IEC 60364-5-53:2019

Low-voltage electrical installations - Part 5-53: Selection and erection of electrical equipment - Devices for protection for safety, isolation, switching, control and monitoring

IEC 60364-5-53:2019 Deals with general requirements for isolation, switching and control and with the requirements for selection and erection of the devices provided to fulfil such functions. This fourth edition cancels and replaces the third edition published in 2001, Amendment 1:2002 and Amendment 2:2015. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) revision of all clauses except 531 and 534;
b) introduction of a new Clause 537 Monitoring;
c) Clause 530 contains all normative references and all terms and definitions.

Installations électriques à basse tension - Partie 5-53: Choix et mise en œuvre des matériels électriques – Dispositifs de protection pour assurer la sécurité, le sectionnement, la coupure, la commande et la surveillance

L'IEC 60364-5-53:2019 traite des exigences relatives:
a) au sectionnement, à la coupure, à la commande et à la surveillance, et
b) au choix et à la mise en œuvre des:
1) dispositifs pour le sectionnement, la coupure, la commande et la surveillance, et
2) dispositifs pour assurer la conformité aux mesures de protection en vue de la sécurité.
Cette quatrième édition annule et remplace la troisième édition parue en 2001, l’Amendement 1:2002 et l’Amendement 2:2015. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) révision de tous les articles à l’exception des articles 521 et 534;
b) introduction d’un nouvel Article 537, Surveillance;
c) l’Article 530 contient toutes les références normatives et l’ensemble des termes et définitions.

General Information

• Status: Published
• Publication Date: 17-Dec-2024
• ICS: 29.130.01 - Switchgear and controlgear in general
• ICS: 91.140.50 - Electricity supply systems
• Technical Committee: TC 64 - Electrical installations and protection against electric shock
• Drafting Committee: MT 39 - TC 64/MT 39
• Current Stage: PPUB - Publication issued
• Start Date: 21-Feb-2019
• Completion Date: 22-Feb-2019

Relations

• Amended By: IEC 60364-5-53:2019/AMD2:2024 - Amendment 2 - Low-voltage electrical installations - Part 5-53: Selection and erection of electrical equipment - Devices for protection for safety, isolation, switching, control and monitoring
• Effective Date: 05-Sep-2023
• Amended By: IEC 60364-5-53:2019/AMD1:2020 - Amendment 1 - Low-Voltage electrical installations - Part 5-53: Selection and erection of electrical equipment - Devices for protection for safety, isolation, switching, control and monitoring
• Effective Date: 05-Sep-2023
• Revises: IEC 60364-5-53:2001/AMD2:2015 - Amendment 2 - Electrical installations of buildings - Part 5-53: Selection and erection of electrical equipment - Isolation, switching and control
• Effective Date: 05-Sep-2023
• Revises: IEC 60364-5-53:2001/AMD1:2002 - Amendment 1 - Electrical installations of buildings - Part 5-53: Selection and erection of electrical equipment - Isolation, switching and control
• Effective Date: 05-Sep-2023
• Revises: IEC 60364-5-53:2001 - Electrical installations of buildings - Part 5-53: Selection and erection of electrical equipment - Isolation, switching and control
• Effective Date: 05-Sep-2023

IEC 60364-5-53:2019 - Overview

IEC 60364-5-53:2019 is an international standard for low-voltage electrical installations covering the selection and erection of devices used for protection for safety, isolation, switching, control and monitoring. This consolidated fourth edition replaces earlier editions and amendments and constitutes a technical revision. Notable updates include a revised Clause 530 (normative references and terms), the introduction of Clause 537 - Monitoring, and comprehensive revision of most clauses. The standard is part of the IEC 60364 series governing safe design and installation practices for low-voltage systems.

Key topics and technical requirements

The standard addresses practical requirements and selection criteria for equipment that maintain safety and continuity in LV installations. Key technical topics include:

• Protection against electric shock - devices and methods for automatic disconnection of supply, insulation monitoring, and protective separation (SELV/PELV).
• Overcurrent protection - selection, positioning and coordination of devices for overload and short-circuit protection, including fuses and circuit-breakers.
• Residual current devices (RCDs) and residual current monitoring (RCM) - installation conditions, device selection by application and system type (TN, TT, IT).
• Transient overvoltage protection (SPDs) - selection, location, connection types, and coordination with RCDs.
• Arc-fault detection devices (AFDDs) and protection against thermal effects - addressing fire risk and device placement in sensitive locations.
• Isolation, switching and emergency functions - devices for isolation, switching-off for maintenance, emergency stopping and functional control.
• Monitoring (new Clause 537) - guidance on insulation monitoring devices (IMDs) and residual current monitoring to support continuity and fault detection.
• Selectivity and co-ordination - requirements for selective operation between protective devices to limit outage areas and ensure discrimination.

Practical applications

IEC 60364-5-53 provides actionable guidance for:

• Electrical designers and consulting engineers specifying protective devices, SPDs, AFDDs, RCDs and IMDs.
• Installers and contractors applying correct positioning, wiring and coordination of protection equipment.
• Safety engineers and facility managers enforcing compliance to reduce shock, fire and equipment-damage risks.
• Inspectors, auditors and utilities assessing conformity of LV installations and continuity-of-supply arrangements.

Who uses this standard

Typical users include electrical design offices, building services engineers, installation contractors, equipment manufacturers, testing bodies and regulatory authorities involved in low-voltage installations.

Related standards

This part is one element of the IEC 60364 family (low-voltage electrical installations) and references device-specific standards and normative references consolidated in Clause 530. For complete compliance, consult related parts of IEC 60364 and the referenced device standards.

