Purpose and principle of operation of residual current devices. RCD: Purpose, causes of operation, RCD connection. Response to leakage current

RCD is a separate type of protective electrical devices along with circuit breakers (AB). Although their purpose is precisely electrical protection, like AB, their principles of operation are different.

Why do we need RCDs if there is an AB?

Over time, the electrical insulation of live parts of electrical appliances, including heating elements, wires, power cords and cables, inevitably ages. And then the so-called leakage currents begin to flow from them through the conductive cases of various electrical appliances into the ground, ranging in size from several tens of microamperes to a few milliamperes.

Ordinary ABs do not react to the appearance of leakage currents in any way - after all, they make up negligible fractions of the rated currents of electrical consumers. However, their appearance (more precisely, the current exceeding a certain allowable limit) is an alarm signal. This is a warning about the approach of an emergency, and to prevent it, you need a special protective electrical device - RCD.

In addition, as you know, non-release (convulsive) current, which is a mortal danger for a person (at a certain time of exposure), is only 10 mA. Therefore, the need to create protective devices that respond to leakage currents in this range of values was felt from the very beginning of the widespread penetration of electricity into everyday life.

Explanation of device operation

Let's try to explain the principle of operation of the RCD using a hydraulic analogy. We will assume that water flows through a closed water heating circuit in the same way as electric current through wires. If a hole appears somewhere in the heating pipe, then water leaks through it. Therefore, its consumption (analogous to electric current) through two pipe sections, one of which is at the inlet of the circuit, and the other at its outlet, will be different. It is the same with leakage currents in an electrical appliance. You can compare how much current goes into an electrical appliance and how much goes out. In a single-phase electrical appliance, current enters through the phase wire, and exits through zero, so it is enough to compare the currents in these two wires. This is the principle of operation of the RCD in a single-phase network. If the current values at the input and output of the electrical appliance are not the same, then it disconnects it from the network in a time of the order of several milliseconds. Such a short response time is necessary because the leakage currents exceeding the tripping current of the RCD could be caused precisely by a person touching the conductive case of the device.

Operate current

But for the work of the RCD to become effective in domestic conditions, it took a lot of time. First of all, it was necessary to accurately determine the amount of leakage current that would be safe for a person during the operation of the device. Attempts to design RCDs for leakage currents of less than 10 mA led to the creation of large, complex and expensive devices, moreover, prone to false alarms from various electromagnetic pickups.

By the beginning of the 80s of the twentieth century. the current of their operation, based on experiments with volunteers, was chosen as 30 mA, and small-sized transformers with ferrite ring cores (they are called differential) were created, which became leakage current sensors. Electromechanical differential UZO-DM with a trip current from 20 to 30 mA, which are the most popular in everyday life, went on sale. Usually the letters DM are omitted, and the device is simply called the RCD.

The principle of operation of the RCD and the connection diagram

The currents flowing through the phase and neutral conductors in different directions excite two identical magnetic fluxes F1 and F2 in the annular core of the device transformer, however, the magnetic induction vectors corresponding to these fluxes are directed in the core oppositely and mutually compensate each other. Therefore, the total magnetic flux in the core is zero, as is the EMF in the secondary winding of the transformer.

If, due to an insulation defect, a leakage current appears that is close to the trip current, then F1 ≠ F2, a magnetic flux arises in the core, inducing an EMF in the output winding, capable of creating a current sufficient to trigger the RCD threshold element. Next, the latch of the power contact group is pulled, and its contacts open. This is the principle of operation of RCDs of all types.

In all types of such devices, there is a "Test" button, when pressed, a current leakage situation is artificially created to test the operation of the device. A flag or button with self-locking is used to re-enable the RCD after a test operation.

Varieties of RCD

Electromechanical and electronic types of such protective devices are known. The principle of operation of the RCD and the connection diagram of both types are the same, however, the devices of the first type do not need power supply and have a simple and reliable design. For their operation, there is enough leakage current in the protected electrical appliance.

