An RCD monitors the algebraic sum of the currents in the line and neutral conductors (the residual current) at the point at which it is installed in a circuit, and mechanically interrupts the circuit when this sum attains a predetermined value (the rated residual operating current ).
The following definition is given in Part 2 of BS 7671:
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‘Residual current device (RCD).A mechanical switching device or association of devices intended to cause the opening of the contacts when the residual current attains a given value under specified conditions.’
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‘Residual current device’ (RCD) is the generic name for a range of devices including:
| • | RCCB (residual current operated circuit-breaker without integral overcurrent protection) | |
| • | RCBO ( residual current operated circuit-breaker with integral overcurrent protection) | |
| • | SRCD (socket-outlet incorporating an RCD) | |
| • | Portable RCD | |
| • | An RCD formed of a suitable association of devices including current transformers, a residual current sensor, a test button and a circuit-breaker. |
Requelec 