RCD (device protective shutdown) are connected according to different schemes. You will not make a mistake if you first figure out for yourself how not to connect it.

The connection is as follows:

when the RCD is installed immediately after the meter NOT CORRECT.

A circuit breaker (AB) must always be installed in front of the device.

An exception can only be the installation of a differential automaton (BP) instead of an RCD.

Such a connection scheme has its drawback - in the event of a current leakage at one of the consumers (washing machine, electric stove, electric kettle ...), the protection will work and turn off the power to the entire apartment, which is not very convenient. And it will not be possible to apply voltage, even for lighting, until the malfunction is completely eliminated. And imagine that the breakdown occurred at night ... Repair will be very difficult.

When I take an apartment for repairs, I suggest that my customers install an RCD on each individual consumer line (washing machine, boiler, electric stove, socket group, bathroom power, heated floors ...). And, for example, only automatic switches should be installed for lighting and air conditioning.

The connection diagram looks like this:

This option is an order of magnitude more expensive than usual and an increased number of devices may not fit in the switchboard, but you have to pay for comfort and safety. And you can save space in the shield if instead of circuit breaker with RCD install differential. machine. It takes up less space, and performs the same functions as AV and RCD combined.

Using the connection of a residual current device (RCD) in world practice is a popular condition for enhancing the safety of electricity consumers. The number of people whose lives were saved by the RCD installation is difficult to count. The use of this device in the power supply lines of high-rise buildings and country cottages prevents fires and emergencies.

What is a security connection device

Electricity- directed movement of charged particles, which is not visually manifested, there are no signs of danger even in the presence of grounding. Effects negative impact charge on the human body appear instantly, are of varying severity, up to death.

The method of using ouzo is still interpreted in two ways: the installation of switching equipment is not provided for in the protection circuit of the conductor of electricity. The wording changed periodically, but the meaning remained unchanged: it is forbidden to install, but they are switching devices. By opening the electrical circuit with grounding, the ouzo simultaneously prevents damage to the protective device when the power is turned off.

The first application of ouzo is a relay protection circuit for power lines by cutting off electricity in the event of an accident when a leakage current is triggered. Then the area of ​​connection expanded to protect the safety of individual objects of electrical equipment. According to the working diagram, two contacts are provided on the ouzo, the method of operation of this device does not provide for the mandatory connection of grounding.

RCD tasks

When installing an electrical network with grounding, the main task of the RCD is taken into account - increasing the degree of safety in case of fire under the action of leakage currents or a short circuit in the electrical network. In this case, the insufficiency of the current strength to ensure automatic shutdown increases.

The next task is the need to guarantee the safety of users in the event of a direct threat of electric shock in the event of:

• careless handling of bare wires;
• use of electrical appliances with broken insulation.

The design and outer appearance of the RCD does not differ from the usual circuit breakers. The scope of these devices extends to the types of electric current network, regardless of the number of working phases. When creating unforeseen emergencies, the RCDs operate automatically, de-energizing the damaged electrical network.

The only difference in work is the reaction to the level of leakage current, while other automation reacts to the occurrence short circuit in damaged single-phase network or a sharp jump in the overload current.

For reliable control over the functionality of electrical networks, the installation diagram suggests placing the RCD together with automatic fuses, placing it in series in the circuit in order to protect against the damaging effects of sudden current surges at the time of emergencies. The stores offer residual current devices for functionality with leakage current:

• 10mA;
• 30mA;
• 100mA;
• 300mA.

In the case of connecting the RCD as suggested by the working diagram, three conductors must be present:

• phase;
• zero;
• grounding.

To connect the normal functionality of the automatic fuse, the network is enough in the "phase-zero" mode. In this case, the "grounding - conductor" circuit is triggered - the "excess" voltage is removed at the moment of a surge of electric current during an accident.

The principle of constructing an RCD connection diagram

For the correct operation of this protective device in each individual case, the connection scheme to the electrical network should be developed separately. According to professional electricians, the likely place to connect an ouzo in a residential apartment is either country house considered a point in the immediate vicinity of the source of electricity. For qualified work, these devices are used simultaneously with circuit breakers, installed in series. Installation of the electric current network is carried out according to two schemes.

1. Scheme 1. If desired, connect one protective device to a common power line, the negative point in this situation is the shutdown of the network when an emergency is created at one of the sites. In this case, the search for the damaged zone will be delayed for a long time.
2. Scheme 2. If it is possible to connect the ouzo on each specific network line individually, in the event of an emergency, energy will be supplied to a separately taken damaged section. Electricity continues to flow into the remaining single-phase network, all appliances and equipment will continue to function as usual. This scheme requires an increase financial costs but these costs are undeniably justified.

Each ouzo connection scheme in a single-phase network requires a serious attitude during installation and further operation.

Variations of household RCDs

With the development of electronics, the work of which is based on semiconductor devices, RCDs are constantly being improved. To protect the consumer from electric shock, household appliances have been developed that operate according to the capacitance relay method and respond to surges. capacitive currents offset.

RCD-E is different:

• increased degree of sensitivity;
• instant response in the event of an accident;
• work without grounding.

