing projects of buildings and structures, in addition to the requirements of the Instruction, the requirements for the implementation of lightning protection of other applicable norms, rules, instructions, state standards should be taken into account.

With the introduction of this Instruction, the "Instruction for the design and installation of lightning protection of buildings and structures" SN 305-77 becomes invalid.

INSTRUCTIONS FOR LIGHTNING PROTECTION OF BUILDINGS AND STRUCTURES (RD 34.21.122-87) 1

1. GENERAL PROVISIONS

1.1. In accordance with the purpose of buildings and structures, the need for lightning protection and its category, and when using rod and wire lightning rods - the type of protection zone are determined by Table. 1 depending on the average annual duration of thunderstorms at the location of a building or structure, as well as on the expected number of lightning strikes per year. The lightning protection device is mandatory with the simultaneous fulfillment of the conditions recorded in columns 3 and 4 of Table. one.

The assessment of the average annual duration of thunderstorms and the expected number of lightning strikes of buildings or structures is made according to Annex 2; construction of protection zones of various types - according to Annex 3.

1 This Instruction was developed by the State Energy Research Institute. G.M. Krzhizhanovsky Ministry of Energy of the USSR, agreed with the State Construction Committee of the USSR (letter No. ACH-3945-8 of July 30, 1987) and approved by the Main Technical Directorate of the USSR Ministry of Energy. With the introduction of this Instruction, the "Instruction for the design and installation of lightning protection of buildings and structures" SN 305-77 becomes invalid.

Table I

no.	Buildings and constructions	Location	Type of protection zone when using rod and wire lightning rods	Category of lightning protection
1	2	3	4	5
1	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	BUT	I
2	The same classes B-Ia, B-Ib, B-IIa		With the expected number of lightning strikes per year of a building or structure N	II
3	Outdoor installations that create a zone of class B-Ig according to the PUE	Throughout the USSR	B	II
4	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- A	III
5	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 ( paragraph 2.30)
6	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 0.1 2 - A	III
7	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 0.1 2 - A
8	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 0.02 2 - A	III
9	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 ( paragraph 2.30)
10	Computing center buildings, including those located in urban areas	In areas with an average duration of thunderstorms of 20 hours per year or more	B	II
11	Livestock and poultry buildings and structures of III-V degrees of fire resistance: for large cattle and pigs for 100 heads and more, for sheep for 500 heads and more, for poultry for 1000 heads and more, for horses for 40 heads and more	In areas with an average duration of thunderstorms of 40 hours per year or more	B	III
12	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	B	III ( paragraph 2.31)
13	Residential and public buildings, the height of which is more than 25 m higher than the average height of the surrounding buildings within a radius of 400 m, as well as detached buildings with a height of more than 30 m, more than 400 m away from other buildings	In areas with an average duration of thunderstorms of 20 hours per year or more	B	III
14	Free-standing residential and public buildings in rural areas with a height of more than 30 m	Same	B	III
15	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	B	III
16	Open entertainment facilities (auditory halls of open cinemas, grandstands of open stadiums, etc.)	Same	B	III
17	Buildings and structures that are monuments of history, architecture and culture (sculptures, obelisks, etc.)	Same	B	III

1.2. Buildings and structures classified by the lightning protection device to categories I and II must be protected from direct lightning strikes, its secondary manifestations and the introduction of high potential through ground (above-ground) and underground metal communications.

Outdoor installations classified as category II according to the lightning protection device must be protected from direct strikes and secondary manifestations of lightning.

Outdoor installations classified as category III according to the lightning protection device must be protected from direct lightning strikes.

Inside buildings large area(width more than 100 m) it is necessary to carry out potential equalization measures.

1.3. For buildings and structures with premises requiring lightning protection devices of I and II or I and III categories, lightning protection of the entire building or structure should be carried out according to category I.

If the area of premises of category I lightning protection is less than 30% of the area of all premises of the building, lightning protection of the entire building is allowed to be carried out according to category II, regardless of the category of other premises. At the same time, at the entrance to the premises of category I, protection against the drift of high potential through underground and ground (above-ground) communications should be provided, which is carried out in accordance with paragraphs. 2.8 and 2.9 .

1.4. For buildings and structures with premises requiring lightning protection devices of categories II and III, lightning protection of the entire building or structure should be carried out according to category II.

If the area of premises of category II lightning protection is less than 30% of the area of all premises of the building, lightning protection of the entire building is allowed to be carried out according to category III. At the same time, at the entrance to the premises of category II, protection against the drift of high potential through underground and ground (overground) communications, carried out in accordance with paragraphs. 2.22 and 2.23 .

1.5. For buildings and structures, at least 30% total area which fall on premises requiring lightning protection devices of category I, II or III, lightning protection of this part of buildings and structures must be carried out in accordance with clause 1.2.

For buildings and structures, more than 70% of the total area of \u200b\u200bwhich are premises that are not subject to lightning protection according to tab. one, and the rest of the building is made up of premises of category I, II or III of lightning protection, only protection against the introduction of high potentials through communications introduced into premises subject to lightning protection should be provided: for category I - in accordance with paragraphs. 2.8 , 2.9 ; for categories II and III - by connecting communications to the grounding device of electrical installations that complies with the instructions clause 1.7, or to the reinforcement of the reinforced concrete foundation of the building (subject to the requirements clause 1.8). The same connection must be provided for internal communications (not introduced from outside)

1.6. In order to protect buildings and structures of any category from direct lightning strikes, existing tall structures (chimneys, water towers, searchlight masts, overhead power lines, etc.) as well as lightning rods of other nearby structures should be used as natural lightning rods as much as possible.

If a building or structure partially fits into the protection zone of natural lightning rods or neighboring objects, protection against direct lightning strikes should be provided only for the rest of its unprotected part. If, during the operation of a building or structure, the reconstruction or dismantling of neighboring facilities will lead to an increase in this unprotected part, the corresponding changes in protection against direct lightning strikes must be carried out before the start of the next thunderstorm season; if the dismantling or reconstruction of neighboring facilities is carried out during the thunderstorm season, temporary measures should be provided for this time to ensure protection from direct lightning strikes of the unprotected part of the building or structure.

1.7. As lightning protection grounding conductors, it is allowed to use all electrical installation grounding conductors recommended by the "Electrical Installation Rules", with the exception of zero wires overhead power lines with voltage up to 1 kV.

1.8. Reinforced concrete foundations of buildings, structures, outdoor installations, supports of lightning rods should, as a rule, be used as lightning protection grounding conductors, provided that a continuous electrical connection is provided through their reinforcement and its connection to embedded parts by welding.

Bituminous and bitumen-latex coatings are not an obstacle to such use of foundations. In medium and highly aggressive soils, where reinforced concrete is protected from corrosion by epoxy and other polymer coatings, as well as when soil moisture is less than 3%, it is not allowed to use reinforced concrete foundations as ground electrodes.

Artificial grounding should be placed under asphalt pavement or in rarely visited places (on lawns, at a distance of 5 m or more from dirt roads and pedestrian roads, etc.).

1.9. Equalization of potentials inside buildings and structures with a width of more than 100 m should occur due to continuous electrical connection between the bearing intra-workshop structures and reinforced concrete foundations, if the latter can be used as ground electrodes in accordance with clause 1.8.

Otherwise, laying inside the building in the ground at a depth of at least 0.5 m of extended horizontal electrodes with a cross section of at least 100 mm 2 should be provided. Electrodes should be laid at least every 60 m across the width of the building and connected at its ends on both sides to the external ground loop.

1.10. In frequently visited open areas with an increased risk of lightning strikes (near monuments, TV towers and similar structures more than 100 m high), potential equalization is carried out by connecting down conductors or fittings of the structure to its reinforced concrete foundation at least 25 m along the perimeter of the base of the structure.

If it is impossible to use reinforced concrete foundations as ground electrodes under the asphalt surface of the site at a depth of at least 0.5 m, every 25 m, radially diverging horizontal electrodes with a cross section of at least 100 mm 2 should be laid, connected to the ground electrodes protecting the structure from direct lightning strikes.

1.11. During the construction of high buildings and structures on them during the thunderstorm period, starting from a height of 20 m, it is necessary to provide for the following temporary lightning protection measures. At the top mark of the object under construction, lightning rods should be fixed, which through metal structures or down conductors freely descending along the walls should be connected to the ground electrodes specified in paragraphs. 3.7 and 3.8 . The type B protection zone of lightning rods should include all outdoor areas where people can be during construction. Connections of lightning protection elements can be welded or bolted. As the height of the object under construction increases, lightning rods should be moved higher.

When erecting high metal structures, their foundations at the beginning of construction must be connected to the ground electrodes specified in paragraphs .. 3.7 and 3.8 .

1.12. Devices and measures for lightning protection that meet the requirements of these standards must be included in the project and schedule for the construction or reconstruction of a building or structure in such a way that the implementation of lightning protection occurs simultaneously with the main construction and installation works.

1.13. Lightning protection devices for buildings and structures must be accepted and put into operation by the beginning finishing works, and in the presence of explosive zones before the start of a comprehensive testing of technological equipment.

At the same time, the corrected during construction and installation project documentation on lightning protection device (drawings and explanatory note) and acts of acceptance of lightning protection devices, including acts on hidden work for connecting grounding conductors to down conductors and down conductors to lightning rods, except for cases when the steel frame of the building is used as down conductors and lightning rods, as well as the results of measuring the resistance to the power frequency current of ground electrodes of separate lightning rods.

1.14. Checking the state of lightning protection devices should be carried out for buildings and structures of I and II categories I once a year before the start of the thunderstorm season, for buildings and structures of category III - at least once every 3 years.

