Almost any above-ground object is not immune to lightning strikes.
Up to 16 million thunderstorms occur annually on the globe, i.e. about 44 thousand per day.

Thunderstorm activity over different parts of the earth's surface is not the same.

To calculate lightning protection measures, it is necessary to know the specific value characterizing thunderstorm activity in a given area. This value is the intensity of thunderstorm activity, which is usually determined by the number of thunderstorm hours or thunderstorm days per year, calculated as the arithmetic mean over a number of years of observations for a certain location on the earth’s surface.

The intensity of thunderstorm activity in a given area of ​​the earth's surface is also determined by the number of lightning strikes per year per 1 km2 of the earth's surface.

The number of hours of thunderstorm activity per year is taken from official data from weather stations in the area.

The relationship between thunderstorm activity and the average number of lightning strikes per 1 km2 (n) is:

The average duration of thunderstorms per thunderstorm day for the territory of the European part of Russia and Ukraine is 1.5–2 hours.

The average annual duration of thunderstorms for Moscow is 10-20 hours/year, the density of lightning strikes into the ground is 1/km2 per year - 2.0.

Maps of the average annual duration of thunderstorms

(PUE 7. Rules for electrical installations)

In European countries, the designer can easily obtain this statistics using automated system determining the location of a lightning strike. These systems consist of a large number of sensors located throughout Europe and form a single monitoring network.

Information from sensors in real time is sent to monitoring servers and is accessible via the Internet using a special password.

According to available data, in areas with the number of thunderstorm hours per year π = 30 per 1 km2 of the earth's surface, on average, it is affected once every 2 years, i.e. the average number of lightning strikes per 1 km2 of the earth's surface during 1 thunderstorm hour is 0.067. These data allow us to estimate the frequency of lightning strikes of various objects.

The expected number of lightning strikes per year on buildings and structures with a height of no more than 60 m, not equipped with lightning protection, and having a constant height (Fig. 4a), is determined by the formula: Where: S - width of the protected building (structure), m; L - length of the protected building (structure), m; hx is the height of the building along its sides, m; n is the average number of lightning strikes on 1 km2 of the earth’s surface per year in the area where the building is being constructed. Note: for central Russia you can take n = 5 The formula is given taking into account the fact that the number of lightning strikes on a building or structure is proportional to the area occupied not only by the building or structure itself, but also by the sum of the areas of projections of protective zones created by the edges and corners of the roof of the building or structure. If parts of the building are of unequal height (Fig. 4b), then the protection zone created by the high-rise part can cover the entire rest of the building. If the protection zone of the high-rise part does not cover the entire building, it is necessary to take into account the part of the building located outside the protection zone of the high-rise part. The radius of the protective action of a lightning rod is determined by the height of the mast and for a traditional system is approximately calculated by the formula: R=1.732 x h, where h is the height from the highest point of the house to the peak of the lightning rod.

Fig.4. Protection zone created by structures

Rice. 4. Protection zone created by structures: a - buildings with the same height; b - buildings with different heights.
The recommended formula allows for a quantitative assessment of the probability of lightning damage to various structures located in flat areas with fairly uniform ground conditions.

The value of the parameter n included in the calculation formula may differ several times from the values ​​given above.

In mountainous areas, most lightning strikes occur between clouds, so the value of n may be significantly smaller.

Areas where there are layers of soil with high conductivity, as observations show, are selectively affected by lightning discharges, so the value of n in these areas may be significantly higher.

Areas with poorly conductive soils in which extensive metal communications (cable lines, metal pipelines) are laid may be selectively affected.

Metal objects (towers, chimneys) that rise above the ground are also selectively affected.

The density of lightning strikes into the ground, expressed in terms of the number of strikes per 1 km 2 of the earth's surface per year, is determined from meteorological observations at the location of the object or is calculated using a formula.

When calculating the number of strikes by downward lightning, it is assumed that a towering object receives discharges that, in its absence, would strike the surface of the earth of a certain area (the so-called contraction surface). This area has the shape of a circle for a concentrated object (vertical pipe or tower) and the shape of a rectangle for an extended object.
The available statistics of damage to objects of different heights in areas with different durations of thunderstorms made it possible to determine the relationship between the contraction radius (ro) and the height of the object (hx); on average it can be taken ro = 3hх.
The analysis shows that concentrated objects are affected by downward lightning at a height of up to 150 m. Objects above 150 m are 90% affected by upward lightning.

In domestic standards, the height of the lightning rod and the protected object under any circumstances is measured from the ground level, and not from the roof of the structure, which guarantees a certain margin during design, which, unfortunately, is not assessed in quantitative terms.

External lightning protection
External lightning protection of a house is designed to intercept lightning and divert it into the ground. This completely prevents lightning from entering the building and causing it to catch fire.
Internal lightning protection
A building fire is not the only danger during a thunderstorm. There is a danger of exposure of devices to an electromagnetic field, which causes overvoltage in electrical networks. This can lead to the alarm and lights being turned off and equipment being damaged.
Installing special surge voltage protection devices allows you to instantly respond to voltage surges in the network and keep expensive equipment working.

Main types of lightning rod systems:

using 1 pin for the whole house, which, in turn, is divided into traditional (Franklin lightning rod) and with an ionizer;

using a system of pins connected to each other (Faraday cage).

using a cable stretched over the protected structure.

Impact of lightning current

When lightning discharges into an object, the current has thermal, mechanical and electromagnetic effects.
Thermal effects of lightning current. The flow of lightning current through structures is associated with the release of heat. In this case, the lightning current can cause the down conductor to heat up to the melting point or even evaporation.
The cross-section of the conductors must be selected in such a way that the danger of unacceptable overheating is eliminated.

The melting of the metal at the point of contact of the lightning channel can be significant if the lightning strikes a sharp spire. When the lightning channel comes into contact with a metal plane, melting occurs over a sufficiently large area, numerically equal in square millimeters to the value of the current amplitude in kiloamperes.
Mechanical effects of lightning currents. The mechanical forces that arise in various parts of a building and structures when lightning currents pass through them can be very significant.

When exposed to lightning currents, wooden structures can be completely destroyed, and brick pipes and other above-ground structures made of stone and brick can suffer significant damage.
When lightning strikes concrete, a narrow discharge channel is formed. Significant energy released in the discharge channel can cause destruction, which will lead either to a decrease in the mechanical strength of concrete or to deformation of the structure.
When lightning strikes reinforced concrete, the concrete may be destroyed with deformation of the steel reinforcement.

CHECKING LIGHTNING PROTECTION

The lightning protection system of a building requires periodic inspection. The need for such measures is determined, firstly, by the importance of these devices for the safety of both the real estate itself and the people nearby, and secondly, by the fact that lightning rods are constantly exposed to adverse environmental factors.

The first check of the lightning protection system is carried out immediately after installation. In the future, it is carried out at certain intervals established by regulations.

FREQUENCY OF LIGHTNING PROTECTION CHECKS

The frequency of lightning protection inspection is determined in accordance with clause 1.14 RD 34.21.122-87 “Instructions for the installation of lightning protection of buildings and structures.”

According to the document, for all categories of buildings it is carried out at least once a year.

In accordance with the “Rules for the technical operation of consumer electrical installations,” grounding circuits are checked:

Once every six months - visual inspection of visible elements of the grounding device;

Once every 12 years - inspection, accompanied by selective opening of the soil.

Measuring the resistance of ground loops:

Once every 6 years - on power lines with voltages up to 1000 V;

Once every 12 years - on power lines with voltages over 1000 V.