An electronic RCD needs to be supplied with a supply voltage, since the threshold element in it is made in the form of an electronic circuit that amplifies the small current in the output winding of its transformer and creates an impulse for the executive relay.

In this regard, the electronic RCD transformer itself is smaller in size, dimensions and power. The threshold element module with an amplifier is powered by a controlled circuit, and if a conductor break occurs in its power circuit, then such a device will lose its operability. There are other risks in the operation of electronic RCDs. For example, the failure of its electronic components during surge voltages in the mains.

Since the reliability of electronic RCDs is lower than that of electromechanical ones, their cost is also less.

Three-phase RCD

A three-phase device, unlike a single-phase device, has four poles instead of two, since the neutral conductor passes through both types of devices. The principle of operation of a three-phase RCD is the same as that of a single-phase one.

The core of his transformer covers four conductors - three phase and one zero. The total current in the three phase wires (the so-called zero sequence current) is always equal in magnitude to the current in the neutral wire and opposite to it in direction (inside the RCD). In this case, the core of the transformer is not magnetized, there is no current in its output winding. If a leakage current appears in the protected device, then an alternating magnetic flux appears in the core, inducing EMF in the output winding of the transformer. A current proportional to the leakage current begins to flow through it, and if the leakage current exceeds the tripping current, then the RCD turns off the appliance. The balance of currents in the RCD control body is disturbed, and it works.

Three-phase RCD without neutral conductor

To protect against leakage currents of asynchronous electric motors, the windings of which are connected in a delta or in a star with an unterminated neutral, a 4-pole RCD with an unoccupied zero terminal is used. In the absence of leakage currents in the phases of the electric motor, the sum of the currents in the phase wires is very small and is unable to trigger the protection. The appearance of a leakage current from the phase wires through the motor housing to the ground causes the zero-sequence current to circulate through the RCD transformer, to which the electric device reacts. The general principle of operation of the RCD does not change in this case either.

Features of the use of single- and three-phase RCDs

Three-phase 4-pole devices have rather large trip currents, which allows them to be used only for fire protection, as well as AB with thermal releases. Protection of group lines to sockets in rooms, kitchens and bathrooms, or protection of individual power lines of powerful electrical appliances (washing machines and dishwashers, electric stoves, electric water heaters) should be carried out on 2-pole single-phase RCDs with leakage current ratings from 20 mA to 30 mA .

In order for the operation of the RCD in a single-phase network to be safe, it must itself be protected from overcurrent (during long-term continuous operation of a serviceable electrical appliance) installed in front of it by an AB with a thermal release.

RCD operation without grounding

As you know, in old Soviet-built houses, apartment electrical wiring did not have a separate zero protective conductor connected to the ground loop. It was assumed that its function is performed by a zero working conductor (the so-called TN-C power supply system with common zero working and protective conductors). And since in all editions of the PUE there is a ban on the installation of protective devices in protective conductors, then 2-pole RCDs that break both phase and zero at the same time are also banned. Even the latest 7th current edition of the PUE in clause 7.1.80 confirmed the inadmissibility of installing an RCD in networks using the TN-C system. The fact is that cases of electric shock during their operation were recorded.

The reason for this was the time difference between the operation of the device contacts, which is a few milliseconds. But if the contact in the neutral wire was disconnected first, then during the breakdown of the insulation on the case of a household electrical appliance, the consumer was under full phase voltage, so these few milliseconds were enough for a fatal defeat.

For apartments without zero protective conductors, it is unacceptable to install a general-apartment RCD, but individual such devices can be installed in group outlet lines with a common protective conductor or in the power lines of individual electrical appliances if the protective conductors of outlet groups or outlets are brought to their input zero terminals along the shortest path.

In this case, a break inside the RCD of the zero working wire before the phase one does not lead to a break in the protective conductor of the electrical appliance, since the section of the protective conductor from the input zero terminal through the socket and the power cord of the electrical appliance will remain intact.

