Types and types of RCDs: what devices exist and how do they differ? Ouzo denominations. We select ouzo according to the characteristics of various types of devices Residual current device type ouzo 1

If you paid attention to this article, then probably not so long ago you asked yourself the question - “What is an RCD and what is its purpose?”. We will try to answer this question in as much detail as possible. Well, for starters, let's say that the abbreviation RCD stands for residual current device.

Despite the fact that today the electrical wiring is maximally protected from contact with people and sad consequences, there is no escape from leaks. Here indispensable assistant and become RCD. The device reacts with lightning speed to an increased current value at the place of leakage and cuts off the power supply.

RCD- this is one of the main "cogs" in the protective automation of current electrical networks. The device switches electrical circuits and protects them from currents that flow through conductive paths that are undesirable under standard conditions. This will increase the chances that your home or business will be protected from fires and no one will be harmed by the current discharge.

Note that this device has the function of turning on or off electrical circuits. In other words, he can switch them. Accordingly, the device is switching.

Why install an RCD

Many consumers have heard about the existence of such a miracle device as an RCD, but not everyone knows what it is for. Understand general principles the operation of the unit is possible even without deep knowledge in electricity. Until recently in residential buildings RCD was not used. But nowadays everything has changed, and now devices are increasingly found in apartments, so it’s worth learning more about them.

As already mentioned, RCDs are installed in order to prevent current leakage, leading to ignition of wiring and fires. In addition, the RCD will protect you from electric shock, which can lead to significant health problems or, God forbid, death when in contact with bare wires and conductive sections of electrical equipment.

NOTE! The RCD differs from automatic devices that protect wiring from overloads and short circuits, its purpose is to significantly increase the security of people.

The principle of operation of the RCD

The operation of the device is based on fixing the leakage current to the "ground" and turning off the power grid in the event of such an emergency. The device detects the presence of leakage only by the difference between the currents: those that left the device and those that returned back.

If everything is in order with the power grid, then the currents are identical in magnitude, but differ in direction. As soon as a leak appears - for example, you touched a wire that is not 100% insulated - part of the current goes "to ground" through another circuit ( in this case, through the human body). As a result, the current returned to the RCD through the neutral will be less than the current that came out.

The same thing happens if one of electrical appliances insulation is damaged. Then the housing or other part is under tension. Touching them, a person creates another contour "to the ground". In this case, part of the current will move along it, that is, the balance will collapse.

Of course, if the insulation is damaged, then the branch circuit may appear without the participation of human body. In this situation, the device will also respond 100% and save the network section from sad consequences such as overheating and fire.

When is an RCD required?

The device is indicated for installation when there is a need to protect group lines supplying plug-in sockets for portable electrical appliances. It is imperative to install an RCD if the circuit breaker or fuse does not provide an auto-off time of 0.4 seconds, taking into account the rated voltage of 220 V due to low current indicators.

In addition, it is recommended to install an RCD if there are people in your family who “love” to carelessly handle electrical wiring. The simplest case: a person drills a wall, while leaning his bare foot on the battery, and touches the phase wire. He flies along the chain "metal body of the drill - hand - rib cage- leg - battery "and leads to terrible consequences: paralysis of the heart or respiratory arrest (sometimes all together). If you have an RCD installed, it will instantly “understand” that part of the current has not returned, and immediately turn off the electricity. Yes, electric shock will occur, but the discharge will be minimal.

When does RCD not help?

RCD does not save from overvoltage, incl. from impulse, as well as from low voltage, which “kills” electric motors - in the refrigerator, washing machine, and so on.

The unit also does not protect against short circuits. This task is performed circuit breaker or .

How many RCDs need to be installed?

To determine the exact number of RCDs required for a particular room, you will need a specialist who can make the appropriate calculations. For example, in a 1-room apartment, one such device is most likely enough, designed for a leakage current of 30 mA. But in an apartment with four rooms, with 15 groups of outlets, you will need at least five RCDs, as well as one device for the entire lighting group, an electric stove and a water heater.

It is usually assumed that one group of electrical appliances is one 30 mA residual current device plus one 100 or 300 mA fire protection RCD.

NOTE! To control the wiring as a whole, at the entrance to a private house it is recommended to install one common RCD with a rated breaking current of 300 mA in addition to the calculated ones.

When is the installation of an RCD impractical?

Sometimes it just doesn't make sense to install a device. One such situation is the presence of old and decrepit wiring. The ability of an RCD to detect a leak can be a headache if the device starts to work unpredictably ( This is exactly what happens with bad wiring.). In this case best solution will put the RCD not in the power supply circuit of the apartment as a whole, but in places with increased danger for the use of sockets.

It also makes no sense to buy low-quality RCDs. On the modern market, you can find not only original devices, but also a wide range of fakes of unknown origin. Many of these devices are made "on the knee around the corner." The use of such devices is completely unacceptable and impractical. Please read carefully before purchasing technical documentation and quality certificates of the purchased unit.

