WG 11 - TC 45/SC 45A/WG 11

IEC 61225:2025 specifies the performance and the functional characteristics of the low voltage static uninterruptible power supply (SUPS) systems in a nuclear power plant (NPP) and, when applicable, in nuclear facilities in general. An uninterruptible power supply (UPS) is an electrical equipment which draws electrical energy from a source, stores it, and maintains the supply in a specified form by means inside the equipment to output terminals. A SUPS has no rotating parts to perform its functions. The specific design requirements for the components of the power supply system are covered by IEC standards and other standards listed in the normative references. Otherwise, specific component-level design requirements are outside the scope of this document.

IEC/IEEE 63332-387:2024 defines the criteria for the application and testing of diesel generator (DG) units used as safety class standby power supplies in nuclear facilities. In general, the standard applies to new nuclear facilities as well as for upgrading or back-fitting of existing facilities. Existing facilities can voluntarily adopt the requirements to enhance the performance capabilities and reliability of the installed DG units. The standard can be used in applications where highly reliable onsite alternating current (AC) power source is required to maintain plant safety following an event with potential loss of offsite power for an extended duration.
This document provides the principal design criteria, the design features, testing, and qualification requirements for the individual DG units that enable them to meet their functional requirements as a part of the standby power supply under the conditions produced by the design basis events catalogued in the plant safety analysis.

IEC 63272:2024 specifies the performance and functional characteristics of the on-site AC interruptible power supply systems and applies to new nuclear facilities and newly installed or upgraded on-site AC interruptible power supply systems.
The specific design requirements for the components of the power supply system are defined by the IEC standards listed in the normative references and are outside the scope of this document.
The purpose of this document is to provide high level requirements for the design of on-site AC interruptible power supply systems as part of the overall electrical distribution system in a nuclear facility. This document defines the requirements for an electrical designer to establish the design of the AC interruptible electrical power supply for nuclear facilities. It is used in conjunction with Level 1 standard IEC 63046.

IEC 63298:2024 provide high level requirements and recommendations for the coordination of NPPs and the electric grid; see also item a) of the Introduction. The specific design requirements for components and equipment are covered by other specific IEC standards outside the scope of this document. This document also defines the coordination requirements to ensure that operating instructions for the electric grid and the NPP are developed to provide a means of safe and reliable operation. This document also defines the requirements for the development of a framework for any specific tests that may be deemed necessary for the electric grid and the NPP, such as testing of NPP regulation capabilities and load rejection to house load operation tests.

IEC 63046:2020 provides requirements and recommendations for the overall Electrical Power System. In particular, it covers interruptible and uninterruptible Electrical Power Systems including the systems supplying the I&C systems; This document is consistent and coherent with IEC 61513. Like IEC 61513, this document also highlights the need for complete and precise requirements, derived from the plant safety goals. Those requirements are prerequisites for generating the comprehensive requirements for the overall Electrical Power System architecture, and for the electrical power supply sub-systems. This document establishes the high level specification and requirement to implement a suitable Electrical Power System in a NPP that supports reactor systems important to safety. It also enables electrical energy production providing the transmission grid with active and reactive power and electro-mechanical inertia.

IEC 61225:2019 specifies the performance and the functional characteristics of the low voltage static uninterruptible power supply (SUPS) systems in a nuclear power plant and, for applicable parts, in general for nuclear facilities. An uninterruptible power supply is an electrical equipment which draws electrical energy from a source, stores it and maintains supply in a specified form by means inside the equipment to output terminals. A static uninterruptible power supply (SUPS) has no rotating parts to perform its functions.
This third edition cancels and replaces the second edition published in 2005. This edition includes the following significant technical changes with respect to the previous edition:
a) the principal objective of this edition is to address the requirements on the static uninterruptible power supplies in nuclear power plants;
b) in addition to Instrumentation and Control (I&C) power supplies include all static uninterruptible power supplies;
c) emphasize that the static uninterruptible power supplies shall protect the connected equipment (loads) from transients on the on-site AC distribution system (the immunity concept);
d) in accordance with the defence-in-depth concept, this standard applies to static uninterruptible power supplies for all equipment, not only for equipment important to safety, with a graded approach to verification and validation;
e) addition of the requirement that, when batteries are connected in parallel under abnormal operating conditions, they shall be properly protected with isolation devices to avoid any failure that may impair more than one division of the uninterruptible power supply.

IEC 62855:2016 provides the electrotechnical engineering guidelines for analysis of AC and DC electrical power systems in nuclear power plants (NPPs) in order to demonstrate that the power sources and the distribution systems have the capability for safe operation and shut down of the NPP, bringing it to a controlled state after an anticipated operational occurrence or accident conditions and finally reaching a safe state. This standard is intended to be used:
- for verification of the design of new nuclear power plants;
- for demonstrating the adequacy and impact of major modifications of electrical power systems in operating nuclear power plants;
- and where there is a requirement to assess and establish operating limits and constraints for existing plants.