IEC 60255-27:2023

Measuring relays and protection equipment - Part 27: Product safety requirements

IEC 60255-27:2023 specifies the product safety requirements for measuring relays and protection equipment having a rated AC voltage up to 1 000 V, or a rated DC voltage up to 1 500 V. This document specifies essential safety requirements to minimize the risk of fire and hazards caused by electric shock or injury to the user and property. This document specifies only product safety requirements; functional performance of the equipment is not covered. This document covers all the ways in which the equipment can be mounted and used in cabinets, racks and panels. This document also applies to auxiliary devices such as shunts, series resistors, transformers, auxiliary control panels, display devices, etc., that are used in conjunction with measuring relays and protection equipment and are tested together.

Relais de mesure et dispositifs de protection - Partie 27: Exigences de sécurité des produits

L'IEC 60255-27:2023 spécifie les exigences de sécurité des produits pour les relais de mesure et les dispositifs de protection avec une tension assignée en courant alternatif inférieure ou égale à 1 000 V ou avec une tension assignée en courant continu inférieure ou égale à 1 500 V. Le présent document spécifie les exigences de sécurité fondamentales pour réduire le plus possible les risques d'incendie et de dangers causés par un choc électrique ou les risques de blessure de l'utilisateur et de dégradation matérielle. Le présent document spécifie uniquement les exigences de sécurité des produits; les performances fonctionnelles du matériel ne sont pas couvertes. En revanche, le présent document couvre tous les modes qui peuvent être utilisés pour le montage et l'utilisation du dispositif dans des baies, des racks ou des panneaux. Le présent document s'applique aussi aux dispositifs auxiliaires comme les shunts, résistances série, transformateurs, panneaux de commande auxiliaires, dispositifs d'affichage, etc., qui sont utilisés conjointement avec les relais de mesure et les dispositifs de protection et sont soumis à l'essai ensemble.

General Information

• Status: Published
• Publication Date: 06-Feb-2023
• ICS: 29.120.70 - Relays
• Technical Committee: TC 95 - Measuring relays and protection equipment
• Drafting Committee: MT 3 - TC 95/MT 3
• Current Stage: PPUB - Publication issued
• Start Date: 27-Jan-2023
• Completion Date: 07-Feb-2023

Relations

• Revises: IEC 60255-27:2013 - Measuring relays and protection equipment - Part 27: Product safety requirements
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 60255-27 ®
Edition 3.0 2023-02
COMMENTED VERSION
INTERNATIONAL
STANDARD
colour
inside
Measuring relays and protection equipment –
Part 27: Product safety requirements
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Secretariat Tel.: [phone]
3, rue de Varembé [e-mail]
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Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

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IEC 60255-27 ®
Edition 3.0 2023-02
COMMENTED VERSION
INTERNATIONAL
STANDARD
colour
inside
Measuring relays and protection equipment –
Part 27: Product safety requirements
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.120.70 ISBN 978-2-8322-6472-0

– 2 – IEC 60255-27:2023 CMV © IEC 2023
CONTENTS
FOREWORD .8
INTRODUCTION . 11

1 Scope . 12
2 Normative references . 13
3 Terms and definitions . 14
4 General safety requirements.
4.1 General .
4.2 Earthing requirements.
4 Protection against electric shock . 26
5.1 General .
Introductory remark .
4.1 Protection from contact with hazardous-live-parts . 27
4.1.1 General . 27
4.1.2 Insulation . 27
4.1.3 Equipment case enclosure and barriers . 27
4.1.4 Hazardous live terminations using stranded wire . 28
Discharge of capacitors .
4.2 Protective impedance . 29
4.3 Accessible parts . 30
4.3.1 General . 30
4.3.2 Determination of accessible parts . 30
4.3.3 Permissible limits for accessible parts . 31
4.4 Bonding to the protective conductor Earthing and protective bonding
requirements . 32
4.4.1 General . 32
4.4.2 Insulation between live parts and accessible conductive parts. 33
4.4.3 Protective bonding . 33
4.5 Functional earthing earthed circuits . 34
4.6 Protective conductor connection. 34
4.7 High leakage current . 34
4.8 Solid insulation . 35
4.8.1 General . 35
4.8.2 Requirements . 35
4.9 Clearances and creepage distances . 35
4.9.1 General . 35
4.9.2 Clearances . 36
4.9.3 Creepage distances . 37
4.10 Single fault conditions . 38
4.10.1 Testing in single fault condition . 38
4.10.2 Application of single fault condition . 38
4.10.3 Duration of tests . 40
4.10.4 Compliance . 40
5 Mechanical aspects . 41
5.1 Protection against mechanical hazards . 41
5.1.1 Stability . 41

