Nuclear power plants - Instrumentation, control and electrical power systems important to safety - Separation (IEC 60709:2018)

This document is applicable to nuclear power plant instrumentation and control (I&C) and
electrical systems and equipment, whose functions are required to be independent due to
their contribution to:
• a redundant or diverse safety group;
• different defence in depth levels;
• different safety classes and also with non-classified (NC) systems.
It is also applicable to temporary installations which are part of those I&C and electrical
systems important to safety (for example, auxiliary equipment for commissioning tests and
experiments or mobile power supply systems). Clause 7 is intended particularly for electrical
isolation, Clause 8 is intended particularly for the cabling and the arrangement of equipment
of I&C and electrical systems important to safety.
This document applies to I&C and electrical systems of new nuclear power plants and to I&C
and electrical upgrading or back-fitting of existing plants. For existing plants see 1.2 and 5.4.
Where independence is required by general safety standards such as IAEA safety guides,
IEC 61513 (for I&C), IEC 63046 (for electrical systems) and other project constraints, one
aspect of achieving this independence is physical separation and electrical isolation between
the systems and their equipment that perform safety functions. This document defines the
assessments needed and the technical requirements to be met for I&C and electrical systems,
equipment or cables for which separation is required. Those means are to achieve adequate
physical separation and electrical isolation between redundant sections of a system and
between a higher and lower class systems. This separation is needed to prevent or minimise
the impact on safety that could result from faults and failures which could be propagated or
affect several sections of a system or several systems.
The requirements for functions, and their associated systems and equipment, to be
independent are normally defined in detail in the project documentation; the method of
determining and defining these requirements is not the subject of this document.
Following IAEA SSR-2/1 Requirement 21, separation means by physical separation, electrical
isolation, functional independence and independence of communication are considered. In
this document physical separation and electrical isolation are treated. Functional
independence and independence of communication are not considered in this document.
More details referring to functional independence, independence from control systems and
independence of communication are given in Annex D.

Kernkraftwerke - Leittechnik und elektrische Energieversorgungssysteme mit sicherheitstechnischer Bedeutung - Physikalische und elektrische Trennung (IEC 60709:2018)

Centrales nucléaires de puissance - Systèmes d'instrumentation, de contrôle-commande et d'alimentation électrique importants pour la sûreté - Séparation (IEC 60709:2018)

L'IEC 60709:2018 est applicable aux systèmes d’instrumentation et de contrôle-commande (I&C) des centrales nucléaires de puissance ainsi qu’aux systèmes et équipements électriques, dont il est exigé que les fonctions soient indépendantes en raison de leur contribution à:


       
  • un groupe de sûreté redondant ou varié;

  •    
  • différents niveaux de défense en profondeur;

  •    
  • différentes classes de sûreté et avec les systèmes non classés (NC).


Cette norme est aussi applicable aux installations temporaires qui font partie de ces systèmes d’I&C et électriques importants pour la sûreté (par exemple, les équipements auxiliaires pour les essais de mise en service et l’expérimentation ou pour les systèmes mobiles d’alimentation électrique).
Cette nouvelle édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:

       
  • intégration d’exigences relatives au principe de séparation dans les systèmes électriques importants pour la sûreté;

  •    
  • définition de critères de séparation pour les systèmes d’I&C et électriques de manière générale;

  •    
  • mise en cohérence de la norme avec les nouvelles révisions des documents de l’AIEA et extension du domaine d’application pour inclure de nouveaux aspects de separation.

Jedrske elektrarne - Merilna, nadzorna in elektroenergetska oprema za zagotavljanje varnosti - Ločevanje (IEC 60709:2018)