It does not make sense to install the device in lines that provide voltage to stationary equipment and lamps, as well as in general power networks.

Device

The RCD device assumes the presence of:

leakage sensor;
polarized magnetic relay.

The operation of the device is based on laws based on incoming and outgoing electricity in closed circuits with extremely large loads. This indicates that the current should have only one value, regardless of the phase of passage.

There are three magnetic coils inside the device. A phase passes through the first, zero through the second. The current creates magnetic fields at the input and output of the coils of the device.

If everything works as it should, the mutual fields cancel each other out. If on one of the coils there is an imbalance, that is, a current leakage is formed, then this will lead to the action of the third coil, which has a relay to turn off the power.

Main technical characteristics

Each RCD has a specific set technical parameters things to consider before purchasing:

manufacturer;
model name;
operating current -- the limiting value of the current that the device can switch;
power supply parameters ( voltage and frequency);
leakage current - the maximum value of the leakage current to which the device responds;
RCD type;
operating temperature range;
rated conditional short-circuit current;
RCD device diagram.

Deciphering the marking

The marking is applied to the RCD case, which makes the choice of the desired model more convenient and easy. First of all, the manufacturer is indicated, but there is other important information there:

"RCD" or "VD" - means that this is a residual current device;
16A - the maximum current for which the contacts of the product and other internal elements are designed;
In 30mA - leakage current at which the RCD will trip;
230V and 50Hz - voltage and frequency at which the unit operates;
S - RCD selective;
the "~" sign - this means that the device is triggered by AC leakage.

In addition, there are inscriptions near each contact for the correct one:

N( above) - an incoming neutral conductor is connected to this contact;
1(above) - the incoming phase conductor is connected here;
2 (from below) - a phase conductor is connected to this place, which goes to the load;
N( from below) or the absence of a letter- the neutral conductor is connected, which goes to the load.

In order to, which is ideal for your electrical network, you need to understand the markings in detail, even if this task is very painstaking and tedious.

Species and types

Modern manufacturers offer the most different types and types of RCDs. The two most popular types of units in terms of their internal design in the electrical market are electromechanical ( do not depend on the strength of the current) and electronic ( depend). Selective and fire-fighting devices are also distinguished.

Electromechanical

Electromechanical RCDs are widely popular in use and are used in electrical circuits alternating current. What caused it? The fact that when a leak is detected, such a device will work, preventing sad consequences even at the most meager voltage.

This type of RCD in many countries is considered the standard of quality and one that is mandatory for widespread use. No wonder, because such an RCD will work even if there is no zero in the network and can save someone's life.

Electronic

Such RCDs are easy to find in any construction market. Their difference from electromechanical ones is inside the board with an amplifier, which requires power to operate.

However, such RCDs, as already mentioned, have a huge drawback - it is not a fact that they will work with current leakage ( it all depends on the voltage). If zero burns out, and the phase remains, then the risk of electric shock does not disappear.

NOTE! We are talking about the advantages and disadvantages of RCDs in general, and not specific models. If you are very "lucky", you can become the owner of a poor-quality RCD, both electromechanical and electronic.

selective

The main difference between a selective RCD and its “brothers” is the presence in the circuit of the time delay function for turning off the circuit that feeds the load, i.e. . Often this parameter does not exceed 40 ms. From this we conclude that selective devices are not suitable for protection against injury by direct contact.

Another feature of selective aggregates is good resistance to reaction to ( the probability of false positives is almost zero).

fire fighting

As the name implies, such RCDs are used in the power supply systems of apartments and houses to prevent fires. However, they are not able to protect a person, since the leakage current for which they are designed is 100 or 300 mA.

Typically, these units are installed in metering boards or floor switchboards. Their main task:

input cable protection;
protection of consumer lines in which differential protection is not installed;
as an additional layer of protection if the device below it suddenly did not work).

Number of poles

Since the RCD works by comparing the currents that penetrate the differential body, the number of poles in the unit coincides with the number of current-carrying conductors. In some cases, RCDs can be used with 4 poles to work in a two- or three-wire network.

At the same time, do not forget to leave free phase poles in stock. The unit will safely do its job not completely, but partially, which, in general, is unprofitable from a financial point of view, but possible.

Conclusion

Every day more and more household electrical appliances appear in our lives. Accordingly, the risk of current leakage increases, which sometimes even leads to death. If you are not killed by an electric shock, it will cause serious health problems or provoke a fire. From all these troubles there is one salvation - a protective shutdown device. We strongly advise you to install it at home, as they say, away from sin.

There are various types of residual current devices (RCD) according to their technical design. Below is an approximate classification of RCDs.

1. RCD classification by purpose:

RCD without built-in overcurrent protection (residual current switches, see Fig. 1, a, b),

RCD with built-in overcurrent protection (differential circuit breakers, Fig. 2, a),

have thermal and electromagnetic releases and protect against overload currents and short circuits.

2. According to the control method: RCDs that are functionally independent of voltage, RCDs that are functionally dependent on voltage (Fig. 2, b).

