IN modern house It is impossible to do without electricity. All kinds of equipment that supports the comfort and life support of the inhabitants of the house requires a high-quality and safe electrical network. Properly executed electrical wiring that ensures safe and uninterrupted power supply to the home is not an easy task, but it is quite within the power of many owners. The main thing is to correctly understand and comply with all the principles and requirements for carrying out work on the electrification of residential and utility premises.
In order to correctly install the internal line of house electrical wiring, it is necessary to understand the types of electrical wires, their purpose, as well as other basic concepts.
Aluminum wires are often used for internal wiring, although they are inferior to copper wire in many respects. The only advantage that aluminum wires have is that they are not high price. At the same current loads, the cross-section of the aluminum wire must be larger than the cross-section of the copper wire, and this is inconvenient. Physical properties metal of aluminum wires cause less reliable connection, how copper wires. In addition, aluminum is highly oxidizable, which affects the electrical contact of aluminum wires with each other and with wires made of other metals. Because of this, all mechanical contacts of aluminum wires require periodic compression, otherwise heating will occur at the point of contact and, as a result, a possible fire. In addition, when aluminum oxidizes, it affects the vinyl insulation of the wires and it deteriorates over time.
The modern market offers many solutions to the problems mentioned above. This is a whole range of single-core and stranded, solid and stranded copper wires PV series, the cross-section of which can be selected for any expected current load. Double-insulated wires of the VVG series (vinyl - vinyl - bare) have increased reliability and are therefore very convenient for external and internal wiring in country and cottage construction. In those rooms where increased requirements are placed on the reliability and safety of wiring, PUNP wires (wire - universal - flat) with reinforced insulation can be used.
Specialized stores offer many options for choosing electrical cables. Among various types There are multi-core and single-core cables. For fixed wiring, it is better to choose a single-core cable. Such a cable has increased resistance to mechanical stress, it is less susceptible to oxidation and, as a result, loss of contact. Where the wiring will be subject to movement (for example, when replacing electric lamps or moving electrical appliances), the use of flexible stranded electric cable, PVA type (wire - vinyl - connecting), more preferably.
In rooms with high fire hazard NYM cables are recommended.
NYM is a German name meaning:
These cables have fireproof padding that releases fire retardants when heated. For rooms with high temperatures, for example, sauna, etc. There are heat-resistant cables that can withstand temperatures up to 800°C. In addition, such cables are moisture-resistant and flexible.
The parameters characterizing various electrical wires are divided according to the dependence of their cross-sectional area on the permissible value of the passing current. In order to determine the required cross-sectional area of the wire, it is necessary to know the expected maximum current strength passing through the wire, taking into account the heating of the insulation. The permissible operating temperature for heating electrical wires should not exceed 65-70°C (depending on the insulation material). At a room temperature of 25°C, the permissible heating of the insulation is 40-45°C. Taking into account these conditions for the cross-section of wires made of copper and aluminum, using the tables provided, it is possible to determine the permissible current loads.
If the cross-sectional area is unknown, then it can be calculated using the formula:
S = 0.785 d²,
where S is the cross-sectional area in mm², d is the wire diameter measured (with a caliper) in mm.
The cross-section of a stranded wire is determined by summing the cross-sections of all cores in the wire.
The most used modern cable for laying electrical wiring inside the house is copper cable VVG with two layers of insulation. This cable is designed for current voltages of 600 and 1000 V, and a frequency of 50 Hz. When using this cable, you can use the following recommendations by choice of section:
Electrical wiring inside the house is laid in two ways. The first method is open wiring. The second method is hidden wiring.
Open wiring is used if the walls are already fully completed and finally lined or there is no need or desire to hide the wires. In wooden houses, open wiring is the norm of modern safety requirements. In a wooden house (unlike a stone house), wiring can be damaged by rodents, and accumulated wood dust instantly ignites in the event of a short circuit.
Exposed wiring is easy to install, easier to maintain and monitor, and can be moved or added to if necessary. If earlier, when executing open wiring on wooden walls contact of the wire with the wood was not allowed (it was necessary to maintain a distance of 15-20 mm), but now this is permissible. Wires can be laid along the surface of the wall, fixing them using electrical clips of a suitable size. The distance between the clips is selected based on the rigidity of the wire, but not more than 1 m. The main condition when the wire comes into contact with wooden wall- this is the presence of at least double insulation (VVG cable).
