What is an ouzo in electrics, the principle of its operation, parameters, manufacturers. What is an ouzo What is a residual current device

In this article, we will talk in detail about:

• What is an RCD in electrical engineering?
• Let's look at how the RCD works and the principle of its operation.
• Let's talk about standards.
• Let's consider the classification of RCDs.
• Construction.
• Main characteristics.
• Use in everyday life.

Now, first things first.

What is an RCD in electrical engineering?

The abbreviation RCD stands for - residual current device (more precisely, a protection device controlled by differential current, abbreviated as difavtomat UZO-D).

Residual current device RCD (difavtomat UZO-D)

Protecting people from electric shock remains one of the most important engineering problems since the beginning of the widespread use of electricity in industry and everyday life. Solving it turned out to be more difficult than protecting the networks and electrical equipment themselves from overcurrents. Automatic circuit breakers with thermal and electromagnetic releases, which successfully control the load current, cannot save a person who has touched live parts or live parts. Also, with their help, it is not possible to respond in a timely manner to leakage currents associated with insulation failure and reduce the risk of fires. The situation has been significantly improved by the development of protective shutdown devices that monitor the appearance of differential currents and break the circuit at a certain value. Such protective devices were called RCD-D; in the USSR they were developed in the early 70s in the electrical safety laboratory of VIESKh and were produced at the Gomel Electrical Apparatus Plant. Today, UZO-D from both domestic and foreign manufacturers are represented on the Russian market.

Operating principle of RCD (UZO-D)

The operation of the RCD-D is based on detecting leakage current to the ground and disconnecting the network when it appears. The fact of a leak is detected by the difference between the currents leaving the RCD and returning to it through the neutral. If the network is in order, then they are equal in size, but opposite in direction. When a leak occurs, for example, a person touches a wire, part of the current will go through his body “to the ground” along another circuit, and as a result, the current returning to the RCD through the neutral will be less than the output. The same situation will arise if the insulation of some electrical load device is broken and the housing or other part is energized. A person touching them will create an additional circuit “to the ground”, part of the current will flow through it and the balance will be disrupted (this situation is shown in the figure). The difference between the outgoing and incoming currents is detected by a transformer with a ring-shaped core. The phase wire and neutral N pass inside it and serve as the primary winding. The secondary winding is connected to an actuator that opens the contacts. Of course, if the insulation is damaged, a branch circuit can be formed without the “participation” of a person, but in this case the RCD will also work and protect the network section from dangerous consequences (for example, heating and fire). The symbol “T” in the figure indicates a button that turns on the device testing circuit - the RCD-D should operate when it is pressed. The same principle is used for three-phase protection devices, however, in them, differential current in the secondary winding appears not only during leaks, but also during “phase imbalance” (load unevenly distributed between phases), therefore additional circuits have been developed that exclude operation due to a violation symmetry.

General scheme. Operating principle of RCD ( UZO-D)

How does an RCD work?

Let's consider How does a residual current device (RCD-D) work?with a clear example:

We have a two-wire electrical circuit 220V (without grounding), the end consumer of which is a washing machine. To protect against leakage currents, a residual current device is included in the circuit. In normal operation, it freely passes current through itself.

The outgoing current I1 and the returning current I2 are equal.

As a result of a malfunction of the electric motor, the body of the washing machine became energized.

An unsuspecting person touches the body of the machine, as a result of which he is exposed to electricity.

When a leakage current occurs, part of the current flows through the human body to the ground, and the returning current becomes less than the outgoing current. The residual current device is tripped.

The person is safe.

Having understood how the RCD works, you can come closer to understanding the principle of its operation.

The examples described above and in the figure show an RCD with an electromechanical actuator for opening the contacts. At the same time, there are no obstacles to the use of electronic components with semiconductor “switches”. Indeed, today there are many electronic protection devices offered, their cost is several times lower than electromechanical ones, the main disadvantages are that they do not operate when the supply voltage drops and lower reliability.

