Locking device. Residual current device. What is the principle of operation of protective devices

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 voltage). 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 tripping of which is guaranteed if the residual 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!

Specially for the site:

Electricity is one of the engineering systems that ensures our comfort. But the same electricity carries a potential threat, so the power grid must be as safe as possible. Ensure the safety of the automatic protection device. One of them is the RCD. What kind of apparatus is this, what does it protect against, what is the principle of operation of the RCD - all this will be discussed in the article.

RCD is a residual current device(alternative name - residual current circuit breaker, abbreviated VDT). Designed to turn off the power in the event of an emergency that leads to leakage current. This is possible in two cases: when the insulation is broken to the ground and when a person touches the current-carrying parts.

This picture will help to imagine the principle of operation of the RCD. An incandescent lamp acts as a load. The RCD compares the current before and after the load. If the difference exceeds the set value, then the device operates and opens the circuit

The principle of its operation can be compared with scales with two bowls. The current in the circuit is compared before and after the load. As soon as one of the bowls outweighs, then the current has found a "left" or workaround. Most often, a workaround is through a breakdown of the insulation to the ground, or through the human body is also not the ground. That is, part of the current "leaked" along this path. Hence the name - leakage current. The current did not go through the laid wires, and this is dangerous. And the appearance of a leakage current is a signal to turn off the power. In the RCD, the relay is activated, breaking the contact and de-energizing the network. This is the principle of operation of the RCD described in simple words - for a better understanding of the purpose and principle of operation.

How to understand what is leakage current

Leakage current occurs when there is a breakdown of the insulation on the case (the wire is frayed, the heating element is "punched", etc.). A leak is when you touch the body of a device that is energized. They touched with one hand and at the same time stand on a conductive floor without shoes or touch some other grounded object (central heating batteries, for example). Current will flow through your body, and it will “leave” through the ground loop, since this is the path with the least resistance. This will be the "workaround" way. As a result, the "returning" current will be less and the relay on the RCD will work.

But pay attention! Direct touch immediately to the phase and zero is not our case. In this case, the body is perceived as a load, and not as a leak. And this is a regular situation and protection will not work. Therefore, work with electricity with one hand, in dielectric shoes. And never touch zero and phase at once.

Connecting an RCD to a circuit improves safety. This is especially true for wet areas such as bathrooms.

Sometimes protection reacts to non-obvious things: neighbors are grounded “in the wrong place”, a stove with a piezo ignition without grounding, a washing machine or a dishwasher are connected with a metal-braided hose to metal pipes. In general, there are many situations in which a leakage current is generated. These are all also leakage currents, but they are the result of errors or violations. And the RCD also reacts to them. If outages occur for no apparent reason, they simply need to be identified. This is not easy, but you should not ignore “false” shutdowns. The reason may be dangerous.

What does it look like

On the front panel of the RCD there is a switch with which you can manually break the circuit or bring the device into working condition. The front panel also has a "Test" button for testing the functionality of the protection device. When it is pressed, a circuit containing a resistor is connected, which emits the occurrence of a leak. If the device is in good order, it will turn off the power - the "switch" will go down, opening the contact.

There are sockets for connecting wires at the top and bottom of the device. At the top, power supply wires are connected, at the bottom - lines that go to the load or to downstream devices. Both phase wires and zero (neutral) pass through the RCD. That is, when triggered, the power is turned off completely.

There are inscriptions on the body that reflect the main parameters. The RCD is mounted on a DIN rail, for this there are protrusions of a specific shape on the rear surface of the case. Fixing methods depend on the manufacturer. There are models that are simply hung, there are those with fixation with a pressure valve.

How to provide quality protection

Despite the obvious benefits of RCDs, it is impossible to do without a circuit breaker. The RCD does not respond to overcurrents (short circuits) or overloads. It only monitors the leakage current. So for the safety of the wiring, an automatic machine is also needed. This pair - automatic and RCD - is placed at the entrance. The machine usually stands before the counter, leakage protection - after.

Instead of a pair - RCD + automatic, you can use a differential automatic. These are two devices in one case. immediately monitors both the leakage current, and the short, and the overload. It is put if there is a need to save space in the shield. If this is not necessary, they prefer to install separate devices. It is easier to determine damage, cheaper replacement in case of failure.

The principle of operation of the RCD

The residual current device consists of a transformer, a relay and a tripping mechanism. The main working element of the RCD is a differential transformer with two primary windings and one secondary. It is he who compares the currents. The primary windings of a differential transformer have exactly the same parameters, but are connected towards each other. Current flows through one winding, which goes to the load, through the second - which returns from the load.

When the line is in good condition, the currents flowing through both primary windings are equal, but have opposite signs. As a result, the electromagnetic fields created by them cancel each other out. In such a situation, there are no induced currents in the secondary winding, the contacts are closed, and there is power.

As soon as a leak appears on the monitored lines, an overbalance appears in one of the primary windings (in the figure this is winding number 2). This leads to the fact that a potential appears on the secondary winding. When it reaches the threshold value (shutdown current), the relay is activated, turning off the power. This is the principle of operation of the RCD.

In general, the RCD is a simple device, but very useful, since it is it that is responsible for safety. For your safety and the safety of your children, we strongly recommend installing a residual current device in the shield.

Briefly about the parameters of the RCD

Despite the not too complicated device, there are a lot of parameters by which it is necessary to select an RCD. This:

All these parameters are selected when drawing up the circuit, since the wire cross-section, the connected load and many more details are important for selection. So first you need to decide on the number and power of consumers (light bulbs, large and small household appliances, heaters, etc.).

