Which ouzo to choose for your dacha. How to calculate the leakage current in the group line of an RCD (difavtomat)? Choice for an apartment

Content:

One of the devices of great importance in electrical engineering is the residual current device. Its main purpose is to disconnect the entire electrical network or its individual section from power by opening the contacts. This ensures protection against and prevention of fires. In modern electrical engineering, the use of these devices in many cases becomes mandatory, therefore, the question often arises of how to choose the right RCD. These protective devices They are used not only in single-phase, but also in three-phase networks under various loads, therefore, their selection is made depending on the specific operating conditions.

Purpose of RCD and principle of operation

The main task of the RCD is to neutralize currents when various damage occurs in electrical installations. The residual current device is the most effective protective device. Unlike fuses or circuit breakers, RCDs are capable of breaking a circuit in a split second and saving a human life.

The danger is not only the possibility of direct electric shock. Sometimes simply touching the parts of live devices and devices is enough. Therefore, protective devices must operate in a timely manner. In order to correctly solve the problem of how to choose an RCD for a home, the conditions in which it will operate must be taken into account.

The operation of protective devices uses the phenomenon of electromagnetism. In this regard, the design of the RCD includes coils with a magnetic core connected to current-carrying wires that transmit electricity to the consumer. At the same time, a magnetic flux occurs, which is the arithmetic sum of the currents flowing through these conductors. In this case, the incoming currents have a positive value, and the outgoing currents have a negative value. In the absence of leaks and short circuits, they will be equal and add up to zero. This state of the circuit indicates the serviceability of the installed equipment.

In the event of a leak, a partial reverse flow of current occurs through the grounding conductors, which leads to an imbalance. The difference in differential currents causes the excitation of magnetic flux in the core. Its value will be proportional to the difference in electric current. When a certain threshold is reached, the device is triggered and turns off the power supply to consumers.

How to choose the right RCD

In order to pick up best option residual current device, you need to know its basic parameters. Devices with different characteristics are used in specific conditions, which must be taken into account when choosing. The nature of leakage currents allows us to divide them into different types. This division depends on a smooth or sudden increase in current. RCDs with such characteristics are most widespread as they are most suitable for the widest operating conditions.

Triggering technology allows RCDs to be divided into electromechanical and electronic. In the first case, high-precision mechanisms are triggered as a result of leakage currents. These are the most reliable and expensive devices capable of operating under any conditions. Electronic devices are cheaper, however, for normal operation of the electronics, the use of external power is required. Their efficiency is significantly reduced when voltage surges occur. The response speed of RCDs allows their use in multi-level protection systems. This allows you to turn off all emergency sections individually.

There are other parameters that require knowledge of electrical engineering. Therefore, when choosing an RCD, it is best to seek help from qualified specialists. However, if the exact characteristics of the electrical network are known in advance, you can independently select the most suitable protective device. Among them, the most important are the following:

• Voltage. The RCD can be designed for a single-phase network with a voltage of 220 V or a three-phase network with a voltage of 380 V. The first option is usually used in apartments, and the second in private houses, dachas and cottages. If there are sections with one phase in three-phase wiring, then protective devices designed for 220 volts are used for them.
• Number of poles. In single-phase networks, two-pole RCDs are used, designed for one phase and zero, and in three-phase networks, four-pole devices are used, to which three phases and zero are connected.
• Rated current. This is also the throughput current of the RCD, which depends on the number and power of connected electrical appliances and equipment. Therefore, this indicator for a general (input) protective device must be calculated for all installed consumers. For linear RCDs, the total power is calculated based on the number of devices on a particular line. The RCD ratings set by the manufacturers are 16, 20, 25, 32, 40, 63, 80, 100 A.
• RCD leakage current. The value at which it is turned off. It also varies in ratings of 10, 30, 100, 300 and 500 mA. For ordinary apartments, a 30 mA device is best suited. With a lower current rating, the device will constantly respond to even minor fluctuations in the network and turn off the power.
• Type of leakage current. The symbols AC, A, B, S and G are marked on the body of the device. For example, AC reacts only to alternating leakage current, and B - to direct and alternating currents. The rest of the markings also correspond to certain parameters, including the device shutdown time delay.

What types of RCDs are there?

The main classification of residual current devices is based on their operating current. For example, devices respond to currents of 100, 300 and 500 mA. They protect wiring from fire in the event of insulation failure and short circuit. Typically, an incoming RCD is installed behind the electric meter and provides protection for the entire facility. For people, electric current becomes dangerous at 50 mA. Therefore, devices that protect against fire are not able to protect a person from electric shock. For these purposes, devices are used that turn off the network when the current reaches a value of 10 or 30 mA.

Protective devices differ in the number of poles and can be used in single- or three-phase networks. Each type of device has a different way of functioning. The markings on the body of the device must be correctly deciphered and you need to know exactly what it means:

• AC is a category of RCD used only in alternating current networks. Accordingly, the device responds only to alternating current.
• A - protective devices of this category operate not only with alternating current, but also with direct current.
• B - has more advanced functions and responds to three types of current. In addition to direct and alternating current, the device turns off with rectified differential current.
• S - devices with the ability to delay time when switched off.
• G - are also selective devices, but with a shorter time delay.

RCDs are also classified according to their technical design. This allows you to select a RCD of better quality. Most often, electromechanical devices are used that do not have their own power supply. They operate and shut down when a differential current appears.

Another type refers to electronic protective devices that require connection to external source nutrition. In this regard, the reliability of protection decreases, so such RCDs are used less frequently. When the auxiliary power is turned off, they turn off the network automatically, and when the power is restored, the network also turns on automatically. Some device designs do not provide for automatic switching on of the circuit when the power supply is restored.