Standards

At the moment, a package of standards has been developed and adopted in Russia regulating the use, characteristics and testing methods of RCD-D. Their action extends to alternating current devices with a rated voltage of no higher than 440 V and a rated current of no more than 200 A, used to protect people and their property from electric shock from the consequences of leakage current development. GOST R 50807-95 (2001) contains definitions, classification, characteristics and a list of standard testing methods. It also contains complete lists of documents referenced by this standard. As for the rules of application, everything necessary is set out in GOST R-30331.3 (Protection against electric shock). These standards are consistent with international ones and contain a comprehensive amount of information on protection devices controlled by differential currents. Let us add that the GOST R 50807-95 (2001) standard does not classify all types of protective devices operating on the principle of differential current control as RCD-D. According to the definition of RCD-D, only mechanical switching devices or complexes are considered that open contacts when the differential current reaches a set value. The device can be implemented as a set of separate specialized units that record and measure diff. current and nodes that disconnect contacts. An example of such spatially separated RCD-D can be protection systems for overhead power lines. At the same time, numerous electronic products with semiconductor switches are not classified as standard RCD-D.

Classification of RCD (UZO-D)

Below is a classification of protection devices according to several important criteria; the information corresponds to GOST R 50807-95, but is presented in a more convenient and systematized form.

Classification UZO-D

According to the method of action:

1. No auxiliary power supply.
2. With auxiliary power supply:

From auto. shutdown in case of source failure with a time delay without it:

• with auto restart when the source is restored;
• without car restart when the source is restored;

Without car shutdown in case of source failure:

• with shutdown in a dangerous situation after a source failure;
• without shutting down in a dangerous situation after a source failure;

By installation method:

1. Stationary:

• installation with fixed electrical wiring

1. Portable:

• installation with flexible wires and extension cords

By number of poles:

• single-pole two-wire
• bipolar;
• two-pole three-wire;
• three-pole;
• three-pole four-wire
• four-pole

By type of protection against overcurrent and overcurrent poles:

• without built-in overcurrent protection;
• with built-in overcurrent protection;
• with built-in overload protection;
• with built-in short circuit protection.

If possible, regulate the disconnecting differential current:

1. Adjustable:

• discrete adjustment
• smooth adjustment

1. Unregulated.

In terms of resistance to impulse voltage:

• with the possibility of switching off during impulse voltage
• impulse voltage resistant

According to the characteristics of the presence of a constant component of the differential current:

1. AC type:

• shutdown when an alternating sinusoidal differential current appears or slowly increases.

1. type A:

Disconnection from residual currents:

• sinusoidal variables;
• pulsating constants;
• pulsating constants with ripple modulation up to 0.006 A, with or without phase shift control angle control, regardless of the polarity of sudden or slowly rising differential currents.

1. type B:

• disconnection from differential currents:
• sinusoidal variables;
• pulsating constants;
• pulsating constants with modulation by smoothed pulsation of direct current up to 0.006 A;
• constant from rectifiers

Each of the classification features - mode of action, installation method, etc. is used not only for classification, it is also considered the most important characteristic of an RCD-D. In addition to them, there are a number of characteristics common to all protection and shutdown devices.

RCD design

From a technical point of view, the design of the RCD-D is nothing complicated or new compared to the designs of automatic circuit breakers. Moreover, Russian manufacturers began and mastered the production of these products based on VA assault rifles. An example is the well-known UZO22 from the Signal plant, produced on the basis of the VA66-29 and VA88-29 circuit breakers. They have the mechanics of the free release, the coil, contacts, arc arresters - everything is the same as the VA. In more detail you can familiarize yourself with their design, operating principle and device in the article. The only difference is in the module controlled by differential current (MCO), the design and operation of which are described above. The same can be said about RCDs produced on the basis of foreign automatic machines.

RCD characteristics

The GOST R 50807-95 (2001) standard gives recommended or preferred values ​​for the characteristics of RCD-D, and manufacturers who want to certify their products in the GOST R system must adhere to these values, but they also have the right to produce products with other indicators (in this case they will not receive a certificate of conformity to GOST R 50807-95). A complete list of characteristics is available in the same GOST; only some of the main ones will be shown here. For the most important characteristics, the standard offers the following values.

