Which two factors determine the prospective short-circuit current in an electrical installation?

The prospective short-circuit current in an electrical installation is influenced significantly by the supply voltage and the impedance of the earth fault loop. Supply voltage refers to the electrical potential provided to the installation, while impedance of the earth fault loop includes the resistive and reactive components of the circuit that limit the flow of current.

When a short circuit occurs, the prospective short-circuit current is calculated based on the available supply voltage divided by the total impedance of the fault loop. Therefore, higher supply voltages will lead to higher short-circuit currents, whereas higher impedance will reduce the short-circuit current. This relationship is key in designing protection devices and ensuring safety within electrical installations.

The other factors listed in the remaining options do not directly define the prospective short-circuit current. Wire gauge and total load, for example, relate to the capacity and current-carrying ability of conductors rather than the short-circuit conditions. Distance from the transformer and weather conditions can affect overall system performance but are not primary determinants of short-circuit levels. Similarly, ground type and installation age may influence other safety or performance aspects but do not specifically dictate the prospective short-circuit current.