How to choose an RCD based on power

Unlike circuit breakers that protect against overloads and short circuits, residual current devices are designed to protect against current leakage. The reason is faulty insulation of electrical appliances or contact of live parts with the housing. In these cases, the RCD is instantly turned off, the line is de-energized, and consumers are protected from electric shock.

In order to calculate the RCD by power, you need to know the total number of consumers connected to a given line. In the case when the question of how to select an RCD and a circuit breaker in terms of power is being decided, both protective devices must have appropriate values ​​that ensure their normal work. If the installation of circuit breakers is not provided for by the project, in this case the total power consumed by electrical appliances is calculated. As a rule, this value in a standard apartment in a multi-storey building does not exceed 25A.

When installing RCDs in private houses, it is recommended to divide all consumers into groups connected to separate lines extended to each floor, outbuildings, external lighting, etc. If the RCD has less power than the existing consumers, it will constantly turn off due to overloads. That is, the device will actually not work normally and will not be able to protect the line. Designed for a current consumption of 5A will help partially solve this problem.

How to calculate RCD

In order to calculate the protective device and solve the problem of how to choose an RCD based on power, the table of parameters will help you do this as quickly and accurately as possible. It is necessary to use two technical characteristics - leakage current and maximum current - to obtain the desired result. The calculations use a mains voltage of 220 V, with a frequency of 50 Hz.

Calculation and selection of the maximum current rating of the RCD is quite simple. It is necessary to establish the value of the total electrical power of devices and equipment turned on simultaneously. For example, if this indicator is 6000 watts, then the calculated current value will be equal to: I = P/U. Substituting the required values ​​into the formula, we get the result: 6000W/220V = 27A. The closest RCD from the standard range of rated currents will be 32A.

If the RCD is calculated based on leakage current, in this case a simplified scheme is used, according to which Various types protective devices are selected in accordance with the operating conditions of the objects:

• In ordinary residential premises - at 30mA.
• In bathrooms, kitchens and other rooms with high humidity and higher requirements for electrical safety - at 10 mA.
• At large facilities with electrical networks with a length of over 1000 m or at the input - 100 mA.

Quite often there is a need to select an RCD for a group of machines, the calculation of which is carried out according to certain rules. The installation of these devices in the circuit is carried out sequentially; the machines can be installed both before and after the RCD. The current values ​​of the circuit breakers must be lower than in the RCD, but not less than the actual current consumption. Correct calculation of RCDs and circuit breakers shows that in the event of overloads and short circuits, the circuit breaker will protect not only the line itself, but also the residual current device installed on it.

RCD current ratings

The rated currents of the main types of RCDs are 16, 25, 40 and 63A. This value corresponds to the current value that the device can pass through itself without time limits. Within this line, a selection of RCDs is made for the electrical panel of an apartment or private house.

The rated current value is necessary when deciding how to calculate an RCD for a group of machines. In this case, for protection, you need to select a circuit breaker with a rated current less than or equal to the rated current of the differential switch. Experts recommend choosing a rating one step higher than that of the machine, since it can pass through itself a current greater than the rated one for a long time. If the currents are equal, during this period the RCD may simply burn out.

Which RCD should be installed at the entrance to the apartment?

In modern high-rise buildings it is prohibited to use three-phase wiring, so many owners are wondering how to choose an RCD for an apartment. Meanwhile, there is nothing complicated here, since for single-phase wiring a two-pole device marked AC is used. Based on the leakage current, the RCD for the apartment is selected at the rate of 30 mA. Devices with a lower shutdown threshold may cause false alarms.

How many RCDs should I install in an apartment? It all depends on the total power of consumers. If it is too big, it is recommended to break it home network on separate lines and install a protective device on each of them. Additionally, a general RCD is installed at the entrance to the apartment to protect against fire if the insulation is damaged.

Often false alarms occur due to old electrical wiring. If these processes occur systematically, it may require complete replacement.

RCD at the entrance to the house

Unlike a standard apartment, a private house has an individual layout with a different number of rooms. Therefore, the question often arises, what kind of RCD to install in a private house? At such facilities, not only single-phase, but also three-phase can be used. Electricity of the net with voltage 220 or 380 volts. Therefore, in the first case, the same RCDs are used as in apartments, and in the second case, four-pole ones are used, where terminals are provided for three phases and a neutral wire.

In addition, the choice of RCD for a private house is carried out according to the type of current. However, it should be borne in mind that in private homes powerful electric motors are often started, a short time consuming powerful starting current. It is recommended to determine in advance which RCD and then choose required device, maintaining performance under these conditions.

Of great importance is the question of how to choose an RCD for a wooden house in order to protect not only from leakage currents, but also from fires. For this purpose, a multi-stage protection system is used, in which powerful devices prevent fires, and devices with a lower response threshold protect against current leaks. However, you should not install an RCD with a minimum cut-off current of 10A, especially if the power lines are long. A sensitive device will react to the slightest changes and cause false alarms.

How does an RCD work, where is it placed and why is it needed? If you find out the answers to these questions, your apartment or house will become more secure and safe to live in. After all, a residual current device (RCD) protects the home from fires in the wiring and the resulting troubles. Therefore, every prudent homeowner should become familiar with the design, installation method and calculation of its ratings.

RCD - what is it and how does it work

When we decipher the abbreviation RCD in electrical engineering, we mean a special unit that opens the circuit in the event of an emergency situation in the system. This situation primarily refers to a current leak in an apartment or house caused by a person who touched a bare wire or contact. In this case, the body will be used as a conductor through which the current will flow to the conditional ground, and a power surge will be recorded in the electrical network, measured in thousandths of an ampere (mA).

