A device intended for personnel protection that de-energizes a circuit during a ground-fault current is known as a _____.

The correct answer identifies a Ground Fault Circuit Interrupter (GFCI) as the device designed for personnel protection by de-energizing a circuit in the event of a ground-fault current. A GFCI continuously monitors the current flowing in a circuit and compares it to the current returning. If it detects an imbalance, which usually indicates that current is leaking to the ground (indicating a potential shock hazard), it quickly disconnects the power to prevent electric shock.

This vital safety feature is essential in locations where electrical circuits may come into contact with water, such as kitchens, bathrooms, and outdoors, and is aligned with the National Electrical Code (NEC) regulations to ensure the safety of electrical installations.

The other options do not serve the same purpose as a GFCI. Current limiting devices protect against overloads or short circuits but do not specifically monitor for ground faults. Voltage regulators are used to maintain a consistent voltage level in an electrical system, but they do not provide protection against ground faults. Surge protectors are designed to protect against voltage spikes and surges but do not deactivate circuits in response to ground faults. Thus, the GFCI stands out as the correct choice for ensuring personnel safety from electric shock due to ground faults.