SYSTEM OF LIGHTNING PROTECTION INSPECTION MEASURES

Checking lightning protection includes the following activities:

checking the connection between grounding and lightning rod;

measurement of the transient resistance of bolted connections of the lightning protection system;

grounding check;

insulation check;

visual inspection of the integrity of the system elements (down conductors, lightning rods, points of contact between them), the absence of corrosion on them;

checking the compliance of the actually installed lightning protection system with the design documentation, the validity of installing this type of lightning rod at this facility;

testing the mechanical strength and integrity of welded joints of the lightning protection system (all joints are tapped with a hammer);

determination of the grounding resistance of each individual lightning rod. During subsequent checks, the resistance value should not exceed the level determined during acceptance tests by more than 5 times;

The resistance of the lightning protection system is checked using the MRU-101 device. At the same time, the methodology for checking lightning protection may be different. The most common ones include:
Resistance measurement in a lightning protection system using a three-pole circuit
Resistance measurement in a lightning protection system using a four-pole circuit
The four-pole testing system is more accurate and minimizes the possibility of error.
It is best to check the grounding in conditions of maximum soil resistance - in dry weather or in conditions of greatest freezing. In other cases, correction factors are used to obtain accurate data.

Based on the results of the system inspection, a lightning protection inspection protocol is drawn up, which indicates the serviceability of the equipment.

According to current standards, to determine the lightning protection class, detailed data on the object and, accordingly, risk factors are required. To obtain them, you are asked to fill out several questionnaires. But thanks to this plate, you can pre-select the lightning protection class and risk factors without detailed data.

	Min. amplitude value of lightning current	Max. amplitude value of lightning current	Probability of getting into the lightning protection system
	3 kA	200 kA
	5 kA	150 kA
	10 kA	100 kA
	16 kA	100 kA

Lightning protection of industrial buildings and structures
(Handbook of power supply for industrial enterprises. Industrial electrical networks).

Determining the need for lightning protection of industrial buildings and structures not included in those indicated in the table. , can be carried out for reasons that provide grounds for the use of lightning protection devices.
The reasons for the need for lightning protection devices may be the number of lightning strikes per year of more than 0.05 for buildings and structures of fire resistance degrees I and II; 0.01 - for III, IV and V degrees of fire resistance (regardless of the activity of thunderstorm activity in the area under consideration).
In large buildings (with a width of 100 m or more), it is necessary, in accordance with § 2-15 and 2-27 CH305-69, to provide measures to equalize the potential inside the building in order to avoid damage to electrical installations and injury to people due to direct lightning strikes into the building.

Classification of buildings and structures according to lightning protection and the need for its implementation

Buildings and constructions	The area in which buildings and structures are subject to mandatory lightning protection
Industrial buildings and structures with production facilities classified as classes B-I and B-II PUE	Throughout the USSR
Industrial buildings and structures with premises classified as classes B-Ia, B-Ib and B-IIa according to the Electrical Installation Rules	In areas with average thunderstorm activity of 10 hours or more per year	ІІ
Outdoor technical installations and outdoor warehouses containing explosive gases, vapors, flammable and flammable liquids (for example, gas tanks, containers, loading and unloading racks, etc.), classified as class B-IIa according to the PUE	Throughout the USSR	ІІ
Industrial buildings and structures with production facilities classified as classes P-I, P-II or P-IIa according to the PUE	In areas with average thunderstorm activity of 20 thunderstorm hours or more per year with the expected number of lightning strikes to a building or structure per year of at least 0.05 for buildings or structures of the 1st degree of fire resistance and 0.01 for the III, IV and V degrees of resistance	ІІІ
Industrial buildings and structures of III, IV and V degrees of fire resistance, classified by fire hazard levels into categories G and D according to SNiP II-M, 2-62, as well as open warehouses of solid flammable substances classified into class P-III according to PUE	In areas with average thunderstorm activity of 20 thunderstorm hours or more per year with an expected number of lightning strikes to a building or structure per year of at least 0.05	ІІІ
Outdoor installations in which flammable liquids with a vapor flash point above 45 °C are used or stored, classified as class P-III according to the PUE		ІІІ
Livestock and poultry buildings and structures of agricultural enterprises of III, IV and V degrees of fire resistance for the following purposes: cowsheds and calf barns for 100 heads or more, pigsties for animals of all ages and groups for 100 heads or more; stables for 40 heads or more; poultry houses for all types of poultry ages for 1000 birds or more	In areas with average thunderstorm activity of 40 thunderstorm hours or more per year	ІІІ
Vertical exhaust pipes of industrial enterprises and boiler houses, water and silo towers, fire towers height 15-30 m from the ground surface	In areas with average thunderstorm activity of 20 thunderstorm hours or more per year	ІІІ
Vertical exhaust pipes of industrial enterprises and boiler houses with a height of more than 30 m from the ground surface	Throughout the USSR	ІІІ
Residential and public buildings rising at the level of the general building mass by more than 25 m, as well as separate buildings with a height of more than 30 m, distant from the building mass by at least 100 m	In areas with average thunderstorm activity of 20 thunderstorm hours or more per year	ІІІ
Public buildings of IV and V degree of fire resistance for the following purposes: kindergartens and nurseries; educational and dormitory buildings, canteens of sanatoriums, recreation institutions and pioneer camps, dormitory buildings of hospitals; clubs and cinemas	In areas with average thunderstorm activity of 20 thunderstorm hours or more per year	ІІІ
Buildings and structures of historical and artistic significance, under the jurisdiction of the Department of Fine Arts and Protection of Monuments of the USSR Ministry of Culture	Throughout the USSR	ІІІ

Explanation of the Office for Supervision in the Electric Power Industry of Rostechnadzor 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)

FEDERAL SERVICE			Heads of Federal government agencies departments and energy state inspections energy supervision
IN ECOLOGICAL, TECHNOLOGICAL
AND ATOMIC SUPERVISION
CONTROL
ON SUPERVISION IN THE ELECTRIC POWER INDUSTRY
109074, Moscow, K-74
Kitaigorodsky pr., 7
tel. 710-55-13, fax 710-58-29
01.12.2004	№	10-03-04/182
At no.	from

To the Department for Supervision of the Electric Power Industry Federal service for supervision in the electric power industry (Rostechnadzor) and previously to Gosenergonadzor from numerous organizationsquestions about the procedure for using the "Instructions for lightning protection of buildings, structures and industries"line communications" (SO 153-34.21.122-2003), approved by order of the Ministry of Energy of Russia dated June 30, 2003 No. 280. Attention is drawn to the difficulties of using this Instruction due tolack of reference materials. Questions are also being asked about the legality of the order of RAO UESRussia" dated August 14, 2003 No. 422 "On the revision of normative and technical documents (NTD) and the procedure for their operation in accordance with the Federal Law "On Technical Regulation" and on the timing of preparation of the documentbiy to instructionsSO 153-34.21.122-2003.

The Office for Supervision of the Electric Power Industry of Rostechnadzor clarifies this.

According to the regulations Federal Law dated December 27, 2002 No. 184-FZ "On technicalregulation", Article 4, executive authorities have the right to approve (issue) documents (acts) only of a recommendatory nature. This type of document includes the "InstructionBy lightning protection of buildings, structures and industrial communications."

Order of the Ministry of Energy of Russia dated June 30, 2003 No. 280 does not cancel the previous edition"Instructions for lightning protection of buildings and structures" (RD 34.21.122-87), and the word "instead" in the prefixAccording to individual editions of the instruction SO 153-34.21.122-2003, does not mean that the use of the previous edition is inadmissible. Design organizations have the right to use when determining research on initial data and when developing protective measures, the position of any of the mentionedinstructions or a combination thereof.

Deadline for preparing reference materials for the "Instructions for lightning protection of buildings and structures"tions and industrial communications", SO 153-34.21.122-2003, not currently defineddue to lack of sources of funding for this work.

Order of RAO "UES of Russia" dated August 14, 2003 No. 422 is corporate document and is not valid for organizations that are not part of the structure of RAO UES of Russia.

