Which NEC rule clarifies grounding requirements for ungrounded systems?

The correct choice clarifies grounding requirements for ungrounded systems as outlined in the National Electrical Code (NEC). Specifically, the referenced rule focuses on the effective grounding of ungrounded systems to ensure safety and integrity in electrical installations.

In ungrounded systems, there are specific challenges when it comes to grounding, as these systems do not have a direct ground reference. The selected rule lays out the necessary conditions and practices to maintain safety, mitigate overvoltages, and ensure proper functioning of protective devices. This is crucial for preventing electrical hazards that could arise from transient voltages or insulation failures.

Other choices pertain to different aspects of grounding and bonding in electrical systems but do not specifically address ungrounded systems. For example, other sections may outline grounding requirements for different types of systems or explain general grounding principles, but they lack the focused context on ungrounded systems that this particular rule provides. Understanding these distinctions is vital for ensuring compliance and enhancing safety in electrical design and installation practices.