The purpose of the RCD has already been repeatedly mentioned, and clearly its installation in a modern household electrical network is the most important protection of a person from electric shock. But how to choose an RCD? Based on what parameters? How to calculate the device for a particular protected consumer? Let's try to figure it out.

To make the right choice of an RCD, you need to understand its purpose, main characteristics and parameters. When you buy a device, pay attention to its case, it contains all the important information. So that these numbers and letters tell you something, we will analyze each of them separately.

Appointment

The most important thing to understand is that the circuit breaker protects the electrical network from overcurrents, and the RCD protects the person. If, as a result of a breakdown of insulation, a potential appears on the body of an electrical appliance, when you touch it, there is a possibility of getting an electric shock. To prevent this from happening, immediately when a leakage current occurs, the residual current device will react and disconnect the damaged section of the circuit.

It's important to know! The RCD does not protect against overloads and short circuits, therefore, circuit breakers must be connected in series with them in the circuit.

Trademark

Speaking of the brand, we are, in essence, going to analyze the value for money. The fact is that there is an unspoken classification of all RCD manufacturers according to their territorial location - European, Asian and Russian models.

One way to spot a fake video:

Each of them has its own specific features:

1. Both a fire-fighting RCD and a device that protects people from electric shock, produced in Europe, will cost an order of magnitude more expensive than models in Russia and China. But this price guarantees quality and reliability. It will not be superfluous to know that some European companies, in addition to the main high-quality assortment, produce RCDs for the markets of other countries with the same reliability, but with underestimated technical characteristics.
2. Domestic manufacturers offer RCDs with a lower price than their counterparts from Europe, nevertheless, they meet all the regulatory requirements of Russian standards. So far, the retail network of Russian manufacturers is not so strong, and the devices themselves are not able to compete with Asians in terms of price, with Europe in terms of quality.

1. RCDs of Asian manufacturers are in the greatest demand in the world. Some manufacturers from Asia enter into contracts with a supplier of products to the Russian market, and in this case they release devices under the trademark of Russia.

Before choosing a RCD trademark, decide what means you have at your disposal for equipping an apartment or in a private house of protective automatics. Most preferred firms:

• Swiss "ABB";
• French Legrand and Schneider Electric;
• German Siemens and Moeller.

Among domestic manufacturers, the most widely used products are:

• Kursk plant "KEAZ", the average price and quality, the company gives a two-year guarantee for the manufactured RCDs, which testifies to the reliability of the products;
• The Moscow firm "Interelektrokomplekt" ("IEK"), the products do not always receive positive reviews, nevertheless, the demand for it is great due to the low cost;
• Ulyanovsk plant "Kontaktor", it is part of the group of companies "Legrand", which affects the quality of products and, accordingly, the price;
• a relatively young St. Petersburg firm "DEKraft", on the Russian market it represents the world-famous company "Schneider Electric".

As for the Chinese manufacturers, the RCDs they produce are a direct competitor to the devices of the Russian company IEK. The price and quality are approximately at the same level, while the warranty period for the Chinese product is five years.

main parameters

After the trademark on the case, the main ratings and operating characteristics of the RCD are indicated.

1. Model name and series. Please note that here you will not always see the letters RCD, some manufacturers designate this device as RCCB (residual current circuit breaker).
2. The magnitude of the rated voltage and frequency. In the Russian power system, the operating frequency is 50 Hz. As for the voltage, for a single-phase network in an apartment it is 220-230 V. For a private house, a three-phase network is sometimes needed and the operating voltage will be 380 V.

RCD characteristics in the video:

1. The rated operating current is the maximum value that the RCD can switch.
2. Rated differential breaking current. This is the amount at which the device is triggered.
3. Also, the temperature limits of the RCD operation are indicated here (minimum - 25 degrees, maximum + 40).

1. Another current value is the rated conditional short-circuit current. This is the maximum short-circuit current that the device will withstand and not turn off, but provided that a suitable automatic machine is installed in the circuit in series with it.
2. Rated response time. This is the time interval from the moment when the current leakage suddenly occurred and before it should be extinguished by all poles of the RCD. The maximum permissible value is 0.03 s.
3. Be sure to draw an RCD diagram on the case.

Leakage current shape

For this parameter, all residual current devices are classified into three types:

1. "A". Such a device is tripped with instantaneous or smoothly increasing current leaks, which have a sinusoidal variable or pulsating constant shape. This is the most common type of RCD. Due to the fact that it controls both alternating and direct current, it has a higher cost.
2. "AC". Also a common and more affordable device. Works only on the occurrence of alternating sinusoidal current leakage.
3. "V". This device is mainly used to protect industrial premises. In addition to a sinusoidal variable, the RCD responds to a rectified and pulsating form of constant current leakage.

A completely logical question arises, an alternating current of a sinusoidal form flows in household networks, can it be enough to install devices of the "AC" type everywhere? But if you take a closer look at the characteristics of modern household appliances, then most of them have power supplies with electronic semiconductor components, reaching which the sinusoid is converted into pulse half-periods. And if the leak is not sinusoidal, then the RCD of the "AC" type will not fix it and will not turn off.

That is why, in the passports for many household appliances, the manufacturer indicates through which RCD it is necessary to connect.

Tips for choosing an RCD in the video:

Operating principle

There are electronic and electromechanical RCDs.

The second is more expensive, but does not depend on the supply network. It will work as soon as a current leak occurs in the circuit.

An electronic device in its operation depends on an amplifier built into the electrical circuit. And for this amplifier to always be in working order, it needs an external power supply. In this regard, the reliability of the actuation is reduced.

Selectivity

According to the selectivity of operation, residual current devices are of two types - "G" and "S".

These RCDs are triggered after a certain period of time, called a delay. They are used when several devices are connected in series in a circuit. To protect the outgoing consumer branches, devices are installed without time delay, and at the input of RCDs of type "G" and "S". If a current leak occurs, and the outgoing RCD did not respond, then after a certain time the device at the input should turn off.

For "S" type RCDs, the shutter speed is adjusted in the range from 0.15 to 0.5 s, for type "G" - from 0.06 to 0.08 s.

Two-level fire protection

For a wooden private house, a guarantee of fire safety is especially important. Therefore, in this situation, it is necessary to select an RCD when planning a two-level differential protection system. Its main purpose is to separate the protective function:

• fire-fighting RCD provides operation in case of large current leaks, contributing to a fire;
• Ordinary devices will prevent electric shock to humans at low leak rates.

