How to do zeroing yourself if there is no zero. Protective grounding: device, purpose, principle of operation

Modern devices, equipment and household appliances that consume electrical energy require compliance with certain safety measures when handling them. One of these events is zeroing in the apartment. This system is very similar to, but differs significantly in the principle of its operation.

Basic concepts of zeroing

In the absence and impossibility of its equipment, grounding is used. However, this type of protection does not directly protect against the effects of electric current. When touching live parts, it is grounding that provides the necessary safety. Grounding differs from grounding in the rapid action of protective equipment. That is, when you touch a dangerous place, a circuit breaker is triggered, cutting off the electric current.

To ensure the required effect, the neutral conductor is connected to the body of a device and the neutral neutral wire of the electrical network. Such a scheme will be called zeroing. Thus, the neutral wire not only performs its main function, but also provides the necessary protection.

However, zeroing does not always guarantee high level security. If the neutral wire breaks for any reason, all devices in the apartment connected to the network will have a phase on their body instead of zero. This situation creates a serious danger to people's lives and health. Sometimes accidents occur as a result of wire confusion, when a phase may be connected instead of a neutral. The maximum effect from using zeroing can be obtained by knowing well the principle of its operation.

How does zeroing work?

If any device or equipment connected to the neutral wire gets on the body, a short circuit occurs. In a damaged circuit, a circuit breaker trips, cutting off the electrical current. In addition, electricity can be turned off using a fuse. The shutdown time for each case is regulated by the PUE. For example, with a nominal phase voltage of the electrical network of 220 or 380 volts, it does not exceed 0.4 seconds.

Special conductors are used for the grounding device. IN single-phase network this is usually the third core of the cable or wire. These conductors are subject to increased demands. Their resistance must be small so that the protective equipment can operate within the specified period of time. In case of high resistance, the machines very often do not work. Because of this, the likelihood of contact with the body of the equipment or device increases sharply. Therefore, very stringent requirements have been established for the quality of installation and connections of such sections. No breaks should be made in these conductors for the purpose of connecting circuit breakers or fuses. Failure to comply with these rules will lead to the fact that zeroing in the apartment will have a low effect.

Zeroing provides not only quick disconnection of the device from the network. With its help, the minimum voltage is set at which the trigger occurs in the event of a touch. As a result, electrical safety is significantly improved.

If there is no grounding in the apartment, protective grounding for sockets in practice is carried out as follows. Located in electrical panel the main neutral wire is divided into two components. They consist of a zero working and protective conductor. The protective conductor is brought to the socket and connected to the ground contact located in it. This provides additional security.

The difference between grounding and grounding is significant. Let's try to understand this issue. Zeroing according to the PUE is a deliberate protection that is used exclusively for industrial purposes and should not be practiced at the household level.

But still, very often, zeroing is done in apartments. According to all forecasts, such a system is far from perfect and not at all safe. Why then do they resort to such extreme measures? Partly due to a lack of knowledge in this area, or due to a hopeless situation.

When renovating an apartment, many people do full or partial electrical installations not only for the convenience of locating sockets and switches, but also to replace worn-out electrical wiring. Also, modern man wants to make his home safer, therefore, the customer’s wishes boil down to ensuring that the house has grounding.

What is used in new buildings: grounding or grounding?

New buildings according to all the rules are provided with a three-wire cable (phase, neutral, ground) in a single-phase system and a five-wire cable (three phases, neutral, ground) in a three-phase system, i.e. according to the TN-C-S or TN-S grounding system. In such systems there is no smell of zeroing.

Is it possible to ground the old foundation?

The old foundation is very rarely reconstructed. In order to transfer from the TN-C system, i.e. two-wire system (phase and neutral), it is practically impossible to use such efficient systems as TN-C-S and TN-S, in which a protective conductor PE (ground) is provided, on your own. Modernization is mainly carried out by a specialized electrical engineering company.

There is no protective conductor (ground) in the TN-C system. No one will pull a separate grounding wire from their apartment in order to make grounding, for example, in the basement. Although, some decide to provide themselves with grounding if the apartment is located on the ground floor. But for the majority of the population, such a maneuver is not possible.

