SIST-TP IEC TR 61439-0:2023

IEC TR 61439-0 ®
Edition 3.0 2022-07
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
Low-voltage switchgear and controlgear assemblies –
Part 0: Guidance to specifying assemblies

Ensembles d’appareillage à basse tension –
Partie 0: Recommandations pour la spécification d’ensembles

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IEC TR 61439-0 ®
Edition 3.0 2022-07
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
Low-voltage switchgear and controlgear assemblies –

Part 0: Guidance to specifying assemblies

Ensembles d’appareillage à basse tension –

Partie 0: Recommandations pour la spécification d’ensembles

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.130.20 ISBN 978-2-8322-4027-4

– 2 – IEC TR 61439-0:2022 © IEC 2022
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 10
2 Normative references . 10
3 Terms and definitions . 11
4 Application of assemblies within the IEC 61439 series . 11
4.1 General . 11
4.2 Assembly design and verification . 11
4.3 Service conditions and interface characteristics . 13
4.4 Application design . 13
5 Electrical system . 13
5.1 General . 13
5.2 Earthing system . 13
5.3 Nominal voltage . 14
5.4 Transient overvoltages . 14
5.5 Unusual voltage transients, temporary overvoltages . 16
5.6 Rated frequency f (Hz) . 16
n
5.7 Additional on-site testing requirements: wiring, operational performance and
function . 17
6 Short-circuit withstand capability . 17
6.1 General . 17
6.2 Prospective short-circuit current at supply terminals I (kA) . 18
cp
6.3 Prospective short-circuit current in the neutral . 19
6.4 Prospective short-circuit current in the protective circuit . 19
6.5 Short-circuit protective device (SCPD) . 19
6.6 Coordination of short-circuit protective devices including external short-
circuit protective device details . 20
6.7 Data associated with loads likely to contribute to the short-circuit current . 21
6.8 Multiple supplies . 21
7 Protection of persons against electric shock . 21
7.1 General . 21
7.2 Basic protection (protection against direct contact) . 21
7.2.1 General . 21
7.2.2 Basic insulation provided by insulating material . 22
7.2.3 Basic insulation by barriers or enclosures . 22
7.3 Fault protection (protection against indirect contact) . 22
7.3.1 General . 22
7.3.2 Requirements for the protective conductor to facilitate automatic
disconnection of the supply . 23
7.3.3 Electrical separation . 24
7.3.4 Class II protection (double or reinforced insulation) . 24
8 Installation environment . 24
8.1 General . 24
8.2 Location type . 24
8.3 Protection against access to hazardous parts, ingress of solid foreign bodies
and ingress of water (IP code) . 25

8.4 External mechanical impact (IK code) . 28
8.5 Resistance to radiation . 29
8.5.1 General . 29
8.5.2 Solar irradiance . 29
8.5.3 Ultraviolet (UV) radiation . 29
8.6 Resistance to corrosion . 29
8.7 Ambient air temperature . 30
8.8 Maximum relative humidity . 30
8.9 Pollution degree . 31
8.10 Altitude . 32
8.11 Electromagnetic compatibility (EMC) . 32
8.12 Special service conditions . 33
8.12.1 General . 33
8.12.2 Climatic conditions . 34
8.12.3 Protection against ingress of solid foreign bodies and ingress of water
(IP code) . 34
8.12.4 Shock, vibration, seismic occurrence and external mechanical impact

(IK code) . 34
8.12.5 Fire and explosion hazards . 34
8.12.6 Exceptional overvoltages . 34
8.12.7 Polluted atmospheres . 35
8.12.8 EMC environment . 35
9 Installation method . 35
9.1 General . 35
9.2 Assembly type . 35
9.3 Portability . 36
9.4 Maximum overall dimensions and weight . 36
9.5 External conductor type(s) . 36
9.6 Direction(s) of external conductors . 37
9.7 External conductor material . 37
9.8 External line conductor, cross sections, and terminations . 37
9.9 External PE, N, PEN, PEM, PEL conductors’ cross sections, and
terminations . 37
9.10 Special terminal identification requirements . 38
10 Storage and handling. 38
10.1 General . 38
10.2 Maximum dimensions and weight of transport units . 38
10.3 Methods of transport (e.g. forklift, crane) . 38
10.4 Environmental conditions different from the service conditions . 39
10.5 Packing details . 39
11 Operating arrangements . 39
11.1 General . 39
11.2 Access to manually operated devices . 39
12 Maintenance and upgrade capabilities . 40
12.1 General . 40
12.2 Requirements related to accessibility for inspection and similar operations . 40
12.3 Requirements related to accessibility for maintenance in service by
authorized persons . 41
12.4 Requirements related to extension under voltage . 41

