If triplen harmonics (3rd, 9th, etc.) are present, the neutral current may be high. IEC 60364-5-52 requires checking voltage drop in the neutral conductor for significant harmonic distortion.
: [ \Delta U = \sqrt3 \cdot 100 \cdot 0.15 \cdot (0.671 \cdot 0.85 + 0.085 \cdot 0.527) ] [ = 25.98 \cdot (0.570 + 0.045) = 25.98 \cdot 0.615 \approx 15.98 \text V ] Relative drop: (15.98 / 400 = 4.0%) → Acceptable for power circuit (<5%).
The IEC 60364 standard provides a formula for calculating the voltage drop in cables: iec 60364 cable sizing voltage drop formula
ΔV=2⋅I⋅(R⋅cosϕ+X⋅sinϕ)⋅Lcap delta cap V equals 2 center dot cap I center dot open paren cap R center dot cosine phi plus cap X center dot sine phi close paren center dot cap L ΔVcap delta cap V : Voltage drop in volts (V). : Design current in amperes (A). : One-way length of the cable in kilometers (km). : Resistance of the conductor at operating temperature ( : Reactance of the conductor (
$$ \Delta V = \frac2 \times L \times I \times R_201000 \times (1 + \alpha \times (T - 20)) $$ If triplen harmonics (3rd, 9th, etc
Resistance at temperature (t): [ R_t = R_20 \cdot [1 + \alpha_20 (t - 20)] ] Where (\alpha_20) ≈ 0.00393 /K for copper, 0.00403 /K for aluminum.
ΔV = (Ib * L * ρ) / A
$$ \Delta V = \frac2 \times L \times I \times (R \cos(\phi) + X \sin(\phi))1000 $$
Where:
The standard voltage drop formula for AC circuits is: