EN IEC 63046:2021

SLOVENSKI STANDARD
01-julij-2021
Jedrske elektrarne - Elektroenergetski sistemi - Splošne zahteve (IEC 63046:2020)
Nuclear power plants - Electrical power system - General requirements (IEC
63046:2020)
Kernkraftwerke - Elektrische Stromversorgungssysteme - Allgemeine Anforderungen
(IEC 63046:2020)
Centrales nucléaires de puissance - Système d'alimentation électrique - Exigences
générales (IEC 63046:2020)
Ta slovenski standard je istoveten z: EN IEC 63046:2021
ICS:
27.120.20 Jedrske elektrarne. Varnost Nuclear power plants. Safety
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 63046

NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2021
ICS 27.120.20
English Version
Nuclear power plants - Electrical power system - General
requirements
(IEC 63046:2020)
Centrales nucléaires de puissance - Système d'alimentation Kernkraftwerke - Elektrische Stromversorgungssysteme -
électrique - Exigences générales Allgemeine Anforderungen
(IEC 63046:2020) (IEC 63046:2020)
This European Standard was approved by CENELEC on 2021-05-17. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 63046:2021 E
European foreword
The text of document 45A/1348/FDIS, future edition 1 of IEC 63046, prepared by SC 45A
"Instrumentation, control and electrical power systems of nuclear facilities" of IEC/TC 45 "Nuclear
instrumentation" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2022-02-17
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2024-05-17
document have to be withdrawn
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
As stated in the nuclear safety directive 2009/71/EURATOM, Chapter 1, Article 2, item 2, Member
States are not prevented from taking more stringent safety measures in the subject-matter covered by
the Directive, in compliance with Community law.
In a similar manner, this European standard does not prevent Member States from taking more
stringent nuclear safety and/or security measures in the subject-matter covered by this standard.
Endorsement notice
The text of the International Standard IEC 63046:2020 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards
indicated:
IEC 60364-5-52 NOTE Harmonized as HD 60364-5-52
IEC 60880 NOTE Harmonized as EN 60880
IEC 61508-1 NOTE Harmonized as EN 61508-1
IEC 61508-2 NOTE Harmonized as EN 61508-2
IEC 61508-3 NOTE Harmonized as EN 61508-3
IEC 61508-4 NOTE Harmonized as EN 61508-4
IEC 62003 NOTE Harmonized as EN IEC 62003
IEC 62040-3 NOTE Harmonized as EN 62040-3
IEC 62138 NOTE Harmonized as EN IEC 62138
IEC 62271-200 NOTE Harmonized as EN 62271-200
IEC 62305-1 NOTE Harmonized as EN 62305-1
IEC 62305-3 NOTE Harmonized as EN 62305-3
IEC 62305-4 NOTE Harmonized as EN 62305-4
IEC 62340 NOTE Harmonized as EN 62340
IEC 62566 NOTE Harmonized as EN 62566
IEC 62645 NOTE Harmonized as EN IEC 62645
ISO/IEC 27001 NOTE Harmonized as EN ISO/IEC 27001
ISO/IEC 27002 NOTE Harmonized as EN ISO/IEC 27002
ISO 9000 NOTE Harmonized as EN ISO 9000
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available here:
www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60038 (mod) 2009 IEC standard voltages EN 60038 2011
IEC 60671 -  Nuclear power plants - Instrumentation and EN 60671 -
control systems important to safety -
Surveillance testing
IEC 60709 2018 Nuclear power plants - Instrumentation, EN IEC 60709 2019
control and electrical power systems
important to safety - Separation
IEC 60964 2018 Nuclear power plants - Control rooms - EN IEC 60964 2019
Design
+EN IEC
60964:2019/AC:201
9-08
IEC 61225 -  Nuclear power plants - Instrumentation, EN IEC 61225 -
control and electrical power systems -
Requirements for static uninterruptible DC
and AC power supply systems
IEC 61226 -  Nuclear power plants - Instrumentation and EN 61226 -
control important to safety - Classification
of instrumentation and control functions
IEC 61513 2011 Nuclear power plants - Instrumentation and EN 61513 2013
control important to safety - General
requirements for systems
IEC 62671 -  Nuclear power plants - Instrumentation and - -
control important to safety - Selection and
use of industrial digital devices of limited
functionality
IEC 62808 -  Nuclear power plants - Instrumentation and EN 62808 -
control systems important to safety -
Design and qualification of isolation
devices
IEC 62855 2016 Nuclear power plants - Electrical power prEN IEC 62855 2021
systems - Electrical power systems
analysis
Publication Year Title EN/HD Year
IEC 62859 -  Nuclear power plants - Instrumentation and EN 62859 -
control systems - Requirements for
coordinating safety and cybersecurity
ISO 9001  Quality management systems - EN ISO 9001 2015
Requirements
IEC/IEEE 60780--  Nuclear facilities - Electrical equipment EN 60780-323 -
323 important to safety - Qualification
IEC/IEEE 60980--  Nuclear facilities - Equipment important to EN IEC/IEEE-
344 safety - Seismic qualification 60980-344

