What is protective grounding? Protective grounding: principle of operation and circuits. Basic methods of grounding

Protective grounding- intentional connection to the ground of metal parts of equipment that are not energized under normal conditions, but which may become energized as a result of a violation of the insulation of the electrical installation.

The purpose of protective grounding is to eliminate the danger of electric shock to people when voltage appears on structural parts electrical equipment, i.e. when there is a “short circuit to the housing”.

The operating principle of protective grounding is to reduce touch and step voltages caused by a “short circuit to the body” to safe values. This is achieved by reducing the potential of grounded equipment, as well as equalizing potentials by raising the potential of the base on which a person stands to a potential close in value to the potential of grounded equipment.

The scope of application of protective grounding is three-phase three-wire networks with voltages up to 1000 V with an isolated neutral and above 1000 V with any neutral mode (Fig. 71).

Rice. 71. Schematic diagrams protective grounding:
a - in a network with an isolated neutral up to 1000 V and above; b - in a network with a grounded neutral above 1000 V, 1 - grounded equipment; 2 — protective grounding conductor; 3 - working grounding conductor; r3. rо - resistance of protective and working grounding, respectively

Types of grounding devices. A grounding device is a combination of a grounding conductor - metal conductors in direct contact with the ground, and grounding conductors connecting the grounded parts of the electrical installation to the grounding conductor. There are two types of grounding devices: remote (or concentrated) and loop (or distributed).

A remote grounding device is characterized by the fact that its grounding conductor is located outside the site on which the grounded equipment is located, or is concentrated on some part of this site.

The disadvantage of remote grounding is the distance of the ground electrode from the protected equipment, as a result of which the contact coefficient a = 1. Therefore, this type of grounding is used only for low ground fault currents and, in particular, in installations with voltages up to 1000 V, where the potential of the ground electrode does not exceed the permissible touch voltage .

The advantage of this type of grounding device is the ability to choose the location of the electrodes with the lowest soil resistance (damp, clayey, in lowlands, etc.).

A loop grounding device is characterized by the fact that its single grounding conductors are placed along the contour (perimeter) of the site on which the grounded equipment is located, or are distributed throughout the entire site as evenly as possible.

Safety during loop grounding is ensured by equalizing the potential in the protected area to such a value that the maximum values ​​of touch and step voltages do not exceed permissible values. This is achieved by appropriate placement of single ground electrodes.

Indoors, potential equalization occurs naturally through metal constructions, pipelines, cables and similar conductive objects connected to an extensive grounding network.

Implementation of grounding devices. There are artificial grounding electrodes, intended exclusively for grounding purposes, and natural ones - metal objects located in the ground for other purposes.

For artificial grounding electrodes, vertical and horizontal electrodes are usually used.

Steel pipes with a diameter of 3-5 cm and angle steel measuring from 40 X 40 to 60 X 60 mm and a length of 2.5-3 m are used as vertical electrodes. last years Steel rods with a diameter of 10-12 mm and a length of up to 10 m are used.

To connect the vertical electrodes and as an independent horizontal electrode, use strip steel with a cross section of at least 4 X 12 mm or steel round section with a diameter of at least 6 mm.

To install vertical grounding conductors, first dig a trench 0.7-0.8 m deep, after which pipes or corners are driven in using mechanisms.

The following can be used as natural grounding conductors: water supply and other metal pipelines laid in the ground, with the exception of pipelines of flammable liquids, flammable or explosive gases, as well as pipelines coated with insulation to protect against corrosion; casing artesian wells, wells, pits, etc.; metal structures and fittings reinforced concrete structures buildings and structures connected to the ground; lead sheaths of cables laid in the ground. Natural grounding conductors, as a rule, have low resistance to current flow and therefore their use for grounding purposes gives very tangible savings. The disadvantages of natural grounding electrodes are their accessibility to non-electrical personnel and the possibility of disrupting the continuity of the connection of extended grounding electrodes (if repair work and so on.).

As a rule, strip steel is used as grounding conductors intended for connecting grounding parts with grounding conductors, as well as round steel etc. Grounding conductors are laid openly along building structures, including walls on special supports. Grounding conductors in premises must be accessible for inspection.

The connection of the grounded equipment to the grounding main is carried out using separate conductors. In this case, sequential connection of grounded equipment is not allowed.

