Electric cable power by cross-section table. Anyone can calculate the wire cross-section

Wire power table it is required to correctly calculate the cross-section of the wire; if the power of the equipment is large and the cross-section of the wire is small, then it will heat up, which will lead to the destruction of the insulation and loss of its properties.

For the transmission and distribution of electric current, the main means are wires; they ensure the normal operation of everything related to electric current, and how good this work will be depends on the right choice wire cross-sectionby power. A convenient table will help you make the necessary selection:

Current cross-section conductive lived mm
	Voltage 220V		Voltage 380V
	Current. A	Power. kW	Current. A	Power, kWt

Section Toko- conductive lived mm	Aluminum conductors cables and wires
	Voltage 220V		Voltage 380V
	Current. A	Power. kW	Current. A	Power, kWt

But in order to use the table, you need to calculate the total power consumption of the devices and equipment that are used in the house, apartment or other place where the wire will be laid.

Example of power calculation.

Let's say that a closed electrical wiring of explosive wires is being installed in a house. You need to write down a list of equipment used on a piece of paper.

But how now find out power? You can find it on the equipment itself, where there is usually a label with the main characteristics recorded.

Power is measured in Watts (W, W) or Kilowatts (kW, KW). Now you need to write down the data and then add it up.

The resulting number is, for example, 20,000 W, which would be 20 kW. This figure shows how much energy all electrical receivers together consume. Next, you should consider how many devices will be used simultaneously over a long period of time. Let’s say it turns out to be 80%, in which case the simultaneity coefficient will be equal to 0.8. We calculate the wire cross-section based on power:

20 x 0.8 = 16 (kW)

To select a cross-section, you will need a wire power table:

Current cross-section conductive lived mm	Copper conductors of cables and wires
	Voltage 220V		Voltage 380V
	Current. A	Power. kW	Current. A	Power, kWt
10		15.4

If the three-phase circuit is 380 Volts, then the table will look like this:

Current cross-section conductive lived mm	Copper conductors of cables and wires
	Voltage 220V		Voltage 380V
	Current. A	Power. kW	Current. A	Power, kWt
				16.5
10		15.4

These calculations are not particularly difficult, but it is recommended to choose a wire or cable with the largest cross-section of conductors, because it may be that it will be necessary to connect some other device.

Additional wire power table.

Hello. The topic of today's article is “ Cable cross-section by power". This information will be useful both at home and at work. We will talk about how to calculate the cable cross-section by power and make a choice using a convenient table.

Why is it even necessary? choose the correct cable section?

In simple terms, this is necessary for the normal operation of everything related to electric current. Be it a hair dryer, washing machine, motor or transformer. Today, innovations have not yet reached the wireless transmission of electricity (I think they will not reach it soon); therefore, the main means for transmitting and distributing electric current are cables and wires.

With a small cable cross-section and high power equipment, the cable can heat up, which leads to loss of its properties and destruction of the insulation. This is not good, so correct calculation is necessary.

So, selection of cable cross-section by power. For selection we will use a convenient table:

The table is simple, I don’t think it’s worth describing it.

Let's say we have a house, we are installing closed electrical wiring using a VVG cable. Take a sheet of paper and copy down the list of equipment used. Done? Fine.

How to find out power? You can find the power on the equipment itself; there is usually a tag where the main characteristics are written down:

Power is measured in Watts (W, W), or Kilowatts (kW, KW). Found it? We record the data, then add it up.

Let's say you get 20,000 W, that's 20 kW. The figure tells us how much energy all electrical receivers consume together. Now you need to think about how many devices you will use simultaneously over a long period of time? Let's say 80%. The simultaneity coefficient in this case is 0.8. Let's do calculation of cable cross-section by power:

We count: 20 x 0.8 = 16(kW)

To do selection of cable cross-section according to power, look at our tables:

In order to correctly lay the electrical wiring, ensure uninterrupted operation of the entire electrical system and eliminate the risk of fire, before purchasing a cable, it is necessary to calculate the loads on the cable to determine the required cross-section.

