Which AC system is permitted to be grounded but not required?

The 480v delta, 3 phase system is permitted to be grounded but is not required to be grounded. In delta configurations, especially in three-phase systems like the 480v delta, the grounding practices vary based on the specific system design and the standards applicable to the installation. Grounding in this context is a safety measure aimed at protecting personnel and equipment from faults. However, it is not a necessity for operational safety in all delta systems, particularly those that are designed with no neutral point.

Grounding helps prevent electrical shock hazards and ensures effective fault current clearing by providing a return path. However, in some configurations, such as ungrounded delta systems, it is permissible to operate without grounding as long as certain safety protocols are followed. This is often the case where equipment is designed to tolerate transient conditions without grounding.

In contrast, other systems listed have different requirements regarding grounding. For example, 240v single phase often requires grounding for safety. The 600v three-phase, being typically part of industrial applications, mandates certain grounding measures. Similarly, delta configurations that have a neutral or are modified to include grounding require adherence to grounding standards. Hence, the distinction with the 480v delta allows for flexibility in grounding practices under regulatory