According to the requirements of the Electrical Installation Rules, the protective grounding resistance at any time of the year should not exceed:

4 Ohms - in installations with voltages up to 1000 V; if the power of the current source (generator or transformer) is less than 100 kVA, then the grounding resistance is allowed 10 Ohms;

0.5 Ohm - in installations with voltages above 1000 V with high ground fault currents (more than 500 A);

250/I3, but not more than 10 Ohms - in installations with voltages above 1000 V with low ground fault currents and without capacitive current compensation; if the grounding device is simultaneously used for electrical installations with voltages up to 1000 V, then the grounding resistance should not exceed 125/I3, but not more than 10 Ohms (or 4 Ohms, if required for installations up to 1000 V). Here I3 is the ground fault current.

Equipment to be grounded. Metal non-current-carrying parts of electrical equipment are subject to protective grounding, which, due to faulty insulation, may be energized and which can be touched by people and animals. At the same time, in rooms with increased danger or especially dangerous grounding is mandatory when rated voltage electrical installations above 36 V AC and 110 V direct current, and in rooms without increased danger- at a voltage of 500 V and above. Only in explosive areas is grounding carried out regardless of the voltage level.

Electricity - best friend And worst enemy person. Of course, now it’s almost impossible to imagine life without him. Unfortunately, there were some bad moments, such as electric shock. You may get an electric shock if you touch not only an exposed live part, but also the seemingly harmless body of an electrical appliance. In this article we will try to explain in simple language What is grounding and what is it intended for? In addition, we will look at what a difavtomat and RCD are and what they are used for.

Definition of the concept

To put it briefly and in simple words, That:

Grounding is a device that protects a person from electric shock if all electrical equipment is connected to ground. IN emergency situation dangerous voltage “drains” to the ground.

Protection is the main purpose of grounding. It consists of connecting an additional, third grounding conductor to the wiring, which is connected to a device such as a ground electrode. He, in turn, has good contact with the ground.

Grounding can be operational or protective according to its intended purpose. The working one is needed for the normal functioning of the electrical installation, the protective one is needed to ensure electrical safety (preventing electric shock).

Typically, grounding (ground electrode) looks like three electrical rods driven into the ground, at equal distances from each other, located in the corners of an equilateral triangle. These rods are connected to each other by a metal strip. You might have seen such rods near houses and buildings.

You may also have noticed that on the walls of many buildings, inside or outside, metal strips are fixed, sometimes painted with yellow and green alternating stripes - this is also connected to the ground electrode. A grounding bus is needed so as not to pull a grounding wire from each electrical installation.

The third conductor is usually connected to the body electrical appliances, providing protection against the appearance of dangerous voltage. In cables, it usually has a smaller cross-section than the adjacent “working” conductors and a different insulation color – yellow-green.

Grounding Requirements

The requirements for the protective ground loop are as follows:

1. All electrical installations must be grounded, including metal doors of electrical cabinets and switchboards.
2. The resistance of the grounding device should not exceed 4 Ohms in electrical installations with a grounding neutral.
3. Nessesary to use .

We have figured out what grounding is, now let’s talk about why it is needed.

Why does a person get electrocuted?

Let's consider two typical situations when you are shocked:

1. The washing machine was doing its job properly, and when you wanted to turn it off, you felt that its body was “pinching” you. Or even worse, when you touched it, you got a serious jolt.
2. You decided to take a bath, turned on the water, grabbed the tap, you felt the same effect of electricity - a tingling or swipe.

Both situations can be solved by connecting grounding to the housings of devices and all metal parts in the bathroom and installing an RCD or differential machine on supplying electricity to a home or a group of consumers.

How does grounding work?

First, let's figure out why on the case washing machine or other electrical equipment, dangerous voltage has appeared. Everything is quite simple - the insulation of the conductors for some reason has deteriorated or become damaged and the damaged area touches metal case some piece of equipment.

If there is no grounding or neutralization of electrical equipment, then when a person touches a damaged device, a potential difference on the surface between the points of contact may occur. When standing near damaged equipment, a (potential difference between feet touching the ground) may occur. Touch voltage and step voltage can be dangerous to humans. To reduce their value to a safe value, protective grounding is used.

Even such small values ​​as 50 mA are dangerous for humans - such a current can lead to ventricular fibrillation and death.

