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A fault current limiter (FCL), also known as fault current controller (FCC), [1] is a device which limits the prospective fault current when a fault occurs (e.g. in a power transmission network) without complete disconnection. The term includes superconducting, solid-state and inductive devices. [2]
Current limiting is the practice of imposing a limit on the current that may be delivered to a load to protect the circuit generating or transmitting the current from harmful effects due to a short-circuit or overload. The term "current limiting" is also used to define a type of overcurrent protective device.
The amount of protection that a current limiting reactor offers depends upon the percentage increase in impedance that it provides for the system. [4] Current limiting reactor. The main motive of using current limiting reactors is to reduce short-circuit currents so that circuit breakers with lower short circuit breaking capacity can be used.
Distance protection detects both voltage and current. A fault on a circuit will generally create a sag in the voltage level. If the ratio of voltage to current measured at the relay terminals, which equates to an impedance, lands within a predetermined level the circuit breaker will operate.
The prospective short-circuit current of a predictable fault can be calculated for most situations. In power systems, protective devices can detect fault conditions and operate circuit breakers and other devices to limit the loss of service due to a failure. In a polyphase system, a fault may affect all phases equally, which is a "symmetric ...
Superconducting fault current limiters (SFCL) are used to limit current under a fault in the grid. In this system a superconductor is quenched (raised in temperature) when a fault in the gridline is detected. By quenching the superconductor the resistance rises and the current is diverted to other grid lines.
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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.