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In an electric power system, a fault or fault current is any abnormal electric current. For example, a short circuit is a fault in which a live wire touches a neutral or ground wire. An open-circuit fault occurs if a circuit is interrupted by a failure of a current-carrying wire (phase or neutral) or a blown fuse or circuit breaker.
The effect of too high short-circuit current is discussed in the previous section. The short-circuit current should be around 20 times the rating of the circuit to ensure the branch circuit protection clears a fault quickly. Quick disconnecting is needed, because during a line-to-ground short circuit the grounding pin potential on the power ...
A fault current limiter is a nonlinear element which has a low impedance at normal current levels, but presents a higher impedance at fault current levels. Further, this change is extremely rapid, before a circuit breaker can trip a few milliseconds later.
A short circuit fault current can, within milliseconds, be thousands of times larger than the normal operating current of the system. [2] Damage from short circuits can be reduced or prevented by employing fuses, circuit breakers, or other overload protection, which disconnect the power in reaction to excessive current. Overload protection must ...
The current breaking capacity corresponds to a certain voltage, so an electrical apparatus may have more than one breaking capacity current, according to the actual operating voltage. Breaking current may be stated in terms of the total current or just in terms of the alternating-current (symmetrical) component.
A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) [a] is an electrical safety device, more specifically a form of Earth-leakage circuit breaker, that interrupts an electrical circuit when the current passing through line and neutral conductors of a circuit is not equal (the term residual relating to the imbalance), therefore ...
Possible causes for overcurrent include short circuits, excessive load, incorrect design, an arc fault, or a ground fault. Fuses, circuit breakers, and current limiters are commonly used overcurrent protection (OCP) mechanisms to control the risks. Circuit breakers, relays, and fuses protect circuit wiring from damage caused by overcurrent. [1]
Fault current can be limited by using current limiting devices such as current limiting breakers, grounding resistors, arc suppression coils or fuses. If the fault current is limited to 5 amperes or less, then many ground faults self-extinguish and do not propagate into phase-to-phase faults.