So, the principle of grounding is as follows: the housings of all electrical appliances are connected to the ground electrode, and an RCD is additionally installed. If a dangerous voltage occurs on the frame, the ground always attracts the dangerous potential to the safe ground potential and the voltage “drains” to the ground.

What are RCDs and difavtomats used for?

Simple grounding of devices is good, but it is even better to provide additional protection. For this they came up with (RCD) and.

A difavtomat is a device that combines an RCD and a conventional one in its housing. circuit breaker, so you will save space in the electrical panel.

RCD - reacts only to . The principle of its operation is this: it compares the amount of current through the phase and through the neutral wire; if part of the current has flowed to the ground, then it instantly reacts by turning off the circuit. They are distinguished by sensitivity from 10 to 500 mA. The more sensitive the RCD, the more often it will trigger, even with minor leaks, but you should not install an RCD that is too rough for your home.

The principle of operation of a protected circuit in simple terms:

When a phase hits the housing of grounded electrical equipment, current begins to flow between the phase wire and the housing. Then the RCD notices that current has passed through the phase wire, some of the current must be sent somewhere and along neutral wire a smaller current returns, after which this circuit is de-energized. This way you are protected from electric shock.

If you install an RCD in a two-wire electrical circuit without a grounding conductor and there is a possibility of current leakage somewhere, it will only work after you touch this place and the current flows to the ground through you. In this case, you will also be safe.

That's all we wanted to tell you about this issue. Now you know what grounding is, when and how it is installed and what it is used for. We hope the information was presented clearly and accessible to you!

13.07.2018

What is grounding in simple words and why is it needed?

Some manufacturers write in the operating manual for their equipment that in order to operate the equipment it is necessary to ground it.

Grounding installation is also required when building a house. What is grounding, why is it needed, and is it possible to do without it, read below.

What is grounding

Grounding is a method of transferring electrical or electrostatic charge to the ground or into a special charge-nullifying device. In most houses and apartments, electrical wiring is single-phase (alternating current), that is, it consists of a positive and negative charge.

This means that during a power surge it will change direction. As a result, the charge will transfer to the equipment and not leave the system. You will get an electric shock if you touch any electrical appliance connected to the network. At the same time, there is a high probability of failure of all equipment in the house connected to the electrical network.

Essentially, a ground is a metal plate or wire that is used to drain “extra” electricity away from your home to a place where it won’t harm anyone. Grounding conductors also include lightning rods.

Unlike simple grounding, the lightning rod must be installed on high towers and poles, since such objects experience a very strong electrostatic effect, which makes them very attractive to lightning.

How to make grounding yourself

Grounding must be done during the construction phase. This mandatory rule is written in GOSTs and SNiP and PUE. Typically, the grounding function is performed by the iron frame of reinforced concrete blocks. But if other materials are used when constructing the foundation, then grounding will have to be done separately. To do this, dig a trench from the place where the shield is installed.

A wire or metal plate of thickness is laid in the trench not less than 6 mm. Then thick reinforcing rods, 1-1.5 meters high, are driven into the trench at a distance of 80-70 cm from each other. They are connected to each other by plates that are either screwed or welded to them.

Plates and switchboard ok secured with copper wire. The rods should protrude 10-15 cm from the ground. The plate is connected to the busbar on the distribution panel using copper cable and bolts.

The straight design can be used, but it has one drawback. In case of breakdown electrical system at home, the pins will be under high voltage and if you touch them, there will be a strong electric shock. Therefore, a triangular type of grounding with a tap is most often used. It allows you to take the ground electrode to another place and protect it.

Triangle welded from plates welded to thick reinforcing bars and a discharge plate, which is placed in a trench dug in advance for this purpose. The outlet plate is connected to the distribution panel in the same way as with a direct ground electrode. There are other grounding schemes, but they are not much different from the previous two.

What happens if you don't ground?

Grounding work requires considerable physical effort and time. The question naturally arises, why so much effort? What are the consequences if you do not carry out grounding work, how dangerous is it to strain yourself like that?

Many people do not ground their homes or apartments for one simple reason. Breakdowns in electrical wiring are a rare occurrence. Even if it happened, for the current to flow strongly, the breakdown must be very large. And so, a slight tingling electric current has never killed anyone, especially if a person does not come into contact directly or through a conductor with the ground, then electricity also not felt.

Also, the risk of failure of household electrical appliances is not so great.

