oSIST prEN IEC 62491:2025

SLOVENSKI STANDARD
01-december-2025
Industrijski sistemi, inštalacije, oprema in industrijski izdelki - Označevanje kablov
in žil
Industrial systems, installations and equipment and industrial products - Labelling of
cables and cores
Industrielle Systeme, Anlagen und Ausrüstungen und Industrieprodukte - Beschriftung
von Kabeln / Leitungen und Adern
Systèmes industriels, installations et appareils et produits industriels - Étiquetage des
câbles et de leurs âmes
Ta slovenski standard je istoveten z: prEN IEC 62491:2025
ICS:
01.110 Tehnična dokumentacija za Technical product
izdelke documentation
29.060.01 Električne žice in kabli na Electrical wires and cables in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

3/1745/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 62491 ED2
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:

2025-10-10 2026-01-02
SUPERSEDES DOCUMENTS:
3/1706/CD, 3/1744/CC
IEC TC 3 : DOCUMENTATION, GRAPHICAL SYMBOLS AND REPRESENTATIONS OF TECHNICAL INFORMATION
SECRETARIAT: SECRETARY:
Sweden Mr Mikael Törnkvist
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):
TC 16,TC 17,TC 44
ASPECTS CONCERNED:
Safety
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft for
Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of which
they are aware and to provide supporting documentation.
Recipients of this document are invited to submit, with their comments, notification of any relevant “In Some Countries”
clauses to be included should this proposal proceed. Recipients are reminded that the CDV stage is the final stage for
submitting ISC clauses. (SEE AC/22/2007 OR NEW GUIDANCE DOC).

TITLE:
Industrial systems, installations and equipment and industrial products - Labelling of cables and cores

PROPOSED STABILITY DATE: 2030
NOTE FROM TC/SC OFFICERS:
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.
You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without
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IEC CDV 62491 © IEC 2025
1 CONTENTS
3 1 Scope . 6
4 2 Normative references . 6
5 3 Terms and definitions . 6
6 4 Rules . 8
7 4.1 General requirements . 8
8 4.2 Use of designated cable cores . 9
9 4.3 Use of additional labelling . 9
10 5 Identification labelling . 10
11 5.1 General . 10
12 6 Connection labelling . 14
13 6.1 General . 14
14 6.2 Local-end connection labelling . 14
15 6.3 Remote-end connection labelling . 15
16 6.4 Both-end connection labelling . 16
17 7 Signal labelling . 16
18 7.1 General . 16
19 7.2 Labelling by signal designation . 16
20 7.3 Labelling of cables for certain designated conductors . 17
21 8 Composite labelling . 18
22 9 Arrangement of additional labelling . 18
23 9.1 General . 18
24 9.2 Relative positions of the labelling . 19
25 9.3 Characters to be used . 19
26 10 Correspondence between labelling and documentation . 20
27 11 Conformance to this standard . 20
28 Annex A Examples of labelling . 21
29 A.1 General . 21
30 A.2 Identification labelling (method R) . 21
31 A.3 Local-end connection labelling (method CL) . 22
32 A.4 Both-end connection labelling (method CB) . 23
33 A.5 Attachment of additional information . 23
34 A.6 Signal labelling (method S) . 24
35 A.7 Composite labelling (method CL+ R) . 25
36 A.8 Use of cable colours (method A) . 25
38 Figure 1 – Example of identification labelling of a single core cable (W23) and of a
39 multi-core cable (W24) in which also the different cores are labelled . 11
40 Figure 2 – Example of identification markings for a control cable (WGA23) and a low-
41 voltage cable (WDB24) . 12
42 Figure 3 – Example of identification labelling of cores where the initial part of the
43 reference designation has been partly omitted . 12
44 Figure 4 – Example of Identification markings for branch cables . 13
45 Figure 5 – Example of local-end connection labelling . 14
46 Figure 6 – Example of remote-end connection labelling for a connection inside a unit . 15
IEC CDV 62491 © IEC 2025
47 Figure 7 – Example of remote-end connection labelling for a cable between different
48 units . 15
49 Figure 8 – Example of both-end connection labelling . 16
50 Figure 9 – Example of local-end connection labelling combined with signal labelling . 18
51 Figure 10 – Example of composite labelling in which both-end connection labelling is
52 used together with identification labelling and signal labelling . 18
53 Figure 11 – Examples of arrangements of labelling on cores or cables. . 19
54 Figure A.1 – Circuit diagram used as a basis for the examples . 21
55 Figure A.2 – Example of identification labelling . 22
56 Figure A.3 – Example of local-end labelling . 23
57 Figure A.4 – Example of both-end connection labelling . 23
58 Figure A.5 – Example of local end connection labelling with additional information . 24
59 Figure A.6 – Example of signal labelling . 25
60 Figure A.7 – Example of composite labelling （CL+R） . 25
61 Figure A.8 – Example where use is made of the cable colours . 26
63 Table 1 – Example of connection table in which the cable cores are identified by
64 means of codes for their colour . 9
65 Table 2 – Connection table corresponding to Figure 1 with labelling . 11
66 Table 3 – Connection table corresponding to Figure 2with labelling . 12
67 Table 4 – Connection table corresponding to Figure 3 with labelling . 13
68 Table 5 – Wiring table corresponding to the markings in Figure 4 . 13
69 Table 6 – Marking of certain designated conductors . 17
70 Table 7 – Methods of labelling defined in this standard . 20
IEC CDV 62491 © IEC 2025
74 INTERNATIONAL ELECTROTECHNICAL COMMISSION
75 ____________
77 INDUSTRIAL SYSTEMS, INSTALLATIONS
78 AND EQUIPMENT AND INDUSTRIAL PRODUCTS –
79 LABELLING OF CABLES AND CORES
82 FOREWORD
83 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all
84 national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation
85 on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other
86 activities, IEC publishes International Standards, Technical Specifications, Technical Reports, Publicly Available
87 Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to technical
88 committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work.
89 International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation.
90 IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions
91 determined by agreement between the two organizations.
92 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international consensus
93 of opinion on the relevant subjects since each technical committee has representation from all interested IEC National
94 Committees.
95 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in
96 that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC
97 cannot be held responsible for the way in which they are used or for any misinterpretation by any end user.
98 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently
99 to the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication
100 and the corresponding national or regional publication shall be clearly indicated in the latter.
101 5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment declared
102 to be in conformity with an IEC Publication.
103 6) All users should ensure that they have the latest edition of this publication.
104 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and members of
105 its technical committees and IEC National Committees for any personal injury, property damage or other damage of any
106 nature whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses arising out of the publicatio n,
107 use of, or reliance upon, this IEC Publication or any other IEC Publications.
108 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable
109 for the correct application of this publication.
110 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights.
111 IEC shall not be held responsible for identifying any or all such patent rights.
112 International Standard IEC 62491 has been prepared by IEC technical committee 3:
113 Documentatíon, graphical symbols and representations of technical information.
114 This second edition cancels and replaces the first edition published in 2008. This edition
115 constitutes a technical revision.
116 This edition includes the following significant texhnical checnges with repest to the previous
117 edition:
118 This edition expands the scope of the standard, and introduces several additions including the
119 definition of connectors, requirements for digital and intermediate markings, and expressions
120 for reference codes of cable types."
121 a) Expand the scope of the standard to include optical cables and optical fibers in Clause 1
122 Scope, and also be suitable for the labeling of other kinds of extended connections.
123 b) Update definition for connectors, and modify the relevant content and example diagrams for
124 connection markings.
125 c) Include requirements for bi-color combinations of insulated conductors.
126 d) Add requirements for digital markings and their placement.
IEC CDV 62491 © IEC 2025
127 e) Update requirements for intermediate markings on cables.
128 f) Add expressions for reference codes of cable types, using the three-letter codes from IEC
129 81346-2 to represent different types of cables, facilitating the intuitive expression of signal
130 information transmitted by the cables through their reference codes.
131 g) Include identification requirements and connection examples for branch cables.
132 h) Modify content caused by modifications to referenced documents, such as the structure of
133 signal designations and marking of certain designated conductors.
134 i) Remove Method 0 "Methods of labelling defined in this standard." from the table 7
135 j) Modify the example of the composite marking method in Appendix A, changing from the
136 composite marking example of identification marking and signal marking (R+S) to the
137 composite marking example of customer-side marking and identification marking (CL+R).
139 The text of this standard is based on the following documents:
FDIS Report on voting
3/XXX/FDIS 3/XXX/RVD
140 Full information on the voting for the approval of this standard can be found in the report on
141 voting indicated in the above table.
142 The language used for the development of this International Standard is English.
143 This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
144 accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, [and the
145 ISO/IEC Directives, JTC 1 Supplement] available at www.iec.ch/members_experts/refdocs. The
146 main document types developed by IEC are described in greater detail at
147 www.iec.ch/publications.
148 For information on the colors applied in this document, see Annex A.
149 The committee has decided that the contents of this document will remain unchanged until the
150 stability date indicated on the IEC web site under webstore.iec.ch in the data related to the
151 specific document. At this date, the document will be
152 • reconfirmed,
153 • withdrawn,
154 • replaced by a revised edition, or
155 • amended.
IEC CDV 62491 © IEC 2025
158 INTRODUCTION
159 Additional labelling of cables and cores might be required within larger systems or installations with many
160 cores of the same colour or with many cables, and where therefore the use of the designations provided
161 by the cable manufacturer only would be ambiguous.
162 Due consideration should be given to the fact that additional labelling will cause additional cost,
163 usually increasing with the number of characters in the labelling string and the number of
164 different labelling elements. The available space may also impose restrictions with regard to
165 the number of characters, their height and the length of the labelling. As a general rule the use
166 of additional labelling should therefore be limited to a necessary minimum and be kept as short
167 as practicable.
168 However, also the advantages and benefits should be taken into considerations in choosing
169 additional labelling of cables and cores.
170 It is important to notice that a single machine or a system has different needs of information in
171 the different phases of its lifecycles (assembling, production, service and maintenance).
172 Additional labelling of cables and cores gives the following advantages:
173 • the possibilities to communicate and identify signals and connections across different involved
174 engineering disciplines and departments like:
175 – process engineering,
176 – software engineering,
177 – electrical engineering,
178 – mechanical/fluid engineering,
179 – control engineering;
180 • minimizing the time used to locate an eventual error (and the reason for it) in the test phase;
181 • saving time when locating an eventual error (and the reason for it) in the service and maintenance
182 phase;
183 • remove the doubt of which core should be connected to which terminal, when replacing components
184 that are placed close to each other;
185 • if used in pre-planning, it gives a clear view for panel-builders, electricians/technicians;
186 service/maintenance and system controllers which will minimize misunderstandings regarding
187 connections.
188 Besides being used in connections between terminal blocks, labelling can also be used when
189 single core cables connect components inside units as: cubicle, pulpit, case, etc.; such methods
190 make possible:
191 • a rapid and secure cabling between the terminals of two objects;
192 • a rapid visual check of cabling, not necessarily looking up in the circuit diagrams;
193 • a correct and secure change of an object during the maintenance operations of plants.
IEC CDV 62491 © IEC 2025
195 INDUSTRIAL SYSTEMS, INSTALLATIONS
196 AND EQUIPMENT AND INDUSTRIAL PRODUCTS –
197 LABELLING OF CABLES AND CORES
201 1 Scope
202 This standard provides rules and guidelines for the labelling of cables and cores/conductors used in
203 industrial installations, equipment and products, in order to maintain a clear relation between the
204 technical documentation and the actual equipment and for other purposes. The following methods
205 are described and designated:
206 • use of coloured cables and designated cores;
207 • additional identification labelling;
208 • additional connection labelling; and
209 • additional signal labelling.
210 This standard is applicable to electric cables and optical fiber cable. However, the methods
211 specified are general and suitable for labelling of other kinds of extended conncetions.
212 The physical design of the labels, the material to be used for the labels as well as cable
213 manufacturers’ product bound marking of cables and cores are not part of this standard.
214 2 Normative references
215 The following referenced documents are indispensable for the application of this document. For
216 dated references, only the edition cited applies. For undated references, the latest edition of
217 the referenced document (including any amendments) applies.
218 IEC 60445, Basic and safety principles for man-machine interface, marking and identification –
219 Identification of equipment terminals ,conductor terminations and conductors
220 IEC 60757, Code for designation of colours
221 IEC 61082-1:2014, Preparation of documents used in electrotechnology – Part 1: Rules
222 IEC 61175-1, Industrial systems, installations and equipment and industrial products –
223 Designation of signals – Part 1: Basic rules
224 IEC 81346-1, Industrial systems, installations and equipment and industrial products –
225 Structuring principles and reference designations – Part 1: Basic rules
226 IEC 81346-2, Industrial systems, installations and equipment and industrial products –
227 Structuring principles and reference designations – Part 2: Classification of objects and codes
228 for classes
229 IEC 61666, Industrial systems, installations and equipment and industrial products –
230 Identification of terminals within a system
231 ISO/IEC 646, Information technology – ISO 7-bit coded character set for information
232 interchange
233 3
IEC CDV 62491 © IEC 2025
234 Terms and definitions
235 For the purposes of this document, the following terms and definitions apply.
236 3.1
237 conductor (of a cable)
238 part of a cable which has the specific function of carrying current
239 [SOURCE: IEC 60050-461:2008, 461-01-01]
240 3.2
241 cable
242 optical fiber cable
243 assembly of one or more conductors and/or optical fibres, with a protective covering and possibly filling,
244 insulating and protective material
245 [SOURCE: IEC 60050-151:2001, 151-12-38，modify]
246 3.3
247 core
248 insulated conductor
249 assembly comprising a conductor with its own insulation (and screens if any)
250 Note 1 to entry: In North American usage, the core of a cable has been defined as the assembly of components of a cable lying
251 under a common covering such as the sheath. Such usage is deprecated.
252 [SOURCE: IEC 60050-461:2008, 461-04-04]
253 3.4
254 connector
255 device used for connecting and disconnecting with appropriate mating parts
256 Note 1 to entry: A connector has one or more contact membe.rs
257 [SOURCE: IEC 60050-151:2001, 151-12-19]
258 3.5
259 terminal
260 conductive part of a device, electric circuit or electric network, provided for connecting that device,
261 electric circuit or electric network to one or more external conductors
262 Note 1 to entry: The term "terminal" is also used for a connection point in circuit theory.
263 [SOURCE: IEC 60050-151:2001, 151-12-12]
264 3.6
265 terminal block
266 assembly of terminals in a housing or body of insulating material to facilitate interconnection between
267 multiple conductors
268 [SOURCE: IEC 60050-581:2008, 581-26-26]
269 3.7
270 terminal designation
271 identifier of a terminal with respect to the object to which it belongs, related to one defined aspect
272 [SOURCE: IEC 61666:2010+AMD1:2021, 3.10]
273 3.8
274 signal designation
275 unambiguous identifier of a signal within a system
276 [SOURCE: IEC 61175-1:2015, 3.6]
IEC CDV 62491 © IEC 2025
277 3.9
278 reference designation
279 identifier of a specific object formed with respect to the system of which the object is a constituent,
280 based on one or more aspects of that system
281 [SOURCE: IEC 81346-1:2022:, 3.11]
282 3.10
283 labelling (of a cable or core)
284 label or labels attached to a cable or core indicating appropriate characteristics
285 3.11
286 identification labelling
287 labelling showing the identifier of an object as a constituent of a specific installation, system, equipment
288 or product
289 3.12
290 connection labelling
291 labelling of a cable or core showing the identifier of the terminal, connector, terminal block or equipment
292 to which it is connected
293 3.13
294 local-end connection labelling
295 system of labelling of cables and cores where the labelling of the end of the cable or core refers to the
296 terminal, connector, terminal block or equipment to which it is connected
297 3.14
298 remote-end connection labelling
299 system of labelling of cables and cores where the labelling of the end of the cable or core refers to the
300 terminal, connector, terminal block or equipment to which the other end of it is connected
301 3.15
302 both-end connection labelling
303 system of labelling of cables and cores where each end of a cable or core is provided with local -end
304 connection labelling and remote-end connection labelling
305 3.16
306 signal labelling
307 system of labelling of cables and cores used as a supplement to other labelling generally based on the
308 signal(s) carried by the cable or core
309 3.17
310 composite labelling
311 system of labelling where two or more of the identification labelling, connection labelling and signal
312 labelling systems are used together
313 4 Rules
314 4.1 General requirements
315 Cables and cores shall be recognizable at each end; it shall be possible to relate cables and
316 cores to the technical documentation.