Table 1

The tripping time of the RCD is determined by its design and depends on the values ​​of the rated current and the rated tripping differential. current GOST R 50807-95 contains the corresponding tables; as a guide, we will show the shutdown time of a device with a rated switching differential. current 0.030 A. With direct contact causing differential. current of the rated value, the device will operate in 0.5 s, with double excess of the rated value in 0.2 s, with differential. current 0.25 A (eight times the excess), the RCD-D will turn off in 0.04 s.

Application of RCD

Residual current devices (RCDs) are used to protect people from electric shock in industry, agriculture, everyday life, etc. Moreover, they cannot be considered as an alternative to other safety measures; moreover, the GOST R-30331.3 standard classifies them as auxiliary devices and additional methods of protection from direct contact. For these purposes, as well as for protection against indirect contacts in the Russian Federation, RCD-D with diff. shutdown current is about 30ms. Devices with large diff. current shutdowns are used to protect electrical equipment from the consequences of leakage currents (fires, equipment failure).

In our age of high technology, people are surrounded on all sides by a huge number of devices and devices that operate using electricity. And the greater their number, the higher the likelihood of electric shock to a person. To avoid this, the RCD was invented. What it is and what it is needed for, we will explain in detail in this article.

Purpose

Intended to protect a person from electric shock when touching the housing of electrical equipment (household electrical appliances), which became energized if the insulation was broken.

When the RCD trips

Let's continue the story about the RCD. What is it and how does it work? An electric current begins to flow through a person touching the energized body of an electrical device. When it reaches 30 mA, the RCD turns off. As a result, the voltage is automatically disconnected from the damaged equipment. In this case, the person does not feel anything, since painful sensations occur at much higher currents (from 50 mA). A current of 100 mA is fatal to humans.

What does an RCD consist of?

Includes current transformer, (relay and breaking lever system), self-test circuit. More advanced devices contain in their design a system that is electromagnetic and inversely dependent on the magnitude of the cutoff current (protection from and against overload).

Operating principle of RCD

What it is? How is this device powered? Now we will tell you about all this in as much detail as possible. The operation of the RCD is based on current (CT). The phase and working neutral conductors pass through the current transformer. With normally operating equipment (with intact insulation), the magnitudes of the currents flowing through them are equal in magnitude, but opposite in direction. As a result of this, they induce CTs in the winding, identical in size, but opposite in direction, which completely compensate each other (there is no voltage at the ends of the secondary winding of the CT). If the insulation of the equipment is broken, part of the phase conductor current flows to the ground through the grounding conductor (if the device body is grounded) or through a person who has touched this electrical device. As a result of this, the amount of current flowing through the neutral working conductor becomes less than that flowing through the phase conductor. This leads to the fact that the magnetic fluxes in the transformer winding become different in magnitude. As a result, voltage appears at the ends of the CT winding. Current begins to flow through the relay connected to them. When the difference in values ​​reaches 30 mA, a relay is activated, activating a system of breaking levers. The equipment turns off.

Turning on the RCD

It is carried out only after identifying and eliminating the fault in the electrical equipment that led to the operation of the device by pressing the cocking levers.

Conclusion

In this article, we introduced you to RCD in some detail: what it is, how it works and what it is used for. We hope you find this information useful.

Hello Dear reader of the site site. Today we’ll talk about RCDs for protecting people from leakage currents (residual current devices). RCD protection is installed in electrical networks to protect people from leakage currents and prevent fires.

Purpose

An RCD is an electrical device specially designed to cut off the power to electrical appliances during leakage currents. Leakage currents occur due to minor violations of the insulation of current-carrying phase conductors. If the insulation is broken, current begins to “flow” through the metal casings of electrical appliances or conductive structures of an apartment or house. Leakage current is also called differential current.

Since the leakage current is small in value, circuit breakers installed in the electrical network do not operate on it and do not turn off the power supply. Circuit breakers turn off the electrical network in the event of a short circuit in the network (touching a phase and neutral wire or two phase wires) or overload. Circuit breakers do not respond to small leakage currents.