Open electrical wiring can be done in a corrugated polymer pipe. Several wires can be placed in such a pipe at the same time. Although safety will be maintained, the aesthetics of such wiring, especially in residential premises, will leave much to be desired. In addition, if it is necessary to gain access to a separate section of cable (or a separate cable), a large amount of wiring will need to be removed.
The electrical wiring made in polymer cable ducts with a removable cover looks quite neat and harmonious. They come in a variety of sizes and capacities, come in a variety of colors and are made of non-flammable plastic. Cable channels are easy to install and convenient for maintaining wiring and making additions and changes. There are many additional devices for cable channels - turns, external and internal corners, tees and plugs.
For open wiring, copper wires are used. If you use aluminum ones, then when passing through combustible wall structures you will have to use a layer of sheet asbestos with a thickness of at least 3 mm and protruding from each side of the wire by at least 5 mm. This is inconvenient and unaesthetic.
Hidden wiring is usually carried out before plastering or facing works. Benefits hidden wiring are:
Depending on the wall material and other conditions, the list the necessary tool will change. However, there is a list of tools that you cannot do without in any case. You will definitely need the following tools:
In order to carry out the wiring, you need to know the installation locations of the electrical panel, junction boxes, sockets, switches and lamps.
The electrical panel is usually installed in close proximity to the entrance to the house and, as far as possible, from the entrance of the external electrical cable. The location for the electrical panel must be protected from dampness (moisture) and possible mechanical influences (for example, when bringing furniture into or out of the house, etc.). The electrical panel is attached to a wall or other rigid structure that is not subject to shocks, away from heat sources at a height of 1.4-1.7 m from the floor.
The electrical panel must be easily accessible for maintenance, as well as for turning on and off the general switch and safety devices.
Sockets are placed taking into account the layout of the room and the number of possible electrical appliances. There are no superfluous sockets. It is better to install more sockets, including double or even triple and quadruple, than to abuse extension cords and tees later.
It is better to place sockets at a height of 300 mm from the floor, and those located above desks and in similar places - at a height of 1000 mm.
Places for switches in the room are selected depending on placement (ceiling and wall), type (stationary and mobile) and number of lighting fixtures.
There can be several switches (for each lighting fixture) or one multi-key for several lamps.
The height of the switches is selected approximately at eye level (1600-1800 mm from the floor) or at the level of the palm of the lowered hand (700-900 mm from the floor).
After all the locations for the panel, sockets and switches have been determined, select a location for the distribution boxes. Moreover, the fewer of them you need, the better (additional connections are difficult to install and a source of additional danger).
Distribution (branch) boxes can be placed both in the room itself and in the corridor. Depending on where the common line runs, the distribution box itself is located at the same level (height).
The wiring line is placed:
After the marking is completed, the actual laying of the wire begins.
Laying open wiring does not cause any particular difficulties. In addition, the main methods of fastening and laying the cable have already been discussed above.
The main thing in any method of laying electrical wiring is accuracy and compliance with all the rules for the safe execution of the electrical network at home.
During installation hidden electrical wiring the wire is laid in a groove made in the wall. The groove (channel or groove) is made of the required width (slightly wider than the diameter of the wire or cable protection used). The cable is laid in the groove and fixed with alabaster or cement mortar. After installation is completed, the groove is filled with putty.
Simultaneously with the grooves for the wire, sockets are made for distribution and installation boxes, sockets and switches.
In brick, block or concrete walls The groove is selected using a grinder (with the required type of disk) and a hammer drill. If there are seams in the wall (block or brickwork), then the grooves should be combined with them (both horizontally and vertically).
The width of the groove is slightly larger than the diameter of the round cable or the thickness of the flat cable, and the depth is 8-10 mm larger than the diameter of the round cable or the width of the flat cable.
Once the distribution boxes are installed (and the entrance and exit windows are correctly oriented), you can begin laying the prepared sections of cable or wire into the grooves. The free ends of the wires are inserted into distribution boxes with a margin of 150-200 mm.
