Railway applications - Communication, signalling and processing systems - Safety related electronic systems for signalling

This European standard is applicable to safety-related electronic systems (including subsystems and equipment) for railway signalling applications.
This European standard applies to generic systems (i.e. generic products or systems defining a class of applications), as well as to systems for specific applications.
The scope of this European standard, and its relationship with other CENELEC standards, are shown in Figure 1.
This European standard is applicable only to the functional safety of systems. It is not intended to deal with other aspects of safety such as the occupational health and safety of personnel. While functional safety of systems clearly can have an impact on the safety of personnel, there are other aspects of system design which can also affect occupational health and safety and which are not covered by this European standard.
This European standard applies to all the phases of the life-cycle of a safety-related electronic system, focusing in particular on phases from 5 (architecture and apportionment of system requirements) to 10 (system acceptance) as defined in EN 50126 (all parts).
Requirements for systems which are not related to safety are outside the scope of this European Standard.
This European standard is not applicable to existing systems, subsystems or equipment (i.e. those which had already been accepted prior to the creation of this European standard). However, as far as reasonably practicable, it should be applied to modifications and extensions to existing systems, subsystems and equipment.
This European standard is primarily applicable to systems, subsystems or equipment which have been specifically designed and manufactured for railway signalling applications. It should also be applied, as far as reasonably practicable, to general-purpose or industrial equipment (e.g. power supplies, display screens or other commercial off the shelf items), which is procured for use as part of a safety-related electronic system. As a minimum, evidence should be provided in such cases to demonstrate either
-   that the equipment is not relied on for safety, or
-   that the equipment can be relied on for those functions which relate to safety.
This European standard is aimed at railway duty holders, railway suppliers, and assessors as well as at safety authorities, although it does not define an approval process to be applied by the safety authorities.
(...)

Bahnanwendungen - Telekommunikationstechnik, Signaltechnik und Datenverarbeitungssysteme - Sicherheitsrelevante elektronische Systeme für Signaltechnik

Applications ferroviaires - Systèmes de signalisation, de télécommunications et de traitement - Systèmes électroniques de sécurité pour la signalisation

La présente Norme européenne est applicable aux systèmes électroniques relatifs à la sécurité (en incluant les sous-systèmes et les équipements) pour des applications de signalisation ferroviaire.
La présente Norme européenne s'applique aux systèmes génériques (c'est-à-dire aux produits ou systèmes génériques qui définissent une classe d'applications), ainsi qu'aux systèmes destinés à des applications spécifiques.
Le domaine d'application de la présente Norme européenne, ainsi que ses relations avec les autres normes du CENELEC, sont représentés dans la Figure 1.
La présente Norme européenne est applicable uniquement à la sécurité fonctionnelle des systèmes. Elle n'est pas destinée à traiter d'autres aspects de la sécurité tels que la santé des travailleurs et la sécurité du personnel. Si la sécurité fonctionnelle des systèmes peut avoir un impact sur la sécurité du personnel, la santé et la sécurité des travailleurs peuvent également être affectées par d'autres aspects de la conception du système qui ne sont pas couverts par la présente Norme européenne.
La présente Norme européenne s'applique à toutes les phases du cycle de vie d'un système électronique relatif à la sécurité, et en particulier aux phases 5 (architecture et allocation des exigences du système) à 10 (acceptation du système) telles que définies dans l'EN 50126 (toutes parties).
Les exigences applicables aux systèmes n'ayant pas trait à la sécurité ne relèvent pas du domaine d'application de la présente Norme européenne.
La présente Norme européenne n'est pas applicable aux systèmes, sous-systèmes ou équipements existants (c'est-à-dire ceux qui ont déjà été acceptés avant l'élaboration de la présente Norme européenne). Toutefois, dans la mesure où cela est raisonnablement possible, elle doit être appliquée à des modifications et à des extensions des systèmes, sous-systèmes et équipements existants.
La présente Norme européenne est plutôt applicable aux systèmes, sous-systèmes ou équipements qui ont été spécialement conçus et fabriqués pour des applications de signalisation ferroviaire. Il convient également de l'appliquer, dans la limite du raisonnable, aux équipements généraux ou industriels (par exemple : alimentations, écrans d'affichage ou autres articles disponibles dans le commerce) qui sont utilisés comme partie d'un système électronique relatif à la sécurité. Dans de tels cas, il convient au minimum d'apporter la preuve que :
-   la sécurité ne repose pas sur cet équipement ; ou
-   que les fonctions en relation avec la sécurité peuvent reposer sur cet équipement.
La présente Norme européenne s'adresse aux responsables d'exploitation ferroviaire, aux fournisseurs de matériel ferroviaire et aux chargés d'évaluations ainsi qu'aux autorités de tutelle, bien qu'elle ne définisse pas un processus d'approbation applicable par les autorités de tutelle.
(...)

