What is grounding and why is it used. What types of grounding systems exist and what is protective grounding? Errors in the grounding device

Grounding refers to the connection of individual components of electrical appliances and equipment to the ground. The grounding kit includes a grounding conductor and a conductor connected to it, which is connected to the ground. This device allows you to prevent injury from electric shock to a person (if the equipment is not grounded, touching it, a person, being a conductor, automatically passes electricity through himself, which creates a striking effect). In practice, there are enough a large number of cases where the use of grounding devices saved people's lives.

Grounding classification

Types of devices differ, depending on their purpose:

• Industrial or working. established requirements operation of electrical installations, it is determined that all current-carrying parts of the equipment must be grounded. This ensures normal working conditions and prevents various injuries. And safety in this case is not in the first place. A working grounding device is necessary to ensure the operation of installations in emergency conditions when the insulation is broken, or the appearance of an electric charge on the body of the machine or other equipment is detected. In particular, it is customary to ground the neutrals of generators and transformers;

Additional Information. Industrial or commercial earthing can be installed directly, or can use various additional devices(for example, reactors or arresters).

• For the safety of people. This type of device is used to prevent electric shock to a person. When designing an electrical circuit and laying wiring, it should be remembered that the human body is a conductor with a sufficiently large resistance. Electric shock does not occur if there is no closed circuit when touching a conductive part of the equipment or a wire. electrical circuit. If there is no ground, then the current from the conductor will pass through the body and go into the ground, which will create a closed circuit. As a result of such a passage of current, a person is injured - due to the presence of resistance, the conductor (person) will heat up to high temperature, which can lead to death;

Note! In places with high humidity grounding is a must. The more wet surface, topics large quantity current will pass through a person upon contact with a bare conductor, which means that the risk of injury is higher.

• Lightning rods. To understand why you need grounding from lightning, you should know that at the place of their impact, the temperature can reach 30,000 degrees Celsius, which means that there is a threat of fire, as well as people's lives, so it is very important to install appropriate devices on buildings. In addition, it should be borne in mind that, according to statistics, 20% of fires in private homes are caused by lightning strikes.

The most important function of grounding is still protective. At the same time, the principle of operation of such devices is the same for all described types, only lightning rods have certain differences.

Lightning protection

The protection system against these natural phenomena consists of three parts:

• Lightning receiver. His task is to take the hit on himself and transfer the current further along the circuit. Externally given element is a round metal rod. Its diameter does not exceed 10 mm, and the length is rarely less than 250 mm (it is calculated based on the radius of the required protection zone: than more area buildings, the longer the lightning rod should be). As a rule, this element is installed on the roof as high as possible so that the lightning strike falls on it;
• The second element is a tap for current. Its task is to transfer current from the receiver to the ground electrode. It is a wire rod with a diameter of 6 mm. It is connected to the lightning rod by welding, and then lowered along the wall of the building and connected to the ground electrode;

Important! The current collector should be removed from doors and windows to the maximum distance to avoid getting the charge inside the room. Also, during installation, it is strictly forbidden to bend this element of lightning protection in order to avoid the occurrence of a spark discharge at the place of deformation.

• The ground electrode itself. In private homes, it is usually common for lightning protection and for household electrical appliances. On the industrial enterprises separation of such circuits is allowed. The grounding conductor is a device consisting of three conductors that are driven into the ground and connected to each other with a steel wire by welding. The device should be located no closer than one meter to the walls and five meters to the porch, as well as walkways and frequent places of walking.

Use of natural ground

Various metal elements available in buildings and structures and in contact with the ground. This can be reinforcement in the foundation, communications underground, various cables passing underground, as well as some elements of ground transport routes (rails). However, they are allowed to be used only if they meet all the requirements for grounding devices, which are established by various technical regulations and recommendations. The main advantage of this method of protection against electrical injuries and ensuring the functioning of the equipment is the savings Money for additional structures.

When using a foundation as a ground electrode, make sure that it meets the following criteria:

• soil moisture level should not be below 3%;
• the environment in the soil should not be aggressive, contributing to the destruction of the material and the manifestation of corrosion;
• there is no mechanical stress in the reinforcement;
• there are no breaks in the electrical circuit formed from metal structures (if necessary, individual elements can be connected by welding, while the cross section of the jumper must be at least 100 mm2);
• the foundation must be made of reinforced concrete.

Artificial ground

The main element of such a system is a specially designed and manufactured circuit. It consists of several metal conductors placed in the ground. As a rule, rods, angles, pipes or other metal products are used for this purpose. Their length must be at least 2.5 m. The main purpose of this design is to dissipate the current inside the ground in order to avoid human injury. The material from which the ground loop is made must correspond to the resistance of the soil in which it is installed, and also take into account the characteristics of the climate (primarily humidity and precipitation). It is strictly forbidden to cover the circuit with anti-corrosion compounds, as this may impair its conductivity, and, therefore, reduce the efficiency of the device.

