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Since the invention of the electric light bulb, electrical engineering has been advancing by leaps and bounds. Today we cannot imagine life without electricity. BUTbecause it, in addition to comfort and convenience, carries a threat. The danger, first of all, is associated with the possibility of electric shock to people, secondly— with fires that occur due to malfunctioning electrical equipment and wiring, not to mention the failure of expensive household appliances. But all this can be avoided if competently and in a timely manner to take care of protection measures.

Do not think that only a negligent electrician is capable of getting under voltage. Each of us can get an electric shock, and for this it is not at all necessary to climb into the switchboard or break the wires. A sensitive blow is easy to get by touching familiar household appliances— fridge, washing machine andt.e. If the insulation of the current-carrying wire is broken, the body of the electrical appliance may be energized. Andif it is not grounded, if you touch this device, an electric shock will almost certainly strike. So, in the interests of electrical safety (your own and your home), you need, firstly, to take care of grounding.

Secondly, traditional circuit breakers, whose progenitors were plugs, save from overloading the network as a result of turning on a large number of electrical appliances and a short circuit (this is already an extreme case).

Finally, the most important question is how to protect yourself from serious injury if you touch a live conductor, and God forbid, in a damp room. Andhow to avoid a fire caused by electric leakage. Here, special residual current devices (RCDs) come to the rescue, which recognize the slightest current leakage and interrupt the power supply to the entire apartment or a separate current-carrying wire.

The devices listed above, grounding and a mandatory meter (without it, the energy company will not supply voltage) are mounted in the electrical panel installed today in all apartments (or stairwells) and cottages. The cost of «stuffing» such a locker with the maximum configuration of the home with electrical appliances and taking care of their serviceability and one’s own health can be hundreds of dollars. Saving on safety is often much more expensive, so in this review we set out to introduce you to the full range of tools and devices that resist electrical danger.

grounding

As we have already said, grounding is the basis for ensuring electrical safety. ATideal case for each appliance rated for 220In, whether it’s a table lamp or a TV, three conductors must fit: phase, zero and protective. This solution has become commonplace and is increasingly replacing the outdated two-wire connection scheme. Phase conductor (L), or in everyday life a phase,— this is a working conductor that is energized and supplies the consumer. It must be supplemented by a zero conductor, in a different way— working zero (N), or «neutral». Zero protective conductor, or «protective earthing» (PE), provides grounding of the network. For it, as a rule, a wire in yellow-green striped insulation is used.

If your house was built after 1998-1999, then, most likely, a protective zero conductor PE has already been stretched to the sockets, or, as the «specialists» say, a protective zero has been wound up. ATIn this case, groups of wires are laid from the switchboard to your apartment: for lighting— 2 conductors, phase and neutral (L+N); group for sockets— 3 conductors (L+N+PE); group on the electric stove— 3 conductors (L+N+PE). That is, 3 wires must go to the sockets, and the neutral and protective (N and PE) in no case can be connected to a common terminal on the shield.

If you live in a house of an earlier construction, from the seventies and eighties, there may not be a protective zero on the sockets. FROMon the other hand, the floor plate is usually grounded. Therefore, it makes sense to invite an electrician from the local DEZ. He knows for sure whether there is a reliable ground in the shield, and if necessary, he can lay an additional zero protective conductor to one of the sockets, for example, to connect a washing machine.

So, in a city apartment with protective grounding, it is more or less clear. BUTHere, the owners of their own home have something to break their heads over.

As a rule, the supply to such houses is carried out through an overhead power line, and the shield in the house is not grounded (and this must be done!). ATIn this case, it is completely unacceptable to use the incoming zero working N-conductor as a protective PE-conductor. In the event of a break in the overhead power line (for example, a tree has fallen), the neutral conductor (N) may be energized. Then the same voltage value will appear on the protective conductor PE (to which, in theory, the cases of all household electrical appliances are connected), and from a protective one it will turn into a deadly one! Therefore, it is especially important to carry out grounding in the cottage. What is needed for this?

First of all, you can use natural grounding conductors, which can become:

water and other metal pipelines laid in the ground, with the exception of pipelines of flammable liquids, flammable and explosive gases and mixtures, sewerage and central heating;
well casing pipes;
metal and reinforced concrete structures of buildings and structures in contact with the ground.

