A fault current is excess current (also called overcurrent) that goes through a circuit because something has gone wrong. It can be one of three things:

A short circuit occurs when two or more normal current-carrying conductors make unintended contact. A ground fault occurs when an ungrounded conductor comes into contact with something grounded such as a conduit or the frame of some electrical equipment. An overload occurs when equipment draws current over its normal rating, or conductors carry more current than their rated ampacity, and the current persists for a sufficient length of time that it could cause damage or dangerous overheating. Short circuits and ground faults are both typically very high currents, but they are not overloads.

Overload

Faults

NOTE: This is an unformatted excerpt from our online fire protection training library.