If the walls are made of plasterboard or other cladding material, then the cable is pulled behind the cladding from box to box along the shortest path. Holes are cut in plasterboard (or other cladding material) for distribution boxes (special for this material), and then they are mounted using special mounting screws.
When laying cables in metal or plastic pipes, the cable is pulled into them using a conductor (steel wire or cable).
Sockets and switches have special terminals in their design for connecting wires. There are four types of terminals:
The operation of stripping the end of the cable requires special care; this is done as follows:
After stripping the ends of the wires, they must be connected to the terminals. The wires in a cable usually have different colors of insulation. It is customary to use a blue (brown) wire for the phase wire, black (or white) for the neutral wire, and yellow-green for the ground wire. But the most important thing is that the markings are the same in all rooms of the house.
When laying a home electrical network, sometimes the installation boxes of sockets are simultaneously used as switching boxes. Both the incoming and outgoing wires are attached to each terminal at the same time.
When installing the switch, the phase wire is attached to the moving contact terminal, and the zero wire is attached to the fixed contact terminal. If the switch has several keys, all its moving contacts are output to one terminal (to which the phase wire is connected), and neutral wires are connected to the terminals of the fixed contacts. Neutral wires are supplied to lamps (or groups of lamps) as phase wires; they are connected to the central contact of the electric cartridge. The wires from the threaded contact into which the lamp base is screwed are connected to the neutral wire.
If you need to install several sockets (or several sockets and switches) in one housing in one place, you can use special installation boxes with adapters that combine all devices into one block.
The electrical wiring of a home consists of many elements. All these elements will eventually need to be connected into a single network. Each connection (switching) must be reliable and safe. All connections must be made only in the junction box. The distribution box must always have free access to it (not be plastered or tightly sealed with cladding) and located in accessible places (without additional actions to free up space for access to it).
Basically, for connecting wires, the method of twisting them together (twisting) is used.
This method requires, to ensure its reliability and safety, one of the following additional operations (clause 2.1.21 of the PUE):
This is not the simplest method in terms of technological execution, but it provides very high reliability of wire connections. To perform soldering you need:
For crimping, you will need a tool with which you can reliably crimp the junction of the wires and a special sleeve-tip. The sleeve-tip (or GAO - aluminum sleeve for crimping) is an aluminum tube with or without lubricant. As a crimping tool, you can use hand press pliers, pliers, a mechanical or hydraulic press. Next, perform the following steps:
Welding is the fusion of metal wires into one core under the influence of electric arc. The method is very effective, but requires special welding machine and is more suitable for professionals than for independent performance.
Crimping is the most technologically accessible method of strengthening and isolating switching, and no less effective than the previous ones.
Crimping of twisted wires is carried out using terminal blocks, PPE caps (connecting insulating clamps), or clamps from WAGO.
Terminal blocks allow you to connect copper and aluminum wires, since they do not have direct contact. These products are available for various wire sections and are easy to use. Switching in such blocks is possible in two ways:
PPE caps are twisted with force onto the twisted wires. Under the influence of forces, a conical metal spring inside the cap expands and reliably compresses the strands of the wires. To prevent oxidation when connecting aluminum wires, an anti-oxidation paste is added inside.
WAGO Clamps the wires are compressed under spring force. They do not have screws, they also allow you to connect copper and aluminum wires, they are available for wires of various hardnesses and strands. WAGO clamps differ in the number of applications (disposable and reusable) and in the number of simultaneously switched wires (up to 8). Using these clamps is very simple, you need to:
Wiring inside walls, if insufficiently protected from operational risks, can cause a short circuit or even a fire. If the wiring is old, then it is better to replace it, but new wiring should be done in compliance with all measures to ensure the protection of the electrical cable.
Currently, there is a sufficient choice of tools that provide reliable protection electrical wiring inside the walls. The following products are used for these purposes:
For protection, it is allowed to use steel as well as plastic pipes. The metal pipe (if it is not special) must first be prepared, for which:
Wiring in steel and plastic pipes is well protected from mechanical damage and adverse conditions environment. If only protection from mechanical influences is assumed, then the pipeline is not sealed. To protect against adverse external environmental influences, the pipeline is also sealed. For sealing, seals are used at the junctions of pipes with each other and at the inlets and outlets of distribution boxes and electrical consumers.