5.1.2 Moving parts . 41
5.1.3 Edges and corners . 42
5.2 Mechanical requirements . 42
5.3 Mechanical security of terminations . 42
6 Flammability and resistance to fire. 42
6.1 General . 42
6.2 Requirements for protection against the spread of fire . 42
6.3 General hazards from overheating and fire . 45
6.3.1 Equipment Surface temperature limits for protection against burns . 45
6.3.2 Hazardous gases and chemicals . 46
6.4 Minimization of fire risk . 46
6.4.1 General . 46
6.4.2 Eliminating or reducing the sources of ignition within the equipment . 47
6.5 Cabling and fusing . 47
6.6 Flammability of materials and components . 48
6.6.1 General . 48
6.6.2 Materials for components and other parts inside fire enclosures . 48
6.6.3 Materials for fire enclosures . 49
6.6.4 Materials for components and other parts outside fire enclosures . 49
6.7 Fire ignition sources . 50
6.8 Conditions for a fire enclosure. 50
6.8.1 Parts requiring a fire enclosure . 50
6.8.2 Parts not requiring a fire enclosure. 50
6.9 Requirements for primary circuits and circuits exceeding ELV limits
Fire enclosures and flame barriers . 51
6.9.1 General . 51
6.9.2 Fire enclosures and flame barrier requirements . 51
6.10 Assessment of the fire risk due to a single fault condition . 54
6.10.1 Guidelines for maximum acceptable temperatures when subjecting a
circuit or component to a single fault condition . 54
6.10.2 Temperature of windings under normal condition use or a single fault
condition . 54
6.10.3 Compliance Conformity of equipment with requirements for protection
against the spread of fire . 55
6.11 Limited-energy circuit . 55
7 General and fundamental design requirements for safety . 56
7.1 Climatic conditions for safety . 56
7.2 Electrical connections . 56
7.3 Components . 57
7.3.1 General . 57
7.3.2 High-integrity part or component . 57
8.4 Connection to telecommunication networks .
7.4 Connection to other equipment. 58
7.5 Laser High-intensity light sources . 58
7.6 Explosion . 58
7.6.1 General . 58
7.6.2 Components at risk of explosion . 58
8 Marking, documentation and packaging . 59
8.1 Marking . 59

– 4 – IEC 60255-27:2023 CMV © IEC 2023
8.1.1 General . 59
8.1.2 Identification . 59
8.1.3 Auxiliary supplies, VT, CT, I/O (Input/Output) measurands, inputs and
outputs . 60
8.1.4 Fuses . 61
8.1.5 Measuring circuit terminals . 62
8.1.6 Terminals and operating devices . 62
8.1.7 Equipment protected by double or reinforced insulation .
...

