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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, more specifically a form of Earth-leakage protection 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 ...
To address this the IEC introduced the term residual current device (RCD). Residual current refers to any residue when comparing current in the outbound and return currents in the circuit. In single phase circuits this is simply the line or phase current minus the neutral current. In a 3 phase circuit all current carrying conductors must be sensed.
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.
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).
This type of consumer unit was very popular in Britain until 2001 when wiring regulations mandated residual-current device (RCD) protection for sockets that could "reasonably be expected to" supply outdoor equipment (BS 7671:2001, ISBN 0-86341-373-0). There were a number of similar designs from other manufacturers but the Wylex ones are by far ...
Loose or poor connections in traditional electrical accessories and switchgear can cause heat to develop capable of starting a fire. This problem is known as High Resistance Connection (HRC) and safety devices such as fuses and Residual Current Devices (RCDs) are unable to disconnect the electrical supply because they cannot detect a HRC.
Such devices, most commonly ground fault circuit interrupters (GFCIs), typically run both the 120-volt energized conductor and the neutral return conductor through a current transformer, with the secondary coil connected to a trip device. Under normal conditions, the current in the two circuit wires will be equal and flow in opposite directions ...
The second problem, the inadequacy of fuses to act as the sole safety device in most power systems, is probably best resolved by the use of residual-current devices (RCDs). In any properly functioning electrical appliance, the current flowing into the appliance on the active line should equal the current flowing out of the appliance on the ...