The full form of RCD is "Residual Current Device" (RCD).
This is a device that swiftly breaks an electrical circuit.
Therefore, by breaking an electrical circuit, a person is saved from serious harm caused by electric shock. It continuously monitors the electric current passing through the circuits it is designed to protect. Whenever a human touches a live item, the RCD rapidly switches the circuit off, reducing the harmful dangers.
Hence, the full form of RCD is the “Residual current device”.