The integrity and corrosion protection of the visible parts of lightning rods and down conductors and the contacts between them, as well as the value of the resistance to current of the industrial frequency of grounding conductors of separate lightning rods, are subject to verification. This value should not exceed the results of the corresponding measurements at the acceptance stage by more than 5 times (clause 1.13). Otherwise, the grounding conductor should be revised.

2. REQUIREMENTS FOR LIGHTNING PROTECTION OF BUILDINGS AND STRUCTURES

set a bookmark

RD 34.21.122-87

INSTRUCTIONS
FOR LIGHTNING PROTECTION OF BUILDINGS AND STRUCTURES

COMPILERS: d.t.s. E.M. Bazelyan - ENIN them. G.M.Krzhizhanovsky, V.I.Polivanov, V.V.Shatrov, A.V.Tsapenko

AGREED by the State Construction Committee of the USSR, letter N АЧ-3945-8 dated 07/30/87

APPROVED by the Main Technical Department of the Ministry of Energy of the USSR on 12.10.87

FOREWORD

The requirements of this Instruction are mandatory for all ministries and departments.

This Instruction establishes the necessary set of measures and devices designed to ensure the safety of people (farm animals), protect buildings, structures, equipment and materials from explosions, fires and destruction, possible under the influence of lightning.

This Instruction must be observed when developing projects for buildings and structures.

This Instruction does not apply to the design and installation of lightning protection for power lines, the electrical part of power plants and substations, contact networks, radio and television antennas, telegraph, telephone and radio transmission lines, as well as buildings and structures whose operation is associated with the use, production or storage of gunpowder and explosives.

When developing projects of buildings and structures, in addition to the requirements of this Instruction, the requirements for the implementation of lightning protection of other applicable norms, rules, instructions, state standards must be taken into account.

With the introduction of this Instruction, the Instruction for the design and installation of lightning protection of buildings and structures (SN 305-77) becomes invalid.

1. GENERAL PROVISIONS

1.1. In accordance with the purpose of buildings and structures, the need for lightning protection and its category, and when using rod and cable lightning rods - the type of protection zone are determined according to Table 1, depending on the average annual duration of thunderstorms at the location of the building or structure, as well as on the expected number of strikes lightning per year. The lightning protection device is obligatory with the simultaneous fulfillment of the conditions recorded in columns 3 and 4 of Table 1.

Table 1

Buildings and constructions	Location	Type of protection zone when using rod and wire lightning rods	Kate- mountain lightning protection

PUE belong to zones of classes B-I and B-II	Throughout the USSR
The same classes B-Ia, B-Ib, B-IIa		With the expected number of lightning strikes per year of a building or structure 1 - zone A; at 1 - zone B
Outdoor installations that create a zone of class B-Ig according to the PUE	Throughout the USSR
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 0.12 and for III-V degrees of fire resistance at 0.022 - zone B; at 2 - zone A
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 0.02		III (clause 2.30)
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
Buildings and structures of III, IIIa, IIIb, IV, V degrees of fire resistance, in which there are no premises related to the PUE		At 0.12 - zone B, at 2 - zone A
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 0.022 - zone B, at 2 - zone A
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 0.1, for IVa fire resistance at 0.02		III (clause 2.30)
Computing center buildings, including those located in urban areas	In areas with an average duration of thunderstorms of 20 hours per year or more
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
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 (clause 2.31)
Residential and public buildings, the height of which is more than 25 m higher than the average height of the 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
Free-standing residential and public buildings in rural areas with a height of more than 30 m
Public buildings of III-V degrees of fire resistance of the following purpose: kindergartens, schools and schools - boarding schools, hospitals of medical institutions, dormitory buildings and canteens of health care and recreation institutions, cultural and educational and entertainment institutions, administrative buildings, railway stations, hotels, motels and campsites
Open entertainment facilities (auditory halls of open cinemas, grandstands of open stadiums, etc.)
Buildings and structures that are monuments of history, architecture and culture (sculptures, obelisks, etc.)

The assessment of the average annual duration of thunderstorms and the expected number of lightning strikes of buildings or structures is made in accordance with the mandatory Appendix 2; construction of protection zones of various types - according to Appendix 3.

Buildings and structures classified as category III according to the lightning protection device must be protected from direct lightning strikes and the introduction of high potential through ground (overground) metal communications. Outdoor installations classified as category II according to the lightning protection device must be protected from direct strikes and secondary manifestations of lightning.

Outdoor installations classified as category III according to the lightning protection device must be protected from direct lightning strikes.

Potential equalization measures must be carried out inside buildings of a large area (more than 100 m wide).

If the area of premises of category I lightning protection is less than 30% of the area of all premises of the building (on all floors), lightning protection of the entire building is allowed to be carried out according to category II, regardless of the category of other premises. At the same time, at the entrance to the rooms of category I, protection against the drift of high potential through underground and ground (overground) communications, carried out in accordance with clauses 2.8 and 2.9 of this Instruction, should be provided.

If the area of the premises of the II category of lightning protection is less than 30% of the area of all premises of the building (on all floors), the lightning protection of the entire building is allowed to be carried out according to the III category. At the same time, at the entrance to the premises of category II, protection against the introduction of high potential through underground and ground (above-ground) communications, carried out in accordance with clauses 2.22 and 2.23 of this Instruction, should be provided.

1.5. For buildings and structures, at least 30% of the total area of \u200b\u200bwhich falls on premises requiring lightning protection devices of category I, II or III, lightning protection of this part of buildings and structures must be performed in accordance with clause 1.2 of this Instruction.

For buildings and structures, more than 70% of the total area of \u200b\u200bwhich are rooms that are not subject to lightning protection according to Table 1, and the rest of the building is made up of rooms of I, II or III categories of lightning protection, only protection against the introduction of high potentials through communications introduced into premises subject to lightning protection: for category I - in accordance with clauses 2.8, 2.9 of this Instruction; for II and III categories - by connecting communications to the grounding device of electrical installations, corresponding to the instructions of clause 1.7 of this Instruction, or to the reinforcement of the reinforced concrete foundation of the building (subject to the requirements of clause 1.8 of this Instruction). The same connection must be provided for internal communications (not introduced from outside).

1.7. It is allowed to use all grounding electrodes of electrical installations recommended by the PUE, with the exception of neutral wires of overhead power lines with voltage up to 1 kV, as lightning protection grounding conductors.

Artificial grounding should be placed under asphalt pavement or in rarely visited places (on lawns, at a distance of 5 m or more from dirt roads and pedestrian roads, etc.).

1.9. Potential equalization inside buildings and structures with a width of more than 100 m should occur due to continuous electrical connection between the bearing intra-workshop structures and reinforced concrete foundations, if the latter can be used as grounding conductors in accordance with clause 1.8 of this Instruction.

Otherwise, laying inside the building in the ground at a depth of at least 0.5 m of extended horizontal electrodes with a cross section of at least 100 mm should be provided. Electrodes should be laid at least every 60 m across the width of the building and connected at its ends on both sides to the external ground loop.

1.10. In frequently visited outdoor areas with an increased risk of lightning strikes (near monuments, TV towers and similar structures more than 100 m high), potential equalization is carried out by connecting the down conductors or fittings of the structure to its reinforced concrete foundation at least 25 m along the perimeter of the base of the structure.

If it is impossible to use reinforced concrete foundations as ground electrodes under the asphalt surface of the site at a depth of at least 0.5 m, every 25 m, radially diverging horizontal electrodes with a cross section of at least 100 mm and a length of 2-3 m should be laid, connected to the ground electrodes protecting the structure from direct lightning strikes.

1.11. During the construction of high buildings and structures on them during the thunderstorm period, starting from a height of 20 m, it is necessary to provide for the following temporary lightning protection measures. At the top mark of the facility under construction, lightning rods should be fixed, which through metal structures or down conductors freely descending along the walls should be connected to the ground electrodes specified in clauses 3.7 and 3.8 of this Instruction. The type B protection zone of lightning rods should include all outdoor areas where people can be during construction. Connections of lightning protection elements can be welded or bolted. As the height of the object under construction increases, lightning rods should be moved higher.

When erecting high metal structures, their foundations at the beginning of construction must be connected to the ground electrodes specified in clauses 3.7 and 3.8 of this Instruction.

1.13. Lightning protection devices for buildings and structures must be accepted and put into operation by the beginning of finishing work, and in the presence of explosive zones - before the start of a comprehensive testing of process equipment.

At the same time, the design documentation for the lightning protection device (drawings and explanatory note) adjusted during construction and installation and acts of acceptance of lightning protection devices, including acts for covert work on connecting ground electrodes to down conductors and down conductors to lightning rods, are drawn up and transferred to the customer, except for cases of using steel the frame of the building as down conductors and lightning rods, as well as the results of measurements of the resistance to the current of the industrial frequency of ground electrodes of separate lightning rods.

1.14. Checking the state of lightning protection devices should be carried out for buildings and structures of categories I and II once a year before the start of the thunderstorm season, for buildings and structures of category III - at least once every three years.

The integrity and corrosion protection of the visible parts of lightning rods and down conductors and the contacts between them, as well as the value of the resistance to current of the industrial frequency of earth electrodes of separate lightning rods, are subject to verification. This value should not exceed the results of the corresponding measurements at the acceptance stage by more than 5 times (see clause 1.13 of this Instruction). Otherwise, carry out an audit of the ground electrode system.