Before connecting the protective PE (ground) conductor from the apartment, you need to determine what possibilities are available. Determine the presence of grounding in the panel room to which the third conductor can be connected. The switchboard must have either a PE grounding bus, or all floor switchboards must be connected to each other by a metal bus, and ultimately connected to the general grounding circuit of the house, i.e. We are talking about re-grounding. This makes it possible to connect the grounding conductor from the apartment to the shield. If these two options are absent, it means that there is no grounding in the house and in this case they do the prohibited grounding. As mentioned earlier, this method in the residential sector is not at all safe.

How is zeroing done?

Grounding does not act as grounding; such a circuit is designed for the effect of a short circuit. In production, the loads are more or less evenly distributed, and the zero performs mainly protective functions. Here the neutral conductor is connected to the motor housing. If voltage from one of the phases hits the motor housing, a short circuit will occur. In turn, the circuit breaker or differential protection circuit breaker will switch off. One more indisputable fact should be taken into account - all electrical installations in production are connected to each other by a metal grounding bus and connected to the common grounding circuit of the entire building.

Is it possible to do zeroing in an apartment?

It's possible, but not necessary. What does this mean? Let's assume your equipment (washing machine, boiler, etc.) is zeroed. If for some reason the neutral wire burns out or the electrician accidentally mixed up the connection of the wires (connected a phase instead of zero), then your equipment will simply burn out due to high voltage.

If you have planned electrical work in your home, and then find out that the house does not have any form of grounding, it is still better to lay a three-core cable. We connect two conductors (phase and neutral) as planned, but leave the third protective grounding conductor unused until we wait for the reconstruction of the risers, where grounding will be provided.

If you still decide to zero the apartment, you need to remember that you are taking on a huge responsibility. In any case, if there is grounding or grounding, you cannot neglect the installation of protective equipment, such as an RCD (Residual Current Device) and a voltage limiter.

Protective grounding is a system in which conductive parts of equipment that are not normally energized are connected to the neutral. For protective purposes, a connection is deliberately created between open conductive elements of a solidly grounded neutral (in three-phase current networks).

In single-phase current networks, contact is created with a solidly grounded terminal of a single-phase current source, and in the case of DC- with a solidly grounded point of the current source. Although grounding has serious drawbacks, the system is still widely used in many applications for current protection.

Difference between grounding and grounding

There are differences between grounding and grounding:

1. In the case of grounding, the excess current and the voltage that appears on the housing are redirected to the ground. The principle of zeroing is based on zeroing on the shield.
2. Grounding is more effective in terms of protecting people from electric shock.
3. Grounding is based on a rapid and significant reduction in voltage. Nevertheless, some (no longer dangerous) tension remains.
4. Zeroing consists of creating a connection between metal parts, in which there is no voltage. The principle of grounding is based on the deliberate creation of a short circuit when insulation breaks down or current enters non-current-carrying parts of electrical installations. As soon as a short circuit occurs, the circuit breaker comes into play, fuses blow, or other protective measures are activated.
5. Grounding is most often used on lines with an isolated neutral in IT and TT systems in three-phase networks, where the voltage does not exceed a thousand volts. Grounding is used at voltages of more than a thousand volts with a neutral in any mode. Grounding is used in solidly grounded neutrals.
6. When zeroing, all elements of electrical appliances that are not energized in the standard mode are connected to zero. If a phase accidentally touches zeroed elements, the current increases sharply and the electrical equipment is switched off.
7. Grounding does not depend on the phases of electrical appliances. To organize zeroing, strict connection conditions must be observed.
8. In modern houses, grounding is rarely used. However, this method of protection is still found in multi-storey buildings, where for some reason it is not possible to organize reliable grounding. At enterprises where there are increased electrical safety standards, the main method of protection is grounding.

Note! To correctly determine the zero points and select the method of protection, you will need the help of a qualified electrician. You can make grounding, assemble circuit elements and install it in the ground with your own hands.

Scheme of work

As mentioned above, grounding is based on provoking a short circuit after a phase hits the metal body of the electrical installation connected to zero. As the current increases, a protective mechanism is activated that cuts off the power supply.

According to the standards of the Electrical Installation Rules, in the event of a violation of the integrity of the line, it must be turned off automatically. The shutdown time is regulated - 0.4 seconds (for 380/220V networks). To disconnect, special conductors are used. For example, in the case of single-phase wiring, the third core of the cable is used.