When installing electrical wiring in pipes made of metal and plastic, it is necessary to take into account the possibility (if necessary) of removing the wires for their replacement or maintenance. To do this, if there are two or more pipeline bends, the distance between the boxes must be chosen no more than 5 m, and straight sections must be no more than 10 m long.
Minimum cross-sections of copper wires laid in plastic and steel pipes are 1.0 mm², and aluminum – 2.0 mm².
Corrugated plastic pipe made of plastic (“corrugation”) with self-extinguishing, non-flammable material is certified according to the current fire safety rules NPB 246-97. Such a product provides sufficient protection of electrical wiring from mechanical influences and reliably protects fire-hazardous elements of material and wall decoration located near the wire from fires.
This type of protection is easy to install and is not very expensive. “Corrugation” can be laid both inside concrete and stone walls, and inside frames made of wood.
This method of protecting an electrical cable is suitable where there may be significant mechanical and thermal effects on the electrical wiring.
A metal armored hose is a flexible corrugated hose with a plastic tube inside.
The electrical wiring in such a product can be made either unsealed or sealed using seals.
The technology of electrical wiring in wooden houses has its own characteristics. Not only will you need to run a cable from the nearest substation to connect to the network, but the wiring inside the premises must be carried out in compliance with special safety standards.
Wood is the most popular material used in the construction of private housing. Despite its advantages, wood is a fire hazardous and flammable material.
Regardless of the material - brick, gas silicate blocks, concrete, timber, if a fire occurs, the open fire spreads to the furniture and interior decoration of the room. First, everything inside the room burns, and only then the load-bearing walls, partitions and roof begin to burn.
Basic requirements for electrical wiring in wooden buildings:
It is not recommended to independently lay a power cable and install an electrical network without appropriate experience - this should be done by specialists. But every owner of a private home must know the basic rules of electrification. This will allow him to diagnose existing wiring, and will also provide an opportunity to control the quality of work of hired electricians.
Electrical Installation Rules is the main document for electrical wiring design
General requirements and rules for electrical wiring are described in the following documents:
The information contained in these sources is described in technical language and may not be understandable to an unqualified person. At self-study We recommend relying on the “Electrical Installation Rules”, since this document most clearly formulates the meanings and concepts necessary for installing wiring in private homes.
An example of two electrical circuit diagrams in a wooden house
After reviewing the application, the governing body will prepare an agreement and technical conditions necessary for connection to the local electrical network. Then you can begin designing the power supply, which is performed in the following sequence:
When drawing up a project, you should be guided by the PUE. According to this document, electrical wiring is laid strictly in a vertical or horizontal direction. The optimal rotation angle is 90 o.
The socket group, switches and distribution boxes must be located in open areas with free access. Typically, switches are mounted 80–150 cm from the floor level, and a socket or socket group - 50–80 cm. The number of sockets varies from 1 to 6 pieces. The exact quantity depends on the size of the room, but at least one piece per 6m2.
When designing a cable route, it is worth considering that minimum distance from the openings should not be less than 10 cm. If the cable may come into contact with metal elements, then it is retracted 15–30 cm in any convenient direction.
Electrical wire cross-section taking into account the total power of the electrical network
When installing private electrical networks, two types of cables are used: NYM and VVGng. NYM type cable is a power cable that complies with the European standard and is used for laying electrical networks with a rated voltage not exceeding 660 V. VVGng cable is a bare power cable, in double vinyl braid, operating in networks with a constant voltage of no more than 1 kW.
The cable cross-section for laying electrical networks is determined in “mm 2”. For identification, the marking is applied to the cable insulation and is indicated by two numbers. The first number indicates the number of wires inside the single insulation. The second number is the cross-sectional area of the conductor. For example, when an electrician says that you need a three-core copper cable one and a half square, this means NYM cable 3x1.5 mm.
The easiest way to determine the minimum cross-section of a power cable core for a specific section of the network is a special table. This method is proven, as it is used in the design of electrical networks in apartment buildings. The table for selecting the cross-section of the core can be found in the photo above.
As a rule, a copper cable with a cross-section of 2.5–4 mm is used for socket groups, and an aluminum cable with a cross-section of 1.5–2.5 mm is used for lighting. In the case of wooden houses, it is recommended to use only copper wiring, as this will protect the electrical network from overheating.
