oSIST prEN IEC 63559:2026

• Status: Not Published
• Public Enquiry End Date: 29-Nov-2026
• ICS: 29.060.10 - Wires
• ICS: 29.240.20 - Power transmission and distribution lines
• Technical Committee: NVV - Overhead lines and overhead electrical conductors
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 15-Sep-2026
• Due Date: 02-Feb-2027
• Ref Project: prEN IEC 63559:2026 - Concentric lay overhead electrical stranded conductors

• Revises: SIST EN 62219:2002 - Overhead electrical conductors - Formed wire, concentric lay, stranded conductors
• Effective Date: 23-Dec-2025

oSIST prEN IEC 63559:2026 is a CLC draft standard aligned with IEC 63559 for concentric lay overhead electrical stranded conductors. It specifies the designation system, construction requirements, calculation methods, test methods, inspection rules, marking and packaging for overhead conductors made from round or formed conductive wires under IEC 62641 and round wires under IEC 63248.

What does oSIST prEN IEC 63559:2026 specify?

oSIST prEN IEC 63559:2026 covers concentric lay overhead stranded conductors and the rules needed to identify, design, test, deliver and document them. The scope includes conductors made from combinations of the wire types named above and excludes gap-conductors as per IEC 62420.

The document is organized into clauses on scope, references, terms, designation, requirements, property calculations, tests, and packaging and marking. It then adds annexes for the technical datasheet, purchaser information, grease mass, stranding increments, lay ratios, examples of conductor sizes, and operating-temperature guidance.

Annex	What it covers
Annex A	Contents of the technical datasheet
Annex B	Information to be supplied by the purchaser
Annex C	Nominal mass of grease for stranded conductors
Annex D	Calculation method for increments of mass or electrical resistance due to stranding
Annex E	Lay ratios used for calculation of increments due to stranding
Annex F	Examples of conductor sizes and properties
Annex G	Maximum operating temperatures and loss of strength

What are the key requirements of oSIST prEN IEC 63559:2026?

oSIST prEN IEC 63559:2026 sets the rules that make a conductor identifiable, buildable and testable in a consistent way. The most important points are the designation system, the stranding geometry, the limits on joints and surface condition, the calculation methods for conductor properties, the conductor type classification, and the test and packaging rules.

Designation and construction

Clause 4 defines a structured designation that names the envelope material, optional formed-wire identification, core material if present, the section values and the overall diameter. In practice, this lets manufacturers, purchasers and test labs refer to the same conductor without ambiguity.

Clause 5.1 to 5.6 require conductors to be made from the wire types covered by IEC 62641 and IEC 63248, with grease used only when specified. The conductor must be concentrically stranded, with alternating lay directions between layers and a right-hand outer lay unless the order says otherwise. This matters because the lay pattern affects manufacturability, compactness, mechanical stability and electrical performance.

The same clause set also sets geometric expectations: the layers must be evenly and closely stranded, the conductor must show inertness after cutting, and the surface must be free from visible defects that are not consistent with good commercial practice. For a buyer, that means the finished conductor should arrive in a state that can be installed and handled without unusual rework.

Joints, strand properties and classification

Clause 5.7 controls joints, especially in aluminium and steel elements. It limits where joints may appear, requires suitable joint quality and spacing, and ties acceptable joint performance to tensile requirements. In practice, this protects reliability during manufacture and service, since poor joints are a common weak point.

Clause 5.8 and 5.9 explain that some wire properties may be reduced after stranding and that mass and electrical resistance must be adjusted for stranding increments. Annex D gives the calculation method, and Annex E gives the lay ratios used for those calculations. This is important when a datasheet, order or acceptance test depends on final conductor mass or resistance rather than on the wires alone.

Clause 5.10 classifies conductors as Type 0, Type 1 or Type 2 according to the material combination and thermo-mechanical behaviour. That classification drives which operating-temperature assumptions and test expectations apply, so it is a key selection point when specifying conductors for different line duties.

Grease and length control

Clause 5.11 applies when a conductor is greased for corrosion protection. The grease must meet IEC 61394, be applied uniformly, stay in place for storage and service, and be suitable for the expected temperature conditions. For the purchaser, this means grease is not just an optional coating - it is part of the defined product performance.

Clause 5.12 requires length measurement on the complete conductor for each drum with defined accuracy. That matters in ordering and acceptance because delivery length tolerance depends on the measurement method used by the manufacturer.

Calculated properties

Clause 6 gives calculation rules for conductor diameter, cross-sectional area, mass per unit length, RTS (rated tensile strength), elastic modulus, coefficient of linear expansion and DC resistance at 20°C. Annex C supports grease mass calculation, and IEC TR 61597 supports modulus, expansion and increment calculations.