If there is such an opportunity, it is good to withdraw from them. The outlet is equipped only by welding— this is the only way to ensure the required cross-sectional area. ATas a grounding conductor, use strip steel with a cross section of at least 48mm² with a thickness of at least 4mm or steel angle with a shelf thickness of at least 2.5mm. A strip or a corner is laid in a room where it is necessary to make a ground loop from a steel strip with a cross section of at least 24mm² and a thickness of at least 3mm. Another option: a bolt is welded to the strip (corner), a copper conductor is attached to it (from 2.5mm²), which will be the protective PE conductor.

If the house is wooden, and there are no pipelines or wells nearby, you need to make an artificial ground electrode. This is a very difficult task. In addition to the fact that a large amount of soil will have to be transferred, it will be necessary to additionally carry out some calculations and measurements of the electrical resistance of the soil on site. It is better to entrust all this work to qualified specialists.

Organization of protective grounding— this is only the first step in ensuring the electrical safety of a person and a home. The next step in the organization of protection can be circuit breakers, or, as they are more commonly called, automata.

Circuit breakers

To begin with, we note that sockets, switches, automation, meters and much other household electrical equipment are produced in a wide range by a number of companies. To name just a few: ABB, AEGKopp, BuSch-Jaeger Electro, Siemens (Germany), Schneider Electric, Legrand (France), «ASTRO-UZO» (Russia) andothers

Automatic switches (automatic devices)— the most widely known and familiar protective device. Designed to protect the circuit from short circuits and overloads. They replaced burnt plugs— one-time progenitors of electrical protection— 20-30 years ago. Today, machines are equipped with a special actuator— a release that directly opens the electrical circuit.

Most of the modern household circuit breakers on the Russian market— combined. They have an electromagnetic and thermal release and can simultaneously protect against network overloads and short circuits (short circuits). Electromagnetic release— this is an electromagnet capable of protecting the circuit from a short circuit when the current instantly increases to critical values, 5-10 times (category C) exceeding the nominal values. In this case, the machine must turn off the circuit in a time of about 0.01 seconds. Thermal release— a bimetallic plate that changes its shape when heated. This element prevents critical overloads, accompanied by a significant heating of the conductors, the braid of which can ignite. An automatic machine with such a mechanism, at a load exceeding the nominal value by 13%, must turn off the circuit within an hour.

ATdepending on the operation characteristic, circuit breakers are divided into groups: B, C and D. To protect networks in the housing and communal sector, category C devices are usually used, since they are universal and designed for short-circuit currents that are 5-10 times above the rated current. Circuit breakers of this category can also be used in circuits supplying electric motors, pumps andt.e. Less commonly used in everyday life are more sensitive automatons of category B. They operate at currents 3-5 times higher than the nominal value, and are used in electronics.

Devices of both categories are issued in denominations of 6, 10, 13, 16, 20, 25, 32, 40, 50 and 63A. It is important to note that the rating of the machine is selected based on the permissible current load of the conductors. That is, the compliance of the characteristics of the machine and the cross sections of the conductors with the power consumption that is included in the electrical installation project of a house or apartment must be achieved.

There are one-, two- and three-pole switches. The first ones are set to open the phase (live wires), and they are most often used in apartments and houses. Less commonly used are bipolar, which turn off not only the phase, but also the neutral wire. BUTthree-, four-pole machines are designed for a three-phase connection with a voltage of 380B, where three energized phase wires, one neutral wire and one protective wire are woven in one cable.

Common mistake— the use of an automaton with an overestimated tripping current. Actually, this is not even a mistake, but a violation. For example, in an old house with dilapidated wiring, the socket protects the machine at 10And, and the owner of the apartment acquires a modern electric kettle with a power consumption of 2.2 kW and turns it on. What’s happening? The machine works. The owner, without hesitation, replaces the machine with another, with a large trip current— at 16Oh, and even 25A (whatever comes to hand). After that, the machine will no longer “knock out”. But the network, which was not originally designed for such currents, will start to work with a large overload. Conductors will overheat. With luck, the circuit breaker will trip when a short circuit occurs as a result of the melting of the wire insulation. Although life shows that in such cases, ignition of the wiring occurs earlier.

