Performing protective grounding. Grounding and grounding of electrical installations: functions, specifics, device. Measures to protect against electric shock

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).

On networks single-phase current create contact with the 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. Grounding consists of creating a connection between metal parts in which there is no tension. The principle of nullification is based on the deliberate creation short circuit in case of insulation breakdown or current contact with 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 zeroing 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 dull 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 a 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 outdoor conditions, where metal structures touched by workers must be grounded.

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 draw a conclusion about the efficiency protective zeroing. 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, next switch on electrical installation (for example, a boiler) will give a person an electric shock.

Zeroing is especially dangerous in a two-wire system. For example, when conducting 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 paragraph 1.7.132 of the PUE, since they involve the use neutral wire two-wire electrical network as both a working and protective zero simultaneously.

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, cable cores are deprived 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 is broken, an imbalance occurs at transformer substation, from which an 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 subsystem TN-S zeroing protective conductor PE is carried out only in one area - on the ground loop of a 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. However, in systems where the neutral is isolated (IT, TT), grounding is not used. Electrical equipment operating within the TT and IT system is grounded through its own circuits. Since the IT system involves supplying power only to specific consumers, consider this method of organizing protection in residential buildings doesn't make sense. The only alternative to incorrect and therefore dangerous zeroing of the PE bus is the TT system. Such a system is especially relevant, because the transition to technically progressive systems TN-S, TN-C-S are technically and financially difficult for houses whose age exceeds 20 - 25 years.

The electrical network, built according to the TT standard, is designed to provide high-quality protection against energized non-current-carrying parts. All work on organizing grounding must be carried out in accordance with the standards specified in paragraph 1.7.39 of the Electrical Installation Rules.

One of the effective means of protection against damage electric shock are protective grounding and grounding of electrical installations. In accordance with GOST 12.1.009–76:

protective grounding – this is intentional electrical connection with the earth or its ecvivalent of metal non-current-carrying parts that may be live;

zeroing – this is an intentional electrical connection withzero protective conductor of metal non-current-carrying conductorsparts that may be live.

In matters of application and practical implementation of protective grounding and grounding, one should be guided by the requirements of not only the PUE, but also GOST R 50571. GOST R 50571.2–94 “Electrical installations of buildings. Part 3. Main characteristics" provides a classification of grounding systems for electrical networks: IT, TT, TN-C, TN-C-S, TN-S (Fig. 2).

In relation to networks alternating current voltage up to 1 kV the designations have the following meaning.

First letter – nature of grounding of the power source (neutral mode secondary winding transformer):

I– isolated neutral;

T– solidly grounded neutral.

Second letter – nature of grounding of open conductive parts (metal casings) of the electrical installation:

T– direct connection of open conductive parts (OCP) with the ground (protective grounding);

N– direct connection of the frequency converter with the grounded neutral of the power source (grounding).

Subsequent letters (if any) – arrangement of zero working and zero protective conductors:

WITH– zero working (N) and zero protective (PE) conductors are combined throughout the network;

C– S– conductors N and PE are combined into parts of the network;

S– N and PE conductors operate separately throughout the entire network

Rice. 2. Types of grounding systems

Conductors used in various types networks must have certain designations and colors (Table 1).

Table 1

Conductor designation

The scope of application of these protection methods is determined by the neutral mode and the voltage class of the electrical installation.

Protective grounding consists (Fig. 3) of a ground electrode 3 (metal conductors located in the ground with good contact with it) and a grounding conductor 2, connecting the metal casing of the electrical installation 1 with ground electrode.

Rice. 3. Protective grounding diagram:

1 - electrical installation; 2 - grounding conductor; 3 - ground electrode

The set of grounding conductor and grounding wires is called grounding device. Protective grounding is used in three-phase three-wire and single-phase two-wire AC networks with voltages up to 1000 V with an isolated neutral, as well as in networks with voltages above 1000 V AC and DC with any neutral mode.

Protective effect of the grounding device based on reducing to a safe value the current passing through a person at the moment of contact them of a damaged electrical installation.