In practice, Clause 6 is the basis for datasheets, technical comparisons, and conformity checks. It tells users how to turn wire data into conductor-level values without relying on ad hoc calculation methods.

Tests, sampling and delivery

Clause 7 separates type tests and sample tests. Type tests verify a new design or a changed process, while sample tests check production lots. The test list covers wire tests, conductor geometry, surface condition, composition, lay ratio, mass, tensile strength, inertness, DC resistance and grease drop point where relevant.

This is the part that links design to production quality. It tells manufacturers what to verify, and it tells purchasers what evidence can be requested for acceptance.

Clause 8 covers packaging and marking. It requires protection in handling and transport, agreed package details, durable identification, and clear marking of the conductor designation, length, weights and whether grease is present. It also sets expectations for random lengths and drum barrel diameter so the conductor is not damaged before installation.

What terms does oSIST prEN IEC 63559:2026 define?

• Conductor - a concentric lay stranded overhead line conductor made of wires that are not insulated from each other and are laid helically in opposite directions.
• Core - the central wire or inner higher-strength layer(s) used as the reinforcing or supporting part of a combined conductor.
• Envelope - the conductive outer layer(s) in a combined conductor, usually made from the more conductive material.
• Lay ratio - the ratio of lay length to the external diameter of the wire layer; it describes how tightly the layer is stranded.
• RTS - rated tensile strength, meaning the calculated breaking load of an unaged conductor based on the tensile properties of its wires.
• Inertness - the property that the wires stay in position after the conductor is cut.
• Type of conductor - the classification into Type 0, Type 1 or Type 2 based on material combination and thermo-mechanical behaviour.

Who uses oSIST prEN IEC 63559:2026?

oSIST prEN IEC 63559:2026 is used by overhead conductor manufacturers, conductor designers, utility specification teams, purchasers, test laboratories and inspection bodies. Manufacturers use it to design the strand build-up, calculate conductor properties and prepare datasheets. Buyers and utilities use it to specify the conductor type, packaging, grease and delivery length, while laboratories use it to check sampling, geometry, resistance, tensile strength and grease performance.

Which standards are used with oSIST prEN IEC 63559:2026?

• IEC 62641 - provides the aluminium and aluminium alloy wire requirements used for the envelope and for formed-wire rules.
• IEC 63248 - provides the coated or cladded metallic wire requirements used for steel and other core-wire options.
• IEC 61394 - sets the grease requirements for greased bare conductors and the performance basis for the grease.
• IEC TR 61597 - provides the calculation methods used for stranded bare conductors, including modulus, expansion and strength-loss guidance.
• IEC 60468 - provides the 4-point method used for direct DC resistance measurement.
• ISO 2176:1995 - provides the method used to determine grease drop point.

What does the oSIST prEN IEC 63559:2026 document contain?

The document contains the conductor designation rules, material and stranding requirements, calculation methods, test methods, packaging and marking rules, and purchaser and datasheet information. It also includes figures showing conductor-section examples and the inertness test, plus tables for lay ratios, allowed joints, property reductions, stranding increments, conductor classification and the test list.

Annex C and Annex D are the main calculation aids for grease mass and stranding increments. Annex F gives worked examples of conductor sizes and properties, which is useful when comparing design options or building technical offers. Annex G explains how operating temperature relates to strength retention over service life.

SLOVENSKI STANDARD
01-november-2026
Koncentrična lega nadzemnih električnih pletenih vrvi
Concentric lay overhead electrical stranded conductor
Ta slovenski standard je istoveten z: prEN IEC 63559:2026
ICS:
29.060.10 Žice Wires
29.240.20 Daljnovodi Power transmission and
distribution lines
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