IEC 63046 ®
Edition 1.0 2020-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Nuclear power plants – Electrical power system – General requirements

Centrales nucléaires de puissance – Système d'alimentation électrique –

Exigences générales
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.120.20 ISBN 978-2-8322-8817-7

– 2 – IEC 63046:2020 © IEC 2020
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 9
1.1 General . 9
1.2 Application: new and pre-existing plants . 11
1.3 Framework . 11
1.4 Interaction with level 2 standards . 11
2 Normative references . 13
3 Terms and definitions . 14
4 Abbreviated terms . 23
5 Overall Electrical Power System life cycle . 24
6 Architecture of Electrical Power System: identification of requirements. 25
6.1 Objectives . 25
6.2 Safety requirements applicable to the electrical architecture design . 26
6.2.1 Defence in Depth . 26
6.2.2 Application of Single Failure Criterion . 26
6.2.3 Management of the Common Cause Failure . 26
6.2.4 Loss Of Off-site Power conditions . 26
6.2.5 Station Black Out conditions . 27
6.2.6 Loss of Electrical Power conditions . 27
6.2.7 Application of internal and external Hazards . 27
6.2.8 Nuclear security requirements . 28
6.2.9 Classification requirements . 28
6.2.10 Probabilistic requirements . 28
6.3 Electrical requirements . 28
6.3.1 Requirements coordinated with the electric grid operator . 28
6.3.2 Electrical disturbances . 29
6.4 Functional performance requirements . 29
6.5 Maintenance requirements . 30
7 Design of the electrical architecture . 30
7.1 Objectives . 30
7.2 Safety design provision . 30
7.2.1 Defence in Depth in the Electrical Power System . 30
7.2.2 Single Failure in the Electrical Power System . 31
7.2.3 Common Cause Failure in the Electrical Power System . 31
7.2.4 Provisions for coping with Loss Of Off-site Power . 37
7.2.5 Provisions for coping with Station Black Out . 38
7.2.6 Provisions to avoid or reduce Loss of Electrical Power . 38
7.2.7 Classification consideration . 38
7.2.8 Provisions to achieve the reliability target for the Electrical Power System . 39
7.3 Electrical design provision . 40
7.3.1 General . 40
7.3.2 Coordination with the grid . 40
7.3.3 Design to achieve electrical requirements . 40
7.4 Functional and performance design provisions . 46
7.4.1 General . 46