What is a fire protection RCD

Smart heads have figured out how to use the principle of RCD operation not only to protect a person from electric shock when the insulation is damaged. The same device can be used to prevent fires. Structurally, they are no different, they are simply designed for large leakage currents.

How does RCD work in this case? As you know, when current flows, the temperature of the conductors rises. With sufficient current, the heat can be so great that it can cause a fire. If you put an apparatus with a leakage current of 100 mA or more at the entrance to the house, it will not save a person from electric shock, but it can very much prevent a fire from occurring. How? It may well be that one of the protection devices is faulty. The phase insulation will be damaged, which will sooner or later lead to a fire. It may turn out that the damage is on the unprotected part of the lines. In this case, the fire RCD will turn off the power. This will mean that it has become too much to "leak" and it is necessary to revise the wiring: measure the insulation, check the heating, etc.

A fire protection device is installed after the meter. If we talk about the parameters, the minimum breaking current is 100 mA. The type is better selective, but choose the exposure time yourself. Selectivity will save you from false positives. Below, after the fire-fighting RCD, they put protection on the line, choosing the tripping leakage current depending on the type of load.

If you follow GOST, then on the lighting lines located in rooms with normal operating conditions, the installation of protective devices is optional. That is, on the lines that lead to lighting, "personal" RCDs and machines can not be installed.

Manufacturers

There is no official rating of RCD manufacturers, so you should focus on the reviews of practicing electricians. As a rule, when assembling a “fancy” shield, experts recommend using the products of three European companies:

ABB (Swedish-Swiss company);
Legrand (France);
Schneider Electric (France).

In the catalogs of the above manufacturers, alternative names for differential current protection devices will be more common. RCD - differential current switch (VDT). Difavtomat - automatic differential current switch (AVDT).

Schneider Electric has developed a line of Easy9 devices related to the middle price segment.

Differential switch EASY 9 (RCD) 2P 63A 30mA (article EZ9R34263). Easy9 devices belong to the middle price segment, but at the same time they differ in the quality, reliability and ease of use inherent in the equipment of the upper price segment

Many electricians are not satisfied with the quality of products from companies such as IEK, TDM, DEKraft, EKF.

Imagine the following - you have a washing machine installed in your bathroom. Whatever the well-known brand it is, devices of any manufacturer are subject to breakdown, and, for example, the most banal thing happens - the insulation on the power cord is damaged and the network potential appears on the machine body. And this is not even a breakdown, the machine continues to work, but it is already becoming a source of increased danger. After all, if they touch both the car body and the water pipe at the same time, we close the electrical circuit through ourselves. And in most cases it will be fatal.

To avoid these terrible consequences, they were invented RCD - residual current devices.

RCD- this is a high-speed protective switch that reacts to differential current in the conductors supplying electricity to the protected electrical installation - this is the “official” definition. In a more understandable language, the device will disconnect the consumer from the mains if there is a current leakage to the grounding conductor PE ("ground").

Let's look at the principle of operation of the RCD. For greater clarity, the figure shows its "internal" circuit diagram:

The main unit of the RCD is differential current transformer. In another way, it is called a zero-sequence current transformer. To make it easier for us and not to get confused in terms, let's call this node just a current transformer.

As can be seen from the figure, in this case it has three windings. The primary and secondary windings are included in the phase and neutral wires, respectively, and the third winding is connected to the starting element, which is performed on sensitive relays or electronic components.

The starting body is connected to the executive control device, which includes a power contact group with a drive mechanism. The test button is used to check and monitor the health of the RCD. Now imagine that a load is connected to the output of our circuit. Naturally, a current will immediately appear in the circuit, which will flow through the windings I and II. For further consideration of the principle of operation of the RCD, let's move on to a more visual diagram:

In normal mode, in the absence of leakage current, the circuit flows through the conductors passing through the window of the magnetic circuit of the current transformer. operating current loads. It is these conductors that form the back-to-back primary and secondary windings of the current transformer. These currents will be equal in magnitude and opposite in direction: I1 = I2. They induce equal but oppositely directed magnetic fluxes F1 and F2 in the magnetic core of the current transformer. It turns out that the resulting magnetic flux is zero, the current in the third (executive) winding of the differential transformer is also zero, and the starting element 2 is in this case at rest and the RCD is operating in normal mode.

When a person touches open conductive parts or the body of an electrical device, on which an insulation breakdown occurred along the phase (primary) winding of the current transformer, in addition to the load current I1, an additional current flows - (indicated in the diagram IΔ), which is for the current transformer differential(difference: I1-I2= IΔ).

It turns out that our currents are unequal, therefore, magnetic fluxes are also unequal, which no longer compensate each other. Because of this, a current appears in the third winding. If this current exceeds the set value, then the starting body is activated, it affects the actuator 3.

The actuator, consisting of a spring drive, a trigger mechanism and a group of power contacts, opens the electrical circuit, as a result of which the installation is disconnected from the network. To carry out periodic monitoring of the health (operability) of the RCD, a test button 4 is provided. It is connected in series with the resistor. The value of the resistor is selected in such a way that the difference current is equal to the passport tripping leakage current of the RCD (we'll talk about the RCD parameters later). If, when you press this button, the RCD is triggered, then it is working properly. Typically, this button is labeled "TEST".

