Comments by "Jovet" (@jovetj) on "Technology Connections"
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The term ground-fault does have a technical meaning, not quite explained in the video. As electricity must always flow in a loop that we call a circuit, a ground fault is when circuit current leaks onto or passes through the grounding system.
The grounding system represents the electrical potential of the Earth itself, and everything not insulated from it. If you're standing on the ground, especially if you're not wearing rubber shoes, then you're the same electrical potential as the Earth. The third prong—the round one you see on these receptacles—is the ground prong, or earth prong. That ground connection allows other things to be connected to the same electrical potential as the Earth. Take the metal shell of a toaster, for instance. If that shell is insulated from the Earth potential, then should an energized wire in the toaster touch the shell, the shell will be come fully energized. Should you happen to touch that energized shell, then ZAP! But, if the metal shell is connected to the Earth's potential, then a ground fault will occur. That ground fault will cause the circuit breaker to sense an overload or a GFCI/RCD to trip, and that will happen before you even have the chance to touch it.
This all happens because one of the wires in a utility power circuit is almost always connected to the Earth, too. In the US and Canada, the neutral wire is connected to the Earth, so they share the same voltage potential. When a ground fault occurs, a secondary circuit is completed through the grounding system, which is what causes the circuit breaker overload or GFCI/RCD to trip.
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