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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.
An earth-leakage circuit breaker (ELCB) ... Residual current refers to any residue when comparing current in the outbound and return currents in the circuit. In a ...
Residual-current circuit breaker with overcurrent protection — combines the functions of a RCD and a MCB in one package. In the United States and Canada, these are called GFCI breakers. Earth leakage circuit breaker (ELCB) — This detects current in the earth wire directly rather than detecting imbalance. They are no longer seen in new ...
Residual-current devices (RCDs, RCCBs or GFCIs) are used for this purpose. Previously, an earth leakage circuit breaker is used. In industrial applications, earth leakage relays are used with separate core balanced current transformers. [18] This protection works in the range of milli-Amps and can be set from 30 mA to 3000 mA.
Until the 1950s, isolated ground domestic mains supplies tended to have no Residual-Current Device or Earth Leakage Circuit Breaker , and too high a ground impedance to blow a fuse if a live-to-earth fault occurred. This could leave metalwork in the house live.
"Residual current devices (RCD) or residual current circuit breakers (RCCB) are circuit breakers that operate to disconnect their circuit whenever they detect that current leaking out of the circuit (such as current leaking to earth through a ground fault) exceeds safety limits." Safety limits are not really what its about.
In electronics, leakage is the gradual transfer of electrical energy across a boundary normally viewed as insulating, such as the spontaneous discharge of a charged capacitor, magnetic coupling of a transformer with other components, or flow of current across a transistor in the "off" state or a reverse-polarized diode.
Earth fault protection also requires current transformers and senses an imbalance in a three-phase circuit. Normally the three phase currents are in balance, i.e. roughly equal in magnitude. If one or two phases become connected to earth via a low impedance path, their magnitudes will increase dramatically, as will current imbalance.