Connecting a private house to a three-phase electrical network - a diagram and important features. What to consider when performing a three-phase connection of a private house Connecting consumers to a three-phase network

Again and again the question arises: what is better for giving and individual residential - three-phase, or single-phase input? And what's so special about three-phase?
Let's figure it out.
First of all, all our networks coming from transformer substations are three-phase. They have four wires - three phase, and zero. If all three phases are brought into the house, this is a three-phase input. If only one leaves, the input is single-phase.
Generally speaking, three-phase has many advantages over single-phase. This is a large transmitted power with the same wire cross-section, and more powerful, reliable and compact electrical consumers, and a more uniform load of networks and transformer substations, and something else.
BUT! There is one very important But! To use the advantages of a three-phase connection, consumers must also be three-phase, designed for such a connection. And now they are not in everyday life. Simply no...
Previously, in Soviet times, people in droves dragged low-power asynchronous three-phase engines from work and, on their basis, made all sorts of circulars, lathes, drilling machines, and much more. It was quite difficult to connect such devices in a conventional single-phase network - maybe the genetic yearning for three phases remained from that time?
Because when connecting single-phase equipment to a technical-phase network, one difficulty arises.
Power related complexity.
And it consists in the following.
Suppose you are allocated 10 kW of three-phase power,
To limit it, you will have a 16A machine at the input.
But do not think that you can plug any single-phase device with a power of 10 kW into the outlet - you can only use 3.5 kW per phase. That is, you cannot use anything more powerful than this value. Moreover, if you use equipment with current surges in starting modes, such as all kinds of electric motors, transformers, etc., then this figure can be safely reduced by another one and a half to two times.
Moreover, when installing electrical networks with your own hands, a mistake is common when all sockets are planted on one phase, lighting on the other, and some kind of technological equipment such as pumps is planted on the third. As a result, one phase turns out to be overloaded in advance, and since the single-phase power for it is almost three times less than the three-phase ... And since at least some selectivity must be ensured, and therefore, willy-nilly, you have to put the machine on the sockets one step less than for input...
Machine guns are starting to kick out.
Here, this is the main problem.
For electricians, three-phase switching of consumers is beneficial. For us, it's the other way around. And if very low power is allowed, such as 6 kW. or less, then 3 phases turn into a disaster. Automatic machines can be knocked out from an ordinary iron or an electric kettle ...

Not every layman understands what electrical circuits are. In apartments, they are 99% single-phase, where the current flows to the consumer through one wire, and returns through another (zero). A three-phase network is a system for transmitting electric current, which flows through three wires with a return one at a time. Here the return wire is not overloaded due to the phase shift of the current. Electricity is generated by a generator driven by an external drive.

An increase in the load in the circuit leads to an increase in the strength of the current passing through the generator windings. As a result, the magnetic field resists the rotation of the drive shaft to a greater extent. The number of revolutions begins to decrease, and gives a command to increase the power of the drive, for example by supplying more fuel to the internal combustion engine. The speed is restored and more electricity is generated.

A three-phase system consists of 3 circuits with EMF of the same frequency and a phase shift of 120 °.

Features of connecting power to a private house

Many people believe that a three-phase network in a house increases power consumption. In fact, the limit is set by the power supply organization and is determined by factors:

supplier capabilities;
the number of consumers;
condition of the line and equipment.

To prevent power surges and phase imbalance, they should be loaded evenly. The calculation of a three-phase system is approximate, since it is impossible to determine exactly which devices will be connected at the moment. The presence of pulsed devices currently leads to increased energy consumption during their start-up.

The distribution switchboard with a three-phase connection is taken larger than with a single-phase supply. Options are possible with the installation of a small inlet shield, and the rest - made of plastic for each phase and for outbuildings.

Connection to the highway is realized by the underground method and by overhead line. Preference is given to the latter due to the small amount of work, low cost of connection and ease of repair.

Now it is convenient to make an air connection using a self-supporting insulated wire (SIP). The minimum cross section of the aluminum core is 16 mm 2, which is enough for a private house with a large margin.