Three-phase residual current devices They work in much the same way as the single phase ones. In three-phase RCDs, four wires pass through the core window - three phase and zero. the simplest three-phase RCD is shown in the figure:

A three-phase RCD includes a switch 1, which is controlled by an element 2, which receives a signal to turn off from the secondary winding 3 of the current transformer 4, through the window of which the neutral working wire N and phase wires L1, L2 and L3 (5) pass.

If the load is equal in the zero and phase (or in three phase) wires, their geometric sum is zero (the current in the phase wire of a single-phase RCD flows in one direction, and the current in the neutral wire of exactly the same value flows in the opposite direction). Therefore, there is no current in the secondary winding of the current transformer.

In the event of a current leakage to the grounded housing of the electrical receiver, as well as in the event of a person standing on the ground or on a conductive floor accidentally touching the phase wire of the electrical network, the equality of currents in the primary winding of the current transformer will be violated, since, in addition to the load current, a leakage current will flow through the phase wire, and a current will appear in its secondary winding - just like the description of the operation of a single-phase RCD considered above. The current flowing in the secondary winding of the transformer acts on the control element 2, which, through the switch 1, disconnects the consumer from the mains. The appearance of a three-phase RCD is shown in the figure:

Consider practical schemes for switching on RCDs in switchboards.
RCD switching circuit for single-phase input. Here, a switching circuit with a divided zero (N) and "earth" (PE) bus is used. As you can see in the figure, the RCD (5) is installed after the introductory circuit breaker, and after it, circuit breakers are installed to protect and switch individual loops. Looking ahead, I want to note that the presence of a bunch of automatic - RCD is mandatory, since the RCD does not provide current protection, both thermal and short circuit. Instead of this "combination" - automatic - RCD, you can use one universal device. However, more on that later.

Scheme of switching on the RCD with a three-phase input. Unlike the previous scheme, both single-phase and three-phase consumers are protected here. In addition, a combination of zero and ground buses (PEN) is used. An electricity meter - an electric meter - is connected between the introductory machine and the RCD. As you remember from the reviews on metering schemes, all switching devices that are installed before the metering device are subject to mandatory sealing by the power supply organization. Therefore, the design of the introductory circuit breaker must provide for this possibility.

So far, we have only talked about electromechanical RCDs. But if you remember, I mentioned that sometimes there are electronic devices. In principle, an electronic RCD is built according to the same scheme as an electromechanical one.

Instead of a sensitive magnetoelectric element, a comparison device is used (for example, the most common example is a comparator). For such a circuit, you need your own built-in power supply - after all, you need to feed the electronic circuit with something.

The residual current has a very small value, therefore, it must be amplified and converted into a voltage level that is applied to. All this, of course, reduces the overall reliability of the device, in comparison with the electromechanical one, here is just the case - the simpler the better. And to be honest, I have not yet come across certified electronic RCDs at all. Therefore, I cannot say something good or bad about them. Therefore, let's leave aside electronic RCDs and dwell on one of the main points in considering electromechanical residual current devices - their parameters:

RCDs have the following main parameters:

network type - single-phase (three-wire) or three-phase (five-wire)

rated voltage -220/230 - 380/400 V

rated load current - 16, 20, 25, 32, 40, 63, 80, 100 A

rated breaking differential current - 10, 30, 100, 300 mA

type of residual current - AC (alternating sinusoidal current, sudden or slowly rising), A (similar to AC, additionally rectified pulsating current), B (alternating and direct), S (time delay, selective), G (similar to selective, only the delay time is shorter).

I want to note one important point regarding the parameters of the RCD. Many are misled by the rated load current printed on the device case, and it is taken as the same parameter as in the circuit breaker. However, this parameter in the RCD characterizes only its “current carrying capacity”, this expression may not be entirely correct, but I introduced it for the availability of the concept of the term “rated RCD load current”.

The RCD is not able to limit the load current and it must be protected from current overloads and short circuit currents by automatic switches, which just provide protection against both overcurrent and short circuit currents. The load current of the RCD should be selected so that it is one step (of the rated current range) greater than the rated current of the circuit breaker of the protected line. That is, if there is a load protected by a circuit breaker for a current of 16 Amperes, then the RCD should be selected for a load current of 25 Amperes.

Here a logical question arises - why not combine both the circuit breaker and the RCD in one housing, especially in the case when the RCD is involved in protecting only one power loop? After all, in this case, they still work "in pairs." This point was touched upon a little in the previous article. Well, the question is quite natural and such devices, of course, exist. They are called differential circuit breakers or simply differential automata.

In the figure you just see such a device. Here is a three-phase differential machine. As in a three-phase RCD, it has four clamps each - phase and zero, and a "TEST" button. If it stops at its internal structure, then it is difficult to say something new here. This is a circuit breaker and an RCD in one bottle.

The cost of diffusers is quite high. For example, three-phase models of well-known foreign manufacturers cost about 100 Euros. Relatively expensive. However, the AV + RCD bundle will have an approximately comparable cost, and instead of four standard 17.5 mm modules on a DIN rail (with a three-phase version), it will take eight. So in some cases, diffusers are still preferable, especially if there is a problem of free space in the switchboard.

How to check the operability of an RCD or differential automaton? We have already mentioned the "TEST" button. However, such a check is very superficial and does not always reflect the real essence of things. Therefore, for objective verification, test circuits or specialized devices are used.

The requirement of reliable protection of a person from the damaging effects of current has always outstripped the possibilities of science and technology to create protective devices that satisfy this goal. Today, innovative developments in the electrical industry fully meet all the criteria for devices of this type. The article reveals the question of such a device as an RCD: what it is, its purpose, principle of operation, choice and application.

