Potential equalization system. Additional potential equalization

Potential equalization - intelligibly. Every person who studied physics at school remembers that any conductor is endowed with its own potential. By itself, the potential does not pose any danger, the difference in potentials that any metal product has is dangerous. The more significant this difference, the higher the probability of getting hit. electric shock. How is potential equalization carried out?

What is the meaning of potential equalization?

Such a phenomenon as a potential difference can be provoked large quantity various factors. Some of them look like this:

– Overvoltages in the atmosphere;

- Wandering bundles of energy;

– Static voltage;

The most dangerous is such a potential difference that occurs as a result of voltage leakage from faulty sections of electrical wiring through things made of metal or electrical household equipment. As an example, consider the following situation: a person living in high-rise building, while in his bathroom, touches a pipe made of metal and receives an electric shock. A similar situation arose due to the fact that the insulation of an electrical appliance located in another apartment is faulty. Due to faulty insulation, the potential of the metal pipe changed and the person who touched it received an electric shock.

In order to equalize the potentials of all electrical appliances that may be dangerous, they must be combined. The easiest way to perform such a manipulation is with a copper wire, combining standing side by side appliances, pipes and other objects. By creating a common circuit between pipes or between appliances, a person equalizes the potential.

However, the union of all potentially dangerous objects is not enough. For complete safety in the process of using electrical household appliances, it is necessary that the wiring be grounded.

Potential equalization system

The potential equalization mechanism is sufficient important system. At the same time, everyone who wishes, having at his disposal necessary information, can assemble such a mechanism with his own hands, without involving assistants from outside. Installation of such a system is carried out in 5 stages, these stages look as follows:

- Installation of a box in which the ground bus will be placed;

– Mounting from the busbar and connecting a copper electrical cord with insulation. The cross section of the cord should not be less than 4 millimeters;

- Separate cords are placed in a pre-prepared channel inside the wall, which will connect the devices to each other. This is how potential equalization occurs.

Electricity has long been an integral part of our daily lives. People are so accustomed to this good that sometimes they forget about the dangers that may arise during the operation of electrical installations (household electrical appliances). On the initial stage designing the power supply of any facility, Special attention given to safety. Almost all users of electrical appliances know what bare wire, insulation, and grounding are. But the term "potential equalization" is familiar only to professional electricians. If we do not see outward signs of a problem, a false sense of absence of danger arises. And this despite the fact that an alternating voltage over 42 volts can be fatal to a person.

In what cases can voltage or electric current pose a threat to health or life

In itself, the presence of voltage (or potential) does not pose any problem. The danger is electric current. It occurs when there is a potential difference between the ends of the conductor.

It's important to know! The human body is a good conductor for electric current, due to the presence of fluid in the cells.

What is potential difference

For example, let's take an ordinary finger-type battery. On its positive contact there is a potential of approximately 1.5 volts, on the negative - 0 volts. If connect measuring device(multimeter) with a positive terminal (using both wires), the value will be zero. And if you measure between "plus" and "minus" - we will see a voltage of 1.5 volts on the device.

Why is this happening? There is a potential difference between the positive and negative contacts with a value of 1.5 volts. Accordingly, if you connect these terminals with a conductor (electric circuit, metal wire, etc.), an electric current will flow between them.

How it works on the example of electrical appliances

Take a household outlet 220 volts. There is a potential of 220 V at the phase contact, and 0 V at the zero contact. There is a potential difference of 220 volts between them. If you connect the contacts with a piece of wire with low resistance (conditionally 1 Ohm), then an electric current of 220 amperes will appear in the conductor (according to Ohm's law). Of course, in practice this cannot be done, the wire will instantly melt, and the insulation will catch fire.

If a person takes two contacts, then despite the high resistance of the body, the current strength will be enough for a fatal outcome.

All devices that produce electricity have a zero-contact connection to "ground": literally, to the physical ground. This means that between any phase conductor and the physical ground there is always a potential difference equal to the phase voltage.

The same thing happens in the conditions of the premises (residential, industrial, and others). A phase can be applied to the body of the electrical appliance. This may occur when emergency: damage to the insulation, moisture ingress into the contact group, malfunction of the power supply. Contact with a energized housing and an element of the premises infrastructure that is electrically connected to the physical ground (for example, a pipeline) at the same time creates a risk of electric shock.

If the electrical appliance has a properly connected ground, the phase on the case is connected to the "ground": a short circuit occurs and the circuit breaker disconnects the circuit. Electric shock does not occur.

This is an ideal situation when the norms of the Electrical Installation Rules (PUE) are complied with in the room.

In practice, the situation may be different.

Let's say your neighbor at the entrance connected the neutral wire to the heating system (we will not consider the reasons: from simple illiteracy to the desire to rewind the electricity meter). A dangerous potential arises on metal pipes: from 50 to 220 volts. Theoretically, the voltage should "go to the ground" because the steel pipes are laid in the ground. However, if a section of the pipeline is replaced with plastic between your apartment and the basement, the conductor opens. And your bathroom towel warmer has a potential of, say: 170 volts.

You touch a metal pipe and a grounded washing machine. The same potential difference arises (with a life-threatening voltage), only the source of the problem is not your electrical appliance, but the energized heated towel rail pipe.

As can be seen from the illustration, the protective earth in this case does not work.