A conductor is connected to the grounding conductor, which ensures the transfer of current from the electrical installation to the ground loop, creating a closed electrical circuit and protecting people from injury. The only requirement for a conductor is resistance to external influence and strength. As a rule, it is made of steel.

The conductor is connected to the shield, which ensures the distribution of current through the wiring in the room. Modern standards provide for wiring in rooms where people are located with three-core wires. One of the cores is a phase (electricity is supplied through it to the electrical installation), the second is zero (it is without voltage and connects the phase to the ground wire), and the third closes the circuit, directing current to the ground. When the device is plugged into a power outlet, the grounding wire automatically starts to operate, providing protection.

If suddenly, due to wear of the insulation, the current instead of the phase begins to fall on the body of the device, the protective wire leads it to the ground, which eliminates the possibility of injury. In the event of a short circuit due to insulation problems, a circuit breaker will trip, which will turn off the electrical current. In either case, the current will pass through the protective conductor and dissipate in the ground.

So, answering the question of why grounding is needed, it should be noted that its main function is to protect against injury during the operation of electrical appliances and equipment. This is achieved by installing a special circuit in the ground and laying wiring from three-core wires.

Video

In almost all objects connected with electricity, it is necessary to protect people from electric shock. Everyone knows why grounding is needed, but few people know how to properly install it so that it fully performs its functions.

If you connect with all the metal parts of the equipment, then when the potential is placed on them, the electric current will go into the ground. Then, when touching the metal, a much smaller current will pass through a person, which does not pose a danger to him.

How is electricity transmitted to consumers?

Electricity comes from the source through power lines, first to the substation, and then to consumers. Three phase wires are used for its transmission. The fourth conductor is earth. The windings of the substation transformer are connected according to the "star" scheme. The common point (neutral) with zero potential is grounded. This is necessary for the normal operation of electrical equipment. Such grounding is called working, not protective.

The apartment is usually supplied with a voltage of 220 V between the phase and neutral conductors to the common electrical panel. AT a private house input can be 380 V - three phases and neutral. Then the wires diverge to sockets and lighting fixtures throughout the premises. Here, too, one should not forget why grounding is needed. For current, along with the phase and neutral conductors, another one is laid - grounding.

How to protect yourself from electric shock?

One of the ways to eliminate electric shock or significantly reduce it is to install Why do I need a ground loop? It is necessary for household appliances with metal cases: washing machines, electric stoves, refrigerators, etc.

When inducing potential on metal cases home equipment current must go to ground. But for this, you first need to make a device in the form of a metal structure that creates electrical contact with the ground. It can be solid or consist of conductive elements immersed in the ground.

Grounding in the outlet

Why is it necessary to ground electrical appliances in the presence of metal cases or other elements? This question is clear to many. Voltage can be accidentally applied to them when the wire insulation is destroyed or from a short circuit, which is dangerous for a person at the moment of contact.

This also applies to metal parts lamps and chandeliers. In a residential building, a grounding conductor with a cross section of 2.5 mm 2 is laid from the electrical panel to each outlet. Why do you need grounding in the outlet? This is necessary to connect the earth through its contact to a household appliance. Otherwise, it would be necessary to lay a bus around the entire apartment and make connections from it to the body of each device, which is not very aesthetically pleasing.

Grounding contacts are designed so that they are connected first as soon as the plug from the cord of the household appliance is inserted into the socket. If the sockets are connected by a loop, grounding is supplied separately to each of them from the junction box.

Grounding installation

So, why do you need grounding in an individual house? It is made in the form of a closed loop. The shape can be any, but the least materials are spent on a triangular one. Along the perimeter of an equilateral triangle, a trench is dug in the ground to a depth of 1 m, and steel pipes or corners 2.5 m long. For corrosion protection, it is better to use materials with zinc or copper plated. Do not paint electrodes. You can only varnish the places of welding.

The electrodes should protrude 20 cm from the bottom of the trench. The circuit is scalded with a strip, and a grounding conductor made of the same material is led from it to the house. A bolt is welded to the free end, and a PE wire with a cross section of 6 mm 2 or more is inserted into the electrical panel. An ohmmeter checks the electrical resistance of the circuit. By requirements of the PUE for residential buildings, it should be no more than 30 ohms.

If the indicator exceeds the set limit, additional corners are clogged near the contour, and a jumper is made. In this way, the area of ​​​​contact of the structure with the ground is increased. To reduce the resistance of the circuit, the wire from it is replaced with copper, which has greater conductivity. After the trench is covered with soil. Crushed stone, screenings or construction debris are not allowed to be used for this. Moisture-retaining material should be used: clay, peat, loam.