For correct zeroing, it is important that the phase-zero loop has low resistance. This ensures that the protection is activated within the required period of time.

Organization of grounding requires high qualifications, therefore such work should be performed only by qualified electricians.

The diagram below shows how the system works:

Application area

Protective grounding is used in electrical installations with four-wire electrical networks and voltages up to 1 kW in the following cases:

• in electrical installations with a solidly grounded neutral in networks TN-C-S, TN-C, TN-S with conductors of types N, PE, PEN;
• in networks with direct current and a grounded midpoint of the source;
• in networks with alternating current and three phases with grounded zero (220/127, 660/380, 380/220).

Networks 380/220 are allowed in any structures where grounding of electrical installations is mandatory. For residential premises with dry floors, there is no need to equip grounding.

Electrical equipment 220/127 are used in specialized areas where there is an increased risk of electric shock. Such protection is necessary in street conditions, where grounding is subject to metal constructions that workers touch.

Checking the effectiveness of zeroing

To check how effective grounding is, you need to measure the resistance of the phase-zero loop at the point furthest from the power source. This will make it possible to check the protection in the event of exposure to current on the housing.

Resistance is measured using specialized equipment. The measuring instruments are equipped with two probes. One probe is directed to the phase, the second - to the neutralized electrical installation.

Based on the measurement results, the resistance level in the phase and zero loop is established. With the result obtained, the single-phase fault current is calculated using Ohm's law. The calculated value of the single-phase fault current must be equal to or greater than the trip current of the protective equipment.

Let's assume that a circuit breaker is connected to protect the electrical circuit from overloads and short circuits. The operating current is 100 Amperes. According to the measurement results, the resistance of the phase and zero loop is 2 Ohms, and the phase voltage in the network is 220 Volts. We calculate the single-phase fault current based on Ohm's law:

I = U/R = 220 Volts/2 Ohms = 110 Amps.

Since the calculated short-circuit current exceeds the instantaneous operation current of the circuit breaker, we conclude that the protective grounding is effective. Otherwise, it would be necessary to replace the circuit breaker with a device with a lower operating current. Another solution to the problem is to reduce the resistance of the phase-zero loop.

Often, when carrying out calculations, the operating current of the machine is multiplied by the reliability factor (KN) or safety factor. The reason is that the cutoff is not always equal to the specified indicator, that is, a certain error is possible. Therefore, using the coefficient allows you to obtain a more reliable result. For old equipment, Kn ranges from 1.25 to 1.4. For new equipment, a coefficient of 1.1 is used, since such machines operate with greater accuracy.

The danger of zeroing in an apartment

Voltage surges are dangerous for both people and household appliances in apartments. IN apartment buildings one of the apartments will receive low voltage, and the other - high voltage. If the neutral conductor breaks in an apartment socket, the next time the electrical installation (for example, a boiler) is turned on, the person will receive an electric shock.

Zeroing is especially dangerous in a two-wire system. For example, when carrying out electrical installation work, an electrician can replace the neutral conductor with a phase conductor. In electrical panels, these conductors are not always marked with a specific color. If replacement occurs, electrical equipment will become live.

According to the standards of the Rules for Installing Electrical Installations at the Household Level, grounding is not permitted for use for domestic purposes precisely because of its unsafety. Grounding is effective only for protecting large industrial facilities. However, despite the ban, some people decide to install zeroing in their own homes. This happens either due to the lack of other methods for solving the problem, or due to insufficient knowledge on this subject.

Zeroing in an apartment is technically feasible, but the effectiveness of such protection is unpredictable, as are possible Negative consequences. Next, we will consider a number of situations that arise when there is grounding in an apartment.

Grounding in sockets

In some cases, it is proposed to protect electrical appliances by jumping the terminal of the socket working zero to the protective contact. Such actions contradict clause 1.7.132 of the PUE, since they involve the use of the neutral wire of a two-wire electrical network as both a working and a protective zero at the same time.

At the entrance to the residential premises there is most often a device designed for switching phase and zero (a two-pole device or a so-called packetizer). Switching of a zero used as a protective conductor is not allowed. In other words, it is prohibited to use as protection a conductor whose electrical circuit includes a switching device.