Since a fire-fighting RCD is of great importance for the rated leakage current, it alone will not provide protection to a person. Therefore, it is always installed in conjunction with an RCD, which has a lower leakage current.

Regardless of what value is the rated operating current and how many poles a fire-fighting RCD has, the leakage current parameter of such a device is 100 mA and 300 mA, otherwise it is no different from an ordinary one.

The connection diagram is performed sequentially, closer to the power source (at the input) we put a fire-prevention RCD, and universal ones on the outgoing branches of the protected wiring.

Clearly about the fire-prevention RCD in the video:

For example, it looks like this: the input RCD is selected with the parameters 63 A (rated operating current) and 300 mA (leakage current), the other devices, respectively, 40 A and 30 mA for the outlet group, 25 A and 10 mA for the bathroom, 16 A and 10 mA for the lighting group.

The use of fire-fighting devices is also advisable in the apartment. Often, the lighting group is left unprotected against leakage currents. With a minimum probability, but high current leakages can occur in this branch, and if such an RCD is installed at the input, it will be a kind of safety net.

Performing calculations

In practice, it is not always possible to accurately calculate the total leakage current. Therefore, approximately it is determined by the following method: for 1 A of the consumed load, 0.4 mA of current leakage is taken. You should also make a calculation based on the length of the phase wire - 10 μA is taken for 1 m.

Let's say you need to choose the right RCD according to the power of the electric stove (3 kW). To begin with, we calculate its load: 3000 W / 220 V = 13.64 A. Leakage current for the plate: 13.64 A x 0.4 mA = 5.46 mA. Similarly, we make a calculation for a laid conductor, for example, 10 m: 10 μA x 10 m = 100 μA = 0.1 mA. In total, the leakage current is 5.46 mA + 0.1 mA = 5.56 mA.

The resulting value of the sum of the current leakage should not exceed 33% of the differential rated current of the RCD. And then the calculation from school math lessons, we make up an elementary proportion and get: 5.56 mA x 100% / 33% = 16.85 mA.

There is a special table of standard values ​​of rated leakage currents, based on it, a 25 mA device is suitable for an electric stove.

You now know how to choose an RCD for an apartment or house, and you will be able to determine the total calculated leakage current yourself. If you have any doubts about your knowledge and abilities, invite a professional electrician to do the job. Remember that the residual current device is your guarantee of your safety.

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 separate section from the power supply by opening the contacts. Thus, fire protection and prevention is ensured. 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 are used not only in single-phase, but also in three-phase networks under various loads, therefore, their choice is carried out depending on the specific operating conditions.

Purpose of the RCD and the principle of operation

The main task of the RCD is to neutralize currents in the event of various damages in electrical installations. The residual current device is the most effective protective device. Unlike fuses or circuit breakers, RCDs are able to break a circuit in a split second and save human life.

The danger is not only the likelihood of direct electric shock. Sometimes it is enough to simply touch the parts of devices and devices that are energized. Therefore, protective devices must be triggered in a timely manner. In order to correctly solve the problem of how to choose an RCD for a house, the conditions in which it will function must be taken into account.

In the work of protective devices, the phenomenon of electromagnetism is used. 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 are positive, and the outgoing ones are negative. In the absence of leaks and short circuits, they will be equal and add up to zero. This state of the circuit indicates the health of the installed equipment.

In the event of a leak, there is a partial reverse current flow through the grounding conductors, resulting in an imbalance. The difference in differential currents causes a magnetic flux to be excited 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 cuts off the power supply to consumers.

How to choose the right RCD

In order to choose the best option for a 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 the leakage currents allows them to be divided into different types. This division depends on a smooth or sudden rise in current. RCDs with such characteristics are most widely used as the most suitable for the widest operating conditions.

The triggering technology allows you to divide the RCD into electromechanical and electronic. In the first case, high-precision mechanisms are triggered as a result of the action of leakage currents. These are the most reliable and expensive devices that can work under any conditions. Electronic devices are cheaper, however, for normal operation of the electronics, an external power supply is required. Their effectiveness is significantly reduced when voltage surges occur. The response speed of RCDs allows them to be used in multi-level protection systems. This allows all emergency sections to be disconnected separately.

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 for 380 V. The first option is usually used in apartments, and the second - in private houses, summer cottages 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. It is also the throughput current of the RCD, which depends on the number and power of the 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. RCD ratings set by manufacturers are 16, 20, 25, 32, 40, 63, 80, 100 A.
• RCD leakage current. The value at which it turns off. It also differs in ratings of 10, 30, 100, 300 and 500 mA. For ordinary apartments, a 30 mA device is best suited. At a lower current rating, the device will constantly respond to even minor fluctuations in the network and turn off the power.
• Leakage current type. The symbols АС, А, В, S and G are marked on the body of the device. For example, АС responds only to alternating leakage current, and В - to direct and alternating currents. The rest of the marking also corresponds to certain parameters, including the shutdown time delay of the device.

What are the RCDs

The main classification of residual current devices is based on the current of their operation. For example, devices respond to currents of 100, 300 and 500 mA. They protect the wiring from fire in case of insulation failure and short circuit. Typically, an introductory RCD is installed behind the electricity meter and provides protection for the entire facility. For humans, 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 disconnect the network when the current reaches a value of 10 or 30 mA.

The protective devices differ in the number of poles and can be used in single- or three-phase networks. Each type of device differs in the way it functions. The markings applied to the body of the device must be correctly deciphered and exactly what it means:

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

RCDs are classified according to their technical design. This allows you to better select the RCD. Most often, electromechanical devices are used that do not have their own power source. They pick up and trip when a differential current appears.

Another type refers to electronic safety devices that require an external power supply. In this regard, the reliability of protection is reduced, therefore, such RCDs are used less often. When the auxiliary power is turned off, they turn off the network automatically, when the power is restored, the network also turns on automatically. Some instrument designs do not automatically turn on the circuit when power is restored.

How to choose an RCD by power

Unlike circuit breakers that protect against overloads and short circuits, residual current circuit breakers are designed to protect against current leaks. The reason is faulty insulation of electrical appliances or contact of live parts with the body. In these cases, an instantaneous disconnection of the RCD occurs, the line is de-energized, and consumers are protected from electric shock.

In order to calculate the power RCD, it is necessary to know the total number of consumers connected to this line. In the event that the question of how to choose an RCD and an automatic machine for power is being decided, both protective devices must have appropriate values ​​that ensure their normal operation. 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 of a multi-storey building does not exceed 25A.