Modern models of machines are mounted on the so-called DIN rail, which is a mounting rail-bar with a width of 35mm, corresponding to a single international standard. ATIn the residential sector, such machines will certainly displace (and are already displacing) devices of old standard sizes that are mounted with screws.

As already mentioned, machines, first of all, protect electrical circuits from overloads. Tripping currents for which the circuit breakers are designed,— from 6 to 100A. Bif a person touches a live conductor 220In a broken insulation, such currents may not occur. If the resistance of the human body is conditionally taken equal to 1000 ohms (with the current flow path arm / leg), then the current passing through the body is equal to 220 mA. For a person, this is a serious electrical injury, but the machine does not perceive this value as a short circuit current and does not turn off the circuit. Therefore, to protect a person from accidental electric shock, another device is needed.— it is a protective shutdown device.

Residual current devices and differential automata

Their active introduction into wide practice began in the sixties and seventies of the last century all over the world, especially in Western Europe, Japan and the USA. To date, the USO— the only one of all known electrical protective equipment that not only provides protection for a person from electric shock, but is also able to protect against ignition and fires due to a malfunction of electrical wiring and electrical equipment. Largely due to this, insurance companies, when assessing the risk that determines the sum insured, necessarily take into account the presence of protective shutdown devices at the facility and their technical condition.

ATon sale there are RCDs designed for two rated voltages (the effective value of the voltage at which the operability of the device is ensured)— 220 and 380B, as well as for rated currents of 6; 16; 25; 40; 63; 80; 100; 125A, which the device can skip for a long time. Obviously, the choice of the device according to the first parameter depends on what voltage you have in the network, while the rated current is determined by the power consumed by household appliances in the protected circuit. An estimated calculation of power consumption was given in the article «Home Energy».

Rated residual breaking current— this is the most important parameter of the residual current device for the consumer. FROMfrom a technical point of view, we are talking about the leakage current strength, which causes the RCD to trip under specified operating conditions (0.006; 0.01; 0.03; 0.1; 0.3; 0.5BUT). That is, when such a leakage current occurs, the circuit will instantly open. For wet areas— sanitary cabins, bathrooms and showers,— if a separate line is allocated to them, it is recommended to use an RCD with a trip current of 10 mA. ATin other cases, even for street sockets, it is allowed to use an RCD with a trip current of 30 mA. Separately, to increase the level of fire protection at the entrance to an apartment or an individual house, experts recommend installing an RCD with a trip current of 300 mA.

The reliability and quality of RCDs are determined by the conditional short-circuit current— 3000, 4500, 6000, 10,000A (this parameter is sometimes called «short-circuit current resistance»). The higher the specified value, the more reliable your residual current circuit breaker will be.

There are two types of differential disconnect devices: AC and A. The difference between them lies in the sensitivity of these devices to direct current that appears in a normal variable network under the influence of household appliances. RCD type AC has a special designation on the case— a sinusoid in a rectangle. It is sensitive only to alternating (sinusoidal) leakage current, while speed-controlled washing machines, adjustable light sources, VCRs, computers, audio equipment distort, rectify the sinusoid and are sources of pulsating current. ATUnder such conditions, an RCD of the AC type sharply loses its sensitivity, and hence the ability to reliably protect a person from electric shock. Type A devices come to the rescue here, responding to both alternating and pulsating fault currents (leakage currents with a constant component). Such RCDs are 20-50% more expensive than AC-type RCDs, but for groups of outlets, and for lighting groups, it is advisable to use them.

Residual current devices of both types (AC and A) exist either in the S (selective) version or in the conventional version. Execution S (type A or AC) implies operation with a time delay. It is used when it is necessary to give additional time for the primary operation of other protective devices or circuit breakers.

You can check the operation of a newly installed or long-running RCD by pressing the «TEST» button, which is on the front panel of most devices (in addition to the on-off switch). Pressing this button artificially creates a residual tripping current. If the RCD is OK, it should trip. Manufacturers recommend that this check be carried out monthly. After the RCD has tripped and the malfunction that caused it has been eliminated, the device is again brought into working condition by the power lever.

