Under what condition is a separate ground rod required for a detached structure?

A separate ground rod is required for a detached structure when that structure is supplied by a feeder or branch circuit. This requirement is rooted in electrical safety standards which aim to minimize the risk of electrical shock and fire hazards. When a detached structure, such as a shed or garage, is fed separately from the main electrical service in a residence, grounding is essential to ensure that the electrical system operates safely. The separate ground rod provides a specific path for fault currents to safely dissipate into the earth, which is crucial for the protection of both people and equipment.

The other options do not establish the same necessity for a separate ground rod. For instance, the location of the structure, such as being on a hill, is not a determining factor for grounding requirements. Similarly, connection to a home network or the use of solar energy does not inherently affect the grounding needs; rather, it’s the electrical supply method that dictates the requirement for additional grounding measures.