IEC 60228:2023

IEC 60228 ®
Edition 4.0 2023-12
COMMENTED VERSION
INTERNATIONAL
STANDARD
colour
inside
Conductors of insulated cables
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IEC 60228 ®
Edition 4.0 2023-12
COMMENTED VERSION
INTERNATIONAL
STANDARD
colour
inside
Conductors of insulated cables
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.060.20 ISBN 978-2-8322-8003-4
– 2 – IEC 60228:2023 CMV  IEC 2023
CONTENTS
FOREWORD .4
INTRODUCTION .7
1 Scope .8
2 Normative references .8
3 Terms and definitions .8
4 Classification .9
5 Materials.9
5.1 Introduction General .9
5.2 Circular and shaped solid aluminium conductors .9
5.3 Circular and shaped stranded aluminium conductors . 10
6 Solid conductors and stranded conductors . 10
6.1 Solid conductors (class 1) . 10
6.1.1 Construction . 10
6.1.2 Resistance . 10
6.2 Stranded circular non-compacted conductors (class 2) . 10
6.2.1 Construction . 10
6.2.2 Resistance . 11
6.3 Stranded compacted circular conductors and stranded shaped conductors
(class 2) . 11
6.3.1 Construction . 11
6.3.2 Resistance . 11
6.4 Milliken conductors (class 2) . 11
6.4.1 Construction . 11
6.4.2 Resistance . 11
7 Flexible conductors (classes 5 and 6) . 11
7.1 Construction . 11
7.2 Resistance . 12
8 Check of compliance with Clause 6 and Clause 7 . 12
Annex A (normative) Measurement of resistance . 17
Annex B (informative) Exact formulae for the temperature correction factors . 19
Annex C (informative) Guidance on the dimensional limits of circular conductors . 20
C.1 Object Purpose . 20
C.2 Dimensional limits for circular copper conductors . 20
C.3 Dimensional limits for stranded compacted circular copper, aluminium and
aluminium alloy conductors . 20
C.4 Dimensional limits for circular solid aluminium conductors . 20
Bibliography . 24
List of comments . 25

Table 1 – Tensile strength limits for circular and shaped solid aluminium conductors.9
Table 2 – Tensile strength limits for circular and shaped stranded aluminium
conductors . 10
Table 3 – Class 1 solid conductors for single-core and multi-core cables . 13
Table 4 – Class 2 stranded conductors for single-core and multi-core cables . 14
Table 5 – Class 5 flexible copper conductors for single-core and multi-core cables . 15

Table 6 – Class 6 flexible copper conductors for single-core and multi-core cables . 16
Table A.1 – Temperature correction factors k for conductor resistance to correct the
t
measured resistance at t °C to 20 °C . 18
Table C.1 – Maximum diameters of solid, non-compacted stranded and flexible circular
copper conductors . 21
Table C.2 – Minimum and maximum diameters of stranded compacted circular copper,
aluminium and aluminium alloy conductors. 22
Table C.3 – Minimum and maximum diameters of solid circular aluminium conductors . 23

– 4 – IEC 60228:2023 CMV  IEC 2023
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CONDUCTORS OF INSULATED CABLES

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 this end and
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preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
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Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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6) All users should ensure that they have the latest edition of this publication.
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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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
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the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
This commented version (CMV) of the official standard IEC 60228:2023 edition 4.0 allows
the user to identify the changes made to the previous IEC 60228:2004 edition 3.0.
Furthermore, comments from IEC TC 20 experts are provided to explain the reasons of
the most relevant changes, or to clarify any part of the content.
A vertical bar appears in the margin wherever a change has been made. Additions are in
green text, deletions are in strikethrough red text. Experts' comments are identified by a
blue-background number. Mouse over a number to display a pop-up note with the
comment.
This publication contains the CMV and the official standard. The full list of comments is
available at the end of the CMV.