When installing an RCD in private houses, it is recommended to divide all consumers into groups that are connected to separate lines extended to each floor, outbuildings, outdoor 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 not actually function normally and will not be able to protect the line. Partially solving this problem will help, designed for a current consumption of 5A.

How to calculate an RCD

In order to calculate the protective device and solve the problem of how to choose an RCD in terms of power, the parameter table 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 get the desired result. The calculations use a mains voltage of 220 V, with a frequency of 50 Hz.

The calculation and selection of the RCD rating for the maximum current is quite simple. It is necessary to set the value of the total electrical power of devices and equipment switched on simultaneously. For example, if this indicator is 6000 watts, then the value of the calculated current will be: 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 for the leakage current, in this case, a simplified scheme is used, according to which various types of protective devices are selected in accordance with the operating conditions of the facilities:

• In ordinary living quarters - at 30mA.
• In bathrooms, kitchens and other rooms with high humidity and higher electrical safety requirements - by 10mA.
• At large facilities with electrical grids over 1000 m long or at the input - 100mA.

Quite often, it becomes necessary 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 consumption current. The correct calculation of RCDs and machines shows that in the event of overloads and short circuits, the machine 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 value of the current that the device can pass through itself without time limits. Within this line, the choice of RCDs is made for the electrical panel of an apartment or a private house.

The value of the rated current is necessary when deciding how to calculate the RCD for a group of machines. In this case, for protection, you need to choose an automatic device 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 a current through itself that is more than the rated one for a long time. If the currents are equal, during this period the RCD may simply burn out.

What kind of RCD to put at the entrance to the apartment

In modern high-rise buildings, it is forbidden 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 a two-pole device labeled AC is used for single-phase wiring. The leakage current of the RCD for the apartment is selected at the rate of 30 mA. Devices with a lower shutdown threshold can cause false alarms.

How many RCDs should be installed in the apartment? It all depends on the total power of consumers. If it is too large, it is recommended to split the home network into separate lines and put a protective device on each of them. Additionally, a general RCD is installed at the entrance to the apartment to protect against fire in case of damage to the insulation.

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

RCD at the entrance to the house

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

In addition, the choice of an RCD for a private house is carried out according to the type of current. However, it should be borne in mind that in private houses, powerful electric motors are often started, consuming a powerful starting current for a short time. It is recommended to determine in advance which RCD and then select the necessary device that remains operational 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 leakage currents. 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 fluctuations and cause false alarms.

If your apartment or house has a large number of household appliances, then it is advisable to take care of additional protection. This is due to the norms and possible damage during the operation of the conductor insulation. After all, if a damaged wire gets on the body of the device, you touch it, then this can have serious consequences. A circuit breaker installed in the electrical panel of an apartment or house protects the circuit only from short circuit and high current. To protect against leakage current, it works in tandem with it. As an alternative to a protective shutdown, it is possible to use difavtomats (differential protection circuit breakers), in the case of which both fuses are located, but this is a separate topic. In this review, we will "focus" on how to properly connect RCDs and machines in an apartment or a private house. In this case, we will consider the electrical parameters of the wiring and the total amperage of household appliances, the main schemes, supplemented by video reviews.

This topic is very relevant and difficult for unprepared readers to understand. Therefore, we will try to sort out all the useful information on the shelves, concretize and build a kind of logical chain.

When electrifying an apartment or a private house, three stages can be roughly distinguished:

• Electricity supply to the switchboard.
• Installation and equipment of the electrical panel.
• Final wiring from the shield.

All these stages are interconnected. After all, without knowing the specific final parameters, it will be impossible to complete the electrical panel and select the required protection device. Therefore, before studying how to properly connect RCDs and machines, consider a specific example of a house or apartment.

Selection of automatic fuses

Let's take the layout of a private house as a starting point. In apartments, especially recently built ones, the issue of connecting residual current devices is not so acute, and everything in the switchboard is completed according to the project. And with a private house, things are a little different - the project and layout falls on our shoulders (with the involvement of specialists).

For clarity, consider the following layout of a private house(program used):

Having considered the project of the house, one can single out such premises as:

• Living room (1st floor).
• Room (1st floor).
• Kitchen (1st floor).
• Corridor (1st floor).
• Bathroom (1st floor).
• Three rooms (2nd floor).
• Bathroom (2nd floor).

Based on this, we will form certain groups of consumers:

Sockets 1st floor:

1. Living room
2. Room- circuit breaker C 16, wire cross-section (copper) 3 × 2.5 mm², approximate power consumption 1600 W.
3. Corridor + bathroom- circuit breaker C 16, wire cross-section (copper) 3 × 2.5 mm², approximate power consumption 1600 W.
4. Kitchen

You can combine the sockets of the living room, room and corridor into one group. In this case, we use an automatic machine C 25, wire cross-section (copper) 3 × 2.5 mm². Estimated power consumption 4800 W.

Switches 1st floor:

1. Living room.
2. Room.
3. The corridor.
4. Kitchen.
5. Bathroom.
6. Outdoor Lighting.

You can combine the switches of the living room, room, corridor, kitchen and local area into one group. In this case, we use an automatic machine B 10, wire cross-section (copper) 3 × 1.5 mm². Estimated power consumption 1600 W.

Sockets 2nd floor:

1. Room 1- circuit breaker C 16, wire cross-section (copper) 3 × 2.5 mm², approximate power consumption 1600 W.
2. Room 2- circuit breaker C 16, wire cross-section (copper) 3 × 2.5 mm², approximate power consumption 1600 W.
3. Room 3- circuit breaker C 16, wire cross-section (copper) 3 × 2.5 mm², approximate power consumption 1600 W.
4. Bathroom + washing machine- circuit breaker C 16, wire cross-section (copper) 3 × 2.5 mm², approximate power consumption 3000 W.

It is possible to combine the outlets of rooms 1, 2 and 3 into one group. In this case, we use an automatic machine C 25, wire cross-section (copper) 3 × 2.5 mm². Estimated power consumption 4800 W.

Switches 2nd floor:

1. Room 1.
2. Room 2.
3. Room 3.
4. Bathroom.

You can combine the switches of room 1, 2, 3 and bathroom into one group. In this case, we use an automatic machine B 10, wire cross-section (copper) 3 × 1.5 mm². Estimated power consumption 800 watts.