IEC 63046:2020 © IEC 2020 – 3 –
7.4.2 Electrical Power System studies . 46
7.4.3 Design of the Interruptible Power Supply System . 49
7.4.4 Design of the Uninterruptible Power Supply System . 49
7.5 Maintenance . 50
7.5.1 Consideration of the maintenance in the electrical design . 50
7.6 Multi-unit shared electrical power systems . 51
7.7 Electrical system layout . 51
7.8 Supporting and associated systems for the Electrical Power System . 51
7.9 Overall quality assurance programs . 52
7.10 Requirements for output documentation . 53
7.10.1 General . 53
7.10.2 Architecture principles . 54
7.10.3 Single line diagrams . 55
8 Sub-system requirements . 55
8.1 Electrical Power System basis requirements . 55
8.1.1 General . 55
8.1.2 System Design . 56
8.1.3 Single line diagram . 56
8.2 Equipment design specification . 56
8.3 Equipment requirements . 56
8.4 AC Interruptible Electrical Power Supply System . 56
8.5 AC/DC Uninterruptible Power Supply System . 57
8.6 Coordination and interaction with power grid . 57
8.7 Earthing . 57
9 Verification of the architecture of the Electrical Power System . 57
9.1 General . 57
9.2 Computerised tools and models verification . 57
9.2.1 Electrical Power System verification . 57
9.2.2 Layout of electrical power systems and equipment verification . 57
9.3 Test requirements . 58
10 Overall integration and commissioning . 59
10.1 General . 59
10.2 Requirements . 59
10.3 Output documentation . 60
11 Overall operation and maintenance . 60
11.1 General . 60
11.2 Requirements . 60
11.3 Output documentation . 60
12 System quality assurance plan . 61
12.1 General . 61
12.2 System verification plan . 61
12.3 System configuration management plan . 62
12.4 Fault resolution procedures . 62
Annex A (informative) Basic safety issues in NPPs . 63
A.1 General . 63
A.2 Plant safety objectives . 63
A.3 Plant safety analysis . 63
A.3.1 General . 63

– 4 – IEC 63046:2020 © IEC 2020
A.3.2 Analysis of event sequences . 64
A.3.3 Assessment of design basis: deterministic/probabilistic methods . 64
A.4 Defence in Depth . 64
Annex B (informative) AC Interruptible Electrical Power System . 67
B.1 General . 67
B.2 Electrical design provisions . 67
B.2.1 Steady state conditions for Electrical Power System . 67
B.2.2 Electrical disturbances . 68
B.3 Design of the Interruptible power system . 71
B.3.1 Design of the preferred power supply . 71
B.3.2 Design of the off-site power supply . 71
B.3.3 Design of on-site preferred power supply . 72
B.3.4 Design of the AC interruptible power systems important to safety . 72
B.3.5 Design of internal standby sources . 72
B.4 Preferred power supply system (from IAEA SSG 34:2016, chapter 6, clauses

6.1 to 6.44) . 73
B.4.1 General . 73
B.4.2 Operation . 73
B.4.3 Grid interface and agreement with grid operator . 73
B.4.4 Reliability of the preferred power supply . 73
B.4.5 Off-site power supplies . 74
B.4.6 Availability . 75
B.4.7 Independence of off-site circuits . 75
B.4.8 Switchyard . 76
B.5 Safety power supply system supporting DBC . 76
B.5.1 General . 76
B.5.2 Design (from IAEA SSG 34:2016, chapter 7, clauses 7.36 to 7.63) . 77
B.5.3 Testing (from IAEA SSG 34:2016, chapter 7, clauses 7.64 to 7.67). 79
B.5.4 Performance criteria (transient and dynamic) (from IAEA SSG 34:2016,
chapter 7, clauses 7.68 to 7.70) . 79
B.5.5 Relay protection of standby power sources (from IAEA SSG 34:2016,
chapter 7, clauses 7.71 to 7.75) . 79
B.5.6 Support systems for standby AC power sources . 80
B.5.7 Fuel for standby AC power sources . 80
B.6 Power supply system important to safety supporting DEC . 80
B.6.1 General . 80
B.6.2 Design (from IAEA SSG 34:2016, chapter 8, clauses 8.1 to 8.18) . 81
B.7 Mobile sources connections network . 82
B.8 Monitoring and switching of buses . 82
Annex C (informative) Earthing . 84
Annex D (informative) Logic diagram followed for the design of the EPS . 85
Bibliography . 86

Figure 1 – Scope of work of this document. 10
Figure 2 – Architecture of Electrical Power System . 12
Figure 3 – Connections between the overall Electrical Power System life cycle and the
life cycles of the electrical power sub- systems . 25
Figure 4 – Typical voltage design bases (IEC 62855) . 43

