Electric machines, varieties of ouzo. Ouzo in a private household. Classification by response time interval

If you paid attention to this article, then you probably recently asked yourself the question: “What is an RCD and what is its purpose?” We will try to answer this question in as much detail as possible. Well, for starters, let's say that the abbreviation RCD stands for residual current device.

Despite the fact that these days electrical wiring is maximally protected from contact with people and sad consequences, there is no escape from leaks. This is where the RCD will become an indispensable assistant. The device will react with lightning speed to an increased current value at the leakage point and cut off the power supply.

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

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

Why install an RCD?

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

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

NOTE! RCDs differ from automatic circuit breakers that protect wiring from overloads and short circuits; its purpose is to significantly increase the protection of people.

Operating principle of RCD

The operation of the device is based on recording the leakage current to the ground and disconnecting the power grid in the event of such an emergency. The device detects the presence of a leak only by the difference between the currents: those that came out of the device and those that returned back.

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

The same thing happens if the insulation in one of the electrical appliances is damaged. Then the housing or other part is under tension. By touching them, a person creates another circuit “to the ground.” In this case, part of the current will move along it, that is, the balance will be destroyed.

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

When is it necessary to install an RCD?

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

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

When does an RCD not help?

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

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

How many RCDs need to be installed?

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

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

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

When is it not practical to install an RCD?

Sometimes there is simply no point in installing a device. One such situation is the presence of old and decrepit wiring. The ability of an RCD to detect a leak can become a headache if the device begins to operate unpredictably ( and this is exactly what happens when the wiring is bad). In this case, the best solution would be to install the RCD not in the power supply circuit of the apartment as a whole, but in places with increased danger for using sockets.

There is also no point in buying a low-quality RCD. On the modern market you can find not only original devices, but also a wide range of fakes of unknown origin. Many of these devices are made “on the knee around the corner.” The use of such devices is completely unacceptable and inappropriate. Before purchasing, carefully study the technical documentation and quality certificates of the purchased unit.

It makes no sense to install the device in lines that supply voltage to stationary equipment and lamps, as well as in general electrical networks.

Device

The RCD device requires the presence of:

• leak sensor;
• polarized magnetic relay.

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

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

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

Main technical characteristics

Each RCD has a certain set of technical parameters that should be studied before purchasing:

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

Explanation of markings

The marking is applied to the body of the RCD, which makes choosing the right model more convenient and easier. First of all, the manufacturer is indicated, but there is also other important information:

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

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

• N ( above) – the incoming neutral conductor is connected to this contact;
• 1(above) – the incoming phase conductor is connected here;
• 2 (from below) – the phase conductor going to the load is connected to this place;
• N ( from below) or absence of a letter– the neutral conductor going to the load is connected.

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

Species and types

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

Electromechanical

Electromechanical RCDs are widely used and are used in AC electrical circuits. What causes this? The fact is that when a leak is detected, such a device will work, preventing dire consequences even at the smallest voltage.

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

Electronic

Such RCDs are easy to find on any construction market. The difference between them and electromechanical ones is that they are located inside the board with an amplifier, which requires power to operate.

However, such RCDs, as already mentioned, have a huge drawback - it is not a fact that they will operate in the event of a current leak ( it all depends on the network voltage). If the zero burns out, but the phase remains, then the risk of electric shock does not go away.

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

Selective

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

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

Fire protection

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

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

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

Number of poles

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

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

Conclusion

Every day more and more household electrical appliances appear in our lives. Accordingly, the risk of current leakage increases, which sometimes even leads to death. Even if it doesn’t kill you with an electric shock, it will cause serious health problems or cause a fire. There is one salvation from all these troubles - a protective shutdown device. We strongly advise you to install it at home, as they say, out of harm’s way.

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

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

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

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

Types of ouzo a and ac what is the difference

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

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

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

An AC type RCD will only respond to alternating leakage current. The shape of the curve of such a current should be sinusoidal. In what situations does AC leakage current occur? Damage to the insulation inside a household appliance (washing machine, refrigerator, water heater, etc.) and phase contact with the housing. There can be a lot of situations. AC RCD is the most common and widespread; it can be used everywhere.