Using a residual current device is a fairly relevant way to ensure the safety of the electrical network in the house. RCD is usually used for human protection. This article will provide information about its purpose, the principle of operation and the types of such equipment.

The main purpose of the residual current device is to protect a person from damage by alternating or direct current. If a faulty or damaged device is connected to the electrical network in a room, then when a person comes into contact with bare conductors, he can be struck by electricity. This equipment allows you to avoid electric shock in case of accidental contacts, as well as protect the house from ignition of the wiring in case of current leakage.

The device is a mechanical switching device for stopping the supply of differential current under certain conditions. The RCD de-energizes the power supply of the electrical network when a person (animals) touches the conductors of household appliances and equipment or with a ground contact. Operation occurs both with direct contact with parts of the electrical installation, and with indirect contact.

The RCD can also turn off if the external insulation or the contact of the conductors with the grounded case is damaged, if the grounding conductor and the working zero conductor are incorrectly changed, if the phase wire with the zero working one is changed while touching them under voltage. A disconnection can occur due to a break in the working neutral conductor, which, according to the scheme, can be placed before and after the protective device, and when a person touches a bare part of the body to live parts of the device.

Kinds

Like all protective devices for an electrical circuit, an RCD has its own types. In connection with the design and mechanics, the devices can be electromechanical and electronic.

Electromechanical. Connecting such a device allows you to provide the circuit with higher reliability. The action of the electromechanical type of devices allows it to be widely used in buildings for various purposes, due to the ability of mechanics to work at any load in the electrical network. The high cost is justified by the speed of operation and a long service life.

The main structural elements are a relay, a magnetoelectric latch, and a zero-sequence voltage transformer. Electronic. The design of this type of equipment is very similar to electromechanical, since the composition includes the same elements. However, the main magnetoelectric element is made in the form of an electronic circuit.

The circuit itself consists of comparative elements, a filter, an amplifier and a rectifier. Thus, when an electronic type residual current device is connected to the network, its operation will depend on the line voltage. The residual current device can be connected according to a certain scheme to an electrical single-phase and three-phase power line.

Classification of devices is carried out according to their reaction rate to a leak, according to the features of a circuit break, according to the permissible load, according to the method of preventing a short circuit and the type of installation of the housing. The choice of such a device should be based on its characteristics and circuit features.

Video “The principle of operation and the scheme of the RCD”

Principle of operation

The principle of operation of protective equipment is based on comparing the potentials of the differential current that passes through it. To do this, the potential is constantly measured at its input and output. Ideally, after measurements, the sum of the vector currents passing through the controlled conductors should be equal to zero. So, with a single-phase circuit of an electric line, the measurement is carried out on two conductors, and with a three-phase circuit, on three or more.

If the value of the outgoing alternating current in the network differs from the input to the RCD, then it will work, de-energizing the room. Potential difference ranges can be standard for a certain type of equipment, or they can have a range control to set an arbitrary value (of course, with a reasonable limit). If a leak appears on the line (a person touches a phase wire or a decrease in the resistance of the external cable insulation), then the vector sum of the incoming and outgoing current will be different. In this regard, the entire line will be de-energized.

So during the operation of the equipment, one can single out the main element in its design - a differential current transformer. It is a core with a winding. The design also provides for a preliminary check. On its body there is a special button for testing the device. The principle of operation of the test is an artificially created leakage charge. If everything is connected correctly and the residual current device itself works correctly, then after pressing the button, the power line branch will be disconnected.

Oleg Udaltsov

Eaton Power Distribution Components Product Specialist.

What is a residual current device

A residual current device, also known as an RCD, is a device installed in an electrical panel in an apartment or house to automatically turn off the power supply to the network in the event of a ground fault current.

