Residual Current Device
Residual Current Device (RCD) ELCB is a safety device that is able to break instantly of an electric circuit to prevent serious electric shock to a human. The device is designed to automatically disconnect a circuit instantly when the electric current is not balanced between the energised line and neutral line. Leakage of electric current may lead to a shock hazard which is dangerous to a human. Leakage may cause harm or death if the leaking electric current pass through the torso of a human. It may cause serious harm to a person if it persists for more than a small fraction of a second. RCD is a device which is designed to disconnect instantly from the leakage of electric current to prevent any accident.
Do note that it does not provide protection against an unexpected high current. This high current is also known as Spikes or Surges.