Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 15: Functional safety requirements for insulation monitoring devices in IT systems and equipment for insulation fault location in IT systems

IEC 61557-15:2014 specifies requirements related to functional safety and is based on the IEC 61508 standard series for the realization of Insulation Monitoring Devices (IMD) as specified in IEC 61557-8 and for Insulation Fault Location Systems (IFLS) according to IEC 61557-9, according to phase 10 of the IEC 61508-1 lifecycle. These devices provide safety related functions for IT systems. This part of IEC 61557 is
- concerned only with functional safety requirements intended to reduce the functional risk during the use of IMDs and IFLSs;
- restricted to risks arising directly from the device itself or from several IMDs or IFLSs working together in a system; and
- intended to define the basic safety functions provided by the devices. This part of IEC 61557 does not
- deal with electrical safety according to IEC 61010-1 and the requirements of IEC 61557-8 and IEC 61557-9;
- cover the hazard and risk analysis of a particular use of the IMD or IFLS;
- identify all the safety functions for the application in which the IMD or IFLS is used; and
- cover the IMD or IFLS manufacturing process. Functional safety requirements depend on the application and should be considered as part of the overall risk assessment of the specific application. The supplier of IMDs and IFLSs is not responsible for the application. The application designer is responsible for the risk assessment and for specifying the overall functional safety requirements of the complete IT system and he should select the functional safety level (SIL) of the IMD and/or IFLS when their safety function is part of the functional safety assessment in the IT system.
This publication is to be read in conjunction with IEC 61557-8:2007 and IEC 61557-9:2009

Sécurité électrique dans les réseaux de distribution basse tension de 1 000 V c.a. et 1 500 V c.c. - Dispositifs de contrôle, de mesure ou de surveillance de mesures de protection - Partie 15: Exigences de sécurité fonctionnelle pour les contrôleurs d'isolement de réseaux IT et les dispositifs de localisation de défauts d'isolement pour réseaux IT

L'IEC 61557-15:2014 spécifie les exigences relatives à la sécurité fonctionnelle; elle se fonde sur la série de normes CEI 61508 pour la réalisation de contrôleurs d'isolement (CPI) tels que spécifiés dans la CEI 61557-8 et de systèmes de localisation de défauts d'isolement (DLD) conformes à la CEI 61557-9 et à la phase 10 du cycle de vie de la CEI 61508-1. Ces dispositifs assurent des fonctions relatives à la sécurité pour des réseaux IT. La présente partie de la CEI 61557
- traite uniquement des exigences de sécurité fonctionnelle visant à réduire le risque fonctionnel lors de l'utilisation des CPI et des DLD;
- se limite aux risques résultant directement du dispositif proprement dit ou de plusieurs dispositifs CPI ou DLD collaborant au sein d'un réseau donné; et
- vise à définir les fonctions de sécurité de base assurées par les dispositifs. La présente partie de la CEI 61557
- ne traite pas de la sécurité électrique selon la CEI 61010-1 et des exigences des normes CEI 61557-8 et CEI 61557-9;
- ne couvre pas l'analyse des dangers et des risques d'un usage particulier de l'CPI ou de l'DLD;
- n'identifie pas toutes les fonctions de sécurité de l'application où l'CPI ou l'DLD est utilisé; et ne couvre pas le processus de fabrication de l'CPI ou de l'DLD. Les exigences de sécurité fonctionnelle dépendent de l'application et il convient d'en tenir compte dans le cadre de l'appréciation globale du risque de l'application spécifique. Le fournisseur des CPI et des DLD n'est pas responsable de l'application qui en est faite. Le concepteur de l'application est responsable de l'appréciation du risque et il lui incombe de spécifier les exigences globales de sécurité fonctionnelle de l'ensemble du réseau IT et il convient qu'il sélectionne le niveau de sécurité fonctionnelle (SIL) de l'CPI et/ou de l'DLD lorsque leur fonction de sécurité fait partie de l'évaluation de la sécurité fonctionnelle du réseau IT.
Cette publication doit être lue conjointement avec la CEI 61557-8:2007 et IEC 61557-9:2009

