Nuclear power plants - Instrumentation, control and electrical power systems - Requirements for static uninterruptible DC and AC power supply systems

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.

Centrales nucléaire de puissance - Systèmes d'instrumentation, de contrôle-commande et d'alimentation électrique - Exigences pour les systèmes d'alimentation en courant alternatif et en courant continu statiques sans interruption

l'IEC 61225:2019 spécifie les performances et les caractéristiques fonctionnelles des systèmes d'alimentation statiques sans interruption (ASSI) en basse tension dans les centrales nucléaires de puissance et, pour les parties pertinentes, dans les installations nucléaires. Une source d’alimentation électrique non-interruptible est un équipement électrique qui tire l’énergie électrique d’une source, la stocke et maintien une alimentation aux bornes de sortie sous une forme spécifiée en utilisant des moyens internes à l’équipement. Une alimentation statique sans interruption (ASSI) ne comprend pas de partie tournante pour réaliser sa fonction.
Cette troisième édition annule et remplace la deuxième édition parue en 2005. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) l'objectif principal de la présente édition est de fournir les exigences relatives aux alimentations statiques sans interruption dans les centrales nucléaires de puissance;
b) outre les alimentations des systèmes d'instrumentation et de contrôle-commande (I&C), la présente édition couvre l'ensemble des alimentations statiques sans interruption;
c) elle met l'accent sur le fait que les alimentations statiques sans interruption doivent protéger le matériel connecté (charges) des transitoires présents sur le réseau de distribution en courant alternatif sur site (concept d'immunité);
d) conformément au concept de défense en profondeur, la présente norme s'applique aux alimentations statiques sans interruption pour l'ensemble des matériels, pas seulement aux matériels importants pour la sûreté, avec une approche graduelle de la vérification et de la validation;
e) ajout de l'exigence précisant que, lorsque les batteries sont connectées en parallèle en conditions de fonctionnement anormal, elles doivent être protégées de manière adéquate au moyen d'appareils d'isolement afin d'éviter toute défaillance pouvant impacter plus d'une division de l'alimentation sans interruption.

General Information

Status
Published
Publication Date
14-Feb-2019
Current Stage
PPUB - Publication issued
Completion Date
15-Feb-2019
Ref Project

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IEC 61225
Edition 3.0 2019-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Nuclear power plants – Instrumentation, control and electrical power systems –
Requirements for static uninterruptible DC and AC power supply systems
Centrales nucléaires de puissance – Systèmes d'instrumentation, de contrôle-
commande et d'alimentation électrique – Exigences pour les systèmes
d'alimentation en courant alternatif et en courant continu statiques sans
interruption
IEC 61225:2019-02(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 61225
Edition 3.0 2019-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Nuclear power plants – Instrumentation, control and electrical power systems –
Requirements for static uninterruptible DC and AC power supply systems
Centrales nucléaires de puissance – Systèmes d'instrumentation, de contrôle-
commande et d'alimentation électrique – Exigences pour les systèmes
d'alimentation en courant alternatif et en courant continu statiques sans
interruption
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.120.20 ISBN 978-2-8322-6382-2

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 61225:2019 © IEC 2019
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 8

3 Terms and definitions ...................................................................................................... 9

4 Abbreviated terms ......................................................................................................... 11

5 System requirements ..................................................................................................... 11

5.1 General ................................................................................................................. 11

5.2 Function and description ....................................................................................... 12

5.2.1 Preamble ....................................................................................................... 12

5.2.2 Designations .................................................................................................. 14

5.2.3 Direct current systems ................................................................................... 14

5.2.4 Alternating current systems ........................................................................... 14

5.3 System divisions ................................................................................................... 15

5.4 System boundaries ............................................................................................... 15

6 Functional requirements for static uninterruptible power supplies .................................. 15

6.1 Static uninterruptible power supplies for systems important to safety .................... 15

6.2 Batteries and battery chargers .............................................................................. 16

6.3 Inverters and bypass switches .............................................................................. 17

6.4 UPS ...................................................................................................................... 18

6.5 Converters used for voltage stabilization ............................................................... 18

6.6 I&C power supply using DC/DC-converters and AC/DC-converters ....................... 19

7 Requirements for distribution systems ........................................................................... 19

7.1 System aspects .................................................................................................... 19

7.2 Load allocation ..................................................................................................... 19

7.3 Electrical aspects .................................................................................................. 21

7.4 Earthing ................................................................................................................ 22

8 Effects of loads on supply quality................................................................................... 22

8.1 General ................................................................................................................. 22

8.2 Electromagnetic interference................................................................................. 22

8.3 Transients ............................................................................................................. 22

8.4 Load current ......................................................................................................... 23

8.5 Power supplies to loads of lower safety classification............................................ 23

9 Monitoring and protection .............................................................................................. 23

9.1 General ................................................................................................................. 23

9.2 Monitoring ............................................................................................................. 24

9.3 Electrical protection .............................................................................................. 24

10 Qualification of equipment ............................................................................................. 25

11 Design to cope with ageing ............................................................................................ 25

12 Testing .......................................................................................................................... 25