Head of DepartmentN.P. Dorofeev

GOST standards for lightning protection

GOST R IEC 62561.1-2014 Components of a lightning protection system. Part 1. Requirements for connecting components
GOST R IEC 62561.2-2014 Components of a lightning protection system. Part 2. Requirements for conductors and grounding electrodes
GOST R IEC 62561.3-2014 Components of lightning protection systems. Part 3. Requirements for isolating spark gaps
GOST R IEC 62561.4-2014 Components of lightning protection systems. Part 4. Requirements for conductor fastening devices
GOST R IEC 62561.5-2014 Components of lightning protection systems. Part 5. Requirements for inspection wells and seals of grounding electrodes
GOST R IEC 62561.6-2015 Components of a lightning protection system. Part 6. Requirements for lightning strike meters
GOST R IEC 62561-7-2016 Components of a lightning protection system. Part 7. Requirements for mixtures that normalize grounding

GOST R IEC 62305-1-2010 Risk management. Lightning protection. Part 1. General principles
GOST R IEC 62305-2-2010 Risk management. Lightning protection. Part 2: Risk assessment
GOST R IEC 62305-4-2016 Lightning protection. Part 4. Protection of electrical and electronic systems inside buildings and structures

GOST R54418.24-2013 (IEC 61400-24:2010) Renewable energy. Wind power. Wind power installations. Part 24. Lightning protection

International Electrotechnical Commission(IEC; English International Electrotechnical Commission, IEC; French Commission électrotechnique internationale, CEI) - international non-profit organization on standardization in the field of electrical, electronic and related technologies.
IEC standards are numbered in the range 60000 - 79999, and their names are of the type IEC 60411 Graphic symbols. The numbers of the old IEC standards were converted in 1997 by adding the number 60 000, for example, the IEC 27 standard received the number IEC 60027. The standards developed jointly with the International Organization for Standardization have names of the form ISO/IEC 7498-1:1994 Open Systems Interconnection: Basic Reference Model.

The International Electrotechnical Commission (IEC) has developed standards that set out the principles of protecting buildings and structures of any purpose from overvoltages, allowing for the correct approach to the design of building structures and the lightning protection system of a facility, the rational placement of equipment and the laying of communications.

These primarily include the following standards:

IEC-61024-1 (1990-04): “Lightning protection of building structures. Part 1. Basic principles."

IEC-61024-1-1 (1993-09): “Lightning protection of building structures. Part 1. Basic principles. Guide A: Selecting Protection Levels for Lightning Protection Systems."

IEC-61312-1 (1995-05): “Protection against lightning electromagnetic pulse. Part 1. Basic principles."

The requirements set out in these standards form the “Zone Protection Concept”, the main principles of which are:

use of building structures with metal elements(fittings, frames, load-bearing elements, etc.), electrically connected to each other and the grounding system, and forming a shielding environment to reduce the impact of external electromagnetic influences inside the object (“Faraday cage”);

the presence of a properly implemented grounding and potential equalization system;

dividing the facility into conditional protective zones and using special surge protection devices (SPDs);

compliance with the rules for the placement of protected equipment and conductors connected to it relative to other equipment and conductors that can have a dangerous effect or cause interference.

The expected number N of lightning strikes per year is calculated using the formulas:

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

for rectangular buildings and structures

where h is the greatest height of the building or structure, m; S, L - width and length of the building or structure, respectively, m; n is 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 the building or structure.

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

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

0 " style="margin-left:2.0pt;border-collapse:collapse;border:none">

APPENDIX 3

LIGHTNING DRIVE PROTECTION ZONES

1. Single rod lightning rod.

The protection zone of a single rod lightning rod with height h is a circular cone (Fig. A3.1), the top of which is at height h0

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

Zone A: h0 = 0.85h,

r0 = (1.1 - 0.002h)h,

rx = (1.1 - 0.002h)(h - hx/0.85).

Zone B: h0 = 0.92h;

rx =1.5(h - hx/0.92).

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

h = (rx + 1.63hx)/1.5.

Rice. P3.1. Protection zone of a single rod lightning rod:

I - border of the protection zone at level hx, 2 - the same at ground level

1.2. Protection zones of single rod lightning rods of high-rise buildings 150< h < 600 м имеют следующие габаритные размеры.

2. Double rod lightning rod.

2.1. The protection zone of a double rod lightning rod with a height of h £ 150 m is shown in Fig. P3.2. The end areas of the protection zone are defined as zones of single lightning rods, the overall dimensions of which h0, r0, rx1, rx2 are determined according to the formulas of clause 1.1 of this appendix for both types of protection zones.

Rice. P3.2. Protection zone of double rod lightning rod:

1 - border of the protection zone at level hx1; 2 - the same at level hx2,

3 - same at ground level

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

;

at 2h< L £ 4h

;

;

With a distance between lightning rods L >

at h< L £ 6h

;

;

When the distance between lightning rods is L > 6h, to construct zone B, the lightning rods should be considered as single.

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

h = (hc + 0.14L) / l.06.

2.2. The protection zone of two lightning rods of different heights h1, and h2 £ 150 m is shown in Fig. The dimensions of the end areas of the protection zones h01, h02, r01, r02, rx1, rx2 are determined according to the formulas of clause 1.1, as for the protection zones of both types of a single lightning rod. The overall dimensions of the internal area of ​​the protection zone are determined by the formulas:

;

;

where the values ​​of hc1 and hc2 are calculated using the formulas for hc in clause 2.1 of this appendix.

For two lightning rods of different heights, the construction of zone A of a double rod lightning rod is carried out at L £ 4hmin, and zone B - at L £ 6hmin. With correspondingly large distances between lightning rods, they are considered as single.

Rice. P3.3 Zone protected by two lightning rods of different heights. The designations are the same as in Fig. P3.1

3. Multiple lightning rod.

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

Rice. P3.4. Protection zone (in plan) of a multiple lightning rod. The designations are the same as in Fig. P3.1

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

4. Single cable lightning rod.

The protection zone of a single cable lightning rod with a height of h £ 150 m is shown in Fig. A3.5, where h is the height of the cable in the middle of the span. Taking into account the sag of a cable with a cross section of 35-50 mm2 with a known height of supports hop and span length A The cable height (in meters) is determined by:

h = hop - 2 at a< 120 м;

h = hop - 3 at 120< а < 150м.

Rice. P3.5. Protection zone of a single catenary lightning rod. The designations are the same as in Fig. P3.1

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

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

5. Double cable lightning rod.

5.1. The protection zone of a double cable lightning rod with a height of h £ 150 m is shown in Fig. P3.6. The dimensions r0, h0, rx for protection zones A and B are determined according to the corresponding formulas of clause 4 of this appendix. The remaining zone sizes are determined as follows.

Rice. PZ.6. Protection zone of double cable lightning rod. The designations are the same, 410 and in Fig. P3.2

at h< L £ 2h

;

at 2h< L £ 4h

;

When the distance between cable lightning rods is L > 4h, to construct zone A, the lightning rods should be considered as single.

at h< L £ 6h

;

;

When the distance between cable lightning rods is L > 6h, to construct zone B, the lightning rods should be considered as single. With known values ​​of hc and L (at rcx = 0), the height of the cable lightning rod for zone B is determined by the formula

h = (hc + 0.12L)/1.06.

Rice. P3.7. Protection zone of two cable lightning rods of different heights

5.2. The protection zone of two cables of different heights h1 and h2 is shown in Fig. P3.7. The values ​​of r01, r02, h01, h02, rx1, rx2 are determined according to the formulas of paragraph 4 of this appendix as for a single catenary lightning rod. To determine the sizes rc and hс the following formulas are used:

;

where hc1 and hc2 are calculated using the formulas for hc in Section 5.1 of this appendix.

(RD34.21.122-87)

This manual aims to explain and specify the main provisions of RD 3421.122-87, as well as to familiarize specialists involved in the development and design of lightning protection for various objects with existing ideas about the development of lightning and its parameters that determine the dangerous effects on humans and material values. Examples are given of the implementation of lightning protection of buildings and structures of various categories 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 some ground structure.

A lightning discharge begins with the development of a leader - a weakly glowing channel with a current of several hundred amperes. According to the direction of movement of the leader - from the cloud downwards or from the ground structure upwards - lightning is divided into downward and upward. Data on downward lightning have been accumulated for a long time in several regions of the globe. Information about ascending lightning appeared only in recent decades, when systematic observations of the lightning susceptibility of very tall structures, for example the Ostankino television tower, began.