So, at this stage, we have decided on consumer groups, circuit breakers and power cable section. Let's display the resulting data in the form of a table:

Table 1. Selection of automatic devices (automatic fuses) for consumer groups:

GROUPS	AUTOMATIC TYPE	WIRE TYPE
Sockets 1st floor	C25 1P	VVG 3 × 2.5 mm²
Sockets kitchen 1st floor	C16 1P	VVG 3 × 2.5 mm²
Sockets 2nd floor	C25 1P	VVG 3 × 2.5 mm²
Sockets bathroom 2nd floor	C16 1P	VVG 3 × 2.5 mm²
Lighting 1st floor	B10 1P	VVG 3 × 1.5 mm²
Lighting 2nd floor	B10 1P	VVG 3 × 1.5 mm²
	The circuit breaker is a single pole 10 amp automatic fuse. It protects the phase conductor connected to the machine of a single-phase two-wire or single-phase three-wire electrical wiring from melting of the insulation and conductive core of the wire due to overheating from short-circuit currents and prolonged heating by a current exceeding 10 A. load up to 2.2 kW in the event of an emergency, by disconnecting the voltage supply. The characteristic curve dictates the use of the B10 circuit breaker to protect lines with inrush currents (inrush currents) up to 30 - 50 amperes.
	The circuit breaker is a single pole 10 amp automatic fuse. It protects the phase conductor of a single-phase two-wire or single-phase three-wire electrical wiring connected to the machine from melting of the insulation and conductive core of the wire due to overheating from short-circuit currents and prolonged heating by a current exceeding 16 A. load up to 3.52 kW in the event of an emergency, by disconnecting the voltage supply. The characteristic curve determines the use of the C 16 circuit breaker to protect lines with inrush currents (inrush currents) up to 80 - 160 amperes.
	The circuit breaker is a single pole 10 amp automatic fuse. It protects the phase conductor of a single-phase two-wire or single-phase three-wire electrical wiring connected to the machine from melting of the insulation and conductive core of the wire due to overheating from short-circuit currents and prolonged heating by a current exceeding 25 A. load up to 5.5 kW in the event of an emergency, by disconnecting the voltage supply. The characteristic curve necessitates the use of the C 25 circuit breaker for the protection of lines with inrush currents (inrush currents) up to 125 - 250 amperes.
	- type of copper power cable VVG, the insulated conductors of which are located parallel in one plane. This power cable has a sheath and the very insulation made of polyvinyl chloride plastic (PVC), which ensures flame retardancy with a single laying. The cable is suitable for use in dry, damp locations and outdoors, but not recommended for buried applications. Withstands low (up to -50 ° C) and high (up to + 50 ° C) temperatures well. Resistant to humidity up to 98% and various chemicals. Power cables VVG-P have different cross-sectional areas of conductive conductors, which depends on the object of use. Copper cable with cross-sectional area 1.5 mm² designed for a current of 19 A and a power of 4100 W, and with a conductor cross-sectional area 2.5 mm²- for a current of 27 A and a power of 5900 W.

How to choose an RCD. Calculation for the considered example

In the previous paragraph, we examined which automatic fuses are needed for a particular house. Now, based on these data, using the calculation, we will determine the necessary OUZO machines for this configuration. For clarity and convenience, we will choose a residual current device according to the groups formed in the table above. But first, let's decide on the recommendations and already known methods of selection and calculation:

1. In order to ensure the best electrical safety and, at the same time, the maximum uninterrupted power supply, it is advisable to install a separate automatic device for each group of consumers. For these purposes, devices with a value of the magnitude of the leakage current (setting) are used 10 mA and 30 mA, at which the protection is triggered.
2. For wet groups made with a separate line, an RCD with a setting of 10 mA is installed. In our example, we refer to the wet groups as the bathroom on the second floor, in which the washing machine will be located.
3. Residual current device rated current is selected equal to or one step higher than the rated current of the circuit breaker that protects this section of the circuit.

Based on the first and second points, we can determine the following: in all groups, except for the "socket, bathroom on the 2nd floor," we install devices with a setting of 30 mA, and in the wet group of the bathroom on the second floor - 10 mA.

How to choose ouzo

Based on the third point, it is possible to preliminarily determine the rating of the residual current device for a specific circuit breaker of a group of consumers.

Table 2. Selection of RCDs for consumer groups:

You can supplement the answer to the question of how to choose ouzo for an apartment or house by checking the types of devices we have previously selected by truncation. They must perform protective functions in accordance with standards. To do this, it is necessary to calculate the leakage current of the electrical installation IΔ:

• IΔ = IΔep + IΔnets, where IΔep- electric receiver leakage current, mA; I∆nets- network leakage current, mA.

When calculating the leakage current in the electrical installation PUE, it is prescribed to take the leakage current of electrical receivers at the rate of 0.4 mA per 1 A of the load current, and the leakage current of the circuit at the rate of 10 μA per 1 m of the length of the phase conductor. Respectively:

• I∆ep = 0.4 X Icalculated, where Icalculation- rated current in the circuit load, A.
• Icalc = Inom = Pnom / (Unom X cosφnom).

Power factor cos φ characterizes the amount of reactive energy consumed by the device. Most household and office equipment has an active load (they have little or no reactance), for them cos φ = 1.

Rated power Pnom(W) in our case we take from consumption groups, where each was given an approximate consumption power. To make it clearer, let's take the group "sockets on the 1st floor". It includes a living room, a room, a corridor and a bathroom. We have set the approximate power consumption for individual rooms to 1600 W. In total for the group, this indicator will be 4800 Wt.

Rated voltage for single-phase network Unom = 220 V.

• I∆network = 0.01 X Lwires, where Lwires- the length of the phase conductor, m.

According to the requirements of the PUE, the total leakage current of the network, taking into account the connected stationary and portable electrical receivers in normal operation, should not exceed 1/3 of the rated breaking differential current IΔn RCD. That is, the rated differential breaking current of the device (which is printed on the case) must be at least three times the total leakage current of the protected circuit of the electrical installation. IΔ:

• I∆n> = 3 I∆.

An example of calculating the conformity of a device in a consumer group

Consider a group "Sockets on the 1st floor":

• I∆n = 30 mA(from table 2).
• Unom = 220 V.
• Pnom = 4800 W.
• Lwires- in this case, it is unknown, and we will determine its optimal length.

By condition I∆n> = 3 I∆, I∆<= 30/3 <= 10 мА.

Icalc = 4800/220 = 21.81 A.

I∆ep = 0.4 X 21.81 = 8.73 A.