IEC 60228 has been prepared by IEC technical committee 20: Electric cables. It is an
International Standard.
This fourth edition cancels and replaces the third edition published in 2004. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) a description of Milliken conductors has been added;
b) nominal cross-sectional areas above 2 500 mm have been added;
c) the old 2 500 mm aluminium resistance value has been corrected and a new value
introduced.
For legacy systems where the 2 500 mm aluminium conductor was designed taking into
account the value presented in previous editions and no longer tabulated, then the original
design can be maintained and still utilized.
The suppliers can furthermore utilize such superseded design of 2 500 mm aluminium
conductors either in systems already designed and qualified but not delivered or for example
to produce repair and additional spare lengths for delivered systems.
The choice of utilizing the original superseded design of 2 500 mm aluminium conductors
or a new one based on the new resistance tabulated value is a matter of agreement between
the supplier and final users.
The text of this International Standard is based on the following documents:
Draft Report on voting
20/2125/FDIS 20/2131/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
– 6 – IEC 60228:2023 CMV  IEC 2023
Conductors described in IEC 60228 are specified in metric sizes. Canada at present uses
conductor sizes and characteristics according to the American Wire Gauge (AWG) system and
kcmil for larger sizes as shown below. The use of these sizes is currently prescribed uniformly
across Canada for installations by sub-national regulations. IEC TC 20 cable product standards
do not prescribe cables with AWG/kcmil conductors. 1
AWG kcmil
Nominal Nominal Nominal Nominal
Conductor cross- Conductor cross- Conductor cross- Conductor cross-
size sectional size sectional size sectional size sectional
area area area  area
2 2 2 2
mm mm mm mm
- - - - 250 127 750 380
- - - - 300 152 800 405
20 0,519 4 21,2 350 177 900 456
18 0,823 3 26,7 400 203 1000 507
16 1,31 2 33,6 450 228 1200 608
14 2,08 1 42,4 500 253 1250 633
12 3,31 1/0 53,5 550 279 1500 760
10 5,26 2/0 67,4 600 304 1750 887
8 8,37 3/0 85,0 650 329 2000 1010
6 13,3 4/0 107 700 355 - -
IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

INTRODUCTION
This document is intended as a fundamental reference standard for IEC technical committees
and National Committees in drafting standards for electric cables, and to the National
Committees in drafting specifications for use in their own countries. These committees should
select from the tables of this general standard the conductors appropriate to the particular
applications with which they are concerned relevant to them and either include the applicable
details in their cable specifications or make appropriate references to this document.
In preparing this edition the main objects have been to incorporate IEC 60228A into it and
maintain a simplified yet informative standard so far as is compatible with technical and
economic considerations.
– 8 – IEC 60228:2023 CMV  IEC 2023
CONDUCTORS OF INSULATED CABLES

1 Scope
This document specifies the nominal cross-sectional areas, in the range 0,5 mm to 2 500 3
500 mm , for conductors in electric power cables and cords of a wide range of types.
Requirements for numbers and sizes of wires and resistance values are also included. These
conductors include solid, stranded and Milliken, copper, aluminium and aluminium alloy
conductors in cables for fixed installations and flexible copper conductors.
This document does not apply to conductors for telecommunication purposes.
The applicability of this document to a particular type of cable is as specified in the standard
for the type of cable.
Unless specified otherwise in a particular clause, this document relates to the conductors in
the finished cable and not to the conductor as made or supplied for inclusion into a cable.
Conductors described in this document are specified in metric sizes.
Informative annexes provide supplementary information covering temperature correction
factors for resistance measurement (Annex B) and guidance on dimensional limits of circular
conductors (Annex C).
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.
IECEE OD-5014, Instrument Accuracy Limits
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
metal-coated
coated with a thin layer of suitable metal, such as tin or tin alloy
3.2
nominal cross-sectional area
value that identifies a particular size of conductor but is not subject to direct measurement
Note 1 to entry: Each particular size of conductor in this document is required to meet a maximum resistance value.

3.3
Milliken conductor
stranded conductor comprising an assembly of shaped conductors, lightly insulated from each
other 2
4 Classification
The conductors have been divided into four classes, 1, 2, 5 and 6. Those in classes 1 and 2
are intended for use in cables for fixed installations. Classes 5 and 6 are intended for use in
flexible cables and cords but may can also be used for fixed installations.
• class 1: solid conductors;
• class 2: stranded conductors;
• class 5: flexible conductors;
• class 6: flexible conductors which are more flexible made with smaller diameter wires than
class 5 for the same nominal conductor cross-section.
5 Materials
5.1 Introduction General
The wires of conductors shall consist of one of the following (except for the Milliken central
element):
• plain or metal-coated annealed copper;
• aluminium or aluminium alloy. 3 4
The wires of stranded conductors (for example Milliken conductors) can be oxidized or
enamelled.
5.2 Circular and shaped solid aluminium conductors
Circular and shaped solid aluminium conductors shall be made from aluminium such that the
tensile strength of the completed conductor is within the limits given in Table 1.
Table 1 – Tensile strength limits for circular
and shaped solid aluminium conductors
Nominal cross-sectional area Tensile strength
2 2
mm N/mm
10 and 16 110 to 165
25 and 35 60 to 130
50 60 to 110
70 and above 60 to 90
NOTE The values given above are not applicable to aluminium alloy conductors.
There are no limits defined for the tensile strength of aluminium alloy solid conductors.

– 10 – IEC 60228:2023 CMV  IEC 2023
5.3 Circular and shaped stranded aluminium conductors
Stranded aluminium conductors shall be made from aluminium such that the tensile strength of
the individual wires is within the limits given in Table 2:
Table 2 – Tensile strength limits for circular
and shaped stranded aluminium conductors
Nominal cross-sectional area Tensile strength
2 2
mm N/mm
10 up to 200
16 and above 125 to 205
NOTE 1 The values given above are not applicable to aluminium alloy conductors.
There are no limits defined for the tensile strength of aluminium alloy stranded conductors.
NOTE 2 This data can only be checked on wires taken before stranding and not on wires taken
from a stranded conductor.
6 Solid conductors and stranded conductors
6.1 Solid conductors (class 1)
6.1.1 Construction
a) Solid conductors (class 1) or conductor wires shall consist of one of the materials specified
in Clause 5.
b) Solid copper conductors shall be of circular cross-section.
NOTE Solid copper conductors having nominal cross-sectional areas of 25 mm and above are for particular
types of cable, e.g. mineral insulated, and not for general purposes.
2 2
c) Solid aluminium and solid aluminium alloy conductors of sizes 10 mm to 35 mm shall be
of circular cross-section. Larger sizes shall be of circular cross-section for single-core
cables and may be of either circular or shaped cross-section for multi-core cables.
6.1.2 Resistance
The resistance of each conductor at 20 ºC, when determined in accordance with Clause 8, shall
not exceed the appropriate maximum value given in Table 3.
NOTE For solid aluminium alloy conductors, having the same nominal cross-sectional area as
an aluminium conductor, the resistance value given in Table 3 should be multiplied by a factor
of 1,162 unless otherwise agreed between the manufacturer and the purchaser.
6.2 Stranded circular non-compacted conductors (class 2)
6.2.1 Construction
a) Stranded circular non-compacted conductors (class 2) shall consist of one of the materials
specified in Clause 5.
b) Stranded aluminium or aluminium alloy conductors shall have a cross-sectional area not
.
less than 10 mm
c) The wires in each conductor shall all have the same nominal diameter.
d) The number of wires in each conductor shall be not less than the appropriate minimum
number given in Table 4.
6.2.2 Resistance
The resistance of each conductor at 20 °C, when determined in accordance with Clause 8, shall
not exceed the appropriate maximum value given in Table 4.
6.3 Stranded compacted circular conductors and stranded shaped conductors
(class 2)
6.3.1 Construction
a) Stranded compacted circular conductors and stranded shaped conductors (class 2) shall
consist of one of the materials specified in Clause 5. Stranded compacted circular aluminium
or aluminium alloy conductors shall have a nominal cross-sectional area not less than
10 mm . Stranded compacted circular copper conductors shall have a nominal
cross-sectional area not less than 1,5 mm . Stranded shaped copper, aluminium or
aluminium alloy conductors shall have a nominal cross-sectional area of not less than
25 mm .
b) The ratio of the diameters of two different wires in the same conductor shall not exceed 2,
except for conductors made with pre-shaped wires.
c) The number of wires in each conductor shall be not less than the appropriate minimum
number given in Table 4, except for conductors made with pre-shaped wires. This
requirement applies to conductors made with wires of circular cross-section before
compaction.
NOTE This requirement applies to conductors made with wires of circular cross-section before compaction and not
to conductors made with pre-shaped wires.
6.3.2 Resistance
The resistance of each conductor at 20 °C, when determined in accordance with Clause 8, shall
not exceed the appropriate maximum value given in Table 4.
6.4 Milliken conductors (class 2)
6.4.1 Construction
a) Milliken conductors (class 2) shall consist of any of the materials specified in Clause 5.
Milliken conductors shall have a nominal cross-sectional area not less than 800 mm , and
the minimum number of wires for each cross section is not specified. 5
b) The ratio of the diameters of two different wires of any segment shall not exceed 2 (Milliken
central element excluded).
c) The Milliken central element can be empty, with a solid conductor, wires or with a plastic
filler.
d) This conductor may be constructed from 4, 5, or 6 equal segments. The number of wires in
each segment is defined by the manufacturer. In the case of a central element formed with
wires, it can be considered as an additional segment with a polygonal shape.
6.4.2 Resistance
The resistance of the whole conductor at 20 °C, for all different constructions described in 6.4.1,
when determined in accordance with Clause 8, shall not exceed the appropriate maximum value
given in Table 4.
7 Flexible conductors (classes 5 and 6)
7.1 Construction
a) Flexible conductors (classes 5 and 6) shall consist of plain or metal-coated annealed copper.
b) The wires in each conductor shall have the same nominal diameter.

– 12 – IEC 60228:2023 CMV  IEC 2023
c) The diameter of the wires in each conductor shall not exceed the appropriate maximum
value given in Table 5 for class 5 or Table 6 for class 6 conductors.
7.2 Resistance
The resistance of each conductor at 20 °C, when determined in accordance with Clause 8, shall
not exceed the appropriate maximum value given in Table 5 or Table 6.
8 Check of compliance with Clause 6 and Clause 7
Compliance with the requirements for construction of 6.1.1, 6.2.1, 6.3.1, 6.4.1 and 7.1 shall be
checked on the completed cable by inspection and measurement where practicable.
Compliance with the requirements for resistance given in 6.1.2, 6.2.2, 6.3.2, 6.4.2, and 7.2 shall
be checked by measurement in accordance with Annex A and corrected for temperature by the
factors in Table A.1.
Table 3 – Class 1 solid conductors for single-core and multi-core cables
1 2 3 4
Nominal cross- Maximum resistance of conductor at 20 ºC
sectional area
Circular, annealed copper conductors Aluminium and
aluminium alloy
Plain Metal-coated
conductors, circular or
c
shaped
Ω/km Ω/km Ω/km
mm
0,5 36,0 36,7 -
0,75 24,5 24,8 -
1,0 18,1 18,2 -
1,5 12,1 12,2 -
2,5 7,41 7,56 -
4 4,61 4,70 -
6 3,08 3,11 -
a
10 1,83 1,84
3,08
a
16 1,15 1,16
1,91
b a
25 -
0,727 1,20
b a
35 -
0,524 0,868
b
50 - 0,641
0,387
b
70 - 0,443
0,268
b d
95 -
0,193 0,320
b d
120 -
0,153 0,253
b d
150 -
0,124 0,206
b d
185 -
0,101 0,164
b d
240 -
0,077 5 0,125
b d
300 -
0,062 0 0,100
b
400 - 0,077 8
0,046 5
500 - - 0,060 5
630 - - 0,046 9
800 - - 0,036 7
1 000 - - 0,029 1
1 200 - - 0,024 7
1 400 - - 0,021 2
1 600 - - 0,018 6
a 2 2
Aluminium conductors 10 mm to 35 mm circular only; see 6.1.1 c).
b
See note in 6.1.1 b).
c
See note in 6.1.2.
d
For single-core cables, four sectoral shaped conductors may be assembled into a single circular conductor.
The maximum resistance of the assembled conductor shall be 25 % of that of the individual component
conductors.
– 14 – IEC 60228:2023 CMV  IEC 2023
Table 4 – Class 2 stranded conductors for single-core and multi-core cables 6
1 2 3 4 5 6 7 8 9 10
Minimum number of wires in the conductor Maximum resistance of conductor at 20 °C
Nominal
cross-
Circular Aluminium or
Circular Shaped Annealed copper conductor
sectional
compacted aluminium alloy
area
b
conductor
Cu Al Cu Al Cu Al Plain wires Metal-coated
wires
Ω/km Ω/km Ω/km
mm
0,5 7 - - - - - 36,0 36,7 -
0,75 7 - - - - - 24,5 24,8 -
1,0 7 - - - - - 18,1 18,2 -
1,5 7 - 6 - - - 12,1 12,2 -
2,5 7 - 6 - - - 7,41 7,56 -
4 7 - 6 - - - 4,61 4,70 -
6 7 - 6 - - - 3,08 3,11 -
10 7 7 6 6 - - 1,83 1,84 3,08
16 7 7 6 6 - - 1,15 1,16 1,91
25 7 7 6 6 6 6 0,727 0,734 1,20
35 7 7 6 6 6 6 0,524 0,529 0,868
50 19 19 6 6 6 6 0,387 0,391 0,641
70 19 19 12 12 12 12 0,268 0,270 0,443
95 19 19 15 15 15 15 0,193 0,195 0,320
120 37 37 18 15 18 15 0,153 0,154 0,253
150 37 37 18 15 18 15 0,124 0,126 0,206
185 37 37 30 30 30 30 0,099 1 0,100 0,164
240 37 37 34 30 34 30 0,075 4 0,076 2 0,125
300 61 61 34 30 34 30 0,060 1 0,060 7 0,100
400 61 61 53 53 53 53 0,047 0 0,047 5 0,077 8
500 61 61 53 53 53 53 0,036 6 0,036 9 0,060 5
630 91 91 53 53 53 53 0,028 3 0,028 6 0,046 9
800 91 91 53 53 - - 0,022 1 0,022 4 0,036 7
1 000 91 91 53 53 - - 0,017 6 0,017 7 0,029 1
b
1 200 0,0151 0,0151 0,0247
1 200 91 91 53 53 - - 0,015 1 0,015 1 0,024 7
a b
1 400 0,0129 0,0129 0,0212
a
91 91 53 53 - - 0,012 9 0,012 9 0,021 2
1 400
b
1 600 0,0113 0,0113 0,0186
1 600 91 91 53 53 - - 0,011 3 0,011 3 0,018 6
a b
- 0,010 1 0,010 1 0,016 5
1 800
b
2 000 - 0,009 0 0,009 0 0,014 9
b
2 500 - 0,007 2 0,007 2 0,01270,011 9
a
- 0,006 0 0,006 0 0,009 9
3 000
3 200 - 0,005 6 0,005 6 0,009 3
a
- 0,005 1 0,005 1 0,008 5
3 500
1 2 3 4 5 6 7 8 9 10
a
These sizes are non-preferred. Other non-preferred sizes are recognized for some specialized applications but
are not within the scope of this document. 7
b
The minimum number of wires for these sizes is not specified. These sizes may be constructed from 4, 5 or 6
equal segments (Milliken).
b
For stranded aluminium alloy conductors having the same nominal cross-sectional area as an aluminium
conductor the resistance value should be agreed between the manufacturer and the purchaser.

Table 5 – Class 5 flexible copper conductors for single-core and multi-core cables
1 2 3 4
Nominal cross- Maximum diameter of Maximum resistance of conductor at 20 °C
sectional area wires in conductor
Plain wires Metal-coated wires
mm Ω/km Ω/km
mm
0,5 0,21 39,0 40,1
0,75 0,21 26,0 26,7
1,0 0,21 19,5 20,0
1,5 0,26 13,3 13,7
2,5 0,26 7,98 8,21
4 0,31 4,95 5,09
6 0,31 3,30 3,39
10 0,41 1,91 1,95
16 0,41 1,21 1,24
25 0,41 0,780 0,795
35 0,41 0,554 0,565
50 0,41 0,386 0,393
70 0,51 0,272 0,277
95 0,51 0,206 0,210
120 0,51 0,161 0,164
150 0,51 0,129 0,132
185 0,51 0,106 0,108
240 0,51 0,080 1 0,081 7
300 0,51 0,064 1 0,065 4
400 0,51 0,048 6 0,049 5
500 0,61 0,038 4 0,039 1
630 0,61 0,028 7 0,029 2
– 16 – IEC 60228:2023 CMV  IEC 2023
Table 6 – Class 6 flexible copper conductors for single-core and multi-core cables
1 2 3 4
Nominal cross- Maximum diameter of Maximum resistance of conductor at 20 °C
sectional area wires in conductor
Plain wires Metal-coated wires
mm Ω/km Ω/km
mm
0,5 0,16 39,0 40,1
0,75 0,16 26,0 26,7
1,0 0,16 19,5 20,0
1,5 0,16 13,3 13,7
2,5 0,16 7,98 8,21
4 0,16 4,95 5,09
6 0,21 3,30 3,39
10 0,21 1,91 1,95
16 0,21 1,21 1,24
25 0,21 0,780 0,795
35 0,21 0,554 0,565
50 0,31 0,386 0,393
70 0,31 0,272 0,277
95 0,31 0,206 0,210
120 0,31 0,161 0,164
150 0,31 0,129 0,132
185 0,41 0,106 0,108
240 0,41 0,080 1 0,081 7
300 0,41 0,064 1 0,065 4
Annex A
(normative)
Measurement of resistance
The cable shall be kept in the test area for a sufficient time to ensure that the conductor
temperature has reached a level which permits an accurate determination of resistance using
the correction factors provided.
Measure the DC resistance of the conductor(s), either on a complete length of cable or flexible
cord or on a sample of cable of flexible cord of at least 1 m in length, at room temperature and
record the temperature at which the measurement is made. Adjust the measured resistance by
means of the correction factors given in Table A.1.
Calculate the resistance per kilometre length of cable from the length of the complete cable and
not from the length of the individual core or wires.
If necessary, correction to 20 °C and 1 km length shall be made by applying the following
formula:
R = Rk××
20 t t
L
where
k is the temperature correction factor from Table A.1;
t
R is the conductor resistance at 20 °C, in Ω/km;
R is the measured conductor resistance, in Ω;
t
L is the length of the cable, in m.
The expanded measurement uncertainty (k = 2) for R shall be in accordance with
IECEE OD-5014.
– 18 – IEC 60228:2023 CMV  IEC 2023
Table A.1 – Temperature correction factors k for conductor resistance
t
to correct the measured resistance at t °C to 20 °C
1 2 1 2
Temperature of Temperature of
Correction factor  Correction factor
k k
t t
conductor at time of conductor at time of
measurement measurement
All conductors All conductors
t °C t °C
0 1,087 21 0,996
1 1,082 22 0,992
2 1,078 23 0,988
3 1,073 24 0,984
4 1,068 25 0,980
5 1,064 26 0,977
6 1,059 27 0,973
7 1,055 28 0,969
8 1,050 29 0,965
9 1,046 30 0,962
10 1,042 31 0,958
11 1,037 32 0,954
12 1,033 33 0,951
13 1,029 34 0,947
14 1,025 35 0,943
15 1,020 36 0,940
16 1,016 37 0,936
17 1,012 38 0,933
18 1,008 39 0,929
19 1,004 40 0,926
20 1,000
NOTE The values of correction factors are based on a resistance-temperature coefficient of 0,004 per Kelvin
k
t
at 20 °C.
The values of temperature correction factors specified in column 2 are approximate but give practical values well
within the accuracy that can normally be achieved in measurements of conductor temperature and length of cable
or flexible cords.
For more accurate values for the temperature correction factors for copper and aluminium, reference should be
made to Annex B. However, these should not be treated as a requirement for testing in compliance with this
document in the assessment of resistances.

