IEC 63026:2019

IEC 63026 ®
Edition 1.0 2019-12
INTERNATIONAL
STANDARD
colour
inside
Submarine power cables with extruded insulation and their accessories for
rated voltages from 6 kV (U = 7,2 kV) up to 60 kV (U = 72,5 kV) –
m m
Test methods and requirements
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IEC 63026 ®
Edition 1.0 2019-12
INTERNATIONAL
STANDARD
colour
inside
Submarine power cables with extruded insulation and their accessories for

rated voltages from 6 kV (U = 7,2 kV) up to 60 kV (U = 72,5 kV) –
m m
Test methods and requirements
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.060.20 ISBN 978-2-8322-7642-6

– 2 – IEC 63026:2019 © IEC 2019
CONTENTS
FOREWORD . 7
INTRODUCTION . 9
1 Scope . 10
2 Normative references . 10
3 Terms and definitions . 11
3.1 Definitions of dimensional values (thicknesses, cross-sections, etc.) . 12
3.2 Definitions concerning tests . 12
3.3 Other definitions . 12
3.4 Definitions concerning test objects . 13
4 Voltage designations, materials and rounding of numbers . 14
4.1 Rated voltages . 14
4.2 Cable insulating compounds . 15
4.3 Rounding of numbers . 15
5 Cable construction . 16
5.1 General . 16
5.2 Conductors . 16
5.3 Insulation . 16
5.4 Screening . 16
5.5 Metal screen . 17
5.6 Core oversheathing materials . 17
5.7 Assembly of three-core cables and fillers . 17
5.8 Cable armour . 17
5.9 Cable outer serving . 18
5.10 Packaging . 18
6 Cable characteristics . 18
7 Accessory characteristics . 19
8 Test conditions . 19
8.1 Ambient temperature. 19
8.2 Frequency and waveform for AC voltage tests . 19
8.3 Lightning impulse test . 19
8.4 Relationship of test voltages to rated voltages . 19
8.5 Determination of the cable conductor temperature . 20
9 Routine tests on cables and accessories . 20
9.1 General . 20
9.2 Test on manufacturing lengths . 20
9.2.1 Partial discharge test . 20
9.2.2 AC voltage test . 20
9.3 Test on factory joints. 21
9.4 Test on delivery lengths . 21
9.4.1 General . 21
9.4.2 AC voltage test . 21
9.4.3 Partial discharge test . 21
9.5 Test on accessories . 21
10 Sample tests on cables . 21
10.1 General . 21
10.2 Frequency of tests . 22

10.3 Repetition of tests . 22
10.4 Conductor examination . 22
10.5 Measurement of electrical resistance of conductor and of metal screen . 22
10.6 Measurement of thickness of insulation . 23
10.6.1 General . 23
10.6.2 Requirements for the insulation . 23
10.7 Measurement of thickness of oversheath . 23
10.7.1 General . 23
10.7.2 Requirements for the oversheath . 23
10.8 Measurement of thickness of metal sheath . 23
10.8.1 General . 23
10.8.2 General . 24
10.8.3 Strip method . 24
10.8.4 Ring method . 24
10.9 Measurement of diameters . 24
10.10 Hot set test for XLPE, EPR and HEPR insulations. 24
10.10.1 Procedure . 24
10.10.2 Requirements . 24
10.11 Measurement of capacitance . 25
10.12 Tests on components of cables with a longitudinally applied metal tape or
foil, bonded to the oversheath . 25
10.13 Examination of completed cable . 25
11 Sample tests on accessories . 25
11.1 Factory joints . 25
11.1.1 General . 25
11.1.2 PD measurement and AC voltage test . 25
11.1.3 Lightning impulse voltage test . 25
11.1.4 Hot set test for insulation . 25
11.1.5 Tensile test . 26
11.1.6 Joint inspection . 26
11.1.7 Pass criteria . 26
11.2 Sample tests on repair (field) joints and terminations . 26
11.2.1 Tests on components . 26
11.2.2 Tests on complete accessory . 26
12 Type tests on cable systems . 27
12.1 General . 27
12.2 Range of type approval . 27
12.3 Summary of type tests . 29
12.4 Mechanical tests . 29
12.4.1 Coiling test . 29
12.4.2 Tensile bending test . 32
12.4.3 Tensile test . 34
12.5 Electrical type tests . 35
12.5.1 Test voltage values . 35
12.5.2 Electrical type tests and sequence of tests . 35
12.5.3 Partial discharge tests . 36
12.5.4 Tan δ measurement . 36
12.5.5 Heating cycle voltage test . 36