RCD stands for "residual current device"

Means and methods of electrical protection: modern devices and features of their work

As soon as the use of electric current entered our lives, it immediately became necessary to protect against its damaging effects on human health. First of all, this is the insulation of the conductive parts of the wiring and parts of the current receivers.

But complete isolation is impossible, since technological breaks and contact groups are present in any electrical circuit. There is always a possibility of violation (destruction) of the insulating layer of conductive elements and their mechanical damage, and most importantly, the statistical regularity in violation of safety regulations, instructions and rules for the operation of electrical equipment, both at the industrial and domestic levels.

Electrical protection: isolation and grounding

One of the most effective ways to protect against the damaging effects of electric current is to organize a ground loop. The ground loop is an artificial conductor connection to the "ground" (the so-called PE-conductor) of neutral conductive cases or parts of electromechanisms, having a resistance of not more than 4 ohms. The listed elements of electrical equipment may be energized due to a short circuit to the body of the phase wire or lightning current.

The main purpose of the ground loop device is to exclude the possibility of electric shock to a person or animal in case of touching the body or part of the mechanism of electrical equipment that is energized due to a short circuit of the phase electric current.

Note! In AC networks with grounded neutral and voltage up to 1 kV (this is the format of residential power supply), grounding is not used as the main protection against electric shock from indirect contact, since it is not effective.

The passage of electric current through the human body in the event of an impact in a system with grounding (right) and without grounding (left)

The problem of the most effective protection against the effects of electricity on a person was solved by the so-called differential current devices (UDT) - this is a large segment of control and protective devices for various purposes and design features. The classification of the UDT segment is quite extensive: from the method of control, the type of installation and the number of poles, to the possibility of regulation and time delay of the breaking differential current.

Consider what an RCD is. The decoding of this abbreviation is a residual current device. The requirements for the installation and use of UDT are given in the supplemented editions of the PUE - the rules for installing electrical equipment and in the series of standards for electrical installations of buildings IEC 60364 and the impact of current on humans and livestock IEC 60479-1.

Historical background for the development of RCDs

Germany was an innovator in the development of RCDs. The first working sample of the protection device was designed and manufactured in the thirties of the last century. The smallest possible differential current transformer was used as a leakage current sensor, and a polarized magnetic relay with a sensitivity of 100 milliamps (mA) and a response time of no more than 0.1 seconds was used as a control element.

The threshold for fixing the differential current in the prototype was about 80 mA. It was impossible at that time to develop a control relay with a sensitivity of less than 80 mA due to the lack of materials with the required electromagnetic characteristics. And only in the middle of the twentieth century, a new design solution for the RCD was proposed. The design took into account the mechanisms to eliminate false positives from discharges during a thunderstorm and significantly increased the sensitivity to differential current up to 30 mA.

The overall dimensions of the RCD have also undergone changes: from the size of a parcel box to a modern format that can be installed on a DIN rail in modern electrical cabinets.

Technical experts in electrical and electronic engineering are already making predictions for the future. They firmly believe that systems such as protection against electric shock will soon be managed by artificial intelligence.

It will be able to perform not only measuring and control functions, but also performing video and audio monitoring of the object given to it, make instant decisions on any random situations and, if necessary, notify the rescue services.

RCD: what is it and how does it work

Residual current devices (RCDs) are among the most demanded of protective UDTs operating in domestic conditions. The RCD works as a protector of a person from electric shock and as a preventive mechanism to prevent accidental ignition of wiring cables and connected cords of electrical appliances.

The functional idea of the device under consideration is based on the laws of electrical engineering, postulating the equality of the incoming and outgoing current in closed electrical circuits with active loads.

This means that the current flowing through the phase wire must be equal to the current flowing through the neutral wire - for single-phase current circuits with two-wire wiring and that the current in the neutral wire must be equal to the sum of the currents that flow in the phases for a three-phase four-wire circuit.

When in such a circuit, due to a person accidentally touching the non-insulated parts of the conductive elements of the circuit or upon contact of the bare part of the wiring (due to damage) with other conductive objects forming a new electrical circuit, the so-called current leakage occurs - the equality of the incoming and outgoing currents is violated .

This violation can be registered and used as a command to turn off the entire electrical circuit. On this process, the RCD was designed. And the "leakage" current in the framework of electrical engineering began to be called differential current.

The RCD can detect very small "leakage" currents and act as a circuit breaker mechanism. Purely theoretically, the principle of operation of the RCD looks like this (where I in is the input current of the neutral wire, I out is the output current of the phase wire):

I in = I out (balance of the system without violation, RCD in standby state);
I in > I out (the balance of the system is disturbed, the RCD registers the appearance of a differential current and turns off the supply network).

RCD will definitely protect

When an RCD is installed in the power supply network, this means that protection is provided against:

closing the phase wire to the body of the electrical appliance. In a large number of cases, these are the heating elements of washing machines, water heaters and heaters. Moreover, a breakdown can occur only when the thermal element is heated under the influence of current;
improper wiring, when unscrupulous electricians wall up the “twisting” of wires in plaster without using a junction box. If the wall is wet, a differential current will leak from this twist into the wall and the RCD will de-energize the line all the time until the plaster is completely dry or the connections are properly repaired;

improper installation in the electrical panel, when seemingly small, but "useful" changes made to the circuit change the current distribution and lead to a loss of high efficiency of the device. This will be discussed in more detail a little later.