Ta dokument se uporablja za merilno, nadzorno in elektroenergetsko opremo ter sisteme v jedrskih elektrarnah, katerih funkcije morajo biti neodvisne zaradi prispevka k:
• redundantni ali raznoliki varnostni skupini;
• različni zaščiti v globinskih nivojih;
• različnim varnostnim razredom in tudi nerazvrščenim (NC) sistemom.
Uporablja se tudi za začasne inštalacije, ki so del merilnih, nadzornih in elektroenergetskih sistemov, pomembnih za varnost (na primer pomožna oprema za zagonske preskuse in poskuse ali mobilni napajalni sistemi). Točka 7 je namenjena predvsem za električno izolacijo, točka 8 pa kabliranju in razporeditvi merilnih, nadzornih in elektroenergetskih sistemov, pomembnih za varnost.
Ta dokument se uporablja za merilne, nadzorne in elektroenergetske sisteme novih jedrskih elektrarn ter za te sisteme v obstoječih elektrarnah, ki jih je treba nadgraditi ali vgraditi. Za obstoječe elektrarne glej 1.2 in 5.4.
Če neodvisnost zahtevajo splošni varnostni standardi, kot so varnostni priročniki IAEA, IEC 61513 (za merilne in nadzorne sisteme), IEC 63046 (za elektroenergetske sisteme) ter druge omejitve projekta, je mogoče to neodvisnost doseči s fizično ločitvijo in električno izolacijo sistemov ter njihove opreme, ki opravljajo varnostne funkcije. Ta dokument opredeljuje potrebne ocene in tehnične zahteve, ki jih je treba izpolnjevati za merilne, nadzorne in elektroenergetske sisteme, opremo ali kable, ki jih je treba ločiti. Na ta način se ustrezno fizično loči in električno izolira redundantne razdelke sistema ter sisteme višjega in nižjega razreda. Ločevanje je potrebno za preprečitev ali zmanjšanje negativnega vpliva na varnost pri napakah in okvarah, ki bi se lahko razširile ali vplivale na več delov sistema ali več sistemov.
Zahteve za neodvisnost funkcij in z njimi povezanih sistemov ter opreme so običajno podrobno opredeljene v projektni dokumentaciji; metoda določanja in opredelitve teh zahtev ni predmet tega dokumenta.
V skladu z zahtevo 21 IAEA SSR-2/1 so sredstva ločevanja fizična ločitev, električna izolacija, funkcionalna neodvisnost in neodvisnost komunikacije. V tem dokumentu se obravnava fizična ločitev in električna izolacija. Funkcionalna neodvisnost in neodvisnost komunikacije v tem dokumentu nista upoštevani. Podrobnosti o funkcionalni neodvisnosti, neodvisnosti od nadzornih sistemov in neodvisnosti komunikacije so v dodatku D.

General Information

Status
Published
Publication Date
11-Aug-2019
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
05-Jul-2019
Due Date
09-Sep-2019
Completion Date
12-Aug-2019

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SLOVENSKI STANDARD
SIST EN IEC 60709:2019
01-september-2019
Nadomešča:
SIST EN 60709:2010
Jedrske elektrarne - Merilna, nadzorna in elektroenergetska oprema za
zagotavljanje varnosti - Ločevanje (IEC 60709:2018)

Nuclear power plants - Instrumentation, control and electrical power systems important

to safety - Separation (IEC 60709:2018)
Kernkraftwerke - Leittechnik und elektrische Energieversorgungssysteme mit
sicherheitstechnischer Bedeutung - Physikalische und elektrische Trennung (IEC
60709:2018)

Centrales nucléaires de puissance - Systèmes d'instrumentation, de contrôle-commande

et d'alimentation électrique importants pour la sûreté - Séparation (IEC 60709:2018)

Ta slovenski standard je istoveten z: EN IEC 60709:2019
ICS:
27.120.20 Jedrske elektrarne. Varnost Nuclear power plants. Safety
SIST EN IEC 60709:2019 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN IEC 60709:2019
---------------------- Page: 2 ----------------------
SIST EN IEC 60709:2019
EUROPEAN STANDARD EN IEC 60709
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2019
ICS 27.120.20 Supersedes EN 60709:2010
English Version
Nuclear power plants - Instrumentation, control and electrical
power systems important to safety - Separation
(IEC 60709:2018)

Centrales nucléaires de puissance - Systèmes Kernkraftwerke - Leittechnik und elektrische

d'instrumentation, de contrôle-commande et d'alimentation Energieversorgungssysteme mit sicherheitstechnischer

électrique importants pour la sûreté - Séparation Bedeutung - Physikalische und elektrische Trennung

(IEC 60709:2018) (IEC 60709:2018)

This European Standard was approved by CENELEC on 2019-06-17. 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

