Automatic circuit breakers protect the power lines (simply - wires) from overloads caused by the connection to them of a large number of loads (for example, household appliances). These overloads significantly shorten the life of the lines, can disrupt the lines and can cause a fire. There is a widespread misconception that the circuit breaker serves to protect household appliances from overloading the network (and very often it is not specified which overloads). This incorrect representation generates a lot of errors when choosing the value of the circuit breaker. Often, when replacing or installing a circuit breaker, its value is chosen at random from the principle of "more useful and cheaper." In fact, the circuit-breaker protects not the devices, but the power lines from over-current, so the calculation of the machine protecting the line should be based on the parameters of the line (that is, initially, from the characteristics of the cable). For example, we can cite the case when a line made of an old aluminum cable cross-section of 1.5 mm. automatic machine with a face value of 40A was put. Thermal overloads on this line led to the fact that the life of this cable instead of 20 years was reduced to 2 months, after which it was necessary to completely replace the cable. It is quite clear that the replacement of cable pleasure is incommensurably more expensive than the correct choice of machine. protection.

2) Circuit breakers. Purpose.

Automatic switches  usually referred to simply as "automata". They are designed to protect electrical networks  from overload and short circuits. In the past, the functions of automatic machines performed plugs into which fuses were inserted. The main advantage of automatic machines is that, to re-enable them, it is sufficient to raise the lever, i. E. Do not need to change the fuse, as in traffic jams.

The main characteristics of automata - rated current  and pickup class.

Both these characteristics are always indicated on the body of the machine, for example: C16, B6, D32.

• The rated current characterizes the value of the current that the machine is able to skip (measured in amperes).
    If this value is exceeded, the machine will open and open the circuit. The automatic devices are produced with the following standard values ​​of the rated current: 6, 10, 13, 16, 20, 25, 32, 40, 50, 63, 80, 100A.

• The pickup class characterizes the short-time current value at which the machine does NOT work.
    There are trigger classes "B", "C" and "D".
    Class "B" automatic machines are used in networks without large voltage surges (in the range of 3 to 5 nominal current values).
    Class "C" automatic machines are most often used in apartments, offices and cottages. They are designed for currents 5-10 times higher than the rated current.
    Type "D" is used in networks where currents from 10 to 50 rated current values ​​are allowed.

At home, usually use ofphase (single-pole) machines. They serve to open the phase conductor. Less commonly, two-phase (two-pole) machines and "phase + neutral" automata are used. They simultaneously open the phase (L) and neutral (N) wires.

Three-phase (three-pole) and four-phase (four-pole) are used, as a rule, in industrial installations  with a voltage of 380 volts.

As a rule, the number of modules occupied by the automatic machine on the din-rail corresponds to the number of phases.

3) How to choose a circuit breaker?

At home, it is recommended to put an input machine and a separate automatic device on each line (for example, to the kitchen, to bathrooms, rooms, etc.). As it was already written above, it is recommended to use automats with the "C" operating class for the house.

When selecting the rated current, you should take into account the quality of the wiring and the total power of electrical appliances that are planned to be connected. In this case, the rated current of the machine must necessarily be less than the maximum current that the wire can withstand. For example, for copper wire  section 2,5кв. mm it is recommended to connect an automaton no more than 20A, and for 4kv. mm - 32A.

4) Dangerous mistakes.

Over 20 years ago, aluminum wiring  with a cross section of 1.5 mm2. For such a wiring you need automatic machines no more than 6A.

Today, when we use washing machines and dishwashers on a par with electric kettles, these machines can often work. A serious mistake in this case is the use of machines with a higher rated current (for example, 16A), since they will not turn off and it may seem that the problem is solved.

But in fact, when using such an automatic machine with such wiring, the danger of a short fire increases dramatically because of too high a load on the wiring. A large proportion of household fires occur due to misuse automatic switches.

It must be remembered that the machine does not protect a person from electric shock.

