Whether or not to combine grounding and lightning protection. Lightning protection and grounding circuit. External and internal lightning protection

The need to electrically connect the ground loop of lightning protection installed directly on the building with the ground loop for electrical installations is prescribed in the current regulatory documents (PUE). We quote verbatim: "Grounding devices for protective grounding of electrical installations of buildings and structures and lightning protection of the 2nd and 3rd categories of these buildings and structures, as a rule, should be common." Just the 2nd and 3rd categories are the most common, the 1st category includes explosive objects to lightning protection of which increased requirements are imposed. However, the existence of the phrase "as a rule" implies the possibility of exceptions.

Modern office and now residential buildings contain many engineering life support systems. It is difficult to imagine the absence of ventilation systems, fire extinguishing, video surveillance, access control, etc. Naturally, the designers of such systems have concerns that as a result of the action of lightning, “delicate” electronics will fail. At the same time, practitioners have some doubts about the expediency of connecting the contours of two types of grounding and there is a desire "within the law" to design electrically unrelated groundings. Is such an approach possible and will it actually increase the safety of electronic devices?

Why is it necessary to combine ground loops?

When lightning strikes a lightning rod, a short electrical impulse with a voltage of up to hundreds of kilovolts occurs in the latter. At such a high voltage, breakdown of the gap between the lightning rod and metal structures home, including electrical cables. The consequence of this will be the occurrence of uncontrolled currents that can lead to fire, failure of electronics and even the destruction of infrastructure elements (for example, plastic water pipes). Experienced electricians say: "Give lightning a way, otherwise it will find it itself." That is why the electrical connection of earths is mandatory.

For the same reason, the PUE recommends electrically combining not only groundings located in the same building, but also groundings of geographically adjacent objects. This concept refers to objects whose groundings are so close that there is no zone of zero potential between them. The combination of several groundings into one is carried out, in accordance with the norms of PUE-7, clause 1.7.55, by connecting the ground electrodes with electrical conductors in the amount of at least two pieces. Moreover, the conductors can be both natural (for example, metal elements of the building structure) and artificial (wires, rigid tires, etc.).

One common or separate grounding devices?

Earthing conductors for electrical installations and lightning protection have different requirements, and this circumstance can be a source of some problems. A grounding conductor for lightning protection must divert a large electric charge into the ground in a short time. At the same time, according to the "Instructions for lightning protection RD 34.21.122-87", the design of the ground electrode is standardized. For a lightning rod, according to this instruction, at least two vertical or radial horizontal ground electrodes are required, with the exception of lightning protection category 1, when three such pins are needed. That is why the most common grounding option for a lightning rod is two or three rods, each about 3 m long, connected by a metal strip buried at least 50 cm into the ground. When using parts manufactured by ZANDZ, such a grounding device turns out to be durable and easy to install.

A completely different matter is grounding for electrical installations. In the normal case, it should not exceed 30 ohms, and for some applications described in departmental instructions, for example, for cellular equipment, 4 ohms or even less. Such grounding conductors are pins more than 10 m long or even metal plates placed at a great depth (up to 40 m), where even in winter there is no freezing of the soil. To create such a lightning rod with the deepening of two or more elements by tens of meters is too expensive.

If the soil parameters and the requirements for resistance make it possible to perform a single grounding in a building for a lightning rod and grounding of electrical installations, there are no obstacles to doing it. In other cases, various ground loops are made for lightning rods and electrical installations, but they must be connected electrically, preferably in the ground. An exception is the use of some special equipment that is particularly sensitive to interference. For example, sound recording equipment. Such equipment requires a separate, so-called technological grounding device, which is directly indicated in the instructions. In this case, a separate grounding device is made, which is connected to the potential equalization system of the building through the main grounding bus. And, if such a connection is not provided for by the instruction manual for the equipment, then special measures are taken to prevent people from simultaneously touching the specified equipment and the metal parts of the building.

Electrical connection of earths

A circuit with several earths connected electrically provides for the fulfillment of different, sometimes conflicting, requirements for earthing devices. According to the PUE, grounding, like many other metal elements of the building, as well as the equipment installed in it, must be connected by a potential equalization system. Potential equalization refers to the electrical connection of conductive parts to achieve potential equality. Distinguish between the main and additional potential equalization systems. Groundings are connected to the main potential equalization system, that is, they are interconnected through the main grounding bus. The wires connecting the grounds to this bus must be connected according to the radial principle, that is, one branch from the specified bus goes to only one ground.

In order to ensure the safe operation of the entire system, it is very important to use the most reliable connection between the grounds and the main ground bus, which will not be destroyed by lightning. To do this, you must comply with the rules of the PUE and GOST R 50571.5.54-2013 “Low-voltage electrical installations. Part 5-54. Grounding devices, protective conductors and potential equalization protective conductors” regarding the cross section of the potential equalization system wires and their interconnection.

However, even a very high-quality potential equalization system cannot guarantee the absence of voltage surges in the network when a lightning strikes a building. Therefore, along with well-designed ground loops, surge protection devices (SPDs) will save you from problems. Such protection is multistage and selective. That is, a set of SPDs should be installed on the object, the selection of elements of which is not an easy task even for an experienced specialist. Fortunately, ready-made SPD kits are available for typical applications.

conclusions

The recommendation of the Electrical Installation Code on the electrical connection of all ground loops in the building is reasonable and, if implemented correctly, not only does not create a danger to complex electronic equipment, but, on the contrary, protects it. In the event that the equipment is sensitive to lightning interference and requires its own separate earthing, a separate process earth can be installed in accordance with the manual supplied with the equipment. The potential equalization system, which combines disparate ground loops, must provide a reliable electrical connection and largely determines the overall level of electrical safety at the facility, so special attention should be paid to it.

Introduction - about the role of grounding in a private house

The house has just been built or bought - in front of you is exactly the cherished home that you recently saw on a sketch or photograph in an ad. Or maybe you live in own house not the first year, and every corner in it has become native. Owning your own personal home is great, but along with the feeling of freedom, in addition you get a number of responsibilities. And now we will not talk about household chores, we will talk about such a need as grounding for a private house. Any a private house includes the following systems: electrical network, water supply and sewerage, gas or electric heating system. Additionally, a security and alarm system, ventilation, a smart home system, etc. are installed. Thanks to these elements, a private house becomes a comfortable living environment modern man. But it really comes to life thanks to the electrical energy that powers the equipment of all the above systems.

The need for grounding

Unfortunately, electricity has reverse side. All equipment has a service life, each device has a certain reliability, so they will not work forever. In addition, when designing or installing the house itself, electricians, communications or equipment, mistakes can also be made that can affect electrical safety. For these reasons, part of the electrical network may be damaged. The nature of accidents is different: short circuits can occur, which are turned off circuit breakers, and breakdowns on the body may occur. The difficulty is that the breakdown problem is hidden. There was damage to the wiring, so the body of the electric stove was energized. With improper grounding measures, damage will not manifest itself in any way until a person touches the stove and receives an electric shock. An electric shock will happen due to the fact that the current is looking for a path to the ground, and the only suitable conductor will be the human body. This cannot be allowed.

Such damage poses the greatest threat to people's safety, because for their early detection, and, therefore, to protect against them, it is imperative to have a ground connection. This article discusses what actions need to be taken to organize grounding for a private house or cottage.

The need to install grounding in a private house is determined by the grounding system, i.e. the neutral mode of the power source and the method of laying the zero protective (PE) and zero working (N) conductors. The type of power supply may also be important - overhead line or cable. The design differences in grounding systems make it possible to distinguish three options for power supply of a private house:

The main potential equalization system (OSUP) combines all large conductive parts of the building, which normally do not have an electrical potential, into a single circuit with the main ground bus. Let's consider a graphical example of the implementation of the EMS in the electrical installation of a residential building.

Let's first look at the most progressive approach to the electrical supply of the house - the TN-S system. In this system, PE and N conductors are separated throughout, and the consumer does not need to install grounding. It is only necessary to bring the PE conductor to the main ground bus, and then separate the ground conductors from it to electrical appliances. Such a system is implemented both as a cable and overhead line, in the case of the latter, a VLI (isolated overhead line) is laid using self-supporting wires (SIP).

But such happiness does not fall to everyone, because the old air lines transmissions use the old grounding system - TN-C. What is its feature? In this case, PE and N are laid along the entire length of the line by one conductor, in which the functions of both the zero protective and zero working conductors are combined - the so-called PEN conductor. If earlier it was allowed to use such a system, then with the introduction in 2002 of the PUE 7th edition, namely clause 1.7.80, the use of RCDs in the TN-C system was banned. Without the use of RCDs, there can be no talk of any electrical safety. It is the RCD that turns off the power when the insulation is damaged, as soon as it occurs, and not at the moment when a person touches the emergency device. To meet all the necessary requirements, the TN-C system must be upgraded to TN-C-S.

In the TN-C-S system, a PEN conductor is also laid along the line. But, now, paragraph 1.7.102 PUE 7th ed. says that re-grounding of the PEN conductor must be performed at the inputs of the overhead lines to electrical installations. They are performed, as a rule, at the electric pole from which the input is performed. When re-grounding is performed PEN division-conductor to separate PE and N, which are brought into the house. The re-grounding norm is contained in paragraph 1.7.103 of the PUE 7 ed. and is 30 ohms, or 10 ohms (if there is a gas boiler). If the grounding at the pole is not completed, it is necessary to contact Energosbyt, in whose department the electric pole, switchboard and input to the consumer's house is located, and point out the violation that must be corrected. If the switchboard is located in the house, PEN separation must be done in this switchboard, and re-grounding should be done near the house.

In this form, TN-C-S is successfully operated, but with some reservations:

if the condition of the overhead line raises serious concerns: the old wires are not in the best condition, because of which there is a risk of breakage or burnout of the PEN conductor. This is fraught with increased voltage on the grounded housings of electrical appliances, because. the current path to the line through the working zero will be interrupted, and the current will return from the bus on which the separation was performed through the zero protective conductor to the device case;
if re-groundings are not made on the line, then there is a danger that the fault current will flow into the only re-grounding, which will also lead to an increase in the voltage on the case.

In both cases, electrical safety leaves much to be desired. The solution to these problems is the TT system.

In the TT system, the PEN conductor of the line is used as a working zero, and individual grounding is performed separately, which can be installed near the house. Paragraph 1.7.59 PUE 7th ed. stipulates such a case when it is impossible to ensure electrical safety, and allows the use of a TT system. An RCD must be installed, and its correct operation must be ensured by the condition Ra * Ia<=50 В (где Iа - ток срабатывания защитного устройства; Ra - суммарное сопротивление заземлителя). «Инструкция по устройству защитного заземления» 1.03-08 уточняет, что для соблюдения этого условия сопротивление заземляющего устройства должно быть не более 30 Ом, а в грунтах с высоким удельным сопротивлением - не более 300 Ом.

How to make grounding at home?

