IEC 62855:2016

Overview

IEC 62855:2016 – Nuclear power plants – Electrical power systems – Electrical power systems analysis – is an international standard published by the International Electrotechnical Commission (IEC). It delivers comprehensive engineering guidelines for analyzing AC and DC electrical power systems in nuclear power plants (NPPs). The primary objective of IEC 62855:2016 is to ensure that electrical power sources and distribution networks within NPPs are capable of supporting the plant's safe operation, controlled shutdown after anticipated operational occurrences or accident conditions, and movement to a final safe state.

This standard is essential for:

• Verifying the design of new nuclear power plants
• Assessing major modifications to electrical power systems in operating NPPs
• Establishing operational constraints and verifying limits for existing plants

By providing a framework for analytical studies, IEC 62855 supports operators, evaluators, and regulators in demonstrating that electrical power systems meet stringent nuclear safety requirements across all operating states and during fault or emergency scenarios.

Key Topics

IEC 62855:2016 outlines the following critical areas in the analysis of nuclear power plant electrical systems:

• Design Basis Considerations: Emphasizes the need to account for nuclear design criteria, safety classification, defense-in-depth strategies, and compliance with national and international safety codes.
• Scope of Analytical Studies: Covers essential studies such as:
  • Transient stability
  • Load flow
  • Short circuit and fault analyses
  • Electrical protection coordination
  • Lightning protection and electromagnetic compatibility (EMC)
• Analytical Methodology: Recommends using validated simulation tools, mathematical calculations, and tests to assess the robustness and adequacy of system design margins under normal, abnormal, and accident conditions.
• Types of Systems Analyzed:
  • Auxiliary power systems
  • On-site and off-site AC and DC power networks
  • Standby power sources
  • Uninterruptible power supplies (UPS)
• Acceptance and Verification: Details requirements for validation and verification analyses, including plant-specific acceptance criteria to confirm the electrical system’s ability to support safety functions.

Applications

IEC 62855:2016 has broad applications throughout the nuclear power industry:

• Design and Construction: Supports the verification and validation of new plant designs by ensuring electrical power systems can maintain plant safety in all operational scenarios.
• Plant Modifications: Provides a framework for demonstrating the adequacy and impact of major electrical system upgrades or modifications in existing nuclear power plants.
• Operational Safety: Facilitates the establishment of operational limits and constraints, helping operators manage both routine and emergency plant states safely.
• Engineering and Regulatory Assurance: Assists utilities, engineering firms, and regulatory bodies in conducting comprehensive analyses to demonstrate compliance with international nuclear safety requirements.

Related Standards

IEC 62855:2016 is part of a structured series of standards that address various aspects of safety and performance in nuclear power plants:

• IEC 61513: Covers general requirements for instrumentation and control (I&C) systems important to safety in NPPs.
• IEC 63046: Addresses general requirements for electrical power systems in NPPs (forthcoming at time of publication).
• IAEA Safety Standards: Includes references to IAEA SSR-2/1 (Safety of Nuclear Power Plants: Design) and IAEA SSG-34 (Design of Electrical Power Systems for Nuclear Power Plants).
• IEC 60880, IEC 62138, IEC 62566: Provide domain-specific guidance for software and instrumentation in nuclear applications.
• IEC 62645: Outlines cybersecurity requirements for NPPs.
• Other Related Documents: Guidance from ISO/IEC 27001 and 27002 on information security management, and other IEC and IAEA guides regarding grid reliability, safety classification, ageing management, and electromagnetic compatibility.

Keywords: IEC 62855, nuclear power plant, electrical power systems, power system analysis, AC DC systems, safety standards, electrical system design, transient stability, load flow, fault analysis, nuclear safety, plant operation, distribution network, electrical protection, verification, compliance.