IEEE P666/D3

IEEE P666/D3 is an unapproved draft IEEE design guide for electric power service systems used in generating stations. It addresses the engineering of station service power arrangements that support plant operations, making it relevant to the design, review, and coordination of auxiliary electrical systems. As a revision of IEEE 666-1991 and now superseded by P666-D4, it is mainly useful for understanding the earlier draft guidance and the technical framework behind generator station service design.

Overview of IEEE P666/D3

This draft document focuses on the design of electric power service systems within generating stations, where dependable auxiliary supply is needed for control, protection, lighting, and support equipment. IEEE P666/D3 reflects guidance for planning and engineering station service power in a power generation environment, helping describe how these systems should be arranged and coordinated. Because it is an unapproved draft, it is best treated as technical reference material for historical context, design comparison, or document research rather than a current normative requirement.

Typical use cases

IEEE P666/D3 is typically relevant when reviewing station service power layouts for generating units, substation-style auxiliary systems, or plant electrical distribution associated with power generation facilities. It may be used when checking design approaches for transformers, switchgear, feeders, and backup supply arrangements that support essential loads in a station. Engineering teams, specifiers, and maintenance planners may consult IEEE P666/D3 when comparing legacy design practice with later IEEE guidance for generating station service systems.

Why it matters

For generating stations, consistent station service design can affect reliability, maintainability, and safe operation of essential electrical support systems. IEEE P666/D3 matters because it helps define a common technical basis for design decisions, reducing ambiguity in procurement, review, and system coordination. Even as an inactive draft, IEEE P666/D3 can still be valuable when evaluating older installations, tracing design intent, or understanding how auxiliary power requirements were addressed in earlier IEEE practice.

• Electric power service systems for generating stations
• Station service design and coordination
• Auxiliary supply for critical plant loads
• Legacy IEEE draft guidance
• Revision of IEEE 666-1991