When voltage enters the body of an electrical installation, a person, touching it and having good contact with the ground, closes the electrical circuit: phase L1 - electrical installation housing 1 - man - earth - capacitive X L3 , X L2 and active R L 3 , R L 2 connection resistance of wires to ground, phases L3 andL2. A current will flow through the person. Despite the fact that the electrical wires of the network are installed on insulated supports, there is an electrical connection between them and the ground. It occurs due to imperfect insulation of wires, supports, etc. and the presence of capacitance between the wires and the ground. With a long distance of wires, this connection becomes significant, and its active R and capacitive X resistance decreases and becomes commensurate with the resistance of the human body. That is why, despite the absence of a visible connection, a person who is energized and in contact with the ground completes an electrical circuit between the different phases of the network.

In the presence of a grounding device, an additional circuit is formed: phase L1- electrical installation housing - grounding device - ground - resistance X L3 , R L3 , X L2 , R L2 - phases L3 And L2. As a result, the fault current is distributed between the grounding device and the person. Since the grounding resistance (it should be no more than 10 Ohms) is many times less human resistance (1000 Ohm), then a small current will pass through the human body without causing damage. The main part of the current will flow through the circuit through the ground electrode.

Grounding switches can be natural or artificial. As natural ground electrodes use metal structures and fittings of buildings and structures that have a good connection to the ground, water supply, sewer and other pipelines laid in the ground (with the exception of pipelines of flammable liquids, flammable and explosive gases and pipelines coated with insulation for protection against corrosion).

As artificial Grounding electrodes use single or grouped metal electrodes driven vertically or laid horizontally into the ground. Electrodes are made from sections of metal pipes with a diameter of at least 32 mm and a wall thickness of at least 3.5 mm, angle steel with a flange thickness of at least 4 mm, strips with a cross-section of at least 100 mm 2, as well as from sections of channels, bar steel with a diameter of at least 10 mm . Electrodes made of thinner profiles quickly fail due to corrosion. In addition, thin profiles have little contact with the ground, so their use is undesirable. The length of the electrodes and the distance between them is taken to be at least 2.5–3.0 m.

The vertical electrodes in the group grounding system are connected to each other by welding with a jumper made of similar materials and the same sections as the electrodes themselves. The grounding device must have an outlet to the outside (to the surface of the earth), welded from the same materials. It serves to connect the grounding conductor.

To perform grounding functionsgrounding device resistance in electrical installations with voltage up to 1000 Vin a network with an isolated neutral there should be no more than 4 ohms.

The required resistance is achieved by installing the appropriate number of electrodes in the ground electrode, determined by calculation.

Grounding device resistance- this is the ratio of the voltage on the grounding device to the current flowing from the ground electrode into the ground. Distinguish remote And contour grounding devices.

Remote the device is located outside the site with grounded equipment. Its advantage is the ability to select soil with the lowest resistivity.

Contour Grounding is performed by driving electrodes along the contour of the grounded equipment and between it. This installation of electrodes creates an additional protective effect by increasing and leveling (more uniform distribution) of the earth potentials in the area where a person is located.

Zeroing - This is a deliberate electrical connection of metal non-current-carrying parts of electrical installations that may be energized with a solidly grounded neutral of a current source (generator or transformer).

In four-wire networks with a neutral wire and a solidly grounded neutral of a current source with a voltage of up to 1000 V, grounding is the main means of protection.

Connection of electrical installation housings to the neutral of the current source is carried out using zero protective conductor (RE- conductor). It should not be confused with zero worker wire (N - conductor), which is also connected to the source neutral, but serves to power single-phase electrical installations. The neutral protective conductor is laid along the route of the phase wires, in close proximity to them.

Protective effect of zeroing based to reduce to a safe value the current passing through a person at the moment of contact them damaged electrical installation, and subsequent disconnection of this installation from the network.

Zeroing works as follows: when voltage comes into contact with the body of a neutralized electrical installation 8 (Fig. 4) most of the current from it will go into the network through the neutral protective wire 6. Along the circuit: electrical installation housing 8 - man - earth - grounding device 9 - neutral working wire 5 - an insignificant current will flow that does not cause damage (due to the higher resistance of this circuit compared to the resistance of the circuit through the neutral protective wire 6). At the same time, a short circuit to the phase wire body with such a protection scheme automatically turns into a single-phase short circuit between the phase and neutral working wires 5 network, as a result in 0.2-7 s current protection is triggered(fuse blows 7, a circuit breaker is tripped, etc.), and the electrical installation, and with it the person, is completely de-energized.

Thus, at the initial moment, grounding works similarly to protective grounding, and subsequently it completely stops the effect of current on a person. Only in this case, the current passing through the human body before the protection is triggered will be several times less, because The resistance of the grounding conductor usually does not exceed 0.3 Ohm, and the resistance of the grounding conductor is allowed up to 4 Ohms.

Rice. 4. Zeroing circuit:

1 - transformer neutral grounding conductor; 2 - current source (transformer); 3 - neutral of the current source; 4 - grounding of the transformer housing; 5 - zero working (also zero protective) wire of the network; 6 - neutral protective conductor of the electrical installation; 7 - fuse; 8 - electrical installation; 9 - re-grounding of the neutral protective wire of the network

In neutralized electrical installations up to 1 kV with a solidly grounded neutral in order to reliably ensure automatic shutdown emergency section, the conductivity of phase and neutral protective conductors and their connections must provide a short-circuit current exceeding at least 3 times the rated current of the fuse element of the nearest fuse or circuit breaker having a release with an inverse current characteristic (thermal release), 1.4 times - for circuit breakers With electromagnetic releases with force rated current up to 100 A and 1.25 times - with a current value of more than 100 A.

IN nullified in electrical installations up to 1 kV with a solidly grounded neutral (in order to reliably ensure automatic shutdown of the emergency section), the conductivity of phase and neutral protective conductors and their connections must ensure short circuit current.

Neutral protective conductor 5 network (Fig. 4) must ensure a reliable connection of electrical installation housings with the source neutral, therefore all connections are made welded. It is prohibited to install fuses and switches in it (except for the case of simultaneous disconnection of phase wires).

Zero protective the wire 5 networks ground: at the current source using ground electrode 1; at the ends of overhead lines (or branches from them) longer than 200 m; as well as on inputs overhead line to electrical installations. Repeated groundings 9 necessary to reduce the risk of electric shock when the neutral wire breaks and a phase is shorted to the electrical installation body beyond the break point, as well as to reduce the voltage on the body at the moment of operation current protection.

According to the PUEgrounding device resistance, to which the neutral of the current source is connected, taking into account natural and repeated grounding of the neutral wire there should be no more 2, 4 and 8 ohms respectively, at linear voltages of a three-phase current source 660, 380 and 220 V.

Total resistance spreading of grounding conductors (including natural ones) of all repeated grounding The PEN conductor of each overhead line at any time of the year must be no more than 5, 10 and 20 ohms respectively at linear voltages 660, 380 and 220 V three-phase power supply or380, 220 and 127 V single-phase current sources. Wherein grounding conductor spreading resistance each of the repeated groundings should be no more than 15, 30 and 60 Ohms, respectively, at the same voltages.

With earth resistivity ρ O > 100 Ohm∙m it is allowed to increase the specified standards by 0.01 ρ O times, but not more than ten times.

Zeroing (grounding) of metal housings of portable electrical installations is carried out by the third conductor for single-phase or fourth conductor for three-phase electrical receivers, located in the same shell with phase wires.

The cores of these wires must be flexible, copper, their section must be equal to the cross-section of the phase conductors and be no less 1.5 mm 2 .

Plug-in connectors (plugs and sockets) must be made so that the connection of the grounding and neutral protective conductors occurs before the connection of the phase conductors, and the disconnection occurs in the reverse order. This is usually achieved by using a longer pin on the plug for the protective conductor than for the phase conductors. In all cases, the plug is connected to the electrical receiver, the socket to the network.

Individual protection meansfrom electric shock

Individual protection means from electric shock - electrical protective environmentsstva (EZS), which are divided into basic and additional.

Basic EZS- these are protective equipment, the insulation of which can withstand the operating voltage of electrical installations for a long time, which allows them to be used to touch live parts that are energized.

For work on electrical installations up to 1000 V These include: insulating rods, insulating and electrical clamps, dielectric gloves,plumbing and assembly tools with insulated handles, voltage indicators.

At electrical installation voltage over 1000 V fixed assets include insulating pantsgi, insulating and electrical clamps, pointers toyarn.

Additional EZS- these are protective equipment whose insulation cannot withstand the operating voltage of electrical installations for a long time. They are used to protect against touch and step voltages, and when working under voltage exclusively with the main electrical protection devices.

These include: under tension before 1000 V - dielectric galoshes, floor insulating matsrates; over 1000 V - dielectric gloves, boots, kovricks, insulating stands.EZS must be marked indicating the voltage for which they are designed, their insulating properties are subject to periodic testing within the time limits established by regulations.

Test periods for protective equipment against electric shock are presented in Table 2.

table 2

Time limits for testing protective equipment against electric shock (fragment)

The main condition safe operation electrical installations is a choice correct scheme protection against accidental exposure of high potential to metal parts not used for energy transmission (cases, frames, etc.). To solve this problem, the requirements of current standards (PUE, in particular) provide for the use of special protective devices called grounding devices - GD. They are installed in close proximity to the protected structure and have the appearance shown in the figure below.

The process of arranging structures that protect structures and people from electric shock or lightning is commonly called grounding in electrical engineering. In order to have a complete and clear understanding of what such grounding is, you will need to investigate it distinctive features and principles of organization in more detail.

The essence of grounding

Grounding refers to the intentional connection of metal parts of electrical installations and other equipment, in this moment not energized, with elements of special devices called grounding electrodes. The design of the latter usually consists of several steel pins driven into the ground or pieces of reinforcement welded together by strips of the same metal.

Complete with a set of flexible copper wires and thick strips (busbars), the grounding conductors form the so-called “grounding loop”, to which the housings of all electrical appliances available at the site and in need of protection are connected. Since the circuit itself is partially or completely immersed in the ground and has almost perfect contact with it, its potential is normal conditions is close to zero, which allows us to draw the following conclusions:

• When hit high voltage on metal parts of a protected object or device, its value will immediately decrease to a level safe for humans (photo below);

• If a person or animal accidentally touches the housing of emergency, but thus protected equipment, they will practically not suffer from high voltage;
• In a situation where a sensitive device is installed in the supply line that responds to third-party leakage currents (RCD, for example), when dangerous voltage appears, it will operate and instantly disconnect this section from the power source.

This is the essence of the grounding effect, which should not be confused with another protection technique often used in electrical engineering, called grounding.

The concept of zeroing

Every user inexperienced in electrical terms may have a question: what is the difference between grounding and grounding, and also when is the latter used?

To understand the difference between grounding and grounding, it is necessary to consider the principle of protecting equipment of distribution substations, the essence of which boils down to the following:

• Equipment of any power stations, including the step-down transformers installed on them, has a zero point or neutral;
• In accordance with the requirements of the PUE, this point must be connected to a local charger located directly on the territory of the substation;
• Grounding is carried out in the form of a direct connection with the ground, as a result of which such a point is called solidly grounded;
• The effect of this grounding applies to all consumers connected to this electrical substation through an extensive power supply system.

Thus, the so-called “zero protective” conductor, already tightly grounded on the substation side, is supplied to each consumer along with the phase wires (see photo).

Note! IN modern systems power supply (TN-C-S, for example), it is laid separately from the working bus N with a PE wire.

When grounding the receiving equipment, its metal parts are deliberately connected not to the charger (as is done when grounding), but to the combined neutral wire that is part of the power supply system. IN TN-C-S system they are connected to a separate PE conductor.

Zeroing ensures a reduction in the risk of electric shock when accidentally touching open metal parts equipment that became energized as a result of an accident. When questions like “what is the difference between grounding and grounding” arise, you should always remember that the first guarantees automatic disconnection of the damaged line from the supply network, while the second does not.

Differences between grounding and grounding

Users often wonder whether it is possible to ground instead of grounding, and how this will affect consumer safety. When answering all such questions, one should proceed from the definition given to this type of protection in previous section. It follows from this that functionally zeroing is more effective, since in a short period of time before the station automation is triggered, it performs the same function as a conventional memory.

However, this does not mean that this type protection must be applied always and everywhere. The fact is that zeroing has a number of disadvantages that are a consequence of the peculiarities of its organization. They appear as follows:

• The neutral wire of power supply systems is long and is constantly used in active mode (as a conductor through which operating current flows), as a result of which it can collapse over time;

Additional Information. This phenomenon in the technical literature, as well as among specialists, is most often referred to as “zero burnout” (see photo below).

• Unlike grounding, the arrangement of which does not depend on the phase of the protected line, when grounding, certain conditions for connecting the protective conductor must be observed;
• It is limited in its capabilities, since it can only be used in circuits with a tightly grounded neutral in networks TN-C-S, TN-C, TN-S (if there are N, PE, PEN conductors).

In lines where the connection is organized according to a scheme with an isolated neutral (in IT and TT systems), its purpose is more suitable for industrial facilities, it will not be able to work.

Also, these two types of intentional protection differ in their scope, namely:

• Grounding is usually used in multi-storey residential buildings, where it is almost impossible to organize full grounding;
• Re-grounding is more often used on industrial enterprises where, according to TB, increased requirements are imposed on personnel safety;
• This same type of protection is most often used in everyday life (in country houses, in particular), where there are plenty of opportunities for arranging a protective circuit (see photo below).

It should be added that protective grounding and grounding differ in one more important factor. The fact is that in the first case, protection extends only to the area electrical circuit, in which, in emergency mode (during an insulation breakdown), the operating voltage decreased due to current flowing into the ground. At the same time, the rest of the electricity supply system continues to function.

Unlike the grounding effect, when grounded, this section of the power line is completely turned off.

So trying to answer the question of what their difference is will not be entirely correct. It is much more correct to say that grounding and grounding of electrical installations should be used together. Such combined use will provide more effective protection from electric shock.

To summarize their comparison, we note that the principle of zeroing is the transformation emergency situation V single-phase fault, leading to the operation of the station protective automatics. Grounding, on the one hand, represents a reduction in the potential of a dangerous point (reducing the resistance of the ground electrode), and on the other, their equalization.

In this case, it consists in raising the potential of the support with the person standing on it to the voltage level on the grounded body.

Additional items

Both in the case of grounding and grounding for implementation protective functions additional conductors must be used ( copper wires), providing a reliable connection to the memory or zero contact, respectively.

In the first case, this conductor is stretched from the protected point to the grounding contact and is made in the form of a copper braid. In the situation with zeroing the same copper conductor it is laid through hidden places in rooms and other buildings to the distribution cabinet, where its end is fixed on the main grounding bus (GZSh). The neutral working conductor, which is part of the power cable supplying electricity, is also inserted here.

Important! According to the requirements of the organization of grounding (see PUE), the use of one bolt or terminal contact to fasten these two conductors is unacceptable, which is explained by their different operating modes.

At the end of the comparison of two methods of protecting objects from electric shock, the following should be noted. Both of these methods (both grounding and grounding) essentially perform the same function, which is to reduce the dangerous potential to an acceptable level. Whether you lost some point of equipment or protected it with a memory, the effect will be approximately the same.

Video

A prerequisite for the safe operation of electrical appliances and various equipment is high-quality grounding and grounding. This work is carried out independently, which avoids equipment failure due to overvoltage and short circuits in the network. Grounding and grounding of electrical installations is carried out taking into account the characteristics of the equipment, which will prevent its premature failure.

Definition of concepts

Grounding is usually understood as the use of special structures that connect the electrical wiring of a house or individual devices to the ground. Thanks to the presence of such protection, touching surfaces that are energized will not lead to death, and the electric shock will be minimal. Protection is manufactured with electrical equipment having an insulated neutral. Grounding devices can be made of a whole group of conductors connecting current-carrying elements to the ground.

Grounding electrical equipment also increases emergency short circuit currents, which is necessary in cases where the existing protection is triggered when non-current-carrying parts become energized. This allows you to prevent equipment failure due to short circuits, unqualified repairs and interference in the electrical network. Today it is customary to distinguish several types of grounding:

• the working type ensures uninterrupted operation of electrical equipment in normal and emergency modes;
• protective type ensures the safety of electrical installations, preventing breakdowns on the housing and work surface live wires;
• The lightning protection type diverts lightning from buildings, discharging the discharge into the ground, preventing damage to electrical equipment and fires in buildings.

It is also customary to distinguish between artificially manufactured and natural grounding. The first is carried out to protect structures and electrical appliances from high voltage. Such devices consist of a metal rod, wire, substandard pipes and steel angle devices. Natural grounding also made by man, but it was not originally intended for protection against overvoltage. It can be considered as reinforced concrete structures, pipelines, casing, etc.

Zeroing also provides necessary protection electrical equipment, preventing its failure due to short circuits and overvoltage in the network. This type of work differs from grounding in terms of installation principle and purpose. Grounding involves connecting conductive elements to the body of an electrical appliance or metal parts. To ensure safety, a connection to the neutral, which is a source of three-phase reduced voltage, is required.

The main task of grounding is to protect electrical equipment and working personnel from electric shock due to the operation of automatic switching equipment. The principle of operation of such protection is to create artificial short circuits when current enters the equipment body or in cases of insulation breakdown. The occurrence of a short circuit triggers:

• fuses;
• circuit breakers;
• special short circuit protection.

Grounding differs from grounding by the use of special equipment that uses a neutral and, due to short circuits, breaks the circuit, preventing serious electric shock. A feature of grounding is the need for high current power in the neutral wire, due to which a short circuit occurs. Only in this case can a 100% probability of protection against electric shock be ensured if there are problems in the power supply. If the power of the neutral wire and the short circuit currents are insufficient, this leads to increased voltage in the electrical equipment.

Technology selection

When planning electrical protection at home, many of us think about implementing additional protection electricity supply However, homeowners do not always understand the difference between grounding and grounding. The main differences are:

• when grounding, excess current is diverted into the ground, and when zeroing is performed, the voltage in the panel is reset to zero;
• grounding is considered the most effective way protecting people from electric shock.

Grounding is easier to do than grounding. In the latter case, you will need the help of a specialist who must calculate optimal performance zero current and only then can the correct operation of the protective equipment be ensured.

Owners of private houses most often resort to grounding, but owners of apartments in high-rise buildings need to do grounding, for which they additionally install RCDs and similar devices that prevent electric shock and damage to operating electrical appliances. At correct device protection can completely eliminate the risk of electric shock, and various techniques and the devices will be completely protected from possible power surges and short circuits in the network.

To ensure high-quality protection during grounding, it is necessary to take into account the phase phase of the devices and carry out complex calculations. It is not possible to carry out such work independently. Only an experienced electrician will correctly plan the connection and install the appropriate protective devices and will carry out high-quality zeroing.

The completed grounding will not depend on the difference in devices, so it is easier to arrange it yourself, even without any professional skills. Dumping excess voltage into the ground is much safer than installing additional devices that divert current to the panel.

Available for sale today ready-made kits for grounding a private house. You only need to bury the metal circuit a few meters into the ground and connect the phase from the panel to it, which will ensure maximum safety for the electrical appliances used. You can select various kits that are suitable for a summer house or a full-size private house, differing in their design, connection method and maximum possible load.

IN last years There is a trend when full zeroing is carried out in production and enterprises where it is necessary to ensure increased electrical safety of the devices in use and industrial equipment. Ordinary homeowners, in order to protect against electric shock, install simple grounding, which is not difficult to do yourself.

Types of protective systems

The basic requirements for grounding and grounding are described in GOST, which simplifies the performance of such work and standardizes the devices used. Protective systems differ in the method of arrangement, operating principle and additional equipment used.

The TN-C system was developed in Germany at the beginning of the last century. Such protection involves the use of a single cable with a PE conductor and a neutral wire. The disadvantage of this grounding system is the appearance of excess voltage when the equipment casing is damaged and the zero burns out. Despite its shortcomings, TN-C is popular today due to its ease of implementation.

The TN-S and TN-C-S grounding systems use two wires that extend from the panel and go into the ground. The contour is made in the form of a complex metal structure, which completely eliminates the possibility of electric shock and failure of electrical appliances if there are problems with the power supply. This scheme turned out to be extremely successful; it is popular and is being installed in dachas and private homes.

Grounding type TT is based on the connection of the electrical installation circuit with metal elements located underground. This scheme is not widely used today due to the complexity of implementation, as well as possible voltage drops in the network.

A type of OT protection involves transferring excess voltage to the housing and to the ground from the neutral, which is isolated from the ground and connected to devices with high resistance. This scheme has become widespread when used electrical equipment, which requires stability and increased security.

Popular methods of zeroing

PNG nulling is simple in design, which is explained by the combination of protective and neutral conductors. The disadvantages of this safety system include increased requirements for the interaction of the conductor cross-section of its potentials. PNG is widely used when it is necessary to ground asynchronous units operating in three-phase networks.

The most popular today are modified systems for grounding electrical installations, which are powered by a single-phase network. They use a common combined PEN conductor connected to a solidly grounded neutral. After this connection, the PE and N cables are separated, which are then connected to the housing or similar protection devices. The advantage of this grounding technology is its versatility, the ability to be used in single-phase and three-phase networks, as well as simplicity of design and complete safety.