Annex B
(informative)
Exact formulae for the temperature correction factors
a) Annealed copper conductors: plain or metal-coated
254,5 1
k
t,Cu
234,t5 ++1 0,00393()t − 20
b) Aluminium conductors
248 1
k
t,Al
228 ++t 1 0,t00403()− 20
NOTE For aluminium alloys, reference should be made to the manufacturer.
In all the above cases, t refers to the temperature of the conductor at the time of measurement
in degrees Celsius.
==
==
– 20 – IEC 60228:2023 CMV  IEC 2023
Annex C
(informative)
Guidance on the dimensional limits of circular conductors
C.1 Object Purpose
This Annex C is intended as a guide for manufacturers of cables and cable connectors to assist
in ensuring that the conductors and connectors are dimensionally compatible. It gives guidance
on dimensional limits for the following types of conductor included in this document:
a) circular solid conductors, (class 1) of copper, aluminium and or aluminium alloy;
b) circular and compacted circular stranded conductors, (class 2) of copper, aluminium and or
aluminium alloy;
c) flexible conductors, (classes 5 and 6) of copper.
C.2 Dimensional limits for circular copper conductors
The diameters of circular copper conductors should not exceed the values given in Table C.1.
If minimum diameters for class 1 circular copper conductors are needed required, reference
can be made to the minimum diameters for solid circular aluminium or aluminium alloy
conductors indicated in Table C.3.
C.3 Dimensional limits for stranded compacted circular copper, aluminium
and aluminium alloy conductors
The diameters of stranded compacted circular copper, aluminium and aluminium alloy
conductors should not exceed the maximum values and should be not less than the minimum
values given in Table C.2.
In the exceptional case of uncompacted circular stranded aluminium or aluminium alloy
conductors, the maximum diameters should not exceed the corresponding values for copper
conductors given in column 3 of Table C.1.
C.4 Dimensional limits for circular solid aluminium conductors
The diameters of circular solid aluminium and aluminium alloy conductors should not exceed
the maximum values and should be not less than the minimum values given in Table C.3.

Table C.1 – Maximum diameters of solid, non-compacted
stranded and flexible circular copper conductors
1 2 3 4
Nominal Conductors in cables for fixed installations
cross-sectional area
Solid Stranded Flexible conductors
(Class 1) (Class 2) (Classes 5 and 6)
mm mm mm
mm
0,5 0,9 1,1 1,1
0,75 1,0 1,2 1,3
1,0 1,2 1,4 1,5
1,5 1,5 1,7 1,8
2,5 1,9 2,2 2,4
4 2,4 2,7 3,0
6 2,9 3,3 3,9
10 3,7 4,2 5,1
16 4,6 5,3 6,3
a
5,7 6,6 7,8
a
6,7 7,9 9,2
a
7,8 9,1 11,0
a
9,4 11,0 13,1
a
11,0 12,9 15,1
a
12,4 14,5 17,0
a
13,8 16,2 19,0
185 15,4 18,0 21,0
240 17,6 20,6 24,0
300 19,8 23,1 27,0
400 22,2 26,1 31,0
500 - 29,2 35,0
630 - 33,2 39,0
800 - 37,6 -
1 000 - 42,2 -
NOTE The values given for flexible conductors are intended to allow for both class 5 and class 6 conductors.
a
See 6.1.1 b).
– 22 – IEC 60228:2023 CMV  IEC 2023
Table C.2 – Minimum and maximum diameters of stranded compacted
circular copper, aluminium and aluminium alloy conductors
1 2 3
Nominal cross-sectional Stranded compacted circular conductors (Class 2)
area
Minimum diameter Maximum diameter
mm mm
mm
10 3,6 4,0
16 4,6 5,2
25 5,6 6,5
35 6,6 7,5
50 7,7 8,6
70 9,3 10,2
95 11,0 12,0
120 12,3 13,5
150 13,7 15,0
185 15,3 16,8
240 17,6 19,2
300 19,7 21,6
400 22,3 24,6
500 25,3 27,6
630 28,7 32,5
NOTE 1 The dimensional limits of aluminium conductors with cross-sectional areas
above 630 mm are not given as the compaction technology is not generally
established.
NOTE 2 No values are given for compacted copper conductors in the size range
2 2
1,5 mm to 6 mm .
Table C.3 – Minimum and maximum diameters of solid circular aluminium conductors
1 2 3
Nominal cross- Solid conductors (Class 1)
sectional area
Minimum diameter Maximum diameter
mm mm
mm
10 3,4 3,7
16 4,1 4,6
25 5,2 5,7
35 6,1 6,7
50 7,2 7,8
70 8,7 9,4
95 10,3 11,0
120 11,6 12,4
150 12,9 13,8
185 14,5 15,4
240 16,7 17,6
300 18,8 19,8
400 21,2 22,2
500 24,0 25,1
630 27,3 28,4
800 30,9 32,1
1000 34,8 36,0
1200 37,8 39,0
– 24 – IEC 60228:2023 CMV  IEC 2023
Bibliography
IEC Guide 108, Guidelines for ensuring the coherence of IEC publications – Horizontal
functions, horizontal publications and their application

