Selection of wire section

The design of any household or industrial electrical networks must begin with the calculation of a suitable cross-section for an electrical wire , a great deal depends on this parameter, and first of all, the reliability and efficiency of your electrical network. How well the grid is calculated and how correctly the wire section is selected according to these calculations, the power losses in the projected network depend, which are quite significant if you choose the wrong section for the wire. In addition, there is a possibility of overheating of the wires and their destruction if the section is not chosen correctly.

The main criteria that are taken into account during the design and selection of the cross section are the magnitude of the current load , the network voltage, and the power of the electrical consumer . The design of the power grid and the choice of wires always begins with determining the properties of the electrical equipment that will be in this network and consume electricity. If there are several electricity consumers on a network site, then their capacities are added to select a wire section for a given section. After determining the power consumption of electricity for each section of the projected network, calculate the permissible current load. To calculate the load, the duration of which is directly dependent on the choice of section, a simplified formula is used in which the network voltage and power consumption for a given network section are located.

After calculating the current load and determining its duration, it is necessary to ascertain the conditions under which the power grid, temperature and method of laying the electrical network (open or closed) will be used.

After the permissible current and time of the load have been calculated, the conditions of operation and the installation of the power grid have been taken into account, the choice of wire cross-section can be started. The choice of cables and wires of the power grid is carried out according to the tables of long-term permissible load current, where the method of laying cables and network wires is also taken into account. Of course, it is quite difficult to choose a wire or cable that exactly matches the calculated load current, in such cases, the cable or wire section is always taken with a margin.

For those interested in improving the theoretical knowledge of electrical work, we provide a table of wire cross section selection depending on the current and power characteristics of equipment with which the design and electrical installation begins. The cross section of the wire is determined from the permissible continuous loads, simplified formula:

I = P ⁄ U × √3,

where I is alternating current, A; P - power of the consumer of electricity, W; U - voltage, V.

Selection of cable cross-section with copper conductors for the power of the connected load

Electrical wiring must meet safety, reliability and cost-effectiveness requirements. Therefore, it is important to correctly calculate the length and cross-section of the electrical wiring required for the installation.

The length of the wire is calculated according to the wiring diagram. To do this, the diagram measures the distances between their neighbors, the locations of the guards, receptacles, switches, junction boxes, etc. Then, using the scale in which the circuit is drawn, calculate the length of the wires; At least 100 mm is added to the length of each segment (the need to connect wires is taken into account). The length of the wire can also be calculated by measuring directly on shields, panels, walls, ceilings, etc., from cutting lines along which wires must be laid.

The wire cross section is calculated from the voltage loss and the permissible continuous current load. If the calculated cross sections are not equal, then the final result is taken as the value of more than the cross section.

The voltage loss is due to the voltage drop in the wires connecting the current source to the receiver. It should not exceed 2–5% of the rated voltage of the power supply. The loss of voltage is calculated in the design of electrical networks, from which electrical receivers of industrial enterprises, transport, large residential and public buildings, etc., are powered.

When designing small electrical installations, for example, electrical installations of individual premises, self-made devices, etc., the loss of voltage in the wires can be neglected, since it is very small.

To calculate the cross-section of wires for the permissible long-term current load, it is necessary to know the rated current that must pass through the designed electrical wiring. Knowing the rated current, the wire cross section is found by the table.