Let's consider another option:

You have a power wire laid in the wall, next to which a water pipe runs. Under load (for example, a boiler or an electric oven is turned on), an EMF (electromotive force) can be induced in the pipe. Water will receive an unwanted potential, up to 50 volts. It may not be a lethal voltage, but when you touch a faucet in the kitchen, you will feel an unpleasant tingling electric shock. Especially if the floor screed has steel reinforcement, which, along the damp walls of the room, has contact with the physical soil.

In this case, the working ground also does not work.

Reasons for the appearance of a difference in electrical potentials

In addition to obvious conditions, such as breakdown of insulation on the body of an electrical installation, or unauthorized connection to structural elements, there are hidden factors:

Static stress. Occurs due to friction (for example, the movement of water in plastic pipe), dry air, dusty premises.
Electrochemical potential accumulation arising from the interaction of dissimilar metals.
atmospheric phenomena (thunderstorm, strong wind) contribute to the accumulation of electric potential.
wandering and induced currents, electromagnetic radiation(Microwave ovens, switching power supplies, monitors, TVs).

How to protect yourself from such situations? Rules for the installation of electrical installations (PUE) provides for a potential equalization system.

Leveling and Leveling

Let's analyze the basic concepts and terms:

Potential equalization- leveling the difference in the values of electrical potentials between the metal elements of the electrical installation, in the room where the electrical installation is located, including the conductive elements of the building. At the same time, a situation is considered dangerous when it becomes possible for a person to simultaneously touch the conductive parts. It is achieved by non-disconnectable connection of all current-carrying parts with each other using conductors.
Potential equalization- this is a system for reducing the relative difference in electrical potentials between grounding, conductive parts of electrical installations accessible to touch, the ground surface and all metal structures of the building. To do this, the potential equalization system must have a non-breakable connection with a working (protective) ground electrode.

In addition, potential equalization includes reducing the difference in electrical potentials on the ground surface (floor, ceiling) to prevent the effect of step voltage.

What does the term "unbreakable" mean? All conductive lines are permanently interconnected (terminal blocks, screw connections, soldering, welding, etc.). It is not allowed to install disconnecting devices: fuses, switches, circuit breakers. That is, the entire potential equalization system is a single conductive circuit, combined with a similar circuit protective earth.

Thanks to these systems, at all points that a person can touch at the same time, the electric potential is equalized to the same value. The situation when, when simultaneously touched at one point, there will be a voltage of 220 volts, and at the other 10 volts, is excluded.

Your home becomes absolutely safe.

Important! The system only works when everyone, without exception, metal objects merged. If at least one element or electrical installation is excluded from the connection by conductors, consider that the entire circuit is not operational.

What is the difference between a potential equalization system and a protective earth

grounding- this is a deliberate non-detachable electrical connection of parts of an electrical installation or circuit with a ground electrode. Designed to reduce voltage (at a point where it should not be under normal operating conditions) to a safe level.

As you can see, there is no concept of potential (potential difference) in the definition. In addition, the organization of grounding is carried out only at electrical installations, or electrical circuits. Potential equalization also applies to infrastructure elements, as well as to metal objects that are not electrical installations.

At the same time, protective grounding works effectively only in combination with devices protective shutdown(safety inserts, circuit breakers). Without such devices, the organization of grounding does not reduce the safety of electrical installations, and can lead to a fire if a phase-to-ground fault occurs.

Unlike grounding, the potential equalization system is self-sufficient, additional protective devices not required. The only condition is the presence of an electrical connection to the physical ground.

Requirements for organizing a potential equalization system in the PUE

There is no clear and universal definition of this system in the Electrical Installation Rules. The potential equalization device is specific depending on the application. AT different types premises, when working with various types electrical installations and laying current-carrying lines, there are their own methods.

For example, consider the imposition of portable protective grounding, in the production of repair work in electrical installations with a three-phase power supply:

All busbars within the same electrical installation are interconnected (potential equalization), and then connected to the ground electrode (potential equalization). When voltage appears on any of the parts, there will be no difference in electrical potentials, the work is carried out in safe conditions.

The PUE has a list of protective measures, where this system is mentioned as one of the items that must be applied:

organization of protective grounding;
automatic power off;
equalization of potentials;
potential equalization;
double or reinforced insulation of conductors and electrical installation housing;
organization of low voltage power supply (for alternating current- not higher than 50 volts);
protective separation of electrical circuits;

Creation of potential equalization systems

The project of each system is individual, and is developed in accordance with the configuration of the room. Exist general rules installation to be done:

What objects are connected to the potential equalization system

Metal enclosures of all electrical installations (if they are not properly earthed). The list also includes conductive housings for lamps (floor lamps).
Of course, the entire protective earthing system. Actually, the potential equalization system begins from it.
Metal parts of the building frame, reinforcement of the foundation, walls, ceilings.
Self-installed metal infrastructure elements. For example, steel mesh under the floor screed or metallic profile under drywall sheets.
Metal pipes and casings of the ventilation system.
Copper pipes of the refrigerant supply system in air conditioners (if they are long).
Metal sheaths of armored cables.
Screen braiding of information cables (television, internet).

Let's dwell on this point in more detail. The metal-braided cable starts from a distribution or amplifying device, which is located far outside your premises. However, you do not have the ability to control the correct power supply or grounding of these devices. A situation may arise when a phase will come to your house on the screen.

You, without suspecting anything, can simultaneously touch a live braid and a grounded metal object (for example, a heating radiator). The consequences are obvious - electric shock. When the screen is connected to a potential equalization system, an external phase breakdown on the cable is not terrible.