Residual current devices that are functionally dependent on voltage, in turn, are divided into: devices that automatically open power contacts in the event of a voltage failure with or without a time delay. When the voltage is restored, some models of these devices automatically re-close the contacts of their main circuit, others remain in the off state, to devices that do not open the power contacts in the event of a power failure.

There are also two versions of devices in this group. In one embodiment, the device does not open its contacts when the voltage fails, but retains the ability to open the power circuit when a differential current occurs. In the second option, in the absence of voltage, the devices are unable to trip when a differential current occurs.

RCDs that are functionally independent of the supply voltage (electromechanical). The source of energy necessary for functioning - performing protective functions, including the shutdown operation, is the signal itself for the device - the differential current to which it responds, RCDs that are functionally dependent on the supply voltage (electronic). Their mechanism to carry out the shutdown operation requires energy, obtained either from a controlled network or from an external source.

The reason for the lesser distribution of electronic RCDs is their inoperability when the neutral conductor that feeds them breaks. In this case, the body of the power receiver connected to the network through an RCD that does not open its contacts when the voltage disappears will be energized. In addition, despite the lower cost, their use is limited due to the lower reliability of electronic components.

Rice. 1. Electrical circuits of residual current devices: a - two-pole RCD, b - four-pole RCD, I - differential current transformer, II - comparison unit, III - disconnection unit, 1-6 - phase conductors, N- neutral conductor, I d> - designation of the differential current comparison unit with setting

Rice. 2. RCD electrical circuits: a - with overcurrent protection (TP - thermal release, EMR - electromagnetic release), b - with an electronic comparison unit (II) powered by the mains, I - differential current transformer, II - comparison unit, III - shutdown block

3. According to the installation method:

RCDs used for fixed installation,

RCDs of a portable type, including those connected with a cord. This, for example, is an RCD type A plug, plugged into a socket with a grounding contact, having a "Test" button with rated currents: working - 16 A, differential - 30 mA.

4. According to the number of poles and current paths, the most common are:

two-pole RCDs with two protected poles,

four-pole RCDs with four protected poles.

A number of manufacturers also produce three-pole RCDs with overcurrent protection.

5. According to the conditions of regulation of the breaking differential current:

RCD with one value of rated residual breaking current,

RCD with several fixed values of residual operating current.

6. According to the operating conditions in the presence of a DC component:

RCDs of AC type, reacting to a sinusoidal alternating differential current, slowly increasing or occurring abruptly,

RCD type A, responding to both sinusoidal alternating differential current and pulsating direct differential current, slowly rising or occurring abruptly,

U30 type B, responding both to sinusoidal alternating differential current and to pulsating direct differential current, slowly rising or appearing abruptly, and also responding to direct current.

7. By the presence of a time delay:

RCD without time delay - type of general application,

RCD with time delay - type S (selective).

In branched power supply systems, RCDs are used with different values of rated differential currents and shutdown times. At the beginning of the network, a selective RCD (type S) is installed with a differential current of 300 or 500 mA. Selective RCDs for currents of 1000 and 1500 mA are also produced.

To eliminate false trips during short-term increases in leakage current, as well as to ensure earlier tripping of RCDs at subsequent levels of power supply, selective RCDs have a trip time of 130 - 500 ms.

Residual current devices with a residual current of 30 mA perform the function of protection against electric shock electric shock, and selective RCDs with a current of 300 mA provide fire protection.

In the event of damage to the insulation and the flow of a differential current of 300 mA or more, the RCD of the lower level of protection with a current of 30 mA will first operate. The selective RCD, which has a longer trip time, will not work in this case and the power supply of undamaged electrical receivers will remain.

8. According to the method of protection from external influences:

RCDs of a protected design that do not require a protective sheath for their operation,

RCDs of unprotected design, for the operation of which a protective sheath is required.

9. According to the method of installation:

RCD surface mount,

flush mounted RCD,

UZO panel-panel board installation.

10. According to the instantaneous trip characteristic (for RCDs with built-in overcurrent protection):

RCD type B,

RCD type C,

RCD type D.

When you go to the store for a certain product, you probably know exactly what you need, what this product should be and for what purposes you will use it. The same applies to residual current devices and any other machinery or equipment. And before buying in the RCD store, you need to decide what type of device you need, for what load it will be used. In general, you need to decide on the parameters.

If we neglect some issues, it may turn out that devices of the same nominal value will work differently (or may not work at all) under certain circumstances.

Hello, friends! I welcome all visitors to my site "Electrician in the House". In today's article, we will continue the topic related to residual current devices.

If you remember, in the last article we examined how electromechanical ouzo differs from electronic, and in today's article I would like to raise an issue that relates to their varieties. And to be more precise, the types of protective devices by the type of current leakage -. Since this issue is also quite important and not everyone understands it.