RCD can work for reasons that are not evident from the first inspection of the connection diagram of household appliances. If you use a gas stove with electric ignition of gas, or a washing machine is connected by a hose in a metal case to a water tap, or when neighbors have grounded a water supply or heating system, then a current leakage will again occur in the electrical circuit, due to which it will work RCD. In such cases, rigorous engineering analysis is required.

Boundary conditions for RCD operation

Rules very often have exceptions. This principle has not bypassed the universal qualities of the residual current device in question.

The RCD will not respond when a person or animal is energized, but no earth fault current will occur. Such a case is possible when touching simultaneously the phase and neutral conductors, which are under the control of the RCD, or with complete insulation with the floor. RCD protection in such cases is completely absent. The RCD cannot distinguish between the electric current passing through the human or animal body and the current flowing in the load element. In such cases, safety can be ensured by mechanical protection measures (full insulation, dielectric casings, etc.) or a complete de-energization of the electrical appliance before its technical inspection.

The RCD, which is completely dependent on the supply voltage of the network suitable for the object, is in working order only if the specified network is in full working order. The situation can become dangerous when the neutral wire breaks “above” the RCD, and the phase wire remains energized. Then, in the wiring, the phase wire can become a factor in electric shock, and the RCD, due to its own incapacity, will not be able to turn off the power to the network.

The RCD can “freeze” in the standby state if the main contact rod in the solenoid is jammed or if the secondary winding of the control device fails, and does not work at the right time. In order to check the operating condition of the RCD, there is a test mechanism. If you regularly test the device (and for this you just need to press the "T" - test button), the risk of RCD failure will be minimal.

Application and how to connect an RCD

RCDs received their main application in domestic conditions when used in electrical groups of bathrooms, kitchens and socket groups of a large number of connected devices and equipment. This does not mean that it does not make sense to use an RCD on a common incoming network. This selective scheme is dictated only by the efficiency of management and marketing expediency, since RCDs for small currents are much cheaper at the price of devices with higher power.

However, in some cases, if we consider hostels, clubs, etc., it will be more reliable to use a general selective RCD due to the mass and simultaneous use of almost all elements of electrical equipment. The selective type RCD differs from the usual one in the large delay time of the tripping differential current (i.e., the trip time) and is one of the most used devices. When a conventional local RCD is triggered in any circuit, the general selective RCD does not turn off all the wiring at once, but allows you to stop the power supply of only a separate group.

For example, if a breakdown of equipment insulation occurs at a disco and the case (for example, an amplifier) is in contact with a phase wire, then at the moment the operator touches the amplifier, the local RCD trips and turns off only the amplifying equipment group, and the selective general RCD will not turn off all power and such groups as a common light, toilets and cafes will work as standard.

The mechanism for connecting an RCD to an existing network is similar to connecting a circuit breaker, with the only difference being that when two terminals are required on a single-phase machine, then four on an RCD.

If, when a person touches a bare section of a wire or a case of equipment under phase voltage, the electricity instantly turns off, it means that the RCD has worked.

Important! In AC systems, additional protection by means of RCDs should be provided for socket groups with a rated current up to 20A (washing machines, stoves, etc.) and mobile (portable) equipment and power tools with a rated current up to 32A, which are used outdoors.

The basic principles of the RCD mechanism and a comparative analysis of analogues

The physical processes occurring in the mechanisms of operation of many modern electromechanical or electronic devices may be completely incomprehensible to us. Not every person has knowledge of engineering and technical disciplines and, of course, is not able to understand and describe the physical basis of the principles of operation of a particular device. But the principle of use (rules of operation), built on security elements, makes it possible to use the most complex inventions in our daily life.

Related article:

Criteria for choosing fixtures. Types of overhead lighting fixtures. Types and prices of built-in models. Overview of LED chandeliers.

Each device has a technical passport, in which both the purpose and the principle of operation are always described in an understandable language, and whenever required, it prescribes installation, connection and proper operation measures. In our case, an attempt was made to describe the principle of operation of a trip protection device (RCD) in the most accessible way and to give the reader the opportunity to make their own decisions in choosing one or another device if necessary.

The principle of operation of the RCD and design features

To perform its protection function, the device consists of a differential current transformer minimized in size, a control "following" magnetoelectric relay, a control solenoid for the main contact group and additional diagnostic elements - the "Test" button and elements of triggering mechanisms.

The physical side of the work is as follows.

When the RCD is turned on (pressing the contact closure button), the solenoid turns on and holds the rod of the contact group in the same way as an electromagnet. Since at the same moment the terminals of the winding of the solenoid itself and the terminals of the supply wires come into contact. But in the power supply circuit of the solenoid, transit opening contacts are installed, which are controlled by a magnetoelectric relay and the relay is given the function of self-shutdown of the RCD.

The outgoing and incoming current of the network, flowing in the corresponding windings of the transformer, due to the produced EMF (electromotive force) creates two equal, but oppositely directed magnetic fluxes in the magnetic circuit (core).

Due to the complete compensation of magnetic fluxes, no EMF occurs in the secondary winding wound on the core, which feeds the control relay, and the relay is in a passive state.

At the moment a person or animal touches the bare part of the phase wire or the case of any household appliance on which a phase breakdown has occurred, an additional differential current will flow through the incoming winding of the transformer.

Violation of the equality of the incoming and outgoing currents instantly creates an uncompensated magnetic flux in the core of the transformer. And as a result, the instantaneous appearance of EMF in the secondary winding connected to the relay as its power source.