– 4 – IEC TR 61439-0:2022 © IEC 2022
12.5 Protection against direct contact with hazardous live internal parts during
maintenance or upgrade . 41
12.6 Method of functional unit connection . 42
12.7 Operating and maintenance gangways within an assembly . 42
12.8 Internal separation (only relevant for assemblies in accordance with

IEC 61439-2) . 42
12.8.1 Fundamentals of separation . 42
12.8.2 Considerations when determining a form of separation . 43
12.8.3 Selecting the most appropriate form of separation . 44
13 Current carrying capability . 46
13.1 General . 46
13.2 Rated current of the assembly I (A) (maximum current allowable) . 46
nA
13.3 Loading of outgoing circuits within an assembly . 47
13.4 Ratio of cross section of the neutral conductor to line conductors . 48
13.4.1 General . 48
13.4.2 Line conductors up to and including 16 mm . 48
13.4.3 Line conductors above 16 mm . 48
14 Assembly design and routine verification processes . 49
14.1 Design verification . 49
14.1.1 Object . 49
14.1.2 Methods . 49
14.1.3 Records . 50
14.2 Routine verification . 50
14.2.1 General . 50
14.2.2 Records . 50
Annex A (informative) Cross section of copper cables suitable for connection to
terminals for external cables . 51
Annex B (informative) Forms of internal separation (see 12.8) . 52
Annex C (informative) Specification template for assemblies . 58
Annex D (informative) Optional information . 62
D.1 General . 62
D.2 Electrical conditions . 63
D.2.1 Internal arc-fault considerations . 63
D.2.2 Insulated busbars . 64
Annex E (informative) List of notes concerning certain countries . 65
Bibliography . 66

Figure 1 – Required rated impulse withstand voltage . 16
Figure 2 – Examples of separation included in IEC 61439-2 . 45
Figure B.1 – Symbols used in Figure B.2, Figure B.3 and Figure B.4 . 53
Figure B.2 – Form 1 and Form 2 . 55
Figure B.3 – Form 3 . 56
Figure B.4 – Form 4 . 57

Table 1 – IP codes, first numeral . 26
Table 2 – IP codes, second numeral . 27

Table 3 – IP codes, additional letter (optional) . 28
Table 4 – Assemblies and application ratings . 48
Table A.1 – Cross section of copper cables suitable for connection to terminals for
external cables . 51
Table B.1 – Forms of internal separation. 52
Table C.1 – Example of items typically subject to agreement between the assembly
manufacturer and the user . 58
Table D.1 – Examples of optional items subject to agreement between the assembly
manufacturer and the specifier . 62

– 6 – IEC TR 61439-0:2022 © IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LOW-VOLTAGE SWITCHGEAR AND CONTROLGEAR ASSEMBLIES –

Part 0: Guidance to specifying assemblies

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
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preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
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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
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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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.
IEC TR 61439-0 has been prepared by subcommittee 121B: Low-voltage switchgear and
controlgear assemblies, of IEC technical committee 121: Switchgear and controlgear and their
assemblies for low voltage. It is a Technical Report.
This third edition cancels and replaces the second edition published in 2013. It constitutes a
technical revision.
This third edition includes the following significant technical changes with respect to the
previous edition:
a) alignment with IEC 61439-1:2020;
b) addition of new content in Clause 13 regarding current ratings;
c) addition of a new subclause 12.8.1 detailing the fundamentals of the forms of internal
separation;
d) alignment of Annex B with Annex AA of 61439-2:2020;
e) removal of the annexes detailing items subject to agreement between specifier and
manufacturer for all product parts as not all of them can always be up to date

The text of this Technical Report is based on the following documents:
Draft Report on voting
121B/126/DTR 121B/152/RVDTR
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 Technical Report 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/standardsdev/publications.
The reader’s attention is drawn to the fact that Annex E lists all of the “in-some-country” clauses
on differing practices of a less permanent nature relating to the subject of this document.
A list of all parts of the IEC 61439 series, under the general title Low-voltage switchgear and
controlgear assemblies, can be found on the IEC web site.
The committee has decided that the contents of this publication will remain unchanged until the
stability 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.
– 8 – IEC TR 61439-0:2022 © IEC 2022
INTRODUCTION
Low-voltage assemblies form an integral part of most electrical distribution networks. In their
application they have two prime functions:
– to safely control and distribute electrical energy; and
– to safely isolate sections of faulted networks.
Whilst these two functions place very different demands on the assembly, an assembly has to
be capable of performing both these functions throughout its expected service life. Controlling
and distributing electrical energy is the assembly’s routine ongoing duty. The second function,
fault management, is a very rare occurrence within a well-managed and maintained system.
Some assemblies will never be called upon to manage a fault, but if a fault does occur, it can
place immense thermal and mechanical stresses on the assembly in an instant. Any ageing or
deterioration of the assembly should be limited such that its safety function is not impaired.
Due to the nature of the application, if there are weaknesses in the design or application of an
assembly, it is possible they will not be identified until years after the assembly was installed.
In order to avoid latent issues, and to ensure that assemblies are suitable for their application,
they will be designed and verified to meet the exacting requirements defined in the IEC 61439
series of standards. However, as the IEC 61439 series covers a wide range of applications, and
some applications can be partially outside the scope of the standard, it is equally important that
assemblies are correctly specified. Where options are given in the IEC 61439 series, the most
suitable for the application will be selected; where the requirements are outside the scope of
the standards, detailed requirements will be agreed between the specifier and manufacturer.
This document identifies the significance of each characteristic to be considered when
specifying an assembly and provides the specifier with guidance on defining a suitable
assembly for their application.
For the purposes of this document, the specifier is the party who specifies or selects the
assembly characteristics. The specifier may be the same party as the one who will use and
operate the assembly, or someone acting on their behalf. The aim of this document is to provide
the specifier with guidance on the specification that should be provided in order to obtain an
assembly with the required performance and at optimised costs.
Throughout this document, the term “assembly” is used for a low-voltage switchgear and
controlgear assembly. The term “manufacturer” refers to the assembly manufacturer unless
specifically indicated otherwise.
The term “line conductor” is used in many places throughout this document. Previously the
terminology was phase conductors.
This document is focussed on the specifier, that is, the person or organization providing the
specification for the assembly. It is assumed the specifier is acting on behalf of the user.
The purpose of the IEC 61439 series of standards is to harmonize, as far as practicable, all the
general rules and requirements that apply to assemblies. The series further seeks, in order to
obtain uniformity of requirements for assemblies, consistency in the verification of assemblies
and to avoid the need for verification to other standards.
All the requirements for the various assemblies that can be considered as general, together
with specific subjects dedicated to performances and application, for example temperature rise,
short-circuit, dielectric properties, have therefore been gathered in IEC 61439-1 as general
rules. For each type of assembly only two main standards are necessary to determine all
requirements and the corresponding methods of verification:
1) the standard giving the general rules designated “IEC 61439-1”, and