A negative point in the functionality of this device is the reaction directly to the manifestation of leakage current, regardless of the source of occurrence. The scope of protective RCD-E is very limited - special equipment in the presence of touch indicators.

When reconstructing the principles of operation of the RCD-E, a protective device was developed that is triggered by a difference in the balance of power conductors. This RCD is called "differential". If you connect the RCD-D in a single-phase electrical network with grounding, the data on the value of the electric current on the phase and zero are fixed, when working with a three-phase electrical network, three directions of current and grounding are taken into account. The specifics of drawing up a diagram and subsequent installation consider the unprofitability of connecting conductors that do not have power, due to possible errors in the operation of the entire network.

It is better to connect differentiated electromechanical RCD-DM, which enjoy reliable popularity. The reliability of this device made it possible to combine in one case directly the RCD and the circuit breaker, which guarantees the complete safety of consumers.

Conclusion

The main condition for connecting an ouzo in an electrical network is a circuit where the position is after the circuit breakers, which is considered a guarantee of protection against surges of the electric current consumption meter and the protection device itself. A breakdown of this device occurs when the value of a single-phase electric current of operating parameters is exceeded. To avoid problems, you need to connect an automatic machine with a rating not exceeding the operating current of the ouzo. If connected incorrectly, the protection device will not be able to function!

It will protect the wiring in a private house or apartment from leakage currents, but at the same time it will not protect the wires from short circuits and overloads of the electrical network. That is why this product is installed together with a circuit breaker. Next, we will look at how to correctly make a diagram for connecting a single-phase RCD to a network with and without grounding!

It is best to install the product after electric meter, but in front of the machine.

For your attention 4 typical schemes RCD connection in a single-phase network.

Connection of one common RCBO:

Installation diagram of several residual current devices for each group:

Connection of several residual current devices together with an introductory RCBO:

Installation in a two-wire network (without grounding):

Please note that you need to connect the device from above, the last picture is provided only for clarity, so that you understand how the RCD is mounted in a network without a grounding conductor. Also note that each of the options has the following sequence of connecting elements: introductory machine - counter - RCD. Such a scheme protects your wiring as much as possible from all types of threats.

• If the wiring in a private house or apartment will include more than one powerful electrical appliance, then it is better to install a separate residual current device for each group of conductors. This option will allow you to control each device separately and, in turn, in case of malfunctions, turn off the electricity not in the entire electrical network, but only in a certain place.
• If the power grid is simple, without a powerful household appliances, it is better to use . This device simultaneously protects the network not only from leakage currents, but also from short circuits along with overloads (AB functions).

The video below clearly discusses the provided installation options for the residual current circuit breaker, and also explains where each of the connection methods is rational.

This article discusses the issue of connecting an RCD to a two-wire network, without grounding. 2 basic installation schemes, 5 main mistakes in the operation of the product.

TEST:

1. Is it possible to install an RCD in a two-wire network?

1. Is it necessary to ground the protective device?

1. Are 2 or more products installed in two-phase network?

1. Is it possible to cascade the protection relay?

1. Are the ground and neutral wires connected in the outlet?

Answers:

1-A, 2-B, 3-A, 4-A. 5 B.

RCD- an abbreviation for a device for protective shutdown of electricity. Its use in the power grid ensures the safety of the use of the power system for the user.

Protection is installed in a single-phase network without grounding? Answer: yes! For the safe operation of this devices grounding is not required. This is determined by the connection diagram of the product located on its body. Consider the principle of operation and the inclusion of the device in the power system.

Connecting the device to the network must be carried out in accordance with the scheme, otherwise the correct operation of the product and the safety of its use are not guaranteed.

2 connection steps in a single-phase network

We install the product and look at 2 photos with an example. On the corps there are input and output terminals - "zero" and "phase". At the bottom there are output terminals for fixing the corresponding user wires. The placement of the connection elements is standard for electrical appliances, the input contact sockets are on top, the output connectors are on the bottom. The purpose of the terminals is indicated on the case by the letters L and N. The N (zero) terminal is one, from 2 to 6 terminals is L (phase). There is a button on the front panel TEST and control indicator light.

The photo below shows the product with the cover removed. The cover schematically shows the connection of the device to the network. Above and below are groups of terminals for connecting wires. The wires are fixed in the sockets of the connectors with screws.

2 important points - how to connect the machines in the shield and the protection device without a ground wire

The product can be installed directly into shield, if there is free space on the tire for mounting it. The connection is made according to the diagram on the device case.

The photo above shows 2 interesting points:

1. The wire in blue insulation "zero" goes to the terminal block, and then to the consumer contacts.
2. The red wire - "phase" is connected to the group of automatic switches, and to the consumer of electricity.

Pay attention to 2 important elements on scheme. Grounding is carried out through the bus and brought directly to current-carrying cable. wires "zero" distributed through the terminal block.

2 answers about protection without grounding

Often the question arises about the possibility of installing an RCD in a two-wire network without grounding? The grounding connection in this case is carried out in addition to the protection device.

It is worth dwelling in more detail on determining the installation scheme of the product. One or more protection devices? But in this case, you need to focus specifically on the capabilities and parameters of the power grid itself. In some cases, a scheme with one device will be the most optimal. But with a large number of consumers or for increased fire safety, a step circuit or the connection of several protective devices will be required.