There are several types of loads, and for the highest quality installation of the electrical system, it is necessary to calculate the loads on the cable according to all indicators. The cable cross-section is determined by load, power, current and voltage.

Power section calculation

In order to produce, it is necessary to add up all the indicators of electrical equipment operating in the apartment. Calculation of electrical loads on the cable is carried out only after this operation.

Calculation of cable cross-section by voltage

Calculation of electrical loads on a wire necessarily includes. There are several types of electrical network - single-phase at 220 volts, and three-phase at 380 volts. In apartments and residential premises, as a rule, a single-phase network is used, so during the calculation process it is necessary to take this point into account - the voltage must be indicated in the tables for calculating the cross-section.

Calculation of cable cross-section by load

Table 1. Installed power (kW) for cables laid openly

Core cross-section, mm 2	Cables with copper conductors		Cables with aluminum conductors
	220 V	380 V	220 V	380 V
0,5	2,4
0,75	3,3
1	3,7	6,4
1,5	5	8,7
2	5,7	9,8	4,6	7,9
2,5	6,6	11	5,2	9,1
4	9	15	7	12
5	11	19	8,5	14
10	17	30	13	22
16	22	38	16	28
25	30	53	23	39
35	37	64	28	49

Table 2. Installed power (kW) for cables laid in a groove or pipe

Core cross-section, mm 2	Cables with copper conductors		Cables with aluminum conductors
	220 V	380 V	220 V	380 V
0,5
0,75
1	3	5,3
1,5	3,3	5,7
2	4,1	7,2	3	5,3
2,5	4,6	7,9	3,5	6
4	5,9	10	4,6	7,9
5	7,4	12	5,7	9,8
10	11	19	8,3	14
16	17	30	12	20
25	22	38	14	24
35	29	51	16

Each electrical appliance installed in the house has a certain power - this indicator is indicated on the nameplates of the devices or in the technical data sheet of the equipment. To implement, it is necessary to calculate the total power. When calculating the cable cross-section for the load, it is necessary to rewrite all electrical equipment, and you also need to think about what equipment may be added in the future. Since the installation is carried out for a long time, it is necessary to take care of this issue so that a sharp increase in load does not lead to an emergency.

For example, you have a total voltage of 15,000 W. Since the vast majority of residential premises have a voltage of 220 V, we will calculate the power supply system taking into account a single-phase load.

Next, you need to consider how much equipment can operate simultaneously. As a result, you will get a significant figure: 15,000 (W) x 0.7 (70% simultaneity factor) = 10,500 W (or 10.5 kW) - the cable must be designed for this load.

You also need to determine what material the cable cores will be made of, since different metals have different conductive properties. In residential premises, copper cable is mainly used, since its conductive properties are much higher than those of aluminum.

It is worth considering that the cable must have three cores, since grounding is required for the electrical supply system in the premises. In addition, it is necessary to determine what type of installation you will use - open or hidden (under plaster or in pipes), since the calculation of the cable cross-section also depends on this. Once you have decided on the load, core material and type of installation, you can look at the required cable cross-section in the table.

Calculation of cable cross-section for current

First you need to calculate the electrical loads on the cable and find out the power. Let's say that the power turned out to be 4.75 kW, we decided to use a copper cable (wire) and lay it in a cable channel. is produced according to the formula I = W/U, where W is power, and U is voltage, which is 220 V. In accordance with this formula, 4750/220 = 21.6 A. Next, look at table 3, we get 2, 5 mm.

Table 3. Permissible current loads for cables with copper conductors laid hidden

Core cross-section, mm	Copper conductors, wires and cables
	Voltage 220 V	Voltage 380 V
1,5	19	16
2,5	27	25
4	38	30
6	46	40
10	70	50
16	85	75
25	115	90
35	135	115
50	175	145
70	215	180
95	260	220
120	300	260

Using the PUE table, you can select the correct cable cross-section for current. So, for example, if the cable is of a smaller cross-section, this can lead to premature failure of the entire wiring system or damage to the included equipment. Also, an incorrect choice of cable thickness can cause a fire, which will occur due to melting of the wire insulation when it overheats due to high power.