7/774/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 63559 ED1
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2026-09-11 2026-12-04
SUPERSEDES DOCUMENTS:
7/768/CD, 7/770A/CC
IEC TC 7 : OVERHEAD ELECTRICAL CONDUCTORS
SECRETARIAT: SECRETARY:
China Mr Qiu Zheng
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):
TC 11,TC 122
ASPECTS CONCERNED:
Electricity transmission and distribution
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
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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:
Concentric lay overhead electrical stranded conductors
PROPOSED STABILITY DATE: 2031
NOTE FROM TC/SC OFFICERS:
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proposed that TC 7 Members (National Committees) submit their comments by end of October so that the Convenor/
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IEC CDV 63559 © IEC 2026
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IEC CDV 63559 © IEC 2026
CONTENTS
CONTENTS . 1
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Designation system . 7
4.1 Purpose . 7
4.2 Conductor composition . 7
4.3 Conductor designation . 10
5 Requirements for stranded conductors . 10
5.1 Materials . 10
5.2 Formed wires . 10
5.3 Conductor geometry. 11
5.4 Conductor sizes and properties . 11
5.5 Surface . 11
5.6 Stranding . 11
5.7 Joints . 12
5.8 Properties of wires after stranding . 13
5.9 Increments due to stranding . 14
5.10 Conductor classification . 15
5.11 Grease . 16
5.12 Length measurement . 17
6 Calculation of conductor properties . 17
6.1 Conductor diameter . 17
6.2 Cross-sectional area . 17
6.3 Mass per unit length . 17
6.4 Rated tensile strength (RTS) . 17
6.4.1 General . 17
6.4.2 Homogeneous conductors . 18
6.4.3 Reinforced combined aluminium-steel conductors . 18
6.4.4 Supported combined aluminium-steel conductors . 18
6.4.5 Combined aluminium conductors . 18
6.5 Elastic modulus . 18
6.6 Coefficient of linear expansion . 18
6.7 DC resistance at 20°C . 19
7 Tests . 19
7.1 Classification of tests . 19
7.1.1 Type tests (T) . 19
7.1.2 Sample tests (S) . 19
7.2 Test requirements . 19
7.3 Sampling . 20
7.4 Rounding rules. 20
7.5 Test method . 20
7.5.1 Tests on wires . 20
7.5.2 Tests on conductor . 20
8 Packaging and marking . 24
IEC CDV 63559 © IEC 2026
8.1 Packaging . 24
8.2 Marking and tare . 24
8.3 Random lengths . 24
8.4 Drum barrel diameter . 24
Annex A (normative) Contents of the technical datasheet . 25
Annex B (normative) Information to be supplied by purchaser . 26
Annex C (normative) Nominal mass of grease for stranded conductors . 27
Annex D (normative) Calculation method for increments of mass or electrical
resistance due to stranding . 30
Annex E (informative) Lay ratios used for calculation of increments due to stranding . 31
Annex F (informative) Examples of conductor sizes and properties . 34
F.1 General . 35
F.2 Conductor tables of homogeneous conductors . 35
F.3 Conductor tables of steel reinforced conductors (Type 0 and 1) . 35
F.4 Conductor tables of steel supported conductors (Type 2) . 36
F.5 Conductor tables of aluminium reinforced conductors (Type 0) . 36
Annex G (informative) Maximum operating temperatures and loss of strength . 37
Bibliography . 38

Figure 1 – Examples of conductors' sections . 9
Figure 2 – Inertness test . 22
Figure C.1 – Sections of a fully greased layer and of an internally greased layer . 27
Figure C.2 – Cases of greasing application . 28

Table 1 – Lay ratio ranges for steel wire layers for non-homogeneous steel conductors . 12
Table 2 – Lay ratio ranges for aluminium wire layers . 12
Table 3 – Number of joints permitted in aluminium layers . 12
Table 4 – Permitted reductions in wire properties after stranding . 13
Table 5 – Standard increments due to stranding . 14
Table 6 – Conductor classification . 16
Table 7 – RTS reduction factors for homogeneous conductors . 18
Table 8 – List of tests to be performed . 19
Table C.1 – Coefficients k for mass of grease . 28
Table E.1 – Lay ratios used for calculation of increments due to stranding . 31
Table F.1 – Examples of aluminium homogeneous conductors (Type 0) . 35
Table F.2 – Examples of steel homogeneous conductors (Type 0) . 35
Table F.3 – Examples of steel reinforced conductors . 36
Table F.4 – Examples of steel supported conductors . 36
Table F.5 – Examples of aluminium reinforced conductors . 36

IEC CDV 63559 © IEC 2026
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Concentric lay overhead electrical stranded conductors