Potential equalization

Today, even children know why grounding is needed. It is important to ensure that the potential difference on the surface of the earth is reduced so that the person is not affected by touch and step voltages. On the site located above the closed loop, the potential changes smoothly, and outside it, the decline occurs sharply. To prevent this from happening, horizontal steel strips connected to the electrodes are buried outside.

According to the requirements of the PUE, it is made of copper. There are special kits on sale, but they have a high cost. For grounding structures of private houses, steel parts are usually used.

Conclusion

Let's summarize. So, why is it necessary? First of all, it is connected with the protection of people from dangerous electric shocks. It is important to properly equip the ground loop and make necessary connections electrical appliances. The health and safety of residents depends on how it is installed and the materials chosen.

Everyone knows that electricity is an essential attribute of modern man. Without the use of electricity, it is impossible to turn on the kettle to drink tea or coffee, heat up food in the microwave or watch TV. Despite the indispensability of electricity, we should not forget about its deceit. A lot of unpleasant cases happen with electric shock, there are even lethal situations.

Greetings Dear friends and readers of the Electrician in the House website. Many felt an unpleasant electric shock when they accidentally touched bare wire. But in everyday life there are situations when a person can be shocked, even if he touches a seemingly harmless household appliance. Why is this happening?

As a rule, this happens when the internal insulation is damaged and the device does not have an earth connection. In this material, we will try to explain to the reader in simple terms what grounding is, how grounding works and why it is necessary.

What does grounding protect against?

The main purpose of grounding in electrical network is protection. For the operation of electrical appliances in the wiring, two wires are provided: phase and zero.

The protection that grounding provides consists in connecting a third conductor connected directly to the ground electrode, which in turn is connected to the ground loop. Thanks to grounding, you can not worry that an emergency caused by a malfunction of a household appliance will lead to an electric shock to someone around you.

Friends, let's see what emergencies can occur and what is it?

The danger of breaking an electrical device is that its case may be energized, thereby making it dangerous. This circumstance may arise if the internal insulation is damaged. For example, when the wires of the device shrink or melt over time, and come into contact with the metal case of the household appliance.

It is impossible to visually notice such an emergency breakdown, but it is enough to touch the electric stove or washing machine, the electric shock will pass immediately.

After many such situations, the question arises: and whether it can effectively protect. The strength of such a blow may be different depending on the condition of the person and the surrounding conditions.

What happens if case not connected to ground? By itself, such a breakdown does not represent anything. Washing machine with a pierced body, it has worked and will continue to work. It will perform its functions perfectly until you touch it.

The thing is that a person is more than 70% water and is an excellent conductor of electricity. When you stand on the floor or touch a wall, your body can act as a conductor. When touching a damaged case, current will begin to flow through your body and into the ground.

Of course, you can avoid electric shock if you wear rubber gloves or shoes, but no one walks like that in the house. If you do not have grounding in your house, and the device beats with current, you should remember that even low voltage can lead to deplorable circumstances.

A value of 50 mA is already dangerous for humans. Such small value current can lead to cardiac fibrillation and even death.

In order not to worry about your life and the health of your family, it is important that the ground is connected in the house. In this case, the dangerous potential available on the device case will go into the ground, protecting you from impact. This is . In addition, it is recommended to install an RCD in addition to grounding, which will turn off damaged equipment at the slightest leak.

The principle of operation of grounding

After the devices are grounded, a breakdown of the internal insulation is not terrible for us. If for some reason the body of the device is energized, a short circuit will occur between the phase and ground. As a result, the circuit breaker will trip. Due to properly installed grounding and the operation of the machine, a person will not be shocked.

However, there are some nuances of electrical engineering. Not always, during a voltage breakdown on the case, the machine can knock out and in such cases the device will be a great helper protective shutdown.

How electrical grounding works

As for the residents of the private sector, basically, in these areas, electricity is supplied to the plots by overhead power lines. As a rule, these are two-wire lines, which consist of phase and neutral wire. In our country, power lines leave much to be desired, because there can be many twists on one cable running along the main line.

Gusts of wind, falling branches and precipitation can break off at any time power cable and if you do not have a protection system in the form of grounding and an RCD installed in your house, then not only the owner of the house, but also all his equipment may suffer. Here, the installation of grounding is a particularly relevant issue.

Today you can create your own good protection for the house and create a ground with my own hands, ensuring the safety of appliances and the health of households.

A properly manufactured and installed protection system can protect electrical appliances even at the moment of a break in the line leading to the house. Currently individual work grounding the house in conjunction with the RCD is considered a popular means of protection against electric shock in your own home.

Grounding work in the private sector

In this section, we will analyze how grounding works using the example of a private house. The power supply scheme of the house shown in the figure consists of an overhead line. overhead line- two-wire, the most common in the private sector. It consists of two phase wires (indicated in red in the figure) and zero ( of blue color). The neutral wire is zero working and protective at the same time. That is, a combined conductor. In electrical literature, it is referred to as a PEN conductor.