3 factors that determine whether a product works without grounding or not

The correct choice of the switching circuit in net is the main factor affecting the performance of the product. The bare ends of the wire in the terminals are securely fixed. It is important to connect the wires to the connectors intended for them, indicated by the letters on the case. devices. It is important to consider the following factors:

1. Understanding how it works. This is necessary to select the scheme for connecting to the power grid.
2. Selecting a device by its technical specifications, in accordance with the parameters of the power grid.
3. Inclusion of the device in a two-wire network without grounding requires the mandatory installation of circuit breakers.

The installation work of the product is carried out with a de-energized network, after connecting it is necessary to check whether the installation is correct. For this, the device has test and indication functions. Button TEST will help you check if the device is connected correctly.

When installing electrical appliances, observe safety precautions!

2 points of operation in a two-wire network without grounding

In a two-wire network, only two wires pass through the device: “zero” and “phase”. RCD monitors and compares current parameters on both. When a malfunction occurs in electrical networks current parameters change. After changes in the current value, the contacts open, disconnecting the damaged area.

Protection will not work in case of breakdown and phase contact with the case and in case of current leakage with voltage below the threshold value. Protection operation occurs only after the network is closed.

For example, in a working washing machine, the insulation of one of the current-carrying wires, and this area is in contact with the body. Metal corps The washing machine conducts electricity, so approaching it becomes potentially dangerous, not to mention touching it. If you come into contact with its body, you are at risk of electric shock. It is at this moment that the protection opens the contact, disconnecting the damaged area and protecting the user from injury. For this reason, setting the protection in single-phase power supply is mandatory, it is this product that, if necessary, will protect you from injury.

2 ways to connect a washing machine without grounding using UZO

In the first case, it is used differential machine, the use of the circuit breaker itself in this case is not necessary. The differential machine combines its functions and protection. But at the same time, the cost of such equipment is slightly more than RCD.

Differential machine

The second option would be to install protection and a circuit breaker, in which case the electrical equipment will take up more space, be more cumbersome, but the cost of such scheme much lower.

The example shows the connection RCD without grounding for washing machine. The legend on the diagram clearly shows how to connect it.

5 errors when connecting UZ O to a single-phase network

What threatens errors when connecting and operating the protection device? This is the failure to fulfill their tasks, the lack of response to damage in the network and periodic false shutdowns of its sections.

Errors when turning on the device in the power grid will be:

1. Output wire connection "zero" with ground wire.
2. "Phase" and "zero" must be connected through the terminals of the product, the output of "zero" in addition to the RCD will lead to periodic trips protection.
3. It is impossible to include jumpers between groups of contacts "zero" of different consumers with separate protective devices in the network.
4. Connecting wires to terminals not intended for them, “phase” - L, “zero” - N.
5. After disconnecting a section of the electrical network, it is necessary to eliminate the malfunction that caused the shutdown, and not turn it on RCD again.

The list is not complete, only the main mistakes made when connecting the device to the network and its operation are indicated here. Connection errors are described in more detail in the video.

RCD connection errors

Do not forget to test the devices during their installation, in the future, with wires embedded in the walls, wiring and junction boxes work will be difficult.

2 schemes how to connect the U.Z.O. without grounding in the apartment

The answer to the question will it work RCD without grounding in the apartment, quite complicated. Answering it is much more difficult than establishing it. This is due to the fact that the apartments use both wiring with and without grounding. Often without grounding there is wiring in old houses.

In such apartments, connection protection does not cause any particular difficulties, it is only necessary to choose the most preferred installation scheme. Will there be one product for all consumers or several devices, with distribution of protection. The first scheme is simpler, you need to install one RCD and connect it to the circuit breakers. The second scheme is more difficult to implement, but more preferable in terms of security. Her virtues:

• it is easier to find a fault in a separate section of the network than to examine the entire power grid for breakdown or damage;
• at emergency shutdown site, the rest of the power supply system continues to function.

The scheme with one product remains the most common for an apartment.

Washing machine connection.

If you replace the washing machine with a water heater, then the circuit will not change fundamentally. The only element that is changed in this circuit will be the current consumer. This is the answer to the question - how to connect protection without grounding to the water heater or hob.

It is impossible to combine “zero” and grounding into one, in sockets and junction boxes, this can lead to a network shutdown when a load is received. More about this in the video.

How not to do it. Dangerous Ways grounding.

The task of the introductory devices- this is the protection of the system from the occurrence of a fire in the event of a short circuit, it can work both for an individual consumer, and for the total value of the jump in loads from several.

How to connect RCD without grounding to boiler? Boiler- an energy-intensive unit, in addition, dangerous in terms of malfunctions. For this reason, it is recommended mandatory installation protection devices on the network section with it. The installation scheme does not differ from the standard one. Inclusion in the power supply network after the automatic switch-off. AT two-wire networks to the product fit "phase" and "zero", the ground wire is passed in addition to the device.

3 main protection parameters - UZO without grounding in the country

Separately, you need to consider the connection protection in the energy system of a country house. In this case, the loads are small, since the number of consumers is small, therefore, as a fire-fighting device, it is enough to install a universal RCD for 25-40A, depending on the load. Scheme connection in the country without grounding does not differ from the scheme mounting in an apartment or house. The only difference is technical parameters equipment. For country house characteristic:

• low power consumption;
• a small number of consumers;
• increased fire safety equipment.

