IEC 60287-2-3:2024

IEC 60287-2-3 ®
Edition 2.0 2024-06
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Electric cables – Calculation of the current rating –
Part 2-3: Thermal resistance – Cables installed in ventilated tunnels

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IEC 60287-2-3 ®
Edition 2.0 2024-06
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Electric cables – Calculation of the current rating –
Part 2-3: Thermal resistance – Cables installed in ventilated tunnels
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.060.20 ISBN 978-2-8322-9370-6

– 2 – IEC 60287-2-3:2024 RLV © IEC 2024
CONTENTS
FOREWORD . 4
INTRODUCTION . 2
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and symbols. 7
3.1 Terms and definitions . 7
3.2 Symbols . 8
4 Description of method . 9
4.1 General description . 9
4.2 Basic formulae . 10
4.2.1 General . 10
4.2.2 Radial heat transfer by conduction within the cable . 11
4.2.3 Heat transfer by radiation from the cable surface to the inner wall of the
tunnel . 11
4.2.4 Heat transfer by convection from the cable surface to the air inside the
tunnel . 12
4.2.5 Heat transfer by convection from the air inside the tunnel to the inner
tunnel wall . 14
4.2.6 Longitudinal heat transfer by convection resulting from the forced or
natural flow of air along the tunnel . 14
4.2.7 Radial heat conduction in the soil surrounding the tunnel. 15
4.3 Set of formulae . 16
4.4 Solving . 17
4.5 Iterative process . 19
5 Formulae for air properties . 20
6 Temperature profile . 20
Annex A (informative) Calculation example . 22
A.1 Cable and installation . 22
A.2 Calculated values . 22
Annex B (informative) Delta-star transformation . 25
Annex C (informative) Calculation of Fm C coefficient. 27
Fm
C.1 Definition of spacing . 27
C
C.2 Calculation of coefficient . 27
Fm
Bibliography . 29

Figure A.1 – Temperature profile along a 1 km tunnel . 24
Figure A.2 – Temperature profile along a 10 km tunnel . 24
Figure B.1 – Delta-star transformation . 26
Figure C.1 – Spacing definitions . 27

Table 1 – F C coefficient for radiation thermal resistance calculation . 12
F
m
m
Table 2 – Values of parameter K . 14
cv
Table A.1 – Installation data . 22
Table A.2 – Iterative process for a 1 km long tunnel . 23

Table C.1 – Expression for F C coefficient calculation . 28
m F
m
– 4 – IEC 60287-2-3:2024 RLV © IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRIC CABLES –
CALCULATION OF THE CURRENT RATING –

Part 2-3: Thermal resistance – Cables installed in ventilated tunnels

FOREWORD
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This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition IEC 60287-2-3:2017. A vertical bar appears in the margin
wherever a change has been made. Additions are in green text, deletions are in
strikethrough red text.
IEC 60287-2-3 has been prepared by IEC technical committee 20: Electric cables. It is an
International Standard.
This second edition cancels and replaces the first edition published in 2017. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) symbols alignment with other parts of the IEC 60287 series.
The text of this International Standard is based on the following documents:
Draft Report on voting
20/2175/FDIS 20/2182/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 60287 series, published under the general title Electric cables –
Calculation of the current rating, can be found on the IEC website.
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.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

– 6 – IEC 60287-2-3:2024 RLV © IEC 2024
INTRODUCTION
In the IEC 60287 series, IEC 60287-1 provides general formulae for ratings and power losses
of electric cables.
The IEC 60287-2 series presents formulae or calculation method
...