An electric breaker, or circuit breaker, is a mechanical switching device, through which it is possible to manually achieve the de-energization of the entire electrical grid or a particular section of it. You can do it in the house, apartment, in the country, in the garage, etc. Moreover, such a device is equipped with an automatic shutdown function electrical cable  In the event of an emergency: for example, in the event of a short circuit or during an overload. The difference of these circuit breakers from conventional fuses is that after the operation they can be turned on again.

Automatic (automatic switches) - this is what came to replace the usual traffic jams, i.e. fuses in the ceramic case where the overcurrent protection was a nichrome wire that burned out.

Unlike the cork, automatic device - reusable device, and the protection functions are separated. First, protection against overcurrents (short-circuit or short-circuit currents), secondly, overload protection, i.e. the mechanism of the machine breaks the load circuit with a slight excess of the working current of the machine.

In accordance with these functions, the circuit breaker contains two types of circuit breakers. Magnetic quick disconnect  protection against short-circuit with an arc extinguishing system (reaction time milliseconds) and slow thermal circuit breaker  with a bimetallic plate (the reaction time is from a few seconds to several minutes, depending on the load current).

Classification of electrical machines

There are several typical characteristics of switching off automata: A, B, C, D, E, K, L, Z

• A  - for breaking circuits with a long extension and for protecting electronic devices.
• B  - for lighting networks.
• FROM  - for lighting networks and electrical installations with moderate currents (current overload capacity is twice as high as in B).
• D  - for circuits with inductive loads and electric motors.
• K  - for inductive loads.
• Z  - for electronic devices.

The main criteria for selecting an auto switch

Short-circuit current limit

This indicator must be taken into account immediately. It means that the maximum value of the current at which the electric machine will operate and open the circuit. Here the choice is not great, since there are only three options: 4.5 kA; 6 kA; 10kA.

When choosing, one should be guided by the theoretical probability of the occurrence of a strong short-circuit current. If there is no such probability, then it will be enough to purchase a 4.5 kA automatic.

Automatic current

Accounting for this indicator is the next step. This is the required nominal value of the working current of the electrical machine. To determine the operating current, you need to be guided by the power that, presumably, will be connected to the wiring, or by the value of the permissible current (the level that will be maintained in the normal mode).

What do you need to know when determining the parameter in question? It is not recommended to use automatic machines with an overestimate operating current. Simply in this case, the machine will not turn off the power during overload, and this can cause thermal destruction of the wiring insulation.

The pole position of the automaton

This is perhaps the simplest indicator. To choose the number of poles at the switch, one must proceed from the way it will be applied.

So, a single-pole machine is your choice if you need to protect the wiring that goes from the electrical panel to the outlets and lighting circuits. Two-pole switch  It is used when it is necessary to protect all wiring in an apartment or a house with single-phase power supply. Three-phase wiring and load protection three-pole automatic device, and four-pole are used to protect four-wire power.

Machine characteristics

This is the last indicator you need to pay attention to. Time-current characteristic of the circuit breaker is determined by the loads that are connected to the protected line. When choosing a characteristic, the following are considered: the operating current of the circuit, the rated current of the machine, the cable carrying capacity, and the operating current of the switch.

In the event that it is necessary to connect small starting currents to the power line, i.e. electrical devices characterized by a small difference between the operating current and the current that occurs when switching on, preference should be given to the characteristic of tripping B. For more serious loads, characteristic C is selected. Finally, there is one more characteristic - D. Its choice should be stopped on it in that If it is intended to connect powerful devices with high starting points. What devices are you talking about? For example, about the electric motor.

Classification of RCDs

The RCD responds to a differential current, i.e. The difference between the currents flowing through the forward and reverse wires. Differential current appears when a person touches a protected circuit and a grounded object. RCDs to protect people are selected for a current of 10-30 mA , fire RCD - for a current of 300 mA. The latter protects the entire wiring system, and in case of fire, leakage currents usually occur earlier than short-circuit currents.

Devices protective shutdown  protect people from electric shock.

