Grounding and zeroing: what is the difference in terms of security level. Protective grounding: device, purpose, principle of operation. What is dangerous zeroing in an apartment Zeroing what is dangerous
Even professional electricians get confused in the purpose and installation of these methods of protection against electric shock. This is not about everyone, but there are precedents. But the elementary concept of terms sometimes saves dozens of lives. Even if we are not talking about electric shock, but about commissioning a new private house. If the protection is not performed correctly, the controlling organization will not allow the supply of voltage to the input shield. And rightly so, no one wants to take responsibility for people's lives. Today we will figure out what the terms and zeroing mean, what is the difference between them, and when it is possible to use one or another method of protection.
In accordance with GOST 12.1.009–76:
- protective earth- this is an intentional electrical connection to earth or its equivalent of metal non-current-carrying parts that may be energized;
- nulling- this is a deliberate electrical connection with a zero protective conductor of metal non-current-carrying parts that may be energized.
In 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.
According to the PUE, grounding is carried out (if there is a circuit or the possibility of its installation) without fail. All metal cases should be grounded, which hypothetically can become energized. If there is no possibility of grounding, protective grounding is carried out with the mandatory installation of residual current devices (RCD) and automatic ones in the input electrical.
Of course, the language in which the PUE and GOST are written can be difficult for a person without an electrical engineering education, which means it is worth analyzing in detail what grounding and zeroing are in a common language understandable to a simple layman.
What is grounding: how it works, the principle of operation and the advantages of such protection
The principle of operation of grounding is to prevent the passage of electric current through the human body if, due to any circumstances, the body becomes energized. This can happen if the insulation of the cable cores is damaged. Consider an example. A core with damaged insulation is in contact with a metal case. The hostess, while preparing food in the kitchen, touches the one that is not grounded. This causes the current to rush to earth, using the human body as a conductor. The result can be the most deplorable, even fatal.
Now let's look at what grounding is for, how it works. The same example, but with the use of protection. Grounding requirements are the most stringent. When measuring, the resistance of the circuit should be practically absent, which allows the current to freely go to the ground through the bus. The laws of physics prevent voltage from flowing through the human body, which has its own resistance. Some have it more, others less, but its presence is not disputed. It turns out that the current flows along the path of least resistance, through the ground electrode. If at the same time an RCD is included in the circuit, it will detect a leak and turn off the power supply to the device.
What is the zeroing of electrical appliances: application possibilities
Protective grounding of electrical appliances is used if it is impossible to install grounding. This situation may arise if the apartment building was built in Soviet times. Such houses do not have their own contour, and it will not be possible to arrange it on their own.
Protective grounding is a system that performs a job other than grounding. If the second is designed to divert voltage to the ground, excluding the possibility of electric shock, then the first is performed in order to create (in the event of a breakdown of the insulation and contact with the case) a short circuit. In this case, the automation is activated and the electricity is turned off.
Important information! In multi-apartment buildings of modern construction and private sectors, installation of zeroing is prohibited today. This is for the safety of residents. Automation can fail, which will lead to irreparable consequences.
Protective grounding requires proper installation. You should not think that it is enough to throw a jumper from the zero contact inside to the ground one. This is strictly prohibited. Consider a situation where an already "burnt" zero is subjected to a short circuit load, and the machine has not yet had time to work. Zero burns out, eliminating the short circuit, but the device remains energized. A person, hoping for a lack of electricity (there is no light, zero has burnt out), moves towards the exit by touch and leans on the energized body. The outcome is clear, isn't it?
Zeroing and grounding: what is the difference
The difference between these systems is in the method of protection. With a protective grounding device, the role of a voltage cut-off in the event of an emergency is assumed by the RCD, and in the case of installation of the zeroing, the RCD becomes powerless, only the machine can work. Why is this happening? The residual current device reacts only to current leakage, completely ignoring any overloads, including short circuits. In the case of installation of zeroing and inclusion in the RCD circuit without a machine, in the event of a short circuit, the RCD does not work, but simply burns out without turning off the voltage from the line.