The purpose of grounding for a private house is to obtain the necessary grounding resistance. For this, vertical and horizontal electrodes are used, which together should provide the necessary current spreading. Vertical earthing switches are suitable for installation in soft ground, while in stony soil their penetration is associated with great difficulties. In such soil, horizontal electrodes are suitable.

Protective grounding and lightning protection grounding are carried out in common, one grounding conductor will be universal and fulfill both purposes, this is stated in paragraph 1.7.55 of PUE 7th ed. Therefore, it will be useful to learn how to unify lightning protection and grounding. To visually see the installation process of these systems, the description of the grounding process for a private house will be divided into stages.

Protective grounding in the TN-S system should be highlighted as a separate item. The starting point for the installation of grounding will be the type of power system. The differences in power systems were discussed in the previous paragraph, so we know that it is not necessary to install grounding for the TN-S system, the zero protective (grounding) conductor comes from the line - you only need to connect it to the main grounding bus, and there will be grounding in the house. But one cannot say that the house does not need lightning protection. This means that we, without paying attention to stages 1 and 2, can immediately go to stages 3-5, see below
TN-C and TT systems always require grounding, so let's move on to the most important thing.

Protective grounding is installed at the pole or at the wall of the house, depending on where the PEN conductor is separated. It is advisable to place the ground electrode in close proximity to the main ground bus. The only difference between TN-C and TT is that in TN-C the grounding point is tied to the PEN separation point. Grounding resistance in both cases should be no more than 30 ohms in soil with a resistivity of 100 ohm * m, for example, loam, and 300 ohms in soil with a resistivity of more than 1000 ohm * m. The values are the same, although we rely on different standards: for the TN-C system 1.7.103 PUE 7th edition, and for the TT system - on clause 1.7.59 PUE and 3.4.8. Instructions I 1.03-08. Since there are no differences in the necessary measures, we will consider general solutions for these two systems.

For grounding, it is enough to hammer a six-meter vertical electrode.

(click to enlarge)

Such grounding turns out to be very compact, it can be installed even in the basement, no regulatory documents contradict this. The necessary steps for grounding are described for soft ground with a resistivity of 100 ohm*m. If the soil has a higher resistance, additional calculations are required, contact for help in calculations and selection of materials.

If a gas boiler is installed in the house, then the gas service may require grounding with a resistance of not more than 10 ohms, guided by paragraph 1.7.103 of PUE 7 ed. This requirement should be reflected in the gasification project.
Then, in order to achieve the norm, it is necessary to install a 15-meter vertical ground electrode, which is installed at one point.

(click to enlarge)

You can install it at several points, for example, at two or three, then connecting it with a horizontal electrode in the form of a strip along the wall of the house at a distance of 1 m and at a depth of 0.5-0.7 m. Installing a ground electrode at several points will also serve for the purpose of lightning protection To understand how, let's move on to its consideration.

Before installing the grounding, you need to immediately decide whether the house will be protected from lightning. So, if the configuration of the grounding conductor for protective grounding can be any, then the grounding for lightning protection must be of a certain type. A minimum of 2 vertical electrodes 3 meters long are installed, united by a horizontal electrode of such length that there is at least 5 meters between the pins. This requirement is contained in clause 2.26 of RD 34.21.122-87. Such grounding should be mounted along one of the walls of the house, it will be a kind of connection in the ground of two down conductors lowered from the roof. If there are several down conductors, the right solution is to lay a ground loop for the house at a distance of 1 m from the walls at a depth of 0.5-0.7 m, and install a vertical electrode 3 m long at the junction with the down conductor.

(click to enlarge)

Now it's time to learn how to make lightning protection for a private house. It consists of two parts: external and internal.

It is carried out in accordance with SO 153-34.21.122-2003 "Instruction for the installation of lightning protection for buildings, structures and industrial communications" (hereinafter referred to as CO) and RD 34.21.122-87 "Instruction for the installation of lightning protection for buildings and structures" (hereinafter RD).

Protection of buildings from lightning discharges is carried out with the help of lightning rods. A lightning rod is a device that rises above the protected object, through which the lightning current, bypassing the protected object, is diverted to the ground. It consists of a lightning rod that directly perceives a lightning discharge, a down conductor and a ground electrode.

Lightning rods are installed on the roof in such a way that the reliability of protection is more than 0.9 for CO, i.e. the probability of a breakthrough through the lightning protection system should be no more than 10%. For more information about what protection reliability is, read the article "Lightning protection of a private house". As a rule, they are installed along the edges of the roof ridge, if the roof is gable. When the roof is mansard, hipped or even more complex, lightning rods can be fixed on chimneys.
All lightning rods are interconnected by down conductors, down conductors are carried out to the grounding device, which we already have.

(click to enlarge)

Installing all these elements will protect the house from lightning, or rather from the danger posed by its direct strike.

Surge protection of the house is carried out with the help of SPDs. For their installation, grounding is necessary, because the current is diverted to the ground using zero protective conductors connected to the contacts of these devices. Installation options depend on the presence or absence of external lightning protection.

Has external lightning protection
In this case, a classic protective cascade is installed from devices of classes 1, 2 and 3 arranged in series. SPD of class 1 is mounted on the input and limits the current of a direct lightning strike. A class 2 SPD is also installed either in the input switchboard or in the distribution switchboard, if the house is large and the distance between the switchboards is more than 10 m. It is designed to protect against induced overvoltages, it limits them to a level of 2500 V. If the house has sensitive electronics, then it is desirable to install a class 3 SPD that limits overvoltages to the level of 1500 V; most devices can withstand such a voltage. SPD of class 3 is installed directly at such devices.
No external lightning protection
A direct lightning strike into the house is not taken into account, so there is no need for a class 1 SPD. The remaining SPDs are installed in the same way as described in point 1. The choice of SPD also depends on the earthing system, to be sure of the correct choice, contact .

The figure shows a house with a protective earth, an external lightning protection system and a combined SPD of class 1 + 2 + 3 installed, designed for installation in a TT system.

Comprehensive home protection: protective grounding, external lightning protection system and
combined SPD class 1+2+3, designed for installation in a TT system
(click to enlarge)

An enlarged image of a shield with an installed SPD for the house
(click to enlarge)

No. p / p	Rice	vendor code	Product	Qty
Lightning protection system
1		ZANDZ Air terminal mast vertical 4 m (stainless steel)	2
2		GALMAR Holder for lightning rod - mast ZZ-201-004 to the chimney (stainless steel)	2
3		GALMAR Clamp to lightning rod - mast GL-21105G for down conductors (stainless steel)	2
4		GALMAR Copper-plated steel wire (D8 mm; coil 50 meters)	1
5		GALMAR Copper-clad steel wire (D8 mm; coil 10 meters)	1
6		GALMAR Downpipe clamp for down conductor (tin-plated copper + tin-plated brass)	18
7		GALMAR Universal roof clamp for down conductor (height up to 15 mm; painted galvanized steel)	38
8		GALMAR Clamp to the facade/wall for a down conductor with an elevation (height 15 mm; galvanized steel with painting)	5
9

MINISTRY OF ENERGY OF THE RUSSIAN FEDERATION

APPROVED
order of the Ministry of Energy of Russia
dated 30.06.2003 No. 280

INSTRUCTIONS FOR THE DEVICE OF LIGHTNING PROTECTION OF BUILDINGS, CONSTRUCTIONS AND INDUSTRIAL COMMUNICATIONS

SO 153-34.21.122-2003

UDC 621.316(083.13)

The instruction applies to all types of buildings, structures and industrial communications, regardless of departmental affiliation and form of ownership.

For managers and specialists of design and operating organizations.

1. INTRODUCTION

Instructions for the installation of lightning protection of buildings, structures and industrial communications (hereinafter referred to as the Instruction) apply to all types of buildings, structures and industrial communications, regardless of departmental affiliation and form of ownership.

The instruction is intended for use in the development of projects, construction, operation, as well as in the reconstruction of buildings, structures and industrial communications.

In the case when the requirements of industry regulations are more stringent than in this Instruction, when developing lightning protection, it is recommended to comply with industry requirements. It is also recommended to act when the instructions of the Instruction cannot be combined with the technological features of the protected object. In this case, the means and methods of lightning protection used are selected based on the condition for ensuring the required reliability.

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

When normalizing lightning protection, it is assumed that any of its devices cannot prevent the development of lightning.

The application of the standard when choosing lightning protection significantly reduces the risk of damage from a lightning strike.

The type and placement of lightning protection devices are selected at the design stage of a new facility in order to be able to maximize the use of the conductive elements of the latter. This will facilitate the development and implementation of lightning protection devices combined with the building itself, will improve its aesthetic appearance, increase the effectiveness of lightning protection, minimize its cost and labor costs.

2. GENERAL PROVISIONS

2.1. Terms and Definitions

A lightning strike into the ground is an electrical discharge of atmospheric origin between a thundercloud and the ground, consisting of one or more current pulses.

Strike point - the point at which lightning contacts the ground, building or lightning protection device. A lightning strike can have multiple hit points.

Protected object - a building or structure, their part or space, for which lightning protection has been performed that meets the requirements of this standard.

Lightning protection device - a system that allows you to protect a building or structure from the effects of lightning. It includes external and internal devices. In particular cases, lightning protection may contain only external or only internal devices.

Protection devices against direct lightning strikes (lightning rods) - a complex consisting of lightning rods, down conductors and ground electrodes.

Secondary lightning protection devices are devices that limit the effects of electric and magnetic fields of lightning.

Potential equalization devices - elements of protection devices that limit the potential difference due to the spreading of lightning current.

Lightning rod - part of the lightning rod, designed to intercept lightning.

Down conductor (descent) - a part of the lightning conductor, designed to divert the lightning current from the lightning rod to the ground electrode.

Grounding device - a combination of grounding and grounding conductors.

Grounding conductor - a conductive part or a set of interconnected conductive parts that are in electrical contact with the ground directly or through a conductive medium.

Grounding loop - a grounding conductor in the form of a closed loop around the building in the ground or on its surface.

The resistance of the grounding device is the ratio of the voltage on the grounding device to the current flowing from the grounding conductor into the ground.

The voltage on the grounding device is the voltage that occurs when current drains from the ground electrode into the ground between the point of current input into the ground electrode and the zone of zero potential.

Interconnected metal reinforcement - reinforcement of reinforced concrete structures of a building (structure), which provides electrical continuity.

Dangerous sparking - an unacceptable electrical discharge inside the protected object, caused by a lightning strike.

Safe distance - minimum distance between two conductive elements outside or inside the protected object, in which no dangerous sparking can occur between them.

Surge protection device - a device designed to limit surges between the elements of the protected object (for example, a surge arrester, a non-linear surge arrester or other protective device).

Stand-alone lightning rod - a lightning rod, the lightning rods and down conductors of which are located in such a way that the lightning current path does not have contact with the protected object.

Lightning rod installed on the protected object - a lightning rod, the lightning rods and down conductors of which are located in such a way that part of the lightning current can spread through the protected object or its ground electrode.

