IEC 61892-4:2007

INTERNATIONAL IEC
STANDARD 61892-4
First edition
2007-06
Mobile and fixed offshore units –
Electrical installations –
Part 4:
Cables
Reference number
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INTERNATIONAL IEC
STANDARD 61892-4
First edition
2007-06
Mobile and fixed offshore units –
Electrical installations –
Part 4:
Cables
PRICE CODE
Commission Electrotechnique Internationale X
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue

– 2 – 61892-4 © IEC:2007(E)
CONTENTS
FOREWORD.4

INTRODUCTION.6

1 Scope.7

2 Normative references .7

3 Terms and definitions .8

4 Types, installation and operating conditions of cables .10

4.1 Types of cables .10
4.2 Voltage rating.10
4.2.1 Power frequency cables .10
4.2.2 Control and instrumentation cables.11
4.3 Cross-sectional areas of conductors and current-carrying capacities .11
4.3.1 Cross-sectional areas of conductors .11
4.3.2 Current-carrying capacities.13
4.3.3 Current-carrying capacities for continuous service.13
4.3.4 Correction factors for different ambient air temperatures .17
4.3.5 Correction factors for short time duty.18
4.3.6 Correction factors for cable grouping .21
4.4 Voltage drop.22
4.5 Estimation of lighting loads.22
4.6 Parallel connection of cables.22
4.7 Separation of circuits.22
4.8 Short circuit capacity (withstand capability). .22
4.9 Conductor .22
4.10 Insulation material.23
4.11 Screen, core screen or shield .23
4.12 Sheathing material .23
4.13 Metallic braid armour.23
4.14 Fire performance.23
4.15 Bending radius .24

Annex A (informative) Tabulated current-carrying capacities – Defined installations .26

Annex B (Informative) Fire stops.40
Annex C (Informative) Jet fire test for hydrocarbon (HCF) fire resistant cables .41
Annex D (Informative) Drilling fluid test procedure and requirements .42

Bibliography.

Table 1 – Choice of cables for a.c. systems .11
∗
Table 2 – Sizes of earth continuity conductors and equipment earthing connections.13
Table 3 – Coefficient related to maximum permissible temperature of the conductor.14
Table 4 – Current-carrying capacities in continuous service at maximum rated
conductor temperature of 70 °C (ambient air temperature 45 °C) .15

61892-4 © IEC:2007(E) – 3 –
Table 5 – Current-carrying capacities in continuous service at maximum rated

conductor temperature of 90 °C (ambient air temperature 45 °C) .16

Table 6 – Current-carrying capacities in continuous service at maximum rated

conductor temperature of 95 °C (ambient air temperature 45 °C) .17

Table 7 – Correction factor for various ambient air temperatures (reference ambient
temperature of 45 °C) .18

Table 8 – Correction factor for various ambient air temperatures (reference ambient

temperature of 30 °C) .18

Table 9 – Bending radii for cables rated up to 1,8/3 kV .25

Table 10 – Bending radii for cables rated at 3,6/6,0(7,2) kV and above.25

Table A.1 – Current-carrying capacities in amperes – Copper conductor temperature
60 °C and reference ambient air temperature 45 °C .29
Table A.2 – Current-carrying capacities in amperes – Copper conductor temperature
70 °C and reference ambient air temperature 45 °C .30
Table A.3 – Current-carrying capacities in amperes – Copper conductor temperature
85 °C and reference ambient air temperature 45 °C .31
Table A.4 – Current-carrying capacities in amperes – Copper conductor temperature
60 °C and reference ambient air temperature 30 °C .32
Table A.5 – Current-carrying capacities in amperes – Copper conductors temperature
70 °C and reference ambient temperature 30 °C .33
Table A.6 – Current-carrying capacities in amperes – Copper conductors temperature
85 °C and reference ambient temperature 30 °C .34
Table A.7 – Current-carrying capacities in amperes – Copper conductors temperature
90 °C and reference ambient temperature 45 °C .35
Table A.8 – Current-carrying capacities in amperes – Copper conductors temperature
95 °C and reference ambient temperature 45 °C .36
Table A.9 – Correction factors for groups of more than one circuit or of more than one
multi-core cable to be used with current-carrying capacities of Tables A.1 to A.8.37
Table A.10 – Correction factors for group of more than one multi-core cable to be
applied to reference ratings for multi-core cables in free air – Method of installation E
in Tables A.1 to A.8 .38
Table A.11 – Correction factors for groups of more than one circuit of single-core
cables to be applied to reference rating for one circuit of single-core cables in free air
– Method of installation F in Tables A.1 to A.8 .39