By by and large, grounding is more likely requirement technical standard , not necessity. In many old houses there is simply no grounding, and no one has ever been electrocuted in such houses. The grounding requirement is most often a requirement of manufacturers of household electrical appliances, especially those made of metal rather than plastic.

How to determine whether there is grounding in a house

If it is not possible to visually determine whether there is grounding in a house or apartment, that is, neither the connection to the grounding system nor the grounding pins are visible anywhere, then you can check it in several ways.

The first one is use special equipment . However, you need to know how to use it, and besides, it costs a lot of money. But there is another way to check whether there is grounding in the house, but it only works if there is a breakdown in the system, which is very important.

It is done like this: take the phone in one hand, make sure it works. And you put the other one on heating battery or any other metal object. The main thing is that you stand barefoot on the floor. If you feel light tingling from electricity- this means there is no grounding in the house.

We will send the material to you by e-mail

Every day at home and at work we have to deal with electricity, which makes human life more comfortable. But, despite the benefits that the use of electricity gives us, it still poses a certain danger, for example, electric shock. To avoid this, electrical safety requirements have been developed and special protection measures are being taken. Such measures include grounding and grounding. What is the difference between them and whether there is one, we will figure it out in this article.

All work related to electricity should only be carried out by specialists

The main requirement for household electrical appliances- safety. This applies to a greater extent to devices that come into contact with water, because even a minor defect in the equipment can be fatal to the user. To protect yourself and others, it is necessary to keep the electrical network and equipment in good condition and regularly inspect them.To eliminate the possibility of a fire due to faulty wiring and electric shock, it is necessary to install protective devices (RCD).

In accordance with the basic electrical safety rules:

It's just short list electrical safety requirements. More detailed safety rules can be found in various regulations and special literature on electricity, which are now easy to find on the Internet.

What is grounding, principle of operation and device

When creating an electrical network in premises for various purposes, it is necessary to create protection that will prevent possible electric shock. To avoid this, a grounding device is installed. In accordance with the PEU clause 1.7.53, grounding is carried out in electrical equipment with a voltage of more than 50 V AC and 120 V DC.

Grounding is the intentional connection of non-current-carrying metal parts of electrical installations (which may be live) with the ground or its equivalent. This protective measure is intended to eliminate the possibility of electric shock to a person due to a short circuit to the equipment body.

Operating principle

The operating principle of protective grounding is:

• reducing the potential difference between the grounded element and other conductive objects with natural grounding to a safe value;
• current drainage in case of direct contact of the grounded equipment with the phase wire. In a well-designed electrical network, the occurrence of a leakage current causes an instantaneous operation of the device protective shutdown(RCD).

From the above it follows that grounding is more effective when used in conjunction with an RCD.

Grounding device

The design of the grounding system consists of a ground electrode (the conductive part that has direct contact with the ground) and a conductor that provides contact between the ground electrode and non-current-carrying elements of electrical equipment. Usually a steel or copper (very rarely) rod is used as a grounding conductor; in industry this is usually a complex system, consisting of several elements of a special shape.

The effectiveness of the grounding system is largely determined by the resistance value of the protective device, which can be reduced by increasing usable area grounding conductors or increasing the conductivity of the medium, for which several rods are used, the level of salts in the ground increases, etc.

The grounding device is...

Above we discussed in general outline What is protective grounding? However, it is worth mentioning that the grounding conductors used in the system differ in natural and artificial.

As grounding devices, it is primarily preferable to use such natural grounding devices as:

Important! It is prohibited to use pipelines with gas and flammable liquids, as well as heating mains as a grounding element.

Natural grounding conductors must be connected to protective system from two or more different points.

The following can be used as an artificial grounding device:

• steel pipe with a wall thickness of 3.5 mm and a diameter of 30÷50 mm and a length of about 2÷3 m;
• steel strips and corners with a thickness of 4 mm;
• steel rods up to 10 or more meters long and with a diameter of 10 mm.

For aggressive soils, it is necessary to use artificial grounding conductors with high corrosion resistance and made of copper, galvanized or copper-plated metal.So, we have figured out what is the definition of the concept of artificial and natural grounding, now we will look at when grounding is used.

This video clearly explains what protective grounding is:

When and where is grounding applied?

As already mentioned, protective grounding is intended to eliminate the possibility of electric shock to people in the event of voltage being applied to conductive parts of the equipment, that is, in the event of a short circuit to the housing.Protective grounding is used to equip metal non-current-carrying elements of electrical installations, which, due to a possible breakdown of wire insulation, may become energized and cause harm to the health and life of people and animals if they come into direct contact with faulty equipment.