Ground fault current occurs in wiring and / or electrical appliances when, for some reason, the insulation is broken in them, or when the bare parts of the wires that must be fixed in the terminals, for example, inside household electrical appliances, touch the housing of the devices - and the current begins to "leak" in the wrong direction.

This can lead to a fire due to overheating (first the wiring or device, and then everything around) or to the fact that a person or a pet will suffer from the current - the consequences can be extremely unpleasant, up to death. But this will happen only if you touch the conductor or the body of the equipment, which is energized.

The main difference between an RCD and a conventional circuit breaker is that it is designed specifically to break the earth fault current that the circuit breaker cannot detect. The RCD is able to turn it off in a fraction of a second, until the moment when it becomes dangerous to a person or property.

Where and how much to install

For one- and two-room apartments - in the general electrical panel of the apartment. If the housing area is large, then in several local electrical panels distributed throughout the house.

An RCD will be required for the entire system to protect against, as well as for separate lines that feed groups of electrical appliances with a metal case (washing and dishwasher, electric stove, refrigerator, and so on) - to protect against electric shock. If a malfunction occurs or an accident occurs, not the entire apartment will be de-energized, but only one line, so it will be easy to determine the culprit of the RCD trip.

However, it must be borne in mind: neither RCDs nor conventional automata save from an electric arc, or an arc breakdown.

An electric arc can occur when, for example, the wire from an electric lamp is often pinched by a slamming door and the metal part of the wire inside is damaged. At the site of damage, sparks hidden from the eyes will occur, accompanied by an increase in ambient temperature and, as a result, ignition of flammable objects nearby: first the wire sheath, and then wood, fabric or plastic.

To protect against such hidden threats, it is better to choose solutions that combine the functions of an automaton, RCD and arc fault protection. In English, such a device is called an arc fault detection device (AFDD), in Russia the name “arc fault protection device” (AFDD) is used.

An electrician can include the installation of such a device in the circuit if you tell him that you need an increased degree of protection. For example, for a children's room, where a child can handle wires inaccurately, or for groups of sockets for powerful electrical appliances with flexible wires prone to breakage.

It is equally important to install protection devices where the wiring is laid in an open way and it can be damaged. And also when planned, in order to avoid risks in case of accidental damage to hidden electrical wiring while drilling walls.

How to choose

A good electrician will recommend the manufacturer of the RCD and calculate the load, but you need to be sure that the recommendations are correct. And if you buy everything for repairs yourself, then all the more you need to understand what to look for when choosing a device.

Price

Do not purchase a device in the lower price range. The logic is simple: the better the components inside, the higher the price. For example, in some cheap devices there is no protection against burnout, and this can lead to ignition.

A cheap device can be made of brittle materials and break easily when you lift up the lever that has fallen when triggered. According to the RCD standard, it should be designed for 4,000 operations. This means that you will have to be puzzled by the choice only once, but only if you have purchased a quality product. By purchasing a low-quality device, you put yourself and loved ones at risk, not to mention material losses in case of fire.

Case quality

Pay attention to how tightly all parts of the device fit together. The front panel should be monolithic, and not consist of two halves. The preferred material is heat-resistant plastic.

Device weight

Give preference to heavier devices. If the RCD is light, then the manufacturer has saved on the quality of internal components.

Conclusion

To resolve issues related to electricians in the house, it is advisable to involve professionals. However, the entire responsibility should not be shifted to their shoulders. It is better to be guided by the proverb "Trust, but verify." With even basic knowledge of the subject and an understanding of the scenario for the future use of electrical appliances in the house, you can save yourself and loved ones from problems with electricity.

It is a mistake to assume that automatic current breakers are installed on the housing of household appliances to protect a person from injury in case of current leakage. For this purpose, the shields are equipped with a protective device. Having found out the principle of operation of ouzo, you can not be afraid for the life of your loved ones and children.

Protection protects against the effects of current on the body, when touching the body of the devices. The leakage of electricity that has occurred, by the amount of power, the current of which the machine does not react. Another important job of protection is to keep your home safe from fire.