Standards Content (Sample)

IEC 60364-5-53 ®
Edition 4.0 2019-02
INTERNATIONAL
STANDARD
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Low-voltage electrical installations –
Part 5-53: Selection and erection of electrical equipment – Devices for protection
for safety, isolation, switching, control and monitoring
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IEC 60364-5-53 ®
Edition 4.0 2019-02
INTERNATIONAL
STANDARD
colour
inside
Low-voltage electrical installations –

Part 5-53: Selection and erection of electrical equipment – Devices for

protection for safety, isolation, switching, control and monitoring

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.130.01; 91.140.50 ISBN 978-2-8322-6509-3

– 2 – IEC 60364-5-53:2019  IEC 2019
CONTENTS
FOREWORD . 6
530.1 Scope . 8
530.2 Normative references . 8
530.3 Terms and definitions . 11
530.4 General and common requirements. 14
530.5 Erection of equipment . 14
531 Devices for protection against indirect contact by automatic disconnection of
supply. 14
531.1 Overcurrent protective devices . 14
531.1.1 TN systems . 14
531.1.2 TT systems . 14
531.1.3 IT systems . 15
531.2 Residual current protective devices. 15
531.2.1 General conditions of installation . 15
531.2.2 Selection of devices according to their method of application . 15
531.2.3 TN systems . 15
531.2.4 TT systems . 16
531.2.5 IT systems . 16
531.3 Insulation monitoring devices . 16
532 Devices and precautions for protection against thermal effects . 16
532.1 General . 16
532.2 Locations with a particular risk of fire . 16
532.2.1 General . 16
532.2.2 Locations with external influences BD2, BD3 or BD4 . 17
532.2.3 Locations with external influences BE2 . 17
532.3 Selection of arc fault detection devices (AFDD) . 18
533 Devices for protection against overcurrent . 18
533.1 General requirements . 18
533.1.1 General . 18
533.1.2 Compliance with standards . 18
533.1.3 Fuses . 19
533.2 Selection of devices for protection against overload current . 19
533.2.1 General . 19
533.2.2 Presence of harmonic currents . 20
533.2.3 Unequal current sharing between parallel conductors . 20
533.3 Selection of devices for protection against short-circuit current . 20
533.3.1 Thermal stresses . 20
533.3.2 Breaking capacity . 21
533.4 Positioning of overcurrent protection devices . 21
533.4.1 General . 21
533.4.2 Positioning of devices for overload protection . 21
533.4.3 Positioning of devices for short-circuit protection . 22
533.5 Co-ordination of overload and short-circuit protective functions. 23
533.5.1 Protective functions provided by one device . 23
533.5.2 Protective functions provided by separate devices . 23
534 Devices for protection against transient overvoltages . 23

534.1 General . 23
534.2 Void . 24
534.3 Void . 24
534.4 Selection and erection of SPDs . 24
534.4.1 SPD location and SPD test class . 24
534.4.2 Transient overvoltage protection requirements . 25
534.4.3 Connection types . 25
534.4.4 Selection of SPDs . 27
534.4.5 Protection of the SPD against overcurrent . 31
534.4.6 Fault protection . 33
534.4.7 SPDs installation in conjunction with RCDs. 34
534.4.8 Connections of the SPD . 34
534.4.9 Effective protective distance of SPDs . 36
534.4.10 Connecting conductors of SPDs . 37
535 Co-ordination of protective devices . 37
535.1 Selectivity between overcurrent protective devices . 37
535.1.1 General . 37
535.1.2 Partial selectivity . 38
535.1.3 Full selectivity . 38
535.1.4 Total selectivity . 38
535.1.5 Enhanced selectivity . 38
535.2 Co-ordination between residual current protective devices and OCPDs. 39
535.3 Selectivity between residual current protective devices . 39
535.4 Selectivity of RCD and OCPD . 39
535.5 Combined short-circuit protection of OCPDs . 39
536 Isolation and switching . 40
536.2 Isolation . 40
536.2.1 General . 40
536.2.2 Devices for isolation . 41
536.3 Switching-off for mechanical maintenance . 42
536.3.1 General . 42
536.3.2 Devices for switching-off for mechanical maintenance . 42
536.4 Emergency switching . 43
536.4.1 General . 43
536.4.2 Devices for emergency switching-off . 43
536.4.3 Devices for emergency stopping . 44
536.5 Functional switching (control) . 44
536.5.1 General . 44
536.5.2 Devices for functional switching . 44
537 Monitoring . 45
537.1 General . 45
537.1.1 Monitoring devices . 45
537.1.2 Selection of insulation monitoring devices (IMDs) . 45
537.1.3 Selection of residual current monitoring devices (RCMs) . 45
537.2 IT systems for continuity of supply . 45
537.2.1 General . 45
537.2.2 Insulation monitoring devices (IMDs) . 46
537.2.3 Installation of IMDs . 46
537.3 IT public distribution system . 46

– 4 – IEC 60364-5-53:2019  IEC 2019
537.4 Off-line systems in TN, TT and IT systems . 46
Annex A (informative) Position of devices for overload protection . 48
A.1 General . 48
A.2 Cases where overload protection need not be placed at the origin of the
branch circuit . 48
Annex B (informative) Position of devices for short-circuit protection . 50
B.1 General . 50
B.2 Cases where short-circuit protection need not be placed at the origin of
branch circuit . 50
Annex C (informative) SPD installation – Examples of installation diagrams according
to system configurations . 52
C.1 TT system – 3 phase supply plus neutral . 52
C.2 TN-C and TN-C-S systems – 3 phase supply . 56
C.3 TN-S system – 3 phase supply plus neutral . 60
C.4 IT system – 3 phase supply with or without neutral . 62
Annex D (informative) Installation supplied by overhead lines . 65
Annex E (normative) Reference standards for devices for isolation and switching . 66
Annex F (informative) List of notes concerning certain countries . 68
Bibliography . 75