Železniške naprave - Komunikacijski, signalni in procesni sistemi - Signalno-varnostni elektronski sistemi

Ta evropski standard se uporablja za varnostne elektronske sisteme (vključno s podsistemi in opremo) v železniških signalnih napravah.
Ta evropski standard se uporablja za generične sisteme (tj. generične izdelke ali sisteme, ki določajo razred uporabe), pa tudi za sisteme za posebno uporabo.
Področje uporabe tega evropskega standarda in njegova povezava z drugimi standardi CENELEC sta prikazana na sliki 1.
Ta evropski standard se uporablja samo za funkcionalno varnost sistemov. Ni namenjen obravnavi drugih vidikov varnosti, kot so zdravje in varnost osebja. Funkcionalna varnost sistemov sicer lahko vpliva na varnost osebja, vendar lahko na zdravje in varnost pri delu vplivajo tudi drugi vidiki zasnove sistema, ki niso zajeti v tem evropskem standardu.
Ta evropski standard se uporablja za vse faze življenjskega cikla varnostnega elektronskega sistema in se osredotoča zlasti na faze od 5 (struktura in porazdelitev sistemskih zahtev) do 10 (sprejem sistema), kot določa standard EN 50126 (vsi deli).
Zahteve za sisteme, ki niso povezane z varnostjo, ne spadajo na področje uporabe tega evropskega standarda.
Ta evropski standard se ne uporablja za obstoječe sisteme, podsisteme ali opremo (npr. tiste, ki so bili sprejeti že pred uvedbo tega evropskega standarda). Vendar naj bi se, kolikor je to razumno izvedljivo, uporabljal za spremembe in razširitve obstoječih sistemov, podsistemov ter opreme.
Ta evropski standard se uporablja predvsem za sisteme, podsisteme ali opremo, ki je bila posebej zasnovana in izdelana za uporabo v železniški signalizaciji. Uporabljal naj bi se tudi, kolikor je to razumno izvedljivo, za splošno ali industrijsko opremo (npr. električne napajalnike, prikazovalnike ali druge komercialne artikle), ki se dobavlja za uporabo kot del varnostnega elektronskega sistema. V takšnih primerih naj bi predložili najmanj dokazila, da:
– ne gre za varnostno opremo; ali
– se je mogoče zanesti na opremo pri funkcijah, ki se nanašajo na varnost.
Ta evropski standard je namenjen nosilcem dolžnosti in dobaviteljem v železniškem prometu ter ocenjevalcem in varnostnim organom, čeprav ne določa postopka odobritve, ki ga morajo izvajati varnostni organi.
(...)

General Information

Status
Published In Edit
Public Enquiry End Date
09-Feb-2017
Publication Date
07-Jan-2019
Current Stage
8100 - Objava popravka objave (Adopted Project 1)
Start Date
16-Aug-2022
Due Date
07-Sep-2022

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Železniške naprave - Komunikacijski, signalni in procesni sistemi - Signalno-varnostni elektronski sistemiBahnanwendungen - Telekommunikationstechnik, Signaltechnik und Datenverarbeitungssysteme - Sicherheitsrelevante elektronische Systeme für SignaltechnikApplications ferroviaires - Systèmes de signalisation, de télécommunications et de traitement - Systèmes électroniques de sécurité pour la signalisationRailway applications - Communication, signalling and processing systems - Safety related electronic systems for signalling45.020Železniška tehnika na splošnoRailway engineering in general35.240.60Uporabniške rešitve IT v prometuIT applications in transportICS:Ta slovenski standard je istoveten z:EN 50129:2018SIST EN 50129:2019en01-februar-2019SIST EN 50129:2019SLOVENSKI

STANDARDSIST-TP CLC/TR 50506-1:2007SIST-TP CLC/TR 50506-2:2010SIST EN 50129:2003SIST-TP CLC/TR 50451:20071DGRPHãþD

SIST EN 50129:2019
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 50129
November 2018 ICS 93.100
Supersedes
CLC/TR 50451:2007, CLC/TR 50506-1:2007, CLC/TR 50506-2:2009, EN 50129:2003
English Version

