Practically in the life of every person there comes a time when he begins to think about ensuring his proper housing, health and life. But in order to protect yourself and your own home, you need to be as conscious as possible in solving this issue. It is necessary to pay special attention to the electrical wiring in the house, because safety largely depends on it. It is necessary to be very careful in the choice of wiring. You can't make hasty decisions in this matter.

Currently, almost every apartment and house uses a huge variety of household electrical appliances. The larger its quantity, the more significant the load on the electric cable will be.

If you do not use special protection devices, there is a possibility of unpleasant problems. Almost every material is capable of becoming unusable over time. The same can be said about the external wiring, the internal wire, which is located directly in the body of the electrical appliance. Over time, the insulating properties are gradually lost. Therefore, electricity leaks may appear, which in turn acts as a direct threat to human life. It is important to avoid these types of problems. To do this, you just need to start using special protective devices. One of the main devices of this type, which has recently become more and more popular, is the RCD, that is, the device protective shutdown.

Why is it necessary to install an RCD in an apartment?

It is not very difficult to understand from the name of the device that it is designed to provide an appropriate level of protection for every living being so that it is not affected by the action of an electric current. It also allows you to effectively prevent the possibility of electrical wiring fires as a result of overheating, as well as various malfunctions.

It was previously noted that a violation of the integrity of the internal electrical circuit appliances. There are several main reasons for this fact, among which one can note temperature damage, mechanical stress, as well as elementary aging of the electrical wiring insulation. Time spares nothing and wiring is no exception to the general rule.

If there is no residual current device, then almost each of the above reasons can harm a person. There is a possibility of losing not only your own home due to fire, but there is also a certain risk of death under voltage. An electric shock may well provoke cardiac fibrillation. And if there is no one nearby who can come to the rescue, that this threatens with extremely significant consequences.

Of course, in this case, a significant role is also assigned to the person's own resistance. The higher it is, the less chance there will be to stay alive. There is hardly any need for such a risk to one's health. It is better to protect yourself and all the people living in the house or apartment from such potential damage. To do this, you just need to install a device for protection in your home. Do not be stingy, because it is a kind of guarantee of health and safety from electric shock.

You can give a specific example. When the washing machine is running, and the insulation has been damaged on the phase wire. It's all about the body. As a result, the latter is under a certain voltage. If a person stands on a wet floor and accidentally touches the metal part of the washing machine, a circuit will form and the current will pass through the person, going into the ground. The RCD will understand that something is wrong here, that not all the current has returned, and will turn off the voltage almost instantly. This will save a person's life. Of course, a person will certainly feel some discomfort, such as a slight tingling, but will remain alive.

How does RCD work?

The key task of this device is to protect a person from a damaged device, part of which may have dangerous potential. Phase and zero from a direct power source are connected to the upper terminals of the device, and zero and phase going to the load are connected to the lower terminals. In this case, the electric current flows from the power source, passing to the device through the RCD, after which it again returns to the network through the RCD. We can conclude from this that the RCD is a kind of controller that monitors the current strength at the "input" and "output". Then, when the indicators at the input and output of the device are different, then somewhere there is a leak. The residual current device responds to such a leak extremely quickly. Typically, it takes about 0.04 seconds to activate and deactivate.

in a properly functioning electrical network there should not be a significant difference between the incoming and outgoing currents. If the amount of current that enters and exits is the same, then no trip will occur. However, in the event that the current finds another way to exit, the RCD will necessarily turn off, stopping the power supply.

We must also not forget that the device can significantly increase the level of security. electrical installations, however, cannot eliminate the risk of electric shock or fire. The device cannot respond to emergency situations when no current leakage occurs. For example, it can be a short circuit or an overload. Here the device will not be able to react to them.

To protect a person from current injuries, a device is used, the normal current of which varies from 10 to 30 mA. This is due to the factor that a larger current can be lethal to the human body.

