Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

ground fault interrupter
a protective device used in commercial and residential wiring which monitors equipment connected to an electrical outlet and shuts off the power when a ground fault in the equipment is detected.
ground fault neutralizer
an inductor connected between the neutral of Y windings of a generator or transformer and ground. It is tuned to the machine's capacitance so as to minimize ground fault current.
ground-fault circuit interrupter (GFCI)
a device designed to detect ground-fault current above a threshold value (several milliamperes) and then interrupt the source of electrical power by opening a circuit breaker or a set of contacts. GFCIs are designed for personnel protection and are generally available in the form of circuit breakers and receptacles.
intermittent fault
a fault that appears, disappears, and then reappears in a repeated manner.
line to line fault
a fault on a three phase power line in which two conductors have become connected.
permanent fault
a fault that remains in existence indefinitely if no corrective actions are taken.
phase-to-phase fault
a fault with two transmission lines being short circuited.
power fault arc
an arc through soil extending from a power lines's lightning ground to a buried, grounded structure. These may form when lightning strikes an energized overhead electric power line.
single line to ground fault
a fault on a three phase power line in which one conductor has become connected to ground.
single phase to ground fault

See single line to ground fault
symmetrical fault
another term for a three-phase fault, a fault in which all three conductors of a three-phase power line are short-circuited together. System faults are symmetrical and can be analyzed by using single phase circuit.
symmetrical fault current
the total current flowing to a fault less the DC offset current. In many cases, fault current calculations are expressed in terms of symmetrical amps.
temporary fault
a fault that will not reoccur if the equipment is deenergized and then reenergized. An example of a temporary fault is when a lightning stroke causes an uninsulated overhead line to arc over an insulator, with no equipment damage.
three phase fault
a fault on a three phase power line in which all three conductors have become connected to each other and possibly the ground as well.
transient fault
a fault that can appear (e.g., caused by electrical noise) and disappear within some short period of time.
unsymmetrical fault
a fault on a three-phase power line in which the fault current is not equal in all three phases, e.g., a single-line-to-ground, double-line-toground or line-to-line fault.
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