I promised to roll up a post for a long time, but because of the creative crisis, it was a little delayed =) And I was too lazy to draw diagrams, but now they somehow drew themselves. And today we are talking about RCD! =) And at least in order to dispel the terrible obscurantism, which began to be born on the Web on forums in the context of “and I heard somewhere that uuuuu ..” - “yes-yes-yes, probably yyyy” and so on. RCD has become mandatory for use in our country as early as 12 years ago (since 2001), but right now, for most electricians (especially ZhEKovsky), RCD is some kind of mythical device that seems to need to be installed, and which sometimes for some reason something knocks out and probably broken?

Will have to figure it out. Let's start with the simplest: what for is it needed? And first of all, to protect a person from electric shock and, accordingly, from death. It is known that a person dies at a current of about 80 mA (0.08 A), and a current of about 50 mA (0.05 A) is considered to be a non-release current (when a person cannot tear himself away from the wire on his own). A conventional machine protects the line only from overcurrent (short circuit or heavy load), and even with a current of 1..2 amperes, it should not work. Therefore, in this variant (when there is only a machine gun on the line from the defense), we can quite calmly get a charred carcass of a person and an unplugged machine gun.

OK! What can we do? First you need to analyze a little what is happening in general. The following usually happens. If a person simply put two fingers into a socket, nothing can help him, this is evolution ("Technological progress has made sockets inaccessible to most children - the most gifted die" ©). But if he touched a kettle or a washing machine in which the heating element was leaking, and because of this, dangerous voltage appeared on its case, then a dangerous current would flow from the device case through the human body. For example, on a wet floor.

Get hurt. Great! And if we come up with some kind of additional conductor that will imitate a person who has fallen under the influence of a current? And pre-connect it to the case? And in case of danger, all the current will go through it? So that's exactly what they came up with! This is the well-known "grounding" or, to put it correctly, a protective conductor - PE, P rotation E arth. And here we immediately need to talk about terminology.

Unfortunately, the terminology is also a complete ass! Because before 2001 there were no such devices in our country at all]
>>I've been corrected here. I took the date of 2001 as the release of a new edition of the PUE, where the installation of an RCD became mandatory. But it turned out that they were produced earlier, and there is even one on this topic. Yes, yes, indeed, I waved. I saw Stavropol DifAutomata in sockets built in the 90s. By mentioning the date, I really wanted to say what should have been written in simple words: “Until now, many people do not understand at all what this is and why it is necessary.”
[, and when they showed up they were called names. In Western countries, the RCD is called as follows: " Residual current circuit breaker". This refers to the principle of operation of this RCD, which we will consider a little later and which is based on measuring the difference (difference - difference) of the flowing currents. We call this thing Residual Current Device.

And the word " differential"we, his mother, is usually used to refer to a differential automaton - a contraption that contains a conventional automaton and an RCD! Moreover, the same difavtomat is also called " Differential circuit breaker«.

How's the confusion? So, it turns out:

Automatic, Automatic switch is a common device that provides line protection against overcurrent in it. More generally, it can be said that overcurrent protection;

Differential switch, Residual current switch, RCD is a device that protects a person from electric shock. In general terms, this type of protection can be called either "differential protection", or "protection against leakage currents" or "protection against current leakages".

A differential circuit breaker, Dif, Difavtomat is a device that contains the properties of a conventional automaton and an RCD that provides protection for ONE line from overcurrents and leakage currents.

Therefore, if you see some strange inconsistencies or abbreviations like “Off. Dif" or "Aut Diff off" - be sure to Clarify what is meant there!

Now let's touch on the topic of PE-explorer.

Protective conductor should correctly be called "Protective conductor", PE-conductor, PE! Do not use the words "grounding" and the like, because they do not quite correctly indicate what you want to say! I translate into the correct language. Only depending on the specific power supply system (TT, TN-C-S), the protective conductor will be either neutral, or clean ground, or even re-ground =)

Therefore, if you are trying to say something in a general way (“Do you have a floor shield with grounding?”) - say “Is there PE in the floor shield?”. If we are talking about some kind of input device, say exactly what is there: “You need to re-ground zero using a ground loop.”

The problem of incorrect terminology is also that when it comes to grounding in an apartment building, then some unique ones begin to produce different ideas “Oops! I’m going to stuff some pins into the ground, drag the cable to the 9th floor, and I’ll have a fucking ground!”. In fact, it turns out that then either the whole house begins to feed through this grounding, or a dangerous potential is transferred to it in the event of an accident. And because of this, people are dying again.