Leakage current is a dangerous electrical fault for humans. For example, if you touch a conductor through which a current of 0.3 milliamps flows, you will feel an ant bite; with a current of 15 milliamps, it will be difficult to tear yourself away from the conductor, but it is still safe. This cannot be said about a current of 40 milliamps. When you “touch” such a leakage current, you are guaranteed to experience body and diaphragm convulsions, which is undoubtedly very life-threatening. RCDs are designed to protect people from leakage currents. Such devices must have a cut-off current of no more than 30 mA.

To protect the premises from fire, a general RCD is installed to protect people from leakage currents, with a cut-off current of 100 mA or 300 mA.

Installation standards

According to Russian standards, an RCD with a shutdown current of no more than 30 mA is installed for residential premises. The response time of the RCD, that is, the time from the appearance of leakage currents to the shutdown of the electrical circuit, should be in the range of 0.1-0.3 seconds; this shutdown time is sufficient to protect a person from death. But don’t think that with an RCD installed, you won’t feel the electric shock at all. There will be an electric shock, but the device must turn off the current in time and save your life.

I note that the same standards apply in Europe. In America, according to their National Electrical Code standard, RCDs installed in residential premises must have an operating current of 5 mA

Note: The serviceability of the device must be checked before installing the RCD, after installing the RCD, and every six months using the “Test” button on the case. If, when you press the “Test” button, the RCD works, that is, it turns off the network, then it is fully operational. If it doesn't work, it needs to be replaced.

Where is it necessary to install an RCD in the electrics of an apartment and house?

According to our regulatory documents, the RCD is an additional protection device. (PUE ed. 7, clause 1.7.50; clause 1.7.156).

Optional does not mean optional.

Installation of RCDs is carried out in all groups of the electrical circuit in which plug sockets are installed. The rated shutdown current of the device should be no more than 30 milliamps. At least one general Protective Disconnection Device for the entire apartment (house) must be installed.

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If you have an electrical network with many power supply groups, installing an RCD for each group together with a common RCD will only improve the safety of the living space. It is allowed to install one RCD on several separate power supply groups, provided that separate circuit breakers are installed on each group.

Selecting an RCD for human protection from leakage currents

The RCD has two main characteristics.

• Rated load current (in amperes)
• Rated cut-off current, also known as differential current (in milliamps).

RCD load current

The RCD must be installed in the electrical circuit together with overcurrent circuit breakers, after the circuit breaker. The rated operating load current of the device must be selected one point higher than the rating of the circuit breaker.

For example: Introductory circuit breaker for apartment 50 Ampere. This means that for the entire apartment, you need to install an RCD with a rated load current of 63 Amperes.

Rated cut-off current

for residential premises the rated cut-off current is selected:

• To protect people from leakage currents, an RCD with a cut-off current of 30 mA is installed;
• For wet areas (bathrooms) and children's rooms powered from a separate line, an RCD with a cut-off current of 10 mA is installed;
• To protect the house from fire, the cut-off current must be 100 mA or 300 mA;
• The choice of device is made on the basis of SP 31-110-2003.

Nominal cut-off time of RCD

• The nominal cut-off time should not exceed 0.2 milliseconds for a supply voltage of 230-400 Volts.
• In apartments and houses it is better to install an RCD of type "AC" or "A". Type "AC" reacts only to sinusoidal, alternating, leakage currents. Type "A" reacts to sinusoidal and pulsating leakage currents. Pulsating currents arise from the operation of tape recorders, televisions, washing machines, and lighting controls.

RCD installation

• The device is installed after overcurrent circuit breakers.
• It is recommended to install the device in such a way that the phase and neutral working conductors are disconnected at the same time. In this case, the installation of an overcurrent protection circuit breaker on the neutral wire is not necessary.
• Below shows the correct and incorrect connections of the device in the apartment and house.
• In the top diagram, the device is installed immediately after the electric meter, without a circuit breaker. This is unacceptable (PUE 7.1.76).

