Residual Current Device is a device that quickly breaks an Electrical Circuit to prevent serious harm from an ongoing Electrical Shock. These Electrical wiring devices are designed to disconnect a circuit quickly and automatically when it detects that the electric current is not balanced between the supply and return conductor of circuit. Any difference between the current in these conductors indicate leakage current, which present a shock hazard.
RCDs are used to provide protection against the specific dangers that may arise in electrical installations, including: