Section 90.2(A) clearly describes the purpose of the National Electrical Code as the practical safeguarding of people and property from hazards arising from the use of electricity. Two types of ground-fault protection used in electrical distribution systems are ground-fault circuit interrupter (GFCI) protection and ground-fault protection of equipment (GFPE). Both types of protection function similarly during a ground-fault condition, but at different current and time levels. 

GFCIs are required to protect people from electric shock and electrocution, while GFPE must protect equipment. These two forms of protection directly align with the text in 90.2(A), “Practical Safeguarding.” The Code includes several important requirements for GFCI protection and for protecting large equipment from ground faults that can severely damage or even destroy equipment.

Requirements for GFCIs

GFCIs provide protection against electrocution and minimize the severity of electric shock a person can receive. Although there are no actual statistics available, data collected by the Consumer Product Safety Commission indicates that electrocutions in the United States have been decreasing since GFCI protective devices were introduced, specifically Class A GFCIs. 

GFCIs do not directly limit the level of current through the body during a contact event; instead, they reduce the amount of time the current is present. Extensive research about preventing electrocution resulted in established current and time levels for Class A GFCI devices. GFCI protection monitors current in the complete electrical circuit for an imbalance; therefore, it can be used in grounded systems.

There are several requirements for GFCI protection throughout the NEC. The first was for swimming pool installations, where a Class B GFCI device was required for circuits supplying underwater luminaires. The NEC requirements for GFCIs have increased significantly over the years and resulted in reduced shock and electrocution events.

Requirements for GFPE

GFPE differs from GFCI protection, as it protects larger equipment from devastating arcing events and destructive burn-downs.

GFPE requirements are provided in multiple NEC sections, such as 210.13, 215.10, 230.95, 240.13 and 517.17. Electric arcs generate significant amounts of heat, and, in a circuit of 277V to ground, an arcing fault is readily sustained. A ground fault is typically not a solid or “bolted fault” condition, so dynamic arcing impedance is introduced in the circuit. This reduces the fault current seen by a standard overcurrent protective device and increases the time the fault can exist, which allows arcing faults to manifest into destructive events. 

During an arc event, ionized gas is dispersed, creating a conductive gas or plasma in the atmosphere surrounding the busbars in the equipment. This condition often rapidly escalates from a phase-to-ground fault event to a phase-to-phase short-circuit condition. This is why 230.95 requires GFPE.

GFPE is generally required for solidly grounded wye services and feeders of more than 150V to ground but not exceeding 1,000V phase-to-phase for each disconnect rated at or above 1,000A. GFPE is required for nominal 480Y/277V, three-phase, 4-wire, wye-connected systems. The maximum settings are 1,200A and not longer than one second for fault currents 3,000A or more.

As indicated in 210.13, GFPE is also required for large branch circuits of more than 150V to ground but not exceeding 1,000V phase-to-phase for each disconnect rated at or above 1,000A. Note that GFPE is not permitted for fire pumps or in systems where a nonorderly shutdown or interruption would introduce additional hazards. 

GFPE is required to be performance tested when first installed on-site to ensure proper operation. Testing GFPE verifies that the system will interrupt a ground-fault event at selected current pickup and time settings. The performance testing must be conducted by qualified people in accordance with the manufacturer’s instructions and must include primary current injection. The test records must be made available to the authority having jurisdiction. 

Section 230.75 provides the requirement for a means to disconnect the grounded conductor (usually a neutral) within the equipment and is intended for testing purposes. The neutral disconnect link can be in the form of a busbar or, in smaller equipment, can be the terminal to which the neutral conductor is connected. Once the link is removed, a test can verify that the neutral (grounded conductor) is isolated from grounding connections on the load side of the service disconnect equipped with GFPE.