Conventional automatic fuses do not respond to such surges. They open the circuit only after detecting a current imbalance of 1 to 4 amperes (above the rated value). Only an RCD can save a person from a bare wire - a more sensitive breaker that responds to 10-30 mA. It is he who opens the circuit before the careless user has time to be afraid of the “bite” of the current. As a result, thanks to such a breaker, after contact with a bare wire, we are left with only unpleasant memories, and not serious injury or disability.

In addition, the RCD reacts to dangerous heating of the electrical wiring, which can be caused by either a short circuit or a jump in current characteristics caused by a fault on the line. The device also protects the network from connecting electrical appliances with excessively high power, which heat the wiring to boiler temperature, which is why in electrical engineering it is customary to use a special term - fire protection RCD.

Typical types of devices - 3 classifications

Why you need an RCD in an apartment or house, we have already figured it out. Now we should study the standard types of such interrupters. In this case, we will use three classification methods: by poles, by design features and by functional features. The first classification method involves dividing the product range of such devices into 2-pole and 4-pole groups. The module from the first group is installed exclusively in single-phase (household) electrical networks. Devices from the second group are installed on a three-phase (industrial) power supply network.

When choosing an RCD based on design features, we are dealing with two groups - electromechanical and electronic. The first includes non-volatile breakers that continue to operate even after the zero line in the wiring is broken. The second group includes volatile breakers that require constant power, since their main component is not a differential transformer, but an electronic board.

The third method - classification by functionality - distinguishes several types of breakers: AC, A B, F, G. The AC type is focused on sinusoidal current and increasing loads, and for such a device to work, both a sharp jump and a smooth increase in characteristics are enough. Type A responds to pulsating direct and alternating current, and loads can increase either gradually or intermittently. Type B is a classic industrial circuit breaker, and you most likely will not see it in an apartment, and F and G are fire protection RCDs used both in everyday life and in production.

Of course, the complete classification of breakers is not limited to the above methods, and in each case there will be a little more groups than we indicated, but the options mentioned are quite enough to understand which breakers should be used in an apartment or other residential premises.

How many and what kind of RCDs do you need for your apartment or house?

Before choosing an RCD for an apartment or house, we need to assess the needs and expectations of the home owner who needs such protection. So, with the help of such a breaker we want to protect ourselves from the following troubles:

• damage to household members electric shock;
• fire in the wiring, socket or electrical appliance itself;
• failure of expensive household appliances;
• short circuit or breakdown in a damp room (in the bathroom, for example).

At the same time, we need to select an RCD with the level of sensitivity we need so that such a device does not respond to “false calls” caused by electrical wiring. As a result, in a city apartment the following application scheme is practiced: a fire protection RCD on the central line, a separate breaker for the kitchen, a separate module for the bathroom and another device for all other rooms (corridor, living room, bedroom). Moreover, it is considered good form to use separate RCDs for water heaters and washing machines.

All apartment blocks are of the 2-pole variety and AC type. The only exception may be a block designed to fight fire - it is a G-type. In a private house, a slightly different scheme is practiced: a fire protection RCD on the central line and breakers for each branch supplying individual rooms. That is, the number of standard security modules should be equal to the number of rooms or functional areas in the home. Plus here you need to add separate RCDs for boilers and pumping stations.

"Home" devices can be either 2-pole or 4-pole types, depending on the number of phases in the home's power supply line. The fire protection RCD will be of F or G type, and the remaining modules will be of AC type. At the same time, for a private house it is better to choose a non-volatile version of the breaker - an electromechanical RCD.

How to calculate the parameters of a specific breaker

So, we have decided on the number of breakers and their layout, but the choice of RCD for a house or apartment does not end there. Before the purchase specific models we need to calculate their characteristics. Without this, the module will operate on its own, annoying the owner of a private house or apartment. To calculate the RCD as accurately as possible, electrical network designers use parameters such as the power of electrical appliances connected to the line, the amount of leakage current, and even the length of the wiring.

For example, calculating a breaker for a room with a total energy consumption of 5 kW, connected to a 220-volt meter with an 11-meter-long wire, begins with determining the maximum current consumption, in this case it is 22.7 A (5000/220). Next comes the determination of the leakage current in wires and electrical appliances - this is about 11 and 9 mA (phase current minus neutral current), after which we select from model range RCD with parameters closest to these values ​​- 22.7 A and 20 mA. This will be a 25A/20mA machine, and before calculating the final parameters, all values ​​must be increased by at least 30 percent. As a result, we will have to install a 32A/30mA breaker on the service line of such a room. That's all, now you know which RCD to choose in this case.

If long calculations tire you, instead of making an exact calculation, you can use the standard recommendations for breaker characteristics, which are as follows:

• The fire module requires parameters at the level of 62A/300 mA.
• A 16A/10 mA module is suitable for the bathroom and nursery.
• In rooms without energy-intensive electrical appliances (refrigerator, washing machine or dishwasher), you can install a 25A/30mA unit.
• It is better to install a 40A/30 mA breaker on the power line of a boiler or kitchen (or other energy-intensive room).

If you remember this data, you will not need to make complex calculations and select RCDs based on power and other parameters. And don’t let the high current values ​​scare you - at 40 amperes the unit does not disconnect from the network (like a machine), but completely melts. And 30 mA of differential current, at which, will not scare even a teenager.