Wire of various sections for installing electrical wiring in a wooden house
According to the PUE, each section of the electrical network is equipped with a residual current device and a circuit breaker designed for the corresponding current values. To calculate the current strength is used standard formula–I = P/U cosφ, where:
For example, it is necessary to determine the current strength for a section of the network to which household equipment with a total power of 3 kW will be connected. I = 3000 / 220 = 13.64 A. Taking into account a small margin and rounding, it turns out that for this section you will need an RCD and difatomat, designed for rated current 16A.
To determine the type of circuit breaker, it is necessary to calculate the minimum current during a short circuit: I short circuit = 3260 x S/L, where S is the cross-section of the conductor in mm2, L is the length of the conductor in m. As a rule, in networks with a mixed load, which will presented in most private homes, type “C” machines are used.
Sockets are selected taking into account the power of electrical appliances. Typically, these are grounded sockets rated for 16 A current. It is worth remembering that if you plan to use several electrical appliances in a particular room, then it is better to install an outlet group for 2-3 products than to use a “tee” in the future.
On the left is an electric meter, on the left is an RCD with an input cable.
It is optimal if the distribution board is installed in special room from a concrete partition or wall
The technology for installing electrical wiring in a wooden house will consist of several stages: supplying a power cable to the house, installing a distribution board, laying a cable route, connecting contacts and checking functionality.
To carry out the work, you will need to prepare an electric drill with a core attachment, a screwdriver, a Phillips and slotted screwdriver, an indicator screwdriver and protective rubberized gloves.
Distribution board for a private house for 12–24 modules
A distribution board is a device for entering a power cable and distributing incoming electrical energy. Inside the switchboard there is electrical equipment responsible for connection, accounting, safety and correct operation of the power supply system.
Ready-made distribution boards from the manufacturer are a plastic, metal or combined box with a door, DIN rail, neutral and grounding bus. The dimensions of the shield are selected according to the number of modules used. For wooden houses, a panel for 12–15 modules is enough.
Installation of the shield consists of several stages:
When using a shield for 16–24 modules, as a rule, it contains two DIN rails. It is better to install an input machine, a meter and an RCD in the required quantity on the upper guide.
Circuit breakers will be located on the lower DIN rail. This type of module distribution will allow for faster and more convenient connections. After installing all the elements, it is recommended to mark the modules taking into account their group. The sequence of assembling the shield is shown in the video below.
Laying a power cable to a residential building by air
Inserting a power cable into a residential building can be done in two ways: underground and over the air. The first method is more reliable, since an armored cable protected by a corrugated pipe will be used. In this case, the wiring itself will be located under a 30–40 cm layer of earth.
To lay the cable, a trench 70–80 cm deep is dug. A 15–20 cm layer of fine-grained sand is poured onto the bottom of the trench and compacted well. Next, a protective corrugation is laid on the sand cushion, through which the armored cable is passed. Then the corrugated pipe is covered with a 10–15 cm layer of sand. Finally, the pipe is completely buried in the ground.
Laying a power cable to a residential building underground
Cable installation by air is carried out in cases where the distance between the house and the substation is too large. For this purpose, a cable with a supporting cable is used, which is stretched between the supporting and residential buildings. If the distance from the pole to the house exceeds 20 m, then an intermediate support is installed between them.
When entering a power cable through a load-bearing wall, a sleeve made of non-combustible materials is installed at the junction. It is optimal if the cable is inserted in close proximity to the location of the distribution board.
Removing the button and the front part of the socket before installation
Surface-mounted switches and sockets are used both when open and when in a hidden way electrical wiring laying. The technology for installing a switch and socket is similar, so as an example we will take the process of installing a switch from Schneider Electric.
The installation process consists of the following:
Finally, the functionality of the switch is checked and final assembly. The technology for installing a surface-mounted socket is similar. As a rule, a three-core cable is used to connect sockets, so when connecting there is a yellow-green cable (grounding), which is connected to the central terminal.
When installing electrical wiring in a wooden house, the use of “twists” is not allowed. Ideally, part of the cable from the automatic machine to the point of consumption will be made of whole piece wires.