2. REQUIREMENTS FOR LIGHTNING PROTECTION OF BUILDINGS AND STRUCTURES

2.1. Protection against direct lightning strikes of buildings and structures, classified by the lightning protection device to category I, should be carried out by separate rod (Fig. 1) or cable (Fig. 2) lightning rods.

Fig.1. Stand-alone lightning rod:

1 - protected object; 2

Fig.2. Freestanding wire lightning rod:

1 - protected object; 2 - metal communications

These lightning rods must provide a type A protection zone in accordance with the requirements of Appendix 3. This ensures the removal of elements of lightning rods from the protected object and underground metal communications in accordance with clauses 2.3, 2.4, 2.5 of this Instruction.

2.2. The choice of ground electrode for protection against direct lightning strikes (natural or artificial) is determined by the requirements of clause 1.8 of this Instruction.

At the same time, the following designs of ground electrodes are acceptable for stand-alone lightning rods (Table 2):

a) one (or more) reinforced concrete footings at least 2 m long or one (or more) reinforced concrete piles at least 5 m long;

b) one (or more) rack buried in the ground at least 5 m reinforced concrete support with a diameter of at least 0.25 m;

c) reinforced concrete foundation of arbitrary shape with a surface area of contact with the ground of at least 10 m;

d) an artificial grounding conductor, consisting of three or more vertical electrodes with a length of at least 3 m, united by a horizontal electrode, with a distance between the vertical electrodes of at least 5 m. The minimum sections (diameters) of the electrodes are determined according to Table 3.

table 2

grounding conductor		Dimensions, m

Reinforced concrete footboard
Reinforced concrete pile
Steel two-rod: a strip of 40x4 mm in size, rods with a diameter of 10-20 mm
Steel three-rod: strip size 40x4 mm, rods with a diameter of 10-20 mm

Table 3

___________________

* Only for potential equalization inside buildings and for laying external circuits at the bottom of the pit along the perimeter of the building.

2.3. The smallest allowable air distance from the protected object to the support (down conductor) of the rod or cable lightning rod (see Fig. 1 and 2) is determined depending on the height of the building, the design of the ground electrode system and the equivalent electrical resistivity of the soil, Ohm m.

For buildings and structures with a height of not more than 30 m, the smallest allowable distance, m, is:

at 100 Ohm m for a ground electrode of any design, given in clause 2.2 of this Instruction, 3 m;

at 1001000 Ohm m:

for grounding conductors consisting of one reinforced concrete pile, one reinforced concrete foot or recessed rack of a reinforced concrete support, the lengths of which are indicated in clause 2.2, a-b,;

for grounding conductors consisting of four reinforced concrete piles or footboards located at the corners of a rectangle at a distance of 3-8 m from one another, or a reinforced concrete foundation of arbitrary shape with a surface area of contact with the ground of at least 70 m2, or artificial grounding conductors specified in clause 2.2 g of this Instruction, 4 m.

For buildings and structures of greater height, the value defined above must be increased by 1 m for every 10 m of the height of the object above 30 m.

2.4. The smallest allowable distance from the protected object to the cable in the middle of the span (see Fig. 2) is determined depending on the design of the earth electrode, the equivalent soil resistivity, Ohm m and the total length of lightning rods and down conductors.

With a length of 200 m, the smallest allowable distance, m, is:

at 100 Ohm m for a ground electrode of any design, given in clause 2.2 of this Instruction, 3.5 m;

at 1001000 Ohm m:

for grounding conductors consisting of one reinforced concrete pile, one reinforced concrete foot or recessed rack of a reinforced concrete support, the length of which is specified in clause 2.2, a-b of this Instruction, ;

for grounding conductors consisting of four reinforced concrete piles or footboards located at a distance of 3-8 m from one another, or artificial grounding conductors specified in clause 2.2d of this Instruction, 4 m.

With a total length of lightning rods and down conductors of 200-300 m, the smallest allowable distance should be increased by 2 m compared to the values defined above.

2.5. To exclude the entry of high potential into the protected building or structure through underground metal communications (including electric cables for any purpose) grounding conductors for protection against direct lightning strikes should be, if possible, removed from these communications to the maximum distances allowed by technological requirements. The smallest allowable distances (see Fig. 1 and 2) in the ground between grounding conductors for protection against direct lightning strikes and communications introduced into buildings and structures of category I should be, m, with according to clause 2.3 of this Instruction.

2.6. If there are direct gas outlet and breathing pipes on buildings and structures for free removal of gases, vapors and suspensions of explosive concentration into the atmosphere, the area of protection of lightning rods should include the space above the edge of the pipes, limited by a hemisphere with a radius of 5 m.

For gas outlet and breathing pipes equipped with caps or "ganders", the protection zone of lightning rods should include the space above the pipe cut, limited by a cylinder with a height and a radius of:

for gases heavier than air at overpressure inside the plant

less than 5.05 kPa (0.05 atm) = 1 m, = 2 m;

5.05-25.25 kPa (0.05-0.25 atm) = 2.5 m, = 5 m;

for gases lighter than air at excess pressure inside the installation:

up to 25.25 kPa = 2.5 m, = 5 m;

over 25.25 kPa = 5 m, = 5 m.

It is not required to include the space above the edge of pipes in the protection zone of lightning rods: in case of emission of gases of non-explosive concentration; the presence of nitrogen respiration; with constantly burning torches and torches ignited at the time of the release of gases; for exhaust ventilation shafts, safety and emergency valves, the release of gases of explosive concentration from which is carried out only in emergency cases.

2.7. To protect against secondary manifestations of lightning, the following measures should be provided:

a) metal structures and cases of all equipment and apparatus located in the protected building must be connected to the grounding device of electrical installations specified in clause 1.7 of this Instruction, or to the reinforced concrete foundation of the building (subject to the requirements of clause 1.8 of this Instruction). The smallest allowable distances in the ground between this ground electrode and ground electrodes protecting against direct lightning strikes must be in accordance with clause 2.5 of this Instruction;

b) inside buildings and structures between pipelines and other extended metal structures in places of their mutual approach at a distance of less than 10 cm every 20 m, weld or solder jumpers made of steel wire with a diameter of at least 5 mm or steel tape with a cross section of at least 24 mm, for cables with metal sheaths or jumper armor must be made of a flexible copper conductor in accordance with the instructions of SNiP 3.05.06-85;

c) in the joints of elements of pipelines or other extended metal objects transitional resistances of not more than 0.03 ohms for each contact should be provided. If it is impossible to ensure contact with the specified contact resistance using bolted connections, it is necessary to install steel jumpers, the dimensions of which are indicated in subparagraph "b" of this paragraph.

2.8. Protection against the introduction of high potential through underground metal communications (pipelines, cables in outer metal sheaths or pipes) should be carried out by connecting them at the entrance to the building or structure to the reinforcement of its reinforced concrete foundation, and if it is impossible to use the latter as a ground electrode, to an artificial ground conductor, specified in clause 2.2d of this Instruction.

2.9. Protection against the drift of high potential through external ground (overground) metal communications should be carried out by grounding them at the input to the building or structure and on the two communication supports closest to this input. As grounding conductors, reinforced concrete foundations of the building or structure and each of the supports should be used, and if such use is impossible (see clause 1.8 of this Instruction), artificial grounding conductors, in accordance with clause 2.2d of this Instruction.

2.10. The entry into buildings of overhead power lines with a voltage of up to 1 kV, telephone, radio, signaling networks should be carried out only with cables at least 50 m long with metal armor or sheath or cables laid in metal pipes.

At the entrance to the building, metal pipes, armor and cable sheaths, including those with an insulating coating of a metal sheath (for example, AASHv, AASHp), must be attached to the reinforced concrete foundation of the building or (see clause 1.8 of this Instruction) to the artificial ground electrode indicated in clause 2.2d of this Instruction.

At the point of transition of the overhead power line into the cable, the metal armor and cable sheath, as well as the pins or hooks of the overhead line insulators, must be connected to the ground electrode specified in clause 2.2d of this Instruction. Pins or hooks of insulators on the support of the overhead power transmission line, closest to the place of transition to the cable, must be connected to the same ground electrode.

In addition, at the point of transition of the overhead power line into the cable between each core of the cable and grounded elements, closed air spark gaps 2-3 mm long must be provided or a valve arrester should be installed low voltage, for example, RVN-0.5.

Protection against the introduction of high potentials through overhead power lines with voltages above 1 kV, introduced into substations located in the protected building (intrashop or attached), must be carried out in accordance with the PUE.

2.11. Protection against direct lightning strikes of category II buildings and structures with a non-metal roof should be performed by stand-alone or installed on the protected object by rod or wire lightning rods, providing a protection zone in accordance with the requirements of Table 1, clause 2.6 and Appendix 3 of this Instruction. When installing lightning rods at the facility, at least two down conductors must be provided from each rod lightning rod or each post of a cable lightning rod. With a roof slope of not more than 1:8, an lightning protection mesh can also be used, subject to the mandatory fulfillment of the requirements of clause 2.6 of this Instruction.

The lightning protection mesh must be made of steel wire with a diameter of at least 6 mm and laid on the roof from above or under fireproof or slow-burning insulation or waterproofing. The grid cell spacing should be no more than 6x6 m. The grid nodes should be connected by welding. The metal elements protruding above the roof (pipes, shafts, ventilation devices) must be connected to the lightning protection mesh, and the protruding non-metallic elements must be equipped with additional lightning rods, also connected to the lightning protection mesh.

The installation of lightning rods or the imposition of a lightning protection mesh is not required for buildings and structures with metal trusses provided that fireproof or slow-burning insulation and waterproofing are used in their roofs.