In the reverse process, when the cable thickness is taken with a significant power reserve, there may be an unnecessary waste of money to purchase a more expensive wire.

As practice shows, in most cases the current cable cross-section should be selected based on its density.

PUE and GOST tables

Current Density

When choosing a wire cross-section, you need to know some indicators. So, for example, the current density in a material such as copper ranges from 6 to 10 A/mm2. This indicator is the result of many years of experience by specialists and is adopted based on the basic rules governing the design of electrical installations.

In the first case, with a density of six units, the electrical network is provided for long-term operation. If the indicator is ten units, then it should be understood that network operation is not possible for a long time during periodic short turns on.

Therefore, it is necessary to select the thickness precisely according to this permissible indicator.

The above data is for copper cable. Aluminum wires are still used in many electrical networks. At the same time, copper cable has its undeniable advantages in comparison with the latter type of wire.

These include the following:

1. Copper cable has much greater softness and at the same time its strength is higher.
2. Products made from copper are not subject to oxidation processes for a longer period of time.
3. Perhaps the most important indicator of a copper cable is its higher degree of conductivity, and therefore a better indicator of current density and power.

Our readers recommend! To save on electricity bills, our readers recommend the ‘Electricity Saving Box’. Monthly payments will be 30-50% less than they were before using the saver. It removes the reactive component from the network, resulting in a reduction in load and, as a consequence, current consumption. Electrical appliances consume less electricity and costs are reduced.

The most important disadvantage of such a cable is its higher price.

The current density indicator for aluminum wire is in the range from four to six A/mm2. Therefore, it can be used in less critical structures. This type of wiring was also actively used in the last century in the construction of residential buildings.

Carrying out current cross-section calculations

When calculating the working indicator of cable thickness, it is necessary to know what current will flow through the network of a given room. For example, in the most ordinary apartment it is necessary to sum up the power of all electrical appliances that are connected to the network.

As an example for calculation, we can give a standard table of power consumption by the main household appliances used in an ordinary apartment.

Based on the total power, the current that will flow through the network cables is calculated.

In this formula, P means the total power, measured in Watts, K1 is the coefficient that determines the simultaneous operation of all household appliances (its value is usually 0.75) and U is the voltage in the home network, usually equal to 220 Volts.

This current calculation indicator will help to estimate the required cross-section for the general network. In this case, it is also necessary to take into account the operating current density.

This calculation can be taken as an approximate choice. In this case, more accurate indicators can be obtained using a selection from a special PUE table. This PUE table is an element of special rules for the design of electrical installations.

Below is an example of a PUE table that can be used to select a section.

As you can see, such a PUE table, in addition to the dependence of cross-sections on the current indicator, also provides for taking into account the material from which the wires are made, as well as its location. In addition, the table regulates the number of cores and the voltage value, which can be either 220 or 380 Volts.

Current calculation using additional parameters

When calculating the cross section based on current using the PUE table, you can also use additional parameters.

For example, it is possible to take into account the core diameter. Therefore, when determining the cross-section of the conductor, special equipment called a micrometer is used. Based on its data, the thickness of each core is determined. Then, using the values ​​of previously obtained currents and a special table, the final selection of the cross-sectional value of the wire core is made.

If the cable consists of several cores, then you should measure one of them and calculate its cross-section. After this, to find the final thickness value, the indicator obtained for one core is multiplied by their number in the wire.

The value of the cable cross-section obtained in this way using calculations and the PUE table will allow you to create wiring in a house or apartment that will serve the owners for quite a long period of time without the occurrence of emergency or emergency situations.

Electricity can be generated by a generator at voltages of 6, 10, 18 kV. Then it goes along busbars or complete busbars to transformers, which increase this value to 35-330 kV. The higher the voltage, the further this energy is transmitted. Then the electricity travels through power lines to consumers. There it is again transformed through step-down transformers to a value of 0.4 kV. And between all these transformations, electricity flows through overhead and cable lines of various voltages. The choice of the cross-section of these cables is a separate issue, which is discussed in this article.

