Earth-leakage circuit breaker

Such a protection mechanism may be found in the form of distribution board modules, standalone devices, and special sockets (aka receptacles).

Voltage-operated ELCBs can still be found in the wild, though these largely fell out of favour after the invention of the current-sensing based RCD (aka GFCI) technology.

If the wrong type was used on an installation, the level of protection given could be substantially less than that intended, in particular the voltage operated type can only protect against faults or shocks to metalwork connected to the circuit ground, connected to the VO-ELCB, it cannot detect current leaving a live wire and running to ground by another path, such as via a person standing on the Earth.

The ELCB detects fault currents between line and earth (ground) conductors within the portion of the installation it protects.

If sufficient characteristics of a fault appear across the ELCB's sensing mechanism, then it will switch off the power, and remain off until manually reset.

A voltage-operated ELCB detects a rise in potential between the protected interconnected metalwork (equipment frames, conduits, enclosures) and a distant isolated Earth reference electrode.

They operate at a detected potential of around 50 volts to open a main breaker and isolate the supply from the protected premises.

RCDs exist in multiple sub-types, but the most basic form simply consists of a current transformer, in which the line and neutral conductors for the circuit are wound around a toroidal transformer core, and should there be a current leak between line and earth (ground), bypassing neutral, the imbalance in current flow between the line and neutral will cause a magnetic flux in the core, which then, if strong enough, activates a relay that opens the switch.

The individual items may each be electrically safe but a large number of small burden currents accumulates and reduces the tripping level.

In such cases, if the unit is allowed to power up without RCD protection then it will normally dry out and successfully pass inspection.