Now let's get back to how this very RCD works. So we came to the conclusion that the RCD protects a person from a damaged device, on the body of which there is a dangerous potential. It works like this:

The phase and zero of the power supply pass through the RCD. The RCD controls the current strength at the "input" and at the "output". If the current leaves as much as entered the RCD, there will be no trip. But if SUDDENLY the current found some other path, and part of it began to leak to another place (that's where the term "leakage" comes from), then the RCD will immediately cut off the line. In my drawing, this is shown by thick and thin arrows.

Once again, I draw your attention to the fact that the RCD will NOT protect against if you take the phase and zero! Then a person (moron) for this RCD will be a normal load, and he will die anyway. However, RCD will protect:

• From a breakdown on the body in technology. Most often these are heating elements (heaters). Moreover, a breakdown can occur only when the heating element heats up. I had to explain to my customers several times why it “suddenly” began to knock out their washing machine, although everything worked well in the old apartment. Of course, it turns out that I assembled the new shield - and put the RCD on all the lines, and in the old apartment there were only two machines for everything. Once I had a very, very serious scandal because of this. But still the problem turned out to be in technology =)
• From crooked wiring, when all sorts of valiant "electricians" wall up a twist somewhere in the plaster. If the wall gets wet (for example, the plaster has not dried) - the phase from this twist will honestly flow into the wall, and the RCD will cut off the line. And it will, stsuko, chop off until it dries or until it is remade.
• RCD can be triggered by non-obvious, but dangerous things. For example, if you have a gas stove with electric ignition, or a washing machine connected by a metal-braided hose to water pipes. In some cases, due to neighbors who “grounded” somewhere in the wrong place, a current leakage (or current difference) will again occur, due to which the RCD will trip. In this case, you need to carefully think, think and, possibly, prevent a serious accident.
• From improper installation in the shield. If you mixed up different zeros (before the RCD and after) - the RCD will also work. We will talk about this again a little later.

RCD MUST be installed! Do not listen to those who say that "yes it will knock you out"! This means that they most likely do not understand why it knocks out what to do and (or) do not want to fix their jambs! If your wiring is budget (and a shield in the heels of machines) - you only need one RCD for the entire apartment. If you have a complex shield, you can put several RCDs in different zones or types of rooms.

However, I remind you: the RCD does not have overcurrent protection !! This is a device that protects a person from electric shock! Therefore, in the circuit where this RCD is located, there must also be an automatic machine!

RCDs have three parameters by which they can be selected:

• Rated current of contacts. On the RCD, it is indicated by the ampere numbers without the letter of the shutdown category, as on the machine. For example, the standard range of such currents for ABB RCDs is 16, 25, 40, 63, 80A. ATTENTION!!! This is NOMINAL!! These are not exact current amps!!! In the same way as on a conventional machine: B16 is written, and according to the table it will turn off in the range from 48 to 80A when closed.
  The denomination is designed to help you choose the right RCD when compiling the filling of the shield. We will also talk about this in detail below =)
• Rated leakage current. This is the most important RCD parameter: it shows at what value of the differential current the RCD will trip. According to RCD standards, it should operate in the range from 0.5 to 1 leakage current (for example, from 15 to 30 mA for RCDs at 30 mA). Value options:
  • 10 mA (0.01 A) is the most sensitive current value. An RCD with such a leakage current can be used in very critical places or in especially wet rooms. However, such RCDs are specially produced with a low contact current rating so that many lines are not crammed under them. Each cable, technique - all have some insulation resistance and natural leakage current. And if there are many such lines, then a sensitive RCD may falsely work.
  • 30 mA (0.03 A) - THE MAXIMUM value of the leakage current for the protection of people and premises! If you want to protect people, install an RCD of this particular value. No more!
  • 100 and 300 mA - RCDs that can be put at the input to the building to ensure selectivity: so that the group RCDs of the lowest ratings are turned off first, and then the input ones. In some cases, these RCDs can protect the input cable, shield wiring and operate in case of accidents, floods and other cataclysms. Because of this, they were nicknamed "fire-fighting."
• Leakage current category. This is what leakage currents the RCD will operate on:
  • AC- RCD will fire only alternating leakage current. This is the most common common denomination that can be used everywhere. An alternating leakage current can occur if our supply phase is directly punched into the case. Let's say the heater's bad insulation, the winding of the motor, the transformer has been pierced, the supply wire has frayed.
  • A- more expensive and sensitive option. In this case, the RCD fires both alternating and pulsating leakage current (sine wave half-waves). This can be useful if secondary power circuits inside the device can break through to the case. Let's say the switching power supply is damaged, something after the rectifier, and so on. These RCDs are more expensive, and if you don't want to spend a lot of money on a shield, you should consider where these RCDs can be applied.
    UPDATE 2014.02: Now even energy-saving and LED light bulbs have switching power supplies. And Europe is slowly moving to RCD type "A". Therefore, AC type RCDs can only remain on heaters and underfloor heating.
    RCDs of type "AC" and type "A" are supplied to Russia. If you need a simpler shield, then it’s enough to leave the RCD of the “AC” type. If you want wild paranoia and complete protection, then you can install all type “A” RCDs.
• View of the internal circuit:
  • Electromechanical. This RCD is more expensive, because it works precisely on the magnitude of the leakage current. But this requires high-precision mechanics: it must work from the same 10 or 30 mA of current, but at the same time, being accurate, it must not work from various shocks, shaking and other external influences. Usually, for this RCD, I don’t care where to connect the phase, and where - zero, and nothing is written about it on the case.
  • Electronic. Inside such an RCD is a simple amplifier on a microcircuit or transistors. This allows you to configure it for any leakage currents. But - here's the trouble - in the event of an emergency network voltage, such an RCD can die, because it is powered by it. But these RCDs are cheaper, which is why they are most often made by different Chinese. Usually for these RCDs, it is important to connect the phase and zero (and even sometimes the power supply side is on top or bottom).