Railway applications - Communication, signalling and processing systems - Safety related electronic systems for signalling

Applications ferroviaires - Systèmes de signalisation, de télécommunications et de traitement - Systèmes électroniques de sécurité pour la signalisation

Bahnanwendungen - Telekommunikationstechnik, Signaltechnik und Datenverarbeitungssysteme - Sicherheitsrelevante elektronische Systeme für Signaltechnik This European Standard was approved by CENELEC on 2018-06-07. 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, 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 © 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN 50129:2018 E SIST EN 50129:2019
EN 50129:2018

Contents Page European foreword ......................................................................................................................................5 Introduction ..................................................................................................................................................7 1 Scope .....................................................................................................................................................8 2 Normative references ...........................................................................................................................9 3 Terms, definitions and abbreviations ..............................................................................................10 3.1 Terms and definitions ................................................................................................................10 3.2 Abbreviations .............................................................................................................................20 4 Overall framework of this standard ..................................................................................................21 5 Requirements for developing safety-related electronic systems ..................................................22 5.1 Introduction ................................................................................................................................22 5.2 The quality management process .............................................................................................23 5.3 The safety management process ..............................................................................................26 6 Requirements for elements following different life cycles ............................................................36 6.1 Introduction ................................................................................................................................36 6.2 Use of pre-existing items ...........................................................................................................36 6.3 Safety-related tools for electronic systems ................................................................................39 6.4 Physical security and IT-Security ...............................................................................................41 7 The Safety Case: structure and content ..........................................................................................42 7.1 The Safety Case structure .........................................................................................................42 7.2 The Technical Safety Report .....................................................................................................44 7.3 Generic and Specific Safety Cases ...........................................................................................55 7.4 Provisions for the Specific Application Safety Case ..................................................................55 7.5 Dependencies between Safety Cases .......................................................................................56 8 System safety acceptance and subsequent phases .......................................................................57 8.1 System safety acceptance process ...........................................................................................57 8.2 Operation, maintenance and performance monitoring ..............................................................61 8.3 Modification and retrofit .............................................................................................................61 8.4 Decommissioning and disposal .................................................................................................61 Annex A (normative)

Safety Integrity Levels ...........................................................................................62 A.1 Introduction ........................................................................................................................................62 A.2 Safety requirements ...........................................................................................................................62 A.3 Safety integrity ....................................................................................................................................63 A.4 Determination of safety integrity requirements ..............................................................................64 A.4.1 General ......................................................................................................................................64 A.4.2 Risk Assessment .......................................................................................................................65 A.4.3 Hazard Control...........................................................................................................................67 SIST EN 50129:2019

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A.4.4 Identification and treatment of new hazards arising from design ..............................................72 A.5 Allocation of SILs ...............................................................................................................................73 A.5.1 General aspects ........................................................................................................................73 A.5.2 Relationship between SIL and associated TFFR ......................................................................74 Annex B (normative)

Management of faults for safety-related functions ............................................77 B.1 Introduction ........................................................................................................................................77 B.2 General concepts ...............................................................................................................................78 B.2.1 Detection and negation times ....................................................................................................78 B.2.2 Composition of two independent items......................................................................................79 B.3 Effects of faults ..................................................................................................................................80 B.3.1 Effects of single faults ...............................................................................................................80 B.3.2 Influences between items ..........................................................................................................81 B.3.3 Detection of single faults ...........................................................................................................87 B.3.4 Action following detection (retention of safe state) ....................................................................90 B.3.5 Effects of multiple faults ............................................................................................................92 B.3.6 Defence against systematic faults .............................................................................................95 Annex C (normative)

Identification of hardware component failure modes ........................................96 C.1 Introduction ........................................................................................................................................96 C.2 General procedure .............................................................................................................................96 C.3 Procedure for integrated circuits ......................................................................................................96 C.4 Procedure for components with inherent physical properties ......................................................97 C.5 General provisions concerning component failure modes ...........................................................97 Annex D (informative)

Example of THR/TFFR/FR apportionment and SIL allocation .......................117 Annex E (normative)

Techniques and measures
for the avoidance of systematic faults

and the control of random and systematic faults ..............................................................................................119 E.1 Introduction ......................................................................................................................................119 E.2 Tables of techniques and measures ..............................................................................................121 Annex F (informative)

Guidance on User Programmable Integrated Circuits ..................................130 F.1 Introduction ......................................................................................................................................130 F.1.1 Purpose ...................................................................................................................................130 F.1.2 Terminology and context .........................................................................................................131 F.2 UPIC life cycle ...................................................................................................................................132 F.2.1 Organization, roles, responsibilities and personnel competencies ..........................................134 F.2.2 UPIC Requirements .................................................................................................................134 F.2.3 UPIC Architecture and Design .................................................................................................135 F.2.4 Logic Component Design ........................................................................................................136 F.2.5 Logic Component Coding ........................................................................................................136 F.2.6 Logic Component Verification ..................................................................................................136 SIST EN 50129:2019

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F.2.7 UPIC Physical Implementation ................................................................................................136 F.2.8 UPIC Integration ......................................................................................................................136 F.2.9 UPIC Validation .......................................................................................................................136 F.2.10 Requirements for use of pre-existing logic components .........................................................136 F.3 Detailed technical requirements for UPIC ......................................................................................136 F.3.1 Guidance on safety architecture ..............................................................................................136 F.3.2 Protection against random faults – architectural principles .....................................................137 F.3.3 Protection against systematic faults – (techniques/measures) ...............................................137 Annex G (informative)

Changes at this document compared to EN 50129:2003 ...............................147 Annex ZZ (informative)

Relationship between this document and the Essential Requirements of EU Directive 2008/57/EC ................................................................................................................................151 Bibliography .............................................................................................................................................153 SIST EN 50129:2019

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European foreword This document (EN 50129:2018) has been prepared by CLC/SC 9XA “Communication, signalling and processing systems” of CLC/TC 9X “Electrical and electronic applications for railways”. The following dates are fixed: • latest date by which this document has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2019-05-23 • latest date by which the national standards conflicting with this document have to be withdrawn (dow) 2021-11-23 This document supersedes EN 50129:2003. CLC/TR 50451:2007, CLC/TR 50506-1:2007 and CLC/TR 50506-2:2009 are withdrawn by the time the present Publication is published. The significant technical changes with respect to EN 50129:2003 are the following: — A better alignment with the life cycle phases described in EN 50126-1:2017 has been made; — Clause 5 describes the requirements that apply to the development of safety-related electronic systems (until phase 9 of the life cycle), — Clause 8 focuses on the requirements for safety acceptance and approval of safety-related electronic systems and subsequent phases; — Requirements and guidance have been added in Clause 6 on the following topics: — reuse of pre-existing systems, — safety-related tools, — impact of IT security threats on functional safety, — specific application safety cases; — Requirements for the structure and content of the safety case are now defined in a dedicated Clause 7; — Annex A has been aligned with EN 50126-2:2017 for the specification and allocation of safety integrity requirements; — The content of former Annex D has been merged with Annex B, and has been changed from informative to normative; — The status of the Annex E has been changed from informative to normative; — An Annex F has been added as an informative annex on User Programmable Integrated Circuits. A more detailed comparison of changes between EN 50129:2003 and this document can be found in Annex G. 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. This document has been prepared under a mandate given to CENELEC by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive(s). SIST EN 50129:2019

EN 50129:2018

For the relationship with EU Directive(s) see informative Annex ZZ, which is an integral part of this document. The structure of this document is described in Clause 4. This document is intended to be used in conjunction with EN 50126-1:2017, “Railway Applications — The Specification and Demonstration of Reliability, Availability, Maintainability and Safety (RAMS) — Part 1: Generic RAMS Process”, EN 50126-2:2017, “Railway Applications — The Specification and Demonstration of Reliability, Availability, Maintainability and Safety (RAMS) — Part 2: Systems Approach to Safety”, and EN 50128:2011, “Railway applications — Communication, signalling and processing systems — Software for railway control and protection systems”. This document has been prepared under the Mandate M/483 given to CENELEC by the European Commission and the Commission Implementing Regulation (EU) No 402/2013 of 30 April 2013 on the common safety method (CSM) for risk evaluation and assessment and repealing Regulation (EC) No 352/2009 (with the subsequent amendment, Commission Implementing Regulation (EU) No 2015/1136 of 13 July 2015). SIST EN 50129:2019