What is the difference between grounding and grounding: generalization
Grounding differs from zeroing in the way of protection and installation. Such systems contradict each other, which means that the installation of the circuit with the inclusion of both options is unacceptable. Zeroing is arranged only in apartment buildings that are not equipped with their own circuit. Otherwise, such installation is prohibited. We will now talk in more detail about the methods of its device.
What is zeroing and how to arrange it correctly
The installation scheme is as follows. The neutral that has come to the introductory machine is bifurcated, each of the cores goes to a separate bus. One of the buses becomes zero, and the second is grounding. From the neutral bus, the wires go through the automation and further to all the zero contacts of the consumers of the apartment. The grounding one is connected to the body of the input shield, the yellow-green wire from it goes to the corresponding socket contacts and that require it. Contact of the ground wire with zero after protective automation is prohibited.
Important information! Incorrect installation of protective earthing leads to burnout of cable cores, fire. It is also possible electric shock up to death.
The best protection option is a grounding device?
The only correct answer to this question is yes. It really is. , mounted in accordance with all the rules, will protect a person much better than the previous version. You can improve protection with the help of additional devices - circuit breakers, RCDs or difavtomatov. After all, what is protective grounding? At its core, this is a system for diverting electric current in the event of an accident to where it cannot harm a person.
With regard to the grounding device, we can say that it can be different - a ground loop around the perimeter of the building, a "triangle" in the yard or a natural ground electrode. We will definitely consider all the rules and methods of its installation in one of the nearest topics. But for general information, it makes sense to understand the definition of what is a natural ground electrode.
Good to know! Any underground metal structures can be used as a natural grounding conductor, with the exception of fuel and lubricants pipelines, sewerage and objects coated with anti-corrosion compounds. Water pipes for this purpose can be used.
Advantages and disadvantages of apartment grounding
A lot has been said today about the shortcomings of such protection. Let's try to summarize the information. With this method, you cannot be 100% sure of your protection. Especially if the installation is done incorrectly. Another disadvantage is that if the contact is weak or the cable is damaged, the machine simply will not have time to work. As a result, the wire will burn out, which will require repair.
And finally, an interesting and informative video on the topic of our conversation today.
In all residential buildings, grounding or zeroing is used to protect against the effects of electric current. In some cases, the electrical panel is grounded and, at the same time, the neutral core of the main cable is connected to the same shield. However, the question often arises whether grounding can be used instead of grounding, and vice versa.
Grounding and zeroing schemes
These protection schemes must be applied very carefully. First of all, this is due to the uneven distribution of loads on the phases. With the same load on each, a small current will flow through the common neutral wire. However, if only one of the three phases is loaded, then the current value in the neutral wire will be the same as in this phase.
In residential buildings, zeroing is not recommended. As a rule, zero cores have a smaller cross section than phase lines. The neutral wire very often remains uncontrolled, its connection gradually weakens, oxidation occurs. When it gets too hot, it just burns out. In this situation, a direct hit of the phase on the shield occurs. Through grounding, current enters the apartment and disables all grounded equipment. Household appliances are energized, as a result, the likelihood of electric shock increases.
Thus, it is undesirable to use zeroing in residential buildings. Usually, it is used in industrial enterprises, where the load distribution of the phases is more uniform, and the neutral wire performs the function of protection.
What is nulling
If almost everyone knows about grounding, then many have a very vague idea about grounding. Nevertheless, it is used quite often and for proper operation, you need to know its structure and principle of operation.
In electrical engineering, grounding is the connection of the neutral wire of the electrical network to the body of the device, equipment and other consumers. Unlike grounding, which protects people, grounding primarily protects equipment. Therefore, talking about zeroing instead of grounding is not entirely correct. Each scheme is designed for use in a specific area. When protecting equipment, grounding artificially creates a short circuit situation in which the circuit breaker trips.
For stable and reliable zeroing operation, it can be grounded separately. Thus, the efficiency of the entire protective system is increased, especially when the neutral wire fails.