Figure 1 – Example of installation of class I, class II and class III tested SPDs . 25
Figure 2 – Connection type CT1 (4+0-configuration) for a three-phase system with
neutral . 26
Figure 3 – Connection type CT1 (3+0-configuration) for a three-phase system . 26
Figure 4 – Connection type CT2 (e.g. 3+1-configuration) for a three-phase system with

neutral . 27
Figure 5 – Connection points of an SPD assembly . 31
Figure 6 – Example of overcurrent protection in the SPD branch by using a dedicated
external overcurrent protective device. 32
Figure 7 – Protective device, which is a part of the installation, also used to protect the
SPD . 33
Figure 8 – Connection of the SPD . 35
Figure 9 – Example of installation of an SPD in order to decrease lead length of SPD

supply conductors . 36
Figure 10 – Example of selectivity . 38
Figure 11 – Example of currents and their correlation to selectivity . 39
Figure 12 – Example of combined short-circuit protection of OCPDs . 40
Figure A.1 – Overload protective device (P ) not at the origin of branch circuit (B) . 48
Figure A.2 – Overload protective device (P ) installed within 3 m of the origin of the
branch circuit (B) . 49
Figure B.1 – Limited change of position of short-circuit protective device (P ) on a
branch circuit . 50
Figure B.2 – Short-circuit protective device P installed at a point on the supply side
of the origin of a branch circuit . 51
Figure C.1 – Example of SPDA installation with connexion type CT2 on the supply side
(upstream) of the main RCD in TT system. 52
Figure C.2 – Example of SPD installation with connexion type CT2 on the supply side
(upstream) of the main RCD in TT system. 53

Figure C.3 – Example of SPDA installation on the load side (downstream) of the main
RCD in TT system . 54
Figure C.4 – Example of SPD installation on the load side (downstream) of the RCD in

TT system . 55
Figure C.5 – Example of SPDA installation in TN-C system . 56
Figure C.6 – Example of SPD installation with connexion type CT1 in TN-C system . 57
Figure C.7 – Example of SPD installation in TN-C-S system where the PEN is
separated into PE and N at the origin of the installation (upstream of the SPD) . 58
Figure C.8 – Example of SPDs installation in TN-C-S in different distribution boards . 59
Figure C.9 – Example of SPDA installation in TN-S system . 60
Figure C.10 – Example of SPDs installation in TN-S . 61
Figure C.11 – Example of SPDA installation in IT system with neutral . 62
Figure C.12 – Example of SPD installation in IT system without neutral . 63
Figure C.13 – Example of SPD installation in IT system with neutral . 64
Figure F.1 – Single user . 71
Figure F.2 – Several users . 71
Figure F.3 – Lamp control circuit with switching in the neutral conductor . 73

Table 1 – Required rated impulse voltage of equipment . 28
Table 2 – U of the SPD dependent on supply system configuration . 29
c
Table 3 – Nominal discharge current (I ) in kA depending on supply system and
n
connection type . 30
Table 4 – Selection of impulse discharge current (I ) where the building is protected
imp
against direct lightning strike . 30
Table 5 – Connection of the SPD dependent on supply system . 34
Table D.1 – Selection of impulse discharge current (I ) . 65
imp
Table E.1 – Devices for isolation and switching. 66

– 6 – IEC 60364-5-53:2019  IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LOW-VOLTAGE ELECTRICAL INSTALLATIONS –

Part 5-53: Selection and erection of electrical equipment – Devices for
protection for safety, isolation, switching, control and monitoring

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
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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
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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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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.
International Standard IEC 60364 has been prepared by IEC technical committee 64:
Electrical installations and protection against electric shock.
This fourth edition cancels and replaces the third edition published in 2001,
Amendment 1:2002 and Amendment 2:2015. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) revision of all clauses except 531 and 534;
b) introduction of a new Clause 537 Monitoring;
c) Clause 530 contains all normative references and all terms and definitions.

The text of this International Standard is based on the following documents:
FDIS Report on voting
64/2352/FDIS 64/2359/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The reader's attention is drawn to the fact that Annex F lists all of the “in-some-country”
clauses on differing practices relating to the subject of this standard.
A list of all parts in the IEC 60364 series, published under the general title Low-voltage
electrical installations, 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 "http://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.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication 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.
– 8 – IEC 60364-5-53:2019  IEC 2019
LOW-VOLTAGE ELECTRICAL INSTALLATIONS –

Part 5-53: Selection and erection of electrical equipment – Devices for
protection for safety, isolation, switching, control and monitoring