Functional features of protection equipment

The case of the device made of conductive material, as well as individual parts and even pipelines, sometimes turn out to be dangerous to humans. The phase breaks through them, with various wiring breakdowns and other reasons. There is such a dangerous situation, as a rule, in 2 cases:

The main task - the leak must be immediately detected and the supply of electricity to this group of contacts is stopped. And also to switch off when a person touches a bare wire and prevent fires in the building.

Important. The protection is triggered by leaks, but it should be remembered that the case of any household appliance will become deadly if, during installation, you mix up the phase and ground wires at the entrance to the building.

What to look for when choosing an RCD

For the correct purchase and the safety of your home, you need to pay attention to the following indicators:

Important. Regardless of the brand and manufacturer of the protection device and different markings, 2 main characteristics show the value of the operating and leakage current. These values are indicated, regardless of the type of device and its price.

The principle of operation of the protection device

The principle of operation of the protective device is the reaction of the sensors when the incoming value of the differential currents changes. An ordinary transformer can act as a current sensor. According to its design features, it is manufactured as a toroidal core. The magnetoelectric relay has a fairly significant sensitivity to leakage, on it we set a certain value of the device actuation.

Devices in which the ouzo principle of operation is performed with the installation of a control relay are by far the most reliable, trouble-free. Even commercially available electronic devices that control leakage by means of an electronic circuit are inferior to electromechanical devices in some cases.

The principle of turning off electricity to consumers in a device with a relay is based on its operation and the impact on the mechanism for interrupting the electrical circuit. It consists of 2 parts:

According to the passport of the device, a contact group is selected for the maximum value of the current in the network.
In the event of an emergency and touching a bare area with a hand, a spring is provided to trigger the device.

The serviceability of the protection can be checked using the “Test” button equipped on the device case. By pressing it, we create an artificial malfunction of the electrical network in the event of an electric current leakage. The value is set sufficient to enable protection.

In this simple way, you can independently examine and check for the serviceability of the RCD without calling a technician and without paying for his visit. This check is carried out at least once a month.

By measuring the values of the current and the operating time of the RCD, a specialist electrician using a special device can conduct a more accurate check.

Correct operation of protection in different modes

How does ouzo work under normal conditions? Without leakage, the operating voltage, up to 12 V, flows towards and in parallel, while magnetic fluxes with the same magnitude are induced on the secondary winding of the transformer. They equalize with each other. Such operation does not trigger the residual current device due to the fact that the value of the current supplied to the secondary winding is zero.

Leakage current occurs when accidentally touching a bare section of wiring or a device case with a phase closed to it. In this case, the correct direction and magnitude of the currents passing through the transformer are violated. On the secondary winding, an unbalance of the current values occurs, from which the relay is triggered. It acts on the spring, the voltage supply to the network stops.

This is a simple explanation of the operation of the RCD, if necessary, there is enough information on the Internet to study this issue in more detail.

It must be remembered that the purpose of a residual current device is an additional measure for the safe use of electrical appliances. This device responds to leakage current. For this reason, it is necessary to install RCDs together with automata to turn off the network in case of a short circuit.

In this article, we will talk about an electrical device called fully RCD - a residual current device. A residual current device (abbreviated as RCD) is a more complete name: a residual current device controlled by a differential (residual) current or a mechanical switching device, which, when the differential (residual) current reaches (exceeds) a predetermined value, should cause the contacts to open.

The main task of the RCD (Residual Current Device)

The main purpose of the RCD is to protect a person from electric shock and from the occurrence of a fire caused by current leakage through worn wire insulation and poor-quality connections.

Combined devices that combine an RCD and an overcurrent (short circuit) protection device are also widely used. Such devices are called UZO-D with built-in overcurrent (short circuit) protection, or simply a differential automat. Often differential automata are equipped with a special indication that allows you to determine for what reason the operation occurred (from overcurrent or from differential current).