On buildings and structures with a metal roof, the roof itself should be used as a lightning rod. In this case, all protruding non-metallic elements must be equipped with lightning rods attached to the roof metal, and the requirements of clause 2.6 of this Instruction must be observed.

Down conductors from a metal roof or lightning protection mesh must be laid to grounding conductors at least every 25 m along the perimeter of the building.

2.12. When laying a lightning protection grid and installing lightning rods on the protected object, wherever possible, metal structures of buildings and structures (columns, trusses, frames, fire escapes, etc., as well as reinforcement of reinforced concrete structures) should be used as down conductors, provided that continuous electrical connection in the joints of structures and fittings with lightning rods and grounding conductors, performed, as a rule, by welding.

Down conductors laid along the outer walls of buildings should be located no closer than 3 m from the entrances or in places not accessible to people.

2.13. In all possible cases (see clause 1.8 of this Instruction), reinforced concrete foundations of buildings and structures should be used as grounding conductors for protection against direct lightning strikes.

If it is impossible to use the foundations, artificial grounding conductors are provided:

in the presence of rod and cable lightning rods, each down conductor is connected to a ground electrode that meets the requirements of clause 2.2d of this Instruction;

in the presence of a lightning protection mesh or a metal roof, an external contour of the following design is laid along the perimeter of a building or structure:

in soils with an equivalent resistivity of 500 Ohm m, with a building area of more than 250 m, a contour of horizontal electrodes laid in the ground at a depth of at least 0.5 m is made, and with a building area of less than 250 m, this one vertical or horizontal beam electrode 2-3 m long;

in soils with a resistivity of 5,001,000 Ohm m, with a building area of more than 900 m, it is sufficient to make a circuit only from horizontal electrodes, and with a building area of less than 900 m, at least two vertical or horizontal beam electrodes 2-3 long are welded to this circuit at the points of connection of down conductors m at a distance of 3-5 m from one another.

In large buildings, the external ground loop can also be used to equalize the potential inside the building in accordance with the requirements of clause 1.9 of this Instruction.

In all possible cases, the grounding conductor of protection against direct lightning strikes must be combined with the grounding conductor of electrical installations in accordance with the instructions in clause 1.7 of this Instruction.

2.14. When installing free-standing lightning rods, the distance from them through the air and in the ground to the protected object and underground utilities introduced into it is not standardized.

2.15. Outdoor installations containing combustible and liquefied gases and flammable liquids should be protected from direct lightning strikes as follows:

a) buildings of installations made of reinforced concrete, metal buildings of installations and individual tanks with a roof metal thickness of less than 4 mm must be equipped with lightning rods installed on the protected object or separately standing;

b) metal cases of installations and individual tanks with a roof metal thickness of 4 mm or more, as well as individual tanks with a capacity of less than 200 m3, regardless of the thickness of the roof metal, as well as metal casings of heat-insulated installations, it is enough to connect to the ground electrode.

2.16. For tank farms containing liquefied gases with a total capacity of more than 8000 m3, as well as for tank farms with metal and reinforced concrete buildings containing flammable gases and flammable liquids, with a total capacity of a group of tanks of more than 100 thousand m3, protection against direct lightning strikes should, as a rule, be be performed by separate lightning rods.

2.17. Treatment facilities are subject to protection against direct lightning strikes if the flash point of the product contained in the wastewater exceeds its operating temperature by less than 10 °C. The protection zone of lightning rods should include a space, the base of which extends beyond the boundaries of the treatment plant by 5 m in each direction from its walls, and the height is equal to the height of the structure plus 3 m.

2.18. If there are gas outlet or breathing pipes on outdoor installations or tanks (ground or underground) containing flammable gases or flammable liquids, then they and the space above them (see clause 2.6 of this Instruction) must be protected from direct lightning strikes. The same space is protected above the cut of the neck of the tanks, into which the product is poured openly on the unloading rack. Breathing valves and the space above them, limited by a cylinder 2.5 m high with a radius of 5 m, are also subject to protection against direct lightning strikes.

For tanks with floating roofs or pontoons, the protection zone of lightning rods should include a space bounded by a surface, any point of which is 5 m away from the flammable liquid in the annular gap.

2.19. For outdoor installations listed in clauses 2.15-2.18 of this Instruction, as grounding conductors for protection against direct lightning strikes, if possible, use reinforced concrete foundations of these installations or supports of free-standing lightning rods, or make artificial grounding conductors consisting of one vertical or horizontal electrode with a length of at least 5 m

These ground electrodes, located at least 50 m along the perimeter of the installation base, must be connected to the casings of outdoor installations or down conductors of lightning rods installed on them, the number of connections is at least two.

2.20. To protect buildings and structures from secondary manifestations of lightning, the following measures should be provided:

a) the metal cases of all equipment and apparatus installed in the protected building (structure) must be connected to the grounding device of electrical installations that meets the instructions in clause 1.7 of this Instruction, or to the reinforced concrete foundation of the building (subject to the requirements of clause 1.8 of this Instruction);

b) inside the building between pipelines and other extended metal structures in the places of their convergence at a distance of less than 10 cm every 30 m jumpers must be made in accordance with the instructions of clause 2.7b of this Instruction;

c) in flange connections of pipelines inside the building, at least four bolts should be properly tightened for each flange.

2.21. To protect outdoor installations from secondary manifestations of lightning, the metal cases of the devices installed on them must be connected to the grounding device of the electrical equipment or to the grounding conductor for protection against direct lightning strikes.

On tanks with floating roofs or pontoons, at least two flexible steel jumpers must be installed between the floating roofs or pontoons and the metal body of the tank or down conductors of lightning rods installed on the tank.

2.22. Protection against the introduction of high potential through underground utilities is carried out by connecting them at the input to the building or structure to the ground electrode of electrical installations or protection against direct lightning strikes.

2.23. Protection against the introduction of high potential through external ground (overground) communications is carried out by connecting them at the input to the building or structure to the ground electrode system of electrical installations or protection against direct lightning strikes, and at the communication support closest to the input - to its reinforced concrete foundation. If it is impossible to use the foundation (see clause 1.8 of this Instruction), an artificial grounding conductor must be installed, consisting of one vertical or horizontal electrode with a length of at least 5 m.

2.24. Protection against the drift of high potential through overhead power lines, telephone, radio and signaling networks must be carried out in accordance with clause 2.10 of this Instruction.

2.25. Protection against direct lightning strikes of buildings and structures classified as category III according to the lightning protection device must be carried out by one of the methods specified in clause 2.11 of this Instruction, in compliance with the requirements of clauses 2.12 and 2.14 of this Instruction.

In this case, in the case of using a lightning protection mesh, the step of its cells should be no more than 12x12 m.

2.26. In all possible cases (see clause 1.7 of this Instruction), reinforced concrete foundations of buildings and structures should be used as grounding conductors for protection against direct lightning strikes.

If it is impossible to use them, artificial grounding is performed:

each down conductor from rod and wire lightning rods must be connected to a ground electrode system consisting of at least two vertical electrodes with a length of at least 3 m, united by a horizontal electrode with a length of at least 5 m;

when using a grid or a metal roof as lightning rods, an external circuit consisting of horizontal electrodes should be laid along the perimeter of the building in the ground at a depth of at least 0.5 m. In soils with an equivalent resistivity of 5,001,000 Ohm m and with a building area of less than 900 m2, one vertical or horizontal beam electrode 2–3 m long should be welded to this circuit at the points of connection of down conductors.

The minimum allowable sections (diameters) of artificial grounding electrodes are determined according to Table 3.

In buildings of a large area (more than 100 m wide), the external ground loop can also be used to equalize the potentials inside the building in accordance with the requirements of clause 1.9 of this Instruction.

In all possible cases, the ground electrode for protection against direct lightning strikes must be combined with the ground conductor of the electrical installation specified in chapter 1.7 of the PUE.

2.27. When protecting buildings for cattle and stables with free-standing lightning rods, their supports and grounding conductors should be located no closer than 5 m from the entrance to the buildings.

When installing lightning rods or laying a grid on a protected structure, a reinforced concrete foundation (see clause 1.8 of this Instruction) or an external contour laid along the perimeter of the structure under the asphalt or concrete blind area in accordance with the instructions of clause 2.26 of this Instruction.

Metal structures, equipment and pipelines located inside the building, as well as electrical potential equalization devices, must be connected to the grounding conductors for protection against direct lightning strikes.

2.28. Protection against direct lightning strikes of metal sculptures and obelisks, specified in clause 17 of Table 1 of this Instruction, is ensured by their connection to the grounding conductor of any design, given in clause 2.26 of this Instruction.

If there are frequently visited sites near such high-altitude structures, potential equalization should be performed in accordance with clause 1.10 of this Instruction.

2.29. Lightning protection of outdoor installations containing flammable liquids with a vapor flash point above 61 ° C and corresponding to clause 6 of Table 1 of this Instruction must be performed as follows:

a) buildings of installations made of reinforced concrete, as well as metal buildings of installations and tanks with a roof thickness of less than 4 mm, must be equipped with lightning rods installed on the protected structure or separately standing;

b) metal casings of installations and tanks with a roof thickness of 4 mm or more should be connected to the ground electrode. The designs of grounding switches must meet the requirements of clause 2.19 of this Instruction.