It is forbidden install human protection against leakage currents in group circuits where there is no protection against overcurrents. On the source side, you need to install an overcurrent protection circuit breaker (ECP) in front of it.

Regulations

In these regulatory documents you will find information about RCDs for protecting people from leakage currents.

• PUE (Rules for Electrical Installations) ed.7
• SP 31-110-2003, Design and installation of electrical installations
• GOST R 50571.8-94, ELECTRICAL INSTALLATIONS OF BUILDINGS, Part 4
• GOST R 50571.11-96, Electrical installations of buildings, Part 7, Requirements for special electrical installations.

A residual current device (RCD) is an electrical low-voltage device that is used to automatically disconnect the protected section of the electrical circuit in the event of a differential current exceeding the permissible value for this device. You can also come across such an abbreviation as VDT - this is a differential current switch, that is, actually the same thing. In this article, we will look at the readers about the device, purpose and operating principle of an RCD used in electrical engineering.

Purpose

First, let's look at the purpose of the residual current device (in the photo below you can see its appearance). occurs in the event of a violation of the integrity of the cable insulation of one of the electrical wiring lines or in the event of damage to structural elements in a household electrical appliance. A leak can lead to either an operating household electrical appliance, as well as electric shock during operation of a damaged electrical appliance or faulty electrical wiring.

In the event of an unwanted leakage, the RCD in a fraction of a second disconnects the damaged section of electrical wiring or a damaged electrical appliance, which protects people from electric shock and prevents the occurrence of a fire.

The question is very often asked about... The difference between the first one is that this protective device, in addition to protection against electrical leakage (RCD functions), additionally has protection against short circuits, that is, it performs the functions of a circuit breaker. The residual current device does not have overcurrent protection, so in addition to it, circuit breakers are installed in electrical networks to implement protection.

Device and principle of operation

Let's look at the design of the residual current device and how it works. The main structural elements of the RCD are a differential transformer that measures the leakage current, a trigger element that influences the shutdown mechanism and the power contact release mechanism itself.

The operating principle of an RCD in a single-phase network is as follows. The differential transformer of a single-phase protection device has three windings, one of which is connected to the neutral conductor, the second to the phase conductor, and the third is used to fix the difference current. The first and second windings are connected in such a way that the currents in them are opposite in direction. In normal operation of the electrical network, they are equal and induce magnetic fluxes in the magnetic circuit of the transformer, which are directed counter to each other. The total magnetic flux in this case is zero and, accordingly, there is no current in the third winding.

In the event of damage to an electrical appliance and the appearance of phase voltage on its body, when touching the metal body of the equipment, a person will be exposed to leakage of electricity that will flow through his body to the ground or to other conductive elements that have a different potential. In this case, the currents in the two windings of the differential transformer RCD will be different, and accordingly, magnetic fluxes of different magnitudes will be induced in the magnetic circuit. In turn, the resulting magnetic flux will be different from zero and will induce in the third a certain value of current - the so-called differential one. If it reaches the triggering threshold, the device will work. We described the main ones in a separate article.

More information about how the RCD works and what it consists of is described in the video lessons:

Do you want to know how a residual current device works in a three-phase network? The operating principle is similar to a single-phase device. The same differential transformer, but it already compares not one, but three phases and the neutral wire. That is, in a three-phase protective device (3P+N) there are five windings - three windings of phase conductors, a neutral conductor winding and a secondary winding, through which the presence of a leak is detected.

In addition to the above structural elements, a mandatory element of the residual current device is a testing mechanism, which is a resistor connected via the “TEST” button to one of the windings of the differential transformer. When you press this button, the resistor is connected to the winding, which creates a difference current and, accordingly, it appears at the output of the secondary third winding and, in fact, simulates the presence of a leak. Triggering of the residual current device indicates that it is in good condition.

Below is the symbol of the RCD in the diagram:

Application area

The residual current device is used to protect against current leakage in single-phase and three-phase electrical wiring for various purposes. In a home, an RCD must be installed to protect the most dangerous household electrical appliances from the point of view of electrical safety. Those electrical appliances, during the operation of which there is contact with metal parts of the housing either directly or through water or other objects. First of all, this is an electric oven, washing machine, water heater, dishwasher, etc.

