Cable Calc Formula ((better)) Review

[ \boxedS = \max\left( S_ampacity, S_V_d, S_short-circuit \right) ]

[ S = \fracI \cdot \sqrtt\kappa \quad \text(adiabatic) ] cable calc formula

[ R_ac = R_dc \left(1 + y_s + y_p\right) ] Where (y_s) (skin) and (y_p) (proximity) depend on frequency and conductor spacing. For longer faults (>0.5s), the heat conducts into insulation. Use IEC 60949’s iterative method, which adds a factor (\epsilon): Simplified (common form):

:

: 185 mm² Cu XLPE. 6. Advanced Nuances 6.1 Skin & Proximity Effect For large conductors (>240 mm²), AC resistance exceeds DC resistance. The ratio (R_ac/R_dc) is given by: [ \boxedS = \max\left( S_ampacity

(185 mm² Cu, R=0.106 Ω/km, X=0.078 Ω/km): [ V_d = \sqrt3 \cdot 340 \cdot 0.250 \cdot (0.106\cdot0.85 + 0.078\cdot0.527) \approx 12.9V ] Drop % = (12.9/400 = 3.2%) — within typical 5% limit.

Simplified (common form):