© 2019 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN IEC 60709:2019 E
---------------------- Page: 3 ----------------------
SIST EN IEC 60709:2019
EN IEC 60709:2019 (E)
European foreword

This document (EN IEC 60709:2019) consists of the text of IEC 60709:2018 prepared by IEC/SC

45A: "Instrumentation, control and electrical power systems of nuclear facilities", of IEC/TC 45:

"Nuclear instrumentation".
The following dates are fixed:
• latest date by which this document has to be (dop) 2020-06-17
implemented at national level by publication of an
identical national standard or by endorsement
• latest date by which the national standards (dow) 2022-06-17
conflicting with this document have to be
withdrawn
This document supersedes EN 60709:2010.

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.

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.

Endorsement notice

The text of the International Standard IEC 60709:2018 was approved by CENELEC as a European

Standard without any modification.
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SIST EN IEC 60709:2019
EN IEC 60709:2019 (E)
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 When 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 60071 series Insulation co-ordination EN 60071 series
IEC 60332 series Tests on electric and optical fibre cables EN 60332 series
under fire conditions
IEC 60364-4-41 - Low-voltage electrical installations - Part 4-HD 60364-4-41 -
41: Protection for safety - Protection
against electric shock
IEC 60364-5-52 - Low-voltage electrical installations - Part 5-HD 60364-5-52 -
52: Selection and erection of electrical
equipment - Wiring systems
IEC 60364-5-56 - Low-voltage electrical installations - Part 5-- -
56: Selection and erection of electrical
equipment - Safety services
IEC 60909 series Short-circuit current calculation in three- - -
phase a.c. systems
IEC 60964 - Nuclear power plants - Control rooms - - -
Design
IEC 61000 series Electromagnetic compatibility (EMC) - -
IEC 61226 - Nuclear power plants - Instrumentation EN 61226 -
and control important to safety -
Classification of instrumentation and
control functions
IEC 61439-1 - Low-voltage switchgear and controlgear EN 61439-1 -
assemblies - Part 1: General rules
IEC 61500 - Nuclear power plants - Instrumentation - -
and control important to safety - Data
communication in systems performing
category A functions
IEC 61513 2011 Nuclear power plants - Instrumentation EN 61513 2013
and control important to safety - General
requirements for systems
IEC 61660 series Short-circuit currents in d.c. auxiliary EN 61660 series
installations in power plants and
substations
IEC 62003 - Nuclear power plants - Instrumentation - -
and control important to safety -
Requirements for electromagnetic
compatibility testing
---------------------- Page: 5 ----------------------
SIST EN IEC 60709:2019
EN IEC 60709:2019 (E)
IEC 62808 - Nuclear power plants - Instrumentation EN 62808 -
and control systems important to safety -
Design and qualification of isolation
devices
IEC/TR 62096 - Nuclear power plants - Instrumentation - -
and control - Guidance for the decision on
modernization
IEC 63046 - Nuclear power plants - Electrical systems - - -
General requirements
IAEA Safety 2016 Safety of Nuclear Power Plant: Design
Standard Series No.
SSR-2/1
IAEA Safety Guide - Safety classification of structures, systems
SSG-30 and components in Nuclear Power Plants
IAEA Safety Guide - Design of electrical power systems in
SSG-34 Nuclear Power Plants
IAEA Safety Guide 2016 Design of instrumentation and control
SSG-39 systems in Nuclear Power Plants
To be published.
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SIST EN IEC 60709:2019
IEC 60709
Edition 3.0 2018-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Nuclear power plants – Instrumentation, control and electrical power systems
important to safety – Separation
Centrales nucléaires de puissance – Systèmes d’instrumentation, de contrôle-
commande et d'alimentation électrique importants pour la sûreté – Séparation
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.120.20 ISBN 978-2-8322-5582-7

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
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SIST EN IEC 60709:2019
– 2 – IEC 60709:2018  IEC 2018
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope ............................................................................................................................ 10

1.1 General ................................................................................................................. 10

1.2 Application: new and pre-existing plants ............................................................... 10

2 Normative references .................................................................................................... 11

3 Terms and definitions .................................................................................................... 12

4 Abbreviated terms ......................................................................................................... 15

5 Principles and requirements for separation .................................................................... 16

5.1 Principles .............................................................................................................. 16