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

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

In our article we will try to analyze in detail the design and principle of operation of RCDs, consider the existing varieties and understand what information the marking of residual current devices contains.

The RCD ground loop device is a PE conductor of neutral conductive housings or parts of electrical mechanisms with a resistance not exceeding 4 Ohms.

If a leakage current occurs, these equipment elements 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 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 disturbances in the circuit are invisible and, in rare cases, noticeable, when you can feel a slight electric shock when touching the device.

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

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

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

RCD design

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

Key operating units include:

• transformer differential sensor;
• trigger - 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 that have the opposite direction in relation to each other. Due to this, the magnetic flux is zero.

The transformer consists of a closed steel core, on which two coils are placed: the primary one is connected to the alternating current source, the secondary one is connected to the load. The number of times the transformer increases the AC voltage, the same number of times the current decreases

An electromagnetic type relay is connected to the secondary winding wound on the magnetic core of the transformer. If the network meets standard operating conditions, it is not activated.

When a current leak occurs, the entire operation changes dramatically. The phase and neutral conductors begin to pass different amounts of current. Now the power value and direction of the magnetic fluxes on the transformer core will also have different parameters.

A current appears in the secondary turns and when the specified values ​​are reached, the electromagnetic relay is activated. It is paired with a release mechanism. This connection reacts at the right moment and disconnects the electrical network.

According to fire safety requirements, control checks of the differential protection device are carried out regularly, at least once a month. For this purpose, the device has a special “TEST” button.

The testing unit is represented by a resistance mechanism - a certain load connected to bypass the differential sensor. This element simulates current leakage and thus checks the functionality of the device. We talked in more detail about verification methods.

The operating principle 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.

This creates conditions for different current indicators at the input and output of the device. This imbalance should lead to the startup of the shutdown unit.

Depending on the developers, the circuit design may vary, but the principle used in the operation of the RCD will be identical for all models.

The principle of operation of the protective mechanism

Let's consider why you need to use an RCD. The functioning of the protective device is based on a measuring method.

The incoming and outgoing parameters of the currents flowing through the transformer are recorded. If the first value is greater than the second, this means that there is a current leak in the electrical circuit and the device reproduces a shutdown. If the parameters are identical, the device does not work.

In a two-wire system, the differential device does not operate if a current of equal strength passes through the phase and neutral wires. If there is a difference in these values, it means there is an insulation breakdown in the network and the protective mechanism will turn off the damaged section

For a better understanding, let's consider how an RCD will work in a household distribution panel with a two-pole system.

The input two-wire wire (phase and neutral) is connected to the upper terminal blocks. Phase and neutral are connected to the lower terminal blocks, laid to the load area, for example, to the power outlet of a boiler or electric kettle. Protective grounding of the device will be carried out by cable, bypassing the RCD.

In standard operating mode, the movement of electrons is carried out along the line-phase from the incoming cable to the electric heater of the boiler/kettle, flowing through the differential protection device. They move back to the ground again through the RCD, but along the neutral line.

If a person touches the body of a current-carrying device, on which a potential has appeared due to a breakdown, in this situation the current leakage will pass through the human body, to which the device reacts almost instantly by turning off the power system

For example, the insulation in the heating element of the device was damaged. Thus, through the water inside, the current will be partially conducted by the housing, and then will go into the ground through the wiring of the protective device.

The remaining current will return along the neutral line through the RCD. However, its strength will become less by the amount of leakage compared to the incoming one.

The difference in indicators is calculated by a differential transformer. If the number is higher than allowed, the device instantly reacts and breaks the circuit.

The feasibility of using RCDs

Let's consider why you need to use an RCD and from what negative impact factors the device provides protection.

First of all, a phase short circuit to the electrical equipment housing. Mainly, problem areas include heating elements of heaters and washing machines. It is worth noting that breakdown occurs only when the heat-generating part is heated under the influence of 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 that will leak into the wall.