– 4 – IEC 63026:2019 © IEC 2019
12.5.6 Lightning impulse voltage test followed by a power frequency voltage
test . 37
12.5.7 Examination . 37
12.5.8 Resistivity of semi-conducting screens . 38
12.6 Longitudinal/radial water penetration (LWP, RWP) test . 38
12.6.1 General . 38
12.6.2 Conductor water penetration test . 39
12.6.3 Metal screen water penetration test . 40
12.6.4 Radial water penetration test for joints . 41
12.7 Non-electrical type tests on cable components and on complete cable . 42
12.7.1 General . 42
12.7.2 Check of cable construction . 42
12.7.3 Tests for determining the mechanical properties of insulation before and
after ageing . 43
12.7.4 Tests for determining the mechanical properties of oversheaths before
and after ageing . 43
12.7.5 Ageing tests on pieces of complete cable to check compatibility of

materials . 43
12.7.6 Pressure test at high temperature for ST oversheaths. 44
12.7.7 Ozone resistance test for EPR and HEPR insulation . 44
12.7.8 Hot set test for EPR, HEPR and XLPE insulations . 44
12.7.9 Measurement of carbon black content of black PE oversheaths . 44
12.7.10 Tests on components of cables with a longitudinally applied metal tape
or foil, bonded to the oversheath . 45
12.7.11 Water absorption test on insulation . 45
12.7.12 Shrinkage test for XLPE insulation . 45
12.7.13 Determination of hardness of HEPR insulation . 45
12.7.14 Determination of the elastic modulus of HEPR insulation . 45
12.7.15 Shrinkage test for PE oversheath . 46
13 Electrical tests after installation . 46
13.1 General . 46
13.2 DC voltage test of the oversheath . 46
13.3 AC voltage test of the insulation . 46
13.4 DC voltage test of the insulation . 46
13.5 Time domain reflectometry (TDR) . 46
Annex A (normative) Methods of heating the test cable and determination of the cable
conductor temperature . 52
A.1 Purpose . 52
A.2 Methods of heating armoured cables for the electrical test . 52
A.2.1 Single-core cables . 52
A.2.2 Three-core cables . 53
A.3 Measurement of the temperature of the test cable. 54
A.3.1 General . 54
A.3.2 Installation of cable and temperature sensors . 54
A.4 Heating for the test . 57
Annex B (normative) Rounding of numbers . 58
Annex C (normative) Method of measuring resistivity of semi-conducting screens . 59
Annex D (normative) Tests on components of cables with a longitudinally applied
metal tape or foil, bonded to the oversheath . 62
D.1 Visual inspection . 62

D.2 Adhesion and peel strength of metal foil . 62
D.2.1 General . 62
D.2.2 Adhesion strength test . 62
D.2.3 Peel strength test of overlapped metal foil . 63
D.2.4 Requirements for adhesion and peel strength . 65
Annex E (normative) Determination of hardness of HEPR insulations . 66
E.1 Test piece . 66
E.2 Test procedure . 66
E.2.1 General . 66
E.2.2 Surfaces of large radius of curvature . 66
E.2.3 Surfaces of small radius of curvature . 66
E.2.4 Conditioning and test temperature . 66
E.2.5 Number of measurements . 67
Annex F (informative) Tests on factory joints . 68
Annex G (normative) Tensile bending and tensile tests load calculation . 69
Annex H (informative) DC voltage test of the insulation . 70
Bibliography . 71