The protection zone of a lightning rod is a space in the vicinity of a lightning rod of a given geometry, characterized in that the probability of a lightning strike into an object entirely located in its volume does not exceed a given value.

Permissible probability of a lightning breakthrough - the maximum permissible probability P of a lightning strike into an object protected by lightning rods.

The reliability of protection is defined as 1 - R.

Industrial communications - power and information cables, conductive pipelines, non-conductive pipelines with an internal conductive medium.

2.2. Classification of buildings and structures by lightning protection device

The classification of objects is determined by the danger of lightning strikes for the object itself and its environment.

The direct hazardous effects of lightning are fires, mechanical damage, injuries to people and animals, as well as damage to electrical and electronic equipment. The consequences of a lightning strike can be explosions and the release of hazardous products - radioactive and toxic chemicals, as well as bacteria and viruses.

Lightning strikes can be especially dangerous for information systems, control systems, control and power supply. For electronic devices installed in objects for various purposes, special protection is required.

The objects under consideration can be divided into ordinary and special.

Ordinary objects - residential and administrative buildings, as well as buildings and structures, not more than 60 m high, intended for trade, industrial production, agriculture.

Special objects:
objects that pose a danger to the immediate environment;
objects that pose a danger to the social and physical environment (objects that, when struck by lightning, can cause harmful biological, chemical and radioactive emissions);
other objects for which special lightning protection may be provided, for example, buildings over 60 m high, playgrounds, temporary structures, objects under construction.

In table. 2.1 gives examples of the division of objects into four classes.

Table 2.1

Examples of object classification

An object	Object type	Consequences of a lightning strike
Ordinary	House	Electrical failure, fire and property damage. Usually slight damage to objects located at the site of a lightning strike or affected by its channel
	Farm	Initially, a fire and a dangerous voltage drift, then a loss of power supply with the risk of death of animals due to a failure of the electronic control system for ventilation, feed supply, etc.
	Theater; school; Department store; sports facility	Power failure (e.g. lighting) that could cause panic. Failure of the fire alarm system causing a delay in fire fighting
	Bank; Insurance Company; commercial office	Power failure (e.g. lighting) that could cause panic. Failure of the fire alarm system causing a delay in fire fighting. Loss of communications, computer failures with data loss
	Hospital; kindergarten; nursing home	Power failure (e.g. lighting) that could cause panic. Failure of the fire alarm system causing a delay in fire fighting. Loss of communications, computer failures with data loss. The need to help seriously ill and immobile people
	Industrial enterprises	Additional consequences depending on the conditions of production - from minor damage to large damage due to product losses
	Museums and archaeological sites	Irreparable loss of cultural values
Special with limited danger	Means of communication; power plants; fire hazardous industries	Inadmissible violation of public services (telecommunications). Indirect fire hazard for neighboring objects
Special, dangerous to the immediate environment	Oil refineries; filling stations; production of firecrackers and fireworks	Fires and explosions inside the facility and in the immediate vicinity
Special, dangerous for the environment	Chemical factory; nuclear power plant; biochemical factories and laboratories	Fire and disruption of equipment with harmful consequences for the environment

During construction and reconstruction for each class of facilities, it is required to determine the necessary levels of reliability of protection against direct lightning strikes (DSL). For example, for ordinary objects, four levels of protection reliability can be proposed, indicated in Table. 2.2.

Table 2.2

Levels of protection against PIP for ordinary objects

Protection level	Reliability of protection against PUM
I	0,98
II	0,95
III	0,90
IV	0,80

For special objects, the minimum permissible level of reliability of protection against PIP is set within 0.9-0.999, depending on the degree of its social significance and the severity of the expected consequences from PIP, in agreement with the state control authorities.

At the request of the customer, the project may include a level of reliability that exceeds the maximum allowable.

2.3. Lightning current parameters

The parameters of lightning currents are necessary for calculating mechanical and thermal effects, as well as for standardizing means of protection against electromagnetic effects.

2.3.1. Classification of the effects of lightning currents

For each level of lightning protection, the maximum permissible parameters of the lightning current must be determined. The data given in the standard refer to downstream and upstream lightning.

The polarity ratio of lightning discharges depends on the geographic location of the area. In the absence of local data, this ratio is assumed to be 10% for discharges with positive currents and 90% for discharges with negative currents.

The mechanical and thermal effects of lightning are due to the peak value of the current I, the total charge Q total, the charge in the pulse Q imp and the specific energy W/R. The highest values of these parameters are observed for positive discharges.

The damage caused by induced overvoltages is due to the steepness of the lightning current front. The slope is rated within 30% and 90% levels of the highest current value. The highest value of this parameter is observed in subsequent pulses of negative discharges.

2.3.2. Parameters of lightning currents proposed for standardization of means of protection against direct lightning strikes

The values of the calculated parameters for those taken in the table. 2.2 security levels (with a ratio of 10% to 90% between the shares of positive and negative discharges) are given in Table. 2.3.

Table 2.3

Correspondence of lightning current parameters and protection levels

2.3.3. Density of lightning strikes to the ground

The density of lightning strikes to the ground, expressed in terms of the number of strikes per 1 km 2 of the earth's surface per year, is determined according to meteorological observations at the location of the object.

If the density of lightning strikes to the ground N g is unknown, it can be calculated using the following formula, 1/(km 2 year):

, (2.1)

where T d is the average duration of thunderstorms in hours, determined from regional maps of the intensity of thunderstorm activity.

2.3.4. Parameters of lightning currents proposed for standardization of means of protection against electromagnetic effects of lightning

In addition to mechanical and thermal effects, lightning current creates powerful pulses of electromagnetic radiation, which can cause damage to systems, including communication, control, automation equipment, computing and information devices, etc. These complex and expensive systems are used in many industries and businesses. Their damage as a result of a lightning strike is highly undesirable for safety reasons as well as for economic reasons.

A lightning strike can contain either a single current pulse, or consist of a sequence of pulses separated by time intervals, during which a weak follow current flows. The parameters of the current pulse of the first component differ significantly from the characteristics of the pulses of subsequent components. Below are the data characterizing the calculated parameters of the current pulses of the first and subsequent pulses (Tables 2.4 and 2.5), as well as long-term current (Table 2.6) in the pauses between pulses for ordinary objects at various levels of protection.

Table 2.4

Parameters of the first lightning current pulse

Current parameter	Protection level
Current parameter	I	II	III, IV
Maximum current I, kA	200	150	100
Rise time T 1 , µs	10	10	10
Half-time T 2 , µs	350	350	350
Charge in an impulse Qsum *, C	100	75	50
Specific pulse energy W/R**, MJ/Ohm	10	5,6	2,5

________________
* Since a significant part of the total charge Qsum falls on the first pulse, it is assumed that the total charge of all short pulses is equal to the given value.
** Since a significant part of the total specific energy W/R occurs in the first pulse, it is assumed that the total charge of all short pulses is equal to the given value.

Table 2.5

Parameters of subsequent lightning current impulse

Table 2.6

Parameters of long-term lightning current in the interval between impulses

______________
* Q dl - the charge due to the long-term current flow in the period between two lightning current pulses.

The average current is approximately equal to Q dl /T.

The shape of the current pulses is determined by the following expression:

where I is the maximum current;
h - coefficient correcting the value of the maximum current;
t - time;
τ 1 - time constant for the front;
τ 2 is the decay time constant.

The values of the parameters included in the formula (2.2), which describes the change in the lightning current over time, are given in Table. 2.7.

Table 2.7

Parameter values for calculating the shape of the lightning current pulse

Parameter	First impulse			Subsequent impulse
	Protection level			Protection level
	I	II	III, IV	I	II	III, IV
I, kA	200	150	100	50	37,5	25
h	0,93	0,93	0,93	0,993	0,993	0,993
τ 1 , ms	19,0	19,0	19,0	0,454	0,454	0,454
τ 2 , ms	485	485	485	143	143	143

A long pulse can be taken as a rectangular one with an average current I and a duration T corresponding to the data in Table. 2.6.

3. PROTECTION AGAINST DIRECT LIGHTNING

3.1. Complex of lightning protection means

The complex of lightning protection facilities for buildings or structures includes protection devices against direct lightning strikes (external lightning protection system - MZS) and devices for protection against secondary lightning effects (internal LZS). In particular cases, lightning protection may contain only external or only internal devices. In general, part of the lightning currents flows through the elements of internal lightning protection.

The external LSM can be isolated from the structure (separately standing lightning rods or cables, as well as neighboring structures that act as natural lightning rods) or can be installed on the protected structure and even be part of it.

Internal lightning protection devices are designed to limit the electromagnetic effects of the lightning current and prevent sparks inside the protected object.

Lightning currents falling into lightning rods are diverted to the grounding conductor through a system of down conductors (descents) and spread in the ground.

3.2. External lightning protection system

External MLT generally consists of lightning rods, down conductors and ground electrodes. In the case of special manufacture, their material and cross-sections must meet the requirements of Table. 3.1.

Table 3.1

Material and minimum cross-sections of elements of the outer ISM

Note. The indicated values may be increased depending on increased corrosion or mechanical influences.

3.2.1. Lightning rods

3.2.1.1. General Considerations

Lightning rods can be specially installed, including at the facility, or their functions are performed by structural elements of the protected facility; in the latter case they are called natural lightning rods.

Lightning rods can consist of an arbitrary combination of the following elements: rods, stretched wires (cables), mesh conductors (grids).

3.2.1.2. Natural lightning rods

The following structural elements of buildings and structures can be considered as natural lightning rods:

Table 3.2

The thickness of the roof, pipe or tank body, acting as a natural lightning rod

3.2.2. Down conductors

3.2.2.1. General Considerations

In order to reduce the likelihood of dangerous sparking, down conductors should be located in such a way that between the point of destruction and the ground:

3.2.2.2. Location of down conductors in lightning protection devices isolated from the protected object

If the lightning rod consists of rods installed on separate supports (or one support), at least one down conductor must be provided for each support.

If the lightning rod consists of separate horizontal wires (cables) or one wire (cable), at least one down conductor is required for each end of the cable.

If the lightning rod is a mesh structure suspended above the protected object, at least one down conductor is required for each of its supports. The total number of down conductors must be at least two.

3.2.2.3. Location of down conductors for non-insulated lightning protection devices

Down conductors are located along the perimeter of the protected object in such a way that the average distance between them is not less than the values given in Table. 3.3.

Down conductors are connected by horizontal belts near the ground surface and every 20 m along the height of the building.

Table 3.3

Average distances between down conductors depending on the level of protection

Protection level	Average distance, m
I	10
II	15
III	20
IV	25

3.2.2.4. Instructions for the placement of down conductors

It is desirable that down conductors are evenly located along the perimeter of the protected object. If possible, they are laid near the corners of buildings.

Down conductors not isolated from the protected object are laid as follows:

Down conductors should not be laid in downpipes. It is recommended to place down conductors at the maximum possible distance from doors and windows.

Down conductors are laid in straight and vertical lines so that the path to the ground is as short as possible. Laying down conductors in the form of loops is not recommended.