SIP is attached to the supports and the wall of the house using anchor brackets with clamps. The connection to the main overhead line and the input cable to the electrical panel of the house is made with branch piercing clamps. The cable is taken with non-combustible insulation (VVGng) and is led through a metal pipe inserted into the wall.

Air connection of three-phase power at home

At a distance from the nearest support, the installation of another pole is more necessary. This is necessary to reduce loads that lead to sagging or broken wires.

The height of the connection point is 2.75 m and above.

Electrical cabinet

Connection to a three-phase network is carried out according to the project, where consumers are divided into groups inside the house:

lighting;
sockets;
separate powerful devices.

Some loads can be turned off for repair while others are running.

The power of consumers is calculated for each group, where a wire of the required cross section is selected: 1.5 mm 2 - to lighting, 2.5 mm 2 - to sockets and up to 4 mm 2 - to powerful appliances.

The wiring is protected from short circuit and overload by circuit breakers.

Electric meter

For any connection scheme, a metering device is required. A 3-phase meter can be connected directly to the network (direct connection) or through a voltage transformer (semi-indirect), where the meter readings are multiplied by a factor.

It is important to follow the connection order, where odd numbers are power, and even numbers are load. The color of the wires is indicated in the description, and the diagram is placed on the back cover of the device. The input and corresponding output of a 3-phase meter are indicated by the same color. The most common connection order is when the phases go first, and the last wire is zero.

A 3-phase direct connection meter for the home is usually rated for power up to 60 kW.

Before choosing a multi-tariff model, you should coordinate the issue with the power supply company. Modern devices with raters make it possible to calculate the fee for electricity depending on the time of day, register and record power values over time.

The temperature indicators of the devices are chosen as widely as possible. On average, they range from -20 to +50 °С. The service life of the devices reaches 40 years with a calibration interval of 5-10 years.

The meter is connected after the introductory three- or four-pole automatic switch.

Three phase load

Consumers include electric boilers, asynchronous electric motors and other electrical appliances. The advantage of their use is the uniform distribution of the load on each phase. If a three-phase network contains unevenly connected single-phase powerful loads, this can lead to phase imbalance. At the same time, electronic devices begin to malfunction, and the lighting lamps glow dimly.

Scheme of connecting a three-phase motor to a three-phase network

The operation of three-phase electric motors is characterized by high performance and efficiency. It does not require the presence of additional starting devices. For normal operation, it is important to connect the device correctly and follow all recommendations.

The scheme for connecting a three-phase motor to a three-phase network creates a rotating magnetic field with three windings connected by a star or a triangle.

Each method has its own advantages and disadvantages. The star circuit allows you to smoothly start the engine, but its power is reduced to 30%. This loss is absent in the delta circuit, but at start the current load is much greater.

The motors have a connection box where the winding leads are located. If there are three of them, then the circuit is connected only by a star. With six leads, the motor can be connected in any way.

Power consumption

It is important for the owner of the house to know how much energy is consumed. This is easy to calculate for all electrical appliances. Adding all the power and dividing the result by 1000, we get the total consumption, for example 10 kW. For household electrical appliances, one phase is sufficient. However, current consumption increases significantly in a private house, where there is a powerful technique. One device can account for 4-5 kW.

It is important to plan the power consumption of a three-phase network at the design stage in order to ensure symmetry in voltages and currents.

A four-wire wire enters the house for three phases and a neutral. The voltage of the electrical network is Between the phases and the neutral wire, electrical appliances are connected to In addition, there may also be a three-phase load.

The calculation of the power of a three-phase network is carried out in parts. First, it is advisable to calculate purely three-phase loads, such as a 15 kW electric boiler and a 3 kW asynchronous motor. The total power will be P = 15 + 3 = 18 kW. In this case, the current I = Px1000/(√3xUxcosϕ) flows in the phase wire. For household electrical networks cosϕ = 0.95. Substituting numerical values into the formula, we obtain the current value I \u003d 28.79 A.

Now it is necessary to define single-phase loads. Let them be for the phases P A = 1.9 kW, P B = 1.8 kW, P C = 2.2 kW. The mixed load is determined by summation and is 23.9 kW. The maximum current will be I = 10.53 A (phase C). Adding it to the current from a three-phase load, we get I C \u003d 39.32 A. The currents in the remaining phases will be I B \u003d 37.4 kW, I A \u003d 37.88 A.

In calculating the power of a three-phase network, it is convenient to use power tables, taking into account the type of connection.

According to them it is convenient to select circuit breakers and determine the cross-sections of the wiring.

Conclusion

With proper design and maintenance, a three-phase network is ideal for a private home. It allows you to evenly distribute the load across the phases and connect additional power consumers, if the wiring section allows.

The right counter is the main assistant in saving. To make the right choice when buying, the first thing to decide is single-phase or three-phase. But how do they differ, how is the installation and what are the pros and cons of each of them?

In a word - single-phase are suitable for a network with a voltage of 220V, and three-phase - at a voltage of 380V. The first of them - single-phase - are well known to everyone, as they are installed in apartments, office buildings and private garages. But three-phase ones, which were previously used in most cases at enterprises, are increasingly being used in private or country houses. The reason for this was the increase in the number of household electrical appliances that require more powerful power.

The solution was found in the electrification of houses with three-phase cable glands, and to measure the incoming energy, many models of three-phase meters equipped with useful functions were released. Let's deal with everything in order.

Electricity is metered in two-wire AC networks with a voltage of 220V. And three-phase - in networks of alternating three-phase current (3-wire and 4-wire) with a nominal frequency of 50 Hz.

Single-phase power is most often used for the electrification of the private sector, residential areas of cities, office and administrative premises, in which the power consumption is about 10 kW. Accordingly, in this case, electricity is also metered using single-phase meters, the great advantage of which is the simplicity of their design and installation, as well as ease of use (taking phases and readings).

But modern realities are such that over the past couple of decades, the number of electrical appliances and their power has increased significantly. For this reason, not only enterprises, but also residential premises - especially in the private sector - are connected to a three-phase power supply. But does this actually allow more power to be consumed? According to the technical conditions for connection, it turns out that the power supply from a three-phase and single-phase network is almost equal - 15 kW and 10-15 kW, respectively.

The main advantage lies in the ability to directly connect three-phase electrical appliances, such as heaters, electric boilers, asynchronous motors, powerful electric stoves. More precisely, there are two advantages at once. The first is that with a three-phase power supply, these devices operate with higher quality parameters, and the second is that there is no “phase imbalance” when several powerful electrical receivers are used simultaneously, since it is always possible to connect electrical appliances to a phase free from drawdown through “skew”.

The increase in the need for three-phase power has led to an increase in the number of installations of three-phase meters. Compared to single-phase, they have the highest reading accuracy, but also have large dimensions and are more complex, require a three-phase input.

The presence or absence of a neutral wire determines which meter will need to be installed: three-wire in the absence of a “zero”, and if it is present, four-wire. For this, there are corresponding special designations in its marking - 3 or 4. Direct and transformer-connected meters are also distinguished (at currents having 100A or more per phase).

To get a clearer idea of the advantages of single-phase and three-phase meters over each other, you should compare their pros and cons.

Let's start with what loses three-phase to single-phase:

a lot of hassle in connection with the mandatory obtaining of permission to install a meter and the likelihood of a refusal
Dimensions. If before that single-phase power was used with the meter of the same name, you should take care of the place to install the input shield, as well as the three-phase meter itself.

Benefits of three-phase design

Watch a video about the benefits of a three-phase network:

We list the advantages of this type of counters:

Allows you to save. Many three-phase meters are equipped with tariffs, such as day and night, for example. This makes it possible to use up to 50% less energy from 11 pm to 7 am than with a similar load, but in the daytime.
Possibility to choose a model corresponding to specific wishes for the accuracy class. Depending on whether the purchased model is intended for use in a residential area or at an enterprise, there are names with an error of 0.2 to 2.5%;
The event log allows you to notate changes regarding the dynamics of voltage, active and reactive energy and directly broadcast them to a computer or an appropriate communication center;

There are only three types of three-phase meters

Direct connection meters, which, like single-phase ones, are connected directly to a 220 or 380 V network. They have a carrying capacity of up to 60 kW, a maximum current level of not more than 100A, and also provide for the connection of wires of a small cross section of about 15 mm2 (up to 25 mm2)
require connection by means of transformers, therefore, it is suitable for networks of higher power. Before you pay for the consumed energy, you just need to multiply the difference in meter readings (the present with the previous ones) by the transformation ratio.
Counters of indirect inclusion. They are connected exclusively through voltage and current transformers. They are usually installed at large enterprises, as they are designed to account for energy through high-voltage connections.

When it comes to installing any of these meters, there can be a number of difficulties associated with them. After all, if there is a universal circuit for single-phase meters, then for three-phase meters there are several connection schemes for each type at once. Now let's look at this clearly.

Devices for direct, or direct switching

The connection diagram of this meter is in many ways (especially in terms of ease of implementation) similar to the installation diagram of a single-phase meter. It is indicated in the technical data sheet, as well as on the back of the cover. The main condition for connection is strict adherence to the order of connecting wires according to the color indicated in the diagram and the correspondence of odd wire numbers to the input, and even wire numbers to the load.

Wire connection order (listed from left to right):

wire 1: yellow - input, phase A
wire 2: yellow - output, phase A
wire 3: green - input, phase B
wire 4: green - input, phase B
wire 5: red - input, phase C
wire 6: red - output, phase C
wire 7: blue - zero, input
wire 8: blue - zero, output

Semi-indirect counters

This connection takes place via current transformers. There are a large number of schemes for this inclusion, but the most common among them are:

The ten-wire connection scheme is the simplest, and therefore the most popular. To connect, you must follow the order of 11 wires from right to left: the first three are phase A, the second three are phase B, 7-9 for phase C, 10 is neutral.
Connection via terminal box - it is more complicated than the first. The connection is made by means of test blocks;
The star connection, like the previous one, is quite complex, but requires fewer wires. First, the first unipolar outputs of the secondary winding are collected at a common point, and the next three from the other outputs are directed to the meter, the current windings are also connected.

Counters of indirect connection

Such meters for residential premises are not installed, they are intended for operation in industrial enterprises. Installation is the responsibility of qualified electricians.

What device to choose?

Although most often those who want to install a meter are literally informed about which model is required for this and it is very problematic to agree on its replacement, despite its obvious non-compliance with the requirements, it is still worth learning the basics of the criteria that a three-phase meter must meet in terms of its characteristics .

The choice of a meter begins with the question of its connection - through a transformer or directly to the network, which can be determined by the maximum current. Direct connection meters have currents of the order of 5-60 / 10-100 amperes, and semi-indirect - 5-7.5 / 5-10 amperes. Strictly according to these indications, the meter is also selected - if the current is 5-7.5A, then the meter should be similar, but not 5-10A, for example.

Secondly, we pay attention to the presence of a power profile and an internal rater. What does it give? Tarifficator allows the meter to regulate tariff transitions, fix the load schedule for any time period. And the profile - fixes, registers and saves power values for a period of time.

For clarity, consider the characteristics of a three-phase meter using the example of its multi-tariff model:

It should be noted that today three-phase meters for single-phase networks are widespread and vice versa: when three single-phase meters are connected to a three-phase network at once.

The accuracy class is defined in values from 0.2 to 2.5. The larger this value, the greater the percentage error. For residential premises, class 2 is considered the most optimal.

rated frequency value: 50Hz
rated voltage value: V, 3x220/380, 3x100 and others

If, when using an instrument transformer, the secondary voltage is 100V, a meter of the same voltage class (100V) is required, as well as a transformer
the value of the total power consumed by the voltage: 5 VA, and the active power is 2 W

value of rated-maximum current: A, 5-10, 5-50, 5-100
maximum value of total power consumed by current: up to 0.2VA
inclusion: transformer and direct
registration and accounting of active energy

In addition, the range of temperature indicators is important - the wider it is, the better. Average values range from minus 20 to plus 50 degrees.

You should also pay attention to the service life (depending on the model and quality of the meter, but on average it is 20-40 years) and the check interval (5-10 years).

A big plus will be the presence of a built-in electric power modem, with the help of which the indicators are exported via the power network. And the event log allows you to notate changes regarding the dynamics of voltage, active and reactive energy and directly broadcast them to a computer or an appropriate communication center.

And the most important thing. After all, when choosing a counter, we first of all think about saving. So, in order to really save on electricity, you should pay attention to the availability of tariffs. On this basis, meters are single-, double- and multi-tariff.

For example, two-tariff ones consist in a combination of positions “”, continuously replacing each other according to the schedule “7 am -11 am; 11 a.m. -7 a.m., respectively. The cost of electricity at the night rate is 50% lower than the daytime rate, so it makes sense to operate appliances that require a lot of energy (electric ovens, washing machines, dishwashers, etc.) at night.

Practical advice on how to connect a three-phase electricity meter

This type of meter is connected through an introductory three-phase type circuit breaker (containing three or four contacts). It is worth noting right away that replacing it with three single-pole ones is strictly prohibited. The switching of phase wires in three-phase switches must occur simultaneously.

In a three-phase meter, the wire connection is as simple as possible. So, the first two wires are the input and output of the first phase, respectively, similarly, the third and fourth wires correspond to the input and output of the second, and the fifth and sixth correspond to the input and output of the third phase. The seventh wire corresponds to the input of the neutral conductor, and the eighth corresponds to the output of the neutral wire to the energy consumer in the premises.

Grounding is usually assigned to a separate block and is made in the form of a combined PEN wire or PE wire. The best option if there is a division into two wires.

Now let's take a look at the installation of the counter step by step. Let's assume that there is a need to replace a three-phase direct connection meter.

To begin with, we will determine the reason for the replacement and the time of its implementation.

It is preferable to replace the meter during the daytime for the simple reason that the illumination during this period is much better than from the use of a flashlight. This means that it will be more convenient and faster to carry out the work, which cannot but affect your wallet if you have to use the services of a paid electrician.

After that, it is necessary to remove the voltage by changing the position of the switch on the circuit breaker.

After making sure that the phases are removed, we dismantle the old electric meter.

Difficulties that may arise when installing a new meter are related to how different the manufacturers and models of the old and new meters are, and at the same time their shapes and dimensions.

We make a preliminary fitting of a new meter by applying it within the perimeter of contact between the surface (wall) of the mount and the meter housing itself. It is important that the side mounting holes of both of them coincide.

If a preliminary check showed some inconsistencies, we eliminate them by adding suitable mounting holes, extend the wires if the terminals of the new meter are located a little further, etc.

Now, when everything converges, we proceed to the connection. The connection sequence is as follows (from left to right): the first wire is phase A (input), the second is its output; the third is the input, and the fourth is the output of phase B; similarly - the 5th and 6th wires, corresponding to the input and output of phase C, the last two are the input and output of the neutral conductor.

Further installation of the electric meter takes place in accordance with the instructions attached to it.

Among the precautionary measures, which, despite the seriousness of the consequences, should be strictly adhered to, the main place is given to the taboo on any kind of amateur activity - the creation of unforeseen jumpers; actions that may lead to disruption of normal contact, etc. Care must be taken to ensure that the wires are well stretched.

It should be remembered that the connection of the meter can only be carried out by a qualified electrician who is authorized to carry out such work. After the installation is completed, the meter will be sealed by a specialist.

Video about the practice of connecting a three-phase meter

In conclusion - a thesis about the main points

The advantage of single-phase meters is the simplicity of their design and installation, as well as ease of use (taking phase and readings)
But three-phase ones have the highest accuracy of readings, although they are more complicated, have large dimensions and require a three-phase input.
Allows you to save money. thanks to tariffs such as day and night, from 11 pm to 7 am, you can use up to 50% less energy than with a similar load, but in the daytime.
Choice of accuracy class. Depending on whether the purchased model is intended for use in a residential area or in an enterprise, there are names with an error of 0.2 to 2.5%
The event log allows you to notate changes regarding the dynamics of voltage, active and reactive energy and directly broadcast them to a computer or an appropriate communication center
The presence of a built-in electric power modem, with the help of which the indicators are exported via the power network.