According to the basic formula I∆ = I∆ep + I∆networks:

10 = 8.73 + (0.01 X L wire);

(10-8.73) / 0.01 = L wire;

Lwire = 127 meters.

Conclusion: installed on the considered group RCD 25 A 30 mA paired with a gun C25 1P acceptable given that the length of the phase conductor does not exceed 127 meters. Naturally, at the design and installation stage, you will know the length of the wire used in each specific group. And to check compliance, the formula is calculated IΔ. The resulting current is multiplied by three and compared with the marking of the used residual current device. The condition must be met I∆n> = 3 I∆.

Let's say Lwires in a group = 250 meters; then, based on the previous calculation, I∆ = 8.73 + (0.01 X 250) = 11.23 mA; 3 I∆ = 33.69> I∆n. The condition was not met. As a way out, you can divide the group into two.

Connecting RCDs and machines in the electrical panel - basic diagrams

We looked at an example of a certain house or apartment and identified groups of electricity consumers, selected automation for them, and reviewed the methodology for calculating compliance with requirements. Let us supplement the above with a visual example and a diagram of how to correctly connect an RCD and automatic machines. Let's complete the electrical panel:

Connection diagram for RCDs and machines

Considering this scheme, several questions may arise:

• Installation of an introductory machine.
• Installation of fire protection ouzo.
• Optimization of the number of residual current devices.

Let's start with the last point. Naturally, the condition to use a separate RCD for each group of electricity consumers is justified. However, there is always an alternative and you can refuse something in this scheme. For example, you can:

• Remove the fire protection device.
• Do not use an RCD for lighting the first and second floors.
• Install one common protection device on the sockets of the first and second floors. In this case, the rated current of the group RCD is selected so that it is equal to or greater than the sum of the ratings of the group circuit breakers. If the sum of the ratings of the group circuit breakers exceeds the rating of the input circuit breaker, then the rated current of the residual current device is selected equal to the rated current of the input RCD, and if the input fire-fighting device is not installed, then it is equal to or greater than the rating of the input circuit breaker.

In any case, these are just options that need to be calculated and analyzed. We will devote a separate review to the options and schemes for connecting the RCD. And now, to complete the topic, we will briefly consider the installation of an introductory machine and a fire extinguishing device.

Introductory machine- This is a circuit breaker for supplying electricity from the mains to the object if an overload occurs in the circuit, or a short circuit occurs. It differs from conventional circuit breakers used in the circuit in a larger value of the rated current. With a small number of loads, it can be single-pole and connected through a phase wire. In our example, a bipolar sample was used. A two-pole circuit breaker is a unit with two poles. They are equipped with a combined lever and have a common interlock between the shut-off mechanisms. This design feature is important, since PUE prohibits breaking the neutral wire.

They can be installed in switchboards fireproof UZO... They differ from conventional devices by a higher leakage current setting - 100 mA or 300 mA. In order to achieve selectivity, it is advisable to use devices with the letter S on the front panel. If you install the usual non-selective one, then when one of the group RCDs is triggered, the fire protection will almost always work.

As a supplement - video: RCD connection diagrams

The topic considered is quite extensive, and we tried to figure out how to correctly connect RCDs and machines in an apartment (house) according to a given scheme and layout. The choice of one or another protective device must be justified by calculations and comply with the standards. For a better understanding, it is recommended to study additional materials on this issue.

In this article, we will consider the purpose and principle of operation of an RCD. We will figure out how devices of different types differ, we will determine in what conditions they are used. Let's talk separately about connecting these protective devices.

An RCD is a switching (switching off) device that, when the differential current (leakage current) reaches and exceeds the set value, opens the contacts and disconnects the network or its section from the power supply. This product has several names: "residual current circuit breaker", "residual current circuit breaker", "protective circuit breaker". One way or another, but hundreds of millions of RCDs used in the world perform two tasks - they protect a person from electric shock during direct and indirect contact and prevent a fire from igniting wiring. In many developed countries, the use of differential switches is mandatory.

Residual current devices are designed to neutralize currents in case of all kinds of damage to electrical installations. Despite the fact that this is only a part of complex measures, in some cases the RCD remains the only means of protection, for example, when: lowering the insulation level, breaking the neutral protective conductor or at low values ​​of the fault current. So the fuses (circuit breakers) break the circuit at current values ​​(short circuits or overcurrents) that are several times higher than the critical threshold for a person, at which a malfunction of the heart muscle occurs, while RCDs are triggered in milliseconds and react even to the smallest current.

It can be fatally dangerous to touch live elements in an electrical panel or cases of electrical appliances that are energized, for example, if the insulation is damaged, there is always a risk of damaging the sheaths of the hidden wiring cables with a tool. A current of 5 mA is already felt by a person, at 10 mA, the muscles contract, and the threshold of "not letting go" sets in, 30 mA causes respiratory failure, 50 mA causes cardiac arrhythmias, 100 mA is a lethal outcome. That is why, according to US standards, an RCD designed to protect people should operate at currents of 4-5 mA, in Europe - 10 mA. In Russia, there are no strict standards - residual current devices, according to state requirements, must be used in metal structures or buildings with a metal frame. However, after the publication of the seventh edition of the PUE, the attitude towards RCDs in our country changed dramatically for the better.

It should be noted that the residual current device cannot replace circuit breakers that protect the wiring, since it "does not notice" malfunctions that are not accompanied by leakage currents, for example, in the event of a short circuit between the line and neutral.

The principle of operation of the RCD

The operation of any RCD is based on monitoring the balance of currents between the conductors that it includes. Possible current differences are detected and compared with the setpoint values. An imbalance is an indication for the actuation of the executive part (circuit breaker).

The main "tracking" unit of the RCD is a differential transformer with three windings of the ferromagnetic core: inlet, outlet, and control. The current flowing through the device (from the phase conductor going to the consumer's power supply to the neutral conductor coming from the consumer) excites magnetic fluxes with opposite poles on the windings. If household appliances, wiring accessories are in good working order, the wiring in the protected area is not damaged, and there are no leaks to the ground, then the sum of the currents is zero. If, for example, a person standing on a wet floor touches a bare wire, then part of the current will go through his body to the ground, the sum of the flows in the device will be greater than zero (the current flows into the RCD more than it leaves). The appearance of a positive sum of currents means that the current also passes by the RCD, that is, there is a leakage, damage in the circuit. In this case, the balance in the control winding of the transformer is disturbed, a force arises that is transmitted to the EMF relay, breaking the contact between the line and neutral. The electromotive force can be detected by the tracker, which becomes a signal to turn off the solenoid (power actuator) holding the contacts - the circuit is opened.