All metal parts of the water supply and sewerage system: pipes, faucets, stainless steel sinks, trays and metal shower cubicles, bathtubs.
Components of water heating systems: boilers, internal pipes.
Heating system: pipes, radiators, heated towel rails.
Gas supply system.
Lightning protection grounding (if you have a private residence, in apartment buildings"option" is not available). In this case, the lightning rod is connected to the common system, and to its own ground electrode at the same time.
Metal-plastic window frames (if the conductive elements are not covered with plastic).
Steel doors and door frames.

On the diagram it looks like this:

Potential equalization bus.
Lightning arrester from the power board. connected to the phase. In the normal state, there is no contact between the phase and ground conductors - there is a sufficient gap in the arrester. When a lightning strikes a power cable, an arc current to the "ground" occurs, and a potential difference of several thousand volts does not occur.
Data line surge protector.
Brackets for fastening grounding conductors to metal pipes.
Foundation grounding with a bus, which is part of a common potential equalization system.

Installation of a potential equalization system for an apartment building (industrial premises)

Installation of system elements begins during the construction process. When creating the foundation, a metal tire is laid around the entire perimeter of the future structure. This is a closed conductor (steel strip or armature) with welded branches for connection with grounding conductors, and for internal wiring of conductors. To ensure uniform spreading of the potential into the physical ground, several groups of ground electrodes are installed along the contour of the building at an equal distance. If possible, equal distance between them is ensured.

From common bus branching is carried out in each section (entrance), where an introductory power board is installed. A ground shield is formed, connected to the potential equalization system.

It is located in the shield room, or in basement. Access to the shield must be limited (if not a private house). Only representatives of the power company, or SUE, are allowed to service.

Important! The entire contour (frame) system is interconnected by welding. Only after checking the reliability and electrical conductivity of the connection, is the final pouring with concrete.

To vertical elements of the system, the ceiling reinforcement is welded. If necessary, bus transitions from room to room are performed.

After the walls were erected, outer wall a conductive busbar is laid for lightning protection installed on the roof. All these conductors are included in the potential equalization system.

Be sure to carry out bends in the form of reinforcement or steel strips in the mines, along which vertical pipelines (risers) are laid. After the installation of water supply and sewerage systems, to steel pipes conductors are welded for connection to the potential equalization system.

Important! In old houses, where they were repeatedly held repair work(without overhaul), there may be plastic inserts in the risers.

This means that the integrity of the potential equalization system is broken. It is recommended to duplicate the connection by simply connecting the ground conductor to the ground bar. This can be done with a contact clamp.

Reference Information

To maintain aesthetics, a potential equalization bus is not created in residential buildings in each apartment. Its role is played by a ground bus located in the input shield. According to modern electrical safety requirements, in all access shafts with risers, a steel strip is laid (for a potential equalization system) connected to a protective earth. It, as it were, loops the general circuit in the second circle, duplicating the grounding.

When creating your own system in an apartment, it is allowed to use this connection point. By creating your own shield, you can connect objects that are not electrical installations to it. For example - a bath (if it is not made of acrylic or plastic).

To do this, there must be a special contact on the case. If not, use standard fasteners.

Creation of a potential equalization system in a private house

The principle is the same as in multi-apartment housing, only the amount of work is much less. After installing the ground electrodes (this is a topic for a separate article), you lay a potential equalization bus together with the ground. Parallel wiring is made from it in accordance with the rules:

Established grounding points for sockets, electrical installations. Including conductive cases.
Connection of the entire metal infrastructure of the building, including lightning protection on the roof.

To estimate the number of covered objects - take a look at the illustration.

Connection points are marked with circles.

When building a new house, you can optimize costs by providing several basic shields for grounding and potential equalization. This will save the grounding conductor when wiring to different rooms.

In the bathroom, it is necessary to create an additional potential equalization system, even if the house has a main one.
When installing electrical heating elements underfloor heating systems, it is recommended to lay on top steel mesh. Then the armature is connected to the potential equalization system, and finishing pouring screed or self-leveling compound.
If your water supply is normally grounded, and a small plot metal-plastic pipe(such a scheme is widespread), the mixer body must be grounded with a separate conductor. This is especially true for the bathroom.
Differential protection system (RCD) electric boiler does not conflict with potential equalization. Sharing is allowed.

non-residential premises

In technical rooms, workshops, in production, a potential equalization bus (usually representing a working ground) is laid open way on inner wall. Grounding conductors of electrical installations are connected to it, as well as lines connecting all conductive elements of the room. Thus, an ideal potential equalization system is formed.

In office buildings, so as not to spoil interior decoration, you can hide the tire in a decorative plastic box for cable laying. Often, owners ignore grounding conductors from heating radiators. This is unacceptable - most cases of electric shock occur precisely when the equipment and heating batteries are touched at the same time.

Important!
Office premises are more dangerous in terms of potential differences in the most unexpected places. Uncontrolled tenant neighbors can throw any “surprise” in the form of voltage in the water supply system, or connecting a phase wire to an Internet cable braid. Therefore, before starting work in such a building, spend some time and money checking the protective earthing and potential equalization systems. You will save both the health of employees and office equipment.

Outcome

After studying the material, you have learned to distinguish between security systems when working in rooms with electrical installations. Behind every requirement of the Electrical Installation Rules is someone's life. Do not gain bad experience at the cost of your mistakes. The potential equalization system is mounted once, and forever gives confidence in safety.

Some physics lessons

As we remember from school bench, and in particular from the lessons of physics, any conductor has an electrical potential, which in itself is not dangerous. The threat lies precisely in the potential difference between different products, usually made of metal. As this difference increases, so does the risk of electric shock.