FOREWORD
a) 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
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical
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preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt
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liaising with the IEC also participate in this preparation. IEC collaborates closely with the International
Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two
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consensus of opinion on the relevant subjects since each technical committee has representation from all
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f) All users should ensure that they have the latest edition of this publication.
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h) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
i) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of patents, which
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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.
IEC 63559has been prepared by Maintenance Team 2 of IEC technical committee7: Overhead
electrical conductors. It is an International Standard.
This XXX edition cancels and replaces the XXX edition published in [publication_date],
Amendment 1:[publication_date] and Amendment 2:[publication_date]. This edition constitutes
a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) .;
The text of this International Standard is based on the following documents:
Draft Report on voting
XX/XX/FDIS XX/XX/RVD
IEC CDV 63559 © IEC 2026
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
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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.
IEC CDV 63559 © IEC 2026
1 Scope
This International Standard specifies the designation system, requirements, test methods,
inspection rules, marks and packaging of concentric lay overhead stranded conductors made
of combinations of any of the following metal wires:
a) round or formed conductive wires as per IEC 62641,
b) round wires as per IEC 63248.
This International Standard does not refer to gap-conductors as per IEC 62420.
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.
IEC 60468, Method of measurement of resistivity of metallic materials
IEC 61394, Overhead lines - Requirements for greases for aluminium, aluminium alloy and steel
bare conductors
IEC TR 61597, Overhead electrical conductors - Calculation methods for stranded bare
conductors
IEC 62641, Conductors for overhead lines - Aluminium and aluminium alloy wires for concentric
lay stranded conductors
IEC 63248, Conductors for overhead lines - Coated or cladded metallic wire for concentric lay
stranded conductors
ISO 2176:1995, Petroleum products — Lubricating grease — Determination of dropping point
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply. The terms and the
definitions listed here are those which differ from or do not appear in IEC 60050-466.
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
aluminium
all types of aluminium and aluminium alloys listed in IEC 62641.
3.2
conductor
concentric lay stranded conductor of an overhead line, intended as a wire or combination of
wires not insulated one from another and being laid helically in opposite directions, suitable for
carrying an electric current.
IEC CDV 63559 © IEC 2026
3.3
core
the central wire or the inner layer(s) made up of the higher strength material, used as reinforcing
or supporting part of a combined conductor.
3.4
direction of lay
direction of twist of a layer of wires as it moves away from the viewer. A right-hand lay is a
clockwise direction and a left-hand lay is an anti-clockwise direction.
Note 1 to entry: With right-hand lay, the wires conform to the direction of the central part of the letter Z when the
conductor is held vertically. With left-hand lay, the wires conform to the direction of the central part of the letter S
when the conductor is held vertically.
3.5
envelope
conductive outer layer(s) made up of the higher conductive material in a combined conductor.
3.6
equivalent diameter
diameter of a circle which would have the same cross-sectional area, mass per unit length and
electrical resistance of a given formed wire:
(1)
�
𝐷𝐷 = 𝑆𝑆
eq
𝜋𝜋
where S is the cross-sectional area of the formed wire.
3.7
formed wire
A filament of metal having a constant non-circular cross-section
3.8
inertness
The property of the wires to remain in their position after cut.
3.9
lay length
Axial length of one complete turn of the helix formed by an individual wire in a stranded
conductor.
3.10
lay ratio
ratio of the lay length to the external diameter of the corresponding layer of wires in the stranded
conductor.
3.11
lot
group of conductors manufactured by the same manufacturer under similar conditions of
