A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) is an electrical safety device, more specifically a form of Earth-leakage circuit breaker, that interrupts an electrical circuit when the current passing. A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) is an electrical safety device, more specifically a form of Earth-leakage circuit breaker, that interrupts an electrical circuit when the current passing. A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) is an electrical safety device, more specifically a form of Earth-leakage circuit breaker, that interrupts an electrical circuit when the current passing through line and neutral. The initiating device, such as a control switch, that directly or indirectly places equipment in or out of operation. A device that functions to give a desired amount of time delay before or after any point of operation in a switching sequence or protective relay system, except as provided by. The widely used United Sates standard ANSI/IEEE C37. Even in those parts of the world where IEC standards are predominate, the use of ANSI numbering. Protective Relay Definition: A protective relay is an automatic device that senses abnormal conditions in electrical circuits and triggers actions to isolate faults. There are many different kinds of devices like fuse, switch breaker, RBCC, etc. What is a Latched Relay? A latched relay is a type.