IEC 60255-27 ®
Edition 3.0 2023-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Measuring relays and protection equipment –
Part 27: Product safety requirements
Relais de mesure et dispositifs de protection –
Partie 27: Exigences de sécurité des produits
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.
Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite ni
utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie et
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About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.
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Stay up to date on all new IEC publications. Just Published
containing more than 22 300 terminological entries in English
details all new publications released. Available online and once
and French, with equivalent terms in 19 additional languages.
a month by email.
Also known as the International Electrotechnical Vocabulary
(IEV) online.
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IEC 60255-27 ®
Edition 3.0 2023-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Measuring relays and protection equipment –
Part 27: Product safety requirements
Relais de mesure et dispositifs de protection –
Partie 27: Exigences de sécurité des produits
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.120.70 ISBN 978-2-8322-6322-8
– 2 – IEC 60255-27:2023 © IEC 2023
CONTENTS
FOREWORD . 7
INTRODUCTION . 9
1 Scope . 10
2 Normative references . 10
3 Terms and definitions . 12
4 Protection against electric shock . 20
4.1 Protection from contact with hazardous-live-parts . 20
4.1.1 General . 20
4.1.2 Insulation . 21
4.1.3 Equipment enclosure and barriers . 21
4.1.4 Hazardous live terminations using stranded wire . 22
4.2 Protective impedance. 22
4.3 Accessible parts. 23
4.3.1 General . 23
4.3.2 Determination of accessible parts . 23
4.3.3 Permissible limits for accessible parts . 24
4.4 Earthing and protective bonding requirements . 25
4.4.1 General . 25
4.4.2 Insulation between live parts and accessible conductive parts . 25
4.4.3 Protective bonding . 26
4.5 Functional earthed circuits . 26
4.6 Protective conductor connection . 27
4.7 High leakage current . 27
4.8 Solid insulation . 27
4.8.1 General . 27
4.8.2 Requirements . 28
4.9 Clearances and creepage distances . 28
4.9.1 General . 28
4.9.2 Clearances . 28
4.9.3 Creepage distances . 29
4.10 Single fault conditions . 30
4.10.1 Testing in single fault condition . 30
4.10.2 Application of single fault condition . 30
4.10.3 Duration of tests . 32
4.10.4 Compliance . 32
5 Mechanical aspects . 33
5.1 Protection against mechanical hazards . 33
5.1.1 Stability . 33
5.1.2 Moving parts . 33
5.1.3 Edges and corners . 34
5.2 Mechanical requirements . 34
5.3 Mechanical security of terminations . 34
6 Flammability and resistance to fire . 34
6.1 General . 34
6.2 Requirements for protection against the spread of fire . 34
6.3 General hazards from overheating and fire . 36

6.3.1 Surface temperature limits for protection against burns . 36
6.3.2 Hazardous gases and chemicals . 36
6.4 Minimization of fire risk . 36
6.4.1 General . 36
6.4.2 Eliminating or reducing the sources of ignition within the equipment . 37
6.5 Cabling and fusing . 37
6.6 Flammability of materials and components . 37
6.6.1 General . 37
6.6.2 Materials for components and other parts inside fire enclosures . 38
6.6.3 Materials for fire enclosures . 38
6.6.4 Materials for components and other parts outside fire enclosures . 39
6.7 Fire ignition sources. 39
6.8 Conditions for a fire enclosure . 40
6.8.1 Parts requiring a fire enclosure . 40
6.8.2 Parts not requiring a fire enclosure . 40
6.9 Fire enclosures and flame barriers . 41
6.9.1 General . 41
6.9.2 Fire enclosures and flame barrier requirements . 41
6.10 Assessment of the fire risk due to a single fault condition . 43
6.10.1 Guidelines for maximum acceptable temperatures when subjecting a
circuit or component to a single fault condition . 43
6.10.2 Temperature of windings under normal use or a single fault condition . 43
6.10.3 Conformity of equipment with requirements for protection against the

spread of fire . 43
6.11 Limited-energy circuit . 44
7 General and fundamental design requirements for safety . 45
7.1 Climatic conditions for safety . 45
7.2 Electrical connections . 45
7.3 Components . 45
7.3.1 General . 45
7.3.2 High-integrity part or component . 45
7.4 Connection to other equipment .
...