Protective differential devices can be installed in an existing distribution cabinet of an apartment— one device with a nominal value of 30 mA for the entire dwelling. This option is relatively cheap, but it does not allow you to determine the location of the leak, and, in addition, when the RCD is triggered, the entire apartment is left without light. A much more progressive solution, which makes sense to strive for,— installation of several protective differential devices on separate lines. ATIn this case, the electrical wiring is divided into independent branches serving various consumer groups. For example, the following layout is possible: separate branches for a group of sockets, for lighting, for a group of power devices (washing machine, electric stove), a separate branch for a bathroom and shower.

Each group must be controlled by its own circuit breaker and its own RCD. To do this, independent (starting from the switchboard) wires for the phase (1 to 220B or 3 by 380B), for neutral N and for earth PE. The presence of a separate ground wire, as we have already said, increases the level of safety.

With such detail, it is possible to fully implement stepwise or selective protection, the principle of which is the ability to determine exactly which device caused the leak and disable only it. The rating (nominal breaking differential current) of each subsequent protection from the input of electricity to the house is selected one step lower (or even less), but it can never be more! In other words, if there is an RCD designed for a leakage current of 30 mA at the entrance to the apartment, then the RCD intended for the branch of the bathroom, kitchen or a separate washing machine should be calculated for 10 or 6 mA. If this condition is met, in a critical situation, the protective device closest to the fault will operate first. For example, in the event of a malfunction in the electric stove, the RCD will trip in the electric stove circuit. All other lines, including lighting, will remain operational. In order for the protection in front of the object to be guaranteed to work in the first place, an RCD is mounted on the input-distribution device, which operates with a certain time delay (of the order of 0.1-0.5 seconds), that is, an RCD in S-selective design.

Protecting against leakage currents, the RCD has a narrow specialization and is in no way capable of replacing a circuit breaker. Overload or short circuit protection— the patrimony of the automatic switch, which must be installed to protect the electrical circuit and the differential device itself. For example, an RCD with a rated operating current of 25And it is necessary to protect it with an automatic device having a trip current of not more than 25BUT.

In order to avoid the need to purchase many different machines and RCDs, manufacturing companies have created and put on the market devices with built-in protection against short circuits and overloads.— differential machines. This is a kind of hybrid of a circuit breaker and an RCD in one housing. An example of such devices are the models of the Multi 9 series from SCHNEIDER, RCD from KOPP, DS 941 from ABB, as well as devices from Legrand. Moreover, the latter even have a transparent plastic pocket for easy marking of the protected circuit. The presence of differential automata on the market has greatly simplified the life of consumers, who now do not need to think about matching the electrical parameters of the RCD and the circuit breaker.

The differential machine opens the electrical circuit when it is exposed to any of the three malfunction factors:

short circuit (coils with a core react to it);
overload current (bimetallic plates are triggered);
differential leakage current (in this case, the magneto-electric release operates).

Protection against lightning and induced surges. Dischargers

overvoltage— impulse excess of the rated operating voltage of the network, power surge during a lightning strike (can reach 15 kV). Overvoltages and, as a result, failure of electrical wiring, equipment and devices, fires can occur in the network in the following cases:

Direct exposure to high-voltage atmospheric discharge— at the points of a direct lightning strike, strong currents can flow in the conductive elements.
Direct hit at one point. It is capable of causing overvoltages at a distance of several hundred meters to several kilometers from the place of a lightning strike. Spreading through power grids, pipelines andt.etc., an overvoltage impulse enters buildings and disables electrical equipment.
Lightning strike to the ground. An overvoltage surge on a ground conductor can propagate through the ground.

ATduring the operation of electric motors (in elevators of apartment buildings, pumps andt.e) the appearance of high-voltage discharges of non-atmospheric origin in the network of the house is likely.

An overvoltage between the mains and the ground can completely disable the electrical panel. An overvoltage that occurs between the phase conductor and the «neutral» damages electrical equipment (audio-video equipment and computers). ATIn this case, the protective shutdown helps out when the voltage in the network is exceeded. Devices that allow such a shutdown are called arresters (or surge suppressors). The main task of the arrester— send an overvoltage impulse to the ground, therefore, the instrument case provides the possibility of connecting a grounding conductor with a cross section of 10mm2 or more. Arresters are mounted immediately behind the introductory circuit breaker and are necessarily connected to the «ground» terminal of the electrical panel.