RCD types

Residual current devices (RCDs) can differ in many characteristics, from the way they are installed to their general purpose. The classification includes hundreds of types of RCDs with their own characteristics. We propose to consider the main ones in order to choose the right device that will function correctly in certain conditions.

By the nature of the leakage current

According to this criterion, RCDs are divided into devices of the AC, A and B types. AC devices break the circuit in case of AC leaks if they grow suddenly or smoothly. These RCDs are inexpensive, they are most widely used, and are considered acceptable for most operating conditions.

RCDs of type A are triggered not only from alternating current, but also from pulsating direct current, which suddenly increases or rises smoothly. Such devices are more preferable for residential premises, since some household appliances are precisely the source of a constant pulsating current, for example, computers, dimmers, televisions, some washing machines (all with semiconductor power supplies). By the way, the instructions for some of these consumers indicate that they must be connected only through an RCD of type A. These protective devices are significantly more expensive than the AC class.

Type B is used for direct, alternating and rectified current, mainly such RCDs are used in industrial facilities.

By triggering technology

Depending on the principle on which the circuit is broken, an RCD is distinguished:

• electronic
• electromechanical

Electromechanical differential protection devices do not need a full power supply from the mains. They are only triggered by a leakage current, which drives a high-precision mechanical actuator. These devices are relatively expensive, few manufacturers produce them, but they are considered the most reliable, since they work under all conditions and are not dependent on power parameters.

Electronic RCDs are several times cheaper than electromechanical ones, so they make up the lion's share of our market. For the functioning of these devices, external power is needed, which "revives" its electronics with an amplifier. The main problem is that with voltage drops in the network, the efficiency of the electronic RCD (there is a dependence of the trigger moment) is noticeably reduced. In addition, there is always a danger that direct or indirect contact with an energized element (wire, terminal or device case) will occur when the neutral conductor is damaged and, accordingly, the RCD will not be energized - and will not work. Electronic RCDs do not protect from all risks, but from most, so if you need to save money, then this is also a good option. It also makes sense not to spend money on an electromechanical device if the in-house network includes an uninterruptible power supply or voltage stabilizer.

By response speed (delay)

Letter S denotes RCDs, which operate with a set delay of up to 0.5 seconds - "selective". This type of device allows you to create multi-level "cascade" protection systems with several protected circuits. Each emergency section of the network, depending on the tasks set and the implementation of the scheme, will be disconnected separately, while the general power supply to the room will remain. RCDs with index G also have a delay, but it is much less.

1 - lead-in cable; 2 - introductory machine; 3 - counter; 4 - RCD type S; 5 - machines; 6 - zero bus; 7 and 8 - RCD type AC; 9 - three-core electrical wiring; 10 - grounding bus

Selective RCDs are usually installed at the top of the cascade, therefore, in the event of leaks, non-selective devices are triggered first, without de-energizing all the circuits that are protected.

High quality modern non-selective RCDs operate in less than 0.1 seconds.

By the number of poles

For a three-phase network, RCDs with four poles are used. They protect several single-phase networks, or separate three-phase consumers (electric motor, hob ...). In tandem with this type of RCD, a four-pole automatic device should work.

For a single-phase network of residential premises, devices with two poles (line and neutral) are usually used.

Leakage current

The leakage current (rated residual current or "setpoint") under specified operating conditions is one of the main parameters characterizing the functional features of the residual current device. The boundary barrier for classification is a current of 30 mA. RCDs that operate at lower creepage points are considered to protect a person from electric shock. Devices, the operating current of which is higher than 30 mA, are considered fire-fighting, since a rather large load can be connected to them, but the differential currents that they allow are dangerous to humans. Sometimes 30 mA RCDs are considered universal, they are most common.

Fireproof RCDs are the first stage of protection located in the switchboard, they are usually installed on the entire internal network, but they can also be used to protect individual heavy-duty and dangerous consumers from ignition (for example, a fan heater with an open spiral). The leakage current of fire-fighting RCDs is usually taken at 100-300 mA, sometimes 500 mA devices are also used as fire-fighting devices. RCDs with a lower current cannot work normally in these positions, since false alarms occur due to exceeding the permissible loads.

RCDs with a leakage current of 10 mA are usually used in the second or third stage of protection, they are used either to connect lighting elements, or for individual electrical appliances that are located in hazardous areas, for example, in a bathroom, shower, swimming pool ... However, a boiler or washing machine powering through them, most likely, will not succeed, since the workload will be limited to 1.8 kilowatts.

Note that the current rating shows only the lower trip limit, so a 30 mA RCD will not disconnect the circuit with a leakage of 25 mA, but will trip at any currents exceeding the 30 mA threshold.

With what leakage current is it necessary to apply an RCD in a particular case? First, the leakage current of the circuit or device is determined, this can be done by measurement or according to the current regulations. According to SP 31-110-2003, the leakage current of the device is taken equal to 0.4 mA for each 1 A of its power. This also adds 10 μA for each meter of phase conductor. For example, for an electrical appliance with a power of 16 A, powered by a twenty-meter wire, the expected leakage current should be taken equal to 4.2 mA. Now you can pick up an RCD, but this is done so that the leakage current of the device is no more than 33% of the operating current of the residual current device. In our case, this is 12.6 mA. A 10-ampere device is no longer suitable, which means it is necessary to supply an RCD with a trigger current of 16 mA.

Operating current

The operating current of the RCD (or the maximum permissible load) determines how much and what power consumers can be powered through this device. This characteristic shows the current that can pass through the RCD for a long time without destroying it.

The calculation of the required RCD is made from the characteristics of the consumers connected to it. In the electrical networks of residential premises, low-power RCDs with an operating current of 10 A are often used. Differential protection devices with a permissible load of 16-32 A are considered medium-power. Devices for 40 A and more are called powerful.

It is noteworthy that in practice there is a clear relationship between the shutdown current and the operating current. Manufacturers produce RCDs, in which the higher one indicator, the higher the other.

If possible, the regulation of the rated leakage current of the RCDs are:

• unregulated
• adjustable (continuous adjustment, step adjustment)

By the presence of short-circuit protection, there is an RCD:

• with overcurrent protection (differential circuit breakers)
• with overheating protection
• without overcurrent protection

According to the method of installation, the RCD is divided into:

• stationary in the form of an automatic machine, which are mounted on a rail in a mounting panel;
• portable - mounted on an extension cord or in a break in the supply cord;
• RCD in the socket (widely used in the USA).