530.1 Scope
This document provides requirements for:
a) isolation, switching, control and monitoring, and
b) selection and erection of:
1) devices for isolation, switching, control and monitoring, and
2) devices to achieve compliance with measures of protection for safety.
530.2 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 60204-1, Safety of machinery – Electrical equipment of machines – Part 1: General
requirements
IEC 60269-2, Low-voltage fuses – Part 2: Supplementary requirements for fuses for use by
authorized persons (fuses mainly for industrial application) – Examples of standardized
systems of fuses A to K
IEC 60269-3, Low-voltage fuses – Part 3: Supplementary requirements for fuses for use by
unskilled persons (fuses mainly for household and similar applications) – Examples of
standardized systems of fuses A to F
IEC 60269-4, Low-voltage fuses – Part 4: Supplementary requirements for use-links for the
protection of semiconductor devices
IEC 60309 (all parts), Plugs, socket-outlets and couplers for industrial purposes
IEC 60364 (all parts), Low-voltage electrical installations
IEC 60364-4-41:2005, Low-voltage electrical installations – Part 4-41: Protection for safety –
Protection against electric shock
IEC 60364-4-41:2005/AMD1:2017
IEC 60364-4-42:2010, Low-voltage electrical installations – Part 4-42: Protection for safety –
Protection against thermal effects
IEC 60364-4-42:2010/AMD1:2014
IEC 60364-4-43:2008, Low-voltage electrical installations – Part 4-43: Protection for safety –
Protection against overcurrent
IEC 60364-4-44:2007, Low-voltage electrical installations – Part 4-44: Protection for safety –
Protection against voltage disturbances and electromagnetic disturbances
IEC 60364-4-44:2007/AMD1:2015
IEC 60364-5-55, Electrical installations of buildings – Part 5-55: Selection and erection of
electrical equipment – Other equipment
IEC 60364-6:2016, Low voltage electrical installations– Part 6: Verification
IEC 60417 (all parts), Graphical symbols for use on equipment
IEC 60664-1:2007, Insulation coordination for equipment within low-voltage systems –
Part 1: Principles, requirements and tests
IEC 60669-1, Switches for household and similar fixed-electrical installations –
Part 1: General requirements
IEC 60669-2-1, Switches for household and similar fixed electrical installations –
Part 2-1: Particular requirements – Electronic switches
IEC 60669-2-2, Switches for household and similar fixed electrical installations –
Part 2-2: Particular requirements – Electromagnetic remote-control switches (RCS)
IEC 60669-2-3, Switches for household and similar fixed electrical installations –
Part 2-3: Particular requirements – Time-delay switches (TDS)
IEC 60669-2-4, Switches for household and similar fixed electrical installations –
Part 2-4: Particular requirements – Isolating switches
IEC 60669-2-5, Switches for household and similar fixed electrical installations –
Part 2-5: Particular requirements – Switches and related accessories for use in home and
building electronic systems (HBES)
IEC 60669-2-6, Switches for household and similar fixed electrical installations –
Part 2-6: Particular requirements – Fireman's switches for exterior and interior signs and
luminaires
IEC 60670-24, Boxes and enclosures for electrical accessories for household and similar fixed
electrical installations – Part 24: Particular requirements for enclosures for housing protective
devices and other power dissipating electrical equipment
IEC 60884 (all parts), Plugs and socket-outlets for household and similar purposes
IEC 60898 (all parts), Electrical accessories – Circuit-breakers for overcurrent protection for
household and similar installations
IEC 60906 (all parts), IEC system of plugs and socket-outlets for household and similar
purposes
IEC 60947-2:2016, Low-voltage switchgear and controlgear – Part 2: Circuit-breakers
IEC 60947-3, Low-voltage switchgear and controlgear – Part 3: Switches, disconnectors,
switch-disconnectors and fuse-combination units
IEC 60947-4-1, Low-voltage switchgear and controlgear – Part 4-1: Contactors and motor-
starters – Electromechanical contactors and motor-starters
-
IEC 60947-4-2, Low-voltage switchgear and controlgear – Part 4-2: Contactors and motor
starters – AC semiconductor motor controllers and starters