Hello, friends!
In this article, we will talk about what zeroing is, where it is applied, as well as the main mistakes in its construction. The topic is not easy, there are constant debates on the forums.
It is interesting that often even electricians cannot correctly say how grounding differs from grounding. Let's figure it out. To begin with, let's see what the PUE says about zeroing.
Zeroing in electrical installations with voltages up to 1 kV is the deliberate connection of parts of an electrical installation that are not normally energized with a solidly grounded neutral of a generator or transformer in three-phase current networks, with a solidly grounded output of a single-phase current source, with a solidly grounded midpoint of the source in DC networks
Simply put, zeroing is the connection of the body of an electrical device with a neutral wire.
Now let's see what the PUE tells us about grounding
The grounding of any part of an electrical installation or other installation is the intentional electrical connection of this part with a grounding device.
In simple words, grounding is the connection of the body of an electrical device with a ground electrode. A grounding conductor is a structure made of metal pins driven into the ground.
Now let's see how the most common power supply systems for apartment buildings are arranged.
Both schemes use a combined PEN neutral conductor, which is grounded at a transformer substation.
The main difference between them is that in TN-C-S the combined conductor is divided into a working zero and a protective conductor. This is done in the introductory common house shield (ASU). In this case, it is necessary to re-ground.
If you look closely at the diagrams, it becomes clear that the working zero is always connected to the ground, that is, grounded. And the question arises: what, in fact, is the difference between grounding and grounding? After all, by connecting the body of the device to the working zero, we actually connect it to the ground.
Actually, there is a difference. It is based on the principle of action.
Grounding is designed to carry current to ground. This reduces dangerous voltage on the housing of the device or device.
Zeroing is intended to create the effect of a short circuit in the event of a phase breakdown on the case. At the same time, the machine is activated and disconnects the emergency line.
Thus, zeroing and grounding in TN systems work simultaneously, so to speak, in one bottle. Therefore, the 3rd protective contact in euro sockets in TN systems is both grounding and zeroing.
Based on this, it is correct to talk about the combined conductor PEN, the working neutral conductor N and the protective conductor PE. At the same time, even electricians do not always understand the difference between PE and N, but it is very significant.
Usually, when some “electrician Uncle Vasya” talks about zeroing, he means all sorts of collective farms such as jumpers in sockets and the like connecting a protective wire to zero. And it's dangerous.
Incorrect zeroing can instead of protection cause a tragedy .. And such pseudo-protection occurs very, very often.
Let's figure out how protective zeroing is done correctly and what absolutely cannot be done.
Remember, the division of the combined conductor into a working zero and a protective zero should be carried out in a common house input device (ASU). And from there, the protective conductor should go to the floor boards, and from them to each apartment.
Thus, we get a five-wire riser: 3 phases, working zero and protective zero. In this case, we are not talking about the so-called grounding, since a separate protective wire comes to each apartment (TN-C-S and TN-S systems). It must be connected to the third contact of the sockets.
In old houses with non-upgraded wiring, there is usually a four-wire riser: 3 phases and a combined zero PEN (TN-C system). This is where the sheer mess and terrible jambs begin.
It all starts in the floor shield. Often it makes an independent division of PEN into PE and N.
This option has the right to life, but only subject to important rules. Here are the main ones:
Rule 1 In single-phase circuits, it is forbidden to separate the neutral wire (PUE - 1.7.132).
How to determine which network is in your house? In relatively old houses, the access risers are four-wire: three phases and one combined zero (PEN). That is, three-phase risers are used, respectively, a three-phase circuit.
In very old houses, stalinkas and Khrushchevs, a two-wire riser is often used, in which there is only a phase and a working zero. A distinctive feature of such houses is the absence of access shields. The risers go in the shafts between the apartments, and in the apartments themselves there are specific “humpbacked” shields. Here in such houses, as a rule, a single-phase network is used.
Rule 2 The combined PEN conductor must be at least 16 mm in aluminum or 10 mm in copper.