Table A.1 – Support of the electrical power supply for the defence in depth of the plant . 66

IEC 63046:2020 © IEC 2020 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
NUCLEAR POWER PLANTS –
ELECTRICAL POWER SYSTEM –
GENERAL REQUIREMENTS
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
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in the subject dealt with may participate in this preparatory work. International, governmental and non-
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 63046 has been prepared by subcommittee 45A: Instrumentation,
control and electrical power systems of nuclear facilities, of IEC technical committee 45:
Nuclear instrumentation.
The text of this International Standard is based on the following documents:
FDIS Report on voting
45A/1348/FDIS 45A/1355/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.

– 6 – IEC 63046:2020 © IEC 2020
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.
IEC 63046:2020 © IEC 2020 – 7 –
INTRODUCTION
a) Technical background, main issues, and organisation of the Standard
The purpose of this standard is to provide the high level specification and requirement to
implement a suitable Electrical Power System in a Nuclear Power Plant (NPP).
The electric power system in NPPs supports reactor systems important to safety. It also
allows electric energy production providing the transmission grid with active and reactive
power and electro-mechanical inertia.
The designers, operators of NPPs (utilities), equipment suppliers, systems evaluators and
licensors, may use this document.
b) Situation of the current Standard in the structure of the IEC SC 45A standard series
The entry point of the IEC SC 45A standard series should be summary report introducing the
two first level standards for I&C (IEC 61513) and the Electrical Power System (IEC 63046).
This document is the first level IEC SC 45A document tackling the issue of general
requirements for Electrical Power System and sub-systems.
For more details on the structure of the IEC SC 45A standard series, see item d) of this
introduction.
c) Recommendations and limitations regarding the application of this Standard
It is important to note that this Standard establishes no additional functional requirements for
safety systems.
To ensure that the Standard will continue to be relevant in future years, the emphasis has
been placed on issues of principle, rather than specific technologies.
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 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.
– 8 – IEC 63046:2020 © IEC 2020
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 was launched to cover
this objective. As IEC 63046 is published, from now on this Note 2 of the introduction of IEC/SC 45A standards will
not be included in the newly published standards.

IEC 63046:2020 © IEC 2020 – 9 –
NUCLEAR POWER PLANTS –
ELECTRICAL POWER SYSTEM –
GENERAL REQUIREMENTS
1 Scope
1.1 General
This document:
• 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;
• 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;
• has to be considered in conjunction with and at the same level as IEC 61513. These two
standards provide a complete framework establishing general requirements for
instrumentation, control, and Electrical Power System for Nuclear Power Plants.
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;
• the relationships between:
– the plant safety requirements and the architecture of the overall Electrical Power
System and its sub-systems (see Figure 1) including:
a) the contribution to the plant Defence in Depth;
b) the independency and redundancy provisions;
– the electrical requirements and the architecture of the Electrical Power System and its
sub-systems;
– the functional requirements and the architecture of the Electrical Power System and its
sub-systems;
– the requirements associated with the maintenance strategy and the architecture of the
Electrical Power System and its sub-systems;
• the design of Electrical power sub-systems (e.g. interruptible and uninterruptible);
• the requirements for supporting systems of Electrical Power System (HVAC, I&C, etc.);
• the Electrical Power System life-cycle framework.
This document does not cover the specification of:
• I&C systems;
• the transmission lines connecting to substations outside the NPP;
• electrical equipment requirements already defined in the industrial IEC standards;
• electrical power for security systems (e.g., fences, surveillance systems, entrance
control);
– 10 – IEC 63046:2020 © IEC 2020
• lighting and socket facility.
This document does not consider power production requirements.

Figure 1 – Scope of work of this document
NOTE Figure 1 is based on IAEA SSG34:2016, Figure 3, with adaptation regarding the scope.

