Formula
Single Phase: VD = 2 × I × L × R
Three Phase: VD = √3 × I × L × R
Max: 3% lighting, 5% power circuits
230V, 20A, 50m, 10mm² cable:
VD = 2×20×50×0.00361 = 7.22V (3.14%)
Receiving end = 222.8V — marginal
Frequently Asked Questions
IEC 60364 allows 3% for lighting and 5% for power circuits. Exceeding this causes equipment malfunction and overheating.
Increase cable size, reduce cable length, use sub-distribution board closer to the load, or balance the load across phases.