2.30. Small buildings located in rural areas with non-metal roofs, corresponding to those specified in clauses 5 and 9 of Table 1 of this Instruction, are subject to protection against direct lightning strikes using one of the simplified methods:

a) if there are trees at a distance of 3-10 m from the structure that are 2 times or more higher than its height, taking into account all objects protruding on the roof (chimneys, antennas, etc.), a down conductor must be laid along the trunk of the nearest tree , the upper end of which protrudes above the crown of the tree by at least 0.2 m. At the base of the tree, the down conductor must be connected to the ground electrode;

b) if the ridge of the roof corresponds to the highest height of the building, a cable lightning rod should be suspended above it, rising above the ridge by at least 0.25 m. Wooden planks fixed on the walls of the building can serve as supports for the lightning rod. Down conductors are laid on both sides along the end walls of the building and connected to the ground electrodes. With a building length of less than 10 m, the down conductor and grounding conductor can be made only on one side;

c) in the presence of a chimney towering above all elements of the roof, a rod lightning rod with a height of at least 0.2 m should be installed above it, a down conductor should be laid along the roof and wall of the building and connected to the ground electrode system;

d) if there is a metal roof, it should be connected to the ground electrode at least at one point; in this case, external metal stairs, drains, etc. can serve as down conductors. All metal objects protruding on it must be attached to the roof.

In all cases, lightning rods and down conductors should be used. minimum diameter 6 mm, and as a ground electrode - one vertical or horizontal electrode 2-3 m long with a minimum diameter of 10 mm, laid at a depth of at least 0.5 m.

Connections of elements of lightning rods are allowed welded and bolted.

2.31. Protection against direct lightning strikes of non-metallic pipes, towers, towers with a height of more than 15 m should be carried out by installing on these structures at their height:

up to 50 m - one rod lightning rod with a height of at least 1 m;

from 50 to 150 m - two rod lightning rods with a height of at least 1 m, connected at the upper end of the pipe;

more than 150 m - at least three rod lightning rods 0.2-0.5 m high or a steel ring with a cross section of at least 160 mm should be laid along the upper end of the pipe.

Can also be used as a lightning rod protective cap, installed on a chimney, or metal structures such as antennas installed on TV towers.

With a structure height of up to 50 m from lightning rods, one down conductor should be laid; with a structure height of more than 50 m, down conductors must be laid at least every 25 m along the perimeter of the structure base, their minimum number is two.

Cross-sections (diameters) of down conductors must meet the requirements of Table 3, and in areas with high gas content or aggressive emissions into the atmosphere, the diameters of down conductors must be at least 12 mm.

Running metal ladders, including those with bolted links, and other vertical metal structures can be used as down conductors.

On the reinforced concrete pipes reinforcing bars connected along the height of the pipe by welding, twisting or overlapping should be used as down conductors; in this case, the laying of external down conductors is not required. The connection of the lightning rod with the armature must be carried out at least at two points.

All connections of lightning rods with down conductors must be made by welding.

For metal pipes, towers, towers, installation of lightning rods and down conductors is not required.

As ground electrodes for protection against direct lightning strikes of metal and non-metal pipes, towers, towers, their reinforced concrete foundations should be used in accordance with clause 1.8 of this Instruction. If it is not possible to use foundations, each down conductor must be provided with an artificial ground electrode made of two rods connected by a horizontal electrode (see Table 2); with a perimeter of the base of the structure not more than 25 m, an artificial ground electrode can be made in the form of a horizontal circuit laid at a depth of at least 0.5 m and made of a circular electrode (see Table 3). When reinforcing bars are used as down conductors, their connections to artificial ground electrodes must be made at least every 25 m with a minimum number of connections equal to two.

When erecting non-metallic pipes, towers, towers, the metal structures of the mounting equipment (cargo-passenger and mine hoists, jib crane, etc.) must be connected to grounding conductors. In this case, temporary lightning protection measures for the construction period may not be performed.

2.32. To protect against the introduction of high potential through external ground (overground) metal communications, they must be connected to the ground electrode of electrical installations or protection against direct lightning strikes at the entrance to the building or structure.

2.33. Protection against the drift of high potential through overhead power lines with voltage up to 1 kV and communication and signaling lines must be carried out in accordance with the EMP and departmental regulations.

3. LIGHTNING CONSTRUCTIONS

3.1. Supports of rod lightning rods should be designed for mechanical strength as free-standing structures, and supports of lightning rods - taking into account the tension of the cable and the effect of wind and ice loads on it.

3.2. Supports of free-standing lightning rods can be made of steel of any grade, reinforced concrete or wood.

3.3. Rod lightning rods must be made of steel of any grade with a cross section of at least 100 mm and a length of at least 200 mm and protected from corrosion by galvanizing, tinning or painting.

Rope lightning rods must be made of steel multiwire ropes with a cross section of at least 35 mm.

3.4. Connections of lightning rods with down conductors and down conductors with grounding conductors should be carried out, as a rule, by welding, and if hot work is unacceptable, it is allowed to make bolted connections with a transition resistance of not more than 0.05 Ohm, with mandatory annual control of the latter before the start of the thunderstorm season.

3.5. Down conductors connecting lightning rods of all types with grounding conductors should be made of steel with dimensions not less than those indicated in Table 3.

3.6. When installing lightning rods on the protected object and it is impossible to use the metal structures of the building as down conductors (see clause 2.12 of this Instruction), the down conductors must be laid to the ground electrodes along the outer walls of the building in the shortest possible ways.

3.7. It is allowed to use any structures of reinforced concrete foundations of buildings and structures (pile, strip, etc.) as natural lightning protection ground electrodes (subject to the requirements of clause 1.8 of this Instruction).

Permissible dimensions of single structures of reinforced concrete foundations used as ground electrodes are given in Table 2.

Appendix 1

Basic terms

1. Direct lightning strike (lightning strike)- direct contact of a lightning channel with a building or structure, accompanied by the flow of lightning current through it.

2. Secondary Lightning Manifestation- pointing potentials to metal elements structures, equipment, in non-closed metal circuits, caused by nearby lightning discharges and creating a spark hazard inside the protected object.

3. High potential skid- transfer to a protected building or structure along long metal communications (underground, ground and overhead pipelines, cables, etc.) electric potentials arising from direct and close lightning strikes and creating the danger of sparking inside the protected object.

4. Lightning rod- a device that perceives a lightning strike and diverts its current to the ground.

In general, a lightning rod consists of: support; lightning rod that directly perceives a lightning strike; a down conductor through which the lightning current is transmitted to the ground; grounding conductor, which ensures the spreading of the lightning current in the ground.

In some cases, the functions of a support, lightning rod and down conductor are combined, for example, when using metal pipes or trusses as a lightning rod.

5. Lightning rod protection zone- space inside which a building or structure is protected from direct lightning strikes with a reliability not lower than a certain value. The surface of the protection zone has the least and constant reliability; In the depth of the protection zone, reliability is higher than on its surface.

Type A protection zone has a reliability of 99.5% or more, and type B - 95% or more.

6. Structurally, lightning rods are divided into the following types:

rod- with a vertical arrangement of the lightning rod;

cable (extended)- with a horizontal arrangement of the lightning rod, fixed on two grounded supports;

grids- multiple horizontal lightning rods intersecting at right angles and laid on the protected object.

7. Stand-alone lightning rods- these are those whose supports are installed on the ground at some distance from the protected object.

8. Single lightning rod- this is a single design of a rod or wire lightning rod.

9. Double (multiple) lightning rod- these are two (or more) rod and cable lightning rods forming a common protection zone.

10. Lightning protection grounding- one or more conductors buried in the ground, designed to divert lightning currents into the ground or limit overvoltages that occur on metal cases, equipment, communications in case of close lightning discharges. Grounding conductors are divided into natural and artificial.

11. Natural grounding- metal and reinforced concrete structures of buildings and structures buried in the ground.

12. Artificial grounding- specially laid in the ground contours of strip or round steel; concentrated structures consisting of vertical and horizontal conductors.

Annex 2

Characteristics of the intensity of thunderstorm activity and
lightning resistance of buildings and structures

The average annual duration of thunderstorms in hours at an arbitrary point on the territory of the USSR is determined from the map (Fig. A2.1), or from regional maps of the duration of thunderstorms approved for some regions of the USSR, or from average long-term (about 10 years) data from the weather station closest to the location buildings or structures.

Fig.A2.1. Map of the average annual duration of thunderstorms in hours for the territory of the USSR

The calculation of the expected number of lightning strikes per year is made according to the formulas:

for concentrated buildings and structures (chimneys, derricks, towers)

for buildings and structures of rectangular shape

where - highest altitude buildings or structures, m;

The average annual number of lightning strikes per 1 km of the earth's surface (specific density of lightning strikes into the ground) at the location of a building or structure;

Width and length of a building or structure, respectively, m.

For buildings and structures of complex configuration, the width and length of the smallest rectangle in which the building or structure can be inscribed in the plan are considered as and.

For an arbitrary point on the territory of the USSR, the specific density of lightning strikes to the ground is determined based on the average annual duration of thunderstorms in hours as follows:

Annex 3

Protection zones of lightning rods

1. Single rod lightning rod

The protection zone of a single rod lightning rod with a height is a circular cone (Fig. A3.1), the top of which is at a height of . At ground level, the protection zone forms a circle with a radius of . The horizontal section of the protection zone at the height of the protected structure is a circle with a radius .

Fig. A3.1. Protection zone of a single rod lightning rod:

1 2 - the same at ground level

1.1. The protection zones of single rod lightning rods with a height of 150 m have the following overall dimensions.

For zone B, the height of a single rod lightning rod at known values and can be determined by the formula

1.2. The protection zones of single rod lightning rods with a height of 150 m600 m have the following overall dimensions:

2. Double rod lightning rod

2.1. The protection zone of a double rod lightning rod with a height of 150 m is provided in Fig. A3.2. The end areas of the protection zone are defined as zones of single rod lightning rods, the overall dimensions of which , , , are determined by the formulas of clause 1.1 of this appendix for both types of protection zones.