production. A lot may consist of a part of or the whole of the purchased quantity.
3.12
nominal
name or identifying value of a measurable property by which a conductor or component of a
conductor is identified and to which tolerances are applied. When a property is tested, it shall
be intended as the target value.
IEC CDV 63559 © IEC 2026
3.13
maximum conductor continuous operating temperature (T )
C
maximum continuous temperature at which the conductor can be operated without significant
reduction of its rated tensile strength during its expected lifetime.
Note 1 to entry: The expected lifetime is defined between 30 and 80 years (typically 40 years) depending on
technology and environmental conditions.
3.14
maximum conductor peak load (emergency operating) temperature (T )
P
maximum temperature at which the conductor can be exposed without significant reduction of
its rated tensile strength during a cumulative period of time (peak loads).
Note 1 to entry: Cumulative duration of peak loads shall not exceed a limit time (400 to 1000 h) for Type 0 and Type
1 conductors.
3.15
rated tensile strength
RTS
breaking load of an unaged conductor, calculated from the specified tensile properties of the
constituent wires.
3.16
round wire (or wire)
Filament of metal having a constant cross-section and a circular shape
3.17
sample
one or more specimens taken from a production unit and considered to have properties
representative of a batch.
3.18
specimen
a length or a component of the conductor taken for test purposes.
3.19
steel
all types of steel and FeNi36 listed in IEC 63248.
3.20
type of conductor
classification of a combination of materials for the envelope and/or the core, based on operating
temperatures and required tests.
4 Designation system
4.1 Purpose
A designation system is used to identify stranded conductors made of aluminium wires (round
or formed) and/or steel wires.
4.2 Conductor composition
Homogeneous conductors are made up of a single material from the ones listed in 5.1.
Combined aluminium conductors are composed of an envelope and a core made up of different
aluminium types.
IEC CDV 63559 © IEC 2026
Combined aluminium-steel conductors are composed of an envelope made up of aluminium and
a core made up of steel.
Examples are given in Figure 1.
IEC CDV 63559 © IEC 2026
Figure 1 – Examples of conductors' sections
IEC CDV 63559 © IEC 2026
Other possible conductor types and designs not included above are not excluded.
4.3 Conductor designation
Conductors are identified by the following sequence:
a) a designation identifying the type of wires constituting the envelope,
b) the letter “F” (if at least one layer of the envelope is made from formed wires),
c) the sign “/” and a designation identifying the type of wires constituting the core (if present),
d) the letter “F” (if at least one layer of the core is made from formed wires),
e) the sign “-” and a code number giving the actual section of the envelope, expressed in mm
and rounded to an integer,
f) the sign “/” and a code number giving the actual section of the core (if present), expressed
in mm and rounded to an integer,
g) the sign “-” and a code number giving the overall diameter (rounded to two decimal places)
expressed in mm and multiplied by 100.
envelope material (F if formed) / core material (F if formed) - envelope actual section / core
actual section - overall diameter x 100
EXAMPLE
– A3-530-2989
conductor with overall diameter equal to 29,89 mm, composed by A3 round wires with a cross-sectional area rounded
,
to 530 mm
– A1/S1A-520/66-3150
conductor with overall diameter equal to 31,50 mm composed by:
- an envelope made up of A1 round wires with a cross-sectional area rounded to 520 mm ,
- a core made up of S1A round wires with a cross-sectional area rounded to 66 mm ,
– AT3F/ACI17SA-144/34-1600
conductor with overall diameter equal to 16,00 mm composed by:
- an envelope made up of AT3 formed wires with a cross-sectional area rounded to 144 mm ,
- a core made up of ACI17SA round wires with a cross-sectional area rounded to 34 mm .
5 Requirements for stranded conductors
5.1 Materials
Stranded conductors shall be made up of wires as per IEC 62641 and/or IEC 63248 and grease
as per 5.11, whenever a greased conductor is specified.
5.2 Formed wires
Two production processes are recognized in this standard for conductors with aluminium formed
wires:
a) wires are formed in one process and stranded in another,
b) wires are first formed and then stranded in a single process.
In any of these cases, materials shall comply with IEC 62641.
IEC CDV 63559 © IEC 2026
In the first case, the tests shall be performed on the formed wires prior to stranding and the
properties shall be based on the equivalent wire diameters. In the second case, the tests shall
