EN IEC 61225:2026

Overview

EN IEC 61225:2026 is a European standard developed by CENELEC (CLC) that establishes the requirements for static uninterruptible DC and AC power supply systems in nuclear power plants and other nuclear facilities. By adopting the IEC 61225:2025 standard without modification, EN IEC 61225:2026 ensures harmonized criteria for reliable, safe, and robust instrumentation, control, and electrical power systems critical to nuclear operations.

Uninterruptible Power Supply (UPS) systems and, in particular, Static Uninterruptible Power Supply (SUPS) systems, are essential for maintaining continuous power to nuclear plant equipment, especially systems important to nuclear safety. This standard outlines the performance, functional characteristics, and design expectations necessary to support uninterrupted operation under both normal and adverse conditions.

Key Topics

• Scope and Applicability: The standard addresses low voltage static UPS systems in nuclear power plants and, when relevant, in broader nuclear facilities.
• System Reliability: Emphasizes requirements for highly reliable and robust SUPS systems to ensure continuous operation of systems important to safety.
• Functional Performance: Specifies that SUPS must provide uninterruptible, quality power to connected loads within predefined voltage, frequency, and waveform limits, regardless of disturbances in the incoming supply.
• Design Considerations:
  • Analysis of voltage and frequency variations
  • Response to transient disturbances and loss of supply
  • Provisions against common cause and common mode failures
  • Ensuring redundancy and independence among system divisions
• Testing and Qualification: Establishes expectations for system monitoring, electrical protection, qualification of equipment (including environmental and seismic considerations), and routine maintenance.
• Integration in Plant Safety: Connects SUPS requirements with broader nuclear safety frameworks referenced in related international standards, facilitating the graded approach for verification based on system importance.

Applications

EN IEC 61225:2026 provides practical value in several areas of nuclear facility management:

• Design and Construction:
  • Ensures power supply continuity for critical safety and control systems in new nuclear power plants, small modular reactors (SMRs), and passive plant designs.
  • Reference for upgrading or modernizing existing facilities to international best practices.
• Operation and Maintenance:
  • Supplies criteria for ongoing system monitoring, protection, and maintenance.
  • Helps to anticipate operational occurrences such as transient voltage dips, grid loss, or phase imbalance, reducing risk of equipment failure.
• Safety and Compliance:
  • Serves as an authoritative basis for demonstrating compliance with European and international nuclear safety directives.
  • Assists nuclear operators and regulators in assessing adequacy of SUPS provisions during audit or inspection processes.

Related Standards

EN IEC 61225:2026 is part of an interlinked framework of nuclear power plant standards:

• IEC 61513: General requirements for instrumentation and control systems important to safety.
• IEC 63046: General requirements for electrical power systems in nuclear power plants.
• EN IEC 60709: Requirements for separation in systems important to safety.
• EN IEC 62138, EN IEC 62855, EN IEC 63046: Detailed requirements on specific power and instrumentation functions.
• IEC/IEEE 60780-323, 60980-344: Qualification standards for equipment under environmental and seismic conditions.
• IEC 62040 series: General requirements for uninterruptible power systems.
• IEC 62003, IEC 61000 series: Requirements for electromagnetic compatibility testing and compliance.
• IAEA safety standards: Including SSR-2/1 (Safety requirements), SSG-34 (Electrical power system design), and SSG-39 (Design of instrumentation and control).

EN IEC 61225:2026 thus ensures that static uninterruptible power supply systems for nuclear power plants conform to the latest international best practices, supporting both operational reliability and regulatory compliance across Europe.