How to install the device - example with a boiler

Technically, it is very easy to install an RCD - strip the contacts of insulation and secure them with clamping screws.

Let's look at an example of connecting a breaker to a Termex boiler:

• We test the wiring contacts and find the line and neutral.
• We insert the neutral into the RCD socket marked with the letter “N”.
• We insert the line into the free socket on the same side. At the same time, in order for the breaker to start working, the connection to the network can be made both from the top and from the bottom of the unit body.
• We connect the free contacts in the RCD body with the corresponding connectors of the boiler.

Ready! Now the electrical appliance will work under protection. Just don’t forget to test the RCD at least once a month. To do this, just press the "Test" button on the case. And if the breaker opens the circuit, then it is fully operational.

The increase in the number of household appliances increases the risk of electrical injury during their operation. Therefore, it is recommended to install protective systems in premises that prevent current leakage.

To ensure stable operation and safe use of devices, it is necessary to correctly select and install the RCD. Before purchasing, you should evaluate the operational features of the room, the type of electrical wiring and decide on the connection diagram of the protective device.

Do you doubt that you can cope with the task? We will tell you how to choose an RCD, what parameters are important to consider to ensure normal functioning equipment, and which manufacturers can be trusted.

It was invented to prevent accidental electric shock from contact with household and industrial electrical appliances.

It is based on a transformer with a toroidal core, which monitors the current strength at “phase” and “zero”. If its levels diverge, then the relay is activated and the power contacts are disconnected.

You can check the RCD by pressing the special “TEST” button. As a result, a current leak is simulated, and the device must disconnect the power contacts

Normally, any electrical device has a current leakage. But its level is so low that it is safe for the human body.

Therefore, RCDs are programmed to operate at a current value that can cause electrical injury to people or lead to equipment breakdown.

For example, when a child inserts a bare metal pin into an outlet, electricity will leak through the body, and the RCD will turn off the light in the apartment.

The speed of operation of the device is such that the body will not experience any negative sensations at all.

The RCD adapter is convenient because it allows you to quickly move between sockets. It is suitable for people who do not want to install stationary protective devices

Depending on the power of the connected equipment, the presence of intermediate protective devices and the length of the electrical wiring, RCDs with different limiting values ​​of differential currents are used.

The most common protective devices in everyday life are those with threshold levels of 10 mA, 30 mA and 100 mA. These devices are sufficient to protect most residential and office premises.

It should be remembered that the classic RCD does not protect electrical wiring from short circuits and does not disconnect power contacts when the network is overloaded. Therefore, it is advisable to use these devices in combination with other electrical protection mechanisms, for example.

Classification of protective devices

Despite the simplicity of the internal structure, the choice of RCD models on the market is quite large. Each device has a certain set of technical parameters that cannot be adjusted during operation.

The manufacturer and size of the RCD do not affect the possibility of sharing within the same circuit. They can be mounted in any combination

To facilitate the selection of RCDs, options for classifying these devices should be considered.

1. By response speed RCD mechanisms are divided into conventional and selective models. The former disconnect power contacts almost instantly, while the latter disconnect with a delay. Selective RCDs are used in multi-level systems where the sequence of operation is important.
2. By type of relay RCDs are divided into electromechanical, which breaks the contact mechanically, and electronic, which prevents the flow of current using a semiconductor circuit.
3. By type of current. RCD type AC is disconnected from alternating current leakage, type A – from alternating and direct current.
4. By additional functions: without and with network overload protection. RCDs with a short circuit or high current trigger mechanism are usually called difavtomats.
5. By design. There are RCDs that are attached to a DIN rail, to the wall, as well as devices in the form of a socket, a portable device, or an adapter.
6. According to operating voltage: for 220V, 380V, combined.
7. By energy dependence. There are RCD models that are capable and unable to disconnect the power load in the absence of operating voltage.
8. By number of connected poles: two-pole and four-pole.

To choose the right RCD, it is not enough to know it specifications. In order for the device to effectively perform its protective function, when purchasing it, you need to take into account the length of the home electrical wiring, the power of the connected devices and some other parameters.

Rules for choosing protective devices

Before purchasing an RCD, you can visit electrician forums to seek advice on the reliability of a particular manufacturer.

However, it is necessary to select the maximum and threshold current, number of poles, mounting scheme and other technical parameters strictly individually, based on the characteristics of the room and electrical wiring.

Selecting a device by power

The residual current device does not control the power consumption of connected devices, but has limitations on the maximum current flow.

Conclusions and useful video on the topic

Selection of RCD with consideration of options, as well as explanations of the features of various connection schemes:

Rules for choosing an RCD, part 1:

Rules for choosing an RCD, part 2:

The choice of a suitable RCD, especially when installing two-level systems, is best left to professionals.

It’s easier to invite an experienced electrician into your home once and consult with him than to change an unsuitable product in a store. After all, the health and lives of loved ones who will use household electrical appliances are at stake.

Do you have anything to add or have questions about choosing a protective device? You can leave comments on the publication, participate in discussions and share your own experience in selecting an RCD for a house or apartment. The contact form is located in the lower block.

RCD is a residual current device. An electromechanical device used to protect people from electric shock. In addition, the RCD protects the home from fire caused by poor insulation of electrical wiring.

From a physics point of view, the main function of an RCD is to protect the electrical network from too high leakage currents by de-energizing when the permissible norm is exceeded. This device, which is also called a residual current switch (RCS), is included in the standard electrical equipment for the home, regardless of whether it is an apartment in a high-rise building or a wooden cottage.

Choosing an RCD is a step that must be approached responsibly, since an incorrectly selected differential switch may either not operate at the time of an accident, or, on the contrary, may operate too often, de-energizing the entire home.