Figure 1 – Time constant of cables .19
Figure 2 – Correction factors for half-hour and one-hour service.20
Figure 3 – Correction factor for intermittent service.21
Figure C.1 – International recognized HC fire curve .41

– 4 – 61892-4 © IEC:2007(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
MOBILE AND FIXED OFFSHORE UNITS –

ELECTRICAL INSTALLATIONS –
Part 4: 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
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with the International Organization for 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
consensus of opinion on the relevant subjects since each technical committee has representation from all
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
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5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
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expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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 61892-4 has been prepared by IEC technical committee 18:
Electrical installations of ships and of mobile and fixed offshore units, in cooperation with
SC 18A: Cables and cable installations.
The text of this standard is based on the following documents:
FDIS Report on voting
18/1052/FDIS 18/1058/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

61892-4 © IEC:2007(E) – 5 –
A list of all parts of the IEC 61892 series, published under the general title Mobile and fixed
offshore units – Electrical installations, can be found on the IEC website.

The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in

the data related to the specific publication. At this date, the publication will be

• reconfirmed;
• withdrawn;
• replaced by a revised edition, or

• amended.
A bilingual version of this publication may be issued at a later date.

– 6 – 61892-4 © IEC:2007(E)
INTRODUCTION
IEC 61892 forms a series of International Standards intended to enable safety in the design,

selection, installation, maintenance and use of electrical equipment for the generation,

storage, distribution and utilisation of electrical energy for all purposes in offshore units which

are being used for the purpose of exploration or production of petroleum resources.

This part of IEC 61892 also incorporates and coordinates, as far as possible, existing rules

and forms a code of interpretation, where applicable, of the requirements of the International

Maritime Organisation. It also constitutes a guide for future regulations which may be

prepared and a statement of practice for offshore unit owners, constructors and appropriate

organisations.
This standard is based on equipment and practices which are in current use but it is not
intended in any way to impede development of new or improved techniques.
The ultimate aim has been to produce a set of International standards exclusively for the
offshore petroleum industry.
61892-4 © IEC:2007(E) – 7 –
MOBILE AND FIXED OFFSHORE UNITS –

ELECTRICAL INSTALLATIONS –
Part 4: Cables
1 Scope
This part of IEC 61892 specifies requirements for the choice and installation of electrical
cables intended for fixed electrical systems in mobile and fixed offshore units, including
pumping or “pigging” stations, compressor stations and exposed location single buoy
moorings, used in the offshore petroleum industry for drilling, production, processing and for
storage purposes.
The reference to fixed electrical systems includes those that are subjected to vibration due to
the movement of the unit, e.g. cables installed on a drag chain, and not those that are
intended for repeated flexing. Cables suitable for repeated flexing use are detailed in other
IEC specifications, e.g. IEC 60227 and IEC 60245, and their uses on board offshore units are
restricted to those situations which do not directly involve exposure to a marine environment,
e.g. portable tools, domestic appliances, etc.
The following types and applications of cables are not included:
• optical fibre cables;
• sub-sea and umbilical cables;
• cables supplying downhole pumps;
• data, telecommunication and radio frequency cables.
2 Normative references
The following referenced documents are indispensable for the application 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.
1)
IEC 60038:1983, IEC standard voltages
Amendment 1 (1994)
Amendment 2 (1997)
IEC 60092-350:2001, Electrical installations in ships – Part 350: Shipboard power cables -
General construction and test requirements
IEC 60092-351, Electrical installations in ships – Part 351: Insulating materials for shipboard
and offshore units, power, control, instrumentation, telecommunication and data cables
IEC 60092-353, Electrical installations in ships – Part 353: Single and multicore non-radial
field power cables with extruded solid insulation for rated voltages 1 kV and 3 kV
IEC 60092-354, Electrical installations in ships – Part 354: Single and three-core power
cables with extruded solid insulation for rated voltages 6 kV (U =7,2 kV); up to 30 kV
m
=36 kV)
(U
m
___________
1)
There exists a consolidated edition 6.2 (2002) including IEC 60038:1983 and its Amendments 1 and 2.