If we turn to the basics of the question, it can immediately be divided into two parts. Part one, choosing a cross-section in networks up to 1 kV, and the second part (in a separate article) - choosing a cross-section in networks above 1 kV. In addition, we will consider a common issue for these voltage classes - determining the cable cross-section by diameter. I warn you right away that there are a lot of tables ahead, but don’t let this scare you, because sometimes a table is worth a thousand words.

Selection and calculation of cable cross-sections for voltages up to 1 kV (for apartments, houses)

Electrical networks up to 1 kV are the most numerous - it’s like a web that wraps around the entire electrical power industry and in which there are such countless machines, circuits and devices that an unprepared person’s head can go spinning. In addition to 0.4 kV networks of industrial enterprises (factories, thermal power plants), these networks also include wiring in apartments and cottages. Therefore, the question of choosing and calculating the cable cross-section is also asked by people who are far from electricity - ordinary property owners.

The cable is used to transmit electricity from source to consumer. In apartments, we consider the area from the electrical panel, where the input circuit breaker for the apartment is installed, to the area into which our appliances are connected (TVs, washing machines, kettles). Anything that moves away from the machine away from the apartment in the department of the service organization, we have no right to go there. That is, we are considering the issue of laying cables from the input machine to sockets in the wall and switches on the ceiling.

In general, 1.5 square meters are taken for lighting, 2.5 for sockets, and calculation is necessary if you need to connect something non-standard with high power - a washing machine, boiler, heating element, stove.

Selection of cable cross-section by power

I will further consider an apartment, since the people at the enterprises are literate and know everything. To estimate the power, you need to know the power of each electrical receiver and add them together. The only disadvantage when choosing a cable with a larger cross-section than necessary is economic infeasibility. Since a larger cable costs more, but heats up less. And if you choose correctly, it will be cheaper and will not heat up much. You cannot round down, since the cable will heat up more due to the current flowing in it and will quickly fall into a faulty state, which can lead to a malfunction of the electrical appliance and all wiring.

The first step when choosing a cable cross-section will be to determine the power of the loads connected to it, as well as the nature of the load - single-phase, three-phase. Three-phase it can be a stove in an apartment or a machine in a garage in a private house.

If all devices have already been purchased, then you can find out the power of each one from the passport that comes with the kit, or, knowing the type, you can find the passport on the Internet and see the power there.

If you have not purchased the devices, but you plan to buy them, then you can use the table where the most popular devices are listed. We write down the power values ​​and add up those values ​​that can be plugged into one outlet at the same time. The values ​​given below are for reference only; when calculating, the larger value should be taken (if the power range is indicated). And it’s always better to look at your passport than to take averages from tables.

It is convenient to divide the switches that come after the introductory one into groups. Separate switches for powering the stove, washing machine, boiler and other powerful appliances. Separate for powering the lighting of individual rooms, separate for groups of sockets in rooms. But this is ideal, in reality there is just an introductory one and three machines. But I got distracted...

Knowing the value of the power that will be connected to a given outlet, we select the cross section from the table, rounded up.

I will take tables 1.3.4-1.3.5 from the 7th edition of the PUE as a basis. These tables are given for wires, aluminum or copper cords with rubber and (or) PVC insulation. That is, what we use in home wiring - copper NYM and VVG, beloved by electricians, and aluminum AVVG are suitable for this type.

In addition to the tables, we will need two formulas for active power: for single-phase (P=U*I*cosf) and three-phase networks (the same formula, only multiplied by the root of three, which is equal to 1.732). We take the cosine to be one, we will have it as a reserve.

Although there are tables where for each type of socket (socket for a machine, socket for this, for that) its own cosine is described. But it cannot be greater than one, so it’s not scary if we take it to be 1.

Even before looking at the table, it is worth deciding how and in what quantity our wires will be laid. The options are as follows - open or in a pipe. And in a pipe you can have two or three or four single-core, one three-core or one two-core. For an apartment, we have a choice of either two single-core in a pipe - this is 220V, or four single-core in a pipe - 380V. When laying in a pipe, it is necessary that 40 percent of free space remains in this very pipe, this is to avoid overheating. If you need to lay wires in a different quantity or in a different way, then feel free to open the PUE and recalculate for yourself, or choose not by power, but by current, which will be discussed a little later in this article.

