Cable Sizing Formula May 2026

[ I_rated \ge I_load \times k_1 \times k_2 \times \dots \times k_n ]

[ A_min = \fracI_sc \times \sqrttk ]

But for sizing, we use the formula:

Short-circuit thermal check (k for Cu/PVC = 115): [ A_min = \frac10,000 \times \sqrt0.1115 \approx 27.5 \text mm^2 ] 25 mm² is slightly below → upgrade to 35 mm² for fault withstand. cable sizing formula

Voltage drop (use R=0.87 Ω/km, X=0.08 Ω/km for 25 mm²): [ V_d = \sqrt3 \times 0.1 \times 84.9 \times (0.87\times0.85 + 0.08\times0.526) \approx 11.8 \text V ] % drop = ( 11.8 / 400 \times 100 = 2.95% ) → OK (<5%). [ I_rated \ge I_load \times k_1 \times k_2