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

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

Let us first consider the development process and 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's 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, intense heating of the channel occurs (up to tens of thousands of Kelvin) and its shock expansion, which is perceived by ear as a clap of thunder. The main stage current consists of one or more successive pulses superimposed on a continuous component. Most current pulses have negative polarity. The first pulse, with a total duration of several hundred microseconds, has a front length of 3 to 20 μs; the peak current value (amplitude) varies widely: in 50% of cases (average current) exceeds 30, and in 1-2% of cases 100 kA. In approximately 70% of downward negative lightning, the first pulse is followed by subsequent ones with smaller amplitudes and front lengths: the average values ​​are 12 kA and 0.6 μs, respectively. In this case, the slope (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 units to hundreds of amperes and exists throughout the entire flash, lasting on average 0.2 s, and in rare cases 1-1.5 s.

The charge transferred during the entire lightning flash ranges from units to hundreds of coulombs, of which the individual pulses account for 5-15 coulombs, and the continuous component accounts for 10-20 coulombs.

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

The accumulated actual data on the parameters of downward lightning do not allow us to judge their differences in different geographical regions. Therefore, for the entire territory of the USSR, their probabilistic characteristics are assumed to be the same.

Rising 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 lasting tenths of a second, carrying a charge of 2-20 C; the second is characterized by the superposition of short pulses on the long-term pulseless component, the amplitude of which is on average 10-12 kA and only in 5% of cases exceeds 30 kA, and the transferred charge reaches 40 C. These impulses are similar to the subsequent impulses of the main stage of downward negative lightning.

In mountainous areas, upward lightning is characterized by longer continuous currents and larger transferred charges than on the plain. At the same time, variations in the pulse components of the current in the mountains and on the plain differ little. To date, no connection has been identified 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 assessed as the same for any geographical regions and heights of objects.

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 means. For example, the minimum permissible distances from lightning rods and their grounding conductors to objects of category I (clauses 2.3-2.5 *) are determined from the condition that lightning rods are damaged by downward lightning with the amplitude and slope of the current front within the limits of 100 kA and 50 kA/µs, respectively. This condition is met in at least 99% of cases of damage by downward lightning.

2. CHARACTERISTICS OF LIGHTNING ACTIVITY

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

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

In general, across the globe, the density of lightning strikes varies from almost zero in the polar regions to 20-30 strikes per 1 km of land per year in humid tropical zones. For the same region, variations are possible from year to year, 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 into the ground are possible. On a mass scale (for example, for the entire territory of the USSR), recording the number of lightning strikes into the ground is not yet feasible due to labor intensity and lack of reliable equipment.

However, for geographic locations where lightning counters are installed and meteorological observations of thunderstorms are carried out, a correlation has been found between the density of discharges into the ground and the frequency or duration of thunderstorms, although each of these parameters is subject to variation from year to year or from thunderstorm to thunderstorm. In RD 34.21.122-87 this correlation dependence, presented in Appendix 2, is extended to the entire territory of the USSR and connects purely downward lightning strikes in 1 km2 of the earth's surface with a specific duration of thunderstorms in hours. Data from meteorological stations on the duration of thunderstorms are averaged over the period from 1936 to 1978 and are plotted on the geographical map of the USSR in the form of lines characterized by a constant number of hours with thunderstorms per year (Fig. 3 RD 34.21.122-87); in this case, the duration of a thunderstorm for any point is set in the interval between the two lines closest to it. For some regions of the USSR, on the basis of instrumental research, regional maps of the duration of thunderstorms have been compiled, these maps are also recommended for use (see Appendix 2 RD34.21.122-87)

In this indirect way (through data on the duration of thunderstorms) it is possible to introduce zoning of the territory of the USSR according to the density of lightning strikes into the ground.

3. NUMBER OF LIGHTNING DAMAGES ON GROUND STRUCTURES

According to the requirements of table. 1 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 facility. It is desirable that this method take into account known characteristics of thunderstorm activity and other information about lightning.

When calculating the number of strikes by downward lightning, the following concept is used: a towering object receives discharges that, in its absence, would strike the surface of the earth of a certain area (the so-called contraction surface). This area has the shape of a circle for a concentrated object (a vertical pipe or tower) and the shape of a rectangle for an extended object, such as an overhead power line. The number of hits to 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 R0 is the contraction radius; n is the average annual number of lightning strikes per 1 km2 of the earth's surface. For an extended object with length l

The available statistics of damage to objects of different heights in areas with different durations of thunderstorms made it possible to roughly determine the relationship between the contraction radius R0 and the height of the object h. Despite the significant scatter, on average we can take R0 = 3h.

The given ratios are the basis for the formulas for calculating the expected number of lightning strikes on concentrated objects and objects with given dimensions in Appendix 2 of RD 34.21.122-87. The lightning damage 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 the data in Appendix 2. It can be assumed that the probability of damage to an object increases, for example, with increasing amplitude of the lightning current, and depends on other parameters of the discharge. However, the available statistics of damage were obtained in ways (by photographing lightning strikes, recording with special meters) that do not allow us to isolate the influence of factors other than the intensity of thunderstorm activity.

Let us now estimate, using the formulas in Appendix 2, how often objects of different sizes and shapes can be struck by lightning. For example, with an average duration of thunderstorms of 40-60 hours per year, no more than one damage can be expected in a concentrated object 50 m high (for example, a chimney) in 3-4 years, and in a building 20 m high and with plan dimensions of 100x100 m (typical by size for many types of production) - no more than one lesion in 5 years. Thus, with moderate sizes of buildings and structures (height within 20-50 m, length and width approximately 100 m), lightning damage is a rare event. For small buildings (with dimensions of approximately 10 m), the expected number of lightning strikes rarely exceeds 0.02 per year, which means that no more than one lightning strike can occur during their entire service life. For this reason, according to RD 34.21.122-87, for some small buildings (even with low fire resistance), lightning protection is not provided at all or is significantly simplified.

For concentrated objects, the number of strikes by downward lightning increases quadratically with height and in areas with moderate duration of thunderstorms at an object height of about 150 m it is one to two strikes per year. From concentrated objects of greater height, ascending lightning is excited, the number of which is also proportional to the square of the height. This idea of ​​the susceptibility of high objects is confirmed by observations carried out at the Ostankino television tower, 540 m high: about 30 lightning strikes occur annually and more than 90% of them are from upward discharges; the number of strikes from downward lightning remains at the level of one or two per year. Thus, for concentrated objects with a height of more than 150 m, the number of strikes by downward lightning depends little on the height.

4. HAZARDOUS EFFECTS OF LIGHTNING

The list of basic terms (Appendix 1 RD 34.21.122-87) lists possible types of lightning impacts on various ground objects. In this paragraph, information about the dangerous effects of lightning is presented in more detail.

The effects of lightning are usually divided into two main groups:

primary, caused by a direct lightning strike, and secondary, induced by nearby lightning discharges or carried into the object by extended metal communications. The danger of a direct strike and secondary effects of lightning for buildings and structures and the people or animals in them is determined, on the one hand, by the parameters of the lightning discharge, and on the other - by the technological and design characteristics of the object (presence of explosion or fire hazardous zones, fire resistance of building structures, type input communications, their location inside the object, etc.). A direct lightning strike causes the following effects on an object: electrical, associated with electric shock to people or animals and the appearance of overvoltage on the affected elements. The overvoltage is proportional to the amplitude and slope of the lightning current, the inductance of structures and the resistance of the grounding conductors through which the lightning current is discharged into the ground. Even with lightning protection, direct lightning strikes with high currents and steepness can lead to overvoltages of several megavolts. In the absence of lightning protection, the paths of lightning current spreading are uncontrollable and its strike can create a danger of electric shock, dangerous step and touch voltages, and overlap to other objects;

thermal, associated with a sharp release of heat during direct contact of the lightning channel with the contents of the object and when lightning current flows through the object. The energy released in the lightning channel is determined by the transferred charge, the duration of the flash and the amplitude of the lightning current; and in 95% of cases of lightning discharges, this energy (calculated for a resistance of 1 Ohm) exceeds 5.5 J, it is two to three orders of magnitude higher than the minimum ignition energy of most gas, steam and dust-air mixtures used in industry. Consequently, in such environments, contact with the lightning channel always creates a danger of ignition (and in some cases, explosion), the same applies to cases of lightning channel penetration of the housings of explosive outdoor installations. When lightning current flows through thin conductors, there is a danger of them melting and breaking;

mechanical, caused by a shock wave propagating from the lightning channel, and electrodynamic forces acting on conductors with lightning currents. This impact can cause, for example, thin metal tubes to flatten. Contact with a lightning channel can cause sudden vapor or gas formation in some materials, followed by mechanical destruction, such as splitting wood or cracking concrete.

Secondary manifestations of lightning are associated with the effect of close discharges on the object of the electromagnetic field. Usually this field is considered in the form of two components: the first is caused by the movement of charges in the lightning leader and channel, the second is due to the change in lightning current over time. These components are sometimes called electrostatic and electromagnetic induction.

Electrostatic induction manifests itself in the form of overvoltage that occurs on the metal structures of an object and depends on the lightning current, the distance to the strike site and the resistance of the ground electrode. In the absence of a proper grounding system, overvoltage can reach hundreds of kilovolts and create a danger of injury to people and overlaps between different parts of the facility.

Electromagnetic induction is associated with the formation of an EMF in metal circuits, proportional to the steepness of the lightning current and the area covered by the circuit. Extended communications in modern industrial buildings can form circuits covering a large area, in which it is possible to induce an EMF of several tens of kilovolts. In places where extended metal structures come together, in gaps in open circuits, there is a danger of overlaps and sparks with possible energy dissipation of about tenths of a joule.

Another type of dangerous impact of lightning is the introduction of high potential through communications introduced into the facility (overhead power lines, cables, pipelines). It is an overvoltage that occurs on communications during direct and close lightning strikes and spreads in the form of a wave impinging on the object. The danger is created due to possible overlaps from communications to grounded parts of the facility. Underground communications also pose a danger, since they can absorb part of the lightning currents spreading in the ground and carry them into the facility.

5. CLASSIFICATION OF PROTECTED OBJECTS

The severity of the consequences of a lightning strike depends primarily on the explosion or fire hazard of a building or structure due to the thermal effects of lightning, as well as sparks and overlaps caused by other types of impacts. For example, in industries that are constantly associated with open fire, combustion processes, and the use of fireproof materials and structures, the flow of lightning current does not pose a great danger. On the contrary, the presence of an explosive atmosphere inside the object will create the threat of destruction, human casualties, and large material damage.

With such a variety of technological conditions, presenting the same requirements for lightning protection of all objects would mean either investing excessive reserves in it, or putting up with the inevitability of significant damage caused by lightning. Therefore, RD 34.21.122-87 adopted a differentiated approach to lightning protection of various objects, and therefore in Table. 1 of this Instruction, buildings and structures are divided into three categories, differing in severity possible consequences lightning damage.

Category I includes industrial premises in which, under normal technological conditions, explosive concentrations of gases, vapors, dusts, and fibers can be present and formed. Any lightning strike, causing an explosion, creates an increased danger of destruction and casualties not only for the given object, but also for those nearby.

Category II includes industrial buildings and structures in which the appearance of an explosive concentration occurs as a result of a violation of the normal technological regime, as well as external installations containing explosive liquids and gases. For these objects, a lightning strike creates a danger of explosion only when it coincides with a technological accident or the activation of breathing or emergency valves in outdoor installations. Due to the moderate duration of thunderstorms on the territory of the USSR, the likelihood of these events coinciding is quite low.

Category III includes objects whose consequences are associated with less material damage than in an explosive environment. This includes buildings and structures with fire-hazardous premises or building structures of low fire resistance, and for them the requirements for lightning protection are tightened with an increase in the probability of damage to the object (the expected number of lightning strikes). In addition, category III includes objects whose damage poses a danger of electrical exposure to people and animals: large public buildings, livestock buildings, tall structures such as pipes, towers, monuments. Finally, category III includes small buildings in rural areas, where combustible structures are most often used. According to statistics, these objects account for a significant proportion of fires caused by thunderstorms. Due to the low cost of these buildings, their lightning protection is carried out using simplified methods that do not require significant material costs (clause 2.30).

Rules for the construction of electrical installations (PUE). Chapter 2.5. Overhead power lines with voltage above 1 kV (Start)
Rules for the construction of electrical installations (PUE). Chapter 2.5. Overhead power lines with voltage above 1 kV (End)

INSULATION

INSULATION

2.5.57. On overhead lines 110 kV and above, only suspended insulators should be used; on overhead lines 35 kV and below, suspension and pin (including support-rod) insulators can be used.

2.5.58. The number of pendant insulators and the type of pin insulators for overhead lines with a voltage of 6 kV and higher are selected to ensure their reliable operation in accordance with the “Instructions for designing insulation in areas with a clean and polluted atmosphere.”

Table 2.5.15. Minimum wet-discharge voltage of pin insulators

Rated voltage of overhead lines, kV
Effective wet-discharge voltage, kV

Table 2.5.16. Estimated switching overvoltage accepted when choosing overhead line insulation

Rated voltage of overhead lines, kV	Estimated frequency of switching overvoltages Naib. slave	Switching overvoltages, kV

2.5.59. When using suspended insulators with a ratio of the creepage distance to the building height of more than 2.3, the garland selected according to the operating voltage is checked according to the conditions of exposure to switching overvoltages, the calculated values ​​of which are given in table. 2.5.17.

2.5.60. On transition supports with a height of more than 40 m, the number of suspended insulators in the garland should be increased in comparison with those accepted on the remaining supports of this overhead line by one insulator for every 10 m of support height above 40 m.

2.5.61. The safety factors of insulators, i.e. the ratio of the mechanical load that destroys pin and support-rod insulators, or the electromechanical destructive load of suspended insulators to the highest standard load acting on the insulators, should be: when operating overhead lines in normal mode - at least 2, 7; at average annual temperature, absence of ice and wind - not less than 5.0; in emergency mode, for overhead insulators of 500 kV overhead lines - no less than 2.0, and for voltages of 330 kV and below - no less than 1.8.

Loads acting on insulators in emergency mode are determined in accordance with 2.5.89-2.5.91 and 2.5.93.

Table 2.5.17. Number of insulators in supporting garlands of 110-500 kV overhead lines with metal and reinforced concrete supports

Insulator type	Number of insulators, pcs., at rated voltage of overhead lines, kV
PF6-A (P-4.5)
PF6-B (PM-4.5)
PF6-V (PFE-4.5)
PF6-V (with Quality Mark)
PF20-A(PFE-16)
PS6-A (PS-4.5)
PS-11 (PS-8.5)
PS16-A(LS-16)
PS16-B (with Quality Mark)
PS30-A (LS-30)

SURGE VOLTAGE PROTECTION, GROUNDING

2.5.62. 110-500 kV overhead lines with metal and reinforced concrete supports must be protected from direct lightning strikes by cables along the entire length of the line.

The construction of 110-500 kV overhead lines without cables is allowed:

1) in areas with less than 20 thunderstorm hours per year;

2) in certain sections of overhead lines in areas with poorly conductive soils (Ohm m);

3) on sections of the route with an estimated ice wall thickness of more than 20 mm.

Reinforcement of insulation for the cases given in paragraphs 1-3 is not required.

In the absence of data on the average annual duration of thunderstorms, you can use a map of the zoning of the territory of the USSR according to the number of thunderstorm hours per year (Fig. 2.5.13-2.5.15).

Rice. 2.5.13. Map of the average annual duration of thunderstorms. Sheet 1

Rice. 2.5.13. Map of the average annual duration of thunderstorms. Sheet 1

Rice. 2.5.14. Map of the average annual duration of thunderstorms. Sheet 2

Rice. 2.5.14. Map of the average annual duration of thunderstorms. Sheet 2

Rice. 2.5.15. Map of the average annual duration of thunderstorms. Sheet 3

Rice. 2.5.15. Map of the average annual duration of thunderstorms. Sheet 3

Rice. 2.5.16. Map of the average annual duration of thunderstorms. Sheet 4

Rice. 2.5.16. Map of the average annual duration of thunderstorms. Sheet 4

Protection of overhead line approaches to substations must be carried out in accordance with the requirements of Chapter. 4.2.

