IEC 60364-5-52:2009/AMD1:2024

IEC 60364-5-52 ®
Edition 3.0 2024-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
AMENDMENT 1
AMENDEMENT 1
Low-voltage electrical installations –
Part 5-52: Selection and erection of electrical equipment – Wiring systems

Installations électriques à basse-tension –
Partie 5-52: Choix et mise en oeuvre des matériels électriques – Canalisations
IEC 60364-5-52:2009-10/AMD1:2024-11(en-fr)

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IEC 60364-5-52 ®
Edition 3.0 2024-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
AMENDMENT 1
AMENDEMENT 1
Low-voltage electrical installations –

Part 5-52: Selection and erection of electrical equipment – Wiring systems

Installations électriques à basse-tension –

Partie 5-52: Choix et mise en oeuvre des matériels électriques – Canalisations

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 13.260, 91.140.50 ISBN 978-2-8322-9969-2

– 2 – IEC 60364-5-52:2009/AMD1:2024
© IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LOW-VOLTAGE ELECTRICAL INSTALLATIONS –

Part 5-52: Selection and erection of electrical equipment –
Wiring systems
AMENDMENT 1
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 this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
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preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
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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
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
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shall not be held responsible for identifying any or all such patent rights.
Amendment 1 to IEC 60364-5-52:2009 has been prepared by IEC technical committee 64:
Electrical installations and protection against electrical shock.
The text of this Amendment is based on the following documents:
Draft Report on voting
64/2675/FDIS 64/2703/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
© IEC 2024
The language used for the development of this Amendment 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/.
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.
___________
520.2 Normative references
Add the following new reference:
IEC 60364-4-43:2023, Low-voltage electrical installations – Part 4-43: Protection for safety –
Protection against overcurrent
524 Cross-sectional areas of conductors
524.2 Cross-sectional area of the neutral conductor
Replace the existing Subclause 524.2 with the following new Subclause 524.2:
524.2 Cross-sectional area of the neutral conductor
The cross-sectional area of the neutral conductor, if any, shall be at least equal to the
cross-sectional area of the line conductors:
– in single-phase circuits; or
– in polyphase circuits where the cross-sectional area of the line conductors is less than or
2 2
equal to 16 mm copper or 25 mm aluminium.
In all other cases, the cross-sectional area of the neutral conductor may be less than that of
the line conductors and:
2 2
– shall be at least 16 mm copper or 25 mm aluminium; and
– shall not be less than 50 % of the cross-sectional area of the line conductors.
Where triplen harmonics are present, see 524.3.
Add, at the end of 524.2, the following new Subclause 524.3:
524.3 Cross-sectional area of live conductors with triplen harmonics
In three-phase circuits where the third harmonic and multiples of third harmonic currents are
expected to flow, the cross-sectional area of the line conductors and the neutral conductor may
be selected in accordance with Annex E.