EN 50129:2018

Introduction This document defines requirements for the acceptance of safety-related electronic systems in the railway signalling field. The aim of European railway duty holders and of European railway industry is to develop compatible railway systems based on common standards. Therefore cross-acceptance of Safety Approvals for systems, subsystems or equipment by the different national railway duty holders is necessary. This document is the common European base for safety acceptance of electronic systems for railway signalling applications. Cross-acceptance is aimed at the acceptance of generic products or generic applications that can be used for a number of different specific applications, and not at the acceptance of any single specific application. Public procurement within the European Community concerning safety-related electronic systems for railway signalling applications will refer to this document. This document is concerned with the evidence to be presented for the acceptance of safety-related systems. However, it specifies not only those life cycle activities which need to be completed before the acceptance stage, but also the additional planned activities to be carried out afterwards. In this way, safety justification will cover the whole life cycle. This document is concerned with what evidence is to be presented. Except where considered appropriate, it does not specify who carries out the necessary work, since this can vary in different circumstances. Safety-related electronic systems for signalling include hardware and software aspects. To develop complete safety-related systems, both aspects need to be taken into account throughout the whole life cycle of the system. The requirements for the overall safety-related electronic system and for its hardware aspects are defined in this document. Other requirements are defined in associated CENELEC standards: for safety-related systems which include software, see EN 50128; for safety-related data communication, see EN 50159. This document consists of Clauses 1 to 8, which form the main part, and Annexes A, B, C, D, E, F, G and ZZ. The requirements defined in the main part of this document and in Annexes A, B, C and E are normative, whilst Annexes D, F, G and ZZ are informative. This document is in line with, and uses relevant sections of: — EN 50126-1:2017, Railway Applications — The Specification and Demonstration of Reliability, Availability, Maintainability and Safety (RAMS) — Part 1: Generic RAMS Process, — EN 50126-2:2017, Railway Applications — The Specification and Demonstration of Reliability, Availability, Maintainability and Safety (RAMS) — Part 2: Systems Approach to Safety. This document is based on the system life cycle described in EN 50126-1, EN 50126-2 and is in line with the EN 61508 series. EN 50126-1, EN 50126-2, EN 50128, EN 50129 comprise the railway sector equivalent of the EN 61508 series so far as Railway Communication, Signalling and Processing Systems are concerned. When compliance with these documents has been demonstrated, further evaluation of compliance with the EN 61508 series is not required. SIST EN 50129:2019

EN 50129:2018

1 Scope This document is applicable to safety-related electronic systems (including subsystems and equipment) for railway signalling applications. This document applies to generic systems (i.e. generic products or systems defining a class of applications), as well as to systems for specific applications. The scope of this document, and its relationship with other CENELEC standards, are shown in Figure 1. This document is applicable only to the functional safety of systems. It is not intended to deal with other aspects of safety such as the occupational health and safety of personnel. While functional safety of systems clearly can have an impact on the safety of personnel, there are other aspects of system design which can also affect occupational health and safety and which are not covered by this document. This document applies to all the phases of the life cycle of a safety-related electronic system, focusing in particular on phases from 5 (architecture and apportionment of system requirements) to 10 (system acceptance) as defined in EN 50126-1:2017. Requirements for systems which are not related to safety are outside the scope of this document. This document is not applicable to existing systems, subsystems or equipment which had already been accepted prior to the creation of this document. However, so far as reasonably practicable, it should be applied to modifications and extensions to existing systems, subsystems and equipment. This document is primarily applicable to systems, subsystems or equipment which have been specifically designed and manufactured for railway signalling applications. It should also be applied, so far as reasonably practicable, to general-purpose or industrial equipment (e.g. power supplies, display screens or other commercial off the shelf items), which is procured for use as part of a safety-related electronic system. As a minimum, evidence should be provided in such cases (more information is given in 6.2) to demonstrate either – that the equipment is not relied on for safety, or – that the equipment can be relied on for those functions which relate to safety. This document is aimed at railway duty holders, railway suppliers, and assessors as well as at safety authorities, although it does not define an approval process to be applied by the safety authorities. SIST EN 50129:2019

