How to check the current cable cross section and why do we need to do?

  • Dec 26, 2019

In a modern house uses a lot of different equipment connected to the electrical network, which has become a must in the same infrastructure components as water, sanitation and ventilation. Like the rest of the engineering system wiring is worn during use and must be replaced when performing repairs.

To restore its linear part of the need for a new cable. When buying usually oriented to the desired cross section of conductors (TPG) and the selected item, the price of which is minimal.

Ceteris paribus cheaper cable enjoys increasing popularity among consumers. However, at the present time can not be 100 percent sure that this cable is just as high quality as it is more expensive counterpart.

This is because the lion's share of the selling price of this product is copper veins. Therefore, some dishonest manufacturers in an effort to increase the volume of sales lower selling prices understatement section TPG, "forgetting" at the same time change the marking.

How can protect yourself from buying low-quality goods? Fortunately, check conformity of the true cross section of the labeling lived quite simply, even at home, and it can be done in two ways.


When performing further actions proceed from the following:

  • Power cable conductors have a circular cross-section (there are cables with the conductors different shapes, but they are not used in everyday life);
  • diameter D core measure is much more convenient than the area;
  • standardized marking cables based on TPG area, e.g. VVGng-2x2.5 indicates an area of ​​2.5 mm2.

To convert the measured diameter D in cross-section it is advisable to use the relation:

S = 0,79*D2. author's Note: D Here in the square (Zen editor does not allow the degree / output indices)

Check caliper and micrometer

The most accurate results are obtained by measuring the micrometer, caliper application for this slightly increases the error.

to find D perform the following procedure:

  • TPG with insulation removed;
  • TPG measured diameter as shown in Figure 1;
  • Measurement was repeated three to five times at a distance of about 5 mm from each other, (preferably) in different planes, ie the tool is applied to the wire at different angles;
  • the obtained values ​​are averaged;
  • sectional area is calculated and compared with the marking.
  • at understating the true value by more than 10% of the cable is rejected.
Picture 1. Measurement micrometer core diameter
Picture 1. Measurement micrometer core diameter

Check with a ruler

In the absence of a caliper and micrometer proceed as follows:

  • TPG free from insulation over a length of 15 - 20 cm;
  • straightened wire and tightly wind the coil to a coil conductor on any suitable subject with a constant cross-section along the length (e.g., a pencil or screwdriver) cm. Figure 2;
  • count the number of revolutions (it is advisable that they were not less than ten) and measure the length of the resulting helix.
  • divide the value of the length in number of turns to obtain D.
Comment. School lines often give an error of up to 10-15%, so when in doubt its accuracy is better to use a tape measure.
Figure 2. The peculiarity measurement ruler core diameter
Figure 2. The peculiarity measurement ruler core diameter

Features Measurement of flexible cables with stranded TPG

When working with the flexible cables (example shown in Figure 3) Any of the above procedures was measured diameter of one wire. Then:

  • counting section;
  • the obtained result is multiplied by the number of wires in the core (to be 7 or 19, larger values ​​are rare).
Figure 3. Different species of flexible stranded lived
Figure 3. Different species of flexible stranded lived


The procedure for determining the true cross section of the power cable lived quite simple and does not require the use of complex instruments. The only problem is that it is inconvenient to perform directly in the store. In this situation, we can recommend to make checks in a relaxed home environment in the first test bay or to buy cable only reliable manufacturers.