2.5.63. For overhead lines up to 35 kV, the use of lightning protection cables is not required. 110 kV overhead lines on wooden supports, as a rule, should not be protected with cables.

2.5.64. Single metal and reinforced concrete supports and other places with weakened insulation on 35 kV overhead lines with wooden supports must be protected by tubular arresters or, in the presence of automatic reclosure, protective gaps, and on 110-220 kV overhead lines by tubular arresters. If there are no 110-220 kV tubular arresters with the required parameters, it is allowed to install protective gaps instead.

2.5.65. When protecting overhead lines from lightning overvoltages with cables, you must be guided by the following:

1. Single-post metal and reinforced concrete supports with one cable must have a protection angle of no more than 30°, and with two cables for lightning protection purposes - no more than 20°.

2. On metal supports with horizontal wires and two cables, the angle of protection with respect to external wires should be no more than 20°; in III, IV and special areas for ice, as well as in areas with frequent dancing of wires, a protection angle of up to 30° is allowed.

3. On portal-type reinforced concrete and wooden supports, the protection angle with respect to the outermost wires is allowed no more than 30°.

4. When protecting an overhead line with two cables, the distance between them should be no more than five times the vertical distance from the cables to the wires.

2.5.66. The vertical distances between the cable and the overhead line wire in the middle of the span, without taking into account their deflection by the wind, according to the conditions of protection against lightning overvoltages, must be no less than those given in table. 2.5.18 and not less than the vertical distance between the cable and the wire on the support.

For intermediate values ​​of span lengths, the distances are determined by interpolation.

2.5.67. Fastening of cables on all supports of 220-500 kV overhead lines must be done using an insulator, bridged with a spark gap measuring 40 mm.

On each anchor section up to 10 km long, the cables must be grounded at one point by installing special jumpers on the anchor support. With a large length of anchor spans, the number of grounding points in the span is selected so that at the highest value of the longitudinal electromotive force induced in the cable during a short circuit on the overhead line, breakdown of the spark gaps on the overhead line does not occur.

In the case of suspending cables on several insulators, for example for melting ice on cables or for communication, the size of the spark gap must be coordinated with the electrical strength of the garland on which the cable is suspended.

On the approaches of 220-330 kV overhead lines to substations over a length of 2-3 km and on the approaches of 500 kV overhead lines over a length of at least 5 km, if the cables are not used for capacitive selection, ice melting or communication, they should be grounded at each support.

On overhead lines of 150 kV and below, if melting of ice on the cable is not provided, insulated fastening of the cable should be performed only on metal and reinforced concrete anchor supports. If such melting is provided, then insulated cable fastening must be made along the entire length of the overhead line.

Table 2.5.18. The smallest distance between the cable and the wire in the middle of the span

Span length, m	Minimum distance between cable and wire vertically, m

2.5.68. On overhead lines with portal-type wooden supports, the distance between phases in wood must be at least 5 m for a 220 kV overhead line, 4.5 m for a 150 kV overhead line, 4 m for a 110 kV overhead line, 3 m for a 35 kV overhead line.

In some cases, for 110-220 kV overhead lines, if there are justifications (small short-circuit currents, areas with weak thunderstorm activity, reconstruction, etc.), it is possible to reduce the specified distances to the value recommended for overhead lines with a voltage one step lower.

On single-column wooden supports, the following distances between phases in wood are allowed: 2.5 m for 35 kV overhead lines, 0.75 m for 3-20 kV overhead lines, provided that the span distances are observed in accordance with 2.5.53.
The use of metal crossbars on wooden supports is not recommended.

Table 2.5.19. Minimum permissible insulation distance
by air from live to grounded parts of overhead lines

Design condition	Minimum insulation distance, cm, at overhead line voltage, kV
Lightning overvoltages for insulators:
pin
hanging
Internal overvoltages
Operating voltage
Ensuring safe ascent to the support

2.5.69. Cable inserts in overhead lines with a length of less than 1.5 km must be protected at both ends of the cable from lightning overvoltages by tubular or valve arresters. The grounding clamp of the arrester, the metal sheaths of the cable, as well as the body of the cable coupling must be connected to each other along the shortest path. The grounding clamp of the arrester must be connected to the ground electrode via a separate outlet.

2.5.70. At overhead line crossings through rivers, gorges, etc., when the height of the supports is more than 40 m and there are no cables on the supports, tubular arresters must be installed.

2.5.71. For overhead lines running at an altitude of up to 1000 m above sea level, the insulation distances in the air from live wires and fittings to the grounded parts of the supports must be no less than those given in table. 2.5.19.

Insulating distances in the air between live parts and a wooden support that does not have grounding slopes may be reduced by 10%, with the exception of distances selected based on the condition of safe ascent to the support.

When passing overhead lines in mountainous areas, the smallest insulation distances for operating voltage and internal overvoltages should be increased compared to those given in Table. 2.5.19 by 1% for every 100 m and above 1000 m above sea level.

2.5.72. The shortest distances on the support between the wires of the overhead line at the places where they intersect each other during transposition, branches, transition from one arrangement of wires to another must be no less than those given in table. 2.5.20.

2.5.73. Additional requirements for protection against lightning overvoltages of overhead lines when they cross each other and when they cross various structures are given in 2.5.122, 2.5.129, 2.5.140 and 2.5.152.

Table 2.5.20. Smallest distance between
phases of overhead lines on a support

Design condition	Minimum distance between phases, cm, at overhead line voltage, kV
Lightning surges
Internal overvoltages
Operating voltage

2.5.74. The following must be grounded on the overhead line:

1) supports with lightning protection cable or other lightning protection devices;

2) reinforced concrete and metal supports of 3-35 kV overhead lines;

3) supports on which power or instrument transformers, disconnectors, fuses or other devices are installed;

4) metal and reinforced concrete supports of 110-500 kV overhead lines without cables and other lightning protection devices, if this is necessary to ensure reliable operation of relay protection and automation.

2.5.75. The resistances of the grounding devices of the supports specified in 2.5.74, clause 1 must be no more than those given in the table. 2.5.21.

The resistances of the grounding devices of the supports specified in 2.5.74, clause 2 must be: for 3-20 kV overhead lines in populated areas, as well as for all 35 kV overhead lines - no more than those given in table. 2.5.21, for 3-20 kV overhead lines in an uninhabited area in soils with a resistivity of up to 100 Ohm m - no more than 30 Ohm, and in soils with a resistivity above 100 Ohm m - no more than 0.3 Ohm.

The resistance of the grounding devices of the supports specified in 2.5.74, clause 3, for overhead lines 110 kV and above should be no more than those given in the table. 2.5.22, and for 3-35 kV overhead lines must be selected in accordance with the requirements of 1.7.57 and 1.7.58.

The resistances of the grounding devices of the supports specified in 2.5.74, clause 4 are determined when designing the overhead line.

For overhead lines protected by cables, the resistance of grounding devices carried out according to lightning protection conditions must be ensured when the cable is disconnected, and under other conditions - when the cable is not disconnected.

For supports with a height of more than 40 m in areas of overhead lines protected by cables, the resistance of grounding devices should be 2 times less than those given in table. 2.5.21.

The resistance of grounding devices of overhead line supports must be provided and measured at industrial frequency currents during the period of their highest values ​​in the summer. It is allowed to take measurements in other periods with the results adjusted by introducing a seasonal coefficient, however, measurements should not be made during a period when the value of the resistance of grounding devices is significantly affected by soil freezing.

Table 2.5.21. The highest resistance of grounding devices
overhead line supports

Specific equivalent resistance of earth, Ohm m	Maximum resistance of the grounding device, Ohm
More than 100 to 500
More than 500 to 1000
More than 1000 to 5000
More than 5000

2.5.76. When passing overhead lines of 110 kV and higher in areas with clayey, loamy, sandy loam and similar soils with a resistivity of 500 Ohm m, reinforcement of reinforced concrete foundations, supports and stepsons should be used as natural grounding conductors without additional installation or in combination with laying artificial grounding conductors. In soils with higher resistivity, the natural conductivity of reinforced concrete foundations should not be taken into account, and the required resistance value of the grounding device should be ensured only by the use of artificial ground electrodes.