EN 50129:2018

Figure 1 — Scope of the main CENELEC railway application standards 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. EN 50124-1, Railway applications — Insulation coordination — Part 1: Basic requirements — Clearances and creepage distances for all electrical and electronic equipment EN 50125-1, Railway applications — Environmental conditions for equipment — Part 1: Rolling stock and on-board equipment EN 50125-3, Railway applications — Environmental conditions for equipment — Part 3: Equipment for signalling and telecommunications EN 50126-1:2017, Railway Applications — The Specification and Demonstration of Reliability, Availability, Maintainability and Safety (RAMS) — Part 1: Generic RAMS Process EN 50126-2:2017, Railway Applications — The Specification and Demonstration of Reliability, Availability, Maintainability and Safety (RAMS) — Part 2: Systems Approach to Safety EN 50128, Railway applications — Communication, signalling and processing systems — Software for railway control and protection systems EN 60664-1, Insulation coordination for equipment within low-voltage systems — Part 1: Principles, requirements and tests (IEC 60664-1) SIST EN 50129:2019

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3 Terms, definitions and abbreviations 3.1 Terms and definitions For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• IEC Electropedia: available at http://www.electropedia.org/ • ISO Online browsing platform: available at http://www.iso.org/obp 3.1.1 accident unintended event or series of events that results in death, injury, loss of a system or service, or environmental damage [SOURCE: IEC 60050-821:2017, 821-12-02] 3.1.2 basic integrity integrity attribute for safety-related functions with a TFFR higher than (less demanding) 10−5 h−1 or for non-safety-related functions Note 1 to entry: In this document Basic Integrity requirements relate only to safety-related functions. If a non-safety-related function has been given basic-integrity requirements on the basis of the process described in EN 50126-2:2017, no additional requirements are defined in this document. [SOURCE: EN 50126-1:2017, 3.7, modified – The note 1 to entry has been added.] 3.1.3 causal analysis analysis of the reasons how and why a particular hazard can come into existence [SOURCE: IEC 60050-821:2017, 821-12-07] 3.1.4 common-cause failures failures of multiple items, which would otherwise be considered independent of one another, resulting from a single cause [SOURCE: IEC 60050-192:2015, 192-03-18] 3.1.5 configuration structuring and interconnection of the hardware and software of a system for its intended application [SOURCE: IEC 60050-821:2017, 821-12-12] 3.1.6 consequence analysis analysis of events which are likely to happen after a hazard has occurred [SOURCE: IEC 60050-821:2017, 821-12-14] SIST EN 50129:2019

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3.1.7 cross-acceptance status achieved by a product that has been accepted by one authority to the relevant standards and is acceptable to other authorities without the necessity for further assessment [SOURCE: IEC 60050-821:2017, 821-12-15] 3.1.8 design activity applied in order to analyse and transform specified requirements into acceptable solutions [SOURCE: IEC 60050-821:2017, 821-12-16, modified – The end of the definition “design solutions which have the required safety integrity level” has been replaced by “solutions”.] 3.1.9 diversity existence of two or more different ways or means of achieving a specified objective Note 1 to entry: Diversity is specifically provided as a defence against common cause failure. It can be achieved by providing systems that are physically different from each other or by functional diversity, where similar systems achieve the specified objective in different ways. [SOURCE: IEC 60050-395:2014, 395-07-115] 3.1.10 DC fault model fault category that includes the following failure modes: stuck-at faults, stuck-open, open or high impedance outputs as well as short circuits between signal lines, and for integrated circuits, short circuit between any two connections (pins) SIST EN 50129:2019

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3.1.11 electronic component hardware component electronic device that cannot be taken apart without destruction or impairment of its intended use EXAMPLE: Resistors, capacitors, diodes, integrated circuits, hybrids, application specific integrated circuits, wound components and relays. [SOURCE: IEC 60050-904:2014, 904-01-09, modified – “hardware component” has been added as a synonym.] 3.1.12 equipment single apparatus or set of devices or apparatuses, or the set of main devices of an installation, or all devices necessary to perform a specific task Note 1 to entry: Examples of equipment are a power transformer, the equipment of a substation, measuring equipment. [SOURCE: IEC 60050-151:2001, 151-11-25] 3.1.13 error discrepancy between a computed, observed or measured value or condition and the true, specified or theoretically correct value or condition Note 1 to entry: An error can be caused by a faulty item, e.g. a computing error made by faulty computer equipment. Note 2 to entry: A human error can be seen as a human action or inaction that can produce an unintended result. [SOURCE: IEC 60050-192:2015, 192-03-02] 3.1.14 fail-safe able to enter or remain in a safe state in the event of a failure [SOURCE: IEC 60050-821:2017, 821-01-10] 3.1.15 failure, loss of ability to perform as required N

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