To understand exactly what potential equalization is, we can give an example. metal surface refrigerator has its potential, it is safe. A water pipe that may be nearby also has its potential value. And here the main thing is how much the potential of the refrigerator exceeds the potential of the pipe. And as we remember, the potential difference is the voltage. And accidentally touching these objects can pose a serious danger. Human body in this case, it acts as a jumper on the path from a larger potential to a smaller one. It is worth noting that all pipes and common house communication systems have a close relationship with each other.

Someone may object, saying that the magnitude of this voltage is not dangerous for humans, since no phase is supplied to the objects in question. In fact, there are times when even an ordinary ventilation duct can acquire a dangerous electrical potential. And here we smoothly move on to the term potential equalization, which is discussed below.

What does the term SOUP mean?

This definition means special connection metal structures conducting current in such a way that no potential difference is created between them. And, as a result, the risk of electric shock is also absent. The potential difference arises against the background of various phenomena:

atmospheric surges;
stray current;
static stress;
circulating ground current.

However, current leakage from electrical wiring through metal structures, of which the house is full, is the most dangerous. Potential can also slip through the cases of household appliances.

In other words, if there is a connection between all products, surfaces or structures, then they all have the same electrical potential. And since there is no potential difference, then there will be no voltage.

Necessary measure

The potential equalization system was not created out of a whim, but is necessary measure because it is about the lives and safety of people. Especially when it comes to providing protection against electric shock in residential buildings. increased attention during electrical work given to all available metal connections. The bath and pipelines carry a big risk.

Sometimes on sewers and water pipes different potentials appear. In this case, anyone can get a shock just by touching the faucet. However, this is only possible when these pipes act as a ground electrode or neutral conductor.

The need for such a protective measure is also caused by the fact that most residential buildings contain a considerable number of potential conductors. This is reinforcement embedded in the walls for rigidity. In addition to the water supply and heating systems, usually with metal pipes, there are also air conditioning, ventilation, and lightning protection systems. That is, equalization of potential is rather a necessary measure.

Ground bus

The EMS system alone is not enough, as various unforeseen circumstances may arise. Meanwhile, electricity must be safely diverted at any time. And for this, all conductive objects and elements are united by a ground bus, which is usually installed on the way to the building. And as an additional measure, a conductor coming from the PE electrical panel is connected to the busbar.

What does it give and what will happen if this is neglected? For example, an insulation breakdown occurred in the electrical wiring, and the appearance of a phase on the body of the washing machine is also possible. Then, standing on the ground, you can get an electric shock, and not only in contact with metal objects, but also with those that do not conduct electricity.

It turns out that a whole electrical circuit is created, through which the current rushes to the ground, but before that it passes through the human body. Thanks to the potential equalization system, all devices and objects are connected to the PE ground bus of the electrical panel, the current energy rushes through the conductor with the least resistance. And a safe current will pass through the human body.

Bathroom - a high-risk area

The bathroom, due to the almost constant high level of humidity, is a dangerous type of premises in terms of electrical safety. Moreover, this is where most of metal pipes. Just in this room or in close proximity to it, a box is placed, and in it is a ground bus. With the help of bolts, conductors are attached to it, which connect all the conductive objects of the room.

It should be borne in mind that only one conductor should go from each metal object or conductive surface. You need to connect all items with a common wire in order to save money. As an exception, you can make a ground loop in a private house, in which there is one serial connection, but without breaking the conductor.

Also, using separate wires, you need to connect all the available sockets in the room. If the bathroom door is metal, which improves the design, it is necessary to ground the door frame with a separate conductor.

In most cases, a box with a tire is installed in the place of the bathroom, where there is an accumulation of pipes. Usually, this area is sewn up by many residents to hide the unsightly view from the eyes. And there is a door for access.

Old is not always safe

In the old days, when the USSR still existed, the grounding system of the TN-C type was widely used. Stalinka, Brezhnevka, Khrushchev - all these houses were equipped with this particular system, which protected residents from accidental electric shock. In it, the protective and working wires are combined into a single conductor, called PEN. He, in turn, was connected to the switchgear of the building. The installation of the system was carried out in accordance with the rules for the installation of electrical potential equalization (PUE) of that time.

What was good about her? First of all - the simplicity of work and low cost. The system provides reliable protection from overcurrents. If necessary, circuit breakers are activated. However, there is a significant drawback - this is the absence of a separate ground conductor. This fact calls into question its use in multi-apartment residential buildings.

This type of grounding can be dangerous in the case of single-phase wiring, as it often ignites. But a much greater danger is fraught with a break in the PEN wire, or, as it is also called, zero burnout. This means that a phase may appear on the body of household appliances, which is not good. This usually happens when the current consumption is significantly higher than normal.

Currently, such a ground loop is no longer used in private homes. The same can be said about the construction of new buildings - the TN-C system has already lost its relevance. This is explained by the fact that modern Appliances significantly increased in power. In addition, in the presence of this type of grounding, it is prohibited to install the EMS.

Varieties

There are only two types of soup:

OSUP;
DSUP.

In this case, the first is considered the main one, and the second is additional measure. They also have differences, but in quality ideal option it's better to use both of them. Let's figure out why.

OSUP system

AT modern construction the BPCS system is provided for at the design stage of buildings, and its installation is carried out before residents move in. Part of the system are:

ground loop;
OSUP conductors;
protective PE conductors;
main ground bus.