Let's take the RCD ABB F202 AC-40 / 0.03 and disassemble it! I came across a fully working copy, but with a marriage: its flag did not change color to green when this RCD was turned off.

I remind you that ABB RCDs have double clamps. This is what allows you to simultaneously connect two wires of zeros under one RCD without an additional zero busbar. And we'll talk about that later too.

We open the RCD and see what is there:

In front we see the mechanical part, and behind - a scarf with details. Some might think that this is an electronic RCD, but it is not. There are a pair of diodes on the scarf (for rectifying alternating current from a differential transformer) and filtering capacitors, apparently to protect against false positives.

In the photo below, you can also see the power lever of the "Test" button. This button simulates a leakage current, and when pressed, the RCD should trip. If the RCD does not work, then it is either defective or dead. In my shields, I check all UZOs in this way.

In these RCDs, the TEST button is only energized when the RCD is on.

Inside the UZOshka there is an arc quenching chamber:

But the fixed contacts of the RCD are made of electrical brass.

There are silver solderings on the moving contacts:

Now let's look at the differential transformer - the basis of the basics of the RCD. It is he who "measures" the currents flowing through the RCD. In RCD data, it is made in the form of a solid block:

Inside the transformer, the main supply wires are rigidly fixed in special channels. I liked the build quality of the transformer. The photo below also shows a resistor to create an artificial leakage current.

And here is the secondary winding of the transformer. The number of its turns determines the amount of leakage current at which the RCD will trip.

RCD works like this. If a current of the same magnitude flows in and out through the RCD, then the magnetic fluxes from both conductors, in which the current flows in different directions at one time, are balanced, and no current occurs in the secondary winding of the transformer. If the currents flowing in and flowing out through the RCD are different, then a current will appear on the secondary winding of the transformer.

It straightens and is fed to an electromagnet, which turns off the RCD.

Here is such a mockery happened over UZOshka:

And here is a photo of the TDM electronic RCD from the MasterCity.ru forum:

It seems to me that there is no need to explain the difference here? We see an amplifier on a microcircuit (in the distance), filtering capacitances, and a transistor, which, apparently, switches the power of the electromagnet.

Well, now we begin the practical part, in which, in fact, there are even more nuances than in the theoretical one!

RCD connection

In fact, there are two important nuances:

1. RCD MUST be protected at its face value! That is, in the circuit where the RCD is located, there must be a fuse or a circuit breaker that will protect the RCD. Some understand this literally, and begin to put a personal machine right in front of the RCD, and also a two-pole one. Because of this, strange discussions in the forums, muddy shield schemes and other oddities begin.
Technically, this means exactly what is written: before or after the RCD there must be one or more machines. The RCD will be protected if the machine has a rating equal to or less than the rating of the RCD. Below I will show examples of such schemes.

2. Phase and Zero that have passed through the RCD should not be "mixed" with other phases and zeros. That is, if, according to the shield scheme, you took the phase after one specific RCD, then you should also take zero after this particular RCD. If you make a mistake, then the RCD will turn off, and you will puzzle over what it was =)

Let's see a diagram of some shield:

What do we have here? Here I simply drew a simple shield: two machines for the light and three machines for sockets. We have an introductory machine at 40A. Our light is made without RCD, and all sockets are under RCD. Pay attention to how the lines are grouped, and to the layout of the zeros. Since our light is connected to the RCD, then we take zero to the light to the RCD, using a zero bus for this N. Zero on the sockets that are connected after the RCD is also taken after the RCD and from the tavern N'.

Is everything simple? In fact, yes, but the debate continues on the forums about circuit breakers TO RCDs. So let's take a look at this chart:

And let's see my correspondence with ABB: . It clearly says that if the sum of the ratings of the machines after the RCD does not exceed its rating, then the RCD is protected and no additional machines are needed.