3.2.2.5. Natural elements of down conductors

The following structural elements of buildings can be considered natural down conductors:

Metal reinforcement of reinforced concrete structures is considered to provide electrical continuity if it satisfies the following conditions:

There is no need to lay horizontal belts if the metal frames of the building or steel reinforcement of reinforced concrete are used as down conductors.

3.2.3. Earthing switches

3.2.3.1. General Considerations

In all cases, with the exception of the use of a stand-alone lightning rod, the lightning protection earth electrode should be combined with the earth electrodes of electrical installations and means of communication. If these earthing switches must be separated for any technological reasons, they should be combined into a common system using a potential equalization system.

3.2.3.2. Specially laid ground electrodes

It is advisable to use the following types of ground electrodes: one or more circuits, vertical (or inclined) electrodes, radially divergent electrodes or a ground loop laid at the bottom of the pit, ground grids.

Deeply buried ground electrodes are effective if the resistivity of the soil decreases with depth and at great depths it turns out to be significantly less than at the level of the usual location.

The grounding conductor in the form of an external contour is preferably laid at a depth of at least 0.5 m from the surface of the earth and at a distance of at least 1 m from the walls. Grounding electrodes must be located at a depth of at least 0.5 m outside the protected object and be as evenly distributed as possible; in this case, one should strive to minimize their mutual shielding.

The depth of laying and the type of grounding electrodes are selected from the condition of ensuring minimal corrosion, as well as the smallest possible seasonal variation in grounding resistance as a result of drying and freezing of the soil.

3.2.3.3. Natural ground electrodes

Interconnected reinforced concrete reinforcement or other underground metal structures that meet the requirements of clause 3.2.2.5 can be used as grounding electrodes. If reinforced concrete reinforcement is used as grounding electrodes, increased requirements are placed on the places of its connections in order to exclude mechanical destruction of concrete. If prestressed concrete is used, consideration should be given to the possible consequences of the passage of lightning current, which can cause unacceptable mechanical loads.

3.2.4. Fastening and connection of elements of the external LSM

3.2.4.1. Fastening

Lightning rods and down conductors are rigidly fixed so as to exclude any rupture or loosening of the fastening of conductors under the action of electrodynamic forces or random mechanical influences (for example, from a gust of wind or a falling snow layer).

3.2.4.2. Connections

The number of conductor connections is reduced to a minimum. Connections are made by welding, soldering, insertion into a clamping lug or bolt fastening is also possible.

3.3. Choice of lightning rods

3.3.1. General Considerations

The choice of the type and height of lightning rods is made based on the values of the required reliability R z. An object is considered protected if the totality of all its lightning rods provides protection reliability of at least R s.

In all cases, the protection system against direct lightning strikes is chosen so that natural lightning rods are used to the maximum, and if the protection provided by them is insufficient - in combination with specially installed lightning rods.

In general, the choice of lightning rods should be made using appropriate computer programs that can calculate the protection zones or the probability of a lightning breakthrough into an object (group of objects) of any configuration with an arbitrary location of almost any number of lightning rods of various types.

Ceteris paribus, the height of lightning rods can be reduced if cable structures are used instead of rod structures, especially when they are suspended along the outer perimeter of the object.

If the protection of the object is provided by the simplest lightning rods (single rod, single cable, double rod, double cable, closed cable), the dimensions of the lightning rods can be determined using the protection zones specified in this standard.

In the case of lightning protection design for an ordinary object, it is possible to determine the protection zones by the protective angle or by the rolling sphere method according to the International Electrotechnical Commission standard (IEC 1024), provided that the calculation requirements of the International Electrotechnical Commission turn out to be more stringent than the requirements of this Instruction.

3.3.2. Typical protection zones of rod and wire lightning rods

3.3.2.1. Protection zones of a single rod lightning rod

The standard protection zone of a single rod lightning rod with height h is a circular cone with height h 0

The calculation formulas given below (Table 3.4) are suitable for lightning rods up to 150 m high. For higher lightning rods, a special calculation method should be used.

Rice. 3.1. Protection zone of a single rod lightning rod

For the protection zone of the required reliability (Fig. 3.1), the radius of the horizontal section r x at the height h x is determined by the formula:

(3.1)

Table 3.4

Calculation of the protection zone of a single rod lightning rod

Reliability of protection R s	Lightning rod height h, m	Cone height h 0, m	Cone radius r 0 , m
0,9	0 to 100	0.85h	1.2h
0,9	100 to 150	0.85h	h
0,99	0 to 30	0.8h	0.8h
	30 to 100	0.8h	h
	100 to 150	h	0.7h
0,999	0 to 30	0.7h	0.6h
	30 to 100	h	h
	100 to 150	h	h

3.3.2.2. Protection zones of a single wire lightning rod

The standard protection zones of a single wire lightning rod with a height h are limited by symmetrical gable surfaces that form an isosceles triangle in a vertical section with a vertex at a height h 0

The calculation formulas below (Table 3.5) are suitable for lightning rods up to 150 m high. For higher heights, special software should be used. Here and below, h is the minimum height of the cable above ground level (including sag).

Rice. 3.2. Protection zone of a single wire lightning rod:
L - distance between the suspension points of the cables

The half-width r x of the protection zone of the required reliability (Fig. 3.2) at a height h x from the earth's surface is determined by the expression:

If it is necessary to expand the protected volume, protection zones of bearing supports can be added to the ends of the protection zone of the wire lightning rod itself, which are calculated by the formulas of single rod lightning rods, presented in Table. 3.4. In the case of large cable sags, for example, at overhead power lines, it is recommended to calculate the provided probability of lightning breakthrough by software methods, since the construction of protection zones according to the minimum cable height in the span can lead to unjustified costs.

Table 3.5

Calculation of the protection zone of a single wire lightning rod

Reliability of protection R s	Lightning rod height h, m	Cone height h 0, m	Cone radius r 0 , m
0,9	0 to 150	0.87h	1.5h
0,99	0 to 30	0.8h	0.95h
	30 to 100	0.8h	h
	100 to 150	0.8h	h
0,999	0 to 30	0.75h	0.7h
	30 to 100	h	h
	100 to 150	h	h

3.3.2.3. Protection zones of a double lightning rod

The lightning rod is considered double when the distance between the rod lightning rods L does not exceed the limit value L max . Otherwise, both lightning rods are considered as single.

The configuration of vertical and horizontal sections of standard protection zones of a double rod lightning rod (height h and distance L between lightning rods) is shown in fig. 3.3. The construction of the outer areas of the zones of a double lightning rod (half-cones with dimensions h 0, r 0) is carried out according to the formulas of Table. 3.4 for single rod lightning rods. The dimensions of the internal areas are determined by the parameters h 0 and h c , the first of which sets the maximum height of the zone directly at the lightning rods, and the second - the minimum height of the zone in the middle between the lightning rods. With a distance between lightning rods L ≤ L c, the zone boundary has no sag (h c = h 0). For distances L c ≤ L ≥ L max, the height h c is determined by the expression

(3.3)

The limiting distances L max and L c included in it are calculated according to the empirical formulas of Table. 3.6, suitable for lightning rods up to 150 m high. For higher lightning rod heights, special software should be used.

The dimensions of the horizontal sections of the zone are calculated according to the following formulas, common for all levels of protection reliability:

Rice. 3.3. Protection zone of a double rod lightning rod

Table 3.6

Calculation of the parameters of the protection zone of a double rod lightning rod

Reliability of protection R s	Lightning rod height h, m	Lmax, m	L0, m
0,9	0 to 30	5.75h	2.5h
	30 to 100	h	2.5h
	100 to 150	5.5h	2.5h
0,99	0 to 30	4.75h	2.25h
	30 to 100	h	h
	100 to 150	4.5h	1.5h
0,999	0 to 30	4.25h	2.25h
	30 to 100	h	h
	100 to 150	4.0h	1.5h

3.3.2.4. Protection zones of a double wire lightning rod

The lightning rod is considered double when the distance between the cables L does not exceed the limit value L max . Otherwise, both lightning rods are considered as single.

The configuration of vertical and horizontal sections of standard protection zones of a double wire lightning rod (height h and distance between wires L) is shown in fig. 3.4. The construction of the outer regions of the zones (two shed surfaces with dimensions h 0, r 0) is carried out according to the formulas of Table. 3.5 for single wire lightning rods.

Rice. 3.4. Protection zone of a double wire lightning rod

The dimensions of the inner regions are determined by the parameters h 0 and h c , the first of which sets the maximum height of the zone directly at the cables, and the second - the minimum height of the zone in the middle between the cables. With a distance between the cables L≤L c, the zone boundary has no sag (h c = h 0). For distances L c L≤L max height h c is determined by the expression

(3.7)

The limiting distances Lmax and Lc included in it are calculated according to the empirical formulas of Table. 3.7, suitable for cables with a suspension height of up to 150 m. With a higher height of lightning rods, special software should be used.

The length of the horizontal section of the protection zone at a height h x is determined by the formulas:

l x \u003d L / 2 for h c ≥ h x;

(3.8)

To expand the protected volume, the zone of protection of the supports carrying the cables can be imposed on the zone of the double wire lightning rod, which is built as the zone of the double rod lightning rod, if the distance L between the supports is less than L max calculated by the formulas of Table. 3.6. Otherwise, the supports should be considered as single lightning rods.

When the cables are not parallel or of different heights, or their height varies along the length of the span, special software should be used to assess the reliability of their protection. It is also recommended to proceed with large cable sags in the span in order to avoid excessive safety margins.

Table 3.7

Calculation of the parameters of the protection zone of a double wire lightning rod

Reliability of protection R s	Lightning rod height h, m	Lmax, m	L c , m
0,9	from 0 to 150	6.0h	3.0h
0,99	from 0 to 30	5.0h	2.5h
	from 30 to 100	5.0h	h
	from 100 to 150	h	h
0,999	from 0 to 30	4.75h	2.25h
	from 30 to 100	h	h
	from 100 to 150	h	h

3.3.2.5 Protection zones of a closed wire lightning rod

The calculation formulas of clause 3.3.2.5 can be used to determine the height of the suspension of a closed wire lightning rod, designed to protect objects with the required reliability with a height h 0

Rice. 3.5. Protection zone of a closed wire lightning rod

To calculate h, the expression is used:

h = A + Bh0, (3.9)

in which the constants A and B are determined depending on the level of protection reliability according to the following formulas:

a) reliability of protection Р s = 0.99

b) reliability of protection Р s = 0.999

The calculated ratios are valid when D > 5 m. Operation with smaller horizontal displacements of the cable is inappropriate due to the high probability of reverse lightning flashes from the cable to the protected object. For economic reasons, closed wire lightning rods are not recommended when the required protection reliability is less than 0.99.

If the height of the object exceeds 30 m, the height of the closed wire lightning rod is determined using software. The same should be done for a closed contour of a complex shape.

After choosing the height of the lightning rods according to their protection zones, it is recommended to check the actual probability of a breakthrough by computer means, and in case of a large safety margin, make an adjustment by setting a lower height of the lightning rods.