be performed on the round wires prior to forming and stranding and properties shall be based
on the round wire diameter prior to forming.
5.3 Conductor geometry
When all layers of a conductor have round wires with identical diameters and a central wire, the
number of wires increases by 6 from one layer to the overlying layer and the total number of
wires of the conductor is one of the following: 7, 19, 37, 61, 91, 127, etc.
Conductors with:
– round wires with different diameters,
– round wires without a central wire,
– formed wires
shall be designed by choosing the number and dimension of wires that, in compliance with the
lay ratios from 5.6, ensure the absence of excessive overlapping and gaps between the wires
of the same layer and between different layers.
5.4 Conductor sizes and properties
The criteria for calculation of conductor sizes and properties are given in Clause 6 .
A list of conductor sizes is given in Annex F as a guidance and example of calculation.
Conductors with strandings not included in this standard may be designed and supplied as
agreed upon by the manufacturer and purchaser and the relevant requirements of this standard
shall apply.
5.5 Surface
The surface of the conductor shall be free from all imperfections visible to the unaided eye
(normal corrective lenses accepted), such as nicks, indentations, etc, not consistent with good
commercial practice.
5.6 Stranding
All wires of the conductor shall be concentrically stranded.
Consecutive wire layers shall be stranded with reverse lay directions. The lay direction of the
external layer shall be “right-hand” except when specifically indicated in the purchase order.
The wires in each layer shall be evenly and closely stranded around the underlying layer.
Adequate production process shall ensure inertness of the conductor. All wires shall lie naturally
in their position in the conductor, and where the conductor is cut, the wire ends shall remain in
position or be readily replaced by hand and then remain approximately in position.
Where a conductor has multiple layers, the lay ratio of any layer shall not exceed the lay ratio
of the layer immediately beneath it.
The lay ratio for homogeneous steel conductors shall be not less than 10 nor more than 16 for
all layers. For any other conductor, the lay ratios for steel wire layers and aluminium wire layers
shall be included into the ranges detailed respectively into Table 1 and Table 2.
IEC CDV 63559 © IEC 2026
Table 1 – Lay ratio ranges for steel wire layers for non-homogeneous steel conductors
6 wire layer 12 wire layer 18 wire layer
Number of steel wires
min max min max min max
7 16 26 - - - -
19 16 26 14 22 - -
37 17 25 16 22 14 18
Table 2 – Lay ratio ranges for aluminium wire layers
Inner layer(s) Outer layer
min max min max
10 16 10 14
5.7 Joints
For conductors containing only one steel wire there shall be no joints made during production
and after heat treatment of the wire or rod itself.
During stranding, there shall be no joints of any kind made in the steel core wire or wires.
No more than one joint per aluminium finished wire as per IEC 62641 shall be used per length
of conductor.
During stranding, no aluminium wire welds shall be made for the purpose of achieving the
required conductor length.
Joints are permitted in aluminium wires unavoidably broken during stranding, provided such
breaks are not associated with either inherently defective wire or with the use of insufficient
lengths of aluminium wires. Joints shall conform to the geometry of original wire, i.e. joints shall
be dressed smoothly with the correct shape and a diameter within the tolerance of the parent
wires and shall not be kinked.
The number of joints permitted in aluminium wires shall conform to the limits specified in Table
3. These joints shall not be closer than 15 m from a joint in the same wire or in any other
aluminium wire of the completed conductor.
The behaviour of properly spaced wire joints in stranded conductor is related to both tensile
stress and elongation. Joints shall be made by electric butt welding, electric butt cold upset
welding or cold pressure welding. The latter of the three shall be electrically annealed for
approximately 250 mm on both sides of the weld.
Table 3 – Number of joints permitted in aluminium layers
Joints permitted per conductor
Number of aluminium layers
length
1 2
2 3
3 4
4 5
5 6
6 7
While the joints in aluminium wires specified above are not required to meet the tensile strength
of unjointed wires, the jointed aluminium wires shall withstand a tensile stress of not less than:
IEC CDV 63559 © IEC 2026
– 60 MPa for A0-AL0,
– 75 MPa for A1-AL1, AT1, AT3 and AT4,
– 130 MPa for A2-AL3, A3-AL2, A4, AL4, AL5 and AT2.
5.8 Properties of wires after stranding