Grounding and grounding of electrical installations allows you to protect equipment from power surges and short circuits. Zeroing involves the use of special equipment that allows you to redirect excess voltage to the shield. Such protection is used primarily in industrial enterprises and facilities where increased safety of equipment operation is required. Owners of private houses can carry out grounding themselves, which will allow them to protect themselves and the electrical appliances they use from short circuits and surges in the network.

The operating principle of grounding is based on the occurrence of a short circuit during phase breakdown to a non-current-carrying part of an instrument or device, which leads to the activation of the protection system (circuit breaker or blown fuses).

Grounding is the main measure of protection against indirect contact in electrical installations up to 1 kV with a solidly grounded neutral. Since the neutral is grounded, grounding can be considered a specific type of grounding.

In 380/220 V networks, grounding of neutrals (zero points) of transformers or generators is used in accordance with.

Let us first consider a 380 V network with a grounded neutral. Such a network is shown in Fig. 1.

If a person touches the conductor of this network, then under the influence phase voltage a damage chain is formed, which closes through the human body, shoes, floor, ground, neutral grounding (see arrows). The same circuit is formed if a person touches a housing with damaged insulation. However, it is impossible to simply ground the body of the electrical receiver.

Rice. 1. Touching a conductor in a network with a grounded neutral

Rice. 2. Grounding the electrical receiver in a network with a grounded neutral

To understand this, let’s assume that such grounding has been completed (Fig. 2) and a short circuit to the motor housing has occurred in the installation. The short circuit current will flow through two grounding conductors - the electrical receiver Rз and the neutral Ro (see arrows).

Rice. 3. Grounding an electrical receiver in a network with a grounded neutral

For this reason, in installations with a grounded neutral voltage of 380/220 V, a different type of grounding system is used: all metal cases and the structures are electrically connected to the grounded neutral of the transformer through the neutral wire of the network or a special neutral conductor (Fig. 3). Thanks to this, any short circuit to the housing turns into a short circuit, and the emergency section is turned off by a fuse or circuit breaker. This grounding system is called grounding.

Thus, ensuring safety during grounding is achieved by disconnecting the section of the network in which a short circuit to the housing occurred.

The protective effect of grounding consists in automatically disconnecting the section of the circuit with damaged insulation and at the same time reducing the potential of the housing for the time from the moment of closure to the moment of disconnection. After a person touches the body of an electrical receiver that has not switched off for any reason, a current branch will appear in the circuit through the person’s body.

In addition, if an RCD is installed in this line, then it also trips, but not from a large current, but because the current is phase wire becomes unequal to the current strength in the neutral working wire, since most of current takes place in the protective grounding circuit past the RCD. If both an RCD and a circuit breaker are installed on this line, then either both of them will work, or one or the other, depending on their speed and the magnitude of the fault current.

Just as not every grounding provides safety, not every grounding is suitable for ensuring safety. Grounding must be carried out so that the short circuit current in the emergency section reaches a value sufficient to melt the fuse link of the nearest fuse or turn off the machine. To do this, the resistance of the short circuit must be sufficiently small.

If the shutdown does not occur, then the short circuit current will flow through the circuit for a long time and in relation to the ground, voltage will arise not only on the damaged case, but also on all grounded cases (since they are electrically connected). This voltage is equal in magnitude to the product of the fault current and the resistance of the neutral wire of the network or the neutral conductor and can be significant in magnitude and, therefore, dangerous, especially in places where there is no potential equalization. To prevent such a danger, it is necessary to carefully carry out PUE requirements to the zeroing device.

The protective effect of grounding is ensured by the reliable operation of maximum current protection to quickly disconnect a section of the network with damaged insulation. The time for automatic shutdown of a damaged line for a 220/380V network should not exceed 0.4 s.

To do this, it is necessary that the short circuit current in the phase-zero circuit meets the condition Ik >k Inom, where k is the reliability coefficient, Inom is the rated current of the setting of the disconnecting device (fuse, automatic ic switch).

The reliability factor k according to the PUE must be no less than: 3 - for fuses or circuit breakers with a thermal release ( thermal relay) For normal premises and 4 - 6 - for explosive premises, 1.4 - for automatic ical switches with electromagnetic release in all rooms.

Spreading resistance of the neutral grounding device Ro ( working grounding) should be no more than 2, 4 and 8 Ohms, respectively, at rated voltages 660, 380 and 220 V three-phase electrical installations.