Types of ouzo a and ac what is the difference

All residual current devices and difautomats are divided by type into several categories, for example, by internal design (electronic or electromechanical), time delay, number of poles, and by the type of leakage of differential current. It is on the latter category that we will focus. What does the type of RCD or RCBO mean by the type of differential current leakage?

Although we have an alternating current with a frequency of 50 Hz in the network, however, the leakage current can not always be alternating either. The leakage current can be variable, pulsating or constant, depending on what and where is damaged.

To understand what is the difference between ouzo type A and AC let's determine for ourselves what each of them reacts to (what kind of current):

RCD type AC will only respond to alternating leakage current. The waveform of such a current must be sinusoidal. In what situations does alternating leakage current occur? Damage to the insulation inside any household appliance(washing machine, refrigerator, water heater, etc.) and phase on the body. There can be many situations. RCD AC is the most common and common, it can be used everywhere.

As we have already found out, AC RCDs are only sensitive to current that has a sinusoidal shape, so they are labeled accordingly. An emblem in the form of a sine wave is applied to the case.

Type A RCD will respond to AC and DC ripple current leakage. As you understand, such protective devices more sensitive than AC, but accordingly they cost a little more. We found out how an alternating leakage current can appear, but where a constant pulsating leakage current can come from.

All modern technology is made on semiconductors (diodes, thyristors, converters, etc.). It's hard to imagine a microwave or washing machine without electronic stuffing. Today, even in energy-saving and LED lamps inside there is a switching power supply. And remember how to connect LED Strip Light- through a switching power supply.

I once met a statement on the Internet in one of the forums. One user wrote that RCD type A it will be useful only when someone will disassemble the equipment turned on under voltage and accidentally or intentionally sticks his hand into the power supply. Like, what kind of fool would disassemble a washing machine or a refrigerator under voltage, and touch their insides with their fingers?

But it is not at all necessary to disassemble something and touch the electronic board with wet hands. Everything has its service life and your Appliances no exception, everything breaks down and fails at some point. Inside the power supply, the secondary switching can be damaged and break through to the metal case, resulting in a current leakage that RCD AS may not feel.

Sometimes it happens that the passport of electrical equipment directly states that it must be connected only through a type A residual current device. Here, as they say, without options, you need to follow the instructions.

The DC pulsating current curve is in the form of half-wave sinusoids. Taking into account the fact that type A residual current devices operate on alternating and pulsating currents on the case, they are marked as follows:

According to the requirements of electrical standards, European countries have long refuse RCD with AC type and give preference to type A devices. RCDs of AC type can be installed on equipment without electronics (water heaters, underfloor heating, etc.)

By the way, our PUE rules also say a few words, but there are no specific requirements in this regard. Both types can be installed. Here is what the PUE paragraph 7.1.78 7th edition says:

What to install for yourself in the apartment ouzo type a or ac It's up to you, of course, to decide. I try to install everywhere and recommend RCD type A to everyone.

Testing ouzo type a and ac response difference

I think, in general terms, everyone understands what RCDs are by type of operation and what is the difference between AC and A devices. Now I would like to do a little testing between these two types of RCDs to clearly show which type will react to what.

In order to provoke the operation of the residual current device, we will create a DC ripple current leakage and see how our devices will or will not work.

How to create a sinusoidal leakage current and check the RCD at home, we have already considered in one of the articles on this site. The source of a constant pulsating leakage current will be a conventional rectifier diode, which is installed in almost every electronic technique.

I bought a 1n5408 brand diode and will assemble a circuit with which I will create a ripple leakage current.

At the input of the diode, we apply an alternating voltage (sinusoidal), and at the output we already remove a constant pulsating voltage. The shape of the curve will look like half-waves of a sinusoid that does not change its direction. Depending on the polarity of the diode connection (direct or reverse), a pulsating current will flow through the ouzo in different directions.

We assemble the power circuit - diode - light bulb. To make sure that the operation is correct, we change the polarity of the diode.

First, let's check the electromechanical ouzo type A of the hager brand, which just the same should feel such a leak. We create a leak through it using a diode and a light bulb. As you can see it worked.

To be sure of the reliability of operation, we change the polarity of the diode. As you can see, in this case, the hager protective device coped with the task.

The second one in our experiment will also be a hager ouzo but of the AC type, which in theory should not feel the pulsating leakage current at all. But in practice, everything turned out to be quite the opposite, and the AC type ouzo hager also felt leaks and turned off.

Moreover, this type of RCD worked at different polarities of the diode.

At first glance, it may seem that there is no difference between ouzo type a and ac, but in fact it is not.

The third in our experiment will be IEK electromechanical ouzo. We assemble our circuit so that a leak appears through the ouzo. As can be seen from the photo, the IEK protective device does not sense the leakage of pulsating current.

The fact that the IEK ouzo did not turn off does not mean that it is defective or of poor quality. The thing is that this device is of AC type, as evidenced by the marking. Now I hope you understand difference between ouzo type a and ac.

Let's try to change the polarity of the diode connection. As you can see, in this variant, the ouzo worked.

