IEC 60287-3-2:2012

IEC 60287-3-2 ®
Edition 2.0 2012-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electric cables – Calculation of the current rating –
Part 3-2: Sections on operating conditions – Economic optimization of power
cable size
Câbles électriques – Calcul du courant admissible –
Partie 3-2: Sections concernant les conditions de fonctionnement – Optimisation
économique des sections d'âme de câbles électriques de puissance

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IEC 60287-3-2 ®
Edition 2.0 2012-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electric cables – Calculation of the current rating –

Part 3-2: Sections on operating conditions – Economic optimization of power

cable size
Câbles électriques – Calcul du courant admissible –

Partie 3-2: Sections concernant les conditions de fonctionnement – Optimisation

économique des sections d'âme de câbles électriques de puissance

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX W
ICS 29.060.20 ISBN 978-2-83220-151-0

– 2 – 60287-3-2 © IEC:2012
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 8
2 Normative references . 8
3 Symbols . 8
4 Calculation of total costs . 10
5 Determination of economic conductor sizes . 13
5.1 First approach: economic current range for each conductor in a series of
sizes . 13
5.2 Second approach: economic conductor size for a given load . 13
5.2.1 General equation . 13
5.2.2 Linear cost function for cable costs. 14
5.2.3 Effect of charging current and dielectric losses . 15
Annex A (informative) Examples of calculation of economic conductor sizes . 17
Annex B (informative) Mean conductor temperature and resistance . 33
Bibliography . 38

Figure A.1 – System layout . 26
Figure A.2 – Economic current ranges . 27
Figure A.3 – Variation of cost with conductor size . 28

2 2
Table A.1 – Economic current ranges for cable sizes 25 mm to 400 mm . 19
Table A.2 – Summary of costs . 23
Table A.3 – Cable details . 23
Table A.4 – Economic loading . 24
Table A.5 – Current-carrying capacity criterion . 24
Table A.6 – Economic loading, standard conductor size for all sections – Standard
size: 150 mm2 . 25
Table A.7 – Economic loading, standard conductor size for all sections – Standard
size: 185 mm . 25
Table A.8 – Economic loading, standard conductor size for all sections – Standard
size: 240 mm . 26
Table A.9 – Cable details . 29
Table A.10 – Steady state current ratings . 30
Table A.11 – Total costs . 31
Table A.12 – Total cost versus anticipated operational life . 31
Table A.13 – Losses versus anticipated operational life . 32
Table B.1 – Required data for conductor sizes for the above example . 34

60287-3-2 © IEC:2012 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRIC CABLES –
CALCULATION OF THE CURRENT RATING –

Part 3-2: Sections on operating conditions –
Economic optimization of power cable size

FOREWORD
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International Standard IEC 60287-3-2 has been prepared by IEC technical committee 20:
Electric cables.
This second edition cancels and replaces the first edition, published in 1995 and its
Amendment 1:1996. This edition consitutes a technical revision. This edition incorporates
Amendment 2 which was not published separately due to the number of changes and pages.
The main changes with respect to the previous edition are as follows:
– update of the normative references;
– clarification of some symbols;
– correction of some formulae;
– introduction of a second example in Annex A for the calculation of the economic conductor
size.
– 4 – 60287-3-2 © IEC:2012
The text of this standard is based on the first edition, its amendment 1 and the following
documents:
FDIS Report on voting
20/1367/FDIS 20/1373/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.
A list of all parts in the IEC 60287 series can be found on the IEC
...