– 10 – IEC 60364-5-53:2019  IEC 2019
IEC 60947-4-3, Low-voltage switchgear and controlgear – Part 4-3: Contactors and motor-
starters – AC semiconductor controllers and contactors for non-motor loads
IEC 60947-5-1, Low-voltage switchgear and controlgear – Part 5-1: Control circuit devices
and switching elements – Electromechanical control circuit devices
IEC 60947-6-1, Low-voltage switchgear and controlgear – Part 6-1: Multiple function
equipment – Transfer switching equipment
IEC 60947-6-2, Low-voltage switchgear and controlgear – Part 6-2: Multiple function
equipment – Control and protective switching devices (or equipment) (CPS)
IEC 61008 (all parts), Residual current operated circuit-breakers without integral overcurrent
protection for household and similar uses (RCCBs)
IEC 61009 (all parts), Residual current operated circuit-breakers with integral overcurrent
protection for household and similar uses (RCBOs)
IEC 61095, Electromechanical contactors for household and similar purposes
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 61439-6, Low-voltage switchgear and controlgear assemblies – Part 6: Busbar trunking
systems (busways)
IEC 61534 (all parts), Powertrack systems
IEC 61557-8, Electrical safety in low voltage distribution systems up to 1 000 V a.c. and
1 500 V d.c. – Equipment for testing, measuring or monitoring of protective measures –
Part 8: Insulation monitoring devices for IT systems
IEC 61557-9, Electrical safety in low voltage distribution systems up to 1 000 V a.c. and
1 500 V d.c. – Equipment for testing, measuring or monitoring of protective measures –
Part 9: Equipment for insulation fault location in IT systems
IEC 61643-11, Low-voltage surge protective devices – Part 11: Surge protective devices
connected to low-voltage power systems – Requirements and test methods
IEC 61643-12, Low-voltage surge protective devices – Part 12: Surge protective devices
connected to low-voltage power distribution systems – Selection and application principles
IEC 61984:2008, Connectors – Safety requirements and tests
IEC 61995 (all parts), Devices for the connection of luminaires for household and similar
purposes
IEC 62020, Electrical accessories – Residual current monitors for household and similar uses
(RCMs)
IEC 62208, Empty enclosures for low-voltage switchgear and controlgear assemblies –
General requirements
IEC 62305 (all parts), Protection against lightning
IEC 62423, Type F and type B residual current operated circuit-breakers with and without
integral overcurrent protection for household and similar uses
IEC 62606, General requirements for arc fault detection devices
IEC 62626-1, Low-voltage switchgear and controlgear enclosed equipment – Part 1: Enclosed
switch-disconnectors outside the scope of IEC 60947-3 to provide isolation during repair and
maintenance work
530.3 Terms and definitions
For the purposes of this document, the following terms and definitions 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.
530.3.1
disconnector
mechanical switching device which in the open position complies with the requirements
specified for the isolating function
Note 1 to entry: A disconnector is capable of opening and closing a circuit when either negligible current is
broken or made, or when no significant change in the voltage across the terminals of each of the poles of the
disconnector occurs. It is also capable of carrying currents under normal circuit conditions and carrying for a
specified time currents under abnormal conditions such as those of short-circuit.
[SOURCE: IEC 60050-441:2000, 441-14-05, modified – Referring to isolating function instead
of isolating distance.]
530.3.2
switch disconnector
switch which, in the open position, satisfies the isolating requirements specified for a
disconnector
[SOURCE: IEC 60050-441:1984, 441-14-12]
530.3.3
mechanical switch
device capable of making, carrying and breaking currents through contacts controlled by
mechanical operation under normal circuit conditions which may include specified operating
overload conditions and also carrying for specified time currents under specified abnormal
circuit conditions such as those of short-circuit
Note 1 to entry: A switch can be capable of making but not breaking short-circuit currents.
[SOURCE: IEC 60050-441:2000, 441-14-10, modified – "through contacts controlled by
mechanical operation" has been added.]
530.3.4
switching-off for mechanical maintenance
opening operation of a switching device intended to inactivate an item or items of electrically
powered equipment for the purpose of preventing a hazard, other than due to electric shock or
to arcing, during non-electrical work on the equipment

– 12 – IEC 60364-5-53:2019  IEC 2019
[SOURCE: IEC 60050-826:2004, 826-17-02]
530.3.5
emergency switching-off
opening operation of a switching device intended to remove electric power from an electrical
installation to avert or alleviate a hazardous situation
[SOURCE: IEC 60050-826:2004, 826-17-03]
530.3.6
emergency stopping
operation intended to stop as quickly as possible a movement which has become dangerous
[SOURCE: IEC 60050-826:2004, 826-17-04]
530.3.7
functional switching
operation intended to switch on or off or vary the supply of electric energy to an electrical
installation or parts of it for normal operating purposes
[SOURCE: IEC 60050-826:2004, 826-17-05]
530.3.8
SPD assembly
one SPD or a set of SPDs, in both cases including all SPD disconnectors required by the SPD
manufacturer, providing the required overvoltage protection for a type of system earthing
530.3.9
SPD disconnector
disconnector
device for disconnecting an SPD, or part of an SPD, from the power system
Note 1 to entry: This disconnecting device is not required to have isolating capability for safety purposes. It is to
prevent a persistent fault on the system and is used to give an indication of an SPD’s failure. Disconnectors can be
internal (built in) or external (required by the manufacturer). There may be more than one disconnector function, for
example an overcurrent protection function and a thermal protection function. These functions may be in separate
units.
[SOURCE: IEC 61643-11:2011, 3.1.28]
530.3.10
mode of protection of an SPD
intended current path, between terminals that contains protective components, e.g. line-to-
line, line-to-earth, line-to-neutral, neutral-to-earth
[SOURCE: IEC 61643-11:2011, 3.1.8]
530.3.11
follow current interrupt rating
I
fi
prospective short-circuit current that an SPD is able to interrupt without operation of a
disconnector
[SOURCE: IEC 61643-11:2011, 3.1.39]

530.3.12
short-circuit current rating
I
SCCR
maximum prospective short-circuit current from the power system for which the SPD, in
conjunction with the disconnector specified, is rated
[SOURCE: IEC 61643-11:2011, 3.1.27]
530.3.13
voltage protection level
U
P
maximum voltage to be expected at the SPD terminals due to an impulse stress with defined
voltage steepness and an impulse stress with a discharge current with given amplitude and
waveshape
Note 1 to entry: The voltage protection level is given by the manufacturer and may not be exceeded by:
• the measured limiting voltage determined for front-of-wave sparkover (if applicable) and the measured limiting
voltage determined from the residual voltage measurements at amplitudes corresponding to I and/or I
n imp
respectively for test classes II and/or I;
• the measured limiting voltage at the open circuit voltage of the combination wave generator (U ), determined
OC
for the combination wave for test class III.
[SOURCE: IEC 61643-11:2011, 3.1.14]
530.3.14
rated impulse voltage
U
W
impulse withstand voltage value assigned by the manufacturer to the equipment or to a part of
it, characterizing the specified withstand capability of its insulation against transient
overvoltages
[SOURCE: IEC 60664-1:2007, 3.9.2]
530.3.15
maximum continuous operating voltage
U
C
maximum RMS voltage, which may be continuously applied to the SPD's mode of protection
Note 1 to entry: The U value covered by this document may exceed 1 000 V.
C
[SOURCE: IEC 61643-11:2011, 3.1.11]
530.3.16
nominal discharge current for class II test
I
n
crest value of the current through the SPD having a current waveshape of 8/20 μs
[SOURCE: IEC 61643-11:2011, 3.1.9]
530.3.17
impulse discharge current for class I test
I
imp
crest value of a discharge current through the SPD with specified charge transfer Q and
specified energy W/R in the specified time
[SOURCE: IEC 61643-11:2011, 3.1.10]