Fig. A3.2. Protection zone of a double rod lightning rod:

1 - the boundary of the protection zone at the level ; 2 - the same at the level ; 3 - the same at ground level

The internal areas of the protection zones of a double rod lightning rod have the following overall dimensions.

With the distance between the rod lightning rods for the construction of zone A, the lightning rods should be considered as single ones.

With the distance between the rod lightning rods for the construction of zone B, the lightning rods should be considered as single ones.

With known values of and (at 0), the height of the lightning rod for zone B is determined by the formula

2.2. The protection zone of two rod lightning rods of different heights and 150 m is shown in Fig. A3.3. dimensions end areas of protection zones , , , , , are determined by the formulas of clause 1.1 of this appendix, as for the protection zones of both types of a single rod lightning rod. The overall dimensions of the inner area of the protection zone are determined by the formulas:

Where the values and are calculated according to the formulas for clause 2.1 of this appendix.

Fig. A3.3. Protection zone of two rod lightning rods of different heights:

1 - 2 - the same at ground level

For two lightning rods of different heights, the construction of zone A of a double rod lightning rod is carried out at , and zone B - at . With corresponding large distances between lightning rods, they are considered as single ones.

3. Multiple rod lightning rod

The protection zone of a multiple lightning rod (Fig. A3.4) is defined as the protection zone of pairwise taken adjacent lightning rods with a height of 150 m (see clauses 2.1, 2.2 of this appendix).

Fig. A3.4. Protection zone (in plan) of a multiple lightning rod:

1 - boundary of the protection zone at the level ; 2 - the same at ground level

The main condition for the protection of one or more objects with a height with reliability corresponding to the reliability of zone A and zone B is the fulfillment of inequality 0 for all lightning rods taken in pairs. Otherwise, the construction of protection zones must be performed for single or double rod lightning rods, depending on the fulfillment of the conditions of clause 2 of this appendix.

4. Single wire lightning rod

The protection zone of a single wire lightning rod with a height of 150 m is shown in Fig. A3.5, where is the height of the wire in the middle of the span. Taking into account the sag of the cable with a cross section of 35-50 mm, with a known height of the supports and the length of the span, the height of the cable, m, is determined by:

At 120150 m.

Fig. A3.5. Protection zone of a single wire lightning rod:

1 - boundary of the protection zone at the level ; 2 - the same at ground level

The protection zones of a single wire lightning rod have the following overall dimensions.

For a zone of type B, the height of a single wire lightning rod with known values and is determined by the formula

5. Double wire lightning rod

5.1. The protection zone of a double wire lightning rod with a height of 150 m is shown in Fig. A3.6. Dimensions , , for protection zones A and B are determined according to the corresponding formulas of clause 4 of this appendix. The rest of the zone sizes are determined as follows.

Fig. A3.6. Protection zone of a double wire lightning rod:

1 - the boundary of the protection zone at the level ; 2 - the same at the level ; 3 - the same at ground level

With a distance between the wire lightning rods for the construction of zone A, the lightning rods should be considered as single ones.

With a distance between the wire lightning rods for the construction of zone B, the lightning rods should be considered as single ones. With known values and (at ), the height of the lightning rod for zone B is determined by the formula

5.2. The protection zone of two cables of different heights is shown in Fig. P3.7. Dimensions , , , , , are determined by the formulas of clause 4 of this appendix as for a single wire lightning rod. Formulas are used to determine the dimensions:

where and are calculated by the formulas for clause 5.1 of this appendix.

Fig. A3.7. Protection zone of two wire lightning rods of different heights

Manual for the Instructions for the installation of lightning protection of buildings and structures (RD 34.21.122-87)

This manual aims to clarify and specify the main provisions of the Instructions for the installation of lightning protection of buildings and structures (RD 34.21.122-87), as well as to acquaint specialists involved in the development and design of lightning protection of various objects with the existing ideas about the development of lightning and its parameters that determine dangerous impact on human and material values. Examples of lightning protection of buildings and structures of various categories are given in accordance with the requirements of RD 34.21.122-87.

1. Brief information about lightning discharges and their parameters

Lightning is an electrical discharge several kilometers long that develops between a thundercloud and the ground or any ground structure.

A lightning discharge begins with the development of a leader - a weakly glowing channel with a current of several hundred amperes. In the direction of the leader's movement - from the cloud down or from the ground structure up - the lightning is divided into descending and ascending. Downward lightning data has been accumulating for a long time in several regions the globe. Information about ascending lightning appeared only in recent decades, when systematic observations began on the lightning resistance of very high structures, for example, the Ostankino television tower.

The leader of a descending lightning appears under the action of processes in a thundercloud, and its appearance does not depend on the presence of any structures on the earth's surface. As the leader moves towards the ground, counter leaders directed towards the cloud can be excited from ground objects. The contact of one of them with the descending leader (or the contact of the latter with the surface of the earth) determines the location of the lightning strike to the ground or some object.

Ascending leaders are excited from high grounded structures, at the tops of which the electric field increases sharply during a thunderstorm. The very fact of the emergence and sustainable development of an ascending leader determines the place of defeat. On flat terrain, ascending lightning strikes objects more than 150 m high, and in mountainous areas they are excited from peaked relief elements and structures of lower height and therefore are observed more often.

Let us first consider the development process and the parameters of downward lightning. After the establishment of a through leader channel, the main stage of the discharge follows - the rapid neutralization of the leader charges, accompanied by a bright glow and an increase in current to peak values ranging from a few to hundreds of kiloamperes. In this case, an intense heating of the channel (up to tens of thousands of kelvins) and its shock expansion occur, which is perceived by ear as a thunderclap. The main stage current consists of one or more successive pulses superimposed on the continuous component. Most current pulses have a negative polarity. The first pulse, with a total duration of several hundred microseconds, has a front length of 3 to 20 μs; the peak value of the current (amplitude) varies widely: in 50% of cases (average current) it exceeds 30 kA, and in 1-2% of cases it exceeds 100 kA. Approximately in 70% of downward negative lightning, the first pulse is followed by subsequent ones with lower amplitudes and front length: the average values are 12 kA and 0.6 μs, respectively. In this case, the steepness (rate of rise) of the current at the front of subsequent pulses is higher than for the first pulse.

The current of the continuous component of downward lightning varies from a few to hundreds of amperes and exists throughout the entire flash, lasting an average of 0.2 s, and in rare cases 1-1.5 s.

The charge carried during the entire lightning flash varies from units to hundreds of coulombs, of which 5-15 C falls on the share of individual impulses, and 10-20 C on the continuous component.

Downward lightning with positive current pulses are observed in about 10% of cases. Some of them have a shape similar to the shape of negative pulses. In addition, registered positive impulses with significantly larger parameters: a duration of about 1000 µs, a front length of about 100 µs, and a transferred charge of 35 C on average. They are characterized by variations in current amplitudes over a very wide range: with an average current of 35 kA, in 1-2% of cases, amplitudes of more than 500 kA may appear.

The accumulated actual data on the parameters of downward lightning do not allow us to judge their differences in different geographical regions.

Ascending lightning develops as follows. After the ascending leader has reached the thundercloud, the discharge process begins, accompanied in approximately 80% of cases by currents of negative polarity. Currents of two types are observed: the first is continuous pulseless up to several hundred amperes and a duration of tenths of a second, carrying a charge of 2-20 C; the second is characterized by the superimposition of short pulses on the long pulseless component, the amplitude of which is on average 10–12 kA and exceeds 30 kA only in 5% of cases, and the transferred charge reaches 40 C. These impulses are similar to the subsequent impulses of the main stage of the downward negative lightning.

In mountainous areas, ascending lightning is characterized by longer continuous currents and larger transferred charges than in the plains. At the same time, the variations in the pulse components of the current in the mountains and on the plain differ little. To date, no relationship has been found between ascending lightning currents and the height of the structures from which they are excited. Therefore, the parameters of ascending lightning and their variations are estimated to be the same for any geographic regions and object heights.

In RD 34.21.122-87, data on the parameters of lightning currents are taken into account in the requirements for the designs and dimensions of lightning protection equipment. For example, the minimum allowable distances from lightning rods and their grounding conductors to objects of category I (clauses 2.3-2.5 *) are determined from the condition of lightning rods being struck by downward lightning with an amplitude and steepness of the current front within 100 kA and 50 kA / μs, respectively. This condition corresponds to at least 99% of downstream lightning strikes.

2. Characteristics of thunderstorm activity

The intensity of thunderstorm activity in various geographical locations can be judged from the data of an extensive network of meteorological stations on the frequency and duration of thunderstorms recorded in days and hours per year from audible thunder at the beginning and end of a thunderstorm. However, a more important and informative characteristic for assessing the possible number of objects struck by lightning is the density of downstream lightning strikes per unit of the earth's surface.

The density of lightning strikes into the ground varies greatly across the regions of the globe and depends on geological, climatic and other factors. At general trend As this value increases from the poles to the equator, for example, it sharply decreases in deserts and increases in regions with intensive evaporation processes. The influence of the relief is especially great in mountainous areas, where lightning fronts mainly propagate along narrow corridors, therefore, within a small area, sharp fluctuations in the density of discharges into the ground are possible.

On the whole, throughout the globe, the density of lightning strikes varies from almost zero in the subpolar regions to 20-30 discharges per 1 km of earth per year in humid tropical zones. For the same region, variations from year to year are possible, therefore, for a reliable assessment of the density of discharges into the ground, long-term averaging is necessary.