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

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

All modern technology is made using semiconductors (diodes, thyristors, converters, etc.). It's hard to imagine a microwave or washing machine without electronic filling. Today, even energy-saving and LED lamps have a switching power supply inside. And remember how the LED strip is connected - through a switching power supply.

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

But it is not at all unnecessary to disassemble something and touch the electronic board with wet hands. Everything has its own service life and your household appliances are no exception; everything breaks down and fails at some point. The secondary switching inside the power supply may be damaged and penetrate the metal case, resulting in a current leakage that RCD AC may not sense.

Sometimes it happens that the passport of electrical equipment directly states that its connection must be made only through a type A residual current device. Here, as they say, there are no options, you need to follow the instructions.

The curve of a direct pulsating current has the shape of half sine waves. Taking into account the fact that type A residual current devices operate on alternating and pulsating currents, they are marked on the housing as follows:

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

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

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

Testing ouzo type a and ac, response difference

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

To provoke the operation of the residual current device, we will create a leakage of direct pulsating current and see how our devices work or do not work.

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

I bought a 1n5408 diode and will assemble a circuit using it to create a pulsating leakage current.

We apply an alternating voltage (sinusoidal) to the input of the diode, and at the output we remove a constant pulsating one. The shape of the curve will look like half-waves of a sine wave without changing its direction. Depending on the polarity of the diode connection (direct or reverse), a pulsating current will flow through the device in different directions.

We assemble the power supply circuit - diode - light bulb. To ensure correct operation, change the polarity of the diode.

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

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

The second in our experiment will also be an ouzo made by Hager, but of the AC type, which in theory should not feel the pulsating leakage current at all. But in practice it turned out to be quite the opposite and the AC-type Uzo Hager also sensed leaks and switched off.

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

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

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

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

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

The difference between the characteristics of RCD type A and AC

Residual current devices differ in design, internal structure (electromechanical and electronic), type of differential leakage current, time delay value and leakage current protection in single-phase or three-phase networks.

The type of leakage current can not only be purely sinusoidal 50 Hz, it can also be pulsating constant or continuous constant. The type of differential leakage current depends on the location of the fault. For example, a violation of the insulation of the device’s network wire, breakdown of the diodes of the rectifier unit of electrical equipment and leakage of pulsating direct current along the soot, onto the device body, etc.

There are several types of residual current devices.

AC type. This type of RCD is designed to trip when there is an alternating current leak. If a malfunction occurs in thyristor devices, rectifiers, that is, in such devices where the leakage current will be pulsating constant or constant, then the protection of the AC type RCD may simply not respond to it.

There is a possibility that the core will become saturated with a constant electromagnetic field, which will significantly reduce the sensitivity of the unit to protection from alternating leakage current or even lead to failure of the protection. It turns out that the operation of AC type protection may be completely disrupted due to the appearance of a pulsating direct or full direct leakage current. The RCD type AC is designated by the AC sign.

Type A. These devices are designed to work with such types of leakage currents as alternating and pulsating direct. They have a higher sensitivity to pulsating direct leakage current, and their cost is correspondingly higher.

If alternating leakage current appears when the insulation of network wires is broken, then pulsating direct current occurs when thyristors, voltage converters, computers, electronic circuits of washing machines, microwave ovens and other household appliances malfunction.

Almost all equipment today has an economical switching power supply; even LED lamps contain such power sources. Type A devices are marked as follows.

Type B. The circuit of such a device has protection against alternating leakage current, as well as protection against pulsating direct current and constant differential leakage current. This extensive type of protection is used in industry, but is not used in homes due to its high cost.

Type S. This version of the RCD is installed in houses and apartments as selective protection, which has a time delay necessary for the operation of lower-level RCDs.

Conclusion: Of course, type A devices have better protection. Some instructions recommend installing type A protection on a washing machine. Abroad, type A protection is also installed everywhere. Since almost all household appliances have switching power supplies and other elements that, in the event of a malfunction, can cause pulsating direct current, it is recommended to install a type A RCD.

When it is not possible to select an RCD of this type, install AC type protection. Some high-quality brands of these devices have increased sensitivity and respond well to pulsating direct leakage current. The probability of occurrence of pulsating DC leakage current is much lower than the occurrence of AC leakage current. Therefore, if a type A device is not affordable, install type AC protection. It is better to install speaker protection than not have it at all.