– 8 – 61892-4 © IEC:2007(E)
IEC 60092-359, Electrical installations in ships – Part 359: Sheathing materials for shipboard

power and telecommunication cables

IEC 60092-376, Electrical installations in ships – Part 376: Cables for control and

instrumentation circuits 150/250 V (300 V)

IEC 60228:2004, Conductors of insulated cables

IEC 60331-21:1999, Tests for electric cables under fire conditions – Circuit integrity – Part 21:

Procedures and requirements – Cables of rated voltage up to and including 0,6/1,0 kV

IEC 60331-31:2002, Tests for electric cables under fire conditions – Circuit integrity – Part 31:
Procedures and requirements for fire with shock – Cables of rated voltage up to and including
0,6/1 kV
IEC 60332-1-2:2004, Tests on electric and optical fibre cables under fire conditions – Part 1-
2: Test for vertical flame propagation for a single insulated wire or cable – Procedure for 1 kW
pre-mixed flame
IEC 60332-3-22:2000, Tests on electric cables under fire conditions – Part 3-22: Test for
vertical flame spread of vertically-mounted bunched wires or cables – Category A
IEC 60754-1:1994, Test on gases evolved during combustion of materials from cables –
Part 1: Determination of the amount of halogen acid gas
IEC 60754-2:1991, Test on gases evolved during combustion of electric cables – Part 2:
Determination of degree of acidity of gases evolved during the combustion of materials taken
from electric cables by measuring pH and conductivity
Amendment 1 (1997)
IEC 61034-2:2005, Measurement of smoke density of cables burning under defined conditions
– Part 2: Test procedure and requirements
IEC 61892-1:2001, Mobile and fixed offshore units – Electrical installations – Part 1: General
requirements and conditions
IEC 61892-2, Mobile and fixed offshore units – Electrical installations – Part 2: System design
IEC 61892-6, Mobile and fixed offshore units – Electrical installations – Part 6: Installation

3 Terms and definitions
3.1
appropriate authority
governmental body and/or classification society with whose rules an offshore unit is required
to comply
3.2
braid armour
covering formed from braided metal wires used to protect the cable from external mechanical
effects
3.3
braid
covering made of plaited metallic or non-metallic material

61892-4 © IEC:2007(E) – 9 –
3.4
core insulated conductor
assembly comprising a conductor and its own insulation (and screens, if any)

3.5
core screen
electric screen of non-metallic and/or metallic materials covering the insulation

3.6
insulated cable
an assembly consisting of:
– one or more cores,
– their individual covering(s) (if any)
– assembly protection (if any)
– protective coverings (if any)
NOTE Additional uninsulated conductor(s) may be included in the cable.
3.7
conductor screen
non-metallic conducting layer applied between the conductor and insulation to equalise the
electrical stress between these components. It may also provide smooth surfaces as the
boundaries of the insulation and assist in the elimination of spaces at these boundaries
3.8
inner sheath
inner jacket (North America) non-metallic extruded sheath applied under a metallic sheath,
reinforcement, or armour
NOTE
It must be extruded.
It can be used to fill the interstices.
It must be a material listed in IEC 60092-359.
It has a defined nominal thickness (value).