Herself scheme does not differ from the above. The output of the "phase" from the product to the circuit breakers, "zero" on terminal box with further distribution to consumers. Ground is connected to the input cable directly.

5 frequently asked questions

The main question that arises when studying the topic is whether the operation of the RCD is possible in a two-phase network? Answer: yes, you can operate the device without grounding. The details are discussed above. Modernization of the power grid in large volumes is not required.

The second question is, what is protection for? The residual current device ensures the safety of the consumer by disconnecting a section of the electrical network. It is necessary, moreover, protection must be installed in a dangerous area.

Do you connect the RCD with your own hands or do you need the help of a professional electrician? Yes, you can install electrical equipment with your own hands. But, if you are not confident in your abilities in the calculation of characteristics or installation, it is worth inviting electricians.

Are electrical wiring errors dangerous? Yes, at best they will lead to false network outages, at worst, to a malfunction of electricity consumers or to injury to the user.

How to choose an RCD? To do this, you need to understand the principle of its operation, and the parameters of your electrical network. Based on these parameters, the type of product and its connection scheme are selected.

Connecting an RCD (residual current device) is a generally accepted measure in world practice to improve the electrical safety of consumers. The number of human lives saved by RCDs goes into the millions, and the use of RCDs in the power supply networks of multi-apartment and private residential buildings, residential areas and industrial facilities prevents billions of damage from fires and accidents.

But Galen's rule: "Everything is poison and everything is medicine" is true not only in medicine. Outwardly simple, RCD with thoughtless or careless use can not only prevent nothing, but also become a source of trouble. By analogy: someone built Kizhi with one ax, someone can build some kind of hut with them, but you can’t give someone an ax in their hands, they will chop off something for themselves. So let's get acquainted with the RCD in more detail.

Primarily

Any serious conversation about electricity is sure to touch on electrical safety rules, and for good reason. Electric current does not carry visible signs of danger, its effect on the human body develops instantly, and the consequences can be long and severe.

But in this case, we are not talking about general rules the production of electrical work, which are already well known, but about something else: RCDs fit very poorly into the old Soviet TN-C power supply system, in which the protective conductor is combined with neutral. For a long time it was not clear whether it fits at all.

All editions of the PUE unequivocally require: it is prohibited to install switching devices in the circuits of protective conductors. The wording and numbering of the paragraphs changed from edition to edition, but the essence is clear, as they say, even to the marabou bird. But what about the recommendations for the use of residual current devices? They are switching devices, and at the same time they are included in the gap of both the phase and ZERO, which is also a protective conductor?

Finally, in the 7th current edition of the PUE (PUE-7A; Electrical Installation Rules (PUE), 7th edition, with additions and changes, M. 2012), clause 7.1.80 still dotted the i: “It is not allowed to apply RCDs responding to differential current in four-wire three-phase circuits(TN-C system)." Such a tightening was caused, contrary to previous recommendations, by recorded cases of electrical injuries WHEN ACTIVATED RCD.

Electric shock due to incorrect connection of the RCD

Let's explain with an example: The hostess was washing, in the car it hit the heater body, as shown in the figure with a yellow arrow. Since the current distributes 220 V along the entire length of the heating element, something around 50 V will appear on the case.

This is where the following factor comes into play: electrical resistance the human body, like any ionic conductor, depends on the applied voltage. With its increase, the resistance of a person falls, and vice versa. Say, the PTB provides an absolutely reasonable calculated value of 1000 ohms (1 kOhm), with sweaty steamed skin or in a state of intoxication. But then, at 12 V, the current should be 12 mA, and this is more than the non-releasing (convulsive) current of 10 mA. Has anyone ever been hit by 12 volts? Even drunk in a saltwater jacuzzi? On the contrary, according to the same PTB 12 V is an absolutely safe voltage.

At 50-60 V on wet steamed skin, the current will not exceed 7-8 mA. This is a strong, painful blow, but the current is less than convulsive. You may need treatment for the consequences, but it will not come to resuscitation with defibrillation.

And now let's "defend" the RCD, not understanding the essence of the matter. Its contacts do not open instantly, but within 0.02 s (20 ms), and not absolutely synchronously. With a probability of 0.5, the ZERO contact will open first. Then, figuratively speaking, the potential reservoir of the heating element at the speed of light (literally) will be filled up to 220 V along its entire length, and 220 V will appear on the body, and the current through the body will pass 220 mA (red arrow in the figure). Less than 20ms, but 220mA is more than two instant killing 100mA values.

So, why not install RCDs in old houses? Still, it is possible, but carefully, with a full understanding of the matter. You need to choose the right RCD and connect it correctly. How? This will be discussed further in the relevant sections.

RCD - what and how

RCDs in electrics appeared simultaneously with the first power lines in the form of relay protection. The purpose of all RCDs remains unchanged to this day: to turn off the power supply in the event of an emergency. As an indicator of an accident, the vast majority of RCDs (and all household RCDs) use leakage current - when it rises above a predetermined limit, the RCD trips and opens the power supply circuit.

