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.m)

Formulae

$\sqrt{3} \left(R_c \mathrm{cos}\varphi+\omega L_m \mathrm{sin}\varphi\right)$	three-phase system
$2\left(R_c \mathrm{cos}\varphi+\omega L_m \mathrm{sin}\varphi\right)$	single-/two-phase system AC
$2R_c \mathrm{cos}\varphi$	single-/two-phase system DC

Related

$\mathrm{cos}\varphi$

Power factor

$L_m$

Inductance (mean) [H/m]

$\omega$

Angular frequency [rad/s]

$R_c$

Electrical resistance of conductor [$\Omega$/m]