Our home is our fortress. However, over time, not only our house ages, the wiring wears out and can become damaged, and the possibility of weakening contact connections arises. As a result, the likelihood of electrical problems increases. There is a need to strengthen security.

Children left unattended may explore electrical equipment and receive severe electric shocks. Ordinary switches do not operate in this case; they react only to overloads and short circuits. Residual current devices will help turn your home into a safe haven. A high-quality unit will prevent electric shock to a person and prevent a fire.

The device, which helps to avoid a large number of unpleasant moments, is a housing made of dielectric material, inside of which there is a transformer. For reliability, its serviceability must be checked periodically.

A “Test” button has been created for this purpose. If you press it, it creates the effect of an artificial leak of electricity. A working device will work immediately after pressing this button. This check should be done once a month.

What to consider when choosing an RCD

In order to choose an effective and safe device, you need to know some factors:

• Understanding the purpose and principle of operation of the device you have chosen;
• Know exactly its parameters and characteristics;
• Study the regulatory documents supplied with the device.

An important role when choosing a machine is the age of your wiring, the condition and quality of the connections. Whether your apartment is new or old, whether there is a transformer substation nearby, the temperature conditions of the room where the electrical panel is installed - these are factors that influence the choice of a device that will protect you in any adverse situations.

A typical home electrical circuit diagram should look like this:

• Input electrical panel;
• Electrical panel on the lower floor;
• Electrical panel on the second floor;
• Each floor of the house has an electrical panel equipped with a group of automatic circuit breakers, individually for each apartment.

There are different types of RCDs, each of which performs specific tasks. Let's look at the indicators by which RCDs are classified.

Gradation:

• type of current leakage;
• response time;
• shutdown principle;
• number of poles.

Before making a purchase, you should determine exactly why you need the machine and what load it must withstand.

Types of devices

Depending on the type of current flowing through your wires, there are two types of devices:

• RCD type AC - protects against the effects of alternating current;
• RCD type A is protection against alternating and pulsed current;
• RCD type B – designed for use in industrial installations. It is triggered by leakage of alternating, direct and pulsating current.

At first glance, it seems that the issue is resolved, alternating current flows in all houses, therefore, we choose the AC type. However, modern household appliances, microwave ovens, washing machines, and most energy-saving lamps are equipped with a power supply that passes pulsed current through it.

Therefore, you can get an electric shock not only by trying to disassemble a faulty unit that is under voltage. Over time, any equipment wears out, which leads to damage to the secondary switching, which is why you can get an electric shock by touching the base of the household appliance.

An AC type RCD can operate on a pulse current, but with a long delay, and this can be dangerous to human life. European countries have long abandoned AC type machines; they are installed mainly on devices without electronics, such as underfloor heating or water heaters.

Often there are illiterate managers who do not know the difference between RCD type AC or A. It happens that they just want to get rid of stale goods. Unfortunately, the recommendations of electricians are also not always competent. AC protectors are a little expensive, but not more expensive than your life. The answer to the question of whether to choose an ouzo type A or AC is obvious.

Classification by response time interval

• RCD type S - has a response time from 0.2 to 0.5 seconds. It is better to use it if several other protective devices are installed in the circuit;
• RCD type G - trips after 0.06 -0.8 seconds.

Selective circuit breakers are used for cascade protection of a circuit. Their ultimate goal is to prevent the entire line from being de-energized, but to turn off only those areas where a leak occurs.

Division by technological design

Based on the principle of timely shutdown, a distinction is made between electromechanical and electronic units. An electromechanical RCD does not depend on whether there is voltage in the network or not, and is triggered directly when there is a current leak.

Electronic RCD, on the contrary, depends on the mains voltage and requires electrical power for its operation; therefore, it has become less widespread due to its low reliability.

If the neutral wire breaks, the electronic device stops working, and current dangerous to human life will continue to flow to the consumer.

However, progress does not stand still; manufacturers have taken into account the shortcomings of electronic protective devices and, thanks to this, the production of uzo-d has been established. These devices provide high-quality operation in the absence of voltage.