Below are the rules for determining protection zones for objects up to 60 m high, set out in the IEC standard (IEC 1024-1-1). When designing, any method of protection can be chosen, however, practice shows the feasibility of using individual methods in the following cases:

In table. 3.8 for protection levels I - IV, the values of the angles at the top of the protection zone, the radii of the fictitious sphere, as well as the maximum allowable grid cell step are given.

Table 3.8

Parameters for the calculation of lightning rods according to IEC recommendations

Protection level	Fictitious sphere radius R, m	Corner a, °, at the top of the lightning rod for buildings of different heights h, m				Grid cell pitch, m
Protection level	Fictitious sphere radius R, m	20	30	45	60	Grid cell pitch, m
I	20	25	*	*	*	5
II	30	35	25	*	*	10
III	45	45	35	25	*	10
IV	60	55	45	35	25	20

_______________
* In these cases, only grids or dummy spheres are applicable.

Rod lightning rods, masts and cables are placed so that all parts of the structure are in the protection zone formed at an angle a to the vertical. The protective angle is selected according to the table. 3.8, where h is the height of the lightning rod above the surface to be protected.

The protective corner method is not used if h is greater than the radius of the fictitious sphere defined in Table 1. 3.8 for the appropriate level of protection.

The fictitious sphere method is used to determine the protection zone for a part or areas of a structure when, according to Table. 3.4, the definition of the protection zone by the protective angle is excluded. The object is considered protected if the fictitious sphere, touching the surface of the lightning rod and the plane on which it is installed, has no common points with the protected object.

The mesh protects the surface if the following conditions are met:

dimensions

Mesh conductors should be laid as short as possible.

3.3.4. Protection of electric metal cable transmission lines of trunk and intrazonal communication networks

3.3.4.1. Protection of newly designed cable lines

On newly designed and reconstructed cable lines of the main and intrazonal communication networks 1, protective measures should be provided without fail in those sections where the probable damage density (the probable number of dangerous lightning strikes) exceeds the allowable one indicated in Table. 3.9.

___________________
1 Backbone networks - networks for transmitting information over long distances; intrazonal networks - networks for the transmission of information between regional and district centers.

Table 3.9

Permissible number of dangerous lightning strikes per 100 km of track per year for electric communication cables

cable type	Permissible estimated number of dangerous lightning strikes per 100 km of the route per year n 0
cable type	in mountainous areas and areas with rocky soil with a resistivity above 500 Ohm m and in permafrost areas	in other areas
Symmetrical single-quad and single-coaxial	0,2	0,3
Symmetrical four- and seven-four	0,1	0,2
Multi-pair coaxial	0,1	0,2
Zone communication cables	0,3	0,5

3.3.4.2. Protection of new lines laid near existing ones

If the cable line being designed is laid near the existing cable line and the actual number of damages to the latter during its operation for a period of at least 10 years is known, then when designing cable protection against lightning strikes, the norm for the allowable damage density should take into account the difference between the actual and calculated damage to the existing cable line.

In this case, the allowable damage density n 0 of the designed cable line is found by multiplying the allowable density from Table. 3.9 on the ratio of the calculated n p and actual n f damage of the existing cable from lightning strikes per 100 km of the route per year:

3.3.4.3. Protection of existing cable lines

On existing cable lines, protective measures are carried out in those areas where lightning strikes have occurred, and the length of the protected section is determined by the terrain conditions (the length of a hill or a section with increased soil resistivity, etc.), but at least 100 m is taken into each side of the injury. In these cases, it is planned to lay lightning protection cables in the ground. If a cable line that already has protection is damaged, then after the damage is eliminated, the state of the lightning protection means is checked and only after that a decision is made to equip additional protection in the form of laying cables or replacing the existing cable with a more resistant to lightning discharges. Protection work should be carried out immediately after the lightning damage has been eliminated.

3.3.5. Protection of optical cable transmission lines of trunk and intrazonal communication networks

3.3.5.1. Permissible number of dangerous lightning strikes into optical lines of backbone and intrazonal communication networks

On the designed optical cable transmission lines of the backbone and intrazonal communication networks, protective measures against damage by lightning strikes are mandatory in those areas where the probable number of dangerous lightning strikes (probable damage density) into the cables exceeds the allowable number indicated in Table. 3.10.

Table 3.10

Permissible number of dangerous lightning strikes per 100 km of track per year for optical communication cables

When designing optical cable transmission lines, it is envisaged to use cables with a lightning resistance category not lower than those given in Table. 3.11, depending on the purpose of the cables and laying conditions. In this case, when laying cables in open areas, protective measures may be required extremely rarely, only in areas with high soil resistivity and increased lightning activity.

Table 3.11

3.3.5.3. Protection of existing optical cable lines

On existing optical cable transmission lines, protective measures are taken in those areas where damage from lightning strikes occurred, and the length of the protected section is determined by the terrain conditions (the length of a hill or a section with increased soil resistivity, etc.), but must be at least 100 m in each direction from the place of damage. In these cases, it is necessary to provide for the laying of protective conductors.

Work on the equipment of protective measures should be carried out immediately after the elimination of lightning damage.

3.3.6. Protection against lightning strikes of electrical and optical communication cables laid in the settlement

When laying cables in a populated area, except for the case of crossing and approaching overhead lines with a voltage of 110 kV and above, protection against lightning strikes is not provided.

3.3.7. Protection of cables laid along the edge of the forest, near separate trees, supports, masts

Protection of communication cables laid along the edge of the forest, as well as near objects with a height of more than 6 m (single-standing trees, communication line supports, power lines, lightning rod masts, etc.) is provided if the distance between the cable and the object (or its underground part ) less than the distances given in Table. 3.12 for various values of earth resistivity.

Table 3.12

Permissible distances between the cable and the ground loop (support)

4. PROTECTION AGAINST SECONDARY IMPACTS OF LIGHTNING

4.1. General provisions

Section 4 outlines the basic principles of protection against secondary lightning effects of electrical and electronic systems, taking into account the recommendations of the IEC (Standard 61312). These systems are used in many industries that use fairly complex and expensive equipment. They are more sensitive to lightning than previous generations, so special measures must be taken to protect them from the dangerous effects of lightning.

The space in which electrical and electronic systems are located must be divided into zones of varying degrees of protection. The zones are characterized by a significant change in the electromagnetic parameters at the boundaries. In general, the higher the zone number, the lower the values of the parameters of electromagnetic fields, currents and voltages in the zone space.

Zone 0 is the zone where each object is subject to a direct lightning strike and therefore the full lightning current can flow through it. In this region, the electromagnetic field has a maximum value.

Zone 0 E - a zone where objects are not subject to a direct lightning strike, but the electromagnetic field is not weakened and also has a maximum value.

Zone 1 - a zone where objects are not subject to a direct lightning strike, and the current in all conductive elements inside the zone is less than in zone 0 E; in this area, the electromagnetic field can be weakened by shielding.

Other zones are set if further current reduction and/or attenuation is required. electromagnetic field; the requirements for the parameters of the zones are determined in accordance with the requirements for the protection of various zones of the object.

The general principles of dividing the protected space into lightning protection zones are shown in fig. 4.1.

At the borders of the zones, measures must be taken to shield and connect all metal elements and communications crossing the border.

Two spatially separated zones 1 can form a common zone using a shielded connection (Fig. 4.2).

Rice. 4.1. Lightning protection zones:
1 - ZONE 0 (external environment); 2 - ZONE 1 (internal electromagnetic environment); 3 - ZONE 2; 4 - ZONE 2 (situation inside the cabinet); 5 - ZONE 3

Rice. 4.2. Combining two zones

4.3. Shielding

Shielding is the main way to reduce electromagnetic interference.

The metal structure of a building structure is or may be used as a screen. Such a screen structure is formed, for example, by steel reinforcement of the roof, walls, floors of the building, as well as metal parts of the roof, facades, steel frames, gratings. This shielding structure forms an electromagnetic shield with openings (due to windows, doors, ventilation openings, mesh spacing in fittings, slots in a metal facade, openings for power lines, etc.). To reduce the influence of electromagnetic fields, all metal elements of the object are electrically combined and connected to the lightning protection system (Fig. 4.3).

If the cables pass between adjacent objects, the ground electrodes of the latter are connected to increase the number of parallel conductors and, due to this, reduce the currents in the cables. This requirement is well met by a grounding system in the form of a grid. To reduce induced noise, you can use:

All of these activities can be performed simultaneously.

If there are shielded cables inside the protected space, their shields are connected to the lightning protection system at both ends and at the zone boundaries.

Cables going from one object to another are laid along their entire length in metal pipes, mesh boxes or reinforced concrete boxes with mesh fittings. Metal elements of pipes, ducts and cable screens are connected to the specified common object busbars. Metal ducts or trays may not be used if the cable shields are capable of withstanding the expected lightning current.

Rice. 4.3. Combining metal elements of an object to reduce the influence of electromagnetic fields:

1 - welding at the intersections of wires; 2 - massive continuous door frame; 3 - welding on each rod

4.4. Connections

Connections of metal elements are necessary to reduce the potential difference between them inside the protected object. Connections of metal elements and systems located inside the protected space and crossing the boundaries of lightning protection zones are made at the boundaries of the zones. Connections should be made with special conductors or clamps and, where necessary, with surge protection devices.

4.4.1. Connections at zone boundaries

All conductors entering the object from the outside are connected to the lightning protection system.

If external conductors, power cables or communication cables enter the object at different points, and therefore there are several common busbars, the latter are connected via the shortest path to a closed ground loop or structural reinforcement and metal outer cladding (if any). If there is no closed ground loop, these common buses are connected to separate ground electrodes and connected by an external ring conductor or a broken ring. If the outer conductors enter an object above ground, the common busbars are connected to a horizontal ring conductor inside or outside the walls. This conductor, in turn, is connected to the lower conductors and fittings.

Conductors and cables entering the facility at ground level are recommended to be connected to the lightning protection system at the same level. The common bus at the point of entry of cables into the building is located as close as possible to the ground electrode and the fittings of the structure with which it is connected.

The ring conductor is connected to fittings or other shielding elements, such as metal cladding, every 5 m. The minimum cross-section of copper or galvanized steel electrodes is 50 mm 2.

General buses for objects with information systems, where the impact of lightning currents is supposed to be minimized, should be made of metal plates with a large number connections to fittings or other shielding elements.

For contact connections and surge protection devices located at the boundaries of zones 0 and 1, the current parameters specified in Table. 2.3. If there are several conductors, the distribution of currents along the conductors must be taken into account.

For conductors and cables entering an object at ground level, the part of the lightning current they conduct is estimated.

The cross sections of the connecting conductors are determined according to Table. 4.1 and 4.2. Tab. 4.1 is used if more than 25% of the lightning current flows through the conductive element, and tab. 4.2 - if less than 25%.

Table 4.1

Sections of conductors through which most of the lightning current flows

Table 4.2

Sections of conductors through which an insignificant part of the lightning current flows

The surge protective device is selected to withstand a part of the lightning current, limit surges and interrupt the follow currents after the main impulses.