All arresters certainly have an operating status indicator. After one or two operations (lightning strikes), devices from ABB and Schneider must be replaced, as indicated by the LED indication on the front panel. ATunlike these arresters, LEGRAND devices consist of a base and a working module. This is especially useful for four-pole arresters in a network designed for 380B (protection of three phases and earth), since it becomes possible to replace only one of the four modules.

Among the devices of Russian manufacturers, arresters of the OPN-12 / 0.4 brand of the ASTRO-UZO company are known. Designed for maximum current up to 10 kA and voltage up to 1200B, they allow you to reduce the overvoltage to a safe value, at which there is no breakdown of the insulation of electrical equipment.

A few words about electricity meters

As a rule, foreign manufacturers that produce devices for mounting on a DIN rail necessarily include electrical measuring instruments in their product range.— ammeters, voltmeters and electric meters. However, before purchasing a branded electricity meter that you like, you need to get it from your local electricity supplier office.— «Energosbyt» consent to its installation in your apartment or house. BUTsince each newly installed electric meter goes to the balance of such an organization, it exercises control over it, assumes the responsibility for its repair and maintenance, then all models of electric meters, Russian and imported, must be certified and only after its successful completion are recommended for widespread use.

ATAt present, domestic electric meters «INCOTEKS» are widely represented on the market (Kazakhstan).Moscow), LEMZ (city ofPetersburg), Mytishchi plant andetc. They are affordable and mounted in the shield in the traditional way— on screws. But to date, modules installed on a DIN rail have practically replaced all others. Andit would be very convenient to have a DIN-rail-mountable electricity meter, for example, the certified DAN 2902 Delta model, which ABB produces at the Metronica plant in Moscow. I would like to note that among Russian electricity meters there are those installed on a DIN rail. This is, say, a single-phase model TsE 6807 B-1 and a three-phase meter TsE 6807 B-2 of the Energomera Stavropol plant.

Switchboards

And now, finally, we have come to the moment when the scheme for protecting the electrical network of your home has already been selected, all protective modules have been purchased, their number and models have been determined. Now the devices that make up the circuit you built need to be installed (hidden) somewhere. To do this, SCHNEIDER, SIEMENS, ABB and some others produce plastic shield cases that provide high user safety and fit perfectly into the interior of an apartment or house. For example, ABB supplies the Russian market with a plastic case model 13204, designed for 12 modular blocks, in which a special place is provided for mounting the Russian electric meter model SO-505 on the screws. The housings of all shields are made of self-extinguishing plastic, which does not conduct electricity. The design of the housings is such that it completely eliminates accidental access to live parts.

For ease of installation of equipment in the switchboards, unified components are used:

DIN rails on which all equipment is mounted;
terminal bars— for convenience of joining of conductors;
comb taverns— for ease of switching of several devices installed in a row;
side plugs— protective caps used to isolate open live parts;
protective and decorative panels that completely cover the installation wires inside the cabinet body.

The enclosures of the shields can be supplied in hinged and built-in versions. Hinged cases are mounted on a wall and are used, as a rule, for open electrical wiring. Recessed shields are installed in a wall niche and are usually used for hidden wiring. Tocase you can choose a transparent or matte door and mortise lock. A huge variety of decorative doors for lockers will not leave anyone indifferent.

When choosing a switchboard, you should take into account that manufacturers recommend— to create favorable working conditions for electrical equipment— provide up to 30% free volume inside the box. In addition, in the future, this unoccupied space makes it possible to install some additional equipment (during the modernization of the power grid).

Towho to contact?

Recently, many companies have appeared that are engaged in the installation of electrical equipment and perform the entire range of electrical work. When concluding an agreement with such a company, you should pay attention to the availability of a license confirmed by Energonadzor.

To connect household appliances, it makes sense to contact the seller’s service center.

BUTto lay a zero protective conductor when connecting, for example, a new washing machine, without having in mind the complete modernization of the electrical wiring in the apartment, you can invite a representative of the service organization (DEZ, ZhEK andt.d.).

The editors would like to thank the CROCUS-TRADE company and the accredited representative office of LEGRAND in Russia for their help in preparing the material.

• Source: Ideas for Your Home Magazine, No. 75