The relay, having received power, immediately operates and turns off the power to the solenoid (the transit terminals open), which holds the main contacts in the closed position.

The contacts open, the solenoid de-energizes and releases the spring-loaded rod of the contact group, and the power supply to the network is interrupted. The more sensitive the control relay is to small values of the differential current, the more effective the protective function of the RCD.

Note! Protection functions such as power outage in case of short circuit and current overload are not provided in the RCD. In practice, the installation of an RCD usually involves the sharing of an automatic switch ("machine"), directly designed for the possibility of a short circuit and current overload.

The correct connection diagram of the RCD and the machine. Mounting errors

Both devices have the same mounting design for installation in control panels for electricity metering and distribution. The task is reduced only to the correct connection to the mains and to each other:

The main option: central machine → metering → RCD.
Preferred: central machine → metering meter → RCD selective type → group machine → group RCD.

in no case do not connect the neutral wire to the ground terminal after it has left the RCD. In this case, periodic occurrences of differential leakage current are possible, leading to false alarms;
incomplete phase connection of the RCD. If the neutral wire from the mains passes in transit past the RCD, then the resulting current in the neutral wire will be perceived as differential, which will lead to a constant operation of the device;
do not allow the connection of neutral wires of sockets that are under the control of the RCD with the ground wire (terminal). In this case, even an outlet not connected to the consumer will create a differential current;
for group use of RCDs, jumpers of the neutral wire on the incoming terminals are not allowed. This will trip all RCDs at the same time.

Helpful advice!When connecting a four-pole. those. three-phase RCD into a similar network, it is necessary to strictly match the phase marking with the marking device terminals. Otherwise, the test mode will not be objective.

RCD analogues with advanced features

The market for RCDs (residual current devices) is very diverse. It should be distinguished from a number of analogues competing with RCDs, the so-called differential machine, belonging to the class of circuit breakers controlled by differential current - RCBO.

To answer in an accessible form the question: difavtomat, what is it? - it must be remembered that its main feature is the combination of the main function of the RCD and the circuit breaker. Also, the difference between an RCD and a differential automaton is that the RCD itself requires protection against short circuits in the network and overcurrent (of course, this is why a circuit breaker is installed in a pair), and the difavtomat is able to protect itself.

It should be noted the entry into the market of new models of RCBOs - electronic and with an auxiliary power source. They differ from electromechanical designs by the presence of an electronic board with a differential current amplifier, which allows detecting leakages of the order of 10 mA and work even if the neutral wire of the incoming network is broken, when the phase wire remains energized. A conventional RCD or RCBO in such a situation, when a person comes into contact with an open phase section, will not work.

Another novelty in the line of differential current devices is the so-called multifunctional protection device. What is USM becomes clear from familiarization with its purpose. This device serves to completely turn off the equipment when the voltage parameters in the network go beyond the operating limits (less than 180V and more than 260V), as well as to protect operating equipment from "burning" windings and electronic elements of voltage surges. These jumps can be caused by electromagnetic impulses or short circuits of phase wires to zero in a three-phase network.

RCD or differential machine: how to distinguish and what to choose

There is no unambiguous algorithm that allows you to give preference to one or another device. The reason is the multivariate feature of the choice. Consider the main factors that influence the choice of RCD or RCBO.

Is it possible to place this or that device in the main panel. In practice, the overall overall size of the RCD and the circuit breaker is larger than the overall size of the difavtomat.

What is the purpose of making changes to the electrical circuit. If it is necessary to individually protect high-power equipment (kitchen stove, boiler, washing machine, etc.) from a possible “shock” by electric current, a differential machine is optimally suited, which clearly monitors the load current.

If it is necessary to protect against electric shock for a group of sockets or a lighting line, in which the power can be increased over time, it is advisable to use an RCD. The RCD has a large power reserve, and the differential machine, due to overload, will need to be replaced with a more powerful one.

Qualitative assessment. Practice has proven that devices that combine many functions of various devices are often inferior in quality to single devices. This also applies to such a multifunctional device as a differential machine, which is inferior in quality and service life to an RCD and a circuit breaker.

The breakdown situation. In a situation where the RCD or circuit breaker stops working, either one or the other device needs to be replaced. But when the differential machine does not work, even due to the failure of one of some functions, you have to replace it with a new one. In this case, the costs are much higher.

Supply stability. If the RCD fails, it is enough to install jumpers between the circuit breaker and the power supply network (bypass the RCD) and the power supply is restored. But if the difavtomat breaks down, you will need either a spare difavtomat or a spare circuit breaker. So a quick prompt resumption of power supply may be in question.

Helpful advice! If it is necessary to correctly select the desired residual current device (RCD or RCBO), it is necessary to use an engineering approach and economic assessment even when one or another type of device is already at hand.

The question remains on the external difference between the RCD and the RCBO.

Labeling of the title side of the device. Example 1: “ABV 16A 30 mA” - we have an RCD ABB (manufacturer “ABV”) with a rated current of 16 amperes and a lower differential current of 30 milliamps. Example 2: “CHNT C16 0.03A” - we have a difavtomat in front of us, manufacturer CHNT with a rated current of 16 amperes and a characteristic of an electromagnetic and thermal interrupter of class “C” at a differential current of 30 milliamps.