In order to divide this conductor into two independent working and protective ones, a special branch is made in the inlet shield of the house to the ground loop. After that, two neutral conductors come out of the input shield, which have different purpose. One of them is a working zero, which serves to operate the devices. Another protective zero - grounding conductor, must have a yellow-green marking and a PE designation.

In the "Electrical Installation Rules" such a grounding system is referred to as TN-C-S. The internal wiring of the house must be three-wire, that is, phase, zero and ground. All sockets in the house must be properly grounded. In this case, the body of the potentially dangerous device will be connected to the protective conductor through the grounding contact of the socket. Particularly at risk is the so-called wet technique these are water heaters, pumps, dishwashers and washing machines.

If during operation the phase wire, as a result of insulation breakdown, comes into contact with the body of the device (for example, this is the case of a refrigerator), then a short circuit will occur between the phase wire (red) and the ground wire (yellow-green), as a result of which the power machine will turn off.

Imaginary protection or incorrect grounding

There are situations where grounding can be dangerous. This is subject to INCORRECT CONNECTION. Friends now consider the case of incorrect ground connection and compare it with the case discussed above.

The figure shows a diagram of incorrect grounding. Its essence is to connect the ground conductor (ground wire in the electrical wiring) to the zero working one. The neutral wire is grounded at the substation, why not ground it from it? Unfortunately, there are specialists in our industry who make such mistakes.

What is the danger? AT good condition the equipment will work flawlessly, all electrical appliances will do their job. Friends, let's now consider another situation when the neutral wire on the line was broken as a result strong wind, while the red is still intact.

When the phase wire is closed to the case, in this case, a short circuit will not occur, since ground wire, which is also a zero worker, is cut off on the way to the house, there is no potential difference between the phase and ground wires, and a short circuit will not occur. From here it is not difficult to guess that the circuit breaker will not turn off, since it simply has nothing to react to (there is no short circuit current).

It follows from this that the body of the refrigerator, being under dangerous voltage, will wait for its victim. The strength of the electric shock in this situation will directly depend on how close the person is to the ground. The better the contact, the harder it hits.

In some cases, an electric shock through the body of the device can be fatal, so that trouble does not happen, you need to know how grounding works in the house.

For example, you touch a pierced electric water heater and at the same time take hold of water pipe. It is also dangerous to take hold of the body of the device, which is energized while standing barefoot on concrete floors. Such a floor can serve as a conductor.

How does an ouzo work with grounding

The sensitivity of the grounding system, and, accordingly, electrical safety can be increased by installing a residual current device (RCD) in the electrical panel. This device reacts to current leakage and turns off when it occurs, thereby de-energizing equipment with damaged insulation. RCD works even in those cases if there is the slightest leakage of current.

In reality, current leakage can occur both through the grounded case of the device, and through the human body (if there is no grounding in the house), which is less pleasant. The figure shows the situation when the current passes through the human body.

For example, a person touches the case of a faulty device, the case of which is not grounded. At the moment of touch, a current begins to flow through a person, and the RCD, reacting to it, will instantly turn off. The duration of the electric shock for a person in this case will be equal to the time the RCD is turned off. It is usually equal to tenths of a second.

Insignificant and short-term exposure to current in most cases does little harm, a person gets pain and discomfort and fear, which disappears after a few minutes.

It would seem that perfect option protection, but not everything is so smooth. Even such a protection system has its drawbacks:

• if the device does not have grounding, then, therefore, the RCD will not be able to fix the leak, and it will be possible to understand the breakdown only after a small, but electric shock;
• in fact, RCD is a complex electronic device, which cannot operate immediately, it takes time to trip, therefore, protection with RCD alone may be too slow.
• due to the high cost of RCDs, homeowners tend to save money and buy low-quality devices or install one RCD for the whole house, in which case it is difficult to guarantee timely operation.

Do not use RCD devices of dubious quality and little-known brands. Each person is responsible for their own protection, so you need to buy only original and certified goods. AT this moment The market is full of electrical equipment from various manufacturers and you need to be responsible for such a purchase.

Friends, we have examined the principle of grounding, and what can happen when wrong way of grounding. The main advantage of such a connection scheme is that it has its own individual ground loop, and in the event of a wire break on the power line, it will not be able to affect performance in any way.

Important! Do not think that if the house has grounding, then you do not need to use an RCD. Even with the slightest leak, the device can fix the problem and turn off the damaged section of the network, ensuring human safety and health.

Electricity is a friend and enemy of a person, therefore, in order to prevent something unforeseen from happening, it is necessary to do the wiring correctly, and to know How does grounding work in a house?. If there is no knowledge and experience in working with electricity, then it is better to entrust such work to professionals who will do everything, not only quickly, but also qualitatively, taking into account all norms and requirements.

