If the calculated percentage exceeds the allowable limit, the cable size must be increased.
For (kHz to MHz) → skin effect forces you to use AC resistance: [ R_ac = R_dc \times \frack \cdot r2 ] …but at 60 Hz, for solid wire up to ~4 AWG, (R_ac \approx R_dc). cable calculations
Here’s a concise technical answer.
For (microseconds), you’d use adiabatic heating formula — but that’s not normal “cable calculation.” If the calculated percentage exceeds the allowable limit,