5.1.1 General ......................................................................................................... 16

5.1.2 Separation reasoning and boundaries ............................................................ 16

5.1.3 Plant safety principles and requirements ....................................................... 17

5.2 Safety class separation requirements .................................................................... 17

5.3 Associated circuits ................................................................................................ 18

5.3.1 General ......................................................................................................... 18

5.3.2 Criteria .......................................................................................................... 19

5.4 Separation issues at existing plants ...................................................................... 20

5.4.1 General ......................................................................................................... 20

5.4.2 Criteria .......................................................................................................... 20

6 Separation design basis ................................................................................................ 20

6.1 Design inputs ........................................................................................................ 20

6.2 Environmental conditions and hazards .................................................................. 21

6.2.1 General ......................................................................................................... 21

6.2.2 Environmental conditions ............................................................................... 21

6.2.3 External hazards............................................................................................ 21

6.2.4 Internal hazards ............................................................................................. 21

6.2.5 Fire protection ............................................................................................... 22

6.3 EMI/EMC .............................................................................................................. 22

6.4 Electrical fault ....................................................................................................... 22

6.5 Requirements from non-nuclear technical standards ............................................. 22

6.6 Requirements from special operating conditions ................................................... 22

7 Electrical isolation ......................................................................................................... 23

7.1 Principles .............................................................................................................. 23

7.1.1 General ......................................................................................................... 23

7.1.2 Overvoltage barrier ........................................................................................ 23

7.1.3 Short circuit / Overcurrent protection ............................................................. 23

7.1.4 Electrical nonreactive (retroaction free) ......................................................... 24

7.1.5 Galvanic isolation (electrical insulation) ......................................................... 24

7.2 Isolation devices ................................................................................................... 24

7.2.1 General ......................................................................................................... 24

7.2.2 Isolation characteristics ................................................................................. 25

7.2.3 Actuation priority ........................................................................................... 25

8 Physical separation ....................................................................................................... 26

8.1 Principles .............................................................................................................. 26

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SIST EN IEC 60709:2019
IEC 60709:2018  IEC 2018 – 3 –

8.1.1 General ......................................................................................................... 26

8.1.2 Separation by distance .................................................................................. 26

8.1.3 Structural separation ..................................................................................... 26

8.2 Separation of cables and cable support structures ................................................ 26

8.2.1 General ......................................................................................................... 26

8.2.2 Divisional separation of redundant cables and cable support structures ......... 27

8.2.3 Separation of system cables and cable supporting structures of different

safety classes ................................................................................................ 27

8.2.4 Separation of signal cables from power cables .............................................. 28

8.2.5 Reduced separation distances ....................................................................... 28

8.2.6 Associated circuits ......................................................................................... 28

8.2.7 Separation of cables from tubes or pipes ....................................................... 28

8.2.8 General routing considerations ...................................................................... 28

8.2.9 Identification .................................................................................................. 28

8.3 Separation of components inside the I&C and electrical system important to

safety .................................................................................................................... 28

8.3.1 Divisional separation of redundant components inside the I&C and

electrical system important to safety .............................................................. 28

8.3.2 Separation of components of different safety classes .................................... 29

8.3.3 Installation of equipment of different voltage levels ........................................ 29

8.3.4 Reduced separation distances ....................................................................... 29

8.3.5 Associated circuits ......................................................................................... 30

8.3.6 Separation of components from sources of hazards ....................................... 30

8.4 Control room cabinets, desks, panels and related cables ...................................... 30

9 Verification .................................................................................................................... 31

Annex A (normative) Relation to IAEA guidelines and IEC 61226 ......................................... 32

A.1 Object of this Annex .............................................................................................. 32

A.2 Applicability of this document ................................................................................ 32

A.3 IAEA Guidelines, applicable for this document ...................................................... 32

A.4 IEC standards, applicable for the safety categorization and classification ............. 32

A.5 Defence in Depth levels, simplified definitions ....................................................... 33

Annex B (informative) Examples of separation realizations .................................................. 34

B.1 Object of this Annex .............................................................................................. 34

B.2 Example of physical separation ............................................................................. 34

B.2.1 General ......................................................................................................... 34

B.2.2 Examples of physical separation by distance ................................................. 34