The choice of RCD is complicated by the fact that it is a more complex device than an automatic device. For example, there is difavatus  - devices that combine automatic and RCD. The RCDs are also divided into the electronic and the electromechanical types. Experience has shown that it is better to use electromechanical RCDs. They are better protected from false positives and from breakdowns.

By number of poles   The RCDs are divided into:

• two-pole for 220 V circuits;
• four-pole for 380 V circuits.

According to the operating conditions   on:

• AC- react only to an alternating sinusoidal differential current.
• A- reacting both to alternating sinusoidal differential current and to a constant pulsating differential current.
• AT  - reacting to an alternating sinusoidal differential current, a constant pulsating differential current and a constant differential current.

Due to the delay   on the RCD without delay in general application and with a time delay of type S. According to the current characteristic (Difavatus) for B, C, D. And, finally, for the rated current.

It should be noted that if the conventional Safety Shutdown Device and the machine stand in series in the same circuit, the machine must be at a lower current than the RCD. Otherwise, the RCD may be damaged. the machine breaks the load chain with a delay.

In conclusion, it should be said that you should choose the devices of well-known firms: ABB abb, GE POWER same power, SIEMENS Siemens, LEGRAND slipper  and others, at least certified in Russia. It is better to choose electromechanical RCDs, because they are much more reliable than electronic ones. Instead of a tandem from an RCD and an automaton, it is better to choose a difa-automat, this will make the shield design more compact and reliable. Current characteristics  must be selected depending on the wiring used. The operating current of automatic machines and automatic machines must be less than the maximum allowable cable currents.

For copper three-wire cables, the following data can be given for the correspondence of the conductor cross-section in square millimeters and the currents of automata:

• 3 x 1.5mm 2 - 16 Amperes;
• 3 x 2.5 mm 2 - 25 A;
• 3 x 4 mm 2 - 32 Amperes;
• 3 x 6mm 2 - 40 A;
• 3 x 10 mm 2 - 50 Amperes;
• 3 x 16 mm 2 - 63 A.

We hope that after reading all the material, it will be easier for you to understand the design and construction of electrical wiring.

History of the RCD

The first residual current device (RCD) was patented by the German company RWE in 1928, when the current differential protection principle, previously used to protect generators, lines and transformers, was used to protect a person from electric shock.

In 1937 the company Schutzapparategesellschaft Paris & Co. manufactured the first acting device based on a differential transformer and a polarized relay, which had a sensitivity of 0.01 A and a speed of 0.1 s. In the same year, with the help of a volunteer (a company employee), an RCD was tested. The experiment ended well, the device worked clearly, the volunteer experienced only a slight electric shock, although he refused to participate in further experiments.

All the following years, with the exception of the military and the first post-war years, intensive work was carried out to study the effect of electric current on the human body, the development of electrical protective equipment and the improvement and introduction of protective shutdown devices.

In our country, the problem of using protective shutdown devices first arose in connection with the electrical and fire safety of schoolchildren about 20 years ago. It was during this period that they were developed and put into production USOSH (school-operated RCD)  for the equipment of school buildings. It is interesting that UZO of this type is placed in school buildings up to now, although due to outdated technologies these devices no longer fully meet modern requirements of electrical and fire safety.

Another event that exacerbated the problem of installing an RCD was the reconstruction of the Moscow hotel "Russia" after a notorious fire that arose from the very ordinary short circuit. The fact is that the construction of this hotel complex violated the principles of electricity supply. Several tragic cases that led to the death staff, prompted the hotel management to plan the installation of protective shutdown devices in order to ensure electrical and fire safety.

At that time, such plants were produced only for industrial use. The installation of a protective shutdown for domestic use was assigned to one of the defense enterprises. But the tragedies were not prevented, and the fire that occurred as a result of the short circuit in the Rossiya Hotel resulted in numerous victims. After the fire, when the building was rebuilt, work was done on installing the RCD in each room. Since domestic RCDs were manufactured in a very short time and had drawbacks, they gradually began to be replaced by SIEMENS devices (Germany).