Electrical networks and equipment with voltages up to 1000 V are subject to grounding, namely:

• alternating current;
• three-phase with isolated neutral;
• two-phase, isolated from ground;
• direct current;
• current sources with an isolated winding point.

Grounding is also necessary for electrical networks and electrical installations of direct and alternating current with voltages over 1000 V with any neutral or midpoint of the current source winding.

Basic methods of grounding

When constructing a grounding system, vertical metal rods are usually used as a grounding conductor. This is due to the fact that horizontal electrodes, due to their shallow depth, have an increased electrical resistance. Steel pipes, rods, angles and other rolled metal products with a length exceeding 1 meter and having a relatively small cross-section are almost always used as vertical electrodes.

There are two main methods for installing vertical ground electrodes.

Related article:

Electricity can not only create comfortable living conditions, but also carries a certain danger. To reduce the likelihood of this hazard occurring, it is necessary DIY grounding in a private house 220V. How to make it - read the publication.

Several short electrodes

This option uses several steel angles or rods 2-3 meters long, which are connected together using a metal strip and welding. The connection is made at the surface of the earth.Installation of the ground electrode occurs by simply driving the electrode into the ground using a sledgehammer. This method is better known as “corner and sledgehammer”.

The minimum permitted cross-section of grounding electrodes is given in the PUE, but most often the corrected and supplemented values ​​are from technical circular No. 11 of RusElectroMontazh. In particular:

The advantages of this method are simplicity, low cost and availability of materials and installation.

Single electrode

IN in this case an electrode in the form of steel pipe(usually single), which is placed in deep hole, drilled in the ground. Drilling the soil and installing the electrode requires the use of special equipment.

An increase in the contact area of ​​the ground electrode with the ground is ensured by a greater depth of installation of the electrode. Moreover, this method is more effective compared to previous version, with the same total length of the electrodes, due to reaching deep layers of soil, which usually have low electrical resistivity.

To the advantages this method include high efficiency, compactness and seasonal “independence”, i.e. Due to winter freezing of the soil, the resistivity of the ground electrode practically does not change.

Another way is to lay a grounding conductor in a trench. However, this option requires large physical and material costs ( large quantity material, digging a trench, etc.).

Having figured out how grounding works and why it is needed, we now face the second question of our article, namely, what constitutes grounding, why it is needed and how it differs from grounding.

What is zeroing

The term grounding refers to the intentional connection of open non-current-carrying conductive parts of the electrical network and equipment with a solidly grounded point in single- and three-phase DC and AC networks. Grounding is performed for electrical safety purposes and is the main protective agent from getting under voltage.

Operating principle

A short circuit in the electrical network occurs when an energized phase wire comes into contact with the body of the device connected to zero. The current increases sharply, and protective devices are activated, cutting off power from the faulty equipment. According to the rules, the response time of the RCD to disconnect a faulty electrical network should not exceed 0.4 seconds. To do this, it is necessary that the phase and zero have an insignificant resistance value.

Related article:

Have you ever heard the acronym, you will find out by reading the review to the end. Briefly, I would like to add that this device can protect housing and all its inhabitants from emergency situations related to electricity.

To create a zero in single-phase network, as a rule, use the third (unused) wire of a three-core cable. To create good protection, it is necessary to ensure a high-quality connection of all elements of the grounding system.

Device

Zeroing system, for example, in apartment building, starts with grounded power transformer, from which the neutral with a three-phase line comes to the main distribution board (MSB) of the building. What happens next. A working zero is created from the neutral, which, together with the phase wire, forms the usual single-phase voltage.

The grounding itself to protect the electrical network and equipment is created in the panel using a conductor connected to a grounded neutral. You should know that it is forbidden to install switching devices (automatic machines, packets, switches, etc.) between zero and neutral.

Where is the zeroing scheme used?

According to the requirements of the PES, the following must be equipped with protective grounding:

• single- and three-phase AC networks with a grounded terminal and voltage up to 1,000 V;
• DC power networks with a central grounding point and voltage up to 1,000 V.

Grounding cannot protect against electric shock like grounding. This protective circuit simply cuts off the voltage supply in case short circuit and turns off the local power grid.

Is it possible to ground in an apartment using grounding?