The properties of individual wires after stranding shall meet the requirements specified in 5.1
for wires before stranding, except for the properties listed in Table 4, for which a reduction in
acceptance values after stranding is allowed.
Table 4 – Permitted reductions in wire properties after stranding
Material Reduction after stranding
Hard-drawn aluminium
Tensile strength 5%
(A1-AL1 – IEC 62641)
Aluminium alloys (A2- Tensile strength 5%
AL3, A3-AL2, A4, AL4,
AL5 - IEC 62641)
Elongation 0.5 percentage points
formed wires
Tensile strength 5%
Thermoresistant
Elongation 0.5 percentage points
aluminium alloys (AT1
AT2 AT3 AT4 - IEC
Thermal resistance
0.05 on individual
62641)
(residual strength
wires**
ratio)
Zinc-coated steel, Tensile strength 5%
Zinc-5 % aluminium
Stress at 1%
coated steel or
5%
extension*
Advanced zinc-
aluminium alloy
Torsion 2 turns
coated steel (IEC
63248) – except
5MS7A, S7A,
Elongation 0.5 percentage points
ADMS7A, 5MS8A,
S8A, ADMS8A
Tensile strength 5%
Stress at 1%
5%
extension*
5MS7A, S7A,
ADMS7A, 5MS8A, Torsion 1 turn
S8A, ADMS8A (IEC
Elongation 0.5 percentage points
63248)
Uniformity of zinc and
zinc-aluminium 0.5
coatings
Tensile strength 5%
Stress at 1%
5%
extension*
Aluminium-clad steel
or Aluminium-clad
Torsion 2 turns
FeNi36 (IEC 63248)
Elongation 0.5 percentage points
Thickness of cladding 25% of minimum
Annealed aluminium
(A0-AL0 – IEC 62641)
Aluminium alloys (A2-
None
AL3, A3-AL2, A4, AL4,
AL5 - IEC 62641)
round wires
IEC CDV 63559 © IEC 2026
* Measurements of stress at 1% extension on steel wires other than the
central wire are unreliable. Therefore, the test is performed only on the
central wire.
** The acceptance values for the residual strength ratio for stranded
wires is 0.85 for individual wires and 0.9 for the average of all the wires
of the envelope.
The specimens of wires after stranding shall be removed and straightened from the conductor
sample taking care not to stretch or damage them in so doing.
The formed aluminium wires after stranding shall conform to the requirements of 5.1 except for
shape and diameter tolerances.
5.9 Increments due to stranding
Mass and electrical resistance of a stranded conductor are affected by the lay ratio. With the
exception of the central wire, all wires are stranded in a helix and are longer than the stranded
conductor length. The lower the lay ratio, the higher the increment to be taken into account.
For any kind of conductor (composed of round and/or formed wires), increments due to
stranding can be calculated following the methodology explained in Annex D.
For round wire conductors whose composition is described in Table 5, the increments in percent
due to stranding shall be those shown in Table 5.
Table 5 – Standard increments due to stranding
Stranding of conductor
lncrement* (increase) for mass
and electrical resistance (%)
Aluminium Steel
N. of wires N. of layers** N. of wires N. of layers** Aluminium Steel
7 1 - - 1,11 -
19 2 - - 1,68 -
37 3 - - 2,03 -
61 4 - - 2,36 -
91 5 - - 2,78 -
127 6 - - 2,85 -
6 1 1 - 1,39 -
8 1 1 - 1,66 -
18 2 1 - 1,82 -
9 1 3 1 1,91 0,34
6 1 7 1 1,51 0,52
10 1 7 1 2,01 0,52
12 1 7 1 2,17 0,52
14 1 7 1 2,30 0,52
18 2 7 1 1,94 0,52
22 2 7 1 2,07 0,52
24 2 7 1 2,13 0,52
26 2 7 1 2,18 0,52
28 2 7 1 2,22 0,52
30 2 7 1 2,26 0,52
32 2 7 1 2,30 0,52
IEC CDV 63559 © IEC 2026
36 2 7 1 2,37 0,52
42 3 7 1 2,20 0,52
45 3 7 1 2,23 0,52
48 3 7 1 2,26 0,52
54 3 7 1 2,31 0,52
72 4 7 1 2,40 0,52
84 4 7 1 2,46 0,52
14 1 19 2 2,50 0,82
15 1 19 2 2,56 0,82
16 1 19 2 2,61 0,82
18 1 19 2 2,70 0,82
30 2 19 2 2,36 0,86
32 2 19 2 2,41 0,86
36 2 19 2 2,48 0,86
42 2 19 2 2,57 0,86
54 3 19 2 2,26 0,79
38+22 3 19 2 2,22 0,79
42+20 3 19 2 2,18 0,79
66 3 19 2 2,34 0,79
78 3 19 2 2,40 0,79
96 4 19 2 2,46 0,79
100 4 19 2 2,47 0,79
18 1 37 3 2,70 1,09
24 1 37 3 2,91 1,09
72 3 37 3 2,43 0,96
54+66 4 37 3 2,32 0,86
150 5 37 3 2,38 0,86
* Increments have been calculated using lay ratios in Annex E.
** Number of layers of each type of wire, not including the central wire.
5.10 Conductor classification
Conductors made up of materials specified in 5.1 shall be classified in three main types,
according to their thermo-mechanical behaviour and specific tests:
– Type 0 – Conductors made up of hard-drawn aluminium or aluminium alloy wires (Ax or ALx
as per IEC 62641, except A0-AL0) with or without a core made up of wires as per IEC 63248;
conductors made up of only wires as per IEC 63248,
– Type 1 – Conductors made up of thermal resistant aluminium alloy wires (ATx as per IEC
62641) with or without a core made up of wires as per IEC 63248,
– Type 2 – Conductors made up of annealed aluminium wires (A0-AL0 as per IEC 62641)
supported by a core made up of wires as per IEC 63248,
as represented in Table 6.
IEC CDV 63559 © IEC 2026
Table 6 – Conductor classification

