IEC 61666:2010

IEC 61666 ®
Edition 2.0 2010-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
HORIZONTAL STANDARD
NORME HORIZONTALE
Industrial systems, installations and equipment and industrial products –
Identification of terminals within a system

Systèmes industriels, installations et appareils, et produits industriels –
Identification des bornes dans le cadre d’un système

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IEC 61666 ®
Edition 2.0 2010-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
HORIZONTAL STANDARD
NORME HORIZONTALE
Industrial systems, installations and equipment and industrial products –
Identification of terminals within a system

Systèmes industriels, installations et appareils, et produits industriels –
Identification des bornes dans le cadre d’un système

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 01.080.30 ISBN 978-2-88912-148-9
– 2 – 61666 © IEC:2010
CONTENTS
FOREWORD.3
1 Scope.5
2 Normative references .5
3 Terms and definitions .5
4 Terminal designation .7
4.1 General .7
4.2 Designation of terminals with respect to the product aspect.8
4.3 Designation of terminals with respect to the function aspect .9
4.4 Designation of terminals with respect to the location aspect .10
4.5 Terminal designation set .11
5 Classification of terminals.13
Annex A (informative) Examples of terminal designations not specified by a
manufacturer .14
Bibliography.16

Figure 1 – Principle of terminal designation .7
Figure 2 – Example of designation of terminals for a 3-phase squirrel-cage motor .9
Figure 3 – A device shown with function labels on which the terminal designations
related to the function aspect are based, as well as terminal designations (pins) related
to the product aspect .10
Figure 4 – Example of a symbol for a motor starter provided with terminal designations
related to the function aspect.10
Figure 5 – Example of a terminal board for cross-connection where the terminals are
designated related to their location aspect .11
Figure 6 – Example of a terminal designation set.12
Figure 7 – Example of a design with terminal designations related to the function
aspect.12
Figure 8 – Example of an implemented design based on Figure 7 with terminal
designations related to the product aspect.13
Figure 9 – Example of an implemented design based on Figure 7 with terminal
designation sets related to the function and product aspects .13
Figure A.1 – Four terminal blocks composing one terminal assembly (each terminal

block is considered as an object) .14
Figure A.2 – One terminal block with eight terminals (the complete unit is an object) .15
Figure A.3 – One terminal block with eight terminals with two entry points each .15

61666  IEC:2010 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INDUSTRIAL SYSTEMS, INSTALLATIONS
AND EQUIPMENT AND INDUSTRIAL PRODUCTS –
IDENTIFICATION OF TERMINALS WITHIN A SYSTEM

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61666 has been prepared by IEC technical committee 3:
Information structures, documentation and graphical symbols
It has the status of a horizontal standard in accordance with IEC Guide 108.
This second edition cancels and replaces the first edition of IEC 61666 published in 1997.
This edition constitutes a technical revision.
This edition includes the following substantial changes with respect to the previous edition:
 the terminology used in the publication has been adapted to the one used in IEC 81346-1 Ed.2;
 a more comprehensive description of the designation principles is provided;
 additional examples illustrating terminal designations related to the function aspect and
location aspect are provided;
 an additional example illustrating the use of terminal designation sets is provided;
 the former informative Annex A has been turned into a clause in the standard.

– 4 – 61666 © IEC:2010
The text of this standard is based on the following documents:
FDIS Report on voting
3/1001/FDIS 3/1008/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
61666 © IEC:2010 – 5 –
INDUSTRIAL SYSTEMS, INSTALLATIONS
AND EQUIPMENT AND INDUSTRIAL PRODUCTS –
IDENTIFICATION OF TERMINALS WITHIN A SYSTEM

1 Scope
This International Standard establishes general principles for the identificatio
...