structural:scholar_edition, information:classification
Warning:- The next paragraph is IMO incorrect. I am not expert enough to correct it, but I don't think it detects voltages, I think it detects imbalance in currents on Live and Neutral, or current flow in the Earth.
An earth-leakage circuit breaker (ELCB) is a safety device used in electrical installations with high Earth impedance to prevent shock. It detects small stray voltages on the metal enclosures of electrical equipment, and interrupts the circuit if a dangerous voltage is detected. Once widely used, more recent installations instead use residual-current devices which instead detect leakage current directly.