The question often arises of how to visually identify electronic and electromechanical devices. To do this, you need to carefully study the diagram shown on the product body.

The electromechanical ouzo transformer does not have a direct connection to the supply voltage. If you have an electronic protective device in front of you, then in the diagram you can see the board to which the conductors are connected.

Although an electromechanical residual current device is more expensive than an electronic one, for greater safety it is worth giving preference to it. Don't skimp on your health.

Division of devices by number of poles

There are two types of RCDs according to the number of poles: two-pole, which are installed in a network with a power of 220 volts, and four-pole for a network of 380 volts.

The most widespread in housing construction are two-pole circuit breakers, which are installed in apartment panels. Four-pole ones are designed to protect three-phase wiring and are most often used in industrial electric motors.

An ouzo socket will help increase the reliability of your apartment, which will ensure your safety when using any household appliance. And the ouzo-fork will protect you when operating devices in any adverse environmental conditions.

Installation in a household

You have made your choice; all that remains is the final stage, installation and connection of the device to the network. Installation of the modular device in the panel is carried out on a DIN rail, which is mounted on the mounting panel.

Then we connect it to the electrical protection circuit. If you are not confident in yourself, then entrust the installation of the device to a professional.

Be careful when choosing a residual current device. The safety of you and your loved ones depends on choosing the right characteristics of its parameters.

The device that saves people from electric shock is not yet popular in our country. It is gratifying that an increasing number of citizens are realizing the need to install it.

The devices are available in several versions and a potential buyer needs to know what types of RCDs exist and how to make the right choice.

The RCD compares the values ​​of the input and output currents of the serviced circuit. When a difference is detected, indicating that the flow of electrons is escaping into foreign objects, the device opens the contacts.

Current leakage occurs in one of the following cases:

• the user received an electric shock;
• a phase short circuit occurred to the grounded body of the device: an accident that also threatens the user with electrical injury;
• contact has occurred between live parts and grounded metal objects, for example, a building structure, which is fraught with fire.

Therefore, if there is an unauthorized loss of current, it is extremely important to quickly de-energize the circuit.

It must be understood that the RCD does not protect the circuit from overloads and short circuit currents. This function is performed by automatic switches. There are two-in-one devices that include an RCD and a circuit breaker. In everyday life they are called.

Selection of RCD based on leakage current setting and rated current

The leakage current setting is the main characteristic of the device. This is the minimum amount of current leakage that causes the device to operate. According to this parameter, RCDs are divided into two types.

The first type includes devices that protect against electric shock:

1. 6 mA. American and European standard. We do not use them because they are demanding on the quality of the wiring;
2. 10 mA. Through them and electrical receivers in rooms with high humidity (bathrooms, swimming pools, saunas);
3. 30 mA. For sockets and devices in dry rooms.

Type 2 includes fire protection RCDs, which have less sensitivity:

• 100 mA;
• 300 mA;
• 500 mA;
• 1000 mA.

There are always normal leaks in an electrical circuit (defects in insulation, connections, etc.) and the greater the length of the circuit, the higher they are. Therefore, there is no point in installing an RCD with a sensitivity of 10 or 30 mA, for example, at the entrance to a building - it will always trip.

The facility’s network is divided into groups and an RCD with the required sensitivity is installed in each. At the entrance to the building, a device with lower sensitivity and response delay is installed (more on this below) - for safety reasons.

Another important characteristic, like all electrical appliances in general, is. Depends on the load included in the circuit.

The fact is that with relatively small overloads, ordinary class B household circuit breakers do not turn off immediately. Their response time can reach 60 minutes, when the bimetallic plate of the thermal release heats up.

If the RCD is designed for the same rated current, it will operate with overload during this time, which will lead to failure.

Types of RCDs and automatic circuit breakers by type of leakage current

The circuits use different types of currents, which is why RCDs come in different classes:

In the operating instructions for washing machines and induction cookers, manufacturers directly indicate that the device must be connected via a type A RCD.

Varieties by time delay

RCDs are usually required to trip as quickly as possible when a current leak is detected. Modern devices operate in 0.02 - 0.03 seconds. But there are special models that operate with a deliberate time delay. They are called selective.