By this time, our electrotechnical enterprises began to think about the problem of manufacturing household protective shutdown devices. Thus, the Gomel Plant "Electroapparatura" and the Stavropol Electrotechnical Plant "Signal" have developed and began to manufacture household safety shut-off devices. And already from 1991-1992 the mass introduction of protective shutdown devices in house building began, at least in Moscow.

In 1994, the standard "Electrical supply and electrical safety of mobile (inventory) buildings from metal or with a metal frame for street trade and consumer services was adopted. Technical requirements". In the same year, a decree issued by the Government of Moscow on the introduction of RCD, which mandated the mandatory equipping of new buildings in Moscow with protective shutdown devices.

In 1996 it was released Letter of the Main Directorate of the State Service of the Ministry of Internal Affairs of Russia of 05.03.96 No. 20 / 2.1 / 516 « On the application of residual current devices (RCDs)". And the Moscow government made another decision to increase the reliability of electricity supply for the entire housing stock, regardless of the year of construction. We can say that from that moment the legalized mass introduction of RCDs in housing construction began.

At present, the application of RCDs has already been clearly described, and a number of regulatory documents that regulate technical parameters and requirements for the use of RCDs in electrical installations of buildings are in force. Today, RCD is an indispensable element of any switchboard, these devices are equipped with all mobile objects (camping sites, vans, public catering vans, small temporary electrical installations of outdoor installation arranged on the areas for the festive festivities), hangars , garages.

The option of connecting the RCD, which provides the most secure operation of electrical wiring. In addition, the RCDs are built into socket outlets or plugs, through which power tools or household electrical appliances operated in extremely hazardous, damp, dusty, conductive floors, etc. are connected.

Insurance companies in assessing the risk that determines the insured amount, necessarily take into account the presence of an RCD insurance facility and their technical condition.

At present, for each resident of developed countries there are on average two RCDs. Nevertheless, dozens of companies for many years, stably in significant quantities produce these devices of various modifications, constantly improving their technical parameters.

These are the main indicators that should be considered  when selecting a circuit breaker. Accordingly, if all the necessary data will be known to you, then the choice will not be difficult. It remains only to take into account the latest criterion - the manufacturer of the machine. What does it affect? It is obvious that value.

Indeed, there is a difference. So, the well-known European brands offer their automatic circuit breakers at a price that is twice the cost of domestic analogues and three times higher than the price of instruments from South-Eastern countries. Also, depending on the choice of a particular manufacturer, the presence or absence of a switch with clearly defined indicators in the warehouse depends.

Automatic circuit breakers are devices that provide wiring protection in short-circuit conditions when the load is connected with indicators exceeding the specified values. They should be chosen with special attention. It is important to consider the types of circuit breakers, their parameters.

Automatic machines of different types

Characteristics of automata

Choosing a circuit breaker, it makes sense to focus on the characteristics of the device. This is an indicator by which you can determine the sensitivity of the device to the possible excess of current values. Different types of circuit breakers have their own marking - it makes it easy to understand how quickly the equipment will react to the excess of the current to the network. Some switches react instantly, others activate for a certain period of time.

• A - marking, which is placed on the most sensitive models of equipment. Automata of this type immediately register the fact of overload and respond quickly to it. They are used to protect equipment that is characterized by high accuracy, but in everyday life they are almost impossible to meet
• B is a characteristic of which switches operating with an unimportant delay have. In the home, switches with the appropriate characteristics are used together with computers, modern LCD TVs and other expensive household appliances
• C - characteristics of machines that are most widely used in everyday life. The equipment begins to function with a slight delay, which is enough for a delayed response to the registered network overload. The network is switched off by the device only in the event that it has a malfunction that really matters
• D is the characteristic of switches having a minimum sensitivity to exceeding the current indices. Basically, such devices are used in the supply of electricity to the building. They are installed in the shields, under their control are virtually all networks. Such devices are selected as a backup option, since they are activated only if the machine did not turn on in time.

