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BS EN IEC 60709:2019

BS EN IEC 60709:2019

$198.66

Nuclear power plants. Instrumentation, control and electrical systems important to safety. Separation

Published By Publication Date Number of Pages
BSI 2019 52
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1.1 General

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.

1.2 Application: new and pre-existing plants

This document applies to the I&C and electrical of new nuclear power plants as well as to up-grading or back-fitting of existing plants.

For existing plants, only a subset of requirements is applicable and this subset is normally specified and argued at the beginning of any project.

PDF Catalog

PDF Pages PDF Title
2 undefined
7 English
CONTENTS
10 FOREWORD
12 INTRODUCTION
15 1 Scope
1.1 General
1.2 Application: new and pre-existing plants
16 2 Normative references
17 3 Terms and definitions
20 4 Abbreviated terms
21 5 Principles and requirements for separation
5.1 Principles
5.1.1 General
5.1.2 Separation reasoning and boundaries
22 5.1.3 Plant safety principles and requirements
5.2 Safety class separation requirements
Figures
Figure 1 – Physical separation by structure or distance
Figure 2 – Separation by electrical isolation
23 5.3 Associated circuits
5.3.1 General
24 5.3.2 Criteria
25 5.4 Separation issues at existing plants
5.4.1 General
5.4.2 Criteria
6 Separation design basis
6.1 Design inputs
26 6.2 Environmental conditions and hazards
6.2.1 General
6.2.2 Environmental conditions
6.2.3 External hazards
6.2.4 Internal hazards
27 6.2.5 Fire protection
6.3 EMI/EMC
6.4 Electrical fault
6.5 Requirements from non-nuclear technical standards
6.6 Requirements from special operating conditions
28 7 Electrical isolation
7.1 Principles
7.1.1 General
7.1.2 Overvoltage barrier
7.1.3 Short circuit / Overcurrent protection
Figure 3 – Electrical Isolation measures and selection of components
29 7.1.4 Electrical nonreactive (retroaction free)
7.1.5 Galvanic isolation (electrical insulation)
7.2 Isolation devices
7.2.1 General
30 7.2.2 Isolation characteristics
7.2.3 Actuation priority
31 8 Physical separation
8.1 Principles
8.1.1 General
8.1.2 Separation by distance
8.1.3 Structural separation
8.2 Separation of cables and cable support structures
8.2.1 General
32 8.2.2 Divisional separation of redundant cables and cable support structures
8.2.3 Separation of system cables and cable supporting structures of different safety classes
33 8.2.4 Separation of signal cables from power cables
8.2.5 Reduced separation distances
8.2.6 Associated circuits
8.2.7 Separation of cables from tubes or pipes
8.2.8 General routing considerations
8.2.9 Identification
8.3 Separation of components inside the I&C and electrical system important to safety
8.3.1 Divisional separation of redundant components inside the I&C and electrical system important to safety
34 8.3.2 Separation of components of different safety classes
8.3.3 Installation of equipment of different voltage levels
8.3.4 Reduced separation distances
35 8.3.5 Associated circuits
8.3.6 Separation of components from sources of hazards
8.4 Control room cabinets, desks, panels and related cables
36 9 Verification
37 Annex A (normative) Relation to IAEA guidelines and IEC 61226
A.1 Object of this Annex
A.2 Applicability of this document
A.3 IAEA Guidelines, applicable for this document
A.4 IEC standards, applicable for the safety categorization and classification
38 A.5 Defence in Depth levels, simplified definitions
39 Annex B (informative) Examples of separation realizations
B.1 Object of this Annex
B.2 Example of physical separation
B.2.1 General
B.2.2 Examples of physical separation by distance
40 Figure B.1 – Separation of cable supporting structures by distance
Figure B.2 – Separation of cable trays by distance
41 B.2.3 Examples of physical separation by structure
Figure B.3 – Separation by structures
42 B.3 Example of electrical isolation
B.3.1 General
B.3.2 Examples of overvoltage barriers
Figure B.4 – Overvoltage barriers in I&C systems
43 B.3.3 Examples of short circuit / overcurrent protection
Figure B.5 – Overvoltage protection in electrical systems
44 B.3.4 Examples of galvanic isolation
Figure B.6 – Short circuit protection in case of a cross-connection
Figure B.7 – Galvanic isolation in I&C systems
45 B.4 Example of EMC protection
Figure B.8 – Galvanic isolation in electrical systems
46 B.5 Associated circuits
Figure B.9 – EMC protection of I&C cables
47 Figure B.10 – Examples of associated circuits
48 Annex C (informative) Examples of design errors and I&C and electrical failure events
C.1 Object of this Annex
C.2 Design errors
C.3 I&C and electrical system failure events
C.3.1 General
C.3.2 Single random failure
C.3.3 Multiple failures from a single common cause
49 Annex D (informative) Functional independence and independence of communication
D.1 Object of this Annex
D.2 Functional independence
D.2.1 General
D.2.2 Independence from control system
50 D.3 Independence of communication
51 Bibliography

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BS EN IEC 60709:2019
$198.66