3.9
outer sheath
jacket (North America)
non-metallic extruded sheath applied over a metallic sheath, reinforcement, or armour It must
.
be extruded
NOTE 1
It can be used to fill the interstices.
It must be a material listed in IEC 60092-359.
It has a defined nominal thickness (value).
NOTE 2 The term sheath is only used for metallic coverings in North America, where the term jacket is used for
non-metallic coverings.
3.10
electrostatic screen
electrostatic shield (North America)
surrounding earthed metallic layer to confine the electric field within the cable cores, pair(s),
triples(s), or quad(s), and to protect the pair(s), triad(s), or quad(s) from external influence

– 10 – 61892-4 © IEC:2007(E)
4 Types, installation and operating conditions of cables

4.1 Types of cables
Cables constructed in accordance with IEC 60092-350, IEC 60092-353, IEC 60092-354 and

IEC 60092-376 are recommended for use on mobile and fixed offshore units.

4.2 Voltage rating
4.2.1 Power frequency cables
The maximum rated voltage (U) considered in this standard for power frequency cables is

30 kV.
In the voltage designation of cables U / U / (U )
0 m :
– U is the rated power frequency voltage between conductor and earth or metallic screen
for which the cable is designed;
– U is the rated power frequency voltage between conductors for which the cable is
designed;
– U is the maximum value of the highest system voltage which may be sustained under
m
normal operating conditions at anytime and at any point in the system. It excludes
transient voltage conditions and rapid disconnection of loads.
U is chosen to be equal to or greater than the highest voltage of the three-phase system.
m
Where cables are permitted for use on circuits where the nominal system voltage exceeds the
rated voltage of the cables, the nominal system voltage shall not exceed the highest system
voltage (U ) of the cable.
m
Careful consideration shall be given to cables subjected to voltage surges associated with
highly inductive circuits to ensure that they are of a suitable voltage rating.
The choice of standard cables of appropriate voltage designations for particular systems
depends upon the system voltage and the system earthing arrangements
The rated voltage of any cable shall not be lower than the nominal voltage of the circuit for
which it is used. To facilitate the choice of the cable, the values of U recommended for cables
to be used in three-phase systems are listed in Table 1 in which systems are divided into the
following three categories.
• Category A
This category comprises those systems in which any phase conductor that comes in contact
with earth or an earth conductor is automatically disconnected from the system.
• Category B
This category comprises those systems that, under fault conditions are operated for a short
time, not exceeding 8 h on any occasion, with one phase earthed.
For example, for a 13,8 kV system of Category A or B, the cable should have a rated voltage
not less than 8,7/15 kV.
NOTE In a system where an earth fault is not automatically and promptly eliminated, the increased stresses on
the insulation of cables during the earth fault are likely to affect the life of the cables to a certain degree. If the
system is expected to be operated fairly often with a sustained earth fault, it may be preferable to use cables
suitable for Category C. In any case, for classification as Category B the expected total duration of earth faults in
any year should not exceed 125 h.
• Category C
61892-4 © IEC:2007(E) – 11 –
This category comprises all systems that do not fall into Categories A and B.

The nominal system voltages from 3,3 kV to 30 kV shown in Table 1 are generally in

accordance with Series 1 in IEC 60038. For nominal system voltages intermediate between

these standard voltages and also between 0,6/1 kV and 1,8/3,3 kV, the cables should be

selected with a rated voltage not less than the next higher standard value. For example: a first

earth fault with one phase earthed causes a √3 higher voltage between the phases and earth

during the fault. If the duration of this earth fault exceeds the times given for Category B, then

according to Table 1, for a 17,5 kV system, the cable is to have a rated voltage not less than

