Journeyman Electrician Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

Ground-fault protection is a critical safety measure designed to protect people and equipment from the dangers of electrical faults that can result from insulation failures or accidental grounding. According to the National Electrical Code (NEC), ground-fault protection must be provided for electrical services rated at 1000 amperes and greater. Specifically, this requirement is applicable to all 3-phase, 277/480 volt services.

This is due to the higher risks associated with large power systems, especially in commercial and industrial settings, where the potential for ground faults is greater due to the scale of equipment and installations. The 3-phase, 277/480 volt service configuration is commonly used in these environments because it provides a more efficient distribution of electricity for high-demand applications.

While other systems may have specific grounding requirements, the regulation focuses on 3-phase services of this voltage and amperage to ensure adequate protection is in place against ground faults, which can lead to electrical shock or fire hazards. This safety measure contributes to minimizing risks during operations and maintenance of electrical systems.