2) the specific product part of the IEC 61439 series, hereinafter referred to as the relevant
product part of the IEC 61439 series.
The IEC 61439 series of standards encompasses assemblies for a wide variety of uses, some
of which have specific needs as imposed by their particular application. In order to clearly define
these specific needs, relevant product parts of the IEC 61439 series focussed on a particular
type of application have been (or are being) developed. These are identified as IEC 61439-2,
IEC 61439-3, and so on (for a list of all parts of the IEC 61439 series, refer to the IEC web site).
Each relevant product part of the IEC 61439 series with reference to IEC 61439-1, the general
rules, as appropriate, specifies the characteristics and performance required by an assembly
within its defined scope of application. Each relevant product part of the IEC 61439 series
includes, as an annex, a template for “items subject to agreement between the assembly
manufacturer and the specifier” to facilitate the specifying of an assembly.
General characteristics of all types of assemblies are considered in this document. Details
which are applicable to each type of assembly can be determined by reference to the
specification schedule in the relevant product part of the IEC 61439 series.
Within this document, reference to IEC 61439 means the current edition of the IEC 61439 series
of standards, including:
• IEC 61439-1, Low-voltage switchgear and controlgear assemblies – Part 1: General rules
• IEC 61439-2, Low-voltage switchgear and controlgear assemblies – Part 2: Power
switchgear and controlgear assemblies
• IEC 61439-3, Low-voltage switchgear and controlgear assemblies – Part 3: Distribution
boards intended to be operated by ordinary persons (DBO)
• IEC 61439-4, Low-voltage switchgear and controlgear assemblies – Part 4: Particular
requirements for assemblies for construction sites (ACS)
• IEC 61439-5, Low-voltage switchgear and controlgear assemblies – Part 5: Assemblies for
power distribution in public networks
• IEC 61439-6, Low-voltage switchgear and controlgear assemblies – Part 6: Busbar trunking
systems (busways)
• IEC 61439-7, Low-voltage switchgear and controlgear assemblies – Part 7: Assemblies for
specific applications such as marinas, camping sites, market squares, electric vehicles
charging stations
Refer to the IEC web site for the latest edition of each product part of the IEC 61439 series and
additional product part of the IEC 61439 series published for other specific applications.
NOTE Each product part of the IEC 61439 series is related to the appropriate edition of IEC 61439-1, as listed in
the product part, and the corresponding edition of IEC TR 61439-0.
A reference to “general rules” means a reference to IEC 61439-1:2020.
A reference to “product standard” means the relevant part or parts of the IEC standard for the
components used in the assembly (e.g. IEC 60947-2 for circuit-breakers).