12/20 kV.
A d.c. voltage to earth of up to a maximum of 1,5 times the a.c. U voltage may be used.
However consideration should be given to the peak value when determining the voltage of
d.c. systems derived from rectifiers, bearing in mind that smoothing does not modify the peak
value when the semiconductors are operating on an open circuit.
Table 1 – Choice of cables for a.c. systems
System Minimum rated voltage
System voltage
category of cable U /U
o
Maximum
Unscreened
Single-core or
Nominal voltage U
sustained
screened
voltage, U
m
kV kV kV kV
up to 0,25 0,30 A, B or C 0,15 / 0,25 −
1 1,2 A, B or C 0,6 / 1,0 0,6 /1,0
3 3,6 A or B 1,8 / 3,0 1,8 / 3,0
3 3,6 C 3,6 / 6,0
6 7,2 A or B 3,6 / 6,0
6 7,2 C 6,0 / 10
10 12 A or B 6,0 / 10
10 12 C 8,7 / 15
15 17,5 A or B 8,7 / 15
15 17,5 C 12 /20
20 24 A or B 12 / 20
20 24 C 18 / 30
30 36 A or B 18 / 30
4.2.2 Control and instrumentation cables
The typical rated voltage (U) for control and instrumentation cables considered in this
standard is 250 V.
In some instances for conductor sizes 1 mm and larger, or when circuits are to be supplied
from a low impedance source, 0,6/1 kV rated cables shall be used as control or
instrumentation cables.
4.3 Cross-sectional areas of conductors and current-carrying capacities
4.3.1 Cross-sectional areas of conductors
The cross-sectional area of each conductor shall be selected to be large enough to comply
with the following conditions:

– 12 – 61892-4 © IEC:2007(E)
a) The highest load to be carried by the cable shall be calculated from the load demands and

diversity factors given in IEC 61892-2.

b) The “corrected current rating” calculated by applying the appropriate correction factors to

the “current rating for continuous services” shall not be lower than the highest current

likely to be carried by the cable. The correction factors to be applied are those given in

4.3.4, 4.3.5 and 4.3.6.
c) The voltage drop in the circuit shall not exceed the limits specified by the appropriate

authority for the circuits concerned - further guidance is given in 4.4.

d) The cross-sectional area of the conductor shall be able to accommodate the mechanical
and thermal effects of a short circuit current (see 4.8) and the effect upon voltage drop of
motor-starting currents (see 4.4, Note 3).

e) The nominal cross-section of the earth conductor shall comply with Table 2. One of the
alternative methods of determining the cross-sectional area of each earthing conductor is
that based upon the rating of the fuse or circuit protection device installed to protect the
circuit. If this method is used the nominal cross-sectional area finally selected shall be the
higher of any cross-sectional area determined by each of the methods.
NOTE The tables incorporated in this standard for the current ratings give only average values; these are not
exactly applicable to all cable constructions and all installation conditions existing in practice. They are
nevertheless recommended for general application, considering that the errors (a few degrees Celsius in the
estimated operating temperature) are of little importance against the advantages of having a single international
standard for the evaluation of the current ratings. In particular cases, however, a more precise evaluation is
permitted, based on experimental or calculated data acceptable to all interested parties

61892-4 © IEC:2007(E) – 13 –
a
Table 2 – Sizes of earth continuity conductors and equipment earthing connections

Cross-section Q of
associated
current-carrying Minimum cross-section of

Arrangement of earth conductor
conductor (One earth conductor

phase or pole)
mm
1 i) Insulated earth conductor in cable for fixed Q ≤ 16 Q

installation.
ii) Copper braid of cable for fixed installation

according to subclause 8.2 of IEC 60092-350.