They are used as a backup for regular ones that control different socket groups. It is set at the input, before branching into groups.

The operating principle is as follows:

• While conventional RCDs function normally, in the event of a current leak they operate before the selective one, so that only one socket group is left without power;
• If one of the conventional RCDs fails and there is a current leak in its group, a selective one will operate.

In apartments, all consumers are combined into one group; accordingly, one regular one is used and there is no point in installing a selective one.

Here, to be on the safe side, it is enough to install one more usual one. Division into groups is used when installing wiring in private houses, for example, one group per floor.

There are two types of time delay device:

1. type S. Triggers in a period of 0.15-0.5 seconds. The letter “C” is placed after indicating the leakage current setting, for example, “100C”;
2. type G. Triggers in 0.06-0.08 seconds.

According to the operating principle

The comparison of currents is carried out in the same way. The coil is switched into phase and neutral, and when the currents are equal, the magnetic fields created by the coils cancel each other out. If the currents are different, a residual magnetic field will arise and it will induce an emf in the third coil.

Electromechanical

The EMF induced in the third coil causes the electromagnetic relay to operate, opening the contacts. This is the most reliable option and therefore the most preferable.

Its disadvantages:

• high price;
• large dimensions.

They prompted Chinese and other Asian manufacturers to develop an alternative - an electronic RCD.

Electronic

In electronic RCDs, the EMF in the 3rd coil is amplified by an electronic circuit before entering the relay. This approach made it possible to reduce the size of the elements and reduce the cost of the device. But there is also a significant drawback: the amplification circuit needs power, and if it disappears due to a zero break, the device becomes inoperable.

At the same time, all live parts remain energized, so there is a possibility of electric shock.

The latest models of electronic RCDs are supplemented with an emergency electromagnetic relay that de-energizes the circuit if there is no power to the amplifier circuit. But experts advise using such RCDs with caution.

There are known cases when electronic RCDs as part of automatic devices failed to operate after the circuit breaker tripped due to a short circuit.

In some models of electronic RCDs with a shutdown function, in the absence of power to the amplifier, the following are provided:

• time delay: the device does not turn off during short-term power failures;
• automatic restart: after the integrity of the neutral wire is restored, the device turns on automatically.

There are three ways:

1. according to the diagram shown on the case. A differential transformer is drawn on the electromechanical one; there is no supply voltage. The electronic symbol shows the amplifier board with power supplied to it. This method is suitable for a radio amateur who understands electrical circuits;
2. connecting one of the differential transformer coils to the battery is carried out using two wires, the RCD is first turned on. The electromechanical device will work during the experiment, the electronic device will not;
3. impact of a permanent magnet on the device. Before this, it is also turned on. The electromechanical version will turn off, the electronic one will not. The reliability of this method is not 100%: if the magnet is weak or incorrectly positioned, then the electromechanical device will not work either.

Externally, electromechanical and electronic devices do not differ, and therefore a potential buyer should be able to recognize them.

Classification by number of poles

There are two types of RCDs for different types of electrical networks; they differ structurally - in the number of poles:

• bipolar (2P). Designed for use in . There are two terminals on each side - for connection to phase and neutral;
• four-pole (4P). Used in 3-phase networks. On each side there are 3 terminals for phase conductors (phases A, B and C) and one for connection to the neutral. Four-pole devices can also operate in a 1-phase network if, for example, a 3-phase connection is only planned.

Selection by installation type

The devices are available in two versions:

1. modular. Equipped with structural elements for installation on a DIN rail, mounted in. Usually they serve a group of several outlets;
2. portable. Less common option. It is plugged into an outlet, after which an electrical appliance is connected to it. It can also be made in the form of an extension cord.

Video on the topic

About the types of RCDs and selection rules in the video:

So, for domestic conditions, in the vast majority of cases, electromechanical 2-pole RCDs with a leakage current setting of 30 mA or 10 mA (for wet rooms) class A with installation on a DIN rail are suitable.

A device that combines the functions of an RCD and a circuit breaker is more expensive than individual devices, but takes up less space in the panel. It is better to choose a difavtomatic device with an indicator that helps determine which part has tripped - the RCD or the automatic device.