All parameters of circuit breakers are written on the front

Important!Experts believe that ideal indicators of automatic circuit breakers should vary within certain limits. The maximum is 4.5 kA. Only in this case the contacts will be under reliable protection, and discharges of current will be given in any conditions, even if the set values ​​are exceeded.

Types of automata

The classification of circuit breakers is based on their types and features. As for types, we can distinguish the following:

• Nominal indicators of the ability to disconnect - it is about the stability of the contacts of the circuit breaker to the effects of currents with high values, as well as to the conditions in which the chain deforms. In such conditions, the risk of burning increases, which is neutralized by the appearance of an arc and an increase in temperature. The more qualitative, durable is the material for the manufacture of equipment, the higher are its corresponding capabilities. Such switches are more expensive, but their characteristics fully justify the price. Switches serve for a long time, do not require regular replacement
• Calibration of the nominal - it is about the parameters in which the equipment operates in normal mode. They are installed at the stage of production of equipment, and already in the process of its use are not regulated. This characteristic allows us to understand how strong the overload is capable of withstanding the apparatus, the period of its operation in such conditions
• Setpoint - this indicator is usually displayed as a marking on the equipment case. These are the maximum values ​​of the current in non-standard conditions, which, even with frequent disconnections, will not have any effect on the functioning of the apparatus. The setting is expressed in current units, it is marked with Latin letters, with numerical values. The figures, in this case, represent the nominal value. Latin letters can be seen in the marking of only those machines that are manufactured in accordance with DIN standards

Electricity is very useful and at the same time a dangerous invention. In addition to the direct effect of current on a person, there is also a high probability of fire if the electrical wiring is not observed. This is explained by the fact that the electric current passes through the conductor and heats it, and especially high temperatures occur in places with poor contact or in case of a short circuit. To prevent such situations, automatic machines are used.

What

These are specially designed devices, the main task of which is to protect the wiring from reflow. In general, the machines do not save from electric shock and do not protect the equipment. They are designed to prevent overheating.

The method of their work is based on breaking electrical circuit  in several cases:

• short circuit;
• exceeding the current flowing through the conductor for this not intended.

As a rule, the machine is installed on the input, that is, it protects the next section of the chain. Since different wiring is used for breeding to different types of devices, it means that the protection devices must be able to operate at different currents.

In appearance it may seem that it is enough to install just the most powerful automatic machine and there are no problems. However, it is not. The current of large force, to which the protection device did not work, can overheat the wiring and, as a result, cause a fire.

The installation of low power machines will break the circuit each time, as soon as two or more powerful consumers are connected to the network.

What does the automaton consist of?

A conventional automatic machine consists of the following elements:

• Handle the platoon. With it, you can turn on the machine after it has been triggered, or turn it off to disconnect the circuit.
• The mechanism of inclusion.
• Contacts. Provide connection and open circuit.
• Terminals. They are connected to the protected network.
• Mechanism, triggered by the condition. For example, a bimetallic heat plate.
• In many models, an adjusting screw may be present to correct the nominal current value.
• Arc suppression mechanism. It is present on each of the poles of the device. It is a small chamber in which copper plated plates are placed. On them, the arc is extinguished and comes to naught.

Depending on the manufacturer, model and purpose, machines can be equipped with additional mechanisms and devices.

Disconnection mechanism

In automata there is an element that produces a break in the electrical circuit at critical current values. Their working principle can be based on different technologies:

• Electromagnetic devices. They differ in the high reaction speed for a short circuit. When the currents of an unacceptable value are acti- vated, the coil with the core is triggered, which in turn disconnects the circuit.
• Thermal. The main element of such a mechanism is a bimetallic plate, which begins to deform under the load of high-current currents. Bending, has a physical effect on the element, breaking the chain. Approximately the same circuit operates an electric kettle, which is able to shut itself down when the water boils in it.
• There are also semiconductor circuit breaking systems. But in household networks  they are used extremely rarely.