The maximum overvoltage U max at the entrance to the object is coordinated with the withstand voltage of the system.

In order to minimize the value of U max, the lines are connected to a common bus with conductors of the minimum length.

All conductive elements such as cable lines, crossing the boundaries of lightning protection zones, are connected at these boundaries. The connection is carried out on a common bus, to which shielding and other metal elements (for example, equipment cases) are also connected.

For terminal clamps and surge suppressors, the current values are evaluated on a case by case basis. The maximum overvoltage at each boundary is coordinated with the system's withstand voltage. Surge protection devices at the boundaries of different zones are also coordinated in terms of energy characteristics.

4.4.2. Connections inside the protected volume

All internal conductive elements of significant size, such as elevator rails, cranes, metal floors, metal door frames, pipes, cable trays, are connected to the nearest common busbar or other common connecting element along the shortest path. Additional connections of conductive elements are also desirable.

The cross sections of the connecting conductors are indicated in Table. 4.2. It is assumed that only a small part of the lightning current passes in the connecting conductors.

All open conductive parts of information systems are connected into a single network. In special cases, such a network may not have a connection to the earth conductor.

There are two ways to connect metal parts of information systems, such as housings, shells or frames, to the earth electrode: connections are made in the form of a radial system or in the form of a grid.

When using a radial system, all its metal parts are isolated from the ground electrode throughout, except for the only connection point with it. Typically, such a system is used for relatively small objects, where all the elements and cables enter the object at one point.

The radial grounding system is connected to the common grounding system at only one point (Fig. 4.4). In this case, all lines and cables between devices in the equipment should be run parallel to the star earth conductors to reduce the inductance loop. Due to grounding at one point, low-frequency currents that appear during a lightning strike do not enter the information system. In addition, sources of low-frequency interference inside the information system do not create currents in the grounding system. Input into the protective zone of wires is carried out exclusively at the central point of the potential equalization system. The specified common point is also best place connection of surge protection devices.

When using a grid, its metal parts are not isolated from the common grounding system (Fig. 4.5). The grid connects to the overall system at many points. Typically mesh is used for extended open systems where equipment is connected by a large number of different lines and cables and where they enter the facility at various points. In this case, the entire system has low impedance at all frequencies. Besides, big number short-circuited grid contours weakens the magnetic field near the information system. Devices in the protection zone are connected to each other over the shortest distances by several conductors, as well as to the metal parts of the protected zone and the zone screen. In this case, the metal parts present in the device, such as fittings in the floor, walls and roof, metal gratings, non-electrical metal equipment, such as pipes, ventilation and cable ducts, are used to the maximum.

Rice. 4.4. Connection diagram for power supply and communication wires with a star-shaped potential equalization system:
1 - shield of the protective zone; 2 - electrical insulation; 3 - wire of the potential equalization system; 4 - the central point of the potential equalization system; 5 - communication wires, power supply

Rice. 4.5. Mesh implementation of the potential equalization system:
1 - shield of the protective zone; 2 - potential equalization conductor

Rice. 4.6. Integrated implementation of the potential equalization system:
1 - shield of the protective zone; 2 - electrical insulation; 3 - the central point of the potential equalization system

Both configurations, radial and mesh, can be combined into a complex system as shown in fig. 4.6. Usually, although it is not necessary, the connection of the local ground network with the common system is carried out at the border of the lightning protection zone.

4.5. grounding

The main task of the grounding lightning protection device is to divert as much of the lightning current as possible (50% or more) to the ground. The rest of the current flows through the communications suitable for the building (cable sheaths, water supply pipes, etc.). In this case, dangerous voltages do not arise on the ground electrode itself. This task is performed by a grid system under and around the building. The ground conductors form a mesh loop that connects the concrete reinforcement at the bottom of the foundation. This is a common method of creating an electromagnetic shield at the bottom of a building. The ring conductor around the building and/or in the concrete at the periphery of the foundation is connected to the earthing system by earth conductors, usually every 5 m. An external earth conductor may be connected to said ring conductors.

The concrete reinforcement at the bottom of the foundation is connected to the grounding system. The reinforcement must form a grid connected to the earth system, usually every 5 m.

It is possible to use a galvanized steel mesh with a mesh width of typically 5 m, welded or mechanically attached to the reinforcement bars, usually every 1 m. On fig. Figures 4.7 and 4.8 show examples of a mesh grounding device.

The connection of the grounding conductor and the connection system creates a grounding system. The main task of the grounding system is to reduce the potential difference between any points of the building and equipment. This problem is solved by creating a large number of parallel paths for lightning currents and induced currents, forming a network with low resistance in a wide frequency spectrum. Multiple and parallel paths have different resonant frequencies. Multiple loops with frequency-dependent impedances create a single low-impedance network for interference in the spectrum under consideration.

4.6. Surge protection devices

Surge protection devices (SPD) are installed at the intersection of the power supply, control, communication, telecommunications line of the border of two shielding zones. SPDs are coordinated to achieve an acceptable load distribution between them in accordance with their resistance to destruction, as well as to reduce the likelihood of destruction of the protected equipment under the influence of lightning current (Fig. 4.9).

Rice. 4.9. An example of installing an SPD in a building

It is recommended to connect the power and communication lines entering the building with one bus and place their SPDs as close to each other as possible. This is especially important in buildings made of non-shielding material (wood, brick, etc.). SPDs are selected and installed so that the lightning current is mainly diverted to the earthing system at the border of zones 0 and 1.

Since the energy of the lightning current is mainly dissipated at this boundary, subsequent SPDs only protect against the remaining energy and the effects of the electromagnetic field in zone 1. For the best protection against overvoltages, when installing an SPD, short connecting conductors, leads and cables are used.

Based on the requirements of insulation coordination in power plants and resistance to damage of the protected equipment, it is necessary to choose the SPD voltage level below the maximum value so that the impact on the protected equipment is always below the allowable voltage. If the level of resistance to damage is not known, an indicative or test level should be used. The number of SPDs in the protected system depends on the resistance of the protected equipment to damage and the characteristics of the SPDs themselves.

4.7. Protection of equipment in existing buildings

The increasing use of sophisticated electronic equipment in existing buildings requires better protection against lightning and other electromagnetic interference. It is taken into account that in existing buildings necessary measures for lightning protection is chosen taking into account the features of the building, such as structural elements, existing power and information equipment.

The need for protective measures and their choice is determined on the basis of the initial data that is collected at the stage of pre-project surveys. An approximate list of such data is given in Table. 4.3-4.6.

Table 4.3

Initial data about the building and the environment

No. p / p	Characteristic
1	Building material - masonry, brick, wood, reinforced concrete, steel frame
2	A single building or several separate blocks with big amount connections
3	Low and flat or tall building (building dimensions)
4	Are fittings connected throughout the building?
5	Is the metal lining electrically connected?
6	Window sizes
7	Is there an external lightning protection system?
8	Type and quality of external lightning protection system
9	Soil type (stone, earth)
10	Grounded elements of neighboring buildings (height, distance to them)

Table 4.4

Initial data on equipment

No. p / p	Characteristic
1	Incoming lines (underground or overhead)
2	Antennas or others external devices
3	Type of power system (high voltage or low voltage, underground or above ground)
4	Cable laying (number and location of vertical sections, cable laying method)
5	Use of metal cable trays
6	Is there electronic equipment inside the building?
7	Are there conductors going to other buildings?

Table 4.5

Equipment characteristics

Table 4.6

Other data concerning the choice of protection concept

Based on the risk analysis and the data given in Table. 4.3-4.6, a decision is made on the need to build or reconstruct a lightning protection system.

4.7.1 Protective measures when using an external lightning protection system

The main task is to find the optimal solution to improve the external lightning protection system and other measures.

Improvement of the external lightning protection system is achieved:

metal cladding

4.7.2. Protective measures when using cables

Efficient measures to reduce surges are the rational laying and shielding of cables. These measures are all the more important, the less the external lightning protection system shields.

Large loops can be avoided by running power cables and shielded communication cables together. The shield is connected to the equipment at both ends.

Any additional shielding, such as laying wires and cables in metal pipes or trays between floors, reduces the impedance of the overall connection system. These measures are most important for tall or long buildings, or when equipment must work especially reliably.

The preferred installation locations for SPDs are the boundaries of zones 0/1 and zones 0/1/2, respectively, located at the entrance to the building.

As a rule, the common network of connections is not used in the operating mode as a return conductor of the power or information circuit.

4.7.3. Protective measures when using antennas and other equipment

Examples of such equipment are various external devices such as antennas, meteorological sensors, outdoor cameras, outdoor sensors in industrial facilities (sensors for pressure, temperature, flow rate, valve position, etc.) and any other electrical, electronic and radio equipment, mounted outside on a building, mast, or industrial tank.

If possible, the lightning rod is installed in such a way that the equipment is protected from a direct lightning strike. Individual antennas are left completely open for technological reasons. Some of them have a built-in lightning protection system and can withstand a lightning strike without damage. Other, less protected types of antennas may require the installation of an SPD on the supply cable to prevent lightning current from flowing through the antenna cable into the receiver or transmitter. If there is an external lightning protection system, the antenna mounts are attached to it.

Stress induction in cables between buildings can be prevented by running them in connected metal trays or pipes. All cables leading to antenna-related equipment are laid out of the pipe at one point. You should pay maximum attention to the shielding properties of the object itself and lay cables in its tubular elements. If this is not possible, as in the case of process vessels, the cables should be laid outside, but as close to the object as possible, while making maximum use of natural screens such as metal stairs, pipes, etc. In masts with L-shaped corner elements, the cables are located inside the corner for maximum natural protection. As a last resort, an equipotential bonding conductor with a minimum cross section of 6 mm 2 should be placed next to the antenna cable. All these measures reduce the induced voltage in the loop formed by the cables and the building, and, accordingly, reduce the likelihood of a flashover between them, i.e. the likelihood of an arc inside the equipment between the mains and the building.

4.7.4. Protection measures for power cables and communication cables between buildings

Building-to-building connections fall into two main types: metal sheathed power cables, metal cables (twisted pair, waveguides, coaxial and multicore cables), and fiber optic cables. The protective measures depend on the types of cables, their number, and whether the lightning protection systems of the two buildings are connected.

Fully insulated fiber optic cable (no metal armor, moisture protection foil or steel inner conductor) can be used without additional protection measures. The use of such a cable is the best option, as it provides complete protection against electromagnetic influences. However, if the cable contains an extended metal element (with the exception of remote power wires), the latter must be connected to the general connection system at the entrance to the building and must not directly enter the optical receiver or transmitter. If buildings are located close to each other and their lightning protection systems are not connected, it is preferable to use fiber optic cable without metal elements in order to avoid high currents in these elements and overheating. If there is a cable connected to the lightning protection system, then an optical cable with metal elements can be used to divert part of the current from the first cable.