– 10 – IEC TR 61439-0:2022 © IEC 2022
LOW-VOLTAGE SWITCHGEAR AND CONTROLGEAR ASSEMBLIES –

Part 0: Guidance to specifying assemblies

1 Scope
Within the IEC 61439 series of standards for low-voltage switchgear and controlgear
assemblies, there are system and application details that are specified by the specifier to enable
the manufacturer to produce an assembly that meets the needs and expectations of the specifier.
This part of IEC 61439, which is a technical report, identifies from the specifier’s perspective
those functions and characteristics that are defined when specifying assemblies. It provides:
– an explanation of the assembly characteristics and options within the IEC 61439 series;
– a guidance on how to select the appropriate options and define characteristics so as to meet
specific application needs; and
– an assistance in the specification of assemblies.
References within this document to the interface characteristics of an assembly and the
requirements with which they will comply assume that the assembly is designed, manufactured,
and verified in accordance with the relevant part of the IEC 61439 series.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
IEC 61439 (all parts), Low-voltage switchgear and controlgear assemblies
IEC 61439-1:2020, Low-voltage switchgear and controlgear assemblies – Part 1: General rules
IEC 61439-2:2020, Low-voltage switchgear and controlgear assemblies – Part 2: Power
switchgear and controlgear assemblies
IEC 61439-3, Low-voltage switchgear and controlgear assemblies – Part 3: Distribution boards
intended to be operated by ordinary persons (DBO)
IEC 61439-4, Low-voltage switchgear and controlgear assemblies – Part 4: Particular
requirements for assemblies for construction sites (ACS)
IEC 61439-5, Low-voltage switchgear and controlgear assemblies – Part 5: Assemblies for
power distribution in public networks
IEC 61439-6, Low-voltage switchgear and controlgear assemblies – Part 6: Busbar trunking
systems (busways)
IEC 61439-7, Low-voltage switchgear and controlgear assemblies – Part 7: Assemblies for
specific applications such as marinas, camping sites, market squares, electric vehicle charging
stations
3 Terms and definitions
For the purposes of this document, the terms and definitions given in the IEC 61439 series
apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 Application of assemblies within the IEC 61439 series
4.1 General
Assemblies manufactured in accordance with the relevant product part of the IEC 61439 series
are suitable for installation in the majority of operating environments. Many of the
characteristics of assemblies are fully defined within the standard and do not require further
consideration by the specifier. In some instances, there can be a default condition specified
within the standard and a range of other identified alternative options, from which the specifier
can choose to suit the application. For other characteristics, the specifier can be required to
choose from a list of options within the standard.
Specifiers are cautioned against over-specifying their requirements; it may not lead to a more
appropriate assembly for their application. More onerous requirements for one criterion usually
have a negative impact on others. For example, an outdoor assembly being specified to comply
with IP66 of IEC 60529, when a lower IP degree, for example IP33, will suffice, can:
– increase temperatures within the assembly due to the lack of ventilation with the effect that
the insulation ages more quickly;
– increase the risk of condensation causing tracking due to there being no ventilation and
therefore no air exchange with the environment outside of the assembly; and
– make the assembly larger and more expensive due to the need to manage the lack of
ventilation.
If special and exceptionally onerous conditions are likely to exist, these conditions should be
identified by the specifier. Examples of these onerous conditions include high ultraviolet (UV)
radiation applications, conditions of high particulates/pollutants, more stringent short-circuit
conditions, special fault protection, special protection due to risk of fire, internal arc-faults,
explosions, burns, etc.
In some instances, the specifier can wish to seek the advice of experts in order to identify their
requirements correctly, for example the cross section of the neutral conductor considering the
system harmonics.
Annex C is typical of the items to be agreed between the specifier and manufacturer when
specifying an assembly. The equivalent annex for each product can be found in the relevant
part of the IEC 61439 series. The specifier should complete the appropriate annex when
defining the interface characteristics for the assembly for their particular application. An
explanation of each interface characteristic is given in Clause 5 to Clause 14 inclusive.
Annex D provides guidance on optional information that a specifier may require for their specific
application.
4.2 Assembly design and verification
An assembly is intended to be used within an electrical installation of defined characteristics.
The assembly can be designed and verified with a specific set of application criteria, to suit a

– 12 – IEC TR 61439-0:2022 © IEC 2022
particular use, or more usually, it can be designed and verified to meet typical application
criteria that make it usable in a range of common applications.
The configuration for a particular specifier application of an assembly usually requires four main
steps:
a) Specification of the requirements and functions particular to the application. The specifier
should complete the table given in Annex C of the relevant product part of the IEC 61439
series.
b) The manufacturer derives the necessary interface characteristics and design of the
assembly to meet the specification. The design will generally be based on the
manufacturer’s previously developed assembly arrangements, characteristics and
functions.
c) For assemblies or parts of assemblies where the design is not previously proven, design
verification is carried out by the manufacturer.
d) Routine verification, carried out on each assembly by the manufacturer.
It is essential that the specifier always insists upon assemblies that are fully verified in
accordance with the appropriate product part of the IEC 61439 series. The nature of the
application is such that deficiencies in an assembly design may not be initially apparent or
readily identified from a cursory examination. For example:
1) The complex thermal effects within an assembly cannot be determined without formal
verification (test, comparison or assessment). Operating components, particularly
insulation, within an assembly at temperatures higher than intended may not cause an
immediate failure but accelerated ageing of insulation can cause a premature failure.
2) Short-circuit protective devices operate rarely during the lifetime of the assembly to interrupt
a fault. When some types of short-circuit protective devices interrupt a fault, they emit a hot
ionized gas which can bridge clearances and/or reduce creepage distances and cause a
flashover within the assembly. There can also be sudden build-up of gas pressure within
the assembly that forces doors and covers to open, possibly endangering anyone in close
proximity.
3) On the rare occasions that a short-circuit occurs, there are complex magnetic effects
associated with high short-circuit currents. These impose substantial mechanical loads on
conductor supports. The forces on the supports are affected by the shape of the conductors,
bends in the conductors, proximity of conductors to each other and ferrous metalwork, phase
relationships between the current in different conductors, and transient effects. All these
effects
...