Under what conditions are separately derived systems not required to be grounded when supplied by transformers rated under 1,000 volts?

Separately derived systems supplied by transformers rated under 1,000 volts have specific grounding requirements, and there are certain conditions under which grounding is not mandated. The correct understanding here hinges on the stipulations that lead to the affirmation of no grounding requirement.

When control power continuity is crucial, it often implies a dedicated system where disturbances from a grounding point could lead to mission-critical interruptions. In such cases, grounding may not be necessary to maintain the integrity of the control circuits.

When qualified persons service the installation, they possess the skills and knowledge to ensure safety and compliance with the electrical systems, which can mitigate risk factors typically associated with grounding. Their expertise decreases the necessity for a grounding requirement in specific contexts, especially if adequate safety measures are observed.

Moreover, when a system is used exclusively for control circuits, it tends to operate in a low-energy context, which typically poses reduced risk for safety standards. This specificity can justify the lack of requirement for grounding under certain operational parameters.

Thus, when these scenarios are met collectively—continuity of control power, servicing by qualified persons, and exclusive use for control circuits—the necessity for grounding becomes less critical, allowing for the appropriate conditions under which grounding is not required for separately derived systems. This comprehensive assessment leads to the