Residual current device: purpose

RCD - a residual current device is installed in the electrical network of an apartment or house to perform the following electrical safety tasks:

Increasing the level of safety in the operation of household and similar electrical appliances by people;
Prevention of fires due to ignition of insulation of current-carrying parts of electrical appliances from differential (residual) current to the ground;
For diffusers. Automatic shutdown of a section of the electrical network (including residential) in case of overload (TK-current protection) and short-circuit current (MTZ-maximum current protection).

Note: In Russia, the use of RCDs became mandatory with the adoption of the 7th edition of the Rules for Electrical Installations ().

As a rule, one or more RCDs are installed on a DIN rail in an electrical panel.

(I talked about installing an electrical panel in an apartment in another blog article :)

SUMMING UP THE FIRST SUMMARY

There are two types of RCDs on sale - Residual Current Device:

RCD directly.
And UZO-D (differential) is an RCD + short-circuit protection device, in “one package”.

Important!

The use of an RCD is an additional protective measure, and not a replacement for overcurrent protection using fuses, since the RCD does not react in any way to faults if they are not accompanied by current leakage (for example, a short circuit between the phase and neutral conductors. Therefore RCD must be used together with Circuit Breakers (fuses)
RCDs can greatly improve the safety of electrical installations, but they cannot completely eliminate the risk of electric shock or fire. RCD does not respond to emergency situations, if they are not accompanied by leakage from the protected circuit. In particular, the RCD does not respond to short circuits between phases and neutral.
The RCD will also not work if the person is energized, but there is no leakage, for example, when a finger touches both the phase and neutral conductors at the same time. It is impossible to provide electrical protection against such touches, since it is impossible to distinguish the flow of current through the human body from the normal flow of current in the load. In such cases, only mechanical protective measures (insulation, non-conductive covers, etc.) and the shutdown of the electrical installation before servicing it are effective!

RCD characteristics

Now let's deal with the characteristics of the RCD indicated on the device case.

RCD - residual current device designed to protect a person from electric shock when indirectly touched (a person touches open conductive non-current-carrying parts of an electrical installation that is energized in the event of insulation damage), as well as with direct contact (a person touches current-carrying parts of an electrical installation that are under tension). This function is provided by RCDs of appropriate sensitivity (cut-off current is not more than 30 mA (milliamps).

Note: In the US, according to the National Electrical Code, ground fault circuit interrupters (GFCI) designed to protect people must open the circuit at a current leakage of 4-6 mA (milliamps) (the exact value is selected by the manufacturer of the device and is usually 5 mA ) for a time not exceeding 25 ms (microseconds). In Europe, these values for RCDs, like ours, are 30-100 mA.

RCDs should operate in no more than 25-40 ms (milliseconds), that is, before the electric current passing through the human body causes heart fibrillation - the most common cause of death in electric shocks.

The list below shows the values of current through the human body and the most likely sensations that can be felt.

Important! don't try to experience it for yourself!

Current through the human body -0.5mA: not felt, weak sensations when touched with the tongue, fingertips and through the wound.
Current through the human body-3 mA: Feeling close to an ant sting.
Current through the human body-15mA: If you took hold of the conductor, it is impossible to let it go. Unpleasant, but safe.
Current through the human body - 40mA: Body spasms, diaphragm spasms. Danger of suffocation for several minutes.
Current through the human body-80 mA: Vibration of the ventricle of the heart. Very dangerous, leads to fairly quick death.

Hence the second short summary of the characteristics of the RCD

To protect a person in household electrical networks (single-phase current with a voltage of 220 volts), RCDs must be marked: cut-off current not more than 30mA, response time not more than 40 ms (milliseconds). Large manufacturers (such as ABB, Legrand) produce RCDs for human protection, with cut-off currents of 10 mA and 30 mA.

