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A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) [a] is an electrical safety device that interrupts an electrical circuit when the current passing through a conductor is not equal and opposite in both directions, therefore indicating leakage current to ground or current flowing to another powered conductor.
This is a category of devices, which are used to protect instruments, circuits and operators, while Earth leakage. Early ELCBs were voltage operated devices (VO-ELCB), detecting a voltage rise between installation metalwork, and an external electrode. These have now been replaced by current sensing devices (RCD/RCCB).
Breakers for protections against earth faults too small to trip an over-current device: Residual-current device (RCD), or residual-current circuit breaker (RCCB) — detects current imbalance, but does not provide over-current protection. In the United States and Canada, these are called ground fault circuit interrupters (GFCI).
The most common three-phase system will have three hot legs, 208 V to each other and 120 V each to the neutral. An older, but still widely used, high-leg delta system uses three phases with 240 volts phase-to-phase for motor loads, and 120 volts for lighting loads by use of a center-tapped transformer; two of the phases are 120 volts to neutral ...
A residual-current device (RCD), or residual-current circuit breaker (RCCB), is a device that instantly breaks an electric circuit to prevent serious harm from an ongoing electric shock. A fuse or circuit breaker also does that, 'instantly' of course, is subject to qualification.
When current flows from a line conductor to an earth wire, as is the case when a line conductor makes contact with an earthed surface in a Class I appliance, an automatic disconnection of supply (ADS) device such as a circuit breaker or a residual-current device (RCD) will automatically open the circuit to clear the fault.
The Federal Reserve’s top banking regulator Michael Barr will step down from his position in February, saying that "the risk of a dispute over the position could be a distraction from our mission."
In the case of a TT system where the impedance is high due to the lack of direct connection to the transformer neutral, a residual-current device (RCD) must be used to provide disconnection. RCDs are also used in other situations where rapid disconnection of small earth faults (including a human touching a live wire by accident, or damage) is ...