B.2.3 Examples of physical separation by structure ................................................ 36

B.3 Example of electrical isolation ............................................................................... 37

B.3.1 General ......................................................................................................... 37

B.3.2 Examples of overvoltage barriers ................................................................... 37

B.3.3 Examples of short circuit / overcurrent protection .......................................... 38

B.3.4 Examples of galvanic isolation ....................................................................... 39

B.4 Example of EMC protection ................................................................................... 40

B.5 Associated circuits ................................................................................................ 41

Annex C (informative) Examples of design errors and I&C and electrical failure events ........ 43

C.1 Object of this Annex .............................................................................................. 43

C.2 Design errors ........................................................................................................ 43

C.3 I&C and electrical system failure events ................................................................ 43

C.3.1 General ......................................................................................................... 43

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SIST EN IEC 60709:2019
– 4 – IEC 60709:2018  IEC 2018

C.3.2 Single random failure ..................................................................................... 43

C.3.3 Multiple failures from a single common cause ................................................ 43

Annex D (informative) Functional independence and independence of communication ......... 44

D.1 Object of this Annex .............................................................................................. 44

D.2 Functional independence ...................................................................................... 44

D.2.1 General ......................................................................................................... 44

D.2.2 Independence from control system ................................................................ 44

D.3 Independence of communication ........................................................................... 45

Bibliography .......................................................................................................................... 46

Figure 1 – Physical separation by structure or distance ........................................................ 17

Figure 2 – Separation by electrical isolation .......................................................................... 17

Figure 3 – Electrical Isolation measures and selection of components .................................. 23

Figure B.1 – Separation of cable supporting structures by distance ...................................... 35

Figure B.2 – Separation of cable trays by distance................................................................ 35

Figure B.3 – Separation by structures ................................................................................... 36

Figure B.4 – Overvoltage barriers in I&C systems ................................................................. 37

Figure B.5 – Overvoltage protection in electrical systems ..................................................... 38

Figure B.6 – Short circuit protection in case of a cross-connection ........................................ 39

Figure B.7 – Galvanic isolation in I&C systems ..................................................................... 39

Figure B.8 – Galvanic isolation in electrical systems ............................................................. 40

Figure B.9 – EMC protection of I&C cables ........................................................................... 41

Figure B.10 – Examples of associated circuits ...................................................................... 42

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SIST EN IEC 60709:2019
IEC 60709:2018  IEC 2018 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
NUCLEAR POWER PLANTS –
INSTRUMENTATION, CONTROL AND ELECTRICAL
POWER SYSTEMS IMPORTANT TO SAFETY – SEPARATION
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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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.

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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

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services carried out by independent certification bodies.

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 60709 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 2004. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:

a) include requirements referring to the separation principle in electrical systems important to

safety;
b) define separation criteria for I&C and electrical systems in a generic way;
c) restructure the standard following the criteria;

d) consider interferences between I&C and electrical equipment from different safety

classes;
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SIST EN IEC 60709:2019
– 6 – IEC 60709:2018  IEC 2018

e) align with the new revisions of IAEA documents and broaden the scope to include other

aspects of separation;

f) cover new technologies that either present unique separation issues or provide new

means of achieving separation;

g) enhance requirements and guidance for areas of cable congestion, e.g. control room,

cable spreading galleries, etc;

h) introduce the concept of “associated circuits” (from US practice) to deal with equipment

not important to safety and cables that are not separated from safety equipment and

cables;

i) address the implications of low energy circuits, such as the possible use of analysis to

reduce the minimum separation distance;
j) review existing requirements, update terminology and definitions;
k) provide guidance for the application of the standard to existing plants.
The text of this International Standard is based on the following documents:
FDIS Report on voting
45A/1185/FDIS 45A/1195/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: 12 ----------------------
SIST EN IEC 60709:2019
IEC 60709:2018  IEC 2018 – 7 –
INTRODUCTION
a) Background, main issues and organization of the standard

I&C and electrical systems important to safety in nuclear power plants need to tolerate the

effects of plant / equipment faults as well as internal and external hazards. Various

techniques are available to increase the level of tolerability of I&C and electrical systems to

such effects, including the provision of independent systems, subsystems and equipment. For

claims to be made of independence b
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