Then RCDs began to be used to protect against breakdown and fire of individual electrical installations. For the time being, for the time being, the RCDs remained “fireproof”, they responded to a current that excluded the ignition of an arc between the wires, less than 1 A. “Fire” RCDs are produced and used to this day.

Video: what is RCD?

RCD-E (capacitive)

With the development of semiconductor electronics, attempts began to create household RCDs designed to protect a person from electric shock. They worked on the principle of a capacitive relay reacting to a reactive (capacitive) bias current; while the person works as an antenna. The well-known indicator-phase indicator with neon is built on the same principle.

RCDs-E have exceptionally high sensitivity (fractions of µA), can be made almost instantly triggered and are absolutely indifferent to grounding: a child standing on an insulating floor and reaching out with his finger to the phase in the socket will not feel anything, and RCD-E will “smell” him and turn off the power until he removes his finger.

But RCDs-E have a fundamental drawback: in them, the flow of leakage current electrons (conduction current) is a consequence of the occurrence of an electromagnetic field, and not its cause, therefore they are extremely sensitive to interference. There is no theoretical possibility to “teach” UZO-E to distinguish between a little hustler who has picked up an “interesting little thing” from a tram that has sparkled on the street. Therefore, UZO-E are used only occasionally to protect special equipment, combining their direct duties with a touch indication.

UZO-D (differential)

Having “turned” the RCD-E “on the contrary”, it was possible to find the principle of operation of the “smart” RCD: you need to go directly from the primary electron flow, and determine the leakage by the unbalance (difference) of the total currents in the POWER conductors. If exactly the same amount flows from the consumer as it went to him, everything is in order. If there is an imbalance, it is leaking somewhere, you need to turn it off.

The difference in Latin is differentia, in English difference, therefore such RCDs were called differential, RCD-D. In a single-phase network, it is enough to compare the magnitudes (modules) of currents in the phase wire and neutral, and when an RCD is connected in a three-phase network, the full vectors of currents of all three phases and neutral. An essential feature of the RCD-D is that in any power supply circuit, the protective and other conductors that do not transmit power to the consumer must pass by the RCD, otherwise false alarms are inevitable.

It took quite a long time to create household RCDs. Firstly, it was necessary to accurately determine the value of the unbalance current, which is safe for a person with an exposure time equal to the RCD operation time. RCDs tuned to an imperceptible or smaller non-letting current turned out to be large, complex, expensive, and pickups “caught” only slightly worse than RCDs.

Secondly, it was necessary to develop high-coercivity ferromagnetic materials for differential transformers, see below. The radio ferrite was not suitable at all, it did not hold the working induction, and the UZO-D with iron transformers turned out to be too slow: the own time constant of even a small iron transformer can reach 0.5-1 s.

UZO-DM

The principle of operation of a differential electromechanical RCD

By the 80s, the research was successfully completed: the current, according to experiments on volunteers, was chosen to be 30 mA, and high-speed differential transformers on ferrite with a saturation induction of 0.5 T (Tesla) allowed secondary winding remove power sufficient to directly drive the opening solenoid. Differential electromechanical UZO-DM appeared in everyday life. Currently, this is the most common type of household RCD, so DM is omitted, and they simply say or write RCD.

Differential electromechanical RCD works like this, see the figure on the right:

The appearance with explanations of the designations on the case of a three-phase and single-phase RCD is shown in the figure above.

Note: using the “Test” button, the RCD is supposed to be checked monthly and every time it is turned on again.

An electromechanical RCD only protects against leakage, but its simplicity and "oak" reliability made it possible to combine an RCD and a current circuit breaker in one case. To do this, it was only necessary to make the breaker latch rod double and bring it into the current and RCD electromagnets. So there was a differential machine that provides complete consumer protection.

Appearance of difavtomat (left) and RCD (right)

However, the difavtomat is not an RCD and an automatic machine separately, this should be clearly remembered. External differences (power lever, instead of a flag or a re-enable button), as shown in the figure, are only appearance. An important difference between an RCD and a differential machine affects the installation of an RCD in power supply systems without protective earth(TN-C, self-contained power supply), see section below on connecting an RCD without earth.

Important: a separate RCD is designed to protect against leakage ONLY. Its rated current shows to what extent the RCD remains operational. RCDs for ratings of 6.3 and 160 A with the same unbalance of 30 mA give the same degree of protection. In difautomatic machines, the cutoff current of the machine is always less than the rated current of the RCD, so that the RCD does not burn out when the network is overloaded.

In this case, "E" does not mean capacity, but electronics. UZO-DE are built directly into the socket or electrical installation. The difference in currents in them is captured by a semiconductor magnetically sensitive sensor (Hall sensor or magnetodiode), its signal is processed by a microprocessor, and the circuit opens the thyristor. UZO-DE, in addition to compactness, have the following advantages:

• High sensitivity, comparable to UZO-E, combined with the noise immunity of UZO-DM.
• As a result of high sensitivity, the ability to respond to bias current, i.e., RCD-DE proactive, will turn off the voltage before it hits someone, regardless of the presence of grounding.
• High speed: for the "buildup" of the RCD-DM, at least one half-cycle of 50 Hz is required, i.e. 20 ms, and at least one dangerous half-wave must pass through the body for the RCD-DM to work. RCD-DE is able to operate at a “breakdown” half-wave voltage of 6-30 V and cut it off in the bud.

