Why is the cable cross-section so important?

One of the most frequently asked questions in electrical installation is: Which values have an influence on the cable cross-section to be selected? In addition to the voltage, the amount of current to be conducted and the power, the length of the cable must also be taken into account when selecting the appropriate cable cross-section. You can find more information on the topic of current/voltage in our guide article "How is electrical voltage measured and calculated?".

How do I determine the cable cross-section?

A wire gauge is suitable for measuring the cable cross-section of a cable. You can also use a caliper gauge to determine the cable cross-section. In the case of a multi-core cable with fine strands, it is advisable to measure the cable cross-section with insulation so that accidental compression does not falsify the measurement.

Please also bear in mind that the diameter of the cable including insulation differs from manufacturer to manufacturer. If in doubt, it is therefore advisable to determine the cable cross-section of the individual wires. With some cables, the cable cross-section can also be identified by means of an imprint on the sheath.

What happens if the cable cross-section is too small or too large?

The longer and thinner a cable is, the greater the risk of heat build-up, which in turn increases the resistance of the conductor. In the worst case, this can melt the insulation and cause a fire. For this reason, the longer the cable, the larger the conductor cross-section in all electrical systems. Voltage drops are compensated for by using larger cross-sections, thus ensuring that a voltage of 230V is present in the cable network, for example.

Is the cable cross-section equal to the cable diameter?

The cable cross-section is an area measurement (in mm²) and the cable diameter is a length measurement (in mm). These can be calculated using simple formulas. In electrical engineering in particular, it is sometimes important to calculate the cable diameter in cable cross-section. Calculate the cable cross-section from the cable diameter using the formula:

A=r² * π = d² * π/4

Calculate the cable diameter from the cable cross-section using the formula

d=2* √A/ π = 2 * r

Note: the thickness of the insulation and the separating air for stranded wires must have an overall diameter that is around 14 % larger than that of a solid wire due to the individual wires lying next to each other.