50% of the current-carrying
iii) Separate, insulated earth conductor for fixed
Q > 16 conductor, but not less than
installation in pipes in dry accommodation spaces,
16 mm
when carried in the same pipe as the supply cable.

iv) Separate, insulated earth conductor when installed
inside enclosures or behind covers or panels,
including earth conductor for hinged doors.
2 Uninsulated earth conductor in cable for fixed Q ≤ 2,5 1 mm
installation, being laid under the cable's armour or
2,5 < Q ≤ 6 1,5 mm
copper braid and in metal-to-metal contact with this.
Q > 6 Not permitted
3 Separately installed earth conductor for fixed Q < 2,5 Same as current-carrying
installation other than specified in 1 iii) and 1 iv). conductor subject to min.
1,5 mm for stranded earthing
connection or 2,5 mm for
unstranded earthing
connection
2,5 < Q ≤ 120 50 % of current-carrying
conductor, but not less than
4 mm
Q > 120 70 mm
4 Insulated earth conductor in flexible cable. Q ≤ 16 Same as current-carrying
conductor
Q > 16 50 % of current-carrying
conductor, but minimum
16 mm
NOTE Refer also to 4.3.1 for method based on rating of fuses.

a
The term protective conductor is accepted as an alternative term for the earth continuity conductor.

4.3.2 Current-carrying capacities
The procedure for cable selection employs rating factors to adjust the current-carrying
capacities for different ambient temperature, short time duty, for the mutual heating effects of
grouping with other cables, and methods of installation. Guidance on the use of these factors
is given below.
4.3.3 Current-carrying capacities for continuous service
Continuous service for a cable shall be considered, for the purpose of this standard, as a
current-carrying service with constant load having a duration longer than three times the
thermal time constant of the cable, i.e., longer than the critical duration (see Figure 1).

– 14 – 61892-4 © IEC:2007(E)
The current to be carried by any conductor for sustained periods during normal operation shall

be such that the appropriate conductor temperature limit is not exceeded.

These current-carrying capacities are derived from those as documented in

IEC 60092-352:1997.
Current ratings currently available from various approval authorities for use in the general

case for continuous service are shown in Tables 4 through 6 and are recommended as being

applicable to both unarmoured and armoured cables laid in free air as a group of six bunched

together.
These ratings may be considered applicable, without correction factors, for cables bunched
together on cable trays, in cable conduits, pipes or trunking, unless more than six cables,
which may be expected to operate simultaneously at their full rated capacity, are laid close
together in a cable bunch in such a way that there is an absence of free air circulation around
them. In this case a correction factor of 0,85 should be applied.
NOTE Cables are said to be bunched when two or more are contained within a single conduit, trunking or duct, or
if not enclosed, are not separated from each other.
These ratings have been calculated using the basis given below for an ambient temperature
of 45°C and a conductor temperature that is assumed to be equal to the maximum rated
temperature of the insulation and continuously maintained. The cable constructions are based
on the various insulating materials given in 60092-351 together with any type of sheathing
material given in 60092-359.
The basis for the calculation of the ratings in Tables 4 to 6 is as follows:
The current ratings I, in amperes, have been calculated for each nominal cross-sectional area
A, in square millimetres, with the formula:
0,625
I = α A
where α is a coefficient related to the maximum permissible service temperature of the
conductor as follows:
Table 3 – Coefficient related to maximum permissible temperature of the conductor
Maximum permissible temperature of the 70 °C 90 °C 95 °C
conductor
≥ 2,5 mm² 12 17 18
Values of α for nominal
cross-sectional area
<2,5 mm² 11,5 18 20
For two-, three- and four-conductor cables, the current ratings given in Table 3 should be
multiplied by the following (approximate) correction factors:
0,85 for two core cables,
0,70 for three- and four-core cables.
The ambient temperature of 45 °C, on which the current ratings in Tables 4 through 6 are
based, is considered as a standard value for the ambient air temperature, generally applicable
for any kind of offshore unit in any climate.
When, however, fixed offshore units are installed in locations where the ambient temperature
is known to be permanently lower than 45 °C, it is permitted to increase the current ratings
from those in the tables - but in no case shall the ambient temperature be considered to be
lower than 25 °C.
61892-4 © IEC:2007(E) – 15 –
When, on the other hand, it is to be expected that the air temperature around the cables could

be higher than 45 °C (for instance, when a cable is wholly or partly installed in spaces or

compartments where heat is produced or higher cable temperatures could be reached due to

heat transfer), the current ratings from the Tables 4 through 6 shall be reduced.