Envelope wires (IEC 62641)
Thermal
Aluminium
resistant
No envelope
Annealed Hard-drawn alloys (A2-
aluminium
aluminium aluminium AL3, A3-
alloy (AT1,
(A0-AL0) (A1-AL1) AL2, A4,
AT2, AT3,
AL4, AL5)
AT4)
No core - - 0 0 1
Group 1 (Zn-
coated 0 - 0 0 1
steel)
Group 2 (Al-
0 2 - - 1
clad FeNi36)
Group 3 (Al-
0 2 0 0 1
Core wires clad steel)
(IEC 63248)
Group 4 (Zn-
5%Al coated 0 2 0 0 1
steel)
Group 5
(Adv. Zn-Al
0 2 0 0 1
coated
steel)
Aluminium
alloy (A2-
AL3, A3- - - 0 0 -
AL2, A4,
AL4, AL5)
Core wires
Thermal
(IEC 62641)
resistant
aluminium
- - - - 1
alloy (AT1,
AT2, AT3,
AT4)
"0,1,2" indicates "type 0, type 1, type 2"
"-" means that the technology is technically not feasible or not relevant
Maximum operating temperatures T and T for a conductor composed of two materials are the
C P
minimum of the corresponding temperatures of the materials themselves, if not limited by
specific requirements related to fittings.
NOTE Type 1 and Type 2 conductors are usually operated at temperature T and T higher than the ones used for
C P
Type 0 conductors. Considerations about strength reduction due to high temperature shall be made (see Annex G).
5.11 Grease
When it is required for bare conductors to be greased in order to reduce the risk of corrosion in
some environments, the grease shall meet the requirements from IEC 61394 and be applied
with a method ensuring a full and uniform covering of the layers, according to the greasing case
(see Annex C).
The grease shall remain in the conductor in order to protect it from atmospheric corrosion in
storage and service for the specified conditions of operation and to avoid increment of noise.
To ensure it, the grease shall have a maximum operating temperature (θ as in IEC 61394) at
least 20°C higher than the maximum conductor peak load temperature (Tp).
The grease supplier shall provide a unique name or code for the product and shall retain details
of the grease composition for verification purposes.
IEC CDV 63559 © IEC 2026
Greases with different designations or from different manufacturers shall not be mixed within a
length of conductor.
5.12 Length measurement
Length measurements on the complete conductor for each drum shall be performed with
equipment having a minimum accuracy of ±1%.
The effective accuracy of length measurement shall be taken into account when defining the
tolerance on delivery lengths.
6 Calculation of conductor properties
6.1 Conductor diameter
The conductor diameter is the nominal diameter of the circumscribed circle to the theoretical
cross-section.
For conductors with a central wire, it shall be calculated as the nominal diameter of the central
wire plus twice the sum of the nominal thickness values of all the layers.
6.2 Cross-sectional area
The cross-sectional area of the envelope and/or of the core of a stranded conductor shall be
taken as the sum of the nominal cross-sectional areas of the composing wires.
This value, expressed in mm , shall be rounded to two decimal places.
6.3 Mass per unit length
The nominal mass per unit length is calculated by multiplying the cross-sectional areas of
aluminium and steel wires by the applicable densities specified in the standards mentioned in
5.1 and increasing these results by the increments given in 5.9 of this document in order to take
into account the fact that wires are formed in a helix.
This value, expressed in kg/m, is then rounded to three decimal places.
Whenever a conductor is to be greased, the nominal mass of grease shall be calculated
according to the method given in Annex C.
6.4 Rated tensile strength (RTS)
6.4.1 General
The minimum breaking strength of any single wire is the product of its nominal cross-sectional
area and the appropriate minimum breaking stress given in the standards listed in 5.1. The RTS
of a complete conductor is calculated from the minimum tensile strengths of its wires, with
specific requirements due to each combination of materials.
RTS is expressed in kN and rounded to two decimal places.
This nominal value is related to an unaged conductor. The effective breaking load can be
affected by thermal degradation, as described in Annex G.
6.4.2 Homogeneous conductors
The RTS of a homogeneous conductor shall be the sum of the minimum tensile strength of all
the wires, multiplied by the reduction factor specified in Table 7.
IEC CDV 63559 © IEC 2026
Table 7 – RTS reduction factors for homogeneous conductors
A2-AL3, A3-
AL2, A4, AL5, All from IEC
A1-AL1
AT1, AT2, AT3, 63248
AT4
< 3 layers 0,95 0,95 -
≥ 3 layers 0,90 0,95 0,95
6.4.3 Reinforced combined aluminium-steel conductors
The RTS of combined aluminium-steel conductors with an envelope made up of any aluminium
except A0-AL0 shall be the sum of the minimum tensile strength of the aluminium portion plus
the minimum tensile strength of steel corresponding to an elongation compatible with that of
aluminium at breaking load.
For the purpose of specification and practicability, this minimum tensile strength of steel is
conservatively established as the strength corresponding to 1% elongation in a 250 mm gauge
length.
6.4.4 Supported combined aluminium-steel conductors
The RTS of combined aluminium-steel conductors with an envelope made up of A0-AL0 shall
be the sum of 96% of the minimum tensile strength of the aluminium portion plus the minimum
tensile strength of the steel portion.
6.4.5 Combined aluminium conductors
The RTS of combined aluminium conductors shall be 95% of the sum of the minimum tensile
strength of the envelope plus the minimum tensile strength of the core.
6.5 Elastic modulus
Elastic modulus of the complete conductor is calculated according to equation 24 from IEC TR
61597.
Elastic modulus of aluminium wires is given in clause 7.4 from IEC TR 61597; elastic modulus
of steel wires is given in IEC 63248
A reference value for the elastic modulus of a stranded conductor shall be calculated by
multiplying the elastic modulus of the aluminium wires and of the steel wires by the following
reduction factors:
– 0.85 for A0-AL0, A1-AL1, AT1, AT3 and AT4
– 0.90 for A2-AL3, A3-AL2, A4, AL4, AL5 and AT2,
– 0.93 for steel,
and rounding to the closest
...