Types of ouzo, the principle of operation of an ouzo and a differential machine, how to check an ouzo, errors when connecting it, how often checks are carried out. +3 Photo with differences RCD type A and AC

TEST:

A small test will show the level of knowledge of this topic and the importance of choosing the optimal electrical protection device.

Do I need separate lines to connect powerful household electrical appliances?

With what leakage current is it necessary to install an RCD for children's rooms?

Is there a difference what type of RCD to purchase for house A or AC?

What is more reliable RCD + AV or AD?

a) RCD + AV;

Answers:

Yes. Separately drawn lines allow you to unload the introductory machines and arrange more reliable intra-house electrical networks.
10 mA. The resistance of a child's body is less than that of an adult. 10 mA is the only permissible conditionally safe value of the flowing leakage current.
Yes. Devices with characteristic A protect not only against alternating, but also constant impulse potential.
RCD + AV. Turning off the AD does not establish the cause of the failure: short circuit or leakage current. In the case of a residual current device and a machine, otherwise, re-enabling the AB in front of it allows you to determine the presence of a short circuit in the system. Also, if the difavtomat fails, it will be necessary to replace the node with a new one. In another case, it is necessary to replace the AB or a residual current device.

Residual current device - an electrical device designed to protect a person from damage by leakage currents. This key element in ensuring the safety of using household electrical networks.

Modern intra-house wiring is carried out by three-wire, and the requirements of the current Rules for the Installation of Electrical Installations require the mandatory presence of differential protection. Electrical distribution boards are equipped with differential switches ( devices sensitive to leakage currents) and RCD. The device is installed for the socket group and lighting network, as well as for stationary household electrical appliances.

Incorrect connection of the device leads to a decrease in the level of safety of the electrical network and its incorrect operation (false alarms).

For the correct connection of the electric device, it is necessary to understand its principle of operation and device.

Fig.1 Multilevel residual current protection

The diagram shows detailed diagram connection of a residential building: level 1 - fire-fighting models for 300 mA, level 2 - introductory, level 3 distribution RCDs for power networks, lighting and connecting individual electrical appliances.

Differences RCD type A and AC

Residual current devices are divided into subspecies depending on the principle of operation and technical characteristics.

Type of leakage current. Devices are divided into 2 types:

AC type. It works only on alternating leakage current (which occurs in the primary circuits of electrical appliances).
Type A. Responds to direct and variable pulsed differential current, i.e. on leakage currents that occur in the secondary circuits of electrical appliances (control boards, power supplies, etc.).

The abbreviation is indicated on the body: AC ("~") or A.

High-quality marking of the manufacturer helps to quickly understand the circuit and select the necessary model of the protection device.

Performance. Selectivity is determined by the protection response time:

Type G. The electric device is switched off after leakage current 0.06..0.08s.
Type S. Time delay - 0.15-0.5 s. best option when organizing multi-level protection. These are introductory protection devices, as well as fire fighting ones.
They work in case of incorrect operation or damage to the group electrical protection.

Operation principle. Distinguish models two types:

Electromechanical. Disconnection of the emergency section does not depend on the presence of voltage in the network.
Electronic. The operability of the electronic amplifier is ensured in the presence of an external power supply. If the integrity of the neutral conductor is broken, then such devices cannot provide protection against electric shock. Therefore, electronic models are less reliable.

Modern imported premium class devices are equipped with an electromagnetic relay that disconnects the load when the potential disappears.

3 ways to distinguish electronic RCD from electromechanical

The diagram shown on the body of the device. In electronic type models, there is an amplifier icon - "A" in a triangle. And the load from the outside is applied to the element. In electromechanical samples, the power supply circuits bypass the RCD elements, and nothing is connected to the differential transformer.
Charged battery. Connect the wires to the terminals of the electrical appliance, then connect them to the poles of the battery, if necessary, change the polarity. If nothing happens after the manipulations, then the device is of an electronic type.
Permanent magnet. The electromechanical device is sensitive to interference and is triggered when a magnet approaches.

Number of poles. Two- or four-pole are used, respectively, in single-phase and three-phase networks.

The principle of operation of the RCD. 2 main nodes

The operation of the electric device is based on the principle of constant comparison of the current value at the input and output. If the values are equal, the network is considered stable and secure. If there is a difference, then the sensitive element reacts to the change in parameters and the protection mechanism is triggered.

The main unit of the device- a differential transformer that responds to changes in parameters in the power grid. In normal mode, the resulting current through the core is zero. When a leakage current appears, the magnitude of the current in the phase and neutral wires is different, which causes the solenoid to turn off and the contacts of the electrical device to open.

Differential machine combines 2 devices: RCD and circuit breaker, simultaneously protecting electrical networks from leakage currents and short circuits.

Rice. 3. The principle of operation of the RCD

How to avoid incorrect operation of differential protection in the absence of grounding. 2 ways

During the construction of civil facilities in the Soviet period, there were no norms obliging to carry out grounding in each apartment. The final grounding point in such cases is the house electrical panel. The use of modern electrical appliances with a connection scheme without grounding is extremely dangerous. The use of electrical protection reduces the risk of electric shock.

