Increase to 25 mm²: voltage drop ~1.9 mV/A/m ( V_d = \frac2 \times 60 \times 30 \times 1.91000 = 6.84 , V ) → 2.97% → passes.

For three-phase: [ V_d = \frac\sqrt3 \times L \times I \times (R\cos\phi + X\sin\phi)1000 ] Simplified (for power factor ~0.8): ( V_d \approx \frac1.732 \times L \times I \times R1000 )

Increase to 16 mm² Cu PVC: rating ~85 A, voltage drop ~2.9 mV/A/m. ( V_d = \frac2 \times 60 \times 30 \times 2.91000 = 10.44 , V ) → 4.5% → still slightly above 3%.