I am often asked: “Why did you bring a three-phase line to the house, do you have some kind of special power tool?” No, the most common tool is 220 volts, however, the power sometimes reaches two kilowatts. Well, in fact why do I need three phases in the house? How to connect them without errors?

Theory and practice of connection

First, quite a bit of general information. The supply line can optionally be single-phase, when there are only two wires, or three-phase, when there are four wires, three phase wires and one neutral wire. Generators that generate electricity are so arranged that they have only three coils. Therefore, if you specify power up to 5 kW in the technical conditions, you will be powered from one coil, request more, then immediately from three coils.

How to conduct three phases in a private house? If there is a technical possibility, it is required to request (declare) such a connection. True, on the way from the generator to you there will be a transformer that reduces the high voltage to a household value, so you will get not 380, but native 220. But you will have as many as three phases of 220 volts! In the latter case, three network lines will immediately go from the shield with automatic switches in the house, each having a voltage of 220 volts and a power of 3.5 to 5 kW, depending on the installed machine.

Connection and wiring diagrams, taking into account the presence of three phases, may be different, depending on the needs and the presence of buildings on the site, but the general principles are, of course, the same. Here is my personal version:

Connection diagram for three phases of a private house and outbuildings on the site

By the way, circuit breakers (fuses) are also necessary in the bathhouse and in the utility unit. Installed at the same current as with the central input, they in these buildings, with a faulty load, will work faster due to losses in the supply line.

This winter I already felt advantage of a three-phase connection when the dog Bob, having played enough on the first snow, wrapped in a blanket, warmed himself by the oil radiator in the change house, additionally pointing his muzzle at the heated air coming from the fan heater. It was possible not to be afraid that the fuse would trip from overload when working with a high-powered power tool by connecting to a temporary outlet with a different phase.

Why do you need a temporary outlet?

Well, certainly not because of the dog. When the walls and windows are already in place, there is a roof over your head and a black floor is laid, but only the interior decoration is missing, then it is time for a temporary socket inside the house. And each time it is extremely inconvenient to drag the extension cord out of the change house. Although the socket is called temporary, it must be done like a real one, in accordance with all safety regulations using a circuit breaker.

Determine the phase correctly: color and numbering

To be honest, I didn’t really think about the phases when I once did the wiring in my country house. My father also did not pay attention to this, in those days all the wiring was almost the same, in cracked rubber insulation. However, when I decided to take up the electrification of the economy and assemble a shield for three phases, then, willy-nilly, I learned quite a few facts about the history of electricity in our country.

What color is the phase?

The fact is, in the Soviet Union, the phase wires were yellow, red or green colors. After the disappearance of the Union from the world map, the colors changed to brown, black and gray. However, this fact is absolutely not related to the colors with the symbols of the flags. The fact is that European standards have been adopted with regard to the marking of wires. The last listed color scale is distinguishable for people with visual impairments. But what united us with Europe for quite a long time is that the earth and neutral have always been the same color for us, - yellow green earth And blue (light blue) neutral.

Remembering the last thing neutral wire blue or blue(light blue) and ground green with yellow stripe, we logically understand that the phase will be any other remaining color, we confidently connect the wires for the next generations, regardless of future revolutions and shaking of the world. This is the answer to the question of how to connect three phases.

But in other countries, the marking of the wires is different. When you think about it, it immediately appears to go into the armored car and shout loudly: “Electricians of all camps - unite!”

Why number three phases?

For a single-phase circuit, where there is one phase, it makes no sense. But for a three-phase transmission line, let's number, so to speak, for the future according to the sequence of colors of the cable leading to the house. Pressing against the six-meter ladder and connecting the wires coming out of the hole in the wall of the house with nuts to the air, do not forget to shout:

“The first phase is the brown wire! The second phase is the black wire! The third phase is a gray wire!”

In the same sequence, it is necessary to connect the wires to the built-in circuit breaker. A fat felt-tip pen for numbering will not interfere.

Next to the electrical panel, be sure to hang a picture in a frame with a complete electrical circuit, with the numbering of each circuit breaker, and the color scheme of the wires. I think that the evacuation plan in this case is not required.

