Fault Current Calculator

PFC (for the purpose of calculating fault current) is the acronym for Prospective Fault Current, not to be confused with PFC Power Factor Correction.

Prospective fault current is the amount of current that would flow in the event of a fault, fault current is measured in either kA (Kilo-amps) or Amps. 1kA = 1000 Amps, 0.5kA = 500 Amps, 0.05kA = 50 Amps.

There are different types of faults, Short Circuit and Earth Fault.

Prospective Short Circuit Fault Current is referred to to as PSCC while Prospective Earth Fault Current is referred to as PEFC.

Fault current is the amount of current that will flow under fault conditions.

Short-circuit current is the amount of current that will flow under a short circuit fault condition.

Short Circuit = A fault of negligible impedance between Live and Neutral (single phase or three phase), or Live and Live three phase. 

Ideally fault current should be measured using the appropriate test equipment, however should you forget to measure the actual fault current it is possible to calculate the PFC from the measured voltage and measured earth fault loop impedance values from that particular part of the circuit. 

Knowing the PFC fault current value is important when selecting the appropriate electrical equipment such as over-current protection devices.

The over-current protection device (Fuses, MCB’s etc) have a maximum kA rating which they can withstand, therefore we need to know what the actual fault current will be at that point of the circuit to ensure the correct MCB, fuse or MCCB is selected.