Which statement about GFCI operation is correct?

Which statement about GFCI operation is correct?

• A. AFCI trips on imbalance.
• B. OCPD trips on imbalance.
• C. Transformer trips on imbalance.
• D. Ground Fault Circuit Interrupter (GFCI) trips when there is an imbalance between hot and neutral currents.

Answer: (D)

The key idea is that a GFCI detects leakage by comparing the current in the hot and the neutral conductor. In normal operation, the current flowing out on the hot equals the current returning on the neutral. If some current leaks through a person or a faulty path to ground, the currents are no longer equal, and the GFCI quickly trips to cut power, typically at a few milliamps of difference. AFCIs protect against arcing faults, not imbalance between hot and neutral. They look for the distinctive electrical signature of arcing as current flows, which is a different fault mechanism than a ground leakage. OCPDs (overcurrent protective devices) trip on overcurrent conditions—when the current exceeds the device’s rating due to a short or overload—rather than due to any mismatch between hot and neutral currents. Transformers themselves don’t perform a trip function based on imbalance; they’re passive devices that change voltage and current; protection is provided by other devices upstream if needed. So the statement that a GFCI trips when there is an imbalance between hot and neutral currents correctly describes how GFCI protection operates.

The key idea is that a GFCI detects leakage by comparing the current in the hot and the neutral conductor. In normal operation, the current flowing out on the hot equals the current returning on the neutral. If some current leaks through a person or a faulty path to ground, the currents are no longer equal, and the GFCI quickly trips to cut power, typically at a few milliamps of difference.

AFCIs protect against arcing faults, not imbalance between hot and neutral. They look for the distinctive electrical signature of arcing as current flows, which is a different fault mechanism than a ground leakage.

OCPDs (overcurrent protective devices) trip on overcurrent conditions—when the current exceeds the device’s rating due to a short or overload—rather than due to any mismatch between hot and neutral currents.

Transformers themselves don’t perform a trip function based on imbalance; they’re passive devices that change voltage and current; protection is provided by other devices upstream if needed.

So the statement that a GFCI trips when there is an imbalance between hot and neutral currents correctly describes how GFCI protection operates.