Which is called electric current, provides a comfortable existence modern man. Without it, production and construction capacities, medical devices in hospitals do not work, there is no comfort in the home, urban and intercity transport is idle. But electricity is the servant of man only in the case of complete control, but if the charged electrons can find another way, then the consequences will be dire. To prevent unpredictable situations, special measures are used, the main thing is to understand what the difference is. Grounding and zeroing protect a person from electric shock.

The directed movement of electrons is carried out along the path of least resistance. To avoid the passage of current through the human body, it is offered another direction with the least loss, which provides grounding or zeroing. What is the difference between them remains to be seen.

grounding

Grounding is a single conductor or a group made up of them, which is in contact with the ground. With its help, the voltage supplied to the metal case of the units is reset along the path of zero resistance, i.e. to the ground.

Such electrical grounding and zeroing of electrical equipment in the industry is also relevant for household appliances with steel outer parts. A person touching the refrigerator body or washing machine energized will not cause electric shock. For this purpose, special sockets with a grounding contact are used.

The principle of operation of the RCD

For the safe operation of industrial and household equipment apply, use devices of automatic differential switches. Their work is based on a comparison of incoming phase wire electric current and leaving the apartment along the neutral conductor.

The normal operation of the electrical circuit shows same values current in these areas, the flows are directed in opposite directions. In order for them to continue to balance their actions, ensure the balanced operation of devices, they perform the installation and installation of grounding and grounding.

A breakdown in any section of the insulation leads to the flow of current directed to the ground through the damaged area, bypassing the working neutral conductor. The RCD shows an imbalance in the current strength, the device automatically turns off the contacts and the voltage disappears in the entire working circuit.

For each individual operating conditions provided various settings to trip the RCD, typically the setting range is 10 to 300 milliamps. The device works quickly, the shutdown time is seconds.

Operation of the grounding device

To attach to the housing of a household or industrial equipment a PE conductor is used, which is output from the shield along a separate line with a special output. The design provides connection of the body to the ground, which is the purpose of grounding. The difference between grounding and zeroing is that at the initial moment when the plug is connected to the outlet, the working zero and phase are not switched in the equipment. The interaction disappears last minute when the contact opens. Thus, the chassis grounding has a reliable and permanent effect.

Two way grounding device

Protection and voltage tap systems are divided into:

• artificial:
• natural.

Artificial grounds are designed directly to protect equipment and people. Their device requires horizontal and vertical steel metal longitudinal elements (often pipes with a diameter of up to 5 cm or corners No. 40 or No. 60 with a length of 2.5 to 5 m are used). Thus, grounding and grounding are different. The difference is that a specialist is required to perform high-quality grounding.

Natural grounding conductors are used in the case of their closest location next to the object or residential building. Pipelines made of metal in the ground serve as protection. It is impossible to use for the protective purpose lines with combustible gases, liquids and those pipelines, the outer walls of which are treated with an anti-corrosion coating.

Natural objects serve not only to protect electrical appliances, but also fulfill their main purpose. The disadvantages of such a connection include access to pipelines by a sufficiently wide range of people from neighboring services and departments, which creates a danger of violating the integrity of the connection.

Zeroing

In addition to grounding, in some cases zeroing is used, you need to distinguish what the difference is. Grounding and zeroing divert voltage, they just do it in different ways. The second method is electrical connection housing, in the normal state not energized, and the output of a single-phase source of electricity, the neutral wire of the generator or transformer, the source direct current at its midpoint. When zeroing, the voltage from the case is reset to a special switchboard or transformer box.

Zeroing is used in cases of unforeseen power surges or breakdown of the insulation of the case of industrial or household appliances. A short circuit occurs, leading to blown fuses and instantaneous automatic shutdown, this is the difference between grounding and neutralizing.

Zeroing principle

Variable three-phase circuits use a neutral conductor for various purposes. To provide electrical safety with its help, they get the effect of a short circuit and the voltage that has arisen on the case with phase potential in critical situations. In this case, a current appears that exceeds the nominal value. circuit breaker and contact is terminated.

Zeroing device

The difference between grounding and grounding can be seen from the connection example. The case is connected with a separate wire to zero on To do this, the third core is connected in the socket electric cable with the terminal provided for this in the socket. This method has a disadvantage, which is that for automatic shutdown a current is needed that is larger than the specified settings. If in normal mode the disconnecting device ensures the operation of the device with a current of 16 amperes, then small breakdowns of the current continue to leak without tripping.

After that, it becomes clear what is the difference between grounding and grounding. Human body when exposed to a current of 50 milliamps, it may not withstand and cardiac arrest will occur. Zeroing from such current indicators may not protect, since its function is to create loads sufficient to turn off the contacts.

Grounding and zeroing, what's the difference?

