Try 16 mm²: Vd per km ≈ 2.4 V/A/km Vd = 2.4 × 51 × 0.15 = 18.4 V → 4.6% → .
10 mm² → 72 A → meets 66.4 A requirement. electrical cable size calculation
Vd per km for 10 mm² copper (from table) ≈ 3.8 V/A/km (3-phase) Vd = 3.8 × 51 × 0.15 = %Vd = 29.1 / 400 = 7.3% – exceeds 5% limit → increase size . Try 16 mm²: Vd per km ≈ 2