# Voltage drop

For the calculation, a power factor $cos\varphi=0.9$ is assumed. The power factor is the ratio of active power to apparent power. When the waveforms are purely sinusoidal, the power factor is equal to the phase angle $\varphi$ 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:

• Low voltage installations supplied directly from a public low voltage distribution system: 3% in case of lighting and 5% for other uses
• Low voltage installations supplied from private LV supply: 6% in case of lighting and 8% for other uses

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