Please note that the RCD does not protect against short circuits. This is what machines are designed for.

Operating principle

In order to choose the right RCD for a private house or apartment, you need to understand on what principle this unit generally works, which is not yet quite familiar to the Russian consumer.

The residual current device is connected to the network in series after the input circuit breaker and the electric meter. A single-phase RCD (for a standard 220 V network) has 2 terminals for zero and a phase, three-phase - 4 terminals: 3 phases and a common zero.

The basis of its operation is to compare the parameters of the incoming and outgoing current. Generally speaking, how many amperes go to all current consumers at the input, so much should be at the output.

If there is a difference between the input and output current, it means that there is a current leak somewhere in the apartment. The cause of its occurrence may also be human contact with a bare wire (phase). In this case, the RCD de-energizes the section of the network that is connected to it.

The minimum triggering threshold of the RCD is 30 mA - this is the so-called “non-release threshold”. With an alternating voltage of 220 V with a frequency of 50 Hz, a current of 30 milliamps causes convulsive muscle contractions - a person cannot unclench his fingers.

In this case, a RCCB with a threshold value of 30 mA should trigger preventively when the leakage current is already 15 mA.

How to choose the right one

To choose an RCD for an apartment, cottage or country house, you must first decide on the level of security that you plan to achieve.

The first thing to consider is the type of wiring. If the wiring is old, then installing a current differential switch is pointless: it will almost certainly contain leakage currents. If you select and install an RCD with a limit of 30 mA, it will trip too often.

If you install a device with a higher shutdown threshold, then it will have no practical meaning.

In addition, many brands of VDTs are not designed to work with aluminum wiring, which was the standard for apartments in houses built in the USSR.

Selection algorithm

When making the desired denomination, we are guided by the following step by step instructions. So, you need:

• make sure that the quality of the wiring allows the use of a residual current device;
• determine the number of consumer groups to which RCDs will be installed;
• determine the number of protection levels.

The calculation and installation of this equipment is carried out simultaneously with the calculation and installation of the entire electrical network. The RCD always comes “complete” with automatic switch nutrition.

There is a rule. The RCD in terms of power, that is, in terms of the current passed, should be set one step higher than the rated current of the input circuit breaker. That is, if the machine is designed for a current of 20 A, then the RCD should be 40 A, and this is what you should choose.

Rated and differential current

The characteristics of this device will always indicate designations of approximately this type: 25/10 mA, 40/30 mA, etc. These are the parameters of the rated and differential current at which the device operates. The rated current is expressed in amperes (A), this is the total value of all currents that can pass through the device in normal operation, indefinitely.

Let's give an example. A group of consumers - sockets and lighting of one living room - is powered from a separate 16 A circuit breaker. According to the standard, the circuit breaker can withstand a load of 1.13 of the rated value for an indefinitely long time, and of 1.45 of the rated value for up to 1 hour.

This standard does not apply to protective devices, so if several powerful consumers are plugged into the sockets, whose total current is, say, 17 A for several hours, the machine will not turn off, but the RCD may fail.

The differential current, expressed in milliamps (thousandths of an ampere), is the leakage current at which the RCCB must operate. To protect people from electric shock, devices with a differential current limit of 10-30 mA are used. As fire protection - an RCD with a limit of 100 mA.

The main thing is balance

When calculating what kind of RCD can be installed in an apartment or private house, how many of these devices are needed and what power, take into account that the proportion works here: the lower the differential current limit, the more often the device will operate.

Therefore, it would be irrational to choose a high-precision device for the common input at the electric meter. The home will lose power quite often, especially if there are problems with the wiring. But even a device with a high switch-off threshold will not protect against electric shocks. It will provide only fire protection.

Therefore, in practice, two main connection schemes are used, conventionally simple and complex. Simple is the most common option. One input circuit breaker - one protection device with a threshold selected empirically.

If too frequent triggering is detected at 30 mA, then either the RCD needs to be replaced with a similar one with a higher threshold, or the “problem” group of consumers must be identified and a separate device mounted on it, since the current load is summed up.

The second scheme involves differentiated wiring with allocation:

Protective devices installed on each group in accordance with its permissible leakage current will ensure de-energization in the event of an insulation breakdown of only this group of electrical appliances.

Electronics or electromechanics

Choosing an RCD - which one to prefer - electronic or electromechanical? There are two types of such devices on the market. The difference between them is the type of trigger mechanism. cheaper, but has a significant drawback: it only works with external power.

People who believe that if there is no food there is no danger are mistaken. If the neutral wire breaks, the light will not light up, but the power will remain in the phase. There is still a danger of current leakage and, accordingly, electric shock. Therefore, remember: electromechanical ones should be considered the best RCDs. They do not depend on external power.

You can distinguish one type of RCD from another by the following characteristics:

• marking. Electronics always have a triangle with the letter “A” on the diagram—current amplifier;
• using a battery. When a regular battery is connected to the device, the electromechanics are activated, but the electronics are not;
• using a magnet. An electromechanical RCD that is turned on will turn off if a magnet is brought near it.

It is worth choosing an electromechanic for a private home, where the quality of the wiring is usually worse than in an apartment, and the likelihood of a burnout or break of the neutral conductor is higher. Simply due to the fact that part of the wiring of a country house or cottage is always located on the street and is exposed to the external environment.

Which brand to prefer

The electrical engineering market is oversaturated with products from different manufacturers, so to avoid mistakes, it is recommended to choose an RCD from a well-known company. These include ABB, AEG, Siemens, Legrand, Schneider electric.