IEC 63046:2020 © IEC 2020 – 11 –
This figure provides only an example. Various possible arrangements of buses, loads, generators and
interconnections would meet the requirements of SSR-2/1. Furthermore, many elements of the plant system, such
as buses that are not important to safety and direct current power systems, are not shown. This figure is intended
only to represent the relationship between the elements of the plant power systems that are within the safety
classification and the preferred power supply. The elements of the preferred power supply that are not within the
bounds of the important to safety power supply are outside the scope of the plant safety classification. The system
elements included in the important to safety power supplies will differ according to plant design and the
classification methods applied in different States. The classification methods are held by IEC 61226. Some plant
designs may not require safety standby power sources. All nuclear power plants are expected to have safety direct
current power supplies.
1.2 Application: new and pre-existing plants
This document is applicable to the Electrical Power System of new nuclear power plants and
upgrading or back fitting of existing plants.
For existing plants, only a subset of requirements may be applicable and this subset should
be identified at the beginning of any project.
1.3 Framework
This document consists of six normative clauses (an overview is provided in Figure 2):
– Clause 6 addresses the identification of requirements;
– Clause 7 addresses the design of the electrical architecture;
– Clause 8 addresses the sub-system requirements;
– Clause 9 addresses the verification;
– Clause 10 addresses the overall integration and commissioning;
– Clause 11 addresses the overall operation and maintenance.
1.4 Interaction with level 2 standards
This document shall permit an electrical designer to establish the list of requirements
applicable for the design.
It also provides the different provisions applicable for the different requirements.
These provisions will be applied to the different type of power networks (sub-system):
• interruptible AC power network;
• uninterruptible power network.
Moreover, other transverse level 2 standards will define requirements applicable to electrical
architecture definition.
The nuclear standards linked with the safety provisions (such as safety classification,
separation, qualification or surveillance testing, etc.) are considered as input data for this
document.
– 12 – IEC 63046:2020 © IEC 2020

6 Architecture of Electrical Power System: Identification of requirements

6.2 Safety requirements 6.3 Electrical requirements
6.2.1 Defence in Depth 6.3.1 Requirements coordinated with
the electric grid operator
6.2.2 Application of Single Failure 6.3.2 Electrical disturbances
Criterion
6.2.3 Management of the Common Cause
Failure
6.2.4 Loss Of Off-site Power conditions 6.4 Functional, performance
requirements
6.2.5 Station Black Out conditions
6.2.6 Loss of Electrical power conditions 6.5 Maintenance requirements
6.2.7 Application of internal and external
Hazards
6.2.8 Nuclear security requirements
6.2.9 Classification requirements
6.2.10 Probabilistic requirements

7 Overall Architecture of Electrical Power System and structured approach: Design of the electrical architecture

7.2 Safety design provision 7.3 Electrical design provision 7.6 Multi-unit shared
electrical power systems
7.2.1 Defence in Depth in the Electrical 7.3.2 Coordination with the grid
Power System
7.2.2 SF in the Electrical Power System 7.3.3 Design to achieve electrical 7.7 Electrical system
requirements layout
7.2.3 CCF in the Electrical Power System
7.2.4 Provisions for coping with LOOP 7.4 Functional and performance 7.8 Supporting and
design provisions associated systems for the
EPS
7.2.5 Provisions for coping with SBO 7.4.2 Electrical Power System studies
7.2.6 Provisions to avoid or reduce Loss 7.4.3 Design of the Interruptible Power 7.9 Overall quality
of Electrical Power Supply System assurance programs
7.2.7 Classification consideration 7.4.4 Design of the Uninterruptible
Power Supply System
7.2.7.2 Qualification  7.10 Requirements for
output documentation
7.2.7.3 Surveillance Testing 7.5 Maintenance
7.2.8 Provisions to achieve the reliability 7.5.1 Consideration of the maintenance
target for the Electrical Power System in the electrical design

8 Sub-System requirements
8.1 Electrical Power System basis 8.4 AC Interruptible Electrical Power 8.6 Coordination and
requirements Supply System interaction with the grid

8.2 Equipment design specification 8.5 AC/DC Uninterruptible Power 8.7 Earthing
Supply System
8.3 Equipment requirements
9 Verification of the a
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