To do this, before cutting the cable, you need to apply markings to the wall surface. Next, using a tape measure, you will need to measure the cable route and only then cut the cable with a margin of 20 cm.
Wago terminal blocks for connecting wiring
If cable connection is unavoidable, then it is better to use:
When installing electrical wiring in a wooden house, we recommend using terminal blocks from Wago. The products are of high build quality and have a wide range of products for cables of various sections. To connect, just strip the cable 10 mm, lift the clamping levers up and insert the cable into the terminal hole.
Covered retro wiring using ceramic sockets and insulators
Opening wiring is the optimal solution for installing electrical wiring in a wooden house. Open way Laying the cable from the distribution panel to the point of consumption has been used for a long time - previously the cable was located on ceramic insulators. Thus, the wiring did not have direct contact with the wooden wall.
Now this technology is called retro wiring and is used in rooms where the total peak power is quite small and does not exceed 4 kW. In residential buildings with high peak loads, this technology has many disadvantages and limitations.
Open wiring in a wooden house without additional insulation
For device open wiring commonly used:
Some homeowners use a combination approach. To lay the cable in straight sections, a straight steel pipe is used, and metal corrugation is used as rotating elements. This approach cannot be called aesthetically attractive, but it is very reliable. For safety reasons, all metal pipes and other elements must be connected to a grounding circuit.
Shutdown alarm with backup power supply
The power outage alarm circuit, Fig. 1, not only emits an audible signal when the power is turned off, but can also turn on a backup power source through an electromagnetic relay. In this alarm circuit, the same intermittent signal generator is used, but in addition to it, the circuit is supplemented with an electromagnetic relay, which is connected with one of the contacts between the diodes VD1 and VD2.
Fig.1
Power outage alarm
If there is voltage in the electrical network, the contacts of this relay are attracted. When the current is lost, capacitor C6 is sharply discharged, causing the voltage at the relay to drop and open the contacts. The presence of diode VD2 in the circuit prevents the rapid discharge of capacitors C1 and C2 through the relay winding.
Automatic protection schemes for a three-phase motor in case of phase loss
Three-phase electric motors, if one of the phases is accidentally disconnected, quickly overheat and fail if they are not disconnected from the network in time. Designed for this purpose various systems automatic protective shutdown devices, but they are either complex or not sensitive enough, Fig. 2
Fig.2
Protective devices can be divided into relay and diode-transistor ones. Relay ones, unlike diode-transistor ones, are easier to manufacture.
An additional relay P with normally open contacts P1 has been introduced into the conventional three-phase motor starting system. If there is voltage in a three-phase network, the winding of the additional relay P is constantly energized and the contacts P1 are closed. When you press the “Start” button, current flows through the electromagnet winding of the MP magnetic starter and the MP1 contact system connects the electric motor to a three-phase network.
If wire A is accidentally disconnected from the network, relay P will be de-energized, contacts P1 will open, disconnecting the winding of the magnetic starter from the network, which, using the MP1 contact system, will disconnect the engine from the network. When wires B to C are disconnected from the network, the winding of the magnetic starter is de-energized. An MKU-48 type AC relay is used as an additional relay P.
Current protection
Household electrical devices- washing machines, electric meat grinders, electric fireplaces, - as a rule, operate from an alternating current network with a voltage of 220 V. In the event of an insulation breakdown on the metal body of such an installation, voltage may be dangerous to human life. To protect against damage electric shock Household appliances should be grounded, especially if they are used in hazardous areas.
Bathrooms pose an increased risk when washing clothes in a washing machine. Moreover, the possibility of electric shock increases significantly if the floor in the room is conductive and the air humidity exceeds 75%.
Most sockets installed in apartments usually do not have a third, grounding wire. Therefore, where it is not available, as a protective measure against possible electric shock in the event of its leakage or insulation breakdown, it is recommended to install automatic disconnecting devices on the housing (Fig. 3).
Fig.3
Electrical energy consumer containing a winding L 1, connect to the network using a bipolar non-polar connector ( regular plugs and sockets). From a rectifier assembled using a bridge circuit using diodes VD 1- VD 4, is powered by relay K1, which has two opening contact pairs K1.1 and K1.2. A thyristor is connected in series with the common relay winding VS 1. Its control electrode is connected through a resistor R 2 with transistor collector VT 1. The emitter of the transistor is connected to the positive pole of the rectifier, and the base is connected through a high-resistance resistor R 1 is connected to the metal body of the electrical device.