The main task of this system is to protect the building from the penetration of electricity through any conductive paths. It could be pipelines. engineering communications, metal fire escape and other objects. When a high potential hits them from an external source, thanks to the BPCS, it will be immediately redirected to the ground.

The system successfully works with several types of grounding:

TN-C-S;
TN-S;

During installation, it should be remembered that the connection of conductors of the PE (protective) and N (working zero) types is strictly unacceptable. It is also strictly forbidden to connect when using loops. In addition, switching devices must not be included in the circuit.

DSUP system

If the task of the OSUP system is to ensure the electrical safety of the whole house, then the installation of the DSUP potential equalization system narrows the scope to some specific premises. Often this is the bathroom.

This is usually not necessary, as the BPCS provides excellent protection functions. But as soon as the tenants begin to redo something, violating the integrity of the project of the house, then here you simply cannot do without DSUP. Many apartment owners change metal pipelines to plastic ones. Such a forced measure, on the one hand, is justified, but on the other, a problem arises. All electrical connections that were provided by the builders are broken. And this already increases the risk of electrical injury.

In addition to the bathroom, the kitchen can also have high-risk electrical equipment. This system consists of the following elements:

potential equalization box (kup);
connecting conductors.

According to physical laws, the electric potential tends to change on a long conductor. That is, on the introductory section of the pipe it has the same meaning, and on the 9th or even 15th floor it has a different meaning. And the difference can be significant.

Carrying out the installation of DCS

Before installing the EMS, the first step is to find out which grounding system is used in the building. If TN-C, then it is impossible to carry out work in any case! Such a move could pose a serious threat to neighbors who do not have an EMS.

Before the work itself, you need to make sure that you have:

terminal box (KDUP or KUP) - for a bathroom it is better with protection IP54 or more;
copper single-core wire with a cross section of at least 6 mm;
protective wires;
fasteners (clamps, bolts, etc.).

After that, it is desirable to draw up a diagram on which to indicate the connection of all elements of the circuit, including the path of the conductor from the PMC box to the main ground bus of the electrical panel. And in order for the additional potential equalization system to work well, you need to clean the contact area well under the clamps.

The next step is to install the mounting box in a convenient location. This will be followed by the connection of the PE conductor, which is usually connected to the shield from the external ground loop, with the box bus using a prepared copper wire. After that, it is connected by means of separate wires to each conductive element, according to the drawn up diagram.

Moreover, if there are sections where the conductors of the main potential equalization system will not receive mechanical damage, then you can use a small section - 2.5 mm, in other cases it is better to choose a slightly thicker wire (4 or 6 mm).

Final stage

After installation of the DSUP system, it is imperative to take measurements in order to check its performance in order to avoid accidents. To do this, you will need to call an electrician or order the appropriate service from specialists in an electrical laboratory.

When studying the issue of power supply to my frame under construction and ensuring electrical safety, I came across such concepts as "grounding", "re-grounding", "potential equalization", "potential equalization". I did not find a clear explanation and differentiation of these concepts in one place (maybe I was looking badly), so I will try to deal with them in the articles of this site.

I'll start with the potential equalization system.

electrical installation - a set of machines, devices, lines and auxiliary equipment(together with the facilities and premises in which they are installed) intended for the production, conversion, transformation, transmission, distribution of electrical energy and its conversion into other types of energy (clause 1.1.3 of the PUE).

According to clause 1.7.32 of the EIC potential equalization - this is the electrical connection of conductive parts to achieve equality of their potentials.

In accordance with the definition of clause 1.7.10 of the EIC "Third party conductive part - a conductive part that is not part of the electrical installation. Under this definition of the PUE, all metal objects larger than 50 × 50 mm in size that are in the bathroom fall. The exact definition of the term "third-party conductive part" is given in GOST R IEC 60050-195 "INTERNATIONAL ELECTROTECHNICAL DICTIONARY. Part 195: GROUNDING AND PROTECTION AGAINST ELECTRIC SHOCK": third-party conductive part - a conductive part which is not a part electrical installation, but at which an electrical potential may be present, usually the local ground potential. That is, belonging metal parts(objects) to third-party conductive parts is determined, for example for bathrooms, by the possibility of the local ground potential appearing on them.

Potential equalization system (SES) is designed to equalize the potential of all conductive parts of the building, which include:

structural elements of the building;
engineering networks and communications;
lightning protection systems (if any).

The connection is made by PE protective conductors, which form a "mesh" in the building and must connect all of the above parts to the earthing device and earthing conductors. In the event of damage in the electrical installation and potential (voltage) on the conductive parts of the building, short-circuit currents or high leakage currents occur, which lead to the disconnection of the damaged section of the circuit from the power supply by circuit breakers or RCDs.

Types of potential equalization system (SES):

the main potential equalization system (OSUP);
additional potential equalization system (DSUP).

Main Potential Equalization System (BPCS)

The main potential equalization system should consist of the following elements:

ground loop (grounding device);
main ground bus (GZSH);
protective conductors PE;

The composition of the main potential equalization system according to the PUE

P. 1.7.82 of the PUE establishes that the main potential equalization system in electrical installations up to 1 kV must connect the following conductive parts to each other ( left only what I consider necessary for my home):

ground conductor connected to the grounding device of the electrical installation (in the TT system);
grounding conductor connected to the re-grounding conductor at the entrance to the building (if there is a grounding conductor);
metal pipes of communications included in the building: hot and cold water supply, sewerage, heating, gas supply, etc.
metal parts of the building frame;
metal parts of centralized ventilation and air conditioning systems. In the presence of decentralized ventilation and air conditioning systems, metal air ducts should be connected to the PE busbar of the power supply panels for fans and air conditioners;
grounding conductor of functional (working) grounding, if there is one and there are no restrictions on connecting the working grounding network to the protective grounding grounding device;
metallic sheaths of telecommunication cables.