Currently, a limited number of locations around the globe are equipped with lightning counters, and for small areas, direct estimates of the density of discharges to the ground are possible. On a massive scale, registration of the number of lightning strikes into the ground is still impossible due to laboriousness and lack of reliable equipment.

3. Number of lightning strikes on ground structures

According to the requirements of Table 1 of RD 34.21.122-87, for a number of objects, the expected number of lightning strikes is an indicator that determines the need for lightning protection and its reliability. Therefore, it is necessary to have a way to evaluate this value at the design stage of the object. It is desirable that this method takes into account the known characteristics of thunderstorm activity and other information about lightning.

When counting the number of strikes by downward lightning, the following representation is used: a towering object takes on discharges that, in its absence, would hit the earth's surface of a certain area (the so-called retraction surface). This area is circular for a lumped object (vertical pipe or tower) and rectangular for an extended object such as an overhead power line. The number of hits on an object is equal to the product of the contraction area and the density of lightning discharges at its location. For example, for a concentrated object

Where is the contraction radius;

The average annual number of lightning strikes per 1 km of the earth's surface.

For an extended object with length

The available statistics of damage to objects of different heights in areas with different duration of thunderstorms made it possible to roughly determine the relationship between the radius of contraction and the height of the object. Despite a significant spread, on average it is possible to accept .

The above ratios form the basis of the formulas for calculating the expected number of lightning strikes of concentrated objects and objects with given dimensions in Appendix 2 of RD 34.21.122-87. The lightning resistance of objects is directly dependent on the density of lightning discharges into the ground and, accordingly, on the regional duration of thunderstorms in accordance with Appendix 2 data. It can be assumed that the probability of hitting an object increases, for example, with an increase in the amplitude of the lightning current, and depends on other parameters of the discharge. However, the available damage statistics were obtained by methods (photographing lightning strikes, recording with special counters) that do not allow one to distinguish the influence of other factors, except for the intensity of thunderstorm activity.

The protective effect of a lightning rod is based on the property of lightning being more likely to strike higher and well-grounded objects compared to nearby objects of lower height. Therefore, the lightning rod, which rises above the protected object, is assigned the function of intercepting lightning, which, in the absence of a lightning rod, would strike the object. Quantitatively, the protective effect of a lightning rod is determined through the probability of a breakthrough - the ratio of the number of lightning strikes to a protected object (the number of breakthroughs) to the total number of strikes to the lightning rod and the object.

There are several ways to estimate the probability of a breakthrough, based on different physical concepts of the processes of lightning strike. RD 34.21.122-87 uses the results of calculations using a probabilistic method that relates the probability of hitting a lightning rod and an object with the spread of downward lightning trajectories without taking into account variations in its currents.

According to the accepted design model, it is impossible to create an ideal protection against direct lightning strikes, which completely excludes breakthroughs to the protected object. However, in practice, the mutual arrangement of the object and the lightning rod is feasible, providing a low probability of a breakthrough, for example, 0.1 and 0.01, which corresponds to a decrease in the number of damage to the object by about 10 and 100 times compared to an unprotected object. For most modern facilities, such protection levels provide a small number of breakthroughs over their entire service life.

Above, we considered an industrial building with a height of 20 m and dimensions in terms of 100x100 m, located in an area with a thunderstorm duration of 40-60 hours per year; if this building is protected by lightning rods with a breakthrough probability of 0.1, it can be expected to have no more than one breakthrough in 50 years. However, not all breakthroughs in equally dangerous for the protected object, for example, ignitions are possible at high currents or carried charges, which are not found in every lightning discharge. Consequently, one hazardous impact can be expected on this facility for a period that is certainly more than 50 years, or for most industrial facilities of II and III categories, no more than one hazardous impact for the entire time of their existence. With a breakthrough probability of 0.01 in the same building, no more than one breakthrough in 500 years can be expected - a period far exceeding the life of any industrial facility. Such a high level of protection is justified only for category I facilities that pose a constant threat of explosion.

By performing a series of calculations of the probability of a breakthrough in the vicinity of the lightning rod, it is possible to construct a surface that is the geometric location of the vertices of protected objects, for which the probability of a breakthrough is a constant value. This surface is the outer boundary of the space, called the protection zone of the lightning rod; for a single rod lightning rod this boundary is the side surface of a circular cone, for a single cable it is a gable flat surface.

Typically, 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 allows you to build a protection zone for rod and wire lightning rods with an arbitrary value of the breakthrough probability, that is, 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 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, the 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.

The calculation method of the breakthrough probability has been developed only for downward lightning, mainly striking objects up to 150 m high. Therefore, in RD 34.21.122-87, formulas for constructing protection zones for single and multiple rod and wire lightning rods are limited to a height of 150 m. To date, the volume of actual data on susceptibility to descending lightning objects of greater height is very small and for the most part refers to the Ostankino television tower. Based on photographic recordings, it can be argued that downward lightning breaks more than 200 m below its top and strikes the ground at a distance of about 200 m from the base of the tower. If we consider the Ostankino television tower as a rod lightning rod, it can be concluded that the relative dimensions of the protection zones of lightning rods with a height of more than 150 m are sharply reduced with an increase in the height of the lightning rods.

Given the limited actual data on the impact of ultra-high objects, RD 34.21.122-87 includes formulas for constructing protection zones only for lightning rods with a height of not more than 150 m.

The method for calculating protection zones against damage by ascending lightning has not yet been developed. However, according to observational data, it is known that ascending discharges are excited from pointed objects near the top of tall structures and hinder the development of other discharges with more low levels. Therefore, for such tall objects as reinforced concrete chimneys or towers, first of all, protection against mechanical destruction of concrete during the excitation of ascending lightning is provided, which is carried out by installing rod or ring lightning rods that provide the maximum possible excess over the top of the object (see paragraph 2.31).

This manual contains nomograms for determining the heights of rod C and cable T of single and double lightning rods that provide protection zones A and B (Fig. 1 and 2). The use of these nomograms, built in accordance with the calculation formulas and notation of Appendix 3 of RD 34.21.122-87

Until recently, for lightning protection grounding conductors, the impulse resistance to the spreading of lightning currents was normalized: its maximum allowable value was taken to be 10 Ohm for buildings and structures of categories I and II and 20 Ohm for buildings and structures of category III. At the same time, it was allowed to increase the impulse resistance up to 40 Ohm in soils with a specific resistance of more than 500 Ohm m, while simultaneously removing lightning rods from objects of category I by a distance that guarantees against breakdown in air and in the ground. For outdoor installations, the maximum allowable impulse resistance of ground electrodes was assumed to be 50 ohms.

The impulse resistance of the grounding conductor is a quantitative characteristic of complex physical processes during the spreading of lightning currents in the ground. Its value differs from the resistance of the ground conductor during the spreading of industrial frequency currents and depends on several parameters of the lightning current (amplitude, steepness, front length), which vary over a wide range. With an increase in the lightning current, the impulse resistance of the ground electrode drops, and in the possible range of distribution of lightning currents (from units to hundreds of kiloamperes), its value can decrease by 2-5 times.

When designing a grounding conductor, it is impossible to predict the values of lightning currents that will flow through it, and therefore it is impossible to estimate in advance the corresponding values of impulse resistances. Under these conditions, the rationing of ground electrodes according to their impulse resistance has obvious inconveniences. It is more reasonable to choose specific designs of grounding conductors according to following condition. Impulse resistance of grounding conductors in the entire possible range of lightning currents should not exceed the specified maximum allowable values.

Such rationing was adopted in paragraphs 2.2, 2.13, 2.26, Table 2: for a number of typical structures, impulse resistances were calculated for fluctuations in lightning currents from 5 to 100 kA and, based on the results of calculations, a selection of ground electrodes was carried out that satisfies the accepted condition.

At present, reinforced concrete foundations are common and recommended designs of grounding conductors. They are subject to an additional requirement - the exclusion of mechanical destruction of concrete during the spreading of lightning currents through the foundation. Reinforced concrete structures withstand high densities of lightning currents spreading through the reinforcement, which is associated with the short duration of this spreading. Single reinforced concrete foundations (piles with a length of at least 5 m or footboards with a length of at least 2 m) are capable of withstanding lightning currents of up to 100 kA without destruction, according to this condition, Table 2 of RD 34.21.122-87 specifies the allowable dimensions of single reinforced concrete ground electrodes. For large foundations with a correspondingly larger reinforcement surface, a current density dangerous for concrete destruction is unlikely for any possible lightning currents.

Rationing the parameters of ground electrodes according to their typical designs has a number of advantages: it corresponds to the unification of reinforced concrete foundations accepted in construction practice, taking into account their widespread use as natural ground electrodes; when choosing lightning protection, it is not required to perform calculations of impulse resistances of grounding conductors, which reduces the amount of design work.

9. Examples of execution of lightning protection of various objects*

(Fig.3-10)

________________

* Developed by VNIPI Tyazhpromelektroproekt, Giprotruboprovod Institute and GIAP.

Fig.3. Lightning protection of a category I building with a free-standing double rod lightning rod (300 Ohm m, 4 m, 6 m):

1 - the border of the protection zone; 2 - ground electrodes - footboards of the foundation; 3 - protection zone at around 8.0 m

Fig.4. Lightning protection of a category I building with a free-standing wire lightning rod (300 Ohm m, 4 m, 6 m, 3.5 m):

1 - rope; 2 - the border of the protection zone; 3 - input of an underground pipeline; 4 - limit of distribution of explosive concentration; 5 - reinforcement connections performed by welding; 6 - reinforced concrete foundation; 7 - embedded elements for connecting equipment; 8 5 5 Series 17. Documents on
supervision in the electric power industry. Issue 27. -
M.: JSC "NTC "Industrial safety", 2006

A really working lightning rod was invented about 200 years ago by American President Benjamin Franklin.