The resistance values ​​of grounding devices for 3-35 kV overhead line supports should be ensured by the use of artificial grounding conductors, and the natural conductivity of foundations, underground parts of supports and stepsons (attachments) should not be taken into account in calculations.

2.5.77. Reinforced concrete foundations of overhead line supports can be used as natural grounding conductors (for an exception, see 2.5.76 and 2.5.142) when making a metal connection between anchor bolts and foundation reinforcement.

The presence of bitumen coating on reinforced concrete supports and foundations used as natural grounding systems should not be taken into account.

Measurement of the conductivity of reinforced concrete foundations, underground parts of supports and stepsons should be carried out no earlier than 2 months after their installation.

2.5.78. To ground reinforced concrete supports, all those elements of stressed and unstressed longitudinal reinforcement of the racks that are metallic connected to each other and can be connected to the grounding conductor should be used as grounding conductors.

Reinforcement rods used for grounding must be tested for thermal resistance when passing short-circuit currents. During the short circuit, the rods should heat up by no more than 60°C.

Guys of reinforced concrete supports should be used as grounding conductors in addition to the reinforcement. In this case, the free end of the guy ropes must be connected to the working part of the guy wires using a special clamp.

Cables and parts for fastening insulators to the traverse of reinforced concrete supports must be metal connected to a grounding descent or grounded reinforcement.

2.5.79. The cross-section of each of the grounding descents on the overhead line support must be at least 35 mm, and for single-wire descents the diameter must be at least 10 mm. It is allowed to use galvanized steel single-wire descents with a diameter of at least 6 mm.

2.5.80. Overhead line grounding conductors, as a rule, must be located at a depth of at least 0.5 m, and in arable land - 1 m. In the case of installing supports in rocky soils, it is permissible to lay radial grounding conductors directly under the collapsible layer above the rocks with a layer thickness of at least 0. 1 m. If the thickness of this layer is smaller or absent, it is recommended to lay grounding conductors along the surface of the rock and fill them with cement mortar.

FITTINGS

2.5.81. Attaching wires to suspension insulators and fastening cables should be done using support or tension clamps. Among tension clamps, preference should be given to clamps that do not require cutting the wire. Fastening of wires to pin insulators should be done using wire ties or special clamps.

2.5.82. Supporting clamps for hanging wires may be blind or have limited strength seals. For reliability reasons, the use of blind clamps is recommended. Lightning protection cables should be suspended from supports only in blind clamps.

For large transitions, multi-roller hangers and special clamps can be used.

2.5.83. Connections of wires and cables should be made using connecting clamps, welding, as well as using clamps and welding in combination. In one span of overhead lines, no more than one connection is allowed for each wire or cable.

In spans crossing engineering structures listed in 2.5.118-2.5.160 and 2.6.163-2.5.167, one connection per wire (cable) is allowed: for steel-aluminum wires with a ratio A: C4.29 - with a cross-section of 240 mm or more , with a ratio A: C1.46 - of any cross-section, with steel cables - with a cross-section of 120 mm or more, as well as when the phase is split into three steel-aluminum wires with a ratio of A: C4.29 - with a cross-section of 150 mm or more.

The minimum distance from the connecting clamp to the clamp with limited sealing strength must be at least 25 m.

2.5.84. The strength of the sealing of wires and cables in connecting and tension clamps must be at least 90% of the tensile strength of the wire or cable.

2.5.85. The safety factors of linear reinforcement, i.e. the ratio of the minimum destructive load to the standard load perceived by the reinforcement, must be at least 2.5 when operating overhead lines in normal mode and at least 1.7 in emergency mode.

On lines with mechanical stress in wires exceeding 42% of the tensile strength at the highest load, before the development of new types of fittings, it is allowed to reduce the safety factors of linear fittings in normal mode to 2.3.

The safety factors of hooks and pins must be no less than 2.0 in normal mode and no less than 1.3 in emergency mode.

Loads acting on reinforcement, hooks and pins in emergency mode are determined in accordance with 2.5.89-2.5.91 and 2.5.93.

SUPPORTS

2.5.86. Overhead line supports above 1 kV are divided into two main types: anchor supports, which fully accept the tension of wires and cables in the spans adjacent to the support, and intermediate supports, which do not perceive the tension of the wires or perceive it partially. End and transposition supports can be made on the basis of anchor supports. Intermediate and anchor supports can be straight or angular.

Depending on the number of chains suspended on them, supports are divided into single-chain, double-chain, etc.

Intermediate supports can be of flexible or rigid design; anchor-type supports must be rigid. Anchor-type supports can be of normal or lightweight design.

The supports can be free-standing or with guy wires.

The design of supports, foundations and foundations must be carried out taking into account the instructions given in the appendix to this chapter.

2.5.87. Supports must be designed for the loads of normal and emergency modes of overhead lines.

Anchor supports must be designed for the difference in tension of wires and cables resulting from the inequality of the values ​​of the given spans on both sides of the support. In this case, the conditions for calculating the tension difference are established when developing support structures.

Double-chain supports in all modes must be designed for conditions when only one chain is mounted.

The supports must be checked for the conditions of their assembly and installation, as well as for the conditions of installation of wires and cables.

2.5.88. Supports on overhead lines must be designed for the following normal operating conditions:

1. Wires and cables are not torn and free from ice, high-speed wind pressure, temperature minus 5°C.

2. Wires and cables are not broken and covered with ice, wind speed is 0.25, temperature is minus 5°C (see also 2.5.34).

Anchor supports and intermediate corner supports should also be designed for low temperature conditions without wind, if the tension of wires or cables in this mode is greater than in the heaviest load mode.

End supports must also be designed for one-way tension of all wires and cables (wires and cables from the side of the substation or span adjacent to the large crossing are not mounted).

2.5.89. Intermediate supports of overhead lines with supporting garlands and blind clamps must be designed for conditional horizontal static loads in emergency modes.

The calculation is made under the following conditions:

1. The wire or wires of one phase are broken (for any number of wires on the support); the cables are not broken.

2. One cable is broken; the wires are not broken.

Conditional loads are applied at the attachment points of the wire or cable, in the event of a break in which the forces in the calculated support elements are greatest.

Loads from wires and cables should be taken under average operating conditions (in conditions without ice and without wind).

In the calculations of overhead line supports with unsplit phases, the conditional loads from the wire are taken:

A. For free-standing metal supports and supports made of any material on guy wires with wires with a cross-section of up to 185 mm 0.5; with a cross section of 205 mm and more than 0.4;

B. For reinforced concrete free-standing supports with wires with a cross-section of up to 185 mm 0.3; with a cross section of 205 mm and more than 0.25.

B. For wooden free-standing supports with wires with a cross-section of up to 185 mm 0.25; with a cross section of 205 mm and more than 0.2, where is the highest standard tension of the wire or wires of one phase.

D. For other supports (supports made of new materials, flexible metal supports, etc.) - depending on the flexibility of the calculated supports within the limits specified in paragraphs A - B.

In the calculations of overhead line supports up to 330 kV with split phases, the standard load is determined by multiplying the values ​​​​specified in paragraphs A - B for unsplit phases by additional coefficients: 0.8 when split into two wires, 0.7 - into three wires and 0 ,6 - on four wires.

In the calculations of 500 kV overhead line supports with split phases, the standard conditional load applied at the point of attachment of one phase is taken equal to 0.15, but not less than 18 kN.

When using means that limit the transfer of longitudinal load to the intermediate support (clamps with limited embedding strength, suspension on blocks, as well as other means), the calculation should be made for the standard loads arising when using these means, but not more than the nominal loads taken during suspension wires in blind clamps.

The conditional horizontal load from the cable is assumed to be 0.5.

For flexible supports (reinforced concrete and wooden supports without guy wires), it is allowed to determine the standard load from a cable break taking into account the flexibility of the supports.