These are world-famous companies that produce truly reliable electrical equipment. If you have a limited budget, then you should pay attention to domestic brands, you can choose DEK or Austro-UZO.

And finally

Before you finally choose a protection device, make sure that the marking contains the letter A or AC. Only these RCDs are suitable for domestic use. The difference between them is that AC class devices do not provide protection against pulsating current, that is, they are not suitable, for example, for working with a washing machine.

According to the PUE, residential properties must be connected to the power supply network through a residual current device (RCD). Any electrician will tell you that this device must be selected very carefully. How exactly to do this and why it is so important - this is what we will talk about now.

Why should an RCD be of high quality and reliable?

Types of RCD

The high demands placed on the RCD will seem quite justified if you understand the purpose of this device. It has only one function: to turn off the power supply if there is a current leak of a certain (threshold) value. A current leak is not fraught with harmless economic damage, as it might seem at first glance, but with much more serious consequences - it always indicates that one of the following situations is occurring:

• a person or animal has been struck by an electric shock;
• due to insulation damage, contact has appeared between a current-carrying element and some grounded metal structure, which can lead to a fire;
• the grounded body of any device or equipment is energized, as a result of which the user who touches it runs the risk of receiving an electric shock.

Thus, no less than the user’s life depends on whether the RCD works at the right moment. Therefore, you should never skimp on the quality of this device.

What you need to know about RCDs

The main element of the RCD is a differential transformer consisting of three coils. The first is connected to the phase, the second to the neutral conductor. In this case, the currents flowing through these coils generate magnetic fields with oppositely directed lines of force.

If the currents in the phase and neutral conductors are equal, then the geometric sum of the field lines will be equal to zero, that is, they will simply destroy each other. If the currents differ, then a residual field will form in the device, which will excite a current in the 3rd coil, and it, in turn, will force the shutdown relay to operate.

Note. The current that causes the RCD to trip is called differential current; accordingly, the RCD is also called a residual current switch.

Thus, if we say accessible language, The RCD compares the currents at the input and output of the circuit connected to it, and if “debit and credit do not match,” it blocks the supply of electricity. Two important conclusions can be drawn from this:

1. The RCD does not protect against overcurrents (short circuit) or overloads, since in such situations the currents at the input and output of the circuit remain equal (there is no leakage). Thus, this device cannot be considered as an alternative to a fuse or circuit breaker - at least one of these devices must be installed at the entrance to the apartment or house. Instead of separate RCDs and circuit breakers, you can use a so-called differential circuit breaker, in which both of these devices are combined.
2. The RCD will not turn off if a person touches the live element and the neutral wire at the same time. In this case, there will be an electric shock, but there will be no leakage - all the current will remain in the circuit.

Therefore, even with an RCD, one must not lose vigilance: live parts must be protected by casings, potentially dangerous places must be fenced off and marked with warning symbols and inscriptions.

Device characteristics

The most important characteristic of an RCD is the differential current setting, that is, the minimum value of the leakage current at which the device will disconnect the circuit. It is most often displayed in milliamps (mA) and can be 6, 10, 30, 100, 300 and 500 mA. This parameter is also called the sensitivity of the RCD: the lower it is, the more sensitive the switch is.

Another important characteristic is the response time of the device, that is, the duration of the period between the appearance of a leak and the shutdown of the RCD. Obviously, this period should be as short as possible, but there are special RCDs that are triggered with a time delay. They will be discussed below.

The third parameter is the rated current of the RCD, that is, the maximum current that the device can withstand without failure.

Calculation of RCD parameters

When calculating RCD parameters, manufacturers take into account the following data:

1. A current of 50 mA is considered dangerous to humans. Therefore, all RCDs designed for protection against electric shock have a differential current setting of no more than 30 mA. Switches with a higher setting are fire protection.
2. The response time is ensured so that in the event of an electric shock, fibrillation of the heart muscle does not occur. A period of 20–40 ms is considered safe in this regard.
3. Each current strength corresponds to its own heat generation power. For example, with a current leak of 500 mA, 100 W of heat is generated. Based on this, the differential settings. current of fire-fighting RCDs does not exceed 500 mA.

The lower the ignition temperature of the building material of the building, the lower the leakage current setting of the fire protection RCD should be.

Criterias of choice

Now let's see how to select an RCD depending on its operating conditions.

Rated current

The rated current of the RCD must be one step higher than the circuit breaker installed in front of it. Thus, after a 16 A machine it is necessary to install an RCD with a rated current of 25 A, and after a 40 A machine - with a rated current of 50 A.

It would be a mistake to install an RCD with the same rated current as the machine: the circuit breaker, although triggered quickly, is still not instantaneous. So in the event of an overload, during its operation time, a current higher than the rated current will flow through the RCD. This time may be quite enough for it to fail.

Differential current (leakage)

Selecting the differential setting current, you should first of all take into account the amount of rated current flowing in the circuit. The point here is this: if you install an overly sensitive RCD at a high current, frequent false alarms will occur. Acceptable values ​​of the leakage current setting for rated currents of different values ​​are shown in the table:

However, as mentioned above, protection against electric shock can only be provided by an RCD with a leakage current setting of up to 30 mA inclusive. More precisely, for dry rooms - 30 mA, for rooms with high humidity (this includes bathrooms) - 10 mA.

To be able to install such RCDs, a section of the network with a large rated current is divided into several subsections (all consumers are divided into several groups) and each of them is equipped with its own differential switch. Current with sufficient sensitivity.