The main ground bus (GZSH), it is also a PE bus, is installed in the introductory switchgear(VRU) buildings. The following is connected to the main ground bus (GZSH):

steel strip coming from the ground loop (grounding device);
PEN-conductor of the input line (cable) in the TN-C-S grounding system (PE-conductor of the input line (cable) in the TN-S grounding system).

PE conductors of group electrical wiring lines depart from the GZSH, as well as PE conductors for equalizing the potentials of the conductive parts of the building.

In the main potential equalization system (OSUP) IT IS FORBIDDEN:

Connection of PE conductors to N conductors, starting from the main earth bar.
Connect the PE potential equalization conductors with a loop (i.e. in series one after another).
Install various protective switching devices in the circuits of protective PE conductors (the circuit must not be interrupted).

Connection diagram to grounded structures, elements and engineering networks buildings in the BPCS should be radial, i.e. each grounded part of the building has its own potential equalization conductor.

Additional potential equalization system (DSUP)

An additional potential equalization system is necessary to provide additional electrical safety in areas with increased danger, such as a bathroom or shower room.

P. 7.1.88. The PUE establishes that additional system potential equalization must be connected to all accessible to touch:

exposed conductive parts of stationary electrical installations,
third-party conductive parts (i.e. not part of the electrical installation) and
zero protective conductors all electrical equipment (including socket outlets).

For bathrooms and shower rooms, an additional potential equalization system is mandatory and should include, among other things, the connection of third-party conductive parts that extend outside the premises. If there is no electrical equipment with zero protective conductors connected to the potential equalization system (i.e. with PE conductors, not to be confused with working zero!), Then the potential equalization system should be connected to the PE bus (clamp) at the input.

Heating elements embedded in the floor, must be covered with a grounded metal mesh or a grounded metal sheath connected to a potential equalization system. As an additional protection for heating elements, it is recommended to use an RCD for a current of up to 30 mA.

It is not allowed to use local potential equalization systems for saunas, bathrooms and shower rooms.

P. 1.7.83. The PUE establishes that the system of additional potential equalization should connect to each other all simultaneously accessible to touch:

exposed conductive parts of stationary electrical equipment;
third-party conductive parts, including accessible metal parts building structures building;
neutral protective conductors in the TN system and protective earth conductors in the IT and TT systems, including the protective conductors of socket outlets.

This system consists of the following elements:

potential equalization boxes (PEC);
potential equalization conductors.

The potential equalization box contains a PE bus, which is connected with a copper wire with a cross section of 6 sq. mm to the PE bus of the input electrical panel (apartment, house). After that, by connecting to the PMC, all metal structures of the bathroom are grounded:

heating;
cold and hot water supply;
bathroom (or shower).

Thus, protective conductors of potential equalization from grounded structures are laid with a copper wire with a cross section of 2.5-6 sq. mm and connected to the PE bus in the potential equalization box. Fastening of protective conductors of potential equalization to pipes can be done using metal clamps.

Also, all sockets installed in the bathroom are subject to additional grounding.

The issue of ensuring electrical safety and the implementation of an additional potential equalization system in bathrooms, showers and sanitary cabins is discussed in detail in Technical Circular No. 23/2009, approved by the Deputy Head Federal Service for Environmental, Technological and Nuclear Supervision Fadeev N.A. (letter dated 08.07.2009 No. NF - 45/2007) and approved by the President of the Association "Roselectromontazh" Khomitsky E.F.

The purpose of the circular is to clarify the implementation of a number of provisions of chapters 7.1 and 1.7 of the EMP and specific recommendations for the implementation individual elements systems of additional potential equalization in bathrooms, showers and sanitary cabins and bringing them into line with new international requirements regulated by the IEC 60364-5-54 standard.

Requirements for conductors of potential equalization systems are specified in chapters 7.1 and 1.7 of the "Electrical Installation Rules" (PUE) of the seventh edition.

However, at present, during the construction of buildings, plastic pipes in water supply systems are widely used, and therefore additional questions have arisen to ensure electrical safety in installations related to the likelihood of electric shock from a jet of water, water taps, faucets, heated towel rails and other metal elements of water fittings .

Note

Tap water of normal quality in terms of volume electrical resistance(conductivity) refers to semi-conductive substances and, from the point of view of the possibility of electric shock, not considered as a third-party conductive part.

When implementing an additional potential equalization system in bathrooms, showers and sanitary cabins, you must be guided by the following:

The system of additional potential equalization should include:
- all exposed conductive parts of the equipment;
- touchable third-party conductive parts, including metal fittings floor bases, protective shells and protective grids of heating cables, outer metal shells of protection class II equipment;
- protective contacts of sockets, bathrooms, showers and sanitary cabins.
When using metal-plastic pipes for equipping bathrooms, showers and sanitary cabins, conductive elements plumbing system(faucets, mixers, heated towel rails, valves and other parts made of metal) are considered as third-party conductive parts to be included in the additional potential equalization system. At the same time, it is recommended on pipes for supplying cold and hot water install conductive inserts and connect them to the additional potential equalization system. In this case, the elements of the plumbing system themselves: taps, faucets, heated towel rails, valves and other parts made of metal, do not need to be separately connected to an additional potential equalization system.
In the case of using metal pipes for risers and passing them in the sanitary duct of the corresponding premises, the installation of conductive inserts is not required, it is sufficient to connect the conductors of additional potential equalization directly to the metal pipes of the risers.
In buildings where water supply to bathrooms, showers and sanitary cabins is carried out branches in non-reinforced plastic pipes, conductive elements of the water supply system: taps, faucets, heated towel rails, valves and other parts made of metal are not considered as third-party conductive parts and are not subject to inclusion in the system of additional potential equalization. In this case, the installation of conductive inserts in front of the inlet valve on the side of the riser and their connection to the additional potential equalization system is considered as a recommended measure. Given technical solution provides electrical safety with inadequate quality tap water and / or when replacing plastic pipes with metal-plastic pipes during the operation of the building.
When performing an additional potential equalization system in the room, the installation of a special potential equalization bus is not necessary. If, during the implementation of the project, for constructive reasons, it was decided that it was necessary to install it, then it is recommended to place it in a plumbing box or other place convenient for maintenance.
In individual houses, when constructing an autonomous sewerage system, there is a possibility of the potential of the local land being carried in from the side of sewerage. To ensure safety in this case, it is necessary to install a special conductive insert in fan pipe(drain pipe) connected to the potential equalization system and / or connect the conductive parts of the sewage storage tank to the potential equalization system.
In sanitary cabins, to ensure electrical safety, the protective contacts of sockets installed outside on sanitary cabins should be connected to an additional potential equalization system, and the lamp in the toilet separate bathroom must be protection class II, as in zone 2 of the bathroom.
In buildings where water supply is carried out by branches from an external distribution network (main), the latter should be considered as local land. In the event of damage in external power supply networks, made in accordance with the requirements of the seventh edition of the Electrical Installation Code, on the protective PE (PEN) conductor of the installation, relative to the local ground, voltages up to 50 V may appear, and if the PEN conductor of the supply line is damaged (break), to values close to phase voltage. When performing plumbing inlets in pipes made of insulating materials, to ensure effective work the main potential equalization system, regardless of the quality of the water supplied, should be provide electrical connection of water with the potential equalization system directly at the water supply inlet to the building.
The cross section of the conductors of the additional potential equalization system connecting the PE busbar of the shield with third-party conductive parts must be at least half of the calculated cross section of the PE busbar of the shield. If there is electrical equipment in the room connected by a protective conductor to the PE bus of the shield and included in the system of additional potential equalization, it is not required to connect the PE bus of the shield to third-party conductive parts with a separate conductor (see clause 7.1.88 of the PUE).
The cross section of conductors connecting open conductive parts of electrical equipment and / or protective contacts of sockets with third-party conductive parts must be at least half the cross section of the PE conductor of the corresponding equipment power line.
The cross section of the conductors connecting the open conductive parts of the electrical equipment must be at least the minimum of the PE cross sections of the conductors of the power lines of the connected equipment.
The resistance of additional potential equalization conductors connecting any two third-party and / or open conductive parts accessible to simultaneous contact should be no more than calculated by the formula: R \u003d 12 / Ia, where: 12 is the safe voltage level V, adopted for zone 0 bathrooms and showers; Ia - the value of the current, which ensures the operation of overcurrent protection for a time of not more than 5 s, in the TN system (in the absence of data, the cut-off current is taken) or the rated differential breaking current of the input device for the differential protection device in the TT system. Note. The use of the TT system is allowed, in accordance with the provisions of clause 1.7.59 of the PUE, in limited cases, in particular, when connecting an individual residential building to overhead line up to 1 kV, made with bare wires.
According to the conditions of mechanical protection, the cross section of copper conductors of the additional potential equalization system must be at least:
- 2.5 mm 2 - in the presence of mechanical protection;
- 4.0 mm 2 - in the absence of mechanical protection;
- it is allowed to use steel conductors with a cross section of at least 16 mm 2.
Connections of the conductive parts of the additional potential equalization system can be made: according to the radial circuit, according to the main circuit using branches, according to the main circuit without branches (connection to a common inextricable conductor) and according to the mixed circuit.
In individual residential buildings and other low-rise buildings, in the presence of a single water distribution device (shield), the additional potential equalization system is combined with the main potential equalization system.

Sewer drains should be considered as a third-party conductive part only in case of blockage.

In buildings where water supply to individual consumers is carried out by branches from an external distribution network (main), which is typical for most low-rise buildings, the latter should be considered as local land.

In buildings where water supply is carried out by branches in plastic and electrically insulated metal-plastic pipes from a distribution network (main) made of metal pipes and laid outside the building, which is typical for water supply schemes for low-rise buildings, when using plumbing and heating systems, consumers may experience leakage currents, exceeding the threshold of sensitivity with serviceable consumer equipment. The differential protection devices installed at the input to the installation are insensitive to these currents, since the flow circuit of this type of leakage current is located between the PE conductor of the installation (all open and third-party conductive parts) and the local ground. To ensure safety guarantees in this case, it is necessary to provide an electrical connection between the water inlet and the main potential equalization system and / or the additional potential equalization system.

In prefabricated bathrooms, a switch block and a socket are installed outside, which is considered a corridor socket. But apart from the developers, no one knows about this, and citizens use them to connect portable appliances in the bathroom. To ensure electrical safety, the protective contacts of sockets installed outside on sanitary cabins should also be connected to an additional potential equalization system.

The protective PE wire of the socket line can be considered as an alternative to the conductor of additional potential equalization only if it is connected not directly to the socket, but, for example, through a connection block installed permanently.