That is, the zero riser must be a section not less than the specified one. In many houses, the cross section is smaller; in this case, it is impossible to divide the combined zero into protective and working. If you have a Soviet-built house with gas stoves, then in 80% of cases the riser in it is frail.
Rule 3 Once PEN has been split into PE and N, they cannot be reconnected.
Here, I think no explanation is needed.
Rule 4 The protective conductor PE must be non-switchable.
That is, it is impossible to put automatic machines and other disconnecting devices on it.
Rule 5 It is necessary to separate PEN BEFORE all machines, knife switches, switches.
It is better to do this: take a brass bus and screw it to the shield with screws so that there is contact between them. From the zero riser through a separate nut, make a tap to this bus. Connect the PE protective wires from the apartments to the busbar.
If at least one of these rules is not fulfilled, then it will not be protection, but a life-threatening collective farm.
A little more about what not to do
1) Connect the protective and neutral contacts in the socket with a jumper. This is one of the most dangerous mistakes!
In the event of a burnout, damage or accidental disconnection of zero, a dangerous phase voltage will immediately appear on the body of all devices connected to such sockets. In this case, neither the RCD nor the machine will work. Hello death.
The same effect will be with a random change in phase and zero.
2) Put the neutral and protective conductors on one screw in the shield
PE and N must be on different clamps (tires). Moreover, each wire from a separate apartment must be clamped with a separate screw.
3) Zeroing on an ungrounded (non-zeroed) shield.
Usually, all shields have direct contact with a zero or protective riser (zeroed). But sometimes there is no contact, for various reasons. For example, the connecting wire fell off. Zeroing on such a shield can lead to the appearance of dangerous voltage on its body.
In practice, this kind of jambs are found all the time, in various variants and combinations. I can advise you not to be too lazy, to study the PUE, and also not to trust your wiring to dubious personalities.
Thus, it is undesirable to use zeroing in residential buildings. Usually, it is used in industrial enterprises, where the load distribution of the phases is more uniform, and the neutral wire performs the function of protection.
What is nulling
If almost everyone knows about grounding, then many have a very vague idea about grounding. Nevertheless, it is used quite often and for proper operation, you need to know its device and principle of operation.
In electrical engineering, grounding is the connection of the neutral wire of the electrical network to the body of the device, equipment and other consumers. Unlike grounding, which protects people, grounding primarily protects equipment. Therefore, talking about zeroing instead of grounding is not entirely correct. Each scheme is designed for use in a specific area. When protecting equipment, grounding artificially creates a short circuit situation in which the circuit breaker trips.
For stable and reliable zeroing operation, it can be grounded separately. Thus, the efficiency of the entire protective system increases, especially when the neutral wire fails.
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WITH With the advent of electricity in everyday life, the question of its safe use also arose. Let's see how to solve this important task, let's figure out: what is zeroing, how does grounding work, how to make a zero in a private house with their 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 goes 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.
Step-down transformer substations then convert the high voltage to a much lower (but still dangerous) voltage, and it will come to our house through wires or underground cables.
The current must come to the appliance, do useful work and leave. In the case of alternating voltageused in everyday life, phase (supply) and neutral wires are used for this. Where the electric current comes from is understandable; but where does the electricity go? To the ground! Slightly simplified, but by and large it is. Right into the ground.
The substation transformer has an earth connected to a separate line wire. This is the same “zero” in ours. Particularly inquisitive people can verify this by examining an ordinary transformer substation with overhead lines. 3 wires came in, 4 came out. At the input - three phases of high voltage, at the output - three phases of low voltage and a neutral wire.
And now let's move on to the main thing - human protection.
Grounding in the apartment
The most reliable way to protect against electric shock in everyday life is with electrical appliances. Indeed, many of our home assistants have metal (read - conductive) cases, and as a result of a break or damage to the insulation, the phase wire may touch the device case. And then touching it becomes deadly...
To avoid trouble, the body of the device is connected to the ground. Now, when a phase hits the case, a short circuit occurs and a protection is activated that turns off the current supply.