We already know what grounding and grounding are, and we’ll try to find out whether it’s possible to do grounding using a grounded zero located in the electrical panel. The fact is that many people far from electrical engineering ask this question and often make unforgivable mistakes by doing just that.

Firstly, this is prohibited by PEU. The point is that if, for example, when carrying out installation work, for some reason, the phase and zero are mixed up, and besides, the zeroing is brought to the working zero, then you can expect the most unpleasant situations. When electrical equipment is connected to the network, the housing will be energized and a person will be shocked by an electric shock, since the protective operation of the RCD will not occur.

To create a protective grounding in the floor electrical panel, a separate bus is allocated, connecting to a solidly grounded neutral. And it is best not to carry out this work yourself, but to entrust it to a specialist who has knowledge in electrical engineering.

The video shows how to create a grounding if it is not in the floor electrical panel:

What is the difference between grounding and grounding?

It’s worth saying right away that despite the fact that grounding and grounding are protective measures, they differ in their principle of operation and purpose.Grounding is more efficient and reliable way protection than grounding, since it allows you to quickly equalize the difference between potentials to the required value. Also, grounding has more simple design and easier to install, and to install it you just need to follow the instructions. In addition, this protective circuit does not depend on the phase pattern of the connected equipment. Grounding options are varied, and this allows you to choose a specific type for each specific case

Protective grounding is a protective measure that, in the event of a network malfunction, simply ensures an instantaneous interruption of the supply of voltage from the electrical network by triggering an RCD. Creating grounding and connecting equipment requires experience and certain knowledge in electrical engineering. All installation work, especially determining the zero point, must be performed correctly, otherwise, in an emergency, electric shock may occur.

Having figured out what grounding and grounding are, many people prefer to use both methods. However, grounding is mandatory when installing household and industrial networks, as well as operating equipment.

To better understand the difference between grounding and zeroing, we suggest watching this video:

Requirements for grounding and grounding

Grounding is a more serious protective measure than grounding. This scheme requires the creation of a separate low-resistance busbar, which is connected to a ground electrode buried in the ground and arranged in accordance with the standards. All requirements for grounding, its elements and arrangement are specified in the PEU and GOST 12.2.007.0.

In the industrial sector the following must be grounded:

• electric drives;
• electrical equipment housings;
• metal structures of buildings;
• shielded braiding of low-voltage electrical cables;
• housings of electrical distribution panels and similar structures.

More flexible requirements are imposed on zeroing, namely:

• neutral and phase conductors are selected in such a way that, in the event of a breakdown, a current sufficient to trigger an RCD or other protective mechanism appears on the equipment body;
• The grounding conductor from the device to the grounded neutral must be continuous, that is, it must not contain any switching devices in the circuit.

Let's sum it up

Ensuring the safety of life and health is the primary task of the state, society and, naturally, the individual himself. To do this, you must strictly adhere to established rules, instructions and requirements. One of the factors dangerous to human health is electricity, so it is very important to ensure sufficient electrical safety at work and at home using certain events and protective technical means.

Save time: selected articles delivered to your inbox every week

Protective grounding device is a method of electrically connecting a protective conductor to non-current-carrying enclosures of electrical installations exposed to phase short-circuit currents. Protective circuit, main task which is to prevent electrical injuries associated with peak current values ​​during a short circuit.

To understand the essence of the device, you should know the basic theoretical issues.

Main goals, tasks of grounding

The main task of protective grounding, according to GOST requirements, is to prevent people from being exposed to peak currents during a short circuit and to remove voltage from electrical installation housings through a grounding device into the ground. All measures are taken to prevent the possibility of electrical injury.

The operating principle of protective grounding and grounding is to reduce the current strength to a minimum level and damaging factors when touching short-circuited parts of electrical appliances and installations.

In this case, the voltage level on the housings of protected devices decreases, the potentials are equalized due to the increase in this value on the surface to a level equal to the potential of the equipment with the ground wire.

Applications include three-phase equipment and circuits. They must be equipped with a solidly grounded neutral at a voltage below 1000.V; for higher circuit voltages, any method of conducting the neutral wire is selected.

The main purpose of the protection device is to reduce the voltage level to a safe value on the equipment housing and the protection circuit, as well as to reduce the current flowing through the human body when touching a live area.