Without grounding, the electric device ensures that the network is turned off when leakage current flows through the human body. At the same time, the speed of protection is such that the current does not have time to hit the body.

It is important to remember: in the presence of a grounding conductor, the electric device disconnects the line with the leakage current instantly. Without grounding, disconnection occurs only after a person touches a faulty electrical appliance (washing machine, water heater, etc.).

In household networks, RCDs without grounding for fire protection work equally well, as in the case of three-wire lines.

Conclusion: RCD is the main protection element in all circuits (with and without a grounding conductor). Provides fire safety at home and high level protecting a person from electric shock.

8 common mistakes when connecting an RCD

Incorrect connection of the residual current device endangers lives, so you need to know how to avoid accidents.

Incomplete connection. When connecting the phase and the neutral wire, false trips of the RCD occur due to the recognition of the current as differential.
The combination of working zero and ground in the outlet provokes protection trips when any load is connected.
Connection to the terminals of the device of all phases (in the case of a 4-pole RCD). The device cannot be judged to be functioning correctly.
Polarity mismatch. When changing places of the neutral and phase wires, right job RCD cannot be reached. In this case, without load, the “Test” button turns out to be inoperative, and when the electrical appliances are turned on, the difrela is activated.
Incorrect connection of the neutral wires of two or more RCDs. Standard testing reveals no problems. False positives start when the load is connected to the network.
Incorrect phasing (1 RCD for 2 machines, etc.) between several devices after the reconstruction of home wiring can lead to cyclic false operation of differential protection with a known good power supply and household appliances.
Connecting several protection devices with a common neutral conductor leads to the fixation of one / all RCDs of a false differential current. A jumper and connecting wires are not provided between several differential protection devices.
The combination of the neutral conductor with the ground after connecting to the electrical protection causes false positives.

You should not purchase a new device without determining the cause of its incorrect operation.

How to avoid device failure? 2 validation rules

Manufacturers equip products with a “Test” health monitoring unit. The program allows you to check the compliance with the norms and standards of the main parameters of the electrical protection apparatus: speed and fixation of the differential leakage current. The optimal frequency of checks is once a month.

Important: in addition to monitoring the main functions, regular testing determines the health of the PE conductor, its integrity and the quality of the connection to ground, the selectivity of the electrical device with a multi-level electrical protection system in the house.

When you press a button "Test" the device is supplied with an electric current equal to the value of the disconnecting differential. The duration of the test is not limited in time. A successful test (turning off the electrical protection device) indicates several factors:

Fast enough, corresponds to the declared characteristics;
The sensitivity of the device is sufficient to operate the protection at the rated differential current.

If there is no reaction to the manipulations, the RCD must be replaced, because. its sensitivity is insufficient or the shutdown time exceeds the declared one.

Important: regularly (at least once every 6 months) it is necessary to test the electric device with special testers. In such cases, the verification of electrical protection is carried out more accurately: the speed is limited to 200ms, and the sensitivity threshold is greater than the nominal one. This prevents all possible emergencies in household electrical networks.

The video describes in detail the steps to check the performance of the RCD in a domestic environment using improvised means.

RCD in household electrical networks is the main protection of a person from electric shock. Understanding the principle of operation and device structure allows you to quickly eliminate failures in the internal power supply system and prevent emergency situations.

Any electrical network must have a protection device, but not everyone knows what an RCD is and what principle of its operation is. The decoding of the abbreviation looks like this - a residual current device.

This electric low-voltage device is designed to turn off the protected section of the circuit when a differential current is created that exceeds the nominal value for this device.

In our article, we will try to analyze in detail the device and the principle of operation of the RCD, consider the existing varieties and figure out what information the marking of residual current devices contains.

The RCD ground loop device is a PE conductor of neutral conductive cases or parts of electrical mechanisms with a resistance of not more than 4 ohms.

If a leakage current occurs, these elements of the equipment may be energized, which poses a danger to human and animal life in contact with them, as well as to property in general.

To save from getting electrical injuries is the calling of survey devices. When a leakage current is detected, they turn off the voltage.

The greatest danger lies in the fact that such violations in the circuit are invisible and in rare cases tangible, when touching the device, you can feel a slight electric shock.

The main reason for this phenomenon is the violation of the insulating layer of the wiring. Uncontrolled processes can cause great harm, which is why protective equipment is becoming increasingly popular in the home.

The impact of conductive networks on the human body can result in disastrous consequences. This problem was solved with the help of RCD instrumentation related to the protective segment. Basic requirements for installation and use are described in IEC 60364

The use of RCDs has become most widespread in applications with alternating current and grounding of the neutral line, as well as with voltage indicators up to 1 kW in the household power supply format.

RCD design

Optional features of the protective mechanism will help to understand the principle of the RCD, namely the reproducible response of the device to current leakage.