There are differences between these two methods:

• when grounding, the excess current and the voltage that has arisen on the case are discharged directly to the ground, and when zeroed, they are reset to zero in the shield;
• grounding is more effective ways in the issue of protecting a person from electric shock;
• when using grounding, safety is obtained due to a sharp decrease in voltage, and the use of zeroing ensures that the section of the line in which the breakdown to the case has occurred is turned off;
• when performing zeroing, in order to correctly determine the zero points and choose the protection method, you will need the help of a specialist electrician, and any home craftsman can make grounding, assemble the circuit and deepen it into the ground.

Grounding is a voltage dissipation system through a triangle in the ground made of a metal profile welded at the junctions. A properly arranged circuit gives reliable protection but all the rules must be followed. Depending on the desired effect, grounding and zeroing of electrical installations are selected. The difference between zeroing is that all elements of the device that are not under current in normal mode are connected to the neutral wire. Accidental contact of the phase with zeroed parts of the device leads to a sharp jump in current and shutdown of the equipment.

The resistance of the neutral neutral wire is in any case less than the same indicator of the circuit in the ground, therefore, when zeroing, a short circuit occurs, which is basically impossible when using an earth triangle. After comparing the operation of the two systems, it becomes clear what the difference is. Grounding and zeroing differ in the method of protection, since there is a high probability of the neutral wire burning out over time, which must be constantly monitored. Zeroing is used very often in high-rise buildings, since it is not always possible to arrange a reliable and complete grounding.

Grounding does not depend on the phase of the devices, while the grounding device requires certain conditions connections. In most cases, the first method prevails in enterprises where, according to safety requirements, increased safety is provided. But in everyday life, recently, a circuit has often been arranged to dump the resulting excess voltage directly into the ground, this is a safer method.

Grounding protection refers directly to the electrical circuit, after a breakdown of the insulation, due to the flow of current into the ground, the voltage is significantly reduced, but the network continues to operate. When zeroing, a section of the line is completely turned off.

Grounding is in most cases used in lines with an arranged isolated neutral in IT and TT systems in three-phase networks with voltage up to 1 thousand volts or more for systems with a neutral in any mode. The use of grounding is recommended for lines with a grounded dead neutral wire in TN-C-S, TN-C, TN-S networks with available N, PE, PEN conductors, this shows the difference. Grounding and zeroing, despite the differences, are human and instrument protection systems.

Useful terms of electrical engineering

In order to understand some of the principles by which protective grounding, grounding and disconnection should know the definitions:

A solidly grounded neutral is a neutral wire from a generator or transformer that is directly connected to a ground loop.

It can serve as an output from the source alternating current in a single-phase network or the pole point of a DC source in two-phase lines, as well as the average output in three-phase DC networks.

An insulated neutral is a neutral wire of a generator or transformer that is not connected to the ground loop or is in contact with it through a strong resistance field from signaling devices, protective devices, measuring relays and other devices.

Accepted designations in the network

All electrical installations with grounding conductors present in them and neutral wires in without fail are subject to labeling. Designations are applied to tires in the form of the letter designation PE with alternating transverse or longitudinal identical stripes of green or yellow color. Neutral neutral conductors are marked with the blue letter N, which is how grounding and grounding are indicated. The description for the protective and working zero is to affix the letter designation PEN and color it in a blue tone throughout with green-yellow tips.

Letter designations

The first letters in the explanation to the system indicate the selected nature of the grounding device:

• T - connection of the power source directly to the ground;
• I - all current-carrying parts are isolated from the ground.

The second letter is used to describe the conductive parts in relation to the connection to earth:

• T speaks of the mandatory grounding of all open live parts, regardless of the type of connection with the ground;
• N - means that the protection of open parts under current is carried out through a solidly grounded neutral from the power source directly.

The letters through the dash from N indicate the nature of this connection, determine the method of arranging the zero protective and working conductors:

• S - PE protection of the zero and N-working conductors is made with separate wires;
• C - one wire is used for protective and working zero.

Types of protective systems

The classification of systems is the main characteristic according to which protective grounding and grounding are arranged. General technical information is described in the third part of GOST R 50571.2-94. In accordance with it, grounding is carried out according to the schemes IT, TN-C-S, TN-C, TN-S.

The TN-C system was developed in Germany at the beginning of the 20th century. It provides for combining a working neutral wire and a PE conductor in one cable. The disadvantage is that when zero burns out or another connection failure occurs, voltage appears on the equipment cases. Despite this, the system is used in some electrical installations up to our time.

TN-C-S and TN-S systems designed to replace a failed scheme grounding TN-C. In the second protection scheme, two types of neutral wires were separated directly from the shield, and the circuit was complex metal structure. This scheme turned out to be successful, since when the neutral wire was disconnected, line voltage did not appear on the casing of the electrical installation.

The TN-C-S system is different in that the separation of the neutral wires is not carried out immediately from the transformer, but approximately in the middle of the main. It was not good decision, since if a zero break occurs before the separation point, then the electric current on the case will be life threatening.