13 Maintenance .................................................................................................................. 26

Annex A (informative) Examples of voltage input variations ................................................ 27

Annex B (informative) Examples of specifications ................................................................ 29

B.1 Example 1: Specification for an DC power supply for equipment requiring a

non-interruptible supply......................................................................................... 29

---------------------- Page: 4 ----------------------
IEC 61225:2019 © IEC 2019 – 3 –
B.2 Example 2: Specification for AC power supply for equipment requiring a non-

interruptible supply ............................................................................................... 30

B.3 Example 3: Specification for DC power supply with DC/DC converter for

equipment ............................................................................................................. 31

B.4 Human factor engineering programme .................................................................. 31

Bibliography .......................................................................................................................... 33

Figure 1 – System boundary ................................................................................................. 13

Figure 2 – Example of one division of an uninterruptible power supply system ...................... 20

Figure 3 – Example of I&C uninterruptible AC power supply system ...................................... 21

Figure A.1 – Example of voltage variations on the on-site AC power system during

clearing of a transmission system fault ................................................................................. 27

Figure A.2 – Example of on-site voltage profile after loss of load (transfer to house

load operation)...................................................................................................................... 27

Figure A.3 – Example of simulated safety bus voltages, double open phase condition

in the 400 kV line to the unit transformer ............................................................................... 28

Table B.1 – Example 1 .......................................................................................................... 29

Table B.2 – Example 2 .......................................................................................................... 30

Table B.3 – Example 3 .......................................................................................................... 31

---------------------- Page: 5 ----------------------
– 4 – IEC 61225:2019 © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
NUCLEAR POWER PLANTS – INSTRUMENTATION, CONTROL AND
ELECTRICAL POWER SYSTEMS – REQUIREMENTS FOR STATIC
UNINTERRUPTIBLE DC AND AC POWER SUPPLY SYSTEMS
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

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International Standard IEC 61225 has been prepared by subcommittee 45A: Instrumentation,

control and electrical power systems of nuclear facilities, of IEC technical committee 45:

Nuclear instrumentation.

This third edition cancels and replaces the second edition published in 2005. This edition

constitutes a technical revision.

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;
---------------------- Page: 6 ----------------------
IEC 61225:2019 © IEC 2019 – 5 –

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.

The text of this International Standard is based on the following documents:
FDIS Report on voting
45A/1235/FDIS 45A/1250/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
---------------------- Page: 7 ----------------------
– 6 – IEC 61225:2019 © IEC 2019
INTRODUCTION
a) Technical background, main issues and organization of the standard

The 1993 issue of IEC 61225 was developed for specifying the requirements relevant to

the design of electrical supplies for I&C systems in nuclear power plants. Considering the

experience gathered worldwide on this subject, in 2003 working group A2 recommended a

revision to this standard so that a new revision, IEC 61225 Ed. 2 (2005), could be

consistently integrated into the SC 45A standard series. In 2015, working group A11

recommended a revision to this standard following the publication of the revision of IAEA

SSG-34 and that the scope of the standard should cover static uninterruptible power

supplies for all types of connected equipment.

International operating experience with electrical supply systems in nuclear power plants

has highlighted a number of supply voltage variations and malfunctions, such as:

– voltage perturbations due to disturbances on the internal AC distribution system (with

origin off-site or on-site);
– voltage overshoot on loss of grid;
– open phase conditions (one or two phases);
– asymmetrical faults.

These types of perturbations can degrade the performance of static uninterruptible power

supplies and ultimately result in failure of connected equipment.

One of the objectives of the uninterruptible power supplies is to protect the connected

equipment from voltage variations on the on-site AC distribution system (the immunity

concept). The power supplies shall also guarantee an output voltage with specified

magnitude and waveform (in case of AC) to connected loads. The power supplies shall

have the capacity to supply the relevant loads during a specified time regardless of any

voltage variations on the on-site AC distribution system.

Examples of voltage and frequency variations in the incoming feeder to the supplies can

be found in informative Annex A. Examples of specifications for static uninterruptible

power supplies can be found in informative Annex B.

This standard is applicable to the design of static uninterruptible electrical power supplies

in new nuclear power plants, when design work is initiated after the publication of this

standard. It also serves as a reference for upgrading and modernizing existing nuclear

power plants.

b) Situation of the current standard in the structure of the SC 45A standard series

IEC 61225 is a second level document specifically addressing the particular topic of

requirements for electrical supplies.

For more details on the structure of the SC 45A standard series, see item d) of this

introduction.
c) Recommendations and limitations regarding the application of this standard

This standard is to be applied in conjunction with IEC 61513, IEC 60709, IEC 60880,

IEC 62138, IEC 62855 and IEC 63046 (to be published).

d) Description of the structure of the IEC SC 45A standard series and relationships

with other IEC documents and other bodies documents (IAEA, ISO)
The top-level documents of the IEC SC 45A standard series are IEC 61513 and

IEC 63046. IEC 61513 provides general requirements for I&C systems and equipment that

are used to perform functions important to safety in NPPs. IEC 63046 provides general

requirements for electrical power systems of NPPs; it covers power supply systems

including the supply systems of the I&C systems. IEC 61513 and IEC 63046 are to be

considered in conjunction and at the same level. IEC 61513 and IEC 63046 structure the

IEC SC 45A standard series and shape a complete framework establishing general

requirements for instrumentation, control and electrical systems for nuclear power plants.