In modern apartments, it is carried out according to a three-wire scheme:
Phase;
zero;
Earth.
Grounding of electrical appliances occurs through the third contact of the plug and. The situation is more complicated in houses where it is mounted according to a two-wire circuit, and there is no ground wire in the sockets. In this case, the ground wire will have to be carried out directly from the instrument case.
Where to get the "land" in the apartment of a multi-storey building? The answer is simple: in the electrical panel installed on each floor.
Before performing (it is better, of course, to do this with the participation or under the supervision of a professional electrician), carefully examine the electrical panel. After all, if there is no reliable grounding at the shield, connecting the apartment's grounding wire to it is not only in vain, but also dangerous!
Let's explain with an example. The neighbor has a short circuit. The current will go the following way: the phase of the neighbor - the "zero" of the neighbor - the storey electrical panel - your ground wire - the body of your device!
Residual current device
To improve safety in the operation of el. devices use the so-called residual current device, abbreviated - RCD. Together with RCDs, they give a 100% guarantee of protecting a person from electric shock.
Let's look at the principle of operation of the RCD, for which we present it as a plumbing system. Water flows through pipes, just like electricity flows through wires. And if suddenly a hole forms in the pipe, the water begins to leave, and its amount at the outlet of the section will be less than at the inlet. RCD controls such a leak, but not water, but electricity.
If the body of the device is energized, but there is no leakage, the RCD does not respond. But as soon as a person touches the case, a path for current leakage appears, a “hole” - the RCD opens the circuit in a split second.
Zeroing
According to the email rules. safety, zeroing is called: “…. connection of the equipment case with a zero protective conductor. Now let's reason. We have an electrical appliance (say, a washing machine) that needs to be grounded. The plug of the machine and the socket are three-pin, but the wiring is two-wire, which means that we do not have grounding. But we know that the “zero” at the substation is grounded, so why not connect the “zero” and “ground” contacts in the outlet? In no case!
Let's read the wording again: "... a zero protective conductor." That's the point! After all, the “zero” in the outlet is a working conductor, not a protective one, and it is impossible to put a jumper between ground and zero in the outlet:
A) it may cause a short circuit;
b) if the zero has poor contact, the phase through the device will go to the zero of the socket, and through the jumper and the ground wire - to the body of the device.
We read the rules further: “Grounding is designed to eliminate the danger of electric shock when shorting to the case ... in three-phase four-wire networks ....”. But in the apartment, the network is single-phase! Here in a multi-storey building, the network is three-phase four-wire, so you can perform zeroing no closer than in the switch cabinet of the house.
Consider a couple of situations
1.
When you connected the case to the neutral wire (working zero). After some time, during the repair of the shield, the phase and zero were accidentally changed. Result: you have a phase on the car body! You will receive a not dangerous, but unpleasant blow, even with an RCD, or you can be seriously injured.
2. Same connection. The motor winding overheated, and a breakdown occurred on the case. The case is energized, but the RCD does not work: there is no leakage! The winding heats up until the wires fuse, and the circuit breaker trips from the increased current. And the engine is "kirdyk", and not far from the fire!
You can think of other situations, but they are all resolved if the wiring is done according to a three-wire circuit with reliable grounding. That is, the machine is connected without grounding in the outlet, but is reliably grounded (Fig. 1).
With any phase closure to the case, an RCD or an automatic device is triggered, turning off the power.
If the wiring is two-wire, you need to run a ground wire from potentially dangerous devices with metal cases to the electrical panel, making sure that it is grounded.
In conclusion about nulling
Remember the common truth - any work with electrical networks is carried out only when the voltage is off! If the work is done under voltage, they use reliable and tested means of protection: dielectric gloves, etc. You have one life, and you should not risk it over trifles: electricity does not forgive frivolity!
As usual, we are waiting for yours! Good luck in job!