The TT connection scheme provides a direct connection of live parts to earth, while all open parts of the electrical installation with the presence of current are connected to the earth circuit through an earthing conductor, which is independent of the neutral wire of the generator or transformer.

According to the IT system, the unit is protected, grounding and grounding are arranged. What is the difference between this connection and the previous scheme? In this case, the transfer of excess voltage from the housing and open parts occurs to the ground, and the source neutral, isolated from the ground, is grounded by means of high resistance devices. This scheme is arranged in a special electrical equipment, which should have increased security and stability, for example, in medical institutions.

Types of grounding systems

The PNG grounding system is simple in design, in which the neutral and protective conductors are combined along the entire length. It is for the combined wire that the indicated abbreviation is used. The disadvantages include increased requirements for the well-coordinated interaction of potentials and the conductor cross section. The system is successfully used for zeroing asynchronous units.

It is not allowed to perform protection according to this scheme in group single-phase and distribution networks. It is forbidden to combine and replace the functions of the neutral and protective cables in a single-phase DC circuit. They use an additional one marked PUE-7.

There is a more advanced zeroing system for electrical installations powered by a single-phase network. In it, the combined common conductor PEN is connected to the current source. The division into N and PE conductors occurs at the point of branching of the main into single-phase consumers, for example, in the access shield of an apartment building.

In conclusion, it should be noted that protecting consumers from electric shock and damage to electrical household appliances during power surges is the main task of energy supply. The difference between grounding and grounding is simply explained, the concept does not require special knowledge. But in any case, measures to maintain the safety of household electrical appliances or industrial equipment must be carried out constantly and at the proper level.

Grounding and landing. The words are monosyllabic. Landing means docking with the surface. Grounding is a term from the field of electrical appliances and related. It remains to analyze what is the connection with the earth.

What is grounding

If the connection of electrical equipment with the soil is discussed, it may be about grounding. Sometimes, a discharge accumulates on the surface of the devices. Among the reasons is a violation of the surface of the wires. Through the leaky insulation, the current from the equipment passes to the bodies of people and animals touching it.

The flesh becomes a conductor on the path of electrons to the ground. Knowing this, people suggest a different path for tension. The escort is made by a wire that goes from the equipment into the soil. Skin resistance to current is higher than that of metal.

Having received a choice, the released current passes to the alloys. The soil where they lead perfectly absorbs energy. Especially well the current "spreads" in aquifers earth.

Invented, how to make a ground Benjamin Franklin. He owns the idea of ​​a lightning rod. Initially, the American attached a metal rod to the machine conductor.

The charge from the latter began to smoothly flow down the spire, just as before a thunderstorm the current descends along the masts of ships and the spiers of churches. Franklin was confident in the electrical nature of lightning and guessed that at a high potential of the field, some of the electrons from it can be drawn by conductors.

The total charge is reduced. Instead of spark lightning, a corona discharge is born, the same flowing and only slightly radiating. This is not able to ignite the surrounding objects and singe the flesh.

It turns out, from a practical point of view ground loop It is the protection of health and material property. We will discuss the role of current diversion into the soil in more detail in the next chapter.

Why is grounding necessary?

If you describe the current, then it is a substance without smell, taste and color. When touching a live object, a person may not be aware of the danger. It starts sparking only in the event of a short circuit. It occurs when connecting points of an electrical circuit with different electronic potentials.

"Silent" grounding is designed to protect against an equally imperceptible voltage. The ground potential is equalized with the potential of the body of the electrical appliance. However, it is possible to completely divert the current to the ground only with low resistance in the circuit section.

Grounding is an alternative to grounding. Its wire is connected to the transformer neutral of the substation. When a phase hits the device, a short circuit occurs. It serves as an impetus for the operation of fuses in the network.

The device switches off automatically. That is, zeroing gives people a signal about malfunctions, but the voltage remains on the instrument cases. It is necessary to repair the network, only then return to the operation of the equipment. Relevant for industrial facilities. Home grounding better.

Zeroing is also called working grounding. They are guided not so much by issues of safe work as by insurance in case of an accident. It is necessary to ensure that the equipment can operate in extreme conditions.

Ordinary grounding is called protective. His the main role to save lives and health of people. For an electric shock, by the way, it is not enough to touch the device under voltage. You need an electrical circuit.

There are 3 participants in it - the device, the body and the earth. If a person, for example, hangs in the air, the circuit will not work and the electric shock will pass. But, as the heroine of Ostrovsky's story "Thunderstorm" complained: - "Why don't people fly?"

The first chapter pointed out that better than earth current is drawn by water. Deadly, usually, are electric arcs that form through the human body into wet soil, a puddle.

Suffice it to recall scenes from films with lowering hands into water with a hair dryer turned on. In general, instrument grounding is especially important in wet rooms, areas at risk of flooding.