To date, actions aimed at protecting structures from lightning are regulated by the DSTU B V.2.5-38:2008 standard. It defines the requirements for lightning rods.

Any lightning rod consists of three main parts:

Lightning rod (takes on a lightning strike);

Down conductor (conducts current to ground);

Grounding (discharges electrical potential to the ground).

Home lightning protection device

In this case, the lightning rod can be of three types:

Rod;

Linear;

Reticulate.

1. A rod lightning rod is a metal rod (tube, angle, rectangle) with a sufficient cross-sectional area of 1-2 cm2 or more. Its length is at least 0.25 m, but, as a rule, from 0.5 m to 2 m. The rod lightning rod is ideal for all types of metal roofs.

The lightning rod must be installed at such a height that a fully protected object falls into the protection zone (like a conditional cone). To do this, the diameter of the base of the cone must be no more than three times the height. For lightning rods of this type, specially installed masts, tops tall trees. The upper end of the lightning rod protrudes above the crown of the tree by at least 0.5 m. The tree must be located no further than 10 m from the building. The lightning rod can be installed on a mast, which is mounted on top point building roofs. The least reliable has, relatively speaking, the surface of the protection zone. In the depth of the cone, it is higher, while the sharper the cone, the higher the degree of protection.

The upper end of the lightning rod a, b. steel wire; in. bar; d. water pipe; d, f. steel strip and corner; 1. soldered bandage; 2. welding; 3. Rivets

The easiest way to calculate the height of the lightning rod is as follows: the lifting height of the lightning rod is equal to the protective horizontal distance from it (3 m lightning rod protects 3 m, 7 m - 7 m, etc.). At the same time, you can calculate the protection radius of a lightning rod for a house using the following formula (h is the distance from the peak of the lightning rod to the highest point of the house):

The lightning rod is installed on a pole, the thickness of which should be 10-15 cm, writes iBud.ua. The pole is attached to the roof of the house. The upper end of the lightning rod is made of the same diameter as the rest of its parts. Larger diameter wire can be used (maximum thickness 14 mm). For the upper end of the lightning rod, use a steel angle, strips, pipes (recommended section 50-60 mm2). From the wire at the top, it is best to make a fixed loop, weld or flatten the pipe.

As noted, you can fix the monlie receiver on the roof of the house, a television mast, a weather vane, or a growing tree nearby. If the installation of the lightning rod is carried out on a tree, then the fastening is carried out using synthetic material. In this case, the house must fall into the protective cone. If the lightning rod is installed on the chimney, then you need to take care of a reliable fastening. The wind can blow the lightning rod off the chimney.

Installation of lightning protection on a tree

Rod lightning rod

2. Linear lightning rod - a cable stretched along the roof ridge with a cross section of at least 0.5 cm. Such lightning protection is used for houses with a slate or wooden roof.

The cable is pulled along the roof ridge and fixed on wooden rods. In this case, each end of the cable is connected to ground. Down conductors are laid on each side of the cable along the walls of the house in protective pipes and connected to ground electrodes. The height of the cable above the roof ridge must be at least 0.5 m.

Linear lightning rod

Mesh lightning rod

Methods for connecting parts of a lightning rod

3. A mesh lightning rod is a mesh of wire or reinforcement with a cell spacing of 6–12 m (the minimum cell spacing is 3 m, according to DSTU B V.2.5-38:2008 " Engineering equipment buildings and structures. Lightning protection device for buildings and structures). For the mesh, as a rule, a wire or cable with a diameter of 6 mm is used. The grid is also installed at a height of 0.5 m above the roof. At the same time, it is connected to several groundings along the perimeter of the building. The distance between grounding points should not exceed 12 m. If there are protruding architectural elements on the roof of the house, for example, towers or pipes, then lightning rods can also be mounted on them. They should protrude 0.5 m above the top edge and be securely grounded.

A down conductor is a thick wire with a cross section of at least 0.5 cm.

Grounding - a metal rod of any profile and section, connected to a down conductor and extending into the ground by at least 50 cm.

In all types of home lightning protection, down conductors and lightning rods with a diameter of at least 6 mm are used. An electrode is used as grounding, which can be either vertical or horizontal. The length of the grounding conductor is 2-3 m, the depth of burial is at least 1 m. To connect the parts of the lightning rod, welded or bolted connections. The quality of the latter must be checked periodically.

Grounding device for lightning rod

It is allowed to ground the lightning rod to the foundation reinforcement if it is not completely covered with a waterproofing layer, and if the soil moisture is more than 3%. The electrodes must be dug deep enough to reach the moist soil layers. And the resistivity of the soil should not be too high, preferably no more than 200 ohms.

Protection of electrodes against corrosion is realized by using galvanized steel or copper. Coating of electrodes with non-conductive enamel or bitumen is not allowed.

One often hears the opinion that metal roofing, for example, sheet copper or metal tiles, sufficiently protects against lightning strikes and does not require additional protection. Unfortunately, this is not entirely true:

1 - any lightning rod must be grounded, and when laying metal tiles, this is usually not done;

2 - the thickness of the metal in this coating is less than a millimeter, and such protection does not save from serious lightning. Lightning of high power simply burns through the metal.

New technologies for lightning protection at home

The listed designs of lightning rods are, figuratively speaking, mechanical, although based on the laws of physics. However, there are more advanced technologies for protecting a home from lightning, the distribution of which is constrained by high cost. We are talking about the so-called ionizers. The essence of the operation of the device is to create an opposing discharge-leader.

The first devices of this type operated on the basis of ionized radiation of a radioactive isotope. Later modifications became purely electronic and isotopes are no longer used.

When voltage is applied to such a device, a column of ionized air arises, on which a lightning discharge closes. Thus, this is no longer a lightning rod, but a kind of trap that attracts lightning from a fairly large area. However, their cost is more than 1000 dollars, which is ten times more expensive than a simple lightning rod, which you can assemble with your own hands, spending only 2-3 hundred hryvnias.

In the world, the entire internal electrical network of a residential facility, including lightning protection and protection against all kinds of external influences, are laid at the stage of the project of the house. That is, the lightning protection system is a part of the integrated network of the facility, and not a separate structure that is not related to power supply.

In modern multi-apartment monolithic buildings, all sections of the circuit from power supply sources are grounded to the internal reinforcement of the load-bearing walls, and through it to the foundation reinforcement.

Prevention and maintenance of lightning protection

In order for the lightning rod to fulfill its function, it must not only be assembled correctly, but also periodically perform preventive maintenance. The properties of a lightning rod depend not only on the design, but also on the operating conditions, for example, on the properties of the soil at the place of the intended grounding. Excessively dry, sandy or rocky soil is poor conductor electricity. In this case, the soil should be moistened, for example, brine, or simply add salt to the composition of the soil. Salt is a good conductor, especially when wet in the rain. Can also be added to soil charcoal which also conducts electricity well. It is important to remember that grounding should not be done anywhere. The electrode must be buried in the ground no closer than 5 meters from the paths, walkways and the building itself.

It is necessary to ensure that rust does not form in the places of assembled contacts. They were not stained with oil, paint or dirt. Places of non-welded joints must be rewound with electrical tape and covered with a layer of waterproofing material.

Preventive inspection of lightning rods is carried out annually in the spring before the beginning of the thunderstorm period. Once every 2-3 years, it is recommended to disassemble the joints, check the contacts, clean them of oxide or rust, and reconnect them. It is advisable to check the condition of the electrode in the ground at least once every three years. If due to corrosion its cross section has noticeably decreased, the earth electrode should be replaced.

current

For buildings and structures, more than 70% of the total area of which are premises not subject to lightning protection according to lightning protection: according to category I - according to , ; for categories II and III - by connecting communications to the grounding device of electrical installations that meets the instructions, or to the reinforcement of the reinforced concrete foundation of the building (taking into account the requirements). The same connection must be provided for internal communications (not introduced from outside).

1.6. In order to protect buildings and structures of any category from direct lightning strikes, existing tall structures (chimneys, water towers, searchlight masts, overhead power lines, etc.), as well as other nearby structures, should be used as natural lightning rods as much as possible.

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Snip installation of lightning protection from a metal strip. What documents regulate the lightning protection device for buildings and structures. General provisions and design principles

What is lightning?

Striking factors of lightning

Protection Options

Type of protection (RD and GOST R IEC 62561.2-2014)

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INSTRUCTIONS FOR LIGHTNING PROTECTION OF BUILDINGS AND STRUCTURES

FOREWORD

1. GENERAL PROVISIONS

2. REQUIREMENTS FOR LIGHTNING PROTECTION OF BUILDINGS AND STRUCTURES

3. LIGHTNING CONSTRUCTIONS

Basic terms

Characteristics of the intensity of thunderstorm activity and lightning resistance of buildings and structures

Protection zones of lightning rods

Manual for the Instructions for the installation of lightning protection of buildings and structures (RD 34.21.122-87)

1. Brief information about lightning discharges and their parameters

2. Characteristics of thunderstorm activity

3. Number of lightning strikes on ground structures

9. Examples of execution of lightning protection of various objects*

INSTRUCTIONS
FOR LIGHTNING PROTECTION OF BUILDINGS AND STRUCTURES

Characteristics of the intensity of thunderstorm activity and
lightning resistance of buildings and structures