The differential protection mechanism in this case will constantly de-energize the line until the area 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 a large number of powered devices. The ideal option is when this type of device is installed on each group of sockets

The scope of application of survey devices is quite diverse - from public buildings to large-scale enterprises. They complete 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 to do it right.

Types of devices and their classification

Development companies endow their products with diverse capabilities, which must be taken into account when determining the required type of RCD, based on the specific operating conditions of the electrical network.

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

• operating principle;
• type of differential current;
• time delay of disconnecting 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 to the damaged line, regardless of the network 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 polarization relay, which leads to 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 a device with electronic filling completely depends on 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, so the circuit uses electricity from the external network to operate 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 an 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, it is 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 break in the zero phase has occurred, in addition to this, during the same period a malfunction occurs in the microwave wiring and a phase short circuit occurs to the housing, i.e. it has dangerous potential.

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

Classification #2 - by type of leakage current

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

The rated operating voltage is indicated on the housing 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 when an alternating leakage voltage instantly appears in the controlled circuit or when it increases in waves. These devices are marked with the inscription “AC” or the symbol “~”.

The most suitable form factor for domestic use is UZO-AS. The model is the cheapest of devices of similar action. In the passport for electrical engineering, manufacturers often indicate a specific model of 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 symbol is marked on the body of the machine, as in the graphic image in a rectangle.

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

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

This is expensive equipment intended for industrial facilities. They are not used in domestic conditions.

The presented tripping 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 distinguishes between two types: S and G. Type S automatic 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 group connection of an RCD.

Scheme of an apartment panel with two load groups, where two different types of protective devices are connected: AC or A, and S

According to the diagram, the panel contains two load groups in the form of sockets No. 1 and No. 2, to which a type A RCD is connected, and a second circuit breaker - 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 section.

Selectivity of circuit break activation can be achieved using another method - through leakage current settings. This method is most widespread.

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

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

There are situations when the differential current in the fault circuit exceeds the rated settings of the two protection devices. For the first circuit, selectivity will not be impaired, but in the second, any of the connected devices can supply the cutoff current.

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

Some RCD models have a system for adjusting the diforgan setting, others do not have this capability. However, the second version is suitable for domestic purposes.

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

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

To organize fire safety of buildings - 0.1-0.3 A. We recommend that you familiarize yourself with the tips and subtleties 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 current passing through it, the number of poles of the machine will be identical to the number of current-carrying lines.

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

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

However, this will not realize the full potential of the device, 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, an additional circuit breaker with a rated voltage no greater than the operating current of the safety system is installed

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

Since differential protective devices come in a variety of housings, they can be used as stationary or portable.

In the second case, the device is equipped with an extension cord. Devices that are fixed on a DIN rail, which is placed 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 device connected through such a mechanism does not pose a danger to humans if it breaks down.

Full decoding of marking values

The name of the developer company must be on the device body. This is followed by standardized markings indicating the serial number.

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

• [F]– residual current device;
• [X]– performance format;
• 00 – digital or alphanumeric designations of the series;
• [X]– number of poles: 2 or 4;
• – characteristics by type of leakage current: AC, A and B.

The nominal parameters of the device will also be indicated here, which you need to pay special attention to when choosing.

Explanation of the abbreviation: 1 – brand; 2 – device type; 3 – selective species; 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 – electrical diagram; 10 – manual performance check; 11 – switch position marking

The maximum parameters for which the devices are designed include: voltage Un, current In, differential value of circuit opening current IΔn, ability to turn on and off I'm switching capacity during short circuits Icn.

The main markings must be located in such a way that they remain visible after installation of the device. Some parameters may be marked on the side or on the rear panel, visible only before installation of the product.

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

Not every product is marked with optimal environmental temperature indicators. In those models where there is a symbol, this means that the operating range is from -25 to + 40 °C; if there are no symbols, this means standard indicators from -5 to +40 °C.

The use of an RCD is a profitable and correct solution not only from the point of view of economy, but, from the point of view of fire safety, and human protection.

Do you still have questions about the operating principle or classification of residual current devices? Or do you want to supplement the presented material 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 thoroughly as possible.