The disadvantages of RCD-DE are primarily high cost, own power consumption (negligible, but when the mains voltage drops, RCD-DE may not work) and a tendency to failure - electronics after all. Abroad, chipped sockets were widely distributed back in the 80s; in some countries their use in children's rooms and institutions is required by law.

We UZO-DE are still little known, but in vain. The bickering between mom and dad about the cost of a socket with "fool protection" is not comparable to the price of a child's life, even if an incorrigible vermin and troublemaker run amok in the apartment.

UZO-D indices

Depending on the device and purpose, main and additional indices can be added to the name of the RCD. According to the indices, you can make a preliminary selection of the RCD for the apartment. Main indices:

• AC - are triggered by the unbalance of the variable component of the current. As a rule, they are fire-fighting, for an unbalance of 100 mA, because cannot protect against short-term impulse leakage. Inexpensive and very reliable.
• A - react to the unbalance of both alternating and pulsating currents. The main version is protective for 30 mA unbalance. False trips/failures are possible in the TN-C system in any case, and in the TN-C-S with poor grounding and / or the presence of powerful consumers with significant intrinsic reactivity and / or impulse blocks power supply (UPS): washing machine, air conditioning, hob, electric oven, food processor; to a lesser extent - dishwasher, computer, home theater.
• B - react to leakage current of any kind. These are either industrial RCDs of the "fire" type for 100 mA of unbalance, or built-in RCDs-DE.

Additional indices give an idea of ​​the additional functionality of the RCD:

• S - selective in response time, it is adjustable within 0.005-1 s. The main area of ​​application is in the power supply of objects powered by two beams (feeders) with an automatic transfer switch (ATS). Adjustment of the response time is necessary so that when the main beam fails, the AVR has time to work. In everyday life, they are sometimes used in elite cottage settlements or mansions. All selective RCDs are fire, for an unbalance of 100 mA, and require the installation of protective 30 mA RCDs after them for a lower current, see below.
• G - high-speed and ultra-high-speed RCDs with a response time of 0.005 s or less. They are used in children's, educational, medical institutions and in other cases when the "overshoot" of at least one striking half-wave is unacceptable. Exclusively electronic.

Note: household RCDs are most often not indexed, but differ in design and unbalance current: electromechanical for 100 mA - AC, they are also for 30 mA - A, built-in electronic - B.

Almost unknown to non-specialists, a type of RCD is not differential, triggered by current in a protective conductor (P, PE). They are used in industry, in military equipment and in other cases when the consumer creates strong interference and / or has its own reactivity that can “confuse” even UZO-DM. They can be both electromechanical and electronic. Sensitivity and speed for domestic conditions are unsatisfactory. A high quality serviced ground is required.

RCD selection

To choose the right RCD, the index is not enough. You also need to find out the following:

• Buy separately RCD with automatic or difavtomat?
• Select or calculate the cutoff value for extra current (overload);
• Determine the rated (working) current of the RCD;
• Determine the required leakage current - 30 or 100 mA;
• If it turned out that for general protection you need a "fire" RCD for 100 mA, determine how many, where and what kind of secondary "life" RCDs for 30 mA are required.

Separately or together?

In an apartment with TN-C wiring, you can forget about the difavtomat: the PUE prohibits, but ignore it, so the electricity itself will soon remind you. In the TN-C-S system, the difavtomat will cost less than two separate devices if the wiring is planned to be reconstructed. If the current machine is already standing, then a separate RCD that is coordinated with it in terms of operating current will be cheaper. Scriptures on the topic: RCD is incompatible with a conventional machine gun - an amateurish nonsense.

What overload to expect?

The cutoff current of the machine (extractors) is equal to the maximum allowable current consumption of the apartment (house), multiplied by 1.25 and added to the nearest higher value from the standard series of currents 1, 2, 3, 4, 5, 6.3, 8, 10, 13, 16 , 20, 25, 32, 35, 40, 50, 63, 80, 100, 125, 160, 250, 400, 630, 1000, 1600, 2500, 4000 and 6300 A.

The maximum current consumption of the apartment must be recorded in its data sheet. If not, you can find out in the organization operating the building (obliged to report by law). In old houses and new budget ones, the maximum allowable current is usually 16 A; in new ordinary (family) - 25 A, in business class - 32 or 50 A, and in suites - 63 or 100 A.

For private households, the maximum current is calculated according to the power consumption limit from the data sheet (the authorities will not miss it) at the rate of 5 A per kilowatt, with a factor of 1.25 and in addition to the nearest higher standard value. If the value of the maximum current consumption is directly stated in the data sheet, it is taken as the basis for the calculation. Conscientious designers on the wiring plan directly indicate the cut-off current of the main machine, so there is no need to count.

Rated current RCD

The rated (working) current of the RCD is taken one step higher than the cut-off current. If a difavtomat is installed, it is chosen BY THE CUT-OFF CURRENT, and the current rating of the RCD is inherent in it constructively.