Potential equalization- electrical connection of conductive parts to achieve equality of their potentials. PUE, paragraph 1.7.32. Protection against indirect contact.

Since the protective earth (PG) has resistance, and if current flows through it, it becomes energized, it alone is not enough to protect people from electric shock.

Proper protection is created by organizing a potential equalization system (SES), that is, an electrical connection and PE wiring, and all metal parts of the building accessible to touch (primarily water pipes and heating pipelines).

In this case, even if the charger is energized, under it is everything metallic and accessible to touch, i.e. current spreads over a large surface, which reduces the voltage, and as a result, the risk of electric shock.

In the brick houses of the Soviet period, as a rule, the EMS was not organized, while in the panel houses (1970s and later) it was organized by connecting in the basement of the house and the frame of electrical panels ( PEN) and plumbing.

Definitions:

Protective earth- grounding performed for electrical safety purposes -PUE p.1.7.29.

Working (functional) grounding- grounding of the point or points of the current-carrying parts of the electrical installation, performed to ensure the operation of the electrical installation (not for the purpose of electrical safety) - PUE p. 1.7.30.

The definition of FE for information equipment power networks and communication systems is given in the following clauses:

"Functional grounding: grounding to ensure the normal functioning of the device, on the body of which, at the request of the developer, even the slightest electrical potential should not be present (sometimes this requires a separate electrically independent ground electrode)" - GOST R 50571.22-2000 p. 3.14.

“Functional earthing can be carried out by using a protective conductor (PE conductor) of the equipment supply circuit information technologies in the TN-S earthing system.

“It is allowed to combine a functional grounding conductor (FE-conductor) and a protective conductor (PE-conductor) into one special conductor and connect it to the main grounding bus (GZSH)” - GOST R 50571.21-2000 p. 548.3.1

Main potential equalization system in electrical installations up to 1 kV, it must interconnect the following conductive parts:

1) zero protective PE or PEN conductor of the supply line in the TN system;

2) ground conductor connected to the grounding device of the electrical installation, in IT and TT systems;

3) a grounding conductor connected to the re-grounding conductor at the entrance to the building;

4) metal pipes of communications included in the building ...

5) metal parts of the building frame;

6) metal parts of centralized ventilation and air conditioning systems….

7) grounding device of the lightning protection system of the 2nd and 3rd category;

8) a grounding conductor of functional (working) grounding, if any, and there are no restrictions on connecting the working grounding network to a protective grounding grounding device;

9) metal sheaths of telecommunication cables.

To connect to the main potential equalization system, all these parts must be connected to the main ground bus using the conductors of the potential equalization system - PUE p. 1.7.82.

Additional potential equalization system must interconnect all exposed conductive parts of stationary electrical equipment that are simultaneously accessible to touch and third-party conductive parts, including metal parts of building structures accessible to touch, as well as zero protective conductors in the TN system and protective earthing conductors in IT and TT systems, including protective conductors of plug sockets - PUE p. 1.7.83.GOST R 50571.3-94.

Local potential equalization system.

An ungrounded local potential equalization system is designed to prevent the appearance of a dangerous touch voltage.

All exposed conductive parts and third-party conductive parts that are simultaneously accessible to touch must be combined.

The local potential equalization system should not be connected to the ground either directly or through open or third-party conductive parts.

Designations:

RE- protective earth

F.E.- working (functional, technological) grounding

Functional grounding in relation to healthcare facilities - to ensure normal, interference-free operation of highly sensitive electrical equipment when powered by isolating transformer or according to technical requirements for some types of equipment

(electrocardiograph, electroencephalograph, rheograph, X-ray computed tomograph, etc.) in operating rooms, resuscitation rooms, delivery rooms, intensive care units, functional diagnostics rooms and other rooms when the specified equipment is installed in them.

In the absence of special requirements of equipment manufacturers, the total resistance to current spreading of the grounding device should not exceed 2 ohms.

Where GZSH- the main grounding bar of protective grounding.

GShFZ- the main bus of functional (working) grounding.

Option "A", from the point of view of electrical safety, is permissible only if the equipment is powered by an isolating transformer (IT - network).

Use this option for networks likeTNS is strongly discouraged!

Fig.2. Scheme of the flow of the short circuit current to the body of the device when using independent functional grounding in a TN type network.

Since functional grounding, unlike protective grounding, does not have a connection point with the GZSH, and, accordingly, with a neutral, the short-circuit currents will not be hundreds or thousands of amperes, as happens with protective grounding, but only tens of amperes. The situation will worsen if the FE is set to 10 ohms according to the task, and there is no RCD in the circuit ( Computer Engineering, tomographs, X-ray equipment, etc.).

The maximum short circuit current will be 15.7A.

I kz\u003d 220 (V) / (4 + 10) (Ohm) \u003d 15.7 (A)

With this power scheme, it is better to use option "B" or "C", especially when it comes to powerful stationary equipment (X-ray machines, MRI, etc.).

In addition to the above, the situation (from the point of view of electrical safety) is complicated by the likelihood of a potential difference across separate systems grounding, especially if these grounding systems are located within the same room, see Fig.3.

Step voltage when the lightning protection system is triggered.
Short circuit to the case in the TN-S network before the protection system is triggered
External electromagnetic fields.

Option "B" useful for the reconstruction of existing facilities. In this case, functional grounding is often performed using a composite, deep ground electrode. The second positive point is that functional grounding and protective grounding connected by a potential equalization conductor mutually duplicate each other, increasing the reliability of the grounding system.