Key work units include:

transformer differential sensor;
starting body - a mechanism that breaks an incorrectly functioning electrical circuit;
control block.

Opposite windings are connected to the sensor - phase and zero. During normal operation of the network, these semiconductor elements form magnetic fluxes in the core, which have the opposite direction with respect to each other. Due to this, the magnetic flux is zero.

The principle of operation / operation of the RCD is as follows: supplying current from the phase line to the control resistance and then to the neutral wire, bypassing the sensor.

Thus conditions are created different indicators current at the input and output of the device. This imbalance should lead to the launch of the shutdown node.

Depending on the developers, the circuitry device may vary, however, the principle used in the operation of the RCD will be identical for all models.

The principle of operation of the protective mechanism

Consider why you need to use RCD. The function of the protective device is based on the measuring method.

The incoming and outgoing parameters of the currents flowing through the transformer are fixed. If the first value is greater than the second, it means that there is a current leakage in the circuit and the device reproduces a trip. If the parameters are identical, the device does not work.

The feasibility of using RCD

Consider why you need to use an RCD and from what negative factors the device provides protection.

First of all - the short circuit of the phase on the body of electrical engineering. Basically, the problem areas include heating elements of heaters and washing machines. It is worth noting that a breakdown is formed only when the heat-producing part is heated under the action of a current.

Also, if the wires are connected incorrectly. For example, if twists without a terminal box are used, which are subsequently recessed into the wall and covered with a layer of plaster. Since the surface has high humidity, this twist will be a breakdown, leaking into the wall.

The differential protection mechanism in this case will permanently de-energize the line until the section is completely dry or until the connecting node is redone.

Automatic protection is effectively used in everyday life: in electrical groups for the bathroom, kitchen and sockets, with big amount powered appliances. Ideal when such devices are installed on each group of outlets

The scope of observation devices is quite diverse - from public buildings to large-scale enterprises. They are completed with electrical structures and circuits intended for reception and distribution: switchboards in residential buildings, current supply systems for individual consumption, etc. The main thing with this is correct.

Types of devices and their classification

Developers endow their products with diverse capabilities that must be taken into account when determining desired type RCD, starting from the specific operating conditions of the electrically conductive network.

In order for the average consumer to be able to choose the right residual current device among the variety of models offered, a classification system was created based on the following characteristics:

operation principle;
kind of differential current;
time delay of the tripping differential current;
number of poles;
installation method.

Classification #1 - by inclusion method

There are only two switching methods - electromechanical and electronic. In the first case, the machine will turn off the power on the damaged line, regardless of the mains voltage. The main working body is a toroidal core with windings.

When a leak occurs, a voltage is generated in the secondary circuit to activate the operation of the polarization relay, which leads to the activation of the shutdown mechanism.

Electromechanical type devices do not require external voltage. The source for their operation is the differential current on the fault line

The functioning of the device with electronic filling is completely dependent on the additional voltage, i.e. external power required. Here, the working body is an electronic board with an amplifier.

Inside such a mechanism there are no additional sources that accumulate energy, therefore, the electricity of the external network is used to operate the circuit, and if there is no voltage, the device will not break the circuit.

Determining the type of device: solder two wires to the terminals of the AA battery. Turn on the RCD and connect it to the input of the protective block, and the next one to the output. The lines are connected to one pole. If the device turns off, this means that the electromechanical type is presented, if not, the electronic

An example of the operation of an electronic RCD installed on a line with a socket from which a microwave oven is powered: a loss of the zero phase occurred, in addition to this, in the same period, a malfunction of the microwave wiring occurs and a phase short circuit to the case occurs, i.e. it has dangerous potential.

If you touch the stove, the electronic type of protection will not be activated, because. no mains supply. It is precisely because of the unreliability in comparison with the electromechanical counterpart that this device has become less widespread.

Classification #2 - according to the type of leakage current

All models of manufactured safety devices are additionally divided by the load current passing through the device. They process the voltage of a given oscillation format.

The nominal value of the operating voltage is written on the case of all devices and in the passport. This parameter must correspond to the rated current range of the electrical equipment.

The AC type will be activated upon the instantaneous occurrence of an alternating leakage voltage in the controlled circuit, or upon its wave-like buildup. These devices are marked with the inscription "АС" or the symbolic sign "~".

The most suitable form factor for domestic use- UZO-AS. The model is the cheapest of the devices of similar action. In the passport for electrical engineering, manufacturers often indicate specific model circuit breaker suitable for this product

Type A is triggered by the instantaneous formation of an alternating or pulsating breakdown current in the controlled circuit, or by their slow increase.

This mechanism can be used in any of the situations presented. The abbreviation "A" or a symbol is applied to the body of the machine, as in the graphic image in the rectangle.

Most often, the A-type is connected to a circuit where load control is reproduced by cutting off the top of the sinusoid, for example, adjusting the speed indicators of the engine's rotational movements with a thyristor converter.