Manufacturers currently produce RCDs with leakage current ratings of 100, 300, and 500 mA. Everyone probably knows that with a current of 50 mA, a person will not be able to get rid of the wire without the help of outsiders. And if the value reaches 80 mA, then instant death will follow. In reality, RCDs are not used to provide normal protection against electric shock. It should perform a slightly different task.

The need to use a device with a rating of 100 mA or more is due to the fact that in almost any electrical power system there are so-called "stray" currents. That is, leakage of natural currents occurs. There is practically no perfect insulation anywhere, which is why there is usually a natural current leakage.

Residual current devices, which are designed for leakage rates of 300 mA, make it possible to exclude the possibility of a fire. For example, in the case of a long-term current leakage with parameters from 200 to 500 mA, a significant amount of thermal energy will be released, which may well be enough to ignite nearby materials.

For this reason, RCDs are primarily used to guarantee fire protection. A device with this rating allows you to provide a reserve of the main RCDs. They are usually installed at the entrance to the premises.

Residual current devices perform the most important function - they protect a person from injury electric shock. Therefore, where there is a possibility of a person falling under dangerous voltage, it is imperative to install an RCD there. The fact that it is necessary to protect groups of outlets with it is known to everyone and many do it. Here is a completely different situation with lighting groups. Someone puts an RCD here, but someone does not. Below I want to express my point of view on this issue - is RCD needed in lighting circuits?

Let's look at the regulations first. We look at the EIC, clause 7.1.79 (read the text in bold italics):

In group networks supplying socket outlets, an RCD with a rated operating current of not more than 30 mA should be used. It is allowed to connect several group lines to one RCD through separate circuit breakers(circuit breakers). The installation of RCDs in lines supplying stationary equipment and fixtures, as well as in general lighting networks, is usually not required.

According to this paragraph, the installation of RCDs in lighting circuits can be neglected. Whoever does not put an RCD here, in principle, does not violate anything. But personally, I always put RCD on lighting. My opinion is that the preposition "not" before the word "required" should be removed from this paragraph of the PUE. This would be a safer wiring option. Now I will try to justify why I think so.

1. To chandeliers, lamps, sconces, etc. tens of meters of cables also stretch, as well as to sockets. Although rare, it happens due to damage to the insulation that a current leak appears. This is true for all cables. Lighting circuits are no exception. For example, it is very common for cable insulation to be damaged when crossing walls made of drywall. As a rule, a metal profile is attached to the ceiling and the cable route runs there. In order to pass through such a partition, electricians drill a metal profile. The resulting hole produces very sharp edges that no one processes and removes sharp burrs. I constantly see how they take cables and simply pull them through a hole in the profile. Because of this, its insulation may be damaged. How are we doing it? If the cable does not stretch, then you need to pull harder))) After pulling, the cable remains lying on the sharp edges of the profile. It is rare that anyone here lays a sleeve, or at least a corrugation. Due to vibration, after some time in this place, the insulation can be damaged and dangerous potential can reach the entire structure of the metal profile. This is a very dangerous situation. In fact, there are many more of them, since cable routes, the premises themselves, situations, the hands of installers, etc. are very varied. Therefore, I believe that all lighting groups need to be protected using RCDs. Above, I gave only one example, where there is probably damage to the cable insulation.
2. Many chandeliers and lamps have metal cases. The current quality of their production leaves much to be desired. Therefore, there is a high probability that a dangerous potential will hit the metal case of the lamp. When replacing a lamp, repairing a chandelier, or when cleaning dust with a damp cloth, it is possible to touch the body of the chandelier. At this point, you can get an electric shock. This person needs to be protected. Therefore, I believe that all lighting groups need to be protected using RCDs.
3. In rooms with high humidity, it is also likely to get a leak in the lighting circuits. Condensation, rapid corrosion, unsatisfactory installation, poor lighting, poor wiring in a cabinet with a socket and lighting, etc. Therefore, I believe that all lighting groups need to be protected using RCDs.