Let us draw the reader's attention to one exception: in networks with a “TT” type grounding system, it is mandatory to install an RCD with a leakage current setting of 30 mA, regardless of the rated current.

Note. Imported RCDs with a leakage current setting of 6 mA are produced to US standards - according to the requirements of local standards, the sensitivity of an RCD that provides protection against electric shock must be within the range of 4 - 6 mA.

Please also note that there are RCD models with an adjustable differential setting. Current, and it can be adjusted both discretely and smoothly.

Device type

RCDs are divided into several types according to two criteria. The first sign is a type of leakage current:

The second sign is the response time. Conventional RCDs, as mentioned, turn off 20 - 40 ms after the leak appears. But there are varieties that operate with a time delay:

These “inhibited” switches are installed to protect the usual ones. The connection is organized according to a cascade scheme: an RCD with a delay is installed on a common line, then the line branches into several groups and a regular RCD is installed on each of them. If a failure occurs with one of the conventional devices and it does not react to the leak, after a split second the common RCD will trip.

RCD design

According to their design, differential switches. Currents are divided into two types:

1. Electromechanical. They consist only of a differential transformer (see above) and a shutdown relay.
2. Electronic. Additionally, they include an electronic amplifier, which amplifies the current arising in the third (control) coil of the differential transformer in the presence of a leak. By equipping the RCD with an amplifier, the manufacturer has the opportunity to use a less powerful differential. Transformers and electronic switches are more compact and less expensive than electromechanical ones.

It would seem that the choice should definitely be made in favor of an electronic RCD. But you should know that not all of them are reliable enough. The point is this: an amplifier, like any electrical device, needs power and in the absence of it the switch cannot work. The power, of course, is taken from the circuit being serviced, that is, the RCD amplifier is connected to it at the very beginning in parallel with other loads.

Let us now imagine that the neutral wire breaks somewhere above the RCD (most often, the conductor is disconnected from the neutral bus). The integrity of the phase was not violated, therefore, all current-carrying elements remained energized, but the circuit was open, which means that all consumers, including the RCD amplifier, are inoperative. That is, the user will not be able to turn on any electrical appliance.

But if he touches, for example, a bare wire or a housing that has suffered a breakdown, he will receive an electric shock.

By the way, the likelihood that the user will touch a current-carrying element is quite high: seeing that the device is not working, 9 out of 10 citizens will think that this is happening precisely because of the lack of voltage, and will lose their vigilance.

So, in such a situation, if a person is struck by electric current, the electromechanical RCD will work, but the electronic one will not, since its amplifier will be inoperative due to lack of power. To increase the reliability of electronic RCDs, they began to be equipped with an additional disconnecting mechanism that is triggered when the amplifier's supply circuit is opened - this is the model you need to look for.

At the same time, it makes sense to find an option that “can” turn on automatically when the power is restored, otherwise the RCD will have to be turned on manually every time after a power outage.

We should also talk about how to recognize which RCD you are holding in your hands. There is no direct indication of its type in the form of the inscription “electronic” or “electromechanical”, and even sellers often cannot clarify the situation. Here's what to do:

1. First of all, look at the diagram of the device shown on it itself. Electronic RCDs must include an amplifier - some kind of symbol to which power is supplied. In the vast majority of cases, the amplifier is indicated by a triangle. Nothing like this will be shown on the electromechanical RCD diagram.
2. If, due to lack of experience, you are unsure about the correct interpretation of the diagram, pass through one of the poles RCD current by connecting it to the most ordinary battery. Before this, of course, you need to remember to turn the device to the “on” position. If it turns off, then you have an electromechanical model. If not, reverse the polarity of the battery to allow current to flow in the opposite direction. If this time the switch does not work, then it is definitely electronic.

If there is a permanent magnet, bring it to the front panel of the RCD and move it slightly. The electromechanical switch will turn off during these manipulations, but the electronic switch will not.

Manufacturers

Today, the highest quality products are offered by manufacturers from Europe and the USA. First of all, these are companies:

• "ABB" (Sweden + Switzerland);
• Legrand, Schneider Electric (France);
• Moeller (German company, but recently acquired by Americans);
• General Electric (USA).

Of course, RCDs from these manufacturers are relatively expensive.

Devices from Siemens (Germany) are somewhat cheaper, but in terms of quality they are slightly inferior to RCDs from leading companies.

Products from domestic manufacturers may vary greatly, since some factories are owned by foreign investors. For example, a plant that produces RCDs under the Kontaktor brand is owned by French company"Legrand". This determines both the quality - it is much higher than that of many other domestic brands, and the price - it is comparable to the cost of a European-made RCD.

The following settled in the middle class:

• Kursk plant "KEAZ";
• DEKraft company.

The latter is notable for the fact that there are almost no negative reviews of its products online.

But IEK devices, on the contrary, are criticized quite often. Users report that they hum even under moderate loads and have a flimsy body that is easily deformed when the clamping screws are tightened. However, IEK brand equipment is quite popular because it has a very attractive price.

Devices from the well-known Chinese manufacturer EKF Electrotechnica can be included in the same category as the products of the IEK brand, both in price and in quality. But at the same time, the “Chinese” are distinguished by a rather long warranty period, for example, for circuit breakers it is 5 years. For comparison, the warranty for similar products from the KEAZ plant is 2 years.

Let us remind the reader once again that the quality of the RCD is often a matter of life and death, so it is not worth purchasing switches from dubious and little-known manufacturers for the sake of saving money. We should also not forget that products from well-known brands are actively counterfeited, so it is better to purchase RCDs in large stores that work directly with the manufacturer, or from official dealers.