The danger of protection using a jumper in a socket is that in the event of damage to the neutral (regardless of the area), the casings of electrical installations come under phase voltage. If the neutral conductor breaks, the power receiver stops functioning. In this case, the wire seems to be de-energized, which provokes rash actions with all the ensuing consequences.

Note! When the zero line breaks, any equipment in an apartment or private house becomes a source of danger.

Phase and zero are reversed

When carrying out electrical installation work in a two-wire riser with your own hands, there is a considerable probability of confusion between zero and phase.

In houses with a two-wire system, the cable cores are devoid of distinctive features. When working with wires in a floor panel, an electrician may simply make a mistake by mixing up phase and neutral. As a result, the housings of electrical installations will come under phase voltage.

Zero burnout

Zero break (zero burnout) often happens in buildings with poor wiring. Most often, the wiring in such houses was designed based on 2 kilowatts per housing unit. Today, electrical wiring in old-type houses has not only worn out physically, but is also unable to satisfy the increased number of household appliances.

When the zero line breaks, an imbalance occurs at the transformer substation from which the apartment building is powered.

Misalignment is possible in the general electrical panel of the building or in the floor panel of the house. The consequence of this will be a random decrease in voltage in some apartments and an increase in others.

Low voltage is detrimental to some types of electrical appliances, including air conditioners, refrigerators, hoods and other devices equipped with electric motors. High voltage is dangerous for all types of electrical installations.

An alternative to zeroing

In the TN-S subsystem, the grounding of the protective conductor PE is carried out only in one area - on the grounding circuit of the transformer substation or electric generator. At this point the PEN conductor is separated, and then the protection and working zero do not meet anywhere.

In such a power supply scheme, grounding and grounding organically interact, creating conditions for high electrical safety.

Electricity is characterized by two main parameters: current and voltage. Everyone knows the consequences of excess current (short circuit) - from the failure of a specific electrical appliance to a fire in an apartment or stairwell. Since the danger from a short circuit is obvious, almost every apartment has a regular automatic plug installed in the distribution panel. Disadvantage - the electricity turns off if there is a slight overload. The advantage is protection against the consequences of a short circuit.

But overvoltage is a hidden danger. Most electrical appliances either have a built-in stabilizer that equalizes the voltage, or, as in the case of heaters, voltage drops within 30% of the norm do not affect their performance. Where does the residual potential go from high voltage?

If the device is grounded, it goes into the ground. If there is no grounding in the apartment, it settles on the body or accumulates on the surface of surrounding objects. If such an object is touched, the static potential turns into an electric current, which tends to follow the path of least resistance, in this case, through the human body.

The most dangerous ungrounded water heating electrical appliances, washing machines, electric stoves. The unspoken rule, known since Soviet times, that you should stand near a working electric stove in shoes with rubber soles and not pick up metal pans with both hands is written in blood. Rubber has high resistance Therefore, the flow of electrons does not tend to the ground through the human body.

Naturally, this indicates inadequate grounding in those days. But the majority live in the same apartments with the same wiring, and modern household electrical appliances have become more powerful and, accordingly, more dangerous. How to ground an apartment in a building commissioned before 1998?

The most obvious example of grounding is a lightning rod, which conducts an electrical discharge along the path of least resistance from the highest point into the ground, bypassing the building's electrical communication systems. For high-voltage lines, lightning rods are power transmission line supports, which prevent lightning discharges from reaching the wire, thereby creating voltage drops in the network during a thunderstorm.

The second type is SPD (surge protection device). One electrode is connected to a low-voltage wire, and the other is grounded. The space between the electrodes is filled predominantly with inert gas. When a certain voltage is reached by 1–5%, lower than the maximum at which a particular device can operate, a breakdown occurs - the voltage equalizes. SPDs are used to eliminate residual voltage on network patch cables.

The third type is used for grounding in an apartment building. A neutral or additional grounding wire is used as grounding, which is supplied to each socket as an additional contact for a 220V socket or in the case of an industrial 3-phase voltage of 380V.

Grounding of apartments and private houses

You can ground the house yourself; fortunately, natural earth (soil) is in close proximity. It is enough to conduct an additional protective grounding wire with a cross-sectional area of ​​16 mm for aluminum or 10 mm for copper to all sockets in a private house and ground it near the distribution panel into the soil to a depth of at least 1.5 m. In rural areas, many people ground their residential building in this way way.