317 This may be carried out by:
318 • the designation and marking provided by the manufacturer of the cable, see 4.2, or
319 • an additional labelling, see 4.3.
320 Intermediate markings may be applied and their use should be determined by the actual environment of
321 the cable connections.
322 • Generally, when the cables are of the considerable length, multiple intermediate markings should
323 be applied.
IEC CDV 62491 © IEC 2025
324 Additional labelling might be required within larger systems or installations with many cores of
325 the same colour or with many cables, and where therefore the use only of the designations
326 provided by the cable or core manufacturer would be ambiguous.
327 The additional labelling shall be based on one or more of the following:
328 • the identifier of the cable or core, see Clause 5;
329 • the connection of the cable or core, see Clause 6, or
330 • the signal carried by the cable or core, see Clause 7.
331 4.2 Use of designated cable cores
332 Cable cores are often designated by the manufacturer applying methods such as:
333 • coloured insulation of the single cores;
334 • differently coloured (including multi-coloured) insulation of the cores of the cables, or
335 • differently numbered cores of cables.
336 These designations should, to the extent possible, be used for the identification of the cores.
337 Additional labelling is in such cases normally not required.
338 The use of such designations shall be described in the documentation of the equipment in
339 accordance with 7.5 and 9.3 of IEC 61082-1:2014.
340 For the indication of the colours of cable cores in the documentation, the colour coding of
341 IEC 60757 shall be applied.
342 Where there is no risk of confusion, the colours of insulated conductors may use any
343 combination of two colours listed in IEC 60757, except for the colours GREEN and YELLOW.
344 Apart from the bicolour combination GREEN-AND-YELLOW, the colours GREEN and YELLOW
345 shall not be combined with other colours.
346 NOTE The colour does not provide any information on where the core is to be connected. The connection information is in
347 entirety to be found in associated connection table or connection diagram.
348 Table 1 shows an example of a connection table in which the colours (designated in accordance
349 with IEC 60757) of the cable cores are used for the identification
350 Table 1 – Example of connection table in which the cable cores are identified by means of codes
351 for their colour
Core colour Local end Remote end
GNYE A4X1:PE B4X1:PE
BK A4X1:11 B4X1:33
BN A4X1:17 B4X1:34
RD A4X1:18 B4X1:35
357 4.3 Use of additional labelling
358 The additional labelling, where required, shall be one of the following types:
359 • identification labelling of the cable or core, see Clause 5;
360 • connection labelling of the cable or core, see Clause 6:
361 – local-end connection labelling,
362 – remote-end connection labelling,
363 – both-end connection labelling;
364 • signal labelling of the cable or core, see Clause 7.
IEC CDV 62491 © IEC 2025
365 • Composite labelling, see Clause 8.
366 The method used shall be specified in the supporting documentation, see Clause 11.
367 Additional information, for example a reference to a page number of the circuit diagram, may
368 be added on the label. The use of such additional information shall be explained in the technical
369 documentation. For an example, see Clause A.5.
370 In addition to the labelling methods mentioned above, digit
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