From the foregoing, we can conclude that the lighting network is not so safe for humans. Therefore, if there is even the slightest threat of a person getting under voltage, then it is imperative to install a residual current device. Take care of yourself and your loved ones! To do this, it is not necessary to buy separate RCDs, increase the budget of the shield and its dimensions. To do this, you can simply connect the machine from the lighting group under the RCD, which is on the sockets. These RCDs must already be present in the shields. Therefore, here you can avoid additional expenses by competently assembling the electrical panel. Remember that electrical safety should come first.

Below are a couple of examples from my practice.

This is a lamp from an ordinary bath. The type of lamp and the wire itself are not correctly selected here. At one not perfect moment, the insulation was damaged and the current began to “leak” into the ground along the damp walls. A bunch of lawsuits fell down, everything crackled and smelled of scorched wood. Fortunately, the owner was nearby, he saw all this and was able to turn off the machine in a timely manner. The RCD did not stand here, and the machine did not work, since there was no short circuit. What would happen if the owner was not around or he washed directly in the bath and everything around was in the water? It's scary to even think about.

And this is a typical Chinese chandelier from Leroy. She puffed and it was very good that the power supply burned out and excluded the further spread of current to the metal case and beyond. The machine in the shield did not work, and the RCD did not stand. What would happen if a dangerous potential remained on the body of the chandelier and the owner climbed up to it to check why it was not working? It's scary to think too.

In modern chandeliers, the thinnest wires very often melt. So the phase can get on the metal case.

Remember that the life of a person and his property is not comparable to the cost of an RCD. Therefore, take care of yourself and protect yourself in terms of electrical safety competently)))

PS: Both owners of the described cases did not install the RCD, although I told them about it.

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 is 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 (PUE-7A; Electrical Installation Rules (PUE), 7th edition, with additions and changes, M. 2012), paragraph 7.1.80 still dotted i: “It is not allowed to use RCDs that respond 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.

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 case, 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, RCDs remained “fireproof”, they responded to a current that excluded the ignition of an arc between 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)

By “turning” 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 imbalance (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. AT single-phase network it is enough to compare the magnitudes (modules) of currents in the phase wire and neutral, and when connecting the RCD to three-phase network are the total current vectors of all three phases and the neutral. An essential feature of RCD-D is that in any power supply circuit, 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

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.

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.

UZO-DE

In this case, "E" does not mean capacity, but electronics. UZO-DE are built directly into or in the 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:

1. High sensitivity, comparable to UZO-E, combined with the noise immunity of UZO-DM.
2. 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.
3. 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 UZO-DE are primarily high cost, own power consumption (negligible, but if the mains voltage drops, UZO-DE may not work) and a tendency to failure - after all, electronics. 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:

1. 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.
2. 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.

PATTERN

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 cut-off 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 range 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 protection circuit

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 clause 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 housekeepers, at the input after the meter it is enough to put a fire RCD with a 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.

Calculation examples

The first - new flat 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. RCD we take a step or two higher in 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 smells like under the guarantee.

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 on 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 lead their lands directly to the ground loop, it will be more reliable.

RCD connection in the 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

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:

1. It is unacceptable to install a common RCD or difavtomat on an apartment with TN-C wiring.
2. Potentially dangerous consumers must be protected by separate RCDs.
3. 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.
4. 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.

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.

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 shop.

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.

Before answering the question "Which RCD should be installed at the entrance to the apartment?" Let's figure out why install an RCD at all.

RCD is installed:

1. For the purposes of electrical safety - to protect against electric shock with direct or indirect contact;
2. In order to protect against fire in the event of leakage to the electrical enclosure or to the ground.

The principle of operation of the RCD

The principle of operation of the RCD is based on measuring the difference in currents in the phase (phase) conductors and the zero working conductor. In normal operation, the vector sum of the currents is zero. When a leakage occurs, the phase current differs from the current in the zero working conductor by the value of the leakage current. The current induced in the coil drives the core of the coil, which breaks the power circuit.