Types of machines by current values

Devices differ in the nature of operation at an excessively high current value. There are 3 most popular types of automata - B, C, D. Each liter means the sensitivity coefficient of the device. For example, an automaton of type D has a value from 10 to 20 xln. What does it mean? Very simply - in order to understand the range at which the machine is capable of operating, it is necessary to multiply the figure next to the letter by the value. That is, the device labeled D30 will be switched off at 30 * 10 ... 30 * 20 or from 300 A to 600 A. But such machines are used mainly in places with consumers who have large starting currents, for example, electric motors.

The machine of type B has a value from 3 to 5 xln. Therefore, the marking B16 means triggering at currents from 48 to 80A.

But the most common type of machine is S. Used in almost every home. Its characteristics are from 5 to 10 xln.

Conventions

Different types of machines are labeled in their own way for quick identification and selection of the necessary for a particular chain or its site. As a rule, all manufacturers adhere to one mechanism, which allows to unify products for many industries and regions. Let's analyze in detail the signs and figures put on the machine:

• Brand. Usually, the manufacturer's logo is placed on the top of the machine. Almost all of them are stylized in a certain way and have their own color, so choosing the product of your favorite company will be easy.
• The indicator window. Shows the current status of contacts. If there is a malfunction in the machine, then it is possible to determine if there is any voltage in the network.
• Type of machine. As already described above, means a trip characteristic at currents much higher than the rated current. Most often, C is used in everyday life and slightly less often B. The differences between the types of electrical machines B and C are not so significant;
• Rated current. Indicates the value of the current strength, which can withstand a prolonged load.
• Rated voltage. Very often, this indicator has two meanings, written through a slash. The first is for single-phase network, the second - for three-phase. As a rule, in Russia the voltage in 220 V is used.
• Limiting switching current. Means the maximum permissible short-circuit current at which the machine will shut down without failure.
• Class of current limitation. Expressed in one digit or not at all. In the latter case, it is considered to be a class number 1. This characteristic means the time at which the short-circuit current is limited.
• Scheme. On the machine, you can find even a diagram of connecting contacts with their notation. It is almost always in the upper right part.

Thus, looking at the front of the machine, you can immediately determine which type of current it is designed for and what it is capable of.

What type of machine should I choose?

When choosing a protective device, one of the main characteristics is considered to be the nominal current. For this it is necessary to determine what current strength is required by the aggregate of all consumer devices in the house.

And since electricity flows through the wires, the current required for heating depends on its cross section.

The presence of poles also plays an important role. Most often this practice is applied:

• One pole. Chains with lighting devices and sockets, to which simple devices will be connected.
• Two poles. It is used for the protection of wiring, conducted to electric stoves, washing machines, heating appliances, water heaters. It can also be installed as a protection between the switchboard and the room.
• Three poles. It is mainly used in three-phase circuits. This is relevant for industrial or near-industrial premises. Small workshops, manufactures and the like.

The tactics of installing machines come from the larger to the smaller. That is, first it is mounted, for example, a bipolar pole, then a single-pole one. Next come the devices with the power decreasing at each step.

• When choosing, it is necessary to focus not on electrical appliances, but on wiring, as it will be protected by automatic switches. If it is old, it is recommended to replace it so that you can use the most the best option  machine.
• For premises such as a garage, or for the duration of repairs, it is worth choosing an automatic machine with a larger rated current, since different machines or welding machines have rather large current strengths.
• It makes sense to complete the entire set of protective mechanisms from the same manufacturer. This will help to avoid a mismatch between the rated currents between the devices.
• You can buy automatic devices in specialized stores. So you can avoid buying a substandard counterfeit, which can lead to disastrous consequences.

Conclusion

No matter how simple the wiring of the circuit seems to be around the room, always remember the safety. The use of automatic machines largely helps to avoid overheating and, as a result, its ignition.