Video: RCD or difavtomat?

leakage current and general scheme protection

For an apartment with TN-C-S wiring, it will not be a mistake to take an RCD for an unbalance of 30 mA without much thought. A separate section will be further devoted to the TN-C apartment system, but clear and final recommendations cannot be immediately given for private houses.

According to paragraph 7.1.83 of the PUE, the operating (natural) leakage current should not exceed 1/3 of the RCD unbalance current. But in a house with electric underfloor heating in the hallway, courtyard lighting and electric heating of the garage in winter, the operating leakage current can reach 20-25 mA with a living area of ​​both 60 and 300 squares.

In general, if there is no greenhouse with electric heating of the soil, a heated water well, and the yard is illuminated by the housekeepers, at the input after the meter it is enough to put a fire RCD with rated current one step higher than the cut-off current of the machine, and for each consumer group - a protective RCD with the same rated current. But only a specialist in the results can make an accurate calculation. electrical measurements already finished wiring.

The first is a new apartment with TN-C-S wiring; according to the data sheet, the power consumption limit is 6 kW (30 A). We check the machine - it costs 40 A, everything is OK. We take the RCD a step or two higher in terms of rated current - 50 or 63 A, it doesn’t matter - and for an unbalance current of 30 mA. We don’t think about leakage current: builders should provide it within the normal range, but if not, then let them fix it themselves for free. However, contractors do not allow such punctures - they know what the replacement of electrical wiring under warranty smells like.

Second. Khrushchev, plugs for 16 A. We put the washing machine on 3 kW; the current consumption is about 15 A. To protect it (and protect it from it), you need an RCD with a rating of 20 or 25 A for 30 mA of unbalance, but 20 A RCDs are rarely on sale. We take an RCD for 25 A, but in any case, it is MANDATORY to remove the plugs, and put a 32 A machine in their place, otherwise the situation described at the beginning is possible. If the wiring clearly cannot withstand a short-term surge of 32 A, nothing can be done, you need to change it.

In any case, you need to submit an application to the energy service for the replacement of the meter and the reconstruction of the electrical wiring, with or without replacement. This procedure is not very complicated and troublesome, and a new meter with an indication of the status of the wiring will serve you well in the future, see the section on trips and malfunctions. And the RCD registered during the reconstruction will then allow free-of-charge calls for electricians for measurements, which is also very good for the future.

Third. A cottage with a consumption limit of 10 kW, which gives 50 A. The total leakage according to the measurement results is 22 mA, and the house gives 2 mA, the garage - 7, and the yard - 13. We put a common difavtomat at 63 A cut-off and 100 mA imbalance, we power the house with the garage separately through the RCD for 80 A nominal and 30 mA imbalance. In this case, it is better to leave the yard without its own RCD at all, but take the lamps for it in waterproof cases with a ground terminal (industrial type), and bring their earths directly to the ground loop, it will be more reliable.

RCD connection in the apartment

A typical circuit for switching on an RCD in an apartment

A typical RCD connection diagram in an apartment is shown in the figure. It can be seen that the general RCD turns on as close as possible to the input, but after the meter and the main (access) machine. The inset there also shows that in the TN-C system, the general RCD cannot be turned on.

If separate RCDs are needed for groups of consumers, they are turned on immediately AFTER the corresponding machines, highlighted in yellow in the figure. The rated current of the secondary RCDs is taken a step or two higher than that of “their own” machine: for VA-101-1 / 16 - 20 or 25 A; VA-101-1/32 - 40 or 50 A.

But this is in new houses, but in old ones, where protection is most needed: there is no land, the wiring is awful? Someone there promised to enlighten on the subject of connecting an RCD without earth. That's right, that's exactly what it came down to.

RCD without earth

RCD connection method without protective earth

Cited at the beginning of paragraph 7.1.80 exists in the PUE not in splendid isolation. It is supplemented with points explaining how, after all (well, there are no ground loops in our houses, no!) “Shove” the RCD into TN-C system. Their essence is as follows:

• It is unacceptable to install a common RCD or difavtomat on an apartment with TN-C wiring.
• Potentially dangerous consumers must be protected by separate RCDs.
• The protective conductors of sockets or socket groups intended for connecting such consumers must be brought to the INPUT zero terminal of the RCD in the shortest way, see the diagram on the right.
• RCD cascade connection is allowed, provided that the upper ones (closest to the RCD input) are less sensitive than the terminal ones.

A smart person, but unfamiliar with the intricacies of electrodynamics (which, by the way, many certified security electricians also sin) may object: “Wait a minute, what's the problem? We put a common RCD, start all PE at its input zero - and you're done, the protective conductor is not switched, grounded without ground! Yes, not so.

The electromagnetic field of the installation and the cord to it are also excluded from consideration. The first is concentrated inside the device, otherwise it will not pass certification and will not go on sale. In the cord, the wires pass close to each other, and their field is concentrated between them, regardless of frequency, this is the so-called. T-wave.

