IEEE 859-1987

IEEE 859-1987 is a standard that defines terms for reporting and analyzing outage occurrences and outage states in electrical transmission facilities. It provides a common language for describing interruptions, restoration conditions, and related operating states in power system work. For utilities, engineers, and planners, this matters because consistent terminology helps support clearer records, better comparison of outage data, and more reliable communication across transmission operations and analysis activities.

IEEE 859-1987 overview

This standard focuses on terminology rather than equipment design, making it a useful reference for power and energy professionals who need to document transmission-facility outages in a consistent way. IEEE 859-1987 helps define how outage occurrences and outage states are described, which can reduce ambiguity in reports, studies, and operating logs. In technical environments, that consistency supports better interpretation of reliability information and more uniform reporting practices across organizations.

Typical use cases

IEEE 859-1987 is typically used when preparing outage reports, reviewing transmission-system performance, or analyzing operational events affecting electrical transmission facilities. It may support utility reliability tracking, planning studies, maintenance records, and internal engineering documentation. The terminology can also be helpful when comparing outage data across substations, transmission lines, and other network elements where precise definitions of outage states are important for consistent analysis and recordkeeping.

Why this standard matters

Clear outage terminology is essential for accurate communication and dependable analysis in transmission operations. IEEE 859-1987 helps reduce confusion between different outage conditions, which can improve the quality of compliance records, engineering reviews, and performance summaries. In practice, that can support safer coordination, more consistent data collection, and better decision-making when evaluating system behavior, maintenance impacts, or service interruptions. As a superseded standard, it remains useful for reference in legacy documentation and historical studies.

• Outage occurrence terminology
• Outage state definitions
• Transmission facility reporting
• Reliability and analysis records
• Legacy reference for utility documentation