Feb 15, 2023

Why Ground Fault Protection Matters and Which Scheme For Sensing Ground Faults To Choose

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A ground fault normally occurs in one of two ways: by accidental contact of an energized conductor with normally grounded metal, or as a result of an insulation failure of an energized conductor. When an insulation failure occurs, the energized conductor contacts normally non-current-carrying metal, which is bonded to a part of the equipment-grounding conductor.

In a solidly grounded system, the fault current returns to the source primarily along the equipment-grounding conductors, with a small part using parallel paths such as building steel or piping.

If the ground return impedance were as low as that of the circuit conductors, ground fault currents would be high, and the normal phase-overcurrent protection would clear them with little damage.

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