Yes, I have not answered the question why numbering is needed. I don't know yet. What if the son buys an electrical appliance exclusively for a three-phase circuit with instructions where the phases are indicated by numbers? That's when you don't have to climb the seven-meter stairs again, having completely forgotten by that time both colors and numbers.

How to connect wires in junction boxes?

The question is really important. Contacts are the most vulnerable point in any electrical circuit. And the issue is resolved for today. how NOT to connect.

We discard all threaded connections. The one who drove domestic cars, and stretched the thread every year, will not argue with me. Under the influence of different temperatures, the bolt and nut will change their linear dimensions, and the connection will weaken, plus a bad coating, and as a result, rust. The end of contact will come quickly. Many still remember heated and melted plugs and sockets.

From the last century, there is still twisting followed by soldering. And in the new century, contacts with springs, for example, from WAGO, are in the first place. Wiring in this case may resemble a game of LEGO. But remember that stranded wire for contact will still have to be twisted and soldered. If I am invited to a barbecue, and while it is cooking, they ask me to help with the electrical wiring, then I will fill all my pockets with spring terminal blocks in advance in order to free myself quickly, otherwise the meat will be eaten without me. And I'm still going to twist myself.

Why do light and power sockets lead from different circuit breakers (fuses)?

There are several answers here. Who will like what ... To choose from:

It is easier to find a malfunction when the chandelier is short-circuited, if it worked on the light, or the electric kettle came to an end, if it worked on the sockets.
In terms of lighting, power consumption is less, especially when using energy-saving lamps, therefore, the automatic device will operate at a lower current and it will work faster without having time to overheat the wires. This condition allows the use of lighting wires with a smaller cross section (0.75 mm), again saving. Yes, and it will be a shame when the time of work on the computer goes to waste, after the light bulb in the chandelier closes, in the case of a common fuse.
We don’t have to look for candles, we won’t stay in complete darkness.

Is there a need for a residual current device (RCD)?

Yes, we will install an RCD and make grounding, without the latter, the first does not work. Euro-class sockets with grounding lamellas. There is a child and a dog. Safety must come first. Now the question is being discussed to put a common RCD on everything, or just on the bathroom. There is still time: the tea is not quite cold :)

P.S. Three phases in a private house really worthwhile thing allowing you to feel more confident and calm. Don't miss out on the added convenience...

So, why do some switchboards get 380 V, and some - 220? Why do some consumers have a three-phase voltage, while others have a single-phase voltage? There was a time when I asked these questions and looked for answers to them. Now I’ll tell you in a popular way, without the formulas and diagrams that textbooks abound in.

In other words. If one phase approaches the consumer, then the consumer is called single-phase, and its supply voltage will be 220 V (phase). If we talk about three-phase voltage, then we are always talking about a voltage of 380 V (linear). Who cares? Further - in more detail.

How are three phases different from one?

In both types of power, there is a working neutral conductor (ZERO). I'm talking about protective grounding, this is a vast topic. In relation to zero in all three phases - the voltage is 220 volts. But in relation to these three phases to each other - they have 380 volts.

Voltages in a three-phase system

This happens because the voltages (with active load, and current) on the three phase wires differ by a third of the cycle, i.e. 120°.

More details can be found in the textbook of electrical engineering - about voltage and current in a three-phase network, as well as see vector diagrams.

It turns out that if we have a three-phase voltage, then we have three phase voltages of 220 V each. And single-phase consumers (and there are almost 100% of them in our homes) can be connected to any phase and zero. It is only necessary to do this in such a way that the consumption for each phase is approximately the same, otherwise phase imbalance is possible.

In addition, it will be difficult and insulting for the overly loaded phase that others are “resting”)

Advantages and disadvantages

Both power systems have their pros and cons, which change places or become insignificant when the power passes through the 10 kW threshold. I'll try to list.

Single-phase network 220 V, pluses

Simplicity
Cheapness
Below dangerous voltage

Single-phase network 220 V, minuses

Limited consumer power

Three-phase network 380 V, pluses

Power is limited only by the cross section of the wires
Savings with three-phase consumption
Power supply for industrial equipment
Ability to switch a single-phase load to a “good” phase in case of deterioration in quality or power failure

Three-phase network 380 V, minuses

More expensive equipment
More dangerous voltage
The maximum power of single-phase loads is limited

When is 380 and when is 220?