– 14 – IEC 60364-5-53:2019  IEC 2019
530.3.18
two-port SPD
SPD having specific series impedance connected between separate input and output
connections
[SOURCE: IEC 61643-11:2011, 3.1.3]
530.4 General and common requirements
530.4.1
Equipment for protection, isolation, switching, control and monitoring shall be selected and
erected to provide for the safety and proper functioning for the intended use of the
installation.
Such equipment shall be selected and erected so as to allow compliance with the
requirements stated in this document and the relevant requirements in other parts of
IEC 60364.
530.4.2
Except as provided in 536.2.2.7 and 536.5.1.2, an independently operated single-pole
protective or switching device shall not be inserted in the neutral conductor.
530.4.3
Devices providing more than one function shall comply with all the requirements of this
document appropriate to each separate function.
530.5 Erection of equipment
530.5.1
Equipment shall be erected in such a way that connections between wiring and equipment
shall not be subject to undue stress or strain resulting from the foreseen use of the
equipment.
530.5.2
Unenclosed type equipment shall be mounted in a suitable mounting box or enclosure in
compliance with a relevant standard.
NOTE Examples of relevant standards are IEC 60670 (all parts), IEC 62208, IEC 61439 (all parts), and
IEC 61084 (all parts).
531 Devices for protection against indirect contact by automatic disconnection
of supply
531.1 Overcurrent protective devices
531.1.1 TN systems
In TN systems overcurrent protective devices shall be selected and erected according
...

IEC 60364-5-53 ®
Edition 4.2 2024-12
CONSOLIDATED VERSION
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Low-voltage electrical installations –
Part 5-53: Selection and erection of electrical equipment – Devices for protection
for safety, isolation, switching, control and monitoring

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IEC 60364-5-53 ®
Edition 4.2 2024-12
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
colour
inside
Low-voltage electrical installations –
Part 5-53: Selection and erection of electrical equipment – Devices for protection
for safety, isolation, switching, control and monitoring
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.130.01, 91.140.50 ISBN 978-2-8327-0119-5
REDLINE VERSION – 2 – IEC 60364-5-53:2019+AMD1:2020
+AMD2:2024 CSV © IEC 2024
CONTENTS
FOREWORD . 7
530.1 Scope . 9
530.2 Normative references . 9
530.3 Terms and definitions . 12
530.4 General and common requirements. 15
530.5 Erection of equipment . 15
531 Devices for protection against indirect contact by automatic disconnection of
supply.
531.1 Overcurrent protective devices .
531.1.1 TN systems .
531.1.2 TT systems .
531.1.3 IT systems .
531.2 Residual current protective devices.
531.2.1 General conditions of installation .
531.2.2 Selection of devices according to their method of application .
531.2.3 TN systems .
531.2.4 TT systems .
531.2.5 IT systems .
531.3 Insulation monitoring devices .
531 Equipment for protection against electric shock . 17
531.1 General . 17
531.2 Devices for automatic disconnection of supply . 18
531.2.1 General . 18
531.2.2 Overcurrent protective devices . 18
531.2.3 Residual current protective devices . 20
531.3 Equipment for protection by double or reinforced insulation . 23
531.3.1 General . 23
531.4 Equipment for protection by electrical separation . 25
531.5 Equipment for protection by extra-low-voltage provided by SELV and PELV
systems . 25
531.5.1 Sources for SELV or PELV systems . 25
531.5.2 Selection of plugs and socket-outlets . 25
531.6 Devices for additional protection . 25
531.7 Monitoring devices . 26
532 Devices and precautions for protection against thermal effects . 26
532.1 General . 26
532.2 Locations with a particular risk of fire . 26
532.2.1 General . 26
532.2.2 Locations with external influences BD2, BD3 or BD4 . 26
532.2.3 Locations with external influences BE2 . 27
532.2.3.1 General . 27
532.2.3.2 Selection of residual current protective devices (RCD) . 27
532.2.3.3 Selection of residual current monitoring device (RCM) in IT systems . 27
532.2.3.4 Selection of insulation monitoring devices (IMDs) in IT systems . 27
532.3 Selection of arc fault detection devices (AFDD) . 27
533 Devices for protection against overcurrent . 28
533.1 General requirements . 28

