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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.
To eliminate this confusion, the IEC decided to apply the term residual current device (RCD) to differential-current-operated ELCBs. Residual current refers to any residue when comparing current in the outbound and return currents in the circuit. In a single phase circuit this is simply the live or phase current minus the neutral current.
GTO thyristors suffer from long switch-off times, whereby after the forward current falls, there is a long tail time where residual current continues to flow until all remaining charge from the device is taken away. This restricts the maximum switching frequency to about 1 kHz. It may be noted, however, that the turn-off time of a GTO is ...
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.
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.
For electrical equipment used outdoors or in wet areas, a residual current device or ground fault circuit interrupter may provide protection from electrical current leakage. Electrical devices have non-conductive insulation preventing contact with energized wires or parts, or may have conductive metal enclosures connected to earth ground so ...
Speed: Devices must function quickly to reduce equipment damage and fault duration, with only very precise intentional time delays. Sensitivity: Devices must detect even the smallest value of faults and respond. Economy: Devices must provide maximum protection at minimum cost. Simplicity: Devices must minimize protection circuitry and equipment.
Ripple (specifically ripple current or surge current) may also refer to the pulsed current consumption of non-linear devices like capacitor-input rectifiers. As well as these time-varying phenomena, there is a frequency domain ripple that arises in some classes of filter and other signal processing networks.