But it will not be possible to ground the apartment in this way. Well, where can I get natural soil on the fourth floor? Some “craftsmen” used metal elements of the centralized heating or gas supply system as grounding in old houses. But after a series of cases of electrocution of neighbors, small children, or explosions in the gas supply system, this practice was abandoned. Now grounding or grounding in the apartment is carried out only to the distribution panel.

How to make grounding in an apartment depends on the existing grounding in an apartment building. Grounding in apartment buildings is carried out according to three schemes:

• TN-S modern way grounding, prescribed by regulation since 1998;
• TN-C-S – protective grounding cable is routed only to the distribution panel;
• TN-C - the neutral wire is used as grounding, which is grounded at the transformer substation, for example, grounding in Khrushchev is carried out according to this principle.

How to make grounding in an apartment if there is none? Before making grounding in an apartment with your own hands, you need to decide on a grounding scheme. To do this, you need to open the distribution panel on the staircase. If a five-core wire is carried along the riser, it is at least TN-C-S, which means that the protective ground wire only needs to be connected to the yellow-green protective wire.

Then you need to go to the distribution panel in the apartment, if the electricity meter is located on the staircase, then look at the wires leading from it to the apartment. If there are 3 wires and one of them is yellow-green, it means that the apartment uses a modern TN-S grounding scheme. In this case, you will not have to worry about how to properly ground.

Important! In large modern apartments 3 or more rooms, two phases can be carried into the apartment, accordingly, there will be more wires. The main thing is the presence of a wire with a yellow-green color.
Anyway, before connecting a powerful electrical appliance that consumes more than 3.2 kW/h, check the grounding of the outlet. Perhaps an ungrounded tap was made some time after the house was put into operation.

If there is no protective ground wire in the general distribution panel, this is an old TN-C circuit. In this case, you can only ground the sockets. But, in the event of significant overloads or phase imbalance, which does not happen so rarely, the devices currently connected to the neutralized power supply may fail. The only way out, using the common funds of the residents of an apartment building or independently, is to change the entire wiring.

Stages of self-grounding

If the TN-C-S scheme was used for electrical communications, you can ground the outlets yourself by following the following sequence of actions:

1. De-energize the apartment - unscrew all the plugs or turn off the automatic plugs or slide-type automatic plugs.
2. Clear access to the wiring - remove plaster or other Decoration Materials in the required places.
3. Remove the necessary sockets.
4. Connect the stripped ends of the conductors to the special contacts that are available in Eurostandard sockets.
5. Connect all terminals to grounded sockets.
6. De-energize the riser or house.
7. Connect the conducted grounding to the common grounding of the riser or phase.
8. Turn on the electricity supply in the house and apartment.

Conclusion

Such grounding is effective only if the household appliance supports a connection to an electrical network grounded according to the TN-S scheme. This can be determined by the connection plug. If it is designed for Euro standard sockets, then TN-S is supported.

WITH With the advent of electricity in everyday life, the question of its safe use arose. Let's see how to solve this important problem, let's figure out: what grounding is, how grounding works, how to do zeroing in a private house with your own hands. And besides, is it possible to use grounding instead of grounding?

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What, how and where does it come from?

It is known that electricity is produced by power plants. From them, an electric current with a voltage of tens and hundreds of thousands of volts travels through three phase wires to the consumer.

The voltage is so high because, according to the laws of physics, the higher the voltage, the lower the losses during transmission over long distances.

Then step-down transformer substations convert the high voltage into a much lower (but still dangerous) one, and it will come through wires or underground cables into our home.

The current must come to the electrical appliance, make useful work and leave. In the case of alternating voltage used in everyday life, the phase (supply) and neutral wires are used for this. Where the electric current comes from is clear; but where does the electricity go? To the ground! A little simplified, but by and large it is true. Right into the ground.

The substation transformer has a ground connected to a separate line wire. This is the very “zero” in our → . Those who are especially curious can verify this by examining a conventional transformer substation with by air lines. 3 wires came in, 4 came out. At the input - three phases of high voltage, at the output - three phases low voltage and neutral wire.

Now let's move on to the main thing - human protection.

Grounding in an apartment

To avoid trouble, the body of the device is connected to the ground. Now, when a phase hits the housing, a short circuit occurs and the protection is triggered, cutting off the current supply.