The indicated wiring diagram is on the title side. For RCDs, the diagram shows a differential transformer (oval loop), a control relay (square) with a loop on the oval contour, and a test circuit in the form of a dash-dotted line. For a difavtomat, the circuit is very similar to the RCD circuit, only there are additional figures in the form of a small arc and a stepped line - these are the designations that are different from the RCD, electromagnetic and thermal interrupter.

Application and installation of RCDs: designations on wiring diagrams

Most of the control and management devices installed in the power supply network have a small list of parameters necessary for their correct selection in the electrical circuit.

The choice of RCD is made according to the rated load current and the threshold for fixing the differential leakage current. Practice recommends a value not higher than 30 mA. The installation of the RCD in the electrical network is carried out on the basis of an engineering analysis of the elements existing in the network and the installation possibilities. The scheme for connecting the RCD to the network must take into account all possible switching errors and eliminate them. Only when properly connected to the power supply circuit, the RCD will ensure maximum efficiency in triggering the protective mechanisms of the device.

Selection parameters and connection diagram of RCD without grounding

Knowing the principle of operation of the RCD, with a standard two-wire electrical network, represented only by phase and neutral wires, which does not have a ground loop, it is possible and necessary to install an RCD in accordance with the protection requirements. The correctness and installation schemes of the RCD were discussed earlier.

The answer to the question of which RCD to put in the apartment is with a calculator in hand. It is necessary to sum up the power of the pieces of equipment and equipment installed in the apartment, and divide the sum by the number 220. Thus, in a rough approximation, we calculate the rated current, according to which the choice of RCD will be made. This calculation is based on the mathematical dependence of the electric power on the mains voltage (220V) and the current strength that occurs when the load devices are powered:

M = U x I,

where M is power, U is voltage, I is current.

Example: you want to select an RCD to protect a group of electrical appliances in a kitchen unit. This line contains the following appliances:

Electric 2000 W.
Microwave 1200W.
Food processor 700 W.
Refrigerator 800 W.
Small household appliances about 600 watts.

We summarize the power consumption: 2000 + 1200 + 700 + 800 = 5300 W. We calculate the current according to the formula: I \u003d M / U \u003d 5300/220 \u003d 24.09A. We select the closest RCD with a large value - 25A.

For an in-depth calculation of currents in the wiring lines, knowledge of the basics of higher electrical engineering is required.

In addition to the rated load current and the sensitivity threshold of the differential current, in some cases, when choosing an RCD, it is necessary to pay attention to one more criterion - the category of leakage current. In most cases, this applies to alternating and pulsed current in the network.

Connection diagram for RCDs and automata using the example of an apartment

AC category assumes the operation of the RCD in an alternating current environment of differential leakage. This category is the most common and can be used in all types of AC networks. In what cases the RCD is triggered - it was discussed above.

Category A has the lowest sensitivity threshold (about 10 mA) for differential current and is able to record a separate component of the current amplitude (the so-called half-wave). An RCD with this category of leakage current reacts not only to a variable current configuration, but also to a pulsed one. Such RCDs are gaining priority use, as more and more household appliances, especially lighting elements, are transferred to pulsed current power supplies.

The main trend of the European market is the expansion of the impulse equipment segment. This, of course, will lead to an increase in the number of pulse current RCDs used. But since active current receivers (full of alternating current) will remain in domestic use for a long time, RCDs of the AC category will occupy a fairly wide space on the market shelves.

Returning to the question of the absence or presence of a ground loop in the electrical network, it is necessary to emphasize that even in the presence of grounding, the organization of protection against electric shock by installing an RCD in the network is even more required.

The basic principles of the RCD connection scheme in a single-phase network have already been considered earlier. The circuit for connecting an RCD with grounding is no different from a circuit without grounding.

Helpful advice! If the electrical network has a ground loop, it is necessary to control and ensure the correct circuit when connecting the RCD, when not a single neutral wire in the electrical wiring should be paired with the wire (terminal) of the ground loop.

Graphic designation of the RCD on the power supply diagram

The main directive provisions included in GOST 2.755-87 ESKD "Conditional graphic designations in electrical circuits of switching devices and contact connections" and GOST 2.710-81 ESKD "Alphanumeric designations in electrical circuits" prescribe graphic and letter designation of such devices as RCD. But no strict prescriptions for the different designation of differential current devices have been presented.

As we already know, all differential current devices are represented by a breaker mechanism and a control element - a differential current transformer. Therefore, the designation of the RCD in the diagram is represented by two standard graphic symbols - a circuit breaker and a transformer that registers differential current. You can see the graphic designation of the RCD on single-line diagrams and other drawings.

Three-phase RCD connection diagram

This type of device is usually called a four-pole device and the specifics of its connection to a three-phase network are completely similar to the connection of a two-pole RCD. On the body of the device, the terminals for connecting the phase wires and the neutral wire are indicated. Also, a passport is attached to the device, which presents standard schemes for connecting a four-pole RCD to a three-phase network.

Different manufacturers sometimes have differences in the location of the zero terminal on the device case - on the right or on the left, and the connection of phase wires only requires matching the designation at the input and output.

Four-pole three-phase RCDs are used for high differential leakage currents and their main purpose is only to protect against ignition of electrical wiring. To organize the protection of people from electric shock, it is necessary to install two-pole single-phase RCDs on each individual group of equipment with leakage current adjustment equal to no more than 30 mA.