UPDATE 2014.02: ATTENTION!!! This information is only valid for ABB RCDs, because I dug it in catalogs and dug it out to technical specialists. What was found out.

In fact, there are two RCD protections: overload and short circuit. For overload, the nominal value of the machine must be 100% no more than the nominal value of the RCD. According to k.z. we can protect ourselves with automatic machines and fuses with a large rating. The RCD shows the level of protection when using a 100 A fuse because there is such a standard test. But we will not take a separate machine and a separate fuse. Therefore, we simply defend ourselves with a machine gun with a small denomination.

The relative position of the machine and the RCD and the total number of machines is not important. The main thing is that the total rating of the machine (if it is on top) and the machines (if they are on the bottom) should not exceed the rated current of the RCD.

As with other manufacturers - I don’t know, so before stupidly copying the scheme shown above and still proving to everyone “But CS drew here, and you are all fools” - read the damn technical catalog of the manufacturer !!

How to choose the right RCD according to the contact current rating? The rules can be described, in relation to our shields, as follows:

• If the rating of the introductory machine is less than or equal to the current rating of the RCD, after the RCD there can be as many machines as you like;
• If the value of the introductory machine is greater than the value of the RCD, then after the RCD, the machines are placed so that the sum of their ratings does not exceed the current rating of the RCD.

I drew pictures. On the first we have two RCDs for 40 and 25A. At the same time, the nominal value of the introductory machine is 40A. The first RCD has a rating of 40A, and is protected by an introductory machine. Therefore, after it, you can cram anything and as much as you like. Under it, automatic machines stick out with the sum of denominations as much as 58A. The second RCD has a rating of 25A (for example), and therefore we can protect it only by putting automatons after it for no more than 25A (6 + 6 + 10A = 22).

Let's look at the second diagram. Here we have an introductory machine for 50A (as in new buildings with a single-phase input). Since we had machines worth 58A under the first RCD at 40A, the RCD at 40A will not work in any way. What to do? let's raise the rating of this RCD to 63A - and everything will get better. But at the second RCD, I showed an example of how not to do it. We have a second RCD at 40A, and the machines under it are at 48A. Here it is not protected and it is not necessary to do so!

How to invent shields for RCD? RCDs in shields are more convenient to use in the case of a single-phase power supply. Then the whole shield turns into a tree structure, as in the pictures above: an RCD, under which there are several automata. This is the easiest and most budget option. And it’s easier to assemble the shield if all the RCDs can be put in a row and connected with a special shank-comb (I). The budget of this option is that some RCD of type A at 10 mA is cheaper than a difavtomat of the corresponding rating, and even with category B.

However, there is also an inconvenience. If a leak occurs on one of the lines under the RCD, the RCD will cut off all these lines at once. This will be somewhat inconvenient, as you understand, especially if it will be difficult to immediately find the place of the leak. In some cases, you even have to disconnect the zeros from the bus to find the problem line, or use two-pole automata (in relation to ABB) or 1P + N automata (other manufacturers have them in the form of a single module).

However, we remember that if there are too many lines under one RCD, then the RCD can falsely trip from the natural leakage current through the cable insulation and power filters. Therefore, usually an ideal RCD shield contains several RCDs, grouped by type of room or type of load. This allows you to turn off the lines for leaks in small sections, without turning off everything at once.

And now a few more words about what to do if there is no PE, and how to check the RCD in general.

If PE is not, then you still need to install an RCD! Do not listen to those who say "it will not work without grounding." Firstly, remind them of the correct name for PE, and secondly, the RCD will work, but in fact. If in a circuit with PE the leakage current has where to go (in PE), then without PE the leakage current has only one way: through the touched person. What will happen? If the leakage current is so small that the RCD will not work, you will simply be shocked. If the leakage current is large, then you will be pulled, but the RCD will immediately work, disconnecting the line and reducing the time of the dangerous current on you. I remind you that in this case, all lines still need to be laid with PE, just do not connect PE anywhere until the reconstruction of the power supply system.

RCD can be checked like this:

a) Press the "Test" button. If the RCD is turned off, then everything is fine with him.
b) If there is a regular PE - short-circuit zero N and PE in the socket or power cable. Do not confuse with the phase! RCD should turn off.
c) Indirectly: if something is flooded somewhere, or the entire cable is bitten, then the RCD will work =)

Somehow, unexpectedly, he told everything about everything. I thought it would be long and tedious, but it turned out simply and clearly. Anything I forgot to say, ask in the comments!

If you are interested in the information from this post and you want to contact me (or order / ), then write to me by mail or call +7-926-286-97-35 . I respond to the name "Electroshaman".
Inattentive, stupid and arrogant salespeople and managers, I will banter hard if they do not look into, but rather rush to call.