The device works as follows. When a working electrical appliance is connected to the network, the relay winding does not receive power because the thyristor is closed. Through the breaking contacts K1.1 and K1.2, the current passes through the consumer winding L 1. In the event of an insulation breakdown, current flows from the phase or “neutral” wire through one of the rectifier diodes, the “emitter-base” transition of the transistor, a resistor R 1, metal case electrical appliance, and then through the place of insulation breakdown and part of the winding L 1 is supplied to the wire with a voltage of opposite polarity. As a result, the transistor opens and current begins to flow in its collector circuit. Through a resistor R 2 it goes to the control electrode of the thyristor and then to the “minus” of the rectifier. The relay is triggered and opens its contact pairs, disconnecting the electrical appliance from the network. At the same time, through the transition “emitter - base” VT 1 current does not flow and the transistor closes. However, the thyristor continues to remain open, since the relay winding plays the role of a smoothing filter, and through VS 1 a direct current flows, the magnitude of which is sufficient to keep the thyristor in the open state. Therefore, after the machine is triggered, the relay remains activated until the electrical appliance is disconnected from the network.
The protective device turns off the electrical installation in the event of an insulation breakdown at any point in the consumer winding L 1. It also works at the slightest leakage current.
Resistor R 1 should have a resistance of 1.5 - 2 MΩ. If you touch a grounded wire with one hand metal object, and the other - to the body household appliance equipped with this protective device, then a current of less than 1 mA passes through a person, which is quite safe. It works right away automatic protection and disconnects the electrical appliance from the network.
To check the operation of the device, the body of the electrical device is briefly connected with a piece of wire to a grounded structure - the relay should operate.
Karachev N.
Power-on protection
Fig.4
In power supplies for powerful equipment on transistors and microcircuits, capacitors with a capacitance exceeding 10,000 μF are usually used in power filters. Transient processes that occur when such equipment is turned on (in particular, the charging of these capacitors) can lead to its failure. For this reason, power supplies, Lately, introduce devices that limit the current in the primary winding of the network transformer at the first moment after turning on the equipment and thereby prevent undesirable effects.
A possible embodiment of such a device is shown in Figure 4. It consists of limiting resistors and a unit that closes these resistors after some time.
The current surge when the equipment is turned on is limited to 5A by resistors R 4- R 7. The use of several resistors here is due only to design considerations. They can be replaced with one resistor with a resistance of 40 Ohms and a power dissipation of at least 20 W, or with another series-parallel combination of resistors connecting, providing the same resistance and power dissipation.
Choosing the value of the limiting resistor is a solution to a contradictory problem. On the one hand, it is desirable to have a large resistance, since overloads in the power supply circuits when the device is turned on and the required power dissipation of this resistor are reduced, but on the other hand, the resistance should not be very large so that the second surge of current that occurs when the limiting resistor is closed is not greater than the initial inrush current when the device is turned on. The parameters of the limiting resistor given here are close to optimal for equipment that consumes 150...200 W of power from the network.
When you turn on the equipment, the charging process of capacitors C2 and C3 begins simultaneously. When the voltage on them reaches the operating voltage of relay K1 and it operates, it will close the resistors with its contacts R 4- R 7 and thereby restore the normal operation of the power source. The delay time for turning on the equipment depends primarily on the capacitance of capacitors C2 and C3, the resistance of the resistor R 3, the response voltage of relay K1 is a fraction of a second.
The device used a relay with an operating voltage of 24 V. It must have contacts that ensure the inclusion of network equipment (220 V and a current of several amperes) with which this protective device will be used.
The bridge used in the original design is designed for an operating voltage of 250 V and a current of 1.5 A. Capacitors C3 and C4 can be replaced with one with a capacity of 1000 μF.
Obvod zpozneneho startu.
"Amaterske Radio", 1997,
A7-8, s.24
Protection of the electric motor from open-phase mode
The open-phase motor protection device, shown in Fig. 5, responds to interruptions in the supply of voltage to a three-phase electric motor from any of the three phases.