Requirements for the use of RCD

Requirements for the use of RCD for electrical safety purposes regulated by the PUE, chapters 1.7, 6.1, 7.1. The tripping current of an RCD installed for electrical safety purposes should not exceed 30 mA (use RCDs with a tripping current of 10 mA and 30 mA).

The rating of the RCD for the tripping current is selected in accordance with the requirements of clause 7.1.83 of the PUE. The total leakage current of the network in normal mode should not exceed 1/3 of the rated current of the RCD. Since there are no data on leakage currents, they are carried out in accordance with the requirements of this paragraph. When calculating, the leakage current of the electrical receiver is taken to be 0.4 mA for every 1 A of load current, and the network leakage current is 10 μA for each meter of cable length.

RCD installation requirements for fire protection regulated by the following documents:

1. PUE, p.7.1.84 “In order to increase the level of fire protection in case of short circuits to grounded parts, when the current is insufficient to operate the overcurrent protection, at the entrance to the apartment, individual house etc. it is recommended to install an RCD with a tripping current of up to 300 mA ";
2. Federal Law of July 22, 2008 N 123-FZ "Technical Regulations on Fire Safety Requirements". Article 82, part 4 “The power supply lines of the premises of buildings and structures must have protective shutdown devices that prevent the occurrence of a fire. Installation rules and parameters of residual current devices must take into account the fire safety requirements established in accordance with this Federal Law ".

In accordance with these requirements, an RCD with a trip current of 100 mA or 300 mA is installed at the entrance to the apartment. Such an RCD is called fire-fighting.

If the calculation shows that the apartment shield does not exceed 10 mA, then you can save money and you can install an RCD with a trip current of 30 mA at the entrance to the apartment. This RCD will serve as a "fire" RCD and RCD used for electrical safety purposes.

Otherwise, a “fire-fighting” RCD with a trip current of 100 mA or 300 mA is installed at the entrance to the apartment, and an RCD with a trip current of 10 mA or 30 mA is installed on the outgoing lines (where the installation of an RCD is required for electrical safety).

Before dealing with the question of whether there is a need to use an RCD, you need to figure out what general function this device performs. It compares the amount of current that went into the house with the amount of current that returned from it. If these two values ​​differ from each other, the voltage will be switched off automatically.

When is an RCD useful?

When there is a violation of the integrity of the insulation of wires in household appliances. Let's say that the insulation on the "phase" is broken in the electric stove, and it touched the grounded case. The electricity will automatically turn off, because the current that went to the consumer through the "phase" wire did not return to the RCD, but "went" through the ground loop and, therefore, the difference between the outgoing and incoming currents turned out to be different from zero.

However, for this device it does not matter at all what load is included in the network - Electric kettle, washing machine or a person. If there is no current leakage, then everything is fine. But in any case, the residual current device greatly increases safety, because it is almost impossible to imagine such a case for a person to be electrocuted without leakage, which means that the protection will work anyway. Of course, there is a possibility that the current will flow without leakage (for example, through the chest, and not through the arm-arm or arm-leg loop), but it is extremely small.

How many RCDs do you need?

In principle, one such device for the whole house is enough to protect against electric shock, although this is not always convenient. It is clear that it is better if, with the above problems with wiring or electrical appliances, a separate "branch" will be de-energized, and not the entire house. More than one piece of RCD can be put in a separate electrical panel (individual), but in general, which is located on the landing, there is simply not enough space.

If such a device is installed on a separate line, from which the current goes immediately to the consumer, it must be purchased with a built-in maximum current limit function. If you use a simple RCD, then in cases with short circuit it can go bad right away. Either in cases with long-term overload currents, it will heat up all the time and again fail, or it will work without any leaks. This "option" of current limitation also means a higher cost of such an RCD compared to a conventional one.

Are there cases when it makes no sense to install an RCD?

Yes, when there is use of old "worn out" electrical wiring. Then the detection of current leakage by the residual current device can lead to its permanent operation. And with dilapidated wiring, this will happen all the time. In this case, the best option would be to install sockets with an already built-in RCD in potentially dangerous areas in the apartment, rather than installing a separate device in a shield.