General Information

Status
Published
Publication Date
11-Feb-2014
Current Stage
PPUB - Publication issued
Start Date
12-Feb-2014
Completion Date
12-Feb-2014
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IEC 61557-15:2014 - Electrical safety in low voltage distribution systems up to 1 000 V a.c. and 1 500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 15: Functional safety requirements for insulation monitoring devices in IT systems and equipment for insulation fault location in IT systems
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IEC 61557-15
Edition 1.0 2014-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical safety in low voltage distribution systems up to 1 000 V a.c. and
1 500 V d.c. – Equipment for testing, measuring or monitoring of protective
measures –
Part 15: Functional safety requirements for insulation monitoring devices in IT
systems and equipment for insulation fault location in IT systems
Sécurité électrique dans les réseaux de distribution basse tension de
1 000 V c.a. et 1 500 V c.c. – Dispositifs de contrôle, de mesure ou de
surveillance de mesures de protection –
Partie 15: Exigences de sécurité fonctionnelle pour les contrôleurs d'isolement
de réseaux IT et les dispositifs de localisation de défauts d'isolement pour
réseaux IT
IEC 61557-15:2014-02(EN-FR)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 61557-15
Edition 1.0 2014-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical safety in low voltage distribution systems up to 1 000 V a.c. and
1 500 V d.c. – Equipment for testing, measuring or monitoring of protective
measures –
Part 15: Functional safety requirements for insulation monitoring devices in IT
systems and equipment for insulation fault location in IT systems
Sécurité électrique dans les réseaux de distribution basse tension de
1 000 V c.a. et 1 500 V c.c. – Dispositifs de contrôle, de mesure ou de
surveillance de mesures de protection –
Partie 15: Exigences de sécurité fonctionnelle pour les contrôleurs d'isolement
de réseaux IT et les dispositifs de localisation de défauts d'isolement pour
réseaux IT
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XC
ICS 17.220.20, 29.080.01, 29.240.01 ISBN 978-2-8322-1406-0

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
---------------------- Page: 3 ----------------------
– 2 – 61557-15 © IEC:2014
CONTENTS

FOREWORD ........................................................................................................................... 6

INTRODUCTION ..................................................................................................................... 8

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

2 Normative references .................................................................................................... 10

3 Terms, definitions and abbreviations ............................................................................. 11

3.1 Terms and definitions ....................................................................................... 11

3.2 Abbreviations ................................................................................................... 22

4 Definition of safety functions embedded in IMDs and IFLSs ........................................... 23

4.1 General ............................................................................................................ 23

4.2 Definition of safety functions ............................................................................ 23

4.2.1 Local insulation warning (LIW) ........................................................ 23

4.2.2 Remote insulation warning (RIW) .................................................... 24

4.2.3 Local location warning (LLW) .......................................................... 24

4.2.4 Remote location warning (RLW)...................................................... 24

4.2.5 Remote enabling / disabling command (REDC) ............................... 25

4.2.6 Local transformer monitoring warning (LTMW) ................................ 25

5 Requirements on products implementing safety-related functions .................................. 25

5.1 Requirement on non-safety-related functions ................................................... 25

5.2 Additional performance requirements for products implementing safety

functions .......................................................................................................... 26

5.2.1 General .......................................................................................... 26

5.2.2 Additional performance requirements for IMDs complying with

SIL 1 or SIL 2 ................................................................................. 26

5.2.3 Additional performance requirements for IFLSs complying with

SIL 1 or SIL 2 ................................................................................. 26

6 Management of functional safety during the development lifecycle ................................ 26

6.1 Management of functional safety for the IT system ........................................... 26

6.2 Use of IMDs and IFLSs in IT systems............................................................... 27

6.3 Safety lifecycle of IMDs and IFLSs in the realisation phase .............................. 27

7 Management of functional safety during the realisation lifecycle of IMDs and

IFLSs............................................................................................................................. 28

7.1 General ............................................................................................................ 28

7.2 IMD and IFL design requirement specification (phase 10.1) ............................. 29

7.2.1 Specification of functional safety requirements ............................... 29

7.2.2 Provisions for the development of safety functions ......................... 29

7.2.3 Verification plan for the development of safety functions ................. 30

7.2.4 Validation plan for the development of safety functions ................... 30

7.2.5 Planning of commissioning, installation and setting into

operation ........................................................................................ 30