The main condition for the safe operation of electrical installations is the choice of the correct protection scheme against accidental contact with high potential on metal parts that are not used for energy transmission (housings, beds, etc.). To solve this problem, the requirements of the current standards (PUE, in particular) provide for the use of special protective devices called grounding devices - GD. They are arranged in close proximity to the protected structure and have the form 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 idea of what grounding is, it will be necessary to study its 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 that are not currently energized with elements of special devices called grounding conductors. 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), grounding conductors form the so-called "grounding loop", to which the cases of all electrical appliances available at the facility 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 under normal conditions is close to zero, which allows us to draw the following conclusions:
- If high voltage hits the metal parts of a protected object or device, its value will immediately drop to a level that is safe for humans (photo below);
- If a person or animal accidentally touches the body of an emergency, but protected in this way, 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 a dangerous voltage appears, it will work and instantly disconnect this section from the power supply.
This is the essence of the grounding effect, which should not be confused with another protection technique often used in electrical engineering, called zeroing.
The concept of nulling
Each user inexperienced in electrical terms may have a question: how does grounding differ from zeroing, and also when is the latter used?
To understand the difference between grounding and zeroing, it will be necessary to consider the principle of protecting equipment of distribution substations, the essence of which is as follows:
- The equipment of any power plants, including step-down transformers installed on them, has a zero point or neutral;
- In accordance with the requirements of the PUE, this point is necessarily connected to the local charger, equipped 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 dead-grounded;
- The action 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 grounded tightly on the side of the substation, is supplied to each consumer along with the phase wires (see photo).
Note! In modern power supply systems (TN-C-S, for example), it is laid separately from the operating busbar N with a PE wire.
When zeroing 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 a TN-C-S system, they are connected to a separate PE conductor.
Zeroing provides a reduction in the threat of electric shock in case of accidental contact with open metal parts of the equipment, which, due to an accident, become energized. When questions like “what is the difference between zeroing and grounding” arise, you should always remember that the first guarantees automatic disconnection of the damaged line from the mains, and the second does not.
Differences between grounding and grounding
Often, users wonder if it is possible to do grounding instead of grounding, and how this will affect consumer safety. Answering all such questions, one should proceed from the definition given to this type of protection in the previous section. It follows from it that functionally zeroing is more effective, since in a short period of time before the operation of station automation, it performs the same function as a conventional memory.
However, this does not mean that this type of protection should be applied always and everywhere. The fact is that zeroing has a number of shortcomings, which 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 the 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, during the arrangement of which there is no dependence on the phase of the protected line, when zeroing, 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 TN-C-S, TN-C, TN-S networks (if there are N, PE, PEN conductors).
In lines where the connection is organized according to an isolated neutral scheme (in IT and TT systems), which are more suitable for industrial facilities by their purpose, it will not be able to work.
Also, these two types of deliberate protection differ in their scope, namely:
- Zeroing is usually used in multi-storey residential buildings, where it is almost impossible to organize a full-fledged grounding;
- Re-grounding is more often used in industrial enterprises, where, according to safety standards, increased requirements are imposed on the safety of personnel;
- The 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 zeroing differ in another important factor. The fact is that in the first case, protection applies only to the section of the electrical circuit, in which, in emergency mode (during the breakdown of insulation), the operating voltage has decreased due to the current draining into the ground. At the same time, the rest of the electricity supply system continues to function.
Unlike the action of the grounding effect, when grounding, this section of the power line is turned off completely.
So trying to answer the question, what is their difference, will not be entirely correct. It is much more correct to say that grounding and grounding of electrical installations should be used together. Such a combined use of them will provide more effective protection against electric shock.
Summing up their comparison, we note that the principle of zeroing is to turn an emergency into a single-phase short circuit, leading to the operation of the station protective automation. Grounding, on the one hand, is a decrease in the potential of a dangerous point (a decrease in 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 a person standing on it to the voltage level on the grounded case.
Additional elements
Both in the case of grounding and zeroing, for the implementation of protective functions, additional conductors (copper wires) must be used to ensure a reliable connection with the charger or with a neutral contact, respectively.