Metal cables between buildings with isolated lightning protection systems. With this connection of protection systems, damage is very likely at both ends of the cable due to the passage of lightning current through it. Therefore, an SPD should be installed at both ends of the cable, and, where possible, the lightning protection systems of the two buildings should be connected and the cable should be laid in connected metal trays.

Metal cables between buildings with connected lightning protection systems. Depending on the number of cables between buildings, protective measures may include connecting cable trays with few cables (for new cables) or with a large number of cables, as is the case with chemical production, shielding or use of flexible metal conduits for multicore control cables. Connecting both ends of a cable to associated lightning protection systems often provides sufficient shielding, especially if there are many cables and the current will be distributed between them.

1. Development of operational technical documentation

In all organizations and enterprises, regardless of the form of ownership, it is recommended to have a set of operational and technical documentation for lightning protection of objects that require a lightning protection device.

The set of operational and technical documentation of lightning protection contains:

The explanatory note states:

The explanatory note indicates the enterprise that developed the set of operational and technical documentation, the basis for its development, the list of current regulatory documents and technical documentation that guided the work on the project, special requirements for the designed device.

Initial data for lightning protection design include:

The section "Accepted methods of lightning protection of objects" describes the selected methods of protecting buildings and structures from direct contact with the lightning channel, secondary manifestations of lightning and drifts of high potentials through ground and underground metal communications.

Objects built (designed) according to the same standard or reusable project, having common building characteristics and geometric dimensions and the same lightning protection device, may have one general scheme and calculation of protection zones of lightning rods. The list of these protected objects is given on the diagram of the protection zone of one of the structures.

When checking the reliability of protection using software, data of computer calculations are given in the form of a summary of design options and a conclusion is made about their effectiveness.

When developing technical documentation, it is proposed to use as much as possible standard designs of lightning rods and grounding conductors and standard working drawings for lightning protection. If it is impossible to use standard designs of lightning protection devices, working drawings of individual elements can be developed: foundations, supports, lightning rods, down conductors, ground electrodes.

To reduce the volume of technical documentation and reduce the cost of construction, it is recommended to combine lightning protection projects with working drawings for general construction works and installation of plumbing and electrical equipment in order to use plumbing communications and grounding switches for electrical devices for lightning protection.

2. Procedure for acceptance of lightning protection devices into operation

Lightning protection devices of objects completed by construction (reconstruction) are accepted into operation by the working commission and transferred to operation to the customer before installation technological equipment, delivery and loading of equipment and valuable property into buildings and structures.

Acceptance of lightning protection devices at operating facilities is carried out by the working commission.

The composition of the working commission is determined by the customer. The working committee usually includes representatives of:

The working committee is presented with the following documents:

The working commission makes a full check and inspection of the completed construction and installation works for the installation of lightning protection devices.

Acceptance of lightning protection devices of newly constructed facilities is documented by acts of acceptance of equipment for lightning protection devices. Putting lightning protection devices into operation is formalized, as a rule, by acts-permits of the relevant bodies of state control and supervision.

After acceptance into operation of lightning protection devices, passports of lightning protection devices and passports of grounding devices of lightning protection devices are drawn up, which are kept by the person responsible for electrical facilities.

The acts approved by the head of the organization, together with the submitted acts for hidden work and measurement protocols, are included in the passport of lightning protection devices.

3. Operation of lightning protection devices

Lightning protection devices for buildings, structures and outdoor installations of objects are operated in accordance with the Rules for the technical operation of consumer electrical installations and the instructions of this Instruction. The task of operating lightning protection devices of objects is to maintain them in a state of necessary serviceability and reliability.

To ensure the constant reliability of the operation of lightning protection devices, every year before the start of the thunderstorm season, all lightning protection devices are checked and inspected.

Checks are also carried out after the installation of the lightning protection system, after making any changes to the lightning protection system, after any damage to the protected object. Each check is carried out in accordance with the work program.

To check the status of the MLT, the reason for the check is indicated and the following are organized:

functional duties

During the inspection and testing of lightning protection devices, it is recommended:

check by visual inspection (using binoculars) the integrity of lightning rods and down conductors, the reliability of their connection and fastening to the masts;
identify elements of lightning protection devices that require replacement or repair due to a violation of their mechanical strength;
determine the degree of destruction by corrosion of individual elements of lightning protection devices, take measures for anti-corrosion protection and strengthening of elements damaged by corrosion;
check the reliability of electrical connections between the current-carrying parts of all elements of lightning protection devices;
check the compliance of lightning protection devices with the purpose of the objects and, in case of construction or technological changes for the previous period, outline measures for the modernization and reconstruction of lightning protection in accordance with the requirements of this Instruction;
clarify the executive circuit of lightning protection devices and determine the ways of spreading the lightning current through its elements during a lightning discharge by simulating a lightning discharge into a lightning rod using a specialized measuring complex connected between the lightning rod and a remote current electrode;
measure the value of the resistance to the spreading of the pulsed current using the "ammeter-voltmeter" method using a specialized measuring complex;
measure the values of surge voltages in power supply networks during a lightning strike, potential distribution over metal structures and the grounding system of a building by simulating a lightning strike into a lightning rod using a specialized measuring complex;

measurement of resistance of conductors of connection to the ground and equalization of potentials (metal bond) (2p);
measuring the resistance of grounding devices using a three-pole circuit (3p);
measuring the resistance of grounding devices using a four-pole circuit (4p);
resistance measurement of multiple grounding devices without breaking the grounding circuit (using current clamps);
measuring the resistance of grounding devices using the two-clamp method;
measurement of the resistance of lightning protection (lightning rods) according to the four-pole circuit by the pulse method;
measurement of alternating current (leakage current);
measurement of soil resistivity by the Wenner method with the possibility of choosing the distance between the measuring electrodes;
high noise immunity;
saving measurement results in memory;
connecting the meter to a computer (USB);
compatibility with the SONEL Protocols program;

measure the value of electromagnetic fields in the vicinity of the location of the lightning protection device by simulating a lightning strike into a lightning rod using special antennas;
check the availability of the necessary documentation for lightning protection devices.

Periodic control with opening for six years (for objects of category I) is subject to all artificial grounding conductors, down conductors and their connection points; at the same time, up to 20% of their total number is checked annually. Corroded earth electrodes and down conductors with a decrease in their area cross section more than 25% must be replaced with new ones.

Extraordinary inspections of lightning protection devices should be carried out after natural disasters ( hurricane wind, flood, earthquake, fire) and thunderstorms of extreme intensity.

Unscheduled measurements of the grounding resistance of lightning protection devices should be carried out after repair work both on lightning protection devices, and on the protected objects themselves and near them.

The results of the checks are documented in acts, entered in the passports and the register of the state of lightning protection devices.

Based on the data obtained, a plan is drawn up for the repair and elimination of defects in lightning protection devices detected during inspections and inspections.

Earthworks at the protected buildings and structures of objects, lightning protection devices, as well as near them are carried out, as a rule, with the permission of the operating organization, which allocates responsible persons who monitor the safety of lightning protection devices.

During a thunderstorm, work on lightning protection devices and near them is not performed.

Lightning protection and grounding - important elements private house. After all, protection from lightning allows not only to prevent the loss of property, but also preserves the life and health of the inhabitants of the home.

The nature of lightning

Clouds are a bunch of droplets of water and water vapor that are in the sky. The large sizes of clouds determine their location in different temperature zones. Therefore, temperatures in different layers of clouds can vary by 20-30 degrees. For example, while in bottom layer cloud temperature can be -10 ° C, in top layer it can be below -40 °C. This turns the water and steam into very small pieces of ice. Due to the contacts between the crystals, static electricity is generated. Since the temperatures in different layers of the cloud differ, the electric charges are also not the same, and therefore the cloud resembles a layer cake.

The current accumulated by the clouds is enormous. However, electricity is sooner or later thrown out in the form of lightning, which, in fact, are short circuits between conductors of different polarity.

Lightning is accompanied by a roar, that is, thunder. Rolling thunder occurs as a result of the instantaneous penetration of an incandescent bolt of lightning through masses of air.

There are three types of lightning:

directed towards the upper atmospheric layers;
discharged inside layers with different charges - in one cloud or between neighboring clouds;
directed towards the earth's surface.

Since electricity always takes the shortest path, lightning strikes the highest part of buildings and trees. The latter are natural lightning rods.

What is a lightning rod

Lightning rod - a device through which electricity is diverted to the ground, bypassing the protected object. The lightning rod is always located above the level of the protected object. A lightning protection device is an electrical conductor and, as it were, provokes lightning to strike exactly at it. Thus, a short circuit between the cloud and the earth's surface does not occur in an unexpected place, but exactly where it will be neutralized by lightning protection.

There are two types of lightning protection devices:

Single lightning rods.
Rope lightning rods, which are several cables stretched between individual lightning rods. This method of protection against lightning is typical, first of all, for high-voltage power lines. In everyday life, such systems are used to protect large areas, where the cable is pulled along the perimeter of the site, or to protect extended buildings.

Lightning protection components

Lightning protection includes:

lightning rod, which is a thin electrode with a sharp tip (mounted above the protected building);
current-carrying cable, through which the current is diverted to ground;
grounding system.

Lightning rod

This part, as mentioned above, is designed to receive a lightning discharge. The optimal material for the manufacture of a lightning rod (as well as a ground electrode) is copper.

Note! It is not allowed to cover the lightning rod with paintwork materials, because in this case the device will not be able to perform its function.

To organize lightning protection on the roof of a building, you can install small lightning rods on different sides of the roof and in the center, from half a meter to a meter long. After that, they need to be combined into a single system and connected to the ground electrode.

Also, a lightning rod can be installed on the roof of a wooden building, on a chimney or a nearby tree. The device is placed on a wooden mast. If the house has a metal roof covering, direct grounding of the roof may be sufficient.

Note! The higher the pantograph is located, the larger the protected area. However, this rule applies up to approximately 15 meters in height. At higher altitudes, the efficiency of the device decreases.

Down conductor

To create a down conductor, you will need a copper or aluminum cable of the largest possible cross section. The optimal solution would be a conventional twisted aluminum wire used in the installation of overhead power lines. At one end, the wire is attached to the lightning rod using couplings, crimp pipes or terminals, and at the other end - to the ground electrode. The wire must be placed strictly vertically in order to use the minimum distance between the ground electrode and the lightning rod. The drain cable can be insulated or laid through a specially created channel.

Grounding a private house

Proper grounding is the basis for effective lightning protection of a building. There is a widespread opinion that a steel bar connected with a wire to a lightning rod and inserted into the ground is sufficient for arranging grounding. This judgment is incorrect and lightning protection made in this way will not protect against the strikes of the elements.

Instructions for the installation of grounding networks and lightning protection require strict adherence to a number of recommendations. The installation of grounding conductors is carried out according to the same principle as the grounding loop of a building. The best materials for the purpose of lightning protection - aluminum, brass, copper and other stainless metals. However, these materials are quite expensive, so steel can also be used. According to the technical regulations (SNIP) for operation electrical installations and conductive parts, grounding conductors must be tested annually for mechanical damage and corrosion. If the diameter of the system elements has been reduced by more than half, their mandatory replacement is necessary.

