Which factor does NOT affect short-circuit current?

The length of the circuit is not a determining factor for short-circuit current. Short-circuit current is primarily influenced by the voltage present in the circuit, the impedance of the circuit path (including any components such as transformers, conductors, or other resistive elements), and the percent impedance rating of transformers.

When a short circuit occurs, the very low resistance of the fault path allows a high current to flow based upon the applied voltage and the total impedance. While the length of the circuit could potentially impact the overall impedance to some degree due to resistive losses, the critical parameters that establish the magnitude of short-circuit currents relate much more directly to the voltage and the specific impedances present in the faulted condition. Thus, the length of the circuit primarily plays a minimal role in defining the short circuit current when considered alongside these other factors.