In an apartment with an increased fire hazard, it is permissible, with the obligatory presence of individual consumer RCDs connected according to the recommended circuit, to install a common FIRE RCD for 100 mA of unbalance and with a rated current one step higher than that of protective ones, regardless of the cutoff current of the machine. In the example described above, for Khrushchev, you need to connect an RCD and an automatic machine, but not a difautomatic! When the machine is knocked out, the RCD must remain in operation, otherwise the likelihood of an accident increases sharply. Therefore, the RCD at face value must be taken two steps higher than the machine (63 A for the disassembled example), and by unbalance - one step higher than the final 30 mA (100 mA). Once again: in difautomats, the RCD rating is made a step higher than the cut-off current, so they are not suitable for wiring without ground.

Video: RCD connection

Well, it's knocked out...

Why does the RCD work? Not how, it has already been described, but why? And what if it worked? Once knocked out, then something is wrong?

Right. You can’t just turn it on after a trip until its cause is found and eliminated. And you can find where something is “wrong” yourself without any special knowledge, tools and devices. A regular apartment electric meter will be of great help in this, unless it is completely antique.

How to find the culprit?

First, turn off all the switches, remove everything from the sockets. In the evening, you will have to use a flashlight for this; it is better to immediately attach a hook to the wall when installing next to the RCD and hang a cheap LED flashlight on it.

We turn off the access or main apartment machine. Doesn't turn on? Blame the electromechanics of the RCD; need to be sent in for repair. You can’t dig yourself - the device is vital, and after repair you need to check it on special equipment.

It turned on, but when the voltage was applied, it knocked out again with empty wiring? In the RCD, either the internal imbalance of the differential transformer, or the “Test” button is stuck, or the wiring is faulty.

Wiring fault indication on the meter

We try to turn it on under voltage, looking at the counter. If the “Earth” indicator flashed at least for a moment (see fig.), or earlier it was noticed that it winks, there is a leak in the wiring. You need to take measurements. If the RCD is installed in the order of reconstruction of the wiring and is registered with the energy service, you need to call the municipal electricians, they are required to check. If the RCD is "self-propelled" - pay a specialized company. The service, however, is not expensive: modern equipment allows for 15 min. find a leak in the wall with an accuracy of 10 cm.

But before calling the company, you need to open and inspect the sockets. Insect excrement gives excellent leakage from the phase to the ground.

The wiring does not inspire fear, they even turned it off section by section with automatic machines, but does the RCD knock out “on empty”? Fault inside it. Both the imbalance and sticking of the “Test” most often cause not condensation or intensive use, but all the same “cockroach poop”. In Rostov-on-Don, a case was noted when in a perfectly well-groomed apartment in the RCD, a nesting place was discovered ... Turkestan earwigs, who knows how they got there. Hefty, with huge powerful cerci (tweezers on the tail), terribly angry and biting. In the apartment, they did not show themselves in any way.

Indication of consumer reactivity by the electric meter

The RCD trips when consumers are connected, but there are no signs of a short circuit? We turn on everything, especially potentially dangerous ones (see the section on the classification of RCDs by indices), we try to turn on the RCD, again looking at the meter. This time, in addition to the "Earth", the glow of the "Reverse" indicator is possible; sometimes it is denoted "Return", next. rice. This indicates the presence of high reactivity, capacitance or inductance in the circuit.

You need to look for a defective consumer in reverse order; by itself, it may not reach the RCD before tripping. Therefore, we turn on everything, then turn off suspicious ones in turn, and try to turn them on. Turned on, finally? This is what it is, "reversible". For repairs, but not to electricians, but to "home appliances".

In apartments with TN-C-S wiring, it is possible that it is not possible to clearly determine the source of RCD operation. Then the likely cause is bad ground. While still retaining its protective properties, grounding no longer removes the higher components of the interference spectrum, and protective conductors work as an antenna, similar to a TN-C apartment with a common RCD. Most often, this phenomenon is observed during periods of greatest drying and freezing of the soil. So what to do? It is obligatory to strain the building operator, let him bring the circuit to the norm.

About filters

One of the main sources of RCD malfunctions is interference from household appliances, and effective way to combat them - absorbing ferrite filters. Have you seen knobs - "bumps" on computer cords? This is what they are. Ferrite rings for filters can be bought at the radio store.

Homemade absorbing ferrite filters

But for power ferrite absorbers, the magnetic permeability of the ferrite and the saturation magnetic induction in it are of decisive importance. The first should be at least 4000, and better - 10,000, and the second - at least 0.25 Tl.

The filter on one ring (at the top of the figure) can be built in with a "noisy" installation, if it is not under warranty, as close as possible to the network inlet. This work is for an experienced specialist, so the exact scheme is not given.

Several rings can simply be put on the power cord (in the figure below): from the point of view of electrodynamics, it doesn’t matter if the conductor is wrapped around the magnetic circuit or vice versa. In order not to cut the branded molded cord, you need to buy a plug, a socket block and a piece of a three-core cable. Ready-made power cords with ferrite noise absorbers are also sold, but it costs more than home-made prefabricated parts.

Video: errors when connecting RCD

As already mentioned at the beginning, RCDs are not a panacea for electrical hazards. It greatly reduces the likelihood of electric shock, but electricity still does not tolerate thoughtless and irresponsible handling of it.

The best option for the development of electrical safety measures is the widespread use of chipped sockets and electronic differential RCDs built into electrical installations. In this case, even the TN-C power supply system, while maintaining its efficiency, could become completely safe.