– 4 – IEC 60364-5-52:2009/AMD1:2024
© IEC 2024
Where cross-sectional areas are not selected in accordance with Annex E,
IEC 60364-4-43:2023, 431.2.3 shall be taken into consideration.
___________
Annex E
Replace the existing Annex E with the following new Annex E:
Annex E
(normative)
Effect of harmonic currents on balanced three-phase systems
E.52.1 General
Subclause 523.6.3 states that where the neutral conductor carries current without a
corresponding reduction in load of the line conductors, the current flowing in the neutral
conductor shall be taken into account in ascertaining the current-carrying capacity of the circuit.
This annex is intended to cover the situation where currents in the line conductors of a balanced
three-phase system have triplen harmonics content which are superimposed in the neutral
conductor. The magnitude of the current in the neutral conductor due to triplen harmonics can
exceed the magnitude of the power frequency current in the line conductors. In such cases, the
current in the neutral conductor will have a significant effect on the current-carrying capacity of
the cables in the circuit.
The reduction factors given in this annex apply to balanced three-phase circuits; it is recognized
that the situation is more onerous if only two of the three line conductors are loaded. In this
situation, the neutral conductor will carry the harmonic currents in addition to the unbalanced
current. Such a situation can lead to overloading of the neutral conductor.
Equipment likely to cause significant harmonic currents are, for example, LED lighting banks
and DC power supplies such as those found in computers. Further information on harmonic
disturbances can be found in the IEC 61000 series.
The tabulated reduction factors only apply to cables where the neutral conductor is of the same
material as the line conductor and within a four-core or five-core cable or within a circuit of four
adjacent single-core cables or insulated conductors. These reduction factors have been
calculated based on triplen harmonic currents. The tabulated reduction factors, when applied
to the current-carrying capacity of a cable with three loaded conductors, will give the current-
carrying capacity of a cable with four loaded conductors where the current in the fourth
conductor is due to harmonics. The reduction factors also take the heating effect of the
harmonic current in the line conductors into account.
E.52.2 Reduction factors
The following symbols are used:
I design current, expressed in A;
B
I power frequency load current, expressed in A;
L
I total current in the line conductor, expressed in A;
lt
I current carrying capacity, expressed in A;
z
© IEC 2024
I current carrying capacity, expressed in A, in accordance with Annex B;
zB
k reduction factor;
P losses per unit length, expressed in W/m, generated in the cable with line conductors
z
only;
P losses per unit length, expressed in W/m, generated in the cable with line and neutral
zN
conductors;
r resistance per unit length, expressed in Ω/m, of line conductors;
l
r resistance per unit length, expressed in Ω/m, of the neutral conductor;
N
THD total harmonic current content, expressed in %;
i
THD total 3n harmonic current content, expressed in %.
i3n
The minimum cross-sectional area of the conductors shall be selected to provide a current-
carrying capacity not less than the power frequency load current, I thus:
L
I ≤ I =kI
(E.52.1)
L Z ZB
Where the design current I is given as a power frequency load current I , the reduction factor
B L
k provided in Table E.52.1 shall be applied.
Table E.52.1 – Reduction factors
a
Reduction factor k for the neutral CSA Reduction factor k for the neutral CSA
THD
i3n
equal to the line CSA half the line CSA
%
5 0,99 0,99
10 0,98 0,97
15 0,96 0,93
20 0,93 NA
25 0,89 NA
30 0,86 NA
35 0,82 NA
40 0,78 NA
45 0,74 NA
50 0,71 NA
Key
CSA cross-sectional area
NA not applicable, see 523.6.3
NOTE The triplen harmonics current in the neutral conductor is, due to the superimposing, three times the triplen
harmonics current in the line conductors.
a
Where the value of THD is not known, apply the value of THD .
i3n i
The reduction factor k given in Table E.52.1 is based on the following:
The current-carrying capacity, I , of a three-phase loaded cable is the current that can flow in
zB
the live conductors where the heat generated by the losses in the conductors are balanced with
the heat dissipation from the cable without causing the temperature of the insulation of the
conductors to exceed its maximum allowed temperature under normal operation.

– 6 – IEC 60364-5-52:2009/AMD1:2024
© IEC 2024
The losses of the cable are then:
(E.52.2)
P = 3rI
z l zB
When a harmonic current, given as a THD of the line current, is added to the line current, the
i3n
total line current will be:
2 22
(E.52.3)
I I+THD I
lt l i3n l
The total losses of the cable when the harmonic current is flowing in the neutral conductor and
,
the power frequency load current of the line conductors, I is set to I , will be:
L z
2 22
P =3r I ++T HD I r (3T HD I ) (E.52.4)

zN l( z i3n z) N i3n z
If the losses in the cables while carrying a harmonic current in the neutral conductor are not
exceeding the maximum losses that can be generated without harmonic current in the neutral
conductor, the conductors are not likely to exceed their maximum allowed temperature under
normal operation. Thus, a reduction factor to the line current is introduced in Equation (E.52.4),
resulting in:
22 2 2 2 2
P=3 r k I + k T HD I + r3T HD kI = P=3rI
( ) (E.52.5)
zN l( zB i3n zB) N i3n zB z l zB

k =
r (E.52.6)
N
1++1 3 THD

i3n
r
l
Considering that the line conductors and the neutral conductor have the same cross-sectional
area and are made of the same conductor material, the reduction factors shown in Table E.52.1
are expressed as:
k =
(E.52.7)
14+ THD
i3n
=
© IEC 2024
Where the cross-sectional area of the neutral conductor is equal to half the cross-sectional area
of the line conductor, i.e. r = 2 × r , the k factor becomes:
N l
k =
half N
(E.52.8)
17+ THD
i3n
Where the design current I is given as a total load current I , the reduction factors may be
B lt
calculated according to the following Formula (E.52.9):
k =
THD (E.52.9)
i3n
13+
1 +T HD
i3n
E.52.3 Examples of the application of reduction factors for harmonic currents
Consider a three-phase and neutral circuit with a
...