You will also need not one, but several metal rods stuck into the ground. At the same time, although the number of rods is a calculated value, it is generally accepted that for a one-story or two-story house 3-4 rods are enough. The length of the rods should exceed by approximately 30 centimeters the depth of maximum freezing of the soil.

The rods are joined by an electrical conductor, usually a wire made of aluminum, copper, or a tinned steel plate. This creates a closed loop. Externally, the design will resemble the letter "Sh", dug into the ground.

Note! No tying of wire rods allowed manually or pliers. This cannot be done even in household grounding, and even more so in a lightning protection system.

Connections must be created by welding, using crimp sleeves or hard twisting, that is, by cold welding of parts. Such connections are reliable, they are not subject to backlash and do not weaken over time. The assembled structure will look something like this.

Important! Grounding for a lightning rod is necessary with a loop. To do this, the lightning protection loop is connected to the ground loop of the building.

The contours are joined with a steel strip. As a result of the work performed, the overall contour is enhanced, which has a positive effect on the safety of the building.

Ground electrode location

Both the down conductor and the grounding conductor must be located in a place where children and pets cannot access. Any grounding conductor can be large object made of metal, while the larger its area of contact with the surface, the more effective it is. How ground electrodes can be used mesh of rebar, cast iron bath, bed steel parts, etc.

Water is an excellent conductor of electricity. Based on this, the ground electrode must be installed where the ground is wet. It is possible to artificially moisten the grounding area, for example, by directing water flow from the roof of the building there.

Note! In houses with plumbing and a centralized heating system, as well as in buildings connected to underground electrical networks, grounding is already available. Therefore, such objects do not need to install additional lightning rods.

Protective zone of the lightning rod

To calculate the guard zone, you can use the rule that this zone is close to a cone-like shape with a 45-degree angle at the top. If we are talking about a single wire lightning rod, the protection zone is similar to a prism with three faces, where the wire acts as an edge. The probability of a direct lightning strike in such areas is no more than 1%. Thus, if the lightning rod is located, for example, at a height of 10 meters, the protective zone on the ground will also have a 10-meter diameter.

There is another way to calculate the guard zone. Here the formula R = 1.732 h is applied, where R is the diameter of the protective zone above the highest point of the building, h is the height from the highest point of the building to the peak of the lightning rod.

Protection zone calculation

Thus, if the height of the house is 7 meters, and the upper end of the lightning rod is 3 meters above the highest point of the roof, the diameter of the protective zone will be 5 meters 20 centimeters. The result is a cone with a diameter at the base - 9 meters and a 10-meter height.

Acceptance of lightning protection systems in operation

Lightning protection devices for construction sites are accepted by a special commission and put into operation by the owner of the building before installation of valuable property in the premises. The composition of the commission for acceptance is established by the customer of the object. The acceptance committee consists of specialists from the following areas:

electrical economy;
contractor;
fire inspection;

The acceptance committee is provided with the following documentation:

approved projects for the creation of lightning protection;
acts for the performance of hidden work (installation of down conductors and grounding conductors that are not accessible for visual control);
certificates of testing lightning protection devices against secondary effects of lightning and the ingress of high potentials through metal communications (information on grounding resistance for lightning protection, results of monitoring the installation of devices).

The commission for acceptance checks the performed installation work on the arrangement of lightning protection systems.

Acceptance of lightning protection devices in new buildings is carried out using equipment acceptance certificates. The start of lightning protection devices is carried out after the signing of the certificates of approval of the relevant supervisory and regulatory authorities of the state.

Upon completion of acceptance, passports are issued for lightning protection systems and passports for grounding conductors, which are held by the owner of the building or responsible for the electrical economy.

Natural lightning rods

Different trees cope with the function of lightning removal in different ways. The most suitable trees are birch, spruce and pine. However, in settlements, birch is more applicable for the purposes of lightning protection, but conifers are tried not to be planted in the immediate vicinity of buildings, since their wood is more fragile.

The listed tree species have advantages over some other species due to their root system. Trees with the most branched root system, located shallow in the ground, have the best grounding. It is best if the roots of such trees are partially located on the surface of the soil and fan out to the sides. When it hits a tree, the electric charge instantly reaches the root system and goes into the ground.

Important! Trees should be avoided during thunderstorms as the chances of being struck by lightning are greatly increased.

Creating a lightning protection device is not very complex, but requires a basic understanding of physical laws and compliance with technical regulations. If there is no self-confidence, it is better to seek help from specialists.

Introduction - about the role of grounding in a private house

The house has just been built or bought - in front of you is exactly the cherished home that you recently saw on a sketch or photograph in an ad. Or maybe you have been living in your own house for more than a year, and every corner in it has become familiar. Owning your own personal home is great, but along with the feeling of freedom, in addition you get a number of responsibilities. And now we will not talk about household chores, we will talk about such a need as grounding for a private house. Any private house includes the following systems: electrical network, water supply and sewerage, gas or electric heating system. Additionally, a security and alarm system, ventilation, a smart home system, etc. are installed. Thanks to these elements, a private house becomes a comfortable living environment for a modern person. But it really comes to life thanks to the electrical energy that powers the equipment of all the above systems.

The need for grounding

Unfortunately, electricity also has a downside. All equipment has a service life, each device has a certain reliability, so they will not work forever. In addition, when designing or installing the house itself, electricians, communications or equipment, mistakes can also be made that can affect electrical safety. For these reasons, part of the electrical network may be damaged. The nature of accidents is different: short circuits can occur, which are turned off by automatic switches, or breakdowns to the case can occur. The difficulty is that the breakdown problem is hidden. There was damage to the wiring, so the body of the electric stove was energized. With improper grounding measures, damage will not manifest itself in any way until a person touches the stove and receives an electric shock. An electric shock will happen due to the fact that the current is looking for a path to the ground, and the only suitable conductor will be the human body. This cannot be allowed.

First, let's look at the most progressive approach to electrical power at home - the TN-S system. In this system, PE and N conductors are separated throughout, and the consumer does not need to install grounding. It is only necessary to bring the PE conductor to the main ground bus, and then separate the ground conductors from it to electrical appliances. Such a system is implemented both as a cable and overhead line, in the case of the latter, a VLI (isolated overhead line) is laid using self-supporting wires (SIP).

But such happiness does not fall to everyone because the old overhead transmission lines use the old grounding system - TN-C. What is its feature? In this case, PE and N are laid along the entire length of the line by one conductor, in which the functions of both the zero protective and zero working conductors are combined - the so-called PEN conductor. If earlier it was allowed to use such a system, then with the introduction in 2002 of the PUE 7th edition, namely clause 1.7.80, the use of RCDs in the TN-C system was banned. Without the use of RCDs, there can be no talk of any electrical safety. It is the RCD that turns off the power when the insulation is damaged, as soon as it occurs, and not at the moment when a person touches the emergency device. To meet all the necessary requirements, the TN-C system must be upgraded to TN-C-S.

In the TN-C-S system, a PEN conductor is also laid along the line. But, now, paragraph 1.7.102 PUE 7th ed. says that re-grounding of the PEN conductor must be performed at the inputs of the overhead lines to electrical installations. They are performed, as a rule, at the electric pole from which the input is performed. When re-grounding, the PEN conductor is divided into separate PE and N, which are brought into the house. The re-grounding norm is contained in paragraph 1.7.103 of the PUE 7 ed. and is 30 ohms, or 10 ohms (if there is a gas boiler in the house). If the grounding at the pole is not completed, it is necessary to contact Energosbyt, in whose department the electric pole, switchboard and input to the consumer's house is located, and point out the violation that must be corrected. If the switchboard is located in the house, PEN separation must be done in this switchboard, and re-grounding should be done near the house.

In this form, TN-C-S is successfully operated, but with some reservations:

if the condition of the overhead line raises serious concerns: the old wires are not in the best condition, because of which there is a risk of breakage or burnout of the PEN conductor. This is fraught with increased voltage on the grounded housings of electrical appliances, because. the current path to the line through the working zero will be interrupted, and the current will return from the bus on which the separation was performed through the zero protective conductor to the device case;
if re-groundings are not made on the line, then there is a danger that the fault current will flow into the only re-grounding, which will also lead to an increase in the voltage on the case.

In both cases, electrical safety leaves much to be desired. The solution to these problems is the TT system.

How to make grounding at home?

For grounding, it is enough to hammer a six-meter vertical electrode.

(click to enlarge)

Such grounding turns out to be very compact, it can be installed even in the basement, no regulatory documents contradict this. The necessary steps for grounding are described for soft ground with a resistivity of 100 ohm*m. If the soil has a higher resistance, additional calculations are required, contact ZANDZ.ru technical specialists for help in calculations and selection of materials.

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Now it's time to learn how to make lightning protection for a private house. It consists of two parts: external and internal.

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Installing all these elements will protect the house from lightning, or rather from the danger posed by its direct strike.

Has external lightning protection
In this case, a classic protective cascade is installed from devices of classes 1, 2 and 3 arranged in series. SPD of class 1 is mounted on the input and limits the current of a direct lightning strike. A class 2 SPD is also installed either in the input switchboard or in the distribution switchboard, if the house is large and the distance between the switchboards is more than 10 m. It is designed to protect against induced overvoltages, it limits them to a level of 2500 V. If the house has sensitive electronics, then it is desirable to install a class 3 SPD that limits overvoltages to the level of 1500 V; most devices can withstand such a voltage. SPD of class 3 is installed directly at such devices.
No external lightning protection
A direct lightning strike into the house is not taken into account, so there is no need for a class 1 SPD. The remaining SPDs are installed in the same way as described in paragraph 1. The choice of SPD also depends on the grounding system, to be sure of the correct choice, contact ZANDZ.ru technical specialists for help.

The figure shows a house with a protective earth, an external lightning protection system and a combined SPD of class 1 + 2 + 3 installed, designed for installation in a TT system.

Comprehensive home protection: protective grounding, external lightning protection system and
combined SPD class 1+2+3, designed for installation in a TT system
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An enlarged image of a shield with an installed SPD for the house
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No. p / p	Rice	vendor code	Product	Qty
Lightning protection system
1		ZANDZ Air terminal mast vertical 4 m (stainless steel)	2
2		GALMAR Holder for lightning rod - mast ZZ-201-004 to the chimney (stainless steel)	2
3		GALMAR Clamp to lightning rod - mast GL-21105G for down conductors (stainless steel)	2
4		GALMAR Copper-plated steel wire (D8 mm; coil 50 meters)	1
5		GALMAR Copper-clad steel wire (D8 mm; coil 10 meters)	1
6		GALMAR Downpipe clamp for down conductor (tin-plated copper + tin-plated brass)	18
7		GALMAR Universal roof clamp for down conductor (height up to 15 mm; painted galvanized steel)	38
8		GALMAR Clamp to the facade/wall for a down conductor with an elevation (height 15 mm; galvanized steel with painting)	5
9