The correction factors for these different ambient air temperatures are given in Table 7 or 8.

The selection of the method applicable to any particular installation is the responsibility of the

appropriate approval authority or governing regulation. An optional alternative method is given

in Appendix A (Informative) when utilized under Engineering Supervision.

Table 4 – Current-carrying capacities in continuous service at maximum rated
conductor temperature of 70 °C (ambient air temperature 45 °C)
Rated conductor
70 °C
temperature
Nominal cross-sectional
Single-core 2-core 3- or 4-core
area
(mm²) (A) (A) (A)
1 12 10 8
1,5 15 13 10
2,5 20 18 15
4 29 24 20
6 37 31 26
10 51 43 35
16 68 58 48
25 90 76 63
35 111 94 78
50 138 118 97
70 171 145 120
95 207 176 145
120 239 203 167
150 275 234 192
185 313 266 219
240 369 313 258
300 424 360 297
400 508 431 355
500 583 496 408
630 674 573 472
– 16 – 61892-4 © IEC:2007(E)
Table 5 – Current-carrying capacities in continuous service at maximum rated
conductor temperature of 90 °C (ambient air temperature 45 °C)

Conductor temperature 90 °C
Nominal cross-sectional
Single-core 2-core 3- or 4-core
area
(mm²) (A) (A) (A)
1 18 15 13
1,5 23 20 16
2,5 30 26 21
4 40 34 28
6 52 44 36
10 72 61 50
16 96 82 67
25 127 108 89
35 157 133 110
50 196 167 137
70 242 206 169
95 293 249 205
120 339 288 237
150 389 331 273
185 444 377 311
240 522 444 366
300 601 511 420
400 719 611 503
500 827 703 579
630 955 812 669
61892-4 © IEC:2007(E) – 17 –
Table 6 – Current-carrying capacities in continuous service at maximum rated
conductor temperature of 95 °C (ambient air temperature 45 °C)

Conductor temperature 95 °C
Nominal cross-sectional 3- or 4-
Single-core 2-core
area core
(mm²) (A) (A) (A)
1 20 17 14
1,5 26 22 18
2,5 32 27 22
4 43 36 30
6 55 47 39
10 76 65 53
16 102 87 71
25 135 114 94
35 166 141 116
50 208 176 145
70 256 218 179
95 310 263 217
120 359 305 251
150 412 351 289
185 470 400 329
240 553 470 387
300 636 541 445
400 761 647 533
500 875 744 613
630 1011 860 708
4.3.4 Correction factors for different ambient air temperatures
The ambient temperature is the temperature of the surrounding medium when the cable(s) or
insulated conductor(s) under consideration are not loaded.
The current-carrying capacity tabulated in this subclause and in Annex A assumes the

following reference ambient temperatures for insulated conductors and cables in air,
irrespective of the method of installation:
• 45 °C for standard situations, generally applicable for any kind of unit and in any climate;
• 30 °C for particular situations, applicable for mobile and fixed offshore units for particular
uses for which the ambient temperature is known to be permanently lower or equal to
30 °C.
Where the ambient temperature in the intended location of the insulated conductors or cables
differs from the reference ambient temperature, the appropriate correction factors specified in
Table 7 and Table 8 shall be applied to the values of current-carrying capacity set out in this
subclause and in Annex A.
NOTE The air temperature around the cables can be higher than 45 °C when, for instance, a cable is wholly or
partly installed in spaces or compartments where heat is produced or due to heat transfer.