+AMD2:2024 CSV © IEC 2024
533.1.1 General . 28
533.1.2 Compliance with standards . 28
533.1.2.1 General . 28
533.1.2.2 Applicability of devices . 28
533.1.3 Fuses . 29
533.2 Selection of devices for protection against overload current . 29
533.2.1 General . 29
533.2.2 Presence of harmonic currents . 30
533.2.3 Unequal current sharing between parallel conductors . 30
533.3 Selection of devices for protection against short-circuit current . 30
533.3.1 Thermal stresses . 30
533.3.1.1 Cables and insulated conductors . 30
533.3.1.2 Busbar trunking systems and powertracks . 30
533.3.2 Breaking capacity . 31
533.4 Positioning of overcurrent protection devices . 31
533.4.1 General . 31
533.4.2 Positioning of devices for overload protection . 31
533.4.3 Positioning of devices for short-circuit protection . 32
533.5 Co-ordination of overload and short-circuit protective functions. 33
533.5.1 Protective functions provided by one device . 33
533.5.2 Protective functions provided by separate devices . 33
534 Devices for protection against transient overvoltages . 33
534.1 General . 33
534.2 Void . 34
534.3 Void . 34
534.4 Selection and erection of SPDs . 34
534.4.1 SPD location and SPD test class . 34
534.4.2 Transient overvoltage protection requirements . 35
534.4.3 Connection types . 35
534.4.4 Selection of SPDs . 37
534.4.5 Protection of the SPD against overcurrent . 42
534.4.6 Fault protection . 44
534.4.7 SPDs installation in conjunction with RCDs. 45
534.4.8 Connections of the SPD . 45
534.4.9 Effective protective distance of SPDs . 47
534.4.10 Connecting conductors of SPDs . 48
535 Co-ordination of protective devices . 48
535.1 Selectivity between overcurrent protective devices . 48
535.1.1 General . 48
535.1.2 Partial selectivity . 49
535.1.3 Full selectivity . 49
535.1.4 Total selectivity . 49
535.1.5 Enhanced selectivity . 49
535.2 Co-ordination between residual current protective devices and OCPDs. 50
535.3 Selectivity between residual current protective devices . 50
535.4 Selectivity of RCD and OCPD . 50
535.5 Combined short-circuit protection of OCPDs . 50
536 Isolation and switching . 51
536.2 Isolation . 51

REDLINE VERSION – 4 – IEC 60364-5-53:2019+AMD1:2020
+AMD2:2024 CSV © IEC 2024
536.2.1 General . 51
536.2.2 Devices for isolation . 52
536.3 Switching-off for mechanical maintenance . 53
536.3.1 General . 53
536.3.2 Devices for switching-off for mechanical maintenance . 53
536.4 Emergency switching . 54
536.4.1 General . 54
536.4.2 Devices for emergency switching-off . 54
536.4.3 Devices for emergency stopping . 55
536.5 Functional switching (control) . 55
536.5.1 General . 55
536.5.2 Devices for functional switching . 55
537 Monitoring . 56
537.1 General . 56
537.1.1 Monitoring devices . 56
537.1.2 Selection of insulation monitoring devices (IMDs) . 56
537.1.3 Selection of residual current monitoring devices (RCMs) . 56
537.2 IT systems for continuity of supply . 56
537.2.1 General . 56
537.2.2 Insulation monitoring devices (IMDs) . 57
537.2.3 Installation of IMDs . 57
537.3 IT public distribution system . 57
537.4 Off-line systems in TN, TT and IT systems . 57
Annex A (informative) Position of devices for overload protection . 59
A.1 General . 59
A.2 Cases where overload protection need not be placed at the origin of the
branch circuit . 59
Annex B (informative) Position of devices for short-circuit protection . 61
B.1 General . 61
B.2 Cases where short-circuit protection need not be placed at the origin of
branch circuit . 61
Annex C (informative) SPD installation – Examples of installation diagrams according
to system configurations . 63
C.1 TT system – 3 phase supply plus neutral . 63
C.2 TN-C and TN-C-S systems – 3 phase supply . 67
C.3 TN-S system – 3 phase supply plus neutral . 71
C.4 IT system – 3 phase supply with or without neutral . 73
Annex D (informative) Installation supplied by overhead lines . 76
Annex E (normative) Reference standards for devices for isolation and switching . 77
Annex F (informative) List of notes concerning certain countries . 79
Annex G (informative) Description of the different types of residual current devices
(RCDs) . 88
G.1 Description of RCD types . 88
G.2 Examples of use of RCD types . 89
Annex H (informative) Additional information for the application of DC SPDs . 92
H.1 General . 92
H.2 Parameters for the selection of SPDs in DC applications . 92
Bibliography . 93

+AMD2:2024 CSV © IEC 2024
Figure 1 – Example of installation of class I, class II and class III tested SPDs . 35
Figure 2 – Connection type CT1 (4+0-configuration) for a three-phase system with
neutral . 36
Figure 3 – Connection type CT1 (3+0-configuration) for a three-phase system . 36
Figure 4 – Connection type CT2 (e.g. 3+1-configuration) for a three-phase system with
neutral . 37
Figure 5 – Connection points of an SPD assembly . 42
Figure 6 – Example of overcurrent protection in the SPD branch by using a dedicated
external overcurrent protective device. 43
Figure 7 – Protective device, which is a part of the installation, also used to
protect the SPD . 44
Figure 8 – Connection of the SPD . 46
Figure 9 – Example of installation of an SPD in order to decrease lead length of SPD
supply conductors . 47
Figure 10 – Example of selectivity . 49
Figure 11 – Example of currents and their correlation to selectivity . 50
Figure 12 – Example of combined short-circuit protection of OCPDs . 51
Figure A.1 – Overload protective device (P ) not at the origin of branch circuit (B) . 59
Figure A.2 – Overload protective device (P ) installed within 3 m of the origin of the
branch circuit (B) . 60
Figure B.1 – Limited change of position of short-circuit protective device (P ) on a
branch circuit . 61
Figure B.2 – Short-circuit protective device P installed at a point on the supply side
of the origin of a branch circuit . 62
Figure C.1 – Example of SPDA installation with connexion type CT2 on the supply side
(upstream) of the main RCD in TT system. 63
Figure C.2 – Example of SPD installation with connexion type CT2 on the supply side
(upstream) of the main RCD in TT system. 64
Figure C.3 – Example of SPDA installation on the load side (downstream) of the main
RCD in TT system . 65
Figure C.4 – Example of SPD installation on the load side (downstream) of the RCD in
TT system . 66
Figure C.5 – Example of SPDA installation in TN-C system . 67
Figure C.6 – Example of SPD installation with connexion type CT1 in TN-C system . 68
Figure C.7 – Example of SPD installation in TN-C-S system where the PEN is
separated into PE and N at the origin of the installation (upstream of the SPD) . 69
Figure C.8 – Example of SPDs installation in TN-C-S in different distribution boards . 70
Figure C.9 – Example of SPDA installation in TN-S system . 71
Figure C.10 – Example of SPDs installation in TN-S . 72
Figure C.11 – Example of SPDA installation in IT system with neutral . 73
Figure C.12 – Example of SPD installation in IT system without neutral . 74
Figure C.13 – Example of SPD installation in IT system with neutral . 75
Figure F.1 – Single user . 84
Figure F.2 – Several users . 84
Figure F.3 – Lamp control circuit with switching in the neutral conductor . 86
Figure G.1 – Possible earth fault currents in systems with semiconductors . 91