7.2.6 Planning of user documentation ...................................................... 31

7.3 IMD and IFLS safety validation planning (phase 10.2) ...................................... 31

7.3.1 General .......................................................................................... 31

7.3.2 Functional safety plan ..................................................................... 31

7.4 IMD and IFLS design and development (phase 10.3) ....................................... 32

7.4.1 General .......................................................................................... 32

7.4.2 Design standards ............................................................................ 32

7.4.3 Realization ..................................................................................... 32

---------------------- Page: 4 ----------------------
61557-15 © IEC:2014 – 3 –

7.4.4 Safety integrity and fault detection .................................................. 32

7.4.5 Safety integrity level (SIL) assignment ............................................ 33

7.4.6 Hardware requirements .................................................................. 33

7.4.7 Software requirements .................................................................... 33

7.4.8 Review of requirements .................................................................. 33

7.4.9 Requirements for the probability of dangerous failure on

demand (PFD) ................................................................................ 34

7.4.10 Failure rate data ............................................................................. 35

7.4.11 Diagnostic test interval ................................................................... 35

7.4.12 Architectural constraints ................................................................. 35

7.4.13 Estimation of safe failure fraction (SFF) .......................................... 37

7.4.14 Requirements for systematic safety integrity ................................... 37

7.5 IMD and IFLS integration (phase 10.4) ............................................................. 40

7.5.1 Hardware integration ...................................................................... 40

7.5.2 Software integration ........................................................................ 40

7.5.3 Modifications during integration ...................................................... 40

7.5.4 Integration tests .............................................................................. 40

7.6 IMD and IFLS documentation related to installation, commissioning,

operation and maintenance procedures (phase 10.5) ....................................... 41

7.6.1 General .......................................................................................... 41

7.6.2 Functional specification .................................................................. 41

7.6.3 Compliance information .................................................................. 41

7.6.4 Information for commissioning, installation, setting into

operation, operation and maintenance ............................................ 41

7.7 IMD and IFLS safety validation (phase 10.6) .................................................... 42

7.7.1 General .......................................................................................... 42

7.7.2 Test ................................................................................................ 42

7.7.3 Verification ..................................................................................... 42

7.7.4 Validation ....................................................................................... 43

7.7.5 EMC requirements .......................................................................... 43

8 Requirements for modifications...................................................................................... 44

8.1 General ............................................................................................................ 44

8.2 Modification request ......................................................................................... 44

8.3 Impact analysis ................................................................................................ 44

8.4 Authorization.................................................................................................... 44

9 Proven in use approach ................................................................................................. 44

Annex A (informative) Risk analysis and SIL assignment for IMDs and IFLSs ...................... 45

A.1 General ............................................................................................................ 45

A.2 SIL assignment for IMDs and IFLSs ................................................................. 47

A.3 Example of risk graph ...................................................................................... 48

A.4 Alternative method of SIL assignment – quantitative method ............................ 49

Annex B (informative) Examples for the determination of PFD, DC and SFF ........................ 50

B.1 General ............................................................................................................ 50

B.2 Examples of IMD and IFLS architectures ......................................................... 51

Annex C (informative) Failure rate databases ...................................................................... 52

C.1 General ............................................................................................................ 52

C.2 Failure rate references in current standards ..................................................... 52

Annex D (informative) Guide to embedded software design and development ...................... 53

D.1 General ............................................................................................................ 53

---------------------- Page: 5 ----------------------
– 4 – 61557-15 © IEC:2014

D.2 Software element guidelines ............................................................................ 53

D.2.1 General .......................................................................................... 53

D.2.2 Interface with system architecture................................................... 53

D.2.3 Software specifications ................................................................... 53

D.2.4 Pre-existent software ...................................................................... 54

D.2.5 Software design .............................................................................. 55

D.2.6 Coding ............................................................................................ 55

D.3 Software development process guidelines ........................................................ 55

D.3.1 Development process: software lifecycle ........................................ 55

D.3.2 Documentation: documentation management .................................. 55

D.3.3 Configuration and software modification management .................... 56

D.3.4 Configuration and archiving management ....................................... 56

D.3.5 Software modifications management ............................................... 57

D.4 Development tools ........................................................................................... 57

D.5 Reproduction of executable code production .................................................... 57

D.6 Software verification and validation .................................................................. 57

D.7 General verification and validation guidelines .................................................. 57

D.8 Verification and validation review ..................................................................... 58

D.9 Software testing ............................................................................................... 58

D.9.1 General validation .......................................................................... 58

D.9.2 Software specification verification: validation tests ......................... 59

D.9.3 Software design verification: software integration tests ................... 59

D.9.4 Detailed design verification: module tests ....................................... 60