Fig.5
By pressing a button S 1, voltage is supplied to the coil of the magnetic starter KM1, which turns on the electric motor M1. Reliable operation of the starter when its coil, designed for 380 V alternating voltage, has a lower amplitude pulsating voltage is ensured due to the significant constant component of the latter.
Simultaneously with the triggering of the starter, voltage is supplied to the anode and control electrode of the thyristor VS 1. Now capacitor C1 is recharged through a periodically opening thyristor, the voltage on it remains sufficient to keep the KM1 starter in the triggered state. In the event of a voltage failure in any of the phases, the thyristor stops opening, the capacitor quickly discharges and the starter disconnects the motor from the network.
Yakovlev V.
Shostka, Ukraine
Emergency switch
Power outages cause a lot of trouble. What is especially bad is that at the moment the voltage is applied there can be very dangerous surges, which, at best, cause failures of the TV processor or DVD - the player by switching them to the on mode, and in the worst case, they damage the power supply.
Fig.6
Figure 6 shows a diagram of an emergency relay, which, when the power supply is turned off, disconnects the equipment from the network. And power is supplied to the equipment not simultaneously with the restoration of power supply, but only after the user presses the button S 1.
The circuit is based on the old KUTS-1 relay from the systems remote control TVs of the "USCT" type.
Electrical equipment protection unit in case of power failures
Many, at least once in their lives, have found themselves in a situation where, instead of a single-phase voltage of 220 V AC, two-phase 380 V suddenly began to flow into their apartments. If such an event was not noticed in the first seconds and the apartment wiring does not have surge protection devices, then all included home appliances fails. The very fact that in a normal situation the potential of the “neutral” wire relative to the “ground” does not exceed a few volts, and in the event of an accident in three-phase final power supply networks reaches 220 V or more, allows us to make a simple device for protecting equipment, the diagram in Fig. 7.
Fig.7
If 220 V plus or minus 30 percent passes through the electric meter, the coil of the powerful electromagnetic relay K1 is de-energized. Through the free-closed contacts of the relay, the loads receive Rated voltage nutrition.
Let’s say an accident occurs and as a result the “neutral wire” turns out to be a phase wire. Since the “Ground” input protective device, assembled according to scheme 1, has a reliable electrical connection with soil, then a voltage of 160...250 V AC will appear on the relay coil, which leads to the opening of its contacts and de-energizing the loads. Back-to-back Zener diodes VD 1, VD 2 eliminate possible slight humming of the relay during normal power supply. Resistor R 1 limits the current through relay coil K1. Neon glow lamp H.L. 1 lights up when there is an accident. Capacitor C1 prevents the occurrence of an arc when the relay contacts open.
Kashkarov A.
A break in the neutral wire in a three-phase electrical network is a dangerous phenomenon that can lead to various negative consequences for household electrical appliances, as well as for the people who operate them. In this article we will consider the consequences of a break in the neutral wire on specific example and appropriate methods for protecting home electrical wiring from ground faults.
Consequences of a broken neutral wire
As an example, consider an apartment building powered by the most common TN-C-S grounding system. This type of system provides for grounding the neutral of the power source - the substation transformer.
From substation to consumer, in in this case electricity enters the house through four conductors - three phase and a conductor that combines the functions of a working neutral and protective grounding conductor.
After entering the building, the combined conductor is divided into a working neutral conductor and a protective conductor, and then distributed between apartments.
The consequences of voltage surges are probably known to everyone. A significant one will lead to the failure of almost all equipment that was currently operating from the network. Excessively low voltage will damage the refrigerator or air conditioner compressor or electric motor in a matter of minutes. washing machine and other electrical appliances that have electric motors. Abnormal operation of electrical appliances may result in their failure and subsequent fire.
Failure household appliances- this is not the worst thing. If the neutral burns out before entering the house, that is, before it is divided into a neutral and grounding conductor, phase voltage appears on all grounded elements of equipment and household electrical appliances. If you touch such electrical appliances, a person will be shocked by electric shock.
In this case, if there is a possible current leak to the grounded body, the RCD will instantly de-energize the electrical wiring. Some types of residual current devices have additional function protection against voltage surges, that is, such a device will combine the functions of two protective devices.
Andrey Povny