Installation and connection of RCD

In the household network, two-pole RCDs are usually used, which occupy two places (36 mm) on the DIN rail. They are usually located near the lines of the protected circuits, with the exception of fire-fighting devices with a shutdown current of 100-500 A, which are installed near the input machine. RCDs can also be located in group ASUs of apartment buildings, and floor panels of a private house.

If the wiring is divided into groups, it is recommended to install one RCD at the input and several devices in different groups, while ensuring their selectivity - cascade disconnection. To do this, an RCD with a lower tripping current rating or a higher tripping speed is installed on each next tier below.

An RCD is connected in accordance with a pre-developed leakage current protection scheme. The protection system is designed depending on the functions performed by the device and the specific characteristics of the network. Below is a simple diagram for connecting an RCD to an electrical installation with grounding, it can be used to protect individual circuits in multi-tiered cascade systems:

1 - lead-in cable; 2 - introductory machine; 3 - counter; 4 - RCD; 5 - machines; 6 - zero bus; 7 - three-core electrical wiring; 8 - grounding bus; 9 - ground wire

As you can see, there is nothing complicated, let's draw your attention to some points:

1. For the correct operation of the RCD, in the protected circuits there should be no contact of the working neutral conductor with grounded elements or the protective PE conductor. For each of them, its own bus is used in the shield (GOST R 50571.3-94).
2. The grounding conductor "does not participate" in the connection of the RCD.
3. The power supply for the RCD is connected to the upper terminals. The connectors for the phase input on the RCD are usually designated "1", for the output - "2".
4. The neutral of the power supply (zero, wire with blue insulation) must be connected to the connector marked "N". This rule must be observed for RCDs of any brand, rating and purpose.
5. The most important point! The rated operating current of the RCD must be the same or greater than the operating current of the circuit breakers. Only then will the machines be able to protect expensive RCDs from overload.
6. The installed RCD must be checked for operability.

Checking the RCD

After switching all circuits, the intra-house network must be powered. If the circuit breakers or RCDs have not tripped, then there is no short circuit, and the neutral conductor is not in contact with ground.

Next, press the "TEST" or "T" button located on the front panel of the device. Thus, we forcibly simulate the occurrence of a leakage current. A serviceable RCD should instantly work and de-energize the protected area. If this does not happen, then in the event of an emergency, the device will not help to cope with the problem.

The last stage of the check can be considered the supply of a load to the RCD. It is necessary to turn on one by one all the devices that will work in a particular circuit and the network as a whole. In case of possible malfunctions, it is necessary to make changes to the protection circuit or change the ratings of the residual current devices.

RCDs are not the only way to protect a person from electric shock and network overloads, which can lead to a fire. But often it is these devices that save lives and ensure the safety of citizens' property.

Turishchev Anton, rmnt.ru

The modern power grid includes an RCD. What kind of RCD are installed at the entrance to the apartment? What are the 2 parameters that determine the choice? How many devices are enough?

TEST:

1. What electrical appliance do we protect against leakage current?

A) Air conditioner, capacity 1950 W

B) Boiler with a power of 4200 W

1. For what current should you choose a differential relay?

1. What room is the consumer installed in?

A) Bedroom

1. Trip current value?

Answer options.

1. For the air conditioner, we choose an RCD with a current of 3 A (2 is enough for the machine, we choose one step higher) for placement in the Bedroom and an allowable leakage of 10 mA.
2. In front of the boiler, we install a 6 A differential relay (3 for the machine). Installation - in the Kitchen with a differential current of 6 mA.
3. The air conditioner can be protected by a 6 A differential relay (2 A for a circuit breaker) when installed in a Bedroom and a leakage value of 10 mA.

We choose an RCD according to 2 main parameters.

Residual current device is a device that protects people and property from two dangers - fire and electric shock.

There are two types of residual current devices- differential automatic or differential relay. Both of these devices are very similar and interchangeable. In the future, we will consider a differential relay (together with an automatic device) as a protective device as the most economical and flexible option.

What are the parameters for choosing the right RCD? Differential protection devices differ in operating current and leakage current (or differential current).

A joint circuit breaker is required for complete leakage protection.

The first parameter of the protection differential is the operating current.

The nominal range of the differential relay has the same range as that of the circuit breakers ( automata) – the first column in Table 1. The current is selected according to the load power and for a single-phase network is indicated in second column of the table. Dif relays are the most expensive devices in the electrical network and therefore the value for the machine is chosen lesser.

TABLE 1. Selection of power rating.

2 more nuances about the choice of the operating current of the machine and the RCD.

Fig. 1. The class of a two-pole machine on the front side (in a red oval).

1. The machines have an additional class marking in the form of a Latin letter (Figure 1). It means how quickly the machine will open the load circuit when the consumption is exceeded. When overloaded, passes through the machine many electricity. Excessive current leads to failure of the diffrell, despite the fact that the machine operates indefinitely with a slight overload.
2. The wiring is rated for the current consumption of the load (Table 2).

Example 1: How to choose an RCD by power for a water heater ( boiler) with a capacity of 2 kW? The cross section of the veins must be 1.5 sq.mm... We select the machine according to table 1 from the standard series in the larger direction - 2 A... The differential of the relay must have a rated value of the operating current in 3 A.

How to choose 380V? The rating of the machine can be simply calculated as two times greater than the load power. For our water heater - 2kW x 2 = 4 A.

Conductor cross-section, mm2	Current, A	power, kWt
1,5	19	4,1
2,5	27	5,9
4	38	8,3
6	46	10,1
10	70	15,4
16	85	18,7
25	115	25,3
35	135	29,7
50	175	38,5
70	215	47,3
95	260	57,2
120	300	66,0

TABLE 2. Maximum current and power at cable cross-section.

1. What if the consumption of multiple loads is very high? It is required to supplement 3 loads with a consumption of 16A each with a differential relay. The obvious way is to choose a nominal 50 A ( rounding up from 3x16 = 48 A). Such differential relays are found, but more often of Chinese production and with poor quality. For a number of European firms, the maximum range is limited to 25-30A. Each load must be protected with a separate protective device.

The second parameter is the trip current.

The tripping current is selected from the range in Table 3. Electric receivers and wiring, due to imperfect insulation or internal device, contain their own, natural leak. Before installing a protective shutdown, it is advisable to measure it by a competent power supply organization. The leakage current can be calculated based on a natural leakage of 0.4 mA per 1 A consumption for the load and 10 μA ( 0.01 mA) for 1 meter of wiring. According to the rules ( PUE) the nominal value must not be less than three times the natural value.

