For the calculation, a power factor $cosφ=0.9$ is assumed. The power factor is the ratio of active power to apparent power and when the waveforms are purely sinusoidal the phase angle φ between the current and voltage.

IEC 60364-5-52 in Annex G states that the voltage drop between the origin of an installation and any load point should not be greater than:

Symbol
$V_{\mathrm{drop}}$
Unit
V/A/km
Formulae
$1000 \sqrt{3} \left(R \cos{\left (\arccos{\left (0.9 \right )} \right )} + X_{\mathrm{c}} \sin{\left (\arccos{\left (0.9 \right )} \right )}\right)$three-phase system
$2000 R \cos{\left (\arccos{\left (0.9 \right )} \right )} + 2000 X_{\mathrm{c}} \sin{\left (\arccos{\left (0.9 \right )} \right )}$single-/two-phase system AC
$2000 R \cos{\left (\arccos{\left (0.9 \right )} \right )}$single-/two-phase system DC
$X_{\mathrm{c}}$