IEC 62502:2010

IEC 62502 ®
Edition 1.0 2010-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Analysis techniques for dependability – Event tree analysis (ETA)

Techniques d’analyse de la sûreté de fonctionnement – Analyse par arbre
d’événement (AAE)
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IEC 62502 ®
Edition 1.0 2010-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Analysis techniques for dependability – Event tree analysis (ETA)

Techniques d’analyse de la sûreté de fonctionnement – Analyse par arbre
d’événement (AAE)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
X
CODE PRIX
ICS 21.020 ISBN 978-2-88912-212-7
– 2 – 62502 © IEC:2010
CONTENTS
FOREWORD.4
INTRODUCTION.6
1 Scope.7
2 Normative references .7
3 Terms, definitions, abbreviations and symbols.7
3.1 Terms and definitions .7
3.2 Abbreviations and symbols.8
3.2.1 Abbreviations .8
3.2.2 Symbols .9
4 General description .9
5 Benefits and limitations of ETA.11
5.1 Benefits.11
5.2 Limitations.11
6 Relationship with other analysis techniques.12
6.1 Combination of ETA and FTA .12
6.2 Layer of protection analysis (LOPA) .13
6.3 Combination with other techniques .13
7 Development of event trees .14
7.1 General .14
7.2 Steps in ETA .14
7.2.1 Procedure.14
7.2.2 Step 1: Definition of the system or activity of interest.15
7.2.3 Step 2: Identification of the initiating events of interest .15
7.2.4 Step 3: Identification of mitigating factors and physical phenomena.16
7.2.5 Step 4: Definition of sequences and outcomes, and their
quantification.16
7.2.6 Step 5: Analysis of the outcomes.17
7.2.7 Step 6: Uses of ETA results.17
8 Evaluation .18
8.1 Preliminary remarks .18
8.2 Qualitative analysis – Managing dependencies.18
8.2.1 General .18
8.2.2 Functional dependencies .19
8.2.3 Structural or physical dependencies .20
8.3 Quantitative analysis .22
8.3.1 Independent sequence of events .22
8.3.2 Fault tree linking and boolean reduction .23
9 Documentation .24
Annex A (informative) Graphical representation .26
Annex B (informative) Examples .27
Bibliography.41

Figure 1 – Process for development of event trees .
Figure 2 – Simple graphical representation of an event tree.18
Figure 3 – Functional dependencies in event trees .20

62502 © IEC:2010 – 3 –
Figure 4 – Modelling of structural or physical dependencies.21
Figure 5 – Sequence of events .22
Figure 6 – Fault tree linking .23
Figure A.1 – Frequently used graphical representation for event trees .26
Figure B.1 – Event tree for a typical fire incident in a diesel generator building.28
Figure B.2 – Simplified event tree for a fire event .29
Figure B.3 – Level-crossing system (LX).31
Figure B.4 – ETA for the level-crossing system.33
Figure B.5 – Simple example .36
Figure B.6 – Fault Tree for the Failure of System 1.36
Figure B.7 – Fault Tree for the Failure of System 2.37
Figure B.8 – Modified event tree .38
Figure B.9 – Event tree with "grouped faults" .39

Table A.1 – Graphical elements .26
Table B.1 – Symbols used in Annex B .29
Table B.2 – System overview.31
Table B.3 – Risk reduction parameters for accidents from Figure B.4 .34

– 4 – 62502 © IEC:2010
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ANALYSIS TECHNIQUES FOR DEPENDABILITY –
EVENT TREE ANALYSIS (ETA)
FOREWORD
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