In the first case, this conductor is pulled from the protected point to the ground electrode contact and is made in the form of a copper braid. In a zeroing situation, the same copper conductor is laid through hidden places in rooms and other buildings to a switch cabinet, where its end is fixed on the main ground bus (GZSH). A zero working conductor, which is part of the power cable supplying electricity, is also brought here.
Important! According to the requirements of the organization of grounding (see the PUE), the use of one bolt or terminal contact for fastening these two conductors is unacceptable, which is explained by the different modes of their operation.
At the end of the comparison of the two methods of protecting objects from electric shock, the following should be noted. Both of these methods (both zeroing and grounding), in fact, perform the same function, which consists in reducing the dangerous potential to an acceptable level. You zap some point of the equipment or protect it with the help of a memory, the effect will be about the same.
Video
Protective earthing - 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, a contact is made with a solidly grounded output of a single-phase current source, and in the case of direct current, with a solidly grounded point of the current source. Although zeroing has serious disadvantages, the system is still widely used in many areas for current protection.
The difference between zeroing and grounding
There are differences between zeroing and grounding:
- In the case of grounding, the excess current and the voltage that has appeared on the case are redirected to the ground. The principle of operation of zeroing is based on zeroing on the shield.
- Grounding is more effective in terms of protecting a person from electric shock.
- Grounding is based on a rapid and significant reduction in voltage. Nevertheless, some (already non-dangerous) tension remains.
- Zeroing consists in creating a connection between metal parts in which there is no voltage. The zeroing principle is based on the deliberate creation of a short circuit in the event of an insulation breakdown or current flow to non-current-carrying parts of electrical installations. As soon as a short circuit occurs, the circuit breaker kicks in, fuses blow, or other protections work.
- Grounding is most often used on isolated neutral lines in IT and TT systems in three-phase networks where the voltage does not exceed a thousand volts. Grounding is used at a voltage of more than a thousand volts with a neutral in any mode. Zeroing is used in dead-earthed neutrals.
- When zeroing, all elements of electrical appliances that are not under voltage in the standard mode are connected to zero. If the phase accidentally touches zeroed elements, the current increases sharply and the electrical equipment is turned off.
- Grounding does not depend on the phases of electrical appliances. For the organization of zeroing, compliance with strict connection conditions is required.
- In modern homes, 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 standards for electrical safety, the main method of protection is zeroing.
Note! For the correct determination of zero points and the choice of protection method, you will need the help of a qualified electrician. You can make grounding, assemble the elements of the circuit and install it in the ground with your own hands.
Scheme of work
As mentioned above, zeroing is based on provoking a short circuit after the phase hits the metal case 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 regulations of the Rules for the installation of electrical installations, in the event of a violation of the integrity of the line, it should 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 cable core is used.
For correct zeroing, it is important that the phase-zero loop is characterized by low resistance. This ensures that the protection is triggered for the required period of time.
The organization of grounding requires high qualifications, so only qualified electricians should perform such work.
The diagram below shows how the system works:
Application area
Protective grounding is used in electrical installations with four-wire power networks and voltages up to 1 kW in the following cases:
- in electrical installations with a solidly grounded neutral in TN-C-S, TN-C, TN-S networks 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 buildings where zeroing of electrical installations is mandatory. For residential premises with dry floors, zeroing does not need to be equipped. 
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 that are touched by workers are subject to grounding.
Zeroing efficiency test
To check how effective zeroing is, you need to measure the resistance of the phase-zero loop at the point most distant from the power source. This will make it possible to check the security in case of current exposure to the case.
Resistance is measured using specialized equipment. Measuring devices are equipped with two probes. One probe is directed to the phase, the second - to the neutral electrical installation.
Based on the measurement results, the resistance level on the phase and zero loop is set. With the result obtained, the single-phase short circuit current is calculated using Ohm's law. The calculated value of the single-phase fault current must be equal to or greater than the operating current of the protective equipment.