Rated voltage

When choosing an RCD, be sure to look at whether it is 1-phase or 3-phase. In the first case, the rated voltage of 230 V will be marked on the case, in the second - 400 V.

Installation method

It is useful to know that, along with stationary RCDs intended for installation in a switchboard on a DIN rail, portable RCDs are produced. They are similar to a regular extension cord - they are plugged into an outlet and at the same time they themselves have several outlets for connecting electrical appliances.

It should be taken into account that the cost of such switches is significantly higher than that of stationary models.

Functionality check

All modern RCDs have a button labeled “TEST” (test). When you press it, current is supplied to a special test wire, as a result of which the RCD, if it is operational, should turn off. But there are two important points to consider:

TEST button

1. Turning off the RCD when you press the “TEST” button only indicates the integrity of the internal circuits, but this fact does not guarantee that the characteristics of the device (breaking leakage current and response time) comply with regulatory requirements. Therefore, do not lose your vigilance and if you purchase an RCD in a small store or market, ask to see the certificate.
2. In the same way, the operation of a switch that has already been installed in place when this button is pressed does not mean that it is connected correctly. It is likely that when you press the “TEST” button, the device will turn off, and will ignore the real current leakage due to a connection error.

If you want to truly test the performance of the RCD, you need to invite a professional electrician and ask him to perform a current leak test. We specifically draw the reader’s attention to the fact that this operation should be performed by a specialist.

Features of operation: Once a month, it is recommended to check the RCD using the " buttonTEST".

Connecting RCDs and circuit breakers

If electrical consumers in a house or apartment are divided into several groups, each of which is protected by its own circuit breaker, then in order to save money, you can install one RCD for 2 - 3 such groups. Today, it is possible to organize a connection in this way in almost any household network: among modern RCDs with a differential setting. current 30 mA, there are models designed for fairly high rated currents - up to 100 A.

When selecting an RCD for a group of machines, you should take into account the rated current of not only the higher-level machine, but also the lower ones. Let's explain with examples.

Example 1

Scheme for example 1

Let us recall that in the general case it is recommended to install an RCD with a rated current that is one step higher than the rated current above the installed circuit breaker. But in this case, as you can see, each of the two RCDs does not exceed the rated current, but, on the contrary, is inferior to the input circuit breaker: its rated current is 50 A, while the rated current of each of the RCDs is only 40 A.

However, the diff switches current are reliably protected from overload: the total rated current of the machines connected to each of them is only 32 A (2x16 A), which is 20% less than the rated current of the RCD of 40 A.

Example 2

The following scheme is not so reliable:

Scheme for example 2

The rated current of the 1st RCD is 25 A and the input circuit breaker with a rated current of 40 A does not protect it. But there is no risk of overloading this device, since the current passing through it cannot exceed 22 A (6 and 16 A circuit breakers are connected to the RCD). But the 2nd RCD, designed for a rated current of 40 A, can burn out: it is not protected by the circuit breakers connected to it, since their total rated current is 58 A (3x16 + 10), and the input circuit breaker is protected, so to speak, end-to-end .

If there is an overload, then before the input circuit breaker is triggered, a current higher than the rated one will flow through RCD No. 2, as a result of which it may fail. It is recommended to either install an RCD with a higher rated current (the next level is 50 A), or protect it with an additional circuit breaker with a rated current one step lower (32 A).

Example 3

But this scheme is clearly incorrect:

Scheme for example 3

Both RCDs with a rated current of 40 A are not protected by either the upstream circuit breaker (50 A) or the downstream ones (total rated currents are 57 and 48 A).

The optimal option for connecting an RCD

If there are several RCDs with their own group of circuit breakers, then it is very important not to mix wires from different groups. It is better to provide each group with its own zero bus - when all consumers are connected to a common zero bus, false alarms of the RCD are possible. The connection with individual buses is shown in the following diagram. Also shown here is the connection of a selective RCD.

RCD connection diagram

Red indicates phase (L), blue indicates neutral conductor (N), yellow-green indicates ground (PE).

As you can see, a selective RCD with a leakage current setting of 300 mA (position 3) protects RCDs 7 and 14 with a leakage current setting of 30 mA and at the same time protects the lighting circuits (circuit breakers positions 5, 6, 12). Protect the lighting wiring of the RCD with the differential setting. a current of 30 mA does not make sense, since here the probability of electric shock is practically zero.

It is understood that the differential machine 13 serves a dedicated line intended for connecting, for example, a computer or washing machine, therefore the neutral conductor from it is laid directly to the load, and not to the neutral bus.

Additional zero buses are indicated by pos. 11 and 18. Groups of sockets 2, 3, 4 are connected to the first one and a wire is laid from it to RCD 7; to the second - groups of sockets 5, 6, 7, the bus itself is connected to RCD 14.

Note that this circuit has the same drawback as that shown in example No. 2: the rated current of the input circuit breaker (item 1) is the same as the RCD pos. 7 and 14 - 40 A, while the total rated current connected to each of these RCD of automatic machines is 3x16 = 48 A. For greater reliability, an RCD designed for a higher rated current should be installed.

When connecting an RCD to a group of machines, identifying the location of the leak is quite simple. For example, the RCD, pos. 7. It is necessary to turn off the automatic machines pos. 8, 9 and 10, then turn on the RCD and turn on the mentioned machines one by one. As soon as the circuit breaker with a leak is turned on, the RCD will immediately turn off.

Whether it will be able to save your life in the event of an emergency depends on whether you have chosen and installed the RCD correctly. Therefore to this issue should be approached with all due care. The recommendations outlined in our article will help you avoid mistakes that could be fatal.