RCDs with a current of 30 mA are usually placed on group circuits. If you put an RCD of 10 mA, it is possible (there is always a background, natural leakage current in the apartment). 10 mA is usually placed on single consumers (washing machine, dishwasher). If you have a shower cabin, or a washing machine is installed in the bathroom (wet environment), using an RCD with a cut-off current of 10 mA is easy Necessarily.

It should be repeated:

For damp and very damp rooms (saunas, baths, baths, showers), an RCD with a leakage current of 10 mA (milliamp) should be used.
For other rooms, it is sufficient to use an RCD with a cut-off current of 30 mA (milliamps)
In wooden ladies, when conducting electrical wiring, in order to avoid fires, the installation of an RCD is desirable, or rather, it is simply necessary.

Note: On sale there are RCDs with cut-off currents and 100 mA and 300 mA or more. These RCDs (with 100 mA, 300 mA or more residual current breaking current are sometimes used to protect large areas of electrical networks (for example, in a private house or computer centers), where a low threshold would lead to false trips. Such low-sensitivity RCDs perform a fire-fighting function and do not are effective protection against electric shock.

RCD classification

Now let's note a few more points. In accordance with the classification, RCD - residual current device is divided into the following types:

Type AC-RCD, the opening of which is guaranteed if the differential sinusoidal current either suddenly appears or slowly increases.

Type A - RCD, the opening of which is guaranteed if a sinusoidal or pulsating residual current either suddenly appears or slowly increases.

The third result of the article

RCD type "A" is more expensive and more versatile, but both types "A" and "AC" are excellent for use in household electrical networks. Therefore, it is not worth focusing on this.

In wide sale, there are mainly RCDs of AC type (only the icon will be displayed on the facade of the device:

It should be noted that each RCD is designed to use a certain load in networks, namely a certain Amperage, which is indicated on the facade of the RCD. Since RCDs in electrical networks are used together with circuit breakers (fuses), I pay attention once again: the amperage of the RCD must be higher than that of the circuit breaker on the line.

RCD connection diagram

Now let's consider the RCD connection diagram - a residual current device, classical zeroing (TN-C). Most houses in the Russian Federation have a classic grounding, in the apartments of these houses there is no separate dedicated ground line, that is, two, not three power wires run throughout the apartment.

Note: In accordance with GOST 50571_3-94 (Safety requirements. Protection against electric shock):

In the TN-C system, protection devices that respond to the RCD-D differential current should not be used;
When a residual current protective device RCD-D is used for automatic tripping in a TN-S system, the PEN conductor must not be used on the load side. The connection of the protective conductor to the PEN conductor (independent earth conductor) must be carried out on the power supply side, i.e. to a protection device that responds to differential current (UZO-D). The diagram shows the connection points of the RCD-D.

Before connecting the RCD, I pay attention to how the RCD circuit works. The principle of operation of the RCD is based on a comparison of the output (left into the apartment) and the input (returning from the apartment) current. If it turns out that the balance is disturbed, and less comes in than leaves, then the RCD turns off the power supply. If the RCD is installed for one line, then there are two options: put an automatic machine after the RCD or the device itself must have a built-in maximum current limiter. Connecting an RCD without a machine will cause a short circuit or constant overheating to disable it. I remind you: that the amperage of the RCD must be higher than that of the machine on the line. Note: In the figure, the phase wire is fed to the lower terminal of the introductory machine. This is not entirely correct, it is better to supply power to the upper terminal of the machine. Although I note that connecting the power wires from above is just a tradition. It is she, and not some technical reason, that determines the recommendation to connect from above. And, although from the point of view of safety, it would be better to connect everywhere the same way, there is no strict ban on connecting from below. However, it is highly desirable that within the shield, and even better - throughout the entire facility, power is supplied in the same way: either from above (everywhere) or from below (everywhere). Other connection schemes can be found in the article:.

Well, that's probably all I wanted to tell you about the RCD - the Protective Shutdown Device used in household electrical networks with a voltage of 220 volts. Good luck to you in your endeavors!

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