Cable Sizing — Earthing

Where ( k ) = 226 for Cu (annealed, 40°C to 250°C). Simplified: [ A_mm^2 = I \times \sqrtt \times 0.143 \quad (\textfor Cu, 1–3s) ] Most accurate for fault current withstand. From IEC 60364-5-54 :

| Largest service conductor (AWG/kcmil Cu) | GEC size (AWG Cu) | |------------------------------------------|-------------------| | 2 AWG or smaller | 8 AWG | | 1/0 – 4/0 | 4 AWG | | 250 – 500 kcmil | 2 AWG | | Over 1100 kcmil | 3/0 AWG | Used for large installations (generators, substations, industrial plants). earthing cable sizing

[ A_mm^2 = I \times \sqrt\fract\Delta T \times k ] Where ( k ) = 226 for Cu (annealed, 40°C to 250°C)

[ S = \frac\sqrtI^2 \times tk ]

| Phase conductor size (mm²) | Minimum protective conductor (mm²) | |----------------------------|-------------------------------------| | ≤ 16 | Same as phase | | 25 – 35 | 16 | | 50 – 95 | 25 | | ≥ 120 | 50 | [ A_mm^2 = I \times \sqrt\fract\Delta T \times