– 18 – 61892-4 © IEC:2007(E)
Table 7 – Correction factor for various ambient air temperatures

(reference ambient temperature of 45 °C)

Maximum
conductor Correction factors for ambient air temperatures
temperature
°C 25 °C 30 °C 35 °C 40 °C 45 °C 50 °C 55 °C 60 °C 65 °C 70 °C 75 °C 80 °C 85 °C

70 1,32 1,25 1,18 1,10 1,00 0,89 0,77 0,63 - - - - -

90 1,20 1,15 1,10 1,05 1,00 0,94 0,88 0,82 0,74 0,67 0,58 0,47 -

95 1,18 1,14 1,10 1,05 1,00 0,95 0,89 0,84 0,77 0,71 0,63 0,55 0,45

Table 8 – Correction factor for various ambient air temperatures
(reference ambient temperature of 30 °C)
Maximum
conductor Correction factors for ambient air temperatures
temperature
°C 20 °C 25 °C 30 °C 35 °C 40 °C 45 °C 50 °C 55 °C 60 °C 65 °C 70 °C 75 °C 80 °C 85 °C
70 1,12 1,06 1,00 0,94 0,87 0,79 0,71 0,61 0,50 - - - - -
90 1,08 1,04 1,00 0,96 0,91 0,87 0,82 0,76 0,71 0,65 0,58 0,50 0,41 -
95 1,07 1,04 1,00 0,96 0,92 0,88 0,83 0,78 0,73 0,68 0,62 0,55 0,48 0.39

4.3.5 Correction factors for short time duty
If a cable is intended to supply a motor or equipment operating for periods of half an hour or
one hour, its current rating, as given by the relevant table (see 4.3.3 and Annex A), may be
increased using the relevant correction factors given by Figure 2. These correction factors are
applicable only if the intermediate periods of rests are longer than the critical duration (which
is equal to three times the time constant of the cable), given in Figure 1 as a function of the
cable diameter.
NOTE 1 The correction factors given in Figure 2 are approximate and depend mainly upon the diameter of the
cable. In general, the half-an-hour service is applicable to mooring winches. The half-an-hour rating might not be
adequate for automatic tensioning mooring winches.
NOTE 2 For cables supplying a single motor or other equipment intended to operate in an intermittent service, as
is generally the case for engine room cranes and similar devices, the current ratings as given by Annexes A and B
may be increased by applying the correction factor given by Figure 3.
NOTE 3 The correction factor given in Figure 3 has been roughly calculated for periods of 10 min, of which 4 min

are with a constant load and 6 min without load.

61892-4 © IEC:2007(E) – 19 –
Critical duration = 3 T
1,35
T = 0,245 x d
11,5 2 2,5 3 3,5 4 5 6 7 8 9 10 15 20 25 30 35 40 50 60 70 90 100
d = overall diameter of the cable (mm)
IEC  938/97
Figure 1 – Time constant of cables
T = time constant (min.)
– 20 – 61892-4 © IEC:2007(E)
2,2
1,12
Correction factor =
2,1
t
s
1 - exp -
T
For T, see Figure 2
2,0
1,9
1,8
1,7
1,6
1,5
1,4
1,3
t = 30´
s
1,2
t = 60´
s
1,1
1,0
0 10 20 3040 50 60 70 8090
Overall diameter of the cable (mm)
IEC  937/97
t = service time
s
Figure 2 – Correction factors for half-hour and one-hour service

Correction factor(s)
61892-4 © IEC:2007(E) – 21 –
1,7
1,6
1,5
1,4
-
1 - exp
T
Correction factor =
1,3
1 - exp -
T
1,3
1,2
1,1
0 10 20 3040 5060 70 80 90
Overall diameter of the cable (mm)
IEC  939/97
Intermittence period = 10 min Intermittence ratio = 40 %
Figure 3 – Correction factor for intermittent service
4.3.6 Correction factors for cable grouping
In the case of a group of insulated conductors or cables the current-carrying capacities
tabulated are subjected to the group correction factors given in 4.3.3 or the tables of Annex A.
The group reduction factors are applicable to groups of insulated conductors or cables having
the same maximum operating temperature.

For groups containing cables or insulated conductors having different maximum operating
temperatures, the current-carrying capacity of all the cables or insulated conductors in the
group shall be based on the lowest maximum operating temperature of any cable in the group
together with the appropriate
...