List of comments
1 As IEC TC 20 do not prescribe cables with AWG/kcmil conductors it has been decided to
remove the below table and the paragraph.
See IEC TR 62602 to find AWG/kcmil information.
2 Segmented conductors without lightly insultation between them used for DC applications
are not considered Milliken.
3 Copper coated aluminium is not considered because of possible safety risks, including
possible corrosion of the metals which make them unsuitable for household use.
4 Conductors can be made of aluminium or copper, and only these materials are considered
in order to evaluate the resistance. Additional materials, i.e. lacquers, paint, tapes and
powders are allowed as part of the conductor design to improve characteristics but they
are not covered by this standard.
5 For cross-sections from 800 mm² to 1600 mm² the minimum number of wires indicated in
Table 4 is not applicable to Milliken conductors.
6 Milliken conductors from 800 mm² take the same DC resistance value than circular
conductors.
Circular conductors are considered up to 1600 mm².
7 Preferred sizes follow the Renard series of preferred numbers.
___________
IEC 60228 ®
Edition 4.0 2023-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Conductors of insulated cables

Ames des câbles isolés
– 2 – IEC 60228:2023  IEC 2023
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Classification . 8
5 Materials . 8
5.1 General . 8
5.2 Circular and shaped solid aluminium conductors . 8
5.3 Circular and shaped stranded aluminium conductors . 9
6 Solid conductors and stranded conductors . 9
6.1 Solid conductors (class 1) . 9
6.1.1 Construction . 9
6.1.2 Resistance . 9
6.2 Stranded circular non-compacted conductors (class 2) . 9
6.2.1 Construction .
...