In calculations, it is possible to take into account the supporting effect of unbroken wires and cables at average annual temperatures without ice and wind. In this case, the standard conditional loads should be taken as for metal free-standing supports and supports made of any material on guys, and the mechanical stresses arising in the supporting wires and cables should not exceed 70% of the tensile strength.

2.5.90. Intermediate supports of overhead lines with fastening of wires on pin insulators using wire knitting must be designed in emergency mode, taking into account the flexibility of the supports for the break of one wire, which produces the greatest forces in the support elements. The conditional standard horizontal load along the line from the pull of a broken wire when calculating the rack should be taken equal to 0.5

When calculating overhead lines and their elements, climatic conditions must be taken into account - wind pressure, ice wall thickness, air temperature, degree of aggressive environmental influences, intensity of thunderstorm activity, dancing of wires and cables, vibration.

The determination of design conditions for wind and ice should be made on the basis of the corresponding maps of climatic zoning of the territory of the Russian Federation (Fig. 2.5.1, 2.5.2 - see color insert), with clarification, if necessary, of their parameters in the direction of increasing or decreasing according to regional maps and long-term materials observations of hydrometeorological stations and weather posts on wind speed, mass, size and type of ice-frost deposits. In poorly studied areas* special surveys and observations can be organized for this purpose.

* Poorly studied areas include mountainous areas and areas where there is only one representative meteorological station per 100 km of overhead line route to characterize climatic conditions.

Fig.2.5.1. Map of zoning of the territory of the Russian Federation by wind pressure

Fig.2.5.2. Map of zoning the territory of the Russian Federation according to the thickness of the ice wall

In the absence of regional maps, the values ​​of climatic parameters are clarified by processing the corresponding long-term observation data according to methodological instructions(MU) for calculating climatic loads on overhead lines and constructing regional maps with a repeatability of 1 time in 25 years.

The basis for zoning by wind pressure are the values ​​of maximum wind speeds with a 10-minute interval of averaging speeds at a height of 10 m with a repeatability of 1 time in 25 years. Ice zoning is carried out according to the maximum wall thickness of cylindrical ice deposits at a density of 0.9 g/cm on a wire with a diameter of 10 mm, located at a height of 10 m above the ground, repeating once every 25 years.

The air temperature is determined on the basis of data from meteorological stations, taking into account the provisions of building codes and regulations and the instructions of these Rules.

The intensity of thunderstorm activity should be determined from zoning maps of the territory of the Russian Federation according to the number of thunderstorm hours per year (Fig. 2.5.3 - see color insert), regional maps with clarification, if necessary, based on weather station data on the average annual duration of thunderstorms.

Fig.2.5.3. Map of the zoning of the territory of the Russian Federation by the average annual duration of thunderstorms in hours

The degree of aggressive environmental impact is determined taking into account the provisions of SNiPs and state standards, containing requirements for the use of overhead line elements, Chapter 1.9 and the instructions of this chapter.

The determination of regions based on the frequency of repetition and intensity of the dancing of wires and cables should be made according to the zoning map of the territory of the Russian Federation (Fig. 2.5.4 - see color insert) with clarification based on operational data.

Fig.2.5.4. Map of the zoning of the territory of the Russian Federation according to the dance of wires

Based on the frequency and intensity of the dancing of wires and cables, the territory of the Russian Federation is divided into areas with moderate dancing of wires (frequency of dancing once every 5 years or less) and with frequent and intense dancing of wires (frequency of repetition more than once every 5 years).

2.5.39

When determining climatic conditions, the influence on the intensity of ice formation and on wind speed must be taken into account by the features of the micro-relief of the area (small hills and basins, high embankments, ravines, gullies, etc.), and in mountainous areas - the features of the micro- and mesorelief of the area (ridges) , slopes, plateau-like areas, valley bottoms, intermountain valleys, etc.).

2.5.40

The values ​​of maximum wind pressures and ice wall thicknesses for overhead lines are determined at a height of 10 m above the ground with a repeatability of 1 time in 25 years (normative values).

2.5.41

Standard wind pressure corresponding to a 10-minute averaging interval of wind speed (), at a height of 10 m above the earth's surface, is taken according to Table 2.5.1 in accordance with the zoning map of the territory of Russia by wind pressure (Fig. 2.5.1) or according to regional maps zoning.

Table 2.5.1 Standard wind pressure at a height of 10 m above the ground

The standard wind pressure obtained during processing of meteorological data should be rounded to the nearest higher value given in Table 2.5.1.

Wind pressure is determined by the formula, Pa

Wind pressure over 1500 Pa should be rounded to the nearest higher multiple of 250 Pa.

For 110-750 kV overhead lines, the standard wind pressure must be taken to be at least 500 Pa.

For overhead lines constructed in hard-to-reach areas, it is recommended that the wind pressure corresponding to the region be one higher than that accepted for a given region according to regional zoning maps or based on the processing of long-term observation materials.

2.5.42

For sections of overhead lines constructed in conditions conducive to a sharp increase in wind speeds (high bank of a large river, a hill that stands out sharply above the surrounding area, ridge zones of ridges, intermountain valleys open to strong winds, coastal strip of seas and oceans, large lakes and reservoirs within 3-5 km), in the absence of observational data, the standard wind pressure should be increased by 40% compared to that accepted for the given area. The resulting values ​​should be rounded to the nearest value indicated in Table 2.5.1.

2.5.43

Standard wind pressure during ice conditions with a repeatability of 1 time in 25 years is determined by formula 2.5.41, based on wind speed during ice conditions.

Wind speed is taken according to the regional zoning of wind loads during ice conditions or determined from observational data in accordance with methodological guidelines for calculating climatic loads. In the absence of regional maps and observational data. For overhead lines up to 20 kV, the standard wind pressure during ice conditions should be at least 200 Pa, for overhead lines 330-750 kV - at least 160 Pa.

Standard wind pressures (wind speeds) during ice conditions are rounded to the nearest following values, Pa (m/s): 80 (11), 120 (14), 160 (16), 200 (18), 240 (20), 280 (21 ), 320 (23), 360 (24).

Values ​​greater than 360 Pa should be rounded to the nearest multiple of 40 Pa.

2.5.44

Wind pressure on the overhead line wires is determined by the height of the location of the reduced center of gravity of all wires, on the cables - by the height of the location of the center of gravity of the cables, on the structure of the overhead line supports - by the height of the midpoints of the zones, measured from the mark of the ground surface at the location of the support. The height of each zone should be no more than 10 m.

For different heights of the center of gravity of wires, cables, as well as midpoints of the overhead line support structure zones, wind pressure is determined by multiplying its value by the coefficient taken according to Table 2.5.2.

Table 2.5.2 Change in height coefficient depending on the type of terrain

The height of the location of the reduced center of gravity of wires, cables and midpoints of the zones of overhead line support structures above the ground surface, m	Coefficient for terrain types
	A	IN	WITH
Up to 15	1,00	0,65	0,40
20	1,25	0,85	0,55
40	1,50	1,10	0,80
60	1,70	1,30	1,00
80	1,85	1,45	1,15
100	2,00	1,60	1,25
150	2,25	1,90	1,55
200	2,45	2,10	1,80
250	2,65	2,30	2,00
300	2,75	2,50	2,20
350 and above	2,75	2,75	2,35

Note. Terrain types are as defined in 2.5.6.

The resulting wind pressure values ​​must be rounded to the nearest whole number.

For intermediate heights, the coefficient values ​​are determined by linear interpolation.

The height of the reduced center of gravity of wires or cables for the overall span is determined by the formula, m

,

where is the arithmetic mean value of the height of fastening the wires to the insulators or the arithmetic mean value of the height of fastening the cables to the support, measured from the ground marks at the places where the supports are installed, m;

Sag of a wire or cable in the middle of the span at the highest temperature, m.

2.5.45

When calculating wires and cables, the wind should be taken to be directed at an angle of 90° to the axis of the overhead line.

When calculating supports, the wind should be taken as directed at an angle of 0°, 45° and 90° to the overhead line axis, while for corner supports the direction of the bisector of the external rotation angle formed by adjacent sections of the line is taken as the overhead line axis.