RCDs of subspecies B are effective for reproducing the reaction in a slave electrical circuit of direct, alternating or converted (rectified) leakage current.

This is expensive equipment designed for industrial facilities. In domestic conditions, they are not used.

The presented trip protection devices of type A, B and AC are designed for an activation time of 0.02-0.03 s.

Classification #3 - by type of time delay

This classification assumes a distinction between two types: S and G. Type S auto-protection can be characterized by a selective format response. The response time delay corresponds to the range of 0.15-0.5 s. It is advisable to choose it in the case of a group connection of the RCD.

According to the diagram, there are two load groups in the shield in the form of sockets No. 1 and No. 2, to which an RCD of type A is connected, and a second machine - S is connected to the entrance of the room.

If a breakdown occurs in one beam, the input device is activated only when the collective device does not fulfill its function and does not turn off the defective area.

Open circuit activation selectivity can be done using another method, through the leakage current settings. This method is the most widely used.

Scheme of an apartment shield with two load groups, where two are connected different types protective devices: AC with a breakdown setting, and the second A, but with a larger value

Let's take a diagram similar to the previous one and modify it in this way: we select the group machine of the AC type only with a diphth current setting of 0.03 A, and at the input there will be a similar device only for 0.1 A.

There are situations where the differential current in the fault circuit exceeds the rated settings of the two protection devices. For the first scheme, the selectivity will not be violated, and for the second, the cutoff current can be supplied by any of the connected devices.

The G form factor device is also represented by a selective actuation principle and has a shutter speed of 0.06-0.08 s. All described selective types are designed for exposure to extreme currents - up to 15 kA.

Some models of RCDs have a diforgan setpoint adjustment system, others do not. However, for domestic purposes, the second version is suitable.

The limiting current is an important selection parameter, because This is what ensures safety.

For example, in rooms with high humidity, electrical appliances are powered by connecting disconnecting devices with a setting of 0.01 A to the circuit. For standard living conditions- 0.03 A.

For the organization of fire safety of buildings - 0.1-0.3 A. We recommend that you familiarize yourself with the tips on and the intricacies of its installation.

Classification #4 - by number of poles

Due to the fact that the automatic device operates on the principle of comparing the magnitudes of the current passing through it, the number of poles in the machine will be identical to the number of conductive lines.

A bipolar RCD is designated as 2P. It is included in a single-phase circuit to ensure human protection and prevent possible causes fire.

Marking of four-pole RCDs - 4P. They are designed to work in a network with three phases. A combination of installation is also possible, for example, a device with four poles is introduced into a two-wire network.

However, in this case, not the full potential of the device will be realized, which is economically unprofitable.

When installing a circuit breaker, it is worth considering the possibility that the load current may exceed the maximum operating values of the device. Therefore, in addition, a circuit breaker with a rated voltage not more than the operating current of the safety system is installed.

Classification #5 - according to the method of installation of the device

Since differential protection devices are available in different housings, they can be used as fixed or portable devices.

In the second case, the device is supplied with an extension wire. Devices fixed on a din-rail, which is located either in the corridor or in the apartment.

There are also options for the type and RCD plug. In both the first and second cases, any electrical appliance connected through such a mechanism does not pose a danger to humans in the event of a breakdown.

Full decoding of marking values

Without fail, the name of the developer company is present on the body of the device. This is followed by a standardized marking with a serial number designation.

To decipher the abbreviation, we will use the following example [F][X]00[X]-:

[F]– protective shutdown device;
[X]– performance format;
00 - numeric or alphanumeric designations of the series;
[X]– number of poles: 2 or 4;

Explanation of the abbreviation: 1 - brand; 2 – device type; 3 – selective view; 4 - compliance with European standards; 5 - rated operating current and setting; 6 - maximum alternating operating voltage; 7 - rated current that the device can withstand; 8 - differential making and breaking capacity; 9 - wiring diagram; 10 – manual performance check; 11 - marking of the switch position

The maximum parameters for which the devices are designed include: voltage Un, current In, the differential value of the circuit opening current IΔn, the ability to turn on and off im, breaking capacity Icn.

The main marking values must be located in such a way that they remain visible after the appliance has been installed. Some parameters may be applied on the side or on the rear panel, visible only before the installation of the product.

Outputs intended only for connecting a neutral wire are indicated by the Latin symbol " N". The disabled RCD mode is indicated by the symbol " ABOUT» (circle), included - short vertical bar « I».

Not every product has optimal temperature readings. environment. In those models where there is a symbol, this means that the operating mode range is from -25 to + 40 ° C, if there are no designations, it means standard indicators from -5 to +40 ° С.

Conclusions and useful video on the topic

Video material with a detailed overview of all the constituent elements of review protection mechanisms, their purpose and the principle of interaction with each other:

Do you have questions about the principle of operation or classification of residual current devices? Or do you want to supplement the material presented with useful information? Please write your clarifications in the comments block, ask questions - experts and competent visitors to our site will try to answer you as detailed as possible.