Lineup, manufacturers and prices of RCDs

The market segment of UDT products is represented by a number of foreign brand companies, as well as domestic manufacturers. To date, preference is given to brands from Italy, Poland, Germany and Spain, as their products have received the best consumer rating in terms of quality, reliability and price-quality ratio. The existing market for UDT differential current devices allows the production of a wide selection of various types of devices, providing a diverse range of products both in price and quality.

The table shows the products of the most common manufacturers of UDT and shows the market prices they offer:

product name	Trademark	price, rub.
RCD IEK VD1-63 single-phase 25A 30 mA	IEK, China	442
RCD ABB single-phase 25A 30 mA	ABB, Italy	536
RCD ABB 40A 30 mA single-phase	ABB, Italy	740
RCD Legrand 403000 single-phase 25A 30 mA	Poland	1177
RCD Schneider 11450 single-phase 25A 30 mA	Schneider Electric, Spain	1431
RCD IEK VD1-63 three-phase 63A 100 mA	IEK, China	1491
Automatic switch IEK BA47-29 25A	IEK, China	92
Circuit breaker Legrand 404028 25A	Poland	168
Circuit breaker ABB S801C 25A single-pole	ABB, Italy	441
RCBO IEK 34, three-phase C25 300 mA	IEK, China	1335

As can be seen from the comparative table, the price of RCD 25A 30 mA (the most demanded on the market) depends on the manufacturer. So the price of RCD ABB 25A 30 mA is higher than Chinese counterparts, but lower than that of such manufacturers as Legrand or Schneider Electric. Taking into account such criteria as quality and cost, it is preferable to buy an RCD 25A 30 mA from ABB, and you can buy the necessary circuit breaker made in China or Legrand.

Helpful advice! Having decided to install an RCD in your home network, but having no experience in electrical installation of similar devices, use the services of a qualified electrician.

Summing up this excursion into the world of differential current devices, in particular, the residual current device (RCD), we will focus on the important points considered.

One of the most effective means of protecting humans and animals from the damaging effects of electric current is the installation of residual current devices (RCDs) in the power supply network.

The RCD has the function to respond to the differential leakage current that appears when a person comes into contact with a bare part of the wiring or the body of any electrical equipment. It may be under phase voltage due to damage to the insulation of the phase wire and its contact with the housing. Also, the RCD reacts to current leakage in places where the wiring insulation is damaged, when this can lead to heating and fire.

However, the RCD does not respond to short circuit phenomena in the wiring circuit and to excess current in the circuit. In this regard, it is necessary to install the device in tandem with a circuit breaker ("automatic"), which responds to a short circuit and power overload.

Most importantly, always follow the safety rules and caution when working with electrical appliances and machinery. As often as possible, visually inspect open current-carrying elements of electrical wiring and connected elements of current collectors.

RCD in any electrical circuit is a very important element. The main purpose of the RCD is to protect a person from electric shock when in contact with live parts. In addition, the RCD, the principle of operation of which will be discussed in this article, prevents the likelihood of fires that can be triggered by the ignition of electrical wiring.

In certain situations, the RCD, the principle of operation of which is quite simple, stops supplying voltage to the protected line. This happens if a person touches the current-carrying parts of electrical installations, and non-current-carrying elements, which, as a result of insulation breakdown, are energized. Another reason for opening contacts is the occurrence of current leakage to the electrical installation case or ground.

Consideration of the principle of operation of the RCD in general and on a specific example

When inexpensive apartments are rented from the developer, then all the electrics, including RCDs and diffusers, as well as wiring and circuit breakers, have already been installed. If you are building your own house or want to install an RCD in an apartment with your own hands, then you should know the principle of operation of this device and the rules for its installation.

RCD (the principle of operation is based on the detection of incoming and outgoing currents at the entrance to the system) can respond to minimal leakage and perform its protective function. To measure the leakage, a sensing element such as a differential transformer with three windings is installed in the device.

The principle of operation of the RCD can be easily understood with a specific example. If a person touches the live parts of the installation, or an insulation breakdown occurs on its case, the amount of current flowing through the phase wire will exceed the current in the neutral wire.

The total (final) flux of magnetic induction, in this case, will necessarily change, will differ from zero and will be the cause of current induction in the control winding. The relay to which the winding is connected will operate and the release of the contacts of the power protective device will be set in motion.

As a result of which a dangerous electrical installation is de-energized in a fraction of a second, it ensures the safety of human health.

Connecting an RCD to a single-phase network: basic rules

The RCD diagram is indicated on the body of the device and allows you to understand the principle of its operation, correctly connect the device to the protection circuit of the electrical circuit, avoiding incorrect operation of the device or its failure.

The RCD circuit, according to which it is connected to the power supply system, depends on various parameters and factors. In residential premises, as a rule, a single-phase version of electrical wiring with a rated voltage of 220 V is used.

Before installation, you need not only to understand the principle of operation of the RCD in a single-phase network, but also to familiarize yourself with the safety rules.

The principle of operation of the RCD and the wiring diagram imply the use of two wires of wiring connected to the input terminals, and two wires to the output of the device, connected to the corresponding output terminals. Install the device only when the power is off. Before installation, you need to make sure that there is enough space in the shield for the selected device.

And the wiring diagram is quite simple. There are several options for installing this device, but the principle, in general, remains unchanged.

The most common and affordable is the option in which the device is at the entrance to the house / apartment. The disadvantage of this option is that when the device is triggered, the entire living space is de-energized, and it is difficult to determine the cause of what is happening.

More expensive, however, very convenient is the connection option with the installation of several RCDs - in this case, each device will be responsible for a separate group of sockets or lighting.

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