You can choose either copper or aluminum cable. Although, recently copper has become more widely used, since a smaller cross-section is required for the same power. In addition, copper has better electrical conductive properties, mechanical strength, is less susceptible to oxidation, and in addition, the service life of copper wire is longer compared to.

Have you decided whether it’s copper or aluminum, 220 or 380V? Well, let's look at the table and select a section. But we take into account that in the table we show values ​​​​for two or four single-core wires in a pipe.

We calculated the load, for example, at 6 kW for a 220V socket and look at 5.9, although it’s close, we choose 8.3 kW - 4mm2 for copper. And if you decide on aluminum, then 6.1 kW is also 4 mm2. Although it is worth choosing copper, since the current with the same cross-section will be 10A more permissible.

Selecting cable cross-section for current

The essence of the choice is similar, only now we have a PUE where the currents are registered, but the currents themselves are unknown to us. Although, wait... After all, we know the power of the devices and can calculate the current values ​​using the formula. Yes, and currents can be written in product passports. We look similarly at the tables below. These are already tables from official documents, so there’s nothing to complain about.

Selecting the cross-section of a wire with rubber or PVC insulation based on permissible current

These wires are the most common, which is why this table is shown. In the PUE there are other tables for all occasions for wires, cables, cords with and without sheathing when laid in water, land and air. But these are special cases. By the way, the table given for power calculations is completely a special case of current selection tables, which are official and described in the PUE.

Cable calculation by power and length

If you are laying a cable over a long distance (well, 15 meters or more), then you need to take into account the voltage drop, which is caused by the resistance of the cable line.

Why is the voltage drop at the end of the cable line unfavorable for us? For a light bulb, this is a deterioration in luminous flux when the voltage decreases, or a decrease in service life when the voltage increases. There are acceptable voltage deviation values. But basically for electrical appliances it is plus or minus five percent.

In this case, it is necessary to make a calculation, and if the voltage is below the nominal voltage by 5% or more, you will have to increase the cross-section and re-calculate. Or use another table.

Now let's go a little deeper into the hardware. The voltage drop for a three-phase network is determined by the formula:

This quantity consists of two parts, active (R) and inductive (X). The inductive part can be neglected in the following cases:

• DC network
• AC mains, at cos=1
• networks made with cables or insulated wires laid in pipes, if their cross-section is not larger than a certain size, but we will not go deeper.

In general, we neglect the inductive component and take the cosine equal to 1. The value of R is determined by the formula:

where p is the resistivity (for - 0.0175, and for aluminum - 0.03)

a) based on the given value of the voltage drop, we find the permissible cross-section and select the next larger value.

b) using a given value of power or current, we determine the voltage drop in the section, and if it is more than 5%, we select another section and repeat the calculation.

In the above formulas, the length is in meters, the current is in amperes, the voltage is in volts, and the area is in mm2. The magnitude of the voltage drop itself is in relative values, dimensionless. The formulas are suitable for calculations in the absence of an inductive component and a cosine equal to 1. A number of cable cross-sections are standard. In principle, with the obtained cross-section value, you can go to the market and see what is suitable, rounded up.

Or you can use tables on the Internet, but these tables... It’s not clear where they came from and for what purpose they were built. Formulas are our everything!

Determination of cable cross-section by diameter

If you have the opportunity to measure the diameter of a cable core, naturally bare, without insulation, then you can determine the cross-section of this core. Again we have two options: a formula or a table. Let everyone choose what is more convenient for them.

Formula: pide square four. Everyone knows this. We measure the diameter of the wire (ruler, caliper, micrometer), again, cleaned. We square the value, multiply by pi (equal to 3.14) and divide by 4. We obtain the cross-section value. Approximate, because there are errors both in the number pi and in the measurement itself. Would you like, here is a simple table - measure the diameter, see if it corresponds to the cross-section stated on the tag.

If the wire is multi-core, then we either measure each wire, and then count their number. Well, we multiply the number by the diameter of one and then follow the scheme given above. Or, if they are well twisted in the shape of a circle at the end, we measure as on a single-core one.

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