So why is the voltage in our apartments 220 V, and not 380? The fact is that, as a rule, one phase is connected to consumers with a power of less than 10 kW. And this means that one phase and a neutral (zero) conductor are introduced into the house. In 99% of apartments and houses, this is exactly what happens.

Single-phase electrical panel in the house. The right automaton is introductory, then - through the rooms. Who will find errors in the photo? Although, this shield is one big mistake ...

However, if you plan to consume more than 10 kW of power, then a three-phase input is better. And if there is equipment with a three-phase power supply (containing), then I strongly recommend bringing a three-phase input with a linear voltage of 380 V into the house. This will save on wire cross-section, on safety, and on electricity.

Despite the fact that there are ways to include a three-phase load in a single-phase network, such alterations drastically reduce the efficiency of motors, and sometimes, other things being equal, you can pay 2 times more for 220 V than for 380.

Single-phase voltage is used in the private sector, where the power consumption, as a rule, does not exceed 10 kW. At the same time, a cable with wires with a cross section of 4-6 mm² is used at the input. The consumed current is limited by the introductory circuit breaker, the rated protection current of which is not more than 40 A.

About the choice of a circuit breaker, I already. And about the choice of wire section -. There are also heated discussions.

But if the consumer's power is 15 kW and above, then it is imperative to use a three-phase power supply. Even if there are no three-phase consumers in this building, for example, electric motors. In this case, the power is divided into phases, and the electrical equipment (input cable, switching) is not subjected to the same load as if the same power was taken from one phase.

For example, 15 kW is about 70A for one phase, you need a copper wire with a cross section of at least 10 mm². The cost of a cable with such cores will be significant. And I have not seen automatic machines for one phase (single-pole) for a current of more than 63 A on a DIN rail.

Therefore, in offices, shops, and even more so in enterprises, only three-phase power is used. And, accordingly, three-phase meters, which are of direct connection and transformer connection (with current transformers).

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And on the input (in front of the counter) there are approximately such “boxes”:

Three-phase input. Introductory machine in front of the counter.

A significant minus of a three-phase input and (marked it above) - the power limit of single-phase loads. For example, the allocated power of a three-phase voltage is 15 kW. This means that for each phase - a maximum of 5 kW. And this means that the maximum current for each phase is no more than 22 A (practically - 25). And you have to spin, distributing the load.

I hope now it is clear what is a three-phase voltage of 380 V and a single-phase voltage of 220 V?

Star and Delta schemes in a three-phase network

There are various variations of switching on the load with an operating voltage of 220 and 380 Volts in a three-phase network. These schemes are called "Star" and "Triangle".

When the load is designed for a voltage of 220V, it is connected to a three-phase network according to the “Star” scheme, that is, to the phase voltage. In this case, all load groups are distributed so that the phase powers are approximately the same. The zeros of all groups are connected together and connected to the neutral wire of the three-phase input.

All our apartments and houses with single-phase input are connected to Zvezda, another example is the connection of heating elements in powerful and.

When the load voltage is 380V, it is switched on according to the “Triangle” scheme, that is, to the linear voltage. This phase distribution is most typical for electric motors and other loads, where all three parts of the load belong to a single device.

Power distribution system

Initially, the voltage is always three-phase. By “originally” I mean a generator at a power plant (thermal, gas, nuclear), from which a voltage of many thousands of volts is supplied to step-down transformers, which form several voltage steps. The last transformer lowers the voltage to a level of 0.4 kV and supplies it to end consumers - to us, to apartment buildings and to the private residential sector.

Further, the voltage is supplied to the transformer TP2 of the second stage, at the output of which the voltage of the end consumer is 0.4 kV (380V). Power transformers TP2 - from hundreds to thousands of kW. From TP2, voltage is supplied to us - to several apartment buildings, to the private sector, etc.

The scheme is simplified, there may be several steps, voltages and powers may be different, but the essence of this does not change. Only the final voltage of consumers is one - 380 V.