The rated value of the AC circuit voltage is over 380 V and the DC value is 440 V - such electrical circuits must be equipped with grounding, especially when hazardous conditions and high-risk areas.

A device with a metal casing must be grounded:

When a phase wire short-circuits on the device body, and a person touches it with his hand, a dangerous electric current passes through his body. When grounding, the main part of the voltage will go to the circuit, because its resistance is less than that of the human body.

The difference between working grounding and protective grounding

Working grounding. The principle of operation is to connect several separate objects of the building's electrical circuit to the ground. This could be the neutral winding of a generator, or other various devices.

It is intended to provide proper operation electrical installations, regardless of the conditions of its use. This type of protection is implemented by directly connecting the grounded housings of electrical installations with grounding conductors.

Rarely enough working grounding can be carried out using specialized devices - these can be breakdown fuses, resistors.

Protective grounding and grounding, as mentioned above, performing work on electrical connection with metal non-current-carrying parts of devices. At the same time, the main work protective circuit, is to prevent electrical injuries when a person touches the equipment body, because the current from it is diverted to a grounding circuit, the resistance of which is less than the resistance of the human body.

Therefore, the difference between these two protective devices, is the principle of their operation. If the working one equalizes the potentials, then the protective one diverts the current to the grounding circuit, as a rule, along a solidly grounded neutral.

But when equipping your premises with any type of protection, the greatest operational efficiency will be achieved provided that short-circuit currents do not increase due to a decrease in the level of grounding resistance.

Something else to keep in mind. Not a single grounding circuit can perform the work of automatic circuit breakers and protective shutdown devices in case of current leakage. And these devices will not be able to perform their work reliably without protective grounding.

Requirements for protective grounding

Protective grounding is a more rigid device than circuit grounding. It provides for the laying of a separate bus, a fairly low level of resistance, which goes to a system of grounding conductors driven into the ground in the form of a triangle.

Calculation of protective grounding requires knowledge of many formulas and the availability of many initial data. Therefore, it is customary to use for housing stock standard projects for each region.

The grounding installation involves laying a neutral bus or any other method of draining current in a single-phase circuit. In this case, the resistance values ​​of each grounding conductor to the substation or supply transformer, adding up, form the resistance value of the protective device.

This value may vary, but the requirements for protective grounding and grounding provide for the general value of the maximum possible level of circuit resistance.

Household grounding

As a rule, power supply systems must have a protective grounding resistance of 4 ohms to 30 ohms. For arrangement, as a rule, steel corners and a strip 40 mm wide are used. They provide for the use of a copper busbar of sufficient cross-section, in accordance with GOST. This is a mandatory requirement.

When using a protective conductor with copper wire 0.5 mm2 is not enough for us even 100 meters of wire to achieve critical value. The most stringent requirements are imposed when servicing areas:

1. Installations with a circuit voltage of up to 1000 V are equipped with a device whose resistance should not exceed 0.5 Ohm. The value of the grounded loop is measured using a special measuring instrument– resistance meter. This measurement is carried out by two additional ground electrodes. Having separated them to a certain distance, we take measurements, then moving the electrode, we take several measurements. The worst result is taken as the nominal value.
2. To service the transformer circuit and other power sources, with voltage values ​​from 220 V to 660 V, the value should be from 2 Ohms to 8 Ohms.

Industrial protective grounding

Usage additional measures to equalize potential values ​​- this is the main “duty” of using protective equipment for production facilities. For achievement reliable protection, all metal parts of structures and devices, and communication pipelines are connected to the grounding conductor.

In residential premises, bathrooms and steel water supply, sewerage, and heating pipes should be equipped in this way. Nowadays, albeit rarely, they do occur. On industrial facilities ground:

Parts that do not require protection:

• metal cases of instruments and equipment installed on a steel platform, the main thing is to ensure reliable contact between them;
• various areas with metal fittings, installed on wooden structures, the exception is objects where protection extends to these objects;
• electrical equipment housings with safety classes 2 and 3;
• when introducing electrical wiring into the building with a voltage not exceeding 25 V, and passing it through a wall made of dielectrics.

In conclusion, it should be noted.

Protective grounding is used in alternating current networks up to 1 kV with a solidly grounded neutral, above this voltage value with all types of neutral wire conduction.

After installing each type of protection, it is necessary to check the resistance value of the protection. After this, an inspection report is drawn up. Measurements are carried out in summer and winter, at which time the soil has the greatest resistance.