Annex E (informative) Information for the assessment of safety functions ............................ 61

E.1 General ............................................................................................................ 61

E.2 Documentation management ............................................................................ 61

E.3 Documentation provided for conformity assessment ......................................... 61

E.4 Documentation of the development lifecycle..................................................... 63

E.5 Design documentation ..................................................................................... 63

E.6 Documentation of verification and validation .................................................... 63

E.7 Test documentation ......................................................................................... 63

E.8 Documentation of modifications ....................................................................... 63

E.9 Information for use ........................................................................................... 63

Annex F (informative) Example of applications ..................................................................... 64

F.1 Overview.......................................................................................................... 64

F.2 Limitation in applications .................................................................................. 64

F.3 Typical applications covered by IEC 61557-15 ................................................. 64

F.3.1 General .......................................................................................... 64

F.3.2 Local alarming ................................................................................ 64

F.3.3 Local transformer monitoring warning ............................................. 65

F.3.4 Alarming and processing of remote insulation warning and/or

remote location warning .................................................................. 66

F.3.5 Automatic disconnection of the complete IT system in case of

a first insulation fault ...................................................................... 67

F.3.6 Automatic disconnection of an IT system sub-network .................... 69

F.3.7 Management of multiple source system (two incomers or of

incomer plus generator) .................................................................. 71

F.3.8 Management of multiple source systems (two incomers or of

incomer plus generator – with a load shedder) ................................ 72

Bibliography .......................................................................................................................... 74

---------------------- Page: 6 ----------------------
61557-15 © IEC:2014 – 5 –

Figure 1 – Relationship between IEC 61557-15 and related standards .................................... 8

Figure 2 – Overall safety lifecycle applicable to an IT system ............................................... 27

Figure 3 – IMD and IFLS safety lifecycle (in realisation phase) ............................................. 28

Figure A.1 – Functional elements of an IT system and their relationship to the

definitions and abbreviations of the IEC 61508 series ........................................................... 45

Figure A.2 – SIL assignment for IMDs and IFLSs .................................................................. 47

Figure A.2 – Example of risk graph ....................................................................................... 48

Figure B.1 – Flowchart for PFD, DC, SFF determination ....................................................... 51

Figure F.1 – Local alarming, based on the systematic presence of one person and

based on a well-defined alarming management process........................................................ 65

Figure F.2 – Local transformer monitoring warning, based on the systematic presence

of a skilled person, and based on a well-defined alarming management process .................. 66

Figure F.3 – Alarming and processing of the remote insulation warning and/or the

remote location warning in a supervisory control system ....................................................... 67

Figure F.4 – Disconnection of the complete IT system in case of insulation fault

detection ............................................................................................................................... 68

Figure F.5 – Threshold 1 warning information and threshold 2 disconnection of the

complete IT system in case of an insulation fault detection ................................................... 69

Figure F.6 – Automatic disconnection of a faulty feeder via direct signal from the IFLS ......... 70

Figure F.7 – Automatic disconnection of a faulty feeder via a PLC ........................................ 71

Figure F.8 – Management of multiple source systems (two incomers or of one incomer

plus generator) ..................................................................................................................... 72

Figure F.9 – Management of multiple source system (two incomers or of one incomer

plus generator, with a load shedder) ..................................................................................... 73

Table 1 – Abbreviations with reference ................................................................................. 22

Table 2 – Safety integrity levels (SIL) and probability of a dangerous failure on

demand (PFD) of IMDs and IFLSs ........................................................................................ 29

Table 3 – Hardware safety integrity: architectural constraints on type A and type B

safety-related subsystems .................................................................................................... 37

Table A.1 – IT system risk analysis ....................................................................................... 46

Table A.3 – Link between minimum risk reduction and SIL .................................................... 48

Table A.4 – Example of classifications according to risk graph Figure A.1 ............................ 49

Table E.1 – Documentation to be provided ............................................................................ 62

---------------------- Page: 7 ----------------------
– 6 – 61557-15 © IEC:2014
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL SAFETY IN LOW VOLTAGE DISTRIBUTION SYSTEMS UP TO
1 000 V AC AND 1 500 V DC – EQUIPMENT FOR TESTING, MEASURING OR
MONITORING OF PROTECTIVE MEASURES –
Part 15: Functional safety requirements for insulation monitoring devices
in IT systems and equipment for insulation fault location in IT systems
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