We continue with example 1. Let's take a consumption current equal to the value of the machine (in practice, the value is indicated in the device passport) - 2A, the wiring will be 20 m long. Based on these data:

Iest = 2x0.4 + 20 * 0.01 = 0.8 + 0.2 = 1 mA. We select a differential protection with a minimum value of 6 mA.

We analyze typical schemes. Example 1. What kind of RCD should be installed in an apartment?

Rice. 2. Typical apartment wiring. The ground and zero line is conventionally not shown

On Fig. 2 after the counter, a differential protection is installed as fire protection. Lighting in each room is output to a separate machine. Dif relays are installed for the most "demanding" rooms - a children's room, living quarters and a bathroom ( SNIP 31-110-2003 clause 14.40). The kitchen electric stove is separated only by an automatic machine. This was chosen with the expectation that there are no moving parts in the electric stove and the risk of damage to the insulation in it is minimal. The lighting is also not protected ( recommendations of PUE 7.1.79), because current leaks for lamps are insignificant and do not pose a danger, and, if necessary, are easily localized.

Calculation of an RCD for an apartment. 1st differential relay.

Let's make a calculation for the first circuit serving for consumers connected through sockets. We will assume that the following electrical appliances are working at the same time:

Refrigerator, with a power of 3500 W with a cable length of 15m

Air conditioner, 3450 W, length 10m

Living room sockets 2400 W, 20m

Children's sockets 1500 W, 15m

Other sockets 2500 W, 25m.

We choose the values ​​of the machines. From table 1 it follows that for the refrigerator and air conditioner, you need to choose machines for 6 A, for a nursery - 2A, for others - 3A. The class of machines - C, as the most common in household electrical wiring. Let's calculate the natural leakage for consumers - ( 6 + 2 + 3x2) x 0.4 = 14 x 0.4 = 5.6 mA. The operating current is selected from Table 1 by a value greater than the total load - 16A.

The total length of all wiring lines is 15 + 10 + 20 +15 + 25 = 85 meters, which corresponds to a current in 85 * 0.01 = 0.9 mA (round up).

The total leakage is 6.4 mA. We select an RCD three times larger by 30 mA.

2nd diffrele in the apartment.

Calculation for second the protection circuit is quite simple. Let's take into account that the washing machine has a power of no more than 2 kW. The leakage current will not exceed 1-2mA ( taking into account the length of the wiring) and the room has a humid climate, passing sewer pipes, etc. For this case, the trip value has the smallest rating - 6 mA.

Possible improvements for the apartment's electrical system.

The considered scheme has disadvantages. The first circuit of the protective shutdown has a large number of loads. A leak in one will de-energize all devices. The most powerful consumers (refrigerator, air conditioner and others) can be connected through portable protective devices. Such devices are plugged into a socket (Fig. 3).

Rice. 3. "Mobile" RCD.

Example 2. Safety shutdown for a garage.

The garage is characterized by the presence of a line of lighting and sockets. Electrical tools with a consumption of no higher than 16A are connected to the sockets. The differential of the relay in this case has a rating of 25A ( Rice. 4).

Rice. 4. A protective shutdown in the garage is installed on the sockets (according to the recommendation of PUE 7.1.71). A common entrance machine protects all garage wiring. Automatic devices (AB) for lighting - separate (zero is not additionally protected - Appendix to SNIP 31-110-2003 A.1.4).

1 differential protection or more?

Video 1.

Video 1 discusses savings in leakage current protection. How appropriate is it? 1 one at the entrance to an apartment (private house) often causes false (and not only) alarms with a complete shutdown of all devices and lighting. Calling and waiting in the dark for electricians is quite an unpleasant experience.

Photo 1. False tripping is caused by an incorrectly selected protection trip value. The longer the wiring, the more loads with the conversion of alternating voltage to direct voltage (TVs, computers, set-top boxes, etc.), the more reasons for the operation of a single installed RCD.
Photo 2. The obvious solution is to divide consumers into groups. The tripping current for normal rooms is 30 mA. In this case, the consumer is always disconnected at half this value - 15 mA.
Photo 3. For electrical appliances for wet rooms - boilers, washing machines set a differential relay with a value of 10 mA (and below). The small value of the protection operation requires the installation of a relay for each consumer.

Video 1 does not discuss the installation of a fire protection diffuser. When several differential relays are turned on with the same leakage rate, the device may be triggered both to a separate load and to the entire group as a whole.

Answers to 5 frequently asked questions:

1. Is it necessary to install an RCD in houses where protective grounding is performed?

When the phase conductor is closed to ground, electricity will “drain” bypassing the neutral wire. In this case, the metal cases of electrical appliances can be energized and will not cause danger as long as the human resistance is much higher than the "ground". However, such a device will be fraught with danger and if there is no significant overload, then the circuit breaker will not work. If energy escapes uncontrollably, there is a danger of heating and fire. The use of a differential relay will protect against these cases.

1. Is it possible to install one difavtomat after the counter instead of a machine before the counter and an RCD after it?

Yes. You can also put a circuit breaker after the meter with the obligatory installation of a disconnector (switch, etc. - requirements of the PUE) before the meter.

1. There are two differential relays connected in series in the circuit. When the protection closest to the consumer is triggered, the entire group of loads is disconnected. Which protective device should be removed from the wiring?

It is enough to apply a differential relay with selectivity (often marked with the letter S) for a consumer group. The sequential connection of the differential relay is regulated by the requirements of PUE 7.1.73.

1. Is it necessary to install an RCD at the input for a wooden private house? After all, the house is “isolated” enough?

Private houses often have an entry from an overhead line through a long cable. With a small value of consumption, there is no protective shutdown by automatic machines and quick shutdown is not ensured. In addition, according to Technical Circular No. 31.2012, the installation of differential protection is a mandatory fire-prevention measure.

1. Will the differential relay protect in the event of a break in the neutral wire?

In the absence of a leakage current, the protection will not operate, but when it appears, it will trip. Thus, even when the zero burns out, it protects against leakage. The differential relay does not protect against the very fact of a break in the neutral wire. This remark is true for electromechanical protection, for electronic, which requires both zero and phase for normal operation, a dangerous state appears when the protected load can lead to an electric shock. Therefore, it is not recommended to use the electronic type.