IEEE 666-1991

IEEE 666-1991 is a technical standard for electric power service systems used in generating stations. It provides design guidance for the electrical service infrastructure that supports station operations, helping engineers consider reliability, continuity, and safe integration with power, energy, and industry applications. As a superseded document, it remains useful for understanding earlier design practice and the expectations that shaped generator-station auxiliary power systems. IEEE 666-1991 is especially relevant where consistent service design affects operational stability.

IEEE 666-1991 overview

This standard focuses on the design of electric power service systems within generating stations, with attention to the electrical supplies that keep essential plant functions operating. It is intended to guide planning and engineering decisions around service arrangement, system coordination, and dependable station support. In practical terms, IEEE 666-1991 helps define how auxiliary power is organized so that control, monitoring, and operating equipment can function as intended under normal and upset conditions.

Typical use cases

IEEE 666-1991 is typically consulted when designing or reviewing the electrical service scheme for a generating station, including auxiliary power distribution, control-room support, and station service equipment. It may also be used when comparing design approaches for plant upgrades, documenting engineering requirements, or checking consistency across equipment interfaces. In power generation projects, the standard can help align service systems for pumps, controls, protection circuits, and other station loads that depend on a reliable supply.

Why this standard matters

For generating-station projects, clear guidance on service-system design can reduce uncertainty during engineering, procurement, and installation. IEEE 666-1991 supports more consistent decisions about how station power is arranged and how essential loads are supplied, which can improve reliability and limit design rework. It is also useful as a reference point when comparing legacy installations or evaluating whether a proposed arrangement matches established practice for auxiliary electrical service in power plants.

• Generating-station electric service design
• Auxiliary and station power planning
• Control and support load coordination
• Legacy design reference for power plants