Assume that a circuit breaker is connected to protect the electrical circuit from overloads and short circuits. The trip current is 100 Amperes. According to the results of measurements, 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 \u003d U / R \u003d 220 Volts / 2 Ohms \u003d 110 Amperes.
Since the estimated short-circuit current exceeds the instantaneous operation of the circuit breaker, we conclude that the protective zeroing is effective. Otherwise, it would be necessary to replace the circuit breaker with a device with a lower trip current. Another solution to the problem is to reduce the resistance of the phase-to-zero loop.
Often, when carrying out calculations, the operation current of the machine is multiplied by the reliability factor (Kn) or the safety factor. The reason is that the cutoff is not always equal to the specified indicator, that is, a certain error is possible. Therefore, the use of the coefficient allows you to get a more reliable result. For old equipment, Kn is from 1.25 to 1.4. For new technology, a coefficient of 1.1 is applied, since such machines work with greater accuracy.
The danger of zeroing in the apartment
Power surges are dangerous both for people and for household appliances in apartments. In apartment buildings, one of the apartments will get low voltage, and the other - high. If a break in the neutral conductor occurs in the outlet of the apartment, the next time the electrical installation (for example, a boiler) is turned on, a person will be shocked.
Zeroing is especially dangerous in a two-wire system. For example, when carrying out electrical work, an electrician can replace the neutral conductor with a phase conductor. In electrical panels, these cores are far from always marked with a certain color. If the replacement occurs, the electrical equipment will be energized.
According to the regulations of the Rules for the installation of electrical installations at the household level, zeroing is not allowed for domestic use precisely because of its unsafety. Zeroing 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 well as possible negative consequences. Next, consider a number of situations that arise in the presence of zeroing the apartment.
Zeroing in sockets
In some cases, the protection of electrical appliances is proposed to be performed by jumpering the terminal of the socket working zero to a protective contact. Such actions contradict paragraph 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 living room, most often there is a device designed to switch phase and zero (a two-pole device or the so-called bag). Switching zero, used as a protective conductor, is not allowed. In other words, it is forbidden to use a conductor as a protection, the electrical circuit of which includes a switching device.
The danger of protection using a jumper in the socket is that the housings of electrical installations in the event of zero damage (regardless of the site) fall under phase voltage. If the neutral conductor breaks, the electrical receiver ceases to function. In this case, the wire seems to be de-energized, which provokes rash actions with all the ensuing consequences.
Note! When zero breaks, any equipment in an apartment or in a private house becomes a source of danger.
Swapped phase and zero
When carrying out electrical work in a two-wire riser with your own hands, there is a considerable likelihood of confusion between zero and phase.
In houses with a two-wire system, cable cores are devoid of distinctive features. When working with wires in a floor shield, an electrician can simply make a mistake by confusing the phase and zero in places. As a result, the housings of electrical installations will fall under phase voltage.
Zero burnout
Zero break (zero burnout) often happens in buildings with poor wiring. Most often, wiring in such houses was designed based on 2 kilowatts per unit of housing. To date, the electrical wiring in old-style houses has not only worn out physically, but is also unable to satisfy the increased number of household appliances.
In the event of a zero break, an imbalance occurs at a transformer substation, from which an apartment building is powered. Distortion is possible in the general electrical panel of the building or in the floor shield 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.
Zeroing alternative
In the TN-S subsystem, the grounding of the protective conductor PE is carried out in only one area - on the ground loop of a transformer substation or electric generator. At this point, the PEN conductor is separated, and further 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), neutralization is not used. Electrical equipment operating within the TT and IT system is grounded by its own circuits. Since the IT system assumes the supply of power only to specific consumers, it does not make sense to consider this method of organizing protection in residential buildings. The only alternative to incorrect and therefore dangerous zeroing of the PE tire is the TT system. Such a system is especially relevant, because the transition to technically advanced systems TN-S, TN-C-S is 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 the ingress of non-current-carrying parts under voltage. All work on the organization of grounding must be carried out in accordance with the standards specified in paragraph 1.7.39 of the Rules for the installation of electrical installations.