The ability of different soils to “perceive” the current in the same way is earth resistance. The earth counteracts the spreading of electrons over it. There are limits to this opposition. For private cottages and cottages, a resistance of 30 ohms is recommended. On gas pipelines and lightning rods, 10 ohms are enough, and on telecommunications - 2-4 ohms.

The third type of grounding is recognized as the very lightning rod created by Benjamin Franklin. Lack of protection on household and industrial appliances rarely leads to fires.

The temperature at the stress point is low. In order to start a fire, you need a spark and flammable gases in the air. The factors rarely overlap. When lightning strikes, the point of interaction with it heats up to 30,000 degrees. 1/5 fires on personal estates are the result of a celestial discharge.

That's the statistics. That's why, grounding in a private house necessary both on appliances and on the roof in the form of a metal spire. How to install it, and make protection on electrical equipment, we will tell further.

How to make grounding with your own hands

The spire of a lightning rod is usually a steel rod a centimeter wide and about 2.5 meters long. This is a current receiver. Install it at the top of the roof. It is known that lightning attracts high-rise objects.

A wire rod is lowered from the receiver along the walls of the house. it earth wire with a round and wide section. They lead the wire rod at a distance from windows and doors. The ground electrode itself is made common with household appliances dwellings.

In other words, conductor wires from the house and from the roof lead to one circuit buried in the ground. A frame of 3 electrodes is enough. So called conductors of the 1st type in contact with the ionic conductor.

The electrodes for the ground loop must be "bare", that is, without anti-corrosion dielectrics. Limited to varnish in places of welding.

It is necessary to take into account the gradual thinning of steel under the action of corrosion. Therefore, the electrodes are taken with a margin in cross section. There are minimum requirements. So, the width of the galvanized rod should be 6 millimeters or more. The minimum for ferrous metal rods is a centimeter.

The electrodes in the ground loop are connected with a steel tape. This is called thrips. It is welded with electrodes. Can do do-it-yourself grounding. It is important to take the contour one meter from the walls and 5 meters from the walking paths and the porch of the house.

Accordingly, it is convenient to lead the conductors to the rear walls of the building and the roof slopes. However, there are houses with several entrances. It is important to remove the contour by 5 meters from each.

In private homes, it is convenient to make a natural grounding system. It consists in using elements already present in the structure to conduct current. On the foundation, for example, reinforcement can conduct stress. In general, you can save on the purchase of wire and maintain the natural look of the building. The wire, by the way, is called an artificial ground electrode.

AT apartment building the grounding system is connected to the shields. They must be included in the system circuit. The connection is made through ground bus. There are many conductors connected to it. The bus allows you to equalize the potentials of the network.

Make an element of iron. In fact, copper and aluminum will work better, but are expensive and there is a risk of cutting out the metal for the purpose of taking it to collection points. You can even make a tire out of gold, which is also illogical in the presence of cheap and uninteresting iron alloy assemblers.

The ground wire, even in an apartment, even in a house, must be included in the main wiring and match in cross section with the phase conductor in the wiring around the house. That is the standard. Accordingly, the wiring is made three-core.

One “lived” in it is zero, the second is a phase, and the third is grounding. socket with it is provided with contacts. They are connected to the body. Its inclusion automatically “starts” not only the current run, but also the operation of the ground electrode system.

Insulation wear does not only lead to short circuits. They are reacting to automatic protection devices. More often, small currents “leak” from the system. They are set to RCD. The abbreviation stands for "safety shutdown device". However, both devices direct the excess current to the ground wire, which leads the voltage to the ground.

In addition to stationary grounding, there is a portable one. It is used, as a rule, at enterprises during disconnection from the current of network sections near electrical installations. There is a risk of erroneous voltage supply or induced current. The latter is understood as a kind of transfer of electrons from the neighboring line, which remains conducting.

Portable grounding- this is a conductor carried with you, preferably made of copper. She has minimal resistance. The wire is connected to the current carrying line. It is de-energized beforehand. The other end of the portable conductor is connected to the ground electrodes. Speech at least about natural, at least about artificial outlets for the flow of electrons.

What tool is needed

For artificial grounding take steel rods, corners and pipes. The latter can be either round or rectangular. Concrete will work too. It has an electrically conductive type. The use of concrete is advantageous in terms of the material's resistance to corrosion.

The electrodes are driven into the ground with a sledgehammer. With factory sets they work with chippers. To connect the pins, brass threaded couplings are taken. The connection of the conductive wire to the electrode goes through the clamp. Take steel.

A special paste helps to reduce resistance at the joints. It is available in electrical stores. Weld the structure, of course, welding machine or the old fashioned way with a soldering iron. A stepladder during installation also comes in handy.

Do not forget about the steel, copper coupling, if we do grounding in an apartment building. In general, the exact set of inventory depends on the type of building, its number of storeys, and network capacity.