IEC 61513 and IEC 63046 refer directly to other IEC SC 45A standards for general topics

related to categorization of functions and classification of systems, qualification,

separation, defence against common cause failure, control room design, electromagnetic

---------------------- Page: 8 ----------------------
IEC 61225:2019 © IEC 2019 – 7 –

compatibility, cybersecurity, software and hardware aspects for programmable digital

systems, coordination of safety and security requirements and management of ageing.

The standards referenced directly at this second level should be considered together with

IEC 61513 and IEC 63046 as a consistent document set.

At a third level, IEC SC 45A standards not directly referenced by IEC 61513 or by

IEC 63046 are standards related to specific equipment, technical methods, or specific

activities. Usually these documents, which make reference to second-level documents for

general topics, can be used on their own.

A fourth level extending the IEC SC 45 standard series, corresponds to the Technical

Reports which are not normative.

The IEC SC 45A standards series consistently implements and details the safety and

security principles and basic aspects provided in the relevant IAEA safety standards and

in the relevant documents of the IAEA nuclear security series (NSS). In particular this

includes the IAEA requirements SSR-2/1, establishing safety requirements related to the

design of nuclear power plants (NPPs), the IAEA safety guide SSG-30 dealing with the

safety classification of structures, systems and components in NPPs, the IAEA safety

guide SSG-39 dealing with the design of instrumentation and control systems for NPPs,

the IAEA safety guide SSG-34 dealing with the design of electrical power systems for

NPPs and the implementing guide NSS17 for computer security at nuclear facilities. The

safety and security terminology and definitions used by SC 45A standards are consistent

with those used by the IAEA.

IEC 61513 and IEC 63046 have adopted a presentation format similar to the basic safety

publication IEC 61508 with an overall life-cycle framework and a system life-cycle

framework. Regarding nuclear safety, IEC 61513 and IEC 63046 provide the interpretation

of the general requirements of IEC 61508-1, IEC 61508-2 and IEC 61508-4, for the
nuclear application sector. In this framework IEC 60880, IEC 62138 and IEC 62566

correspond to IEC 61508-3 for the nuclear application sector. IEC 61513 and IEC 63046

refer to ISO as well as to IAEA GS-R part 2 and IAEA GS-G-3.1 and IAEA GS-G-3.5 for

topics related to quality assurance (QA). At level 2, regarding nuclear security, IEC 62645

is the entry document for the IEC/SC 45A security standards. It builds upon the valid high

level principles and main concepts of the generic security standards, in particular

ISO/IEC 27001 and ISO/IEC 27002; it adapts them and completes them to fit the nuclear

context and coordinates with the IEC 62443 series. At level 2, IEC 60964 is the entry

document for the IEC/SC 45A control rooms standards and IEC 62342 is the entry
document for the ageing management standards.

NOTE 1 It is assumed that for the design of I&C systems in NPPs that implement conventional safety

functions (e.g. to address worker safety, asset protection, chemical hazards, process energy hazards)

international or national standards would be applied.

NOTE 2 IEC/SC 45A domain was extended in 2013 to cover electrical systems. In 2014 and 2015 discussions

were held in IEC/SC 45A to decide how and where general requirements for the design of electrical systems

were to be considered. IEC/SC 45A experts recommended that an independent standard be developed at the

same level as IEC 61513 to establish general requirements for electrical systems. Project IEC 63046 is now

launched to cover this objective. When IEC 63046 is published, this NOTE 2 of the introduction of IEC/SC 45A

standards will be suppressed.
---------------------- Page: 9 ----------------------
– 8 – IEC 61225:2019 © IEC 2019
NUCLEAR POWER PLANTS – INSTRUMENTATION, CONTROL AND
ELECTRICAL POWER SYSTEMS – REQUIREMENTS FOR STATIC
UNINTERRUPTIBLE DC AND AC POWER SUPPLY SYSTEMS
1 Scope

This document 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.

The specific design requirements for the components of the power supply system are covered

by IEC standards and standards listed in the normative references and are otherwise outside

the scope of this document.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their

content constitutes requirements of this document. For dated references, only the edition

cited applies. For undated references, the latest edition of the referenced document (including

any amendments) applies.
IEC 60038, IEC standard voltages

IEC 60146-1-1, Semiconductor converters – General requirements and line commutated

converters – Part 1-1: Specification of basic requirements

IEC 60146-2, Semiconductor converters – Part 2: Self-commutated semiconductor converters

including direct d.c. converters

IEC 60364-4-41, Low voltage electrical installations – Part 4.41: Protection for safety –

Protection against electric shock

IEC 60709, Nuclear power plants – Instrumentation, control and electrical power systems

important to safety – Separation

IEC/IEEE 60780-323, Nuclear power plants – Electrical equipment important to safety –

Qualification
IEC 60880, Nuclear power plants – Instrumentatio
...

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