Figure 1 – Example of accessory length extension in the case of factory joint . 27
Figure 2 – Example of coiling test arrangement . 30
Figure 3 – Test cable length for coiling test . 31
Figure 4 – Illustration of an example of an anchoring head where relative load sharing
between conductor and armour can be controlled . 33
Figure 5 – Example of set-up for tensile bending test with a flexible or factory joint . 34
Figure 6 – Set-up for the conductor water penetration test . 40
Figure 7 – Set-up for the metal screen water penetration test . 41
Figure 8 – Circuit diagram for TDR testing (traditional transmission line diagram, π-

model) . 47
Figure A.1 – Arrangement for heating of single-core armoured cables . 52
Figure A.2 – Arrangement 1 for heating of three-core armoured cables . 53
Figure A.3 – Arrangement 2 for heating of three-core armoured cables . 54
Figure A.4 – Installation of the temperature sensors in the conductor(s) of the
reference cable . 55
Figure A.5 – Reference cable for heating of single-core armoured cables . 56
Figure A.6 – Reference cable for heating of three-core armoured cables . 57
Figure C.1 – Preparation of samples for measurement of resistivity of conductor and
insulation screens . 61
Figure D.1 – Adhesion of metal foil . 63
Figure D.2 – Example of overlapped metal foil . 63
Figure D.3 – Peel strength of overlapped metal foil . 64
Figure D.4 – Example 1 of strength versus grip spacing curve . 64
Figure D.5 – Example 2 of strength versus grip spacing curve . 65
Figure E.1 – Test on surfaces of large radius of curvature . 67
Figure E.2 – Test on surfaces of small radius of curvature . 67

– 6 – IEC 63026:2019 © IEC 2019
Table 1 – Recommended rated voltages U . 15
Table 2 – Insulating materials . 15
Table 3 – Tan δ requirements for insulating compounds for cables . 47
Table 4 – Test voltages . 47
Table 5 – Non-electrical type tests for insulating and oversheath compounds for cables . 48
Table 6 – Test requirements for mechanical characteristics of insulating compounds
for cables (before and after ageing) . 49
Table 7 – Test requirements for mechanical characteristics of oversheathing
compounds for cables (before and after ageing) . 50
Table 8 – Test requirements for particular characteristics of insulating compounds for
cables . 51
Table D.1 – Minimum acceptable adhesion or peel strength forces . 65

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SUBMARINE POWER CABLES WITH EXTRUDED INSULATION
AND THEIR ACCESSORIES FOR RATED VOLTAGES
FROM 6 kV (U = 7,2 kV) UP TO 60 kV (U = 72,5 kV) –
m m
TEST METHODS AND REQUIREMENTS
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 63026 has been prepared by IEC technical committee 20: Electric
cables.
The text of this International Standard is based on the following documents:
FDIS Report on voting
20/1888/FDIS 20/1895/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 8 – IEC 63026:2019 © IEC 2019
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication 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
As a result of the growing demand for inter-array cables for offshore windfarms, IEC TC 20
decided to develop an International Standard for medium voltage submarine cable systems.
The worldwide mandate to reduce carbon emissions has stimulated major developments of
power production systems where the principal contribution comes from offshore wind farms.
Due to the location of these wind power generation systems, large amounts of submarine
cables are required to inter-connect individual power generating units (inter-array cable) and
to connect to the mainland (power export cable).
Many offshore wind farms have been built or are today under construction and there are plans
for even more farms to be built in future. Although the focus is on wind farms, the need for
cable connections to other types of offshore generation will increase. At this stage most of the
information and expertise already available on cables for the connection to the mainland grid
can be found in CIGRE documents.
Requirements of this document are mainly based on IEC 60502-2, IEC 60840 and CIGRE TB
490, Recommendations for testing of long AC submarine cables with extruded insulation for
system voltage above 30 (36) kV to 500 (550) kV. References to the relevant applicable
mechanical tests are taken from CIGRE TB 623, Recommendations for mechanical testing of
submarine cables.
A list of relevant additional references is given in the bibliography.

– 10 – IEC 63026:2019 © IEC 2019
SUBMARINE POWER CABLES WITH EXTRUDED INSULATION
AND THEIR ACCESSORIES FOR RATED VOLTAGES
FROM 6 kV (U = 7,2 kV) UP TO 60 kV (U = 72,5 kV) –
m m
TEST METHODS AND REQUIREMENTS
1 Scope
This document specifies test methods and requirements for power cable systems, cables with
extruded insulation and their accessories for fixed submarine installations, for rated voltages
= 7,2 kV) up to 60 kV (U = 72,5 kV).
from 6 kV (U
m m
This document includes the electrical tests and the physical tests on materials and
components as well as the specific mechanical tests that are applicable to submarine cable
systems.
The requirements apply to armoured single-core cables and three-core cables in combination
with their accessories, terminations and joints for usual conditions of installation and
operation, but not to special cables and their accessories, such as submarine cables for
dynamic applications (i.e. for direct connection to a floating structure), for which modifications
to the standard tests can be necessary or special test conditions be devised.
This document is applicable to submarine cables installed in permanently submerged
conditions with water depths up to 250 m.
NOTE This document does not include accessories having a mechanical function only, such as hang-offs or
armour clamps.
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 60228, Conductors of insulated cables
IEC 60229:2007, Electric cables – Tests on extruded oversheaths with a special protective
function
IEC 60230, Impulse tests on cables and their accessories
IEC 60287-1-1:2006, Electric cables – Calculation of the current rating – Part 1-1: Current
rating equations (100 % load factor) and calculation of losses – General
IEC 60502-2:2014, Power cables with extruded insulation and their accessories for rated
voltages from 1 kV (U = 1,2 kV) up to 30 kV (U = 36 kV) – Part 2: Cables for rated voltages
m m
from 6 kV (U = 7,2 kV) up to 30 kV (U = 36 kV)
m m
IEC 60502-4, Power cables with extruded insulation and their accessories for rated voltages
from 1 kV (U = 1,2 kV) up to 30 kV (U = 36 kV) – Part 4: Test requirements on accessories
m m
for cables with rated voltages from 6 kV (U = 7,2 kV) up to 30 kV (U = 36 kV)
m m
IEC 60811-201, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 201: General tests – Measurement of insulation thickness
IEC 60811-202, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 202: General tests – Measurement of thickness of non-metallic sheath
IEC 60811-203, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 203: General tests – Measurement of overall dimensions
IEC 60811-401, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 401: Miscellaneous tests – Thermal ageing methods – Ageing in an air oven
IEC 60811-402, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 402: Miscellaneous tests – Water absorption tests
IEC 60811-403, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 403: Miscellaneous tests – Ozone resistance test on cross-linked compounds
IEC 60811-501, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 501: Mechanical tests – Tests for determining the mechanical properties of insulating and
sheathing compounds
IEC 60811-502, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 502: Mechanical tests – Shrinkage test for insulations
IEC 60811-503, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 503: Mechanical tests – Shrinkage test for sheaths
IEC 60811-507, Electric and optical fibre cables – Test methods for non-metallic materials–-
Part 507: Mechanical tests – Hot set test for cross-linked materials
IEC 60811-508, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 508: Mechanical tests – Pressure test at high temperature for insulation and sheaths
IEC 60811-605, Electric and optical fibre cables – Test methods for non-metallic materials –
Part 605: Physical tests – Measurement of carbon black and/or mineral filler in polyethylene
compounds
IEC 60840, Power cables with extruded insulation and their accessories for rated voltages
above 30 kV (U = 36 kV) up to 150 kV (U = 170 kV) – Test methods and requirements
m m
IEC 60885-3, Electrical test methods for electric cables – Part 3: Test methods for partial
discharge measurements on lengths of extruded power cables
ISO 48-2, Rubber, vulcanized or thermoplastic – Determination of hardness – Part 2:
Hardness between 10 IRHD and 100 IRHD
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp

– 12 – IEC 63026:2019 © IEC 2019
3.1 Definitions of dimensional values (thicknesses, cross-sections, etc.)
3.1.1
nominal value
value by which a quantity is designated and which is often used in tables
Note 1 to entry: Usually, in this document, nominal values give rise to values to be checked by measurements
taking into account specified tolerances.
3.1.2
median value
when several test results have been obtained and ordered in an increasing (or decreasing)
succession, middle value if the number of available values is odd, and mean of the two middle
values if the number is even
3.2 Definitions concerning tests
3.2.1
routine test
test made by the manufacturer on each manufactured component (length of cable or
accessory) to check that the component meets the specified requirements
3.2.2
sample test
test made by the manufacturer on samples of completed cable or components taken from a
completed cable or accessory, at a specified frequency so as to verify that the finished
product meets the specified requirements
3.2.3
type test
test made before supplying on a general commercial basis a type of cable system covered by
IEC 63026, in order to demonstrate satisfactory performance characteristics to meet the
intended application
Note 1 to entry: Once successfully completed, these tests need not be repeated, unless changes are made in the
cable or accessory with respect to materials, manufacturing process, design or design electrical stress levels,
which might adversely change the performance characteristics.
3.2.4
electrical test after installation
test made to demonstrate the integrity of the cable system as installed
Note 1 to entry: Integrated optical elements, if present, will be tested upon customer request. Tests to be defined
on agreement between customer and manufacturer.
3.3 Other definitions
3.3.1
cable system
cable with installed accessories including components used for thermo-mechanical restraint of
systems limited to those used for terminations and joints only
3.3.2
nominal electrical stress
electrical stress calculated at U using nominal dimensions
3.3.3
test object
object, which is a cable length or an accessory, to be subjected to testing

3.3.4
test assembly
assembly, which is a combination of series connected test objects, i.e. cable and accessories,
simultaneously under test
3.4 Definitions concerning test objects
3.4.1
extrusion length
length of cable conductor with the insulation and semi-conducting layers continuously
extruded in the same non-interrupted extrusion operation
3.4.2
manufacturing length
whole extrusion length (or parts thereof if cut), where construction elements (outside the outer
semi-conducting layer) have been applied
3.4.3
delivery length
completed cable length, typically on a drum, in a coil or on a turntable
3.4.4
factory joint
joint between extrusion lengths/manufacturing lengths that is manufactured under controlled
factory conditions
Note 1 to entry: Factory joints have the same mechanical and electrical performance as the original cable and are
generally fully flexible.
3.4.5
field joint
joint between two delivery lengths of cable that is completed with all cable construction
elements
Note 1 to entry: A field joint is generally used to connect two delivery lengths offshore or in the beach area. In this
document the requirements for field joints are the same as for repair joints.
Note 2 to entry: The requirements in this document are different for rigid and flexible types of joint.
Note 3 to entry: Repair and field joints may be of identical design.
3.4.6
repair joint
joint used for repairing a damaged submarine cable
Note 1 to entry: The requirements in this document are different for rigid and flexible types of joint.
Note 2 to entry: Repair and field joints may be of identical design.
3.4.7
rigid joint
joint which cannot be subjected to the coiling or tensile bending tests
3.4.8
flexible repair joint
flexible field joint
repair (field) joint that is manufactured under controlled conditions and that is fully flexible
Note 1 to entry: Flexible repair (field) joints have the same mechanical and electrical performance as the original
cable.
– 14 – IEC 63026:2019 © IEC 2019
3.4.9
asymmetric joint
joint which connects two cables with the same insulation system, but of different design
Note 1 to entry: Examples of different design are different conductors, different insulation or screen dimensions,
or land and submarine cables.
3.4.10
long length
cable length which cannot be moved into a shielded room for the partial discharge
measurement
3.4.11
significant wave height
average wave height (trough to crest) of the highest third of the waves
4 Voltage designations, materials and rounding of numbers
4.1 Rated voltages
The rated voltages U /U (U ) of the cables considered in this document are as follows:
0 m
U /U (U ) = 3,6/6 (7,2) – 6/10 (12) – 8,7/15 (17,5) – 12/20 (24) – 18/30 (36) – 26/45 (52) –
0 m
36/60 (72,5) kV.
NOTE 1 The voltages given above are the standard designations although in some countries other designations
are used, e.g. – 5,8/10 – 6,6/11 – 11,5/20 – 17,3/30 – 19/33 – 21/35 – 26/35 – 26/46 – 38/66 kV.
In the voltage designation of cables U /U (U ):
0 m
U is the rated power frequency voltage between conductor and earth or metal screen for
which the cable is designed;
U is the rated power frequency voltage between conductors for which the cable is
designed;
U is "highest voltage for equipment'' (see IEC 60038).
m
The rated voltage of the cable for a given application shall be suitable for the operating
conditions in the system in which the cable is used. To facilitate the selection of the cable,
systems are divided into three categories:
– category A: this category comprises those systems in which any phas
...