[ V_d = \sqrt3 \times L \times I \times (R_ac \cos\phi + X \sin\phi) ]
[ I_rated \ge I_load \times k_1 \times k_2 \times \dots \times k_n ]
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.
[ I_req = 84.9 / 0.87 \approx 97.6 \text A ]