IEC 60287-1-2:2023

Electric cables - Calculation of the current rating - Part 1-2: Current rating equations (100 % load factor) and calculations of losses - Sheath eddy current loss factors for two circuits in flat formation

IEC 60287-1-2:2023 provides a method for calculating the eddy current losses in the metallic sheaths of single-core cables arranged as a three-phase double circuit in flat formation. The sheaths are bonded at one point or are cross-bonded so that there are no significant sheath circulating currents. Where metallic sheaths are bonded at both ends there are significant circulating currents which result in a lower current-carrying capacity. A method of calculating circulating current losses for double circuits is provided in IEC 60287-1-3.
The method descibed in this document provides coefficients which are applied as corrections to the loss factors for the sheaths of one isolated three-phase circuit. These corrections are negligible for cables where the parameter m is less than approximately 0,1 (m = ω/(Rs · 107)), which corresponds to a sheath longitudinal resistance higher than 314 µΩ/m at 50 Hz.
Consequently, the method is used for most sizes of aluminium-sheathed cables, but is not required for lead-sheathed cables unless they are unusually large.
The coefficients are provided in tabular form and have been computed from fundamental formulae for sheath losses, the evaluation of which calls for expertise in computer programming which will possibly not be readily available in general commercial situations. The development of simplified formulae for some of the tabulated coefficients is under consideration.
Losses for cables in a single circuit is covered in IEC 60287-1-1.

General Information

• Status: Published
• Publication Date: 11-May-2023
• ICS: 29.060.20 - Cables
• Technical Committee: TC 20 - Electric cables
• Drafting Committee: WG 19 - TC 20/WG 19
• Current Stage: PPUB - Publication issued
• Start Date: 09-Jun-2023
• Completion Date: 12-May-2023

Standards Content (Sample)

IEC 60287-1-2 ®
Edition 2.0 2023-05
INTERNATIONAL
STANDARD
Electric cables – Calculation of the current rating –
Part 1-2: Current rating equations (100 % load factor) and calculations of losses –
Sheath eddy current loss factors for two circuits in flat formation

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IEC 60287-1-2 ®
Edition 2.0 2023-05
INTERNATIONAL
STANDARD
Electric cables – Calculation of the current rating –

Part 1-2: Current rating equations (100 % load factor) and calculations of losses –

Sheath eddy current loss factors for two circuits in flat formation

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.060.20  ISBN 978-2-8322-6972-5

– 2 – IEC 60287-1-2:2023 © IEC 2023
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms, definitions and symbols. 5
3.1 Terms and definitions . 5
3.2 Symbols . 6
4 Description of method . 7
4.1 General . 7
4.2 Outline of method . 7
4.3 Criteria for use of formulae and coefficients . 8
5 Formulae for sheath loss factors for high-resistance sheaths in a single circuit, λ . 8
0s
6 Calculation of the coefficients C , C and C . 9
H N J
6.1 Allocation of coefficients to each cable, time sequence and phase
identification . 9
6.2 Calculation of coefficients C (1, 2 and 3), Table 1 . 10
H
6.3 Calculation of coefficients C (1, 2, 3, 4, 5 and 6), Table 2 . 11
N
6.4 Calculation of coefficients C (1, 2, 3, 4, 5 and 6), Table 3 to Table 11 . 11
J
6.5 Calculation of coefficients G and g . 13
s s
7 Notes on transposition of cables . 14
8 Worked examples of calculation of eddy current losses . 14
8.1 Overview . 14
8.2 Example 1 . 14
8.3 Example 2 . 16
Bibliography . 30

Figure 1 – Cable configuration . 8

Table 1 – C coefficients . 19
H
Table 2 – C coefficients . 20
N
Table 3 – C coefficients . 21
J
Table 4 – C coefficients . 22
J
Table 5 – C coefficients . 23
J
Table 6 – C coefficients . 24
J
Table 7 – C coefficients . 25
J
Table 8 – C coefficients . 26
J
Table 9 – C coefficients . 27
J
Table 10 – C coefficients . 28
J
Table 11 – C coefficients . 29
J
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRIC CABLES –
CALCULATION OF THE CURRENT RATING –

Part 1-2: Current rating equations
(100 % load factor) and calculation of losses –
Sheath eddy current loss factors for two circuits in flat formation

FOREWORD
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IEC 60287-1-2 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 1993. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the symbols have been harmonized and aligned with the symbols used in the IEC 60287
and IEC 60853 series.
– 4 – IEC 60287-1-2:2023 © IEC 2023
The text of this International Standard is based on the following documents:
Draft Report on voting
20/2097/FDIS 20/2104/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,
• replaced by a revised edition, or
• amended.
ELECTRIC CABLES –
CALCULATION OF THE CURRENT RATING –

Part 1-2: Current rating equations
(100 % load factor) and calculation of losses –
Sheath eddy current loss factors for two circuits in flat formation

1 Scope
This part of IEC 60287 provides a method for calculating the eddy current losses in the metallic
sheaths of single-core cables arranged as a three-phase double circuit in flat formation. The
sheaths are bonded at one point or are cross-bonded so that there are no significant sheath
circulating currents. Where metallic sheaths are bonded at both ends there are significant
circulating currents which result in a lower current-carrying capacity. A method of calculating
circulating current losses for double circuits is provided in IEC 60287-1-3.
The method descibed in this document provides coefficients which are applied as corrections
to the loss factors for the sheaths of one isolated three-phase circuit. These corrections are
negligible for cables where the parameter m is less than approximately 0,1 (m = ω/(R · 10 )),
s
which corresponds to a sheath longitudinal resistance higher than 314 µΩ/m at 50 Hz.
Consequently, the method is used for most sizes of aluminium-sheathed cables, but is not
required for lead-sheathed cables unless they are unusually large.
The coefficients are provided in tabular form and have been computed from fundamental
formulae for sheath losses, the evaluation of which calls for expertise in computer programming
which will possibly not be readily available in general comme
...