REDLINE VERSION – 6 – IEC 60364-5-53:2019+AMD1:2020
+AMD2:2024 CSV © IEC 2024
Table 1 – Required rated impulse voltage of equipment .
Table 2 – U of the SPD dependent on supply system configuration . 40
c
Table 3 – Nominal discharge current (I ) in kA depending on supply system and
n
connection type . 41
Table 4 – Selection of impulse discharge current (I ) where the building is protected
imp
against direct lightning strike . 41
Table 5 – Connection of the SPD dependent on supply system . 45
Table D.1 – Selection of impulse discharge current (I ) . 76
imp
Table E.1 – Devices for isolation and switching. 77

+AMD2:2024 CSV © IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LOW-VOLTAGE ELECTRICAL INSTALLATIONS –

Part 5-53: Selection and erection of electrical equipment – Devices for
protection for safety, isolation, switching, control and monitoring

FOREWORD
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This consolidated version of the official IEC Standard and its amendments has been
prepared for user convenience.
IEC 60364-5-53 edition 4.2 contains the fourth edition (2019-02) [documents
64/2352/FDIS and 64/2359/RVD], its amendment 1 (2020-12) [documents 64/2457/FDIS
and 64/2465/RVD] and its amendment 2 (2024-12) [documents 64/2648/FDIS and
64/2738/RVD].
In this Redline version, a vertical line in the margin shows where the technical content
is modified by amendments 1 and 2. Additions are in green text, deletions are in
strikethrough red text. A separate Final version with all changes accepted is available
in this publication.
REDLINE VERSION – 8 – IEC 60364-5-53:2019+AMD1:2020
+AMD2:2024 CSV © IEC 2024
International Standard IEC 60364 has been prepared by IEC technical committee 64:
Electrical installations and protection against electric shock.
This fourth edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) revision of all clauses except 531 and 534;
b) introduction of a new Clause 537 Monitoring;
c) Clause 530 contains all normative references and all terms and definitions.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The reader's attention is drawn to the fact that Annex F lists all of the “in-some-country”
clauses on differing practices relating to the subject of this standard.
A list of all parts in the IEC 60364 series, published under the general title Low-voltage
electrical installations, can be found on the IEC website.
The committee has decided that the contents of this document and its amendments 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 publication 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.
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LOW-VOLTAGE ELECTRICAL INSTALLATIONS –

Part 5-53: Selection and erection of electrical equipment – Devices for
protection for safety, isolation, switching, control and monitoring

530.1 Scope
This document provides requirements for:
a) isolation, switching, control and monitoring, and
b) selection and erection of:
1) devices for isolation, switching, control and monitoring, and
2) devices to achieve compliance with measures of protection for safety.
530.2 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 60204-1, Safety of machinery – Electrical equipment of machines – Part 1: General
requirements
IEC 60269-2, Low-voltage fuses – Part 2: Supplementary requirements for fuses for use by
authorized persons (fuses mainly for industrial application) – Examples of standardized
systems of fuses A to K
IEC 60269-3, Low-voltage fuses – Part 3: Supplementary requirements for fuses for use by
unskilled persons (fuses mainly for household and similar applications) – Examples of
standardized systems of fuses A to F
IEC 60269-4, Low-voltage fuses – Part 4: Supplementary requirements for use-links for the
protection of semiconductor devices
IEC 60309 (all parts), Plugs, socket-outlets and couplers for industrial purposes
IEC 60364 (all parts), Low-voltage electrical installations
IEC 60364-4-41:2005, Low-voltage electrical installations – Part 4-41: Protection for safety –
Protection against electric shock
IEC 60364-4-41:2005/AMD1:2017
IEC 60364-4-42:2010, Low-voltage electrical installations – Part 4-42: Protection for safety –
Protection against thermal effects
IEC 60364-4-42:2010/AMD1:2014
IEC 60364-4-43:2008, Low-voltage electrical installations – Part 4-43: Protection for safety –
Protection against overcurrent
IEC 60364-4-44:2007, Low-voltage electrical installations – Part 4-44: Protection for safety –
Protection against voltage disturbances and electromagnetic disturbances
IEC 60364-4-44:2007/AMD1:2015
REDLINE VERSION – 10 – IEC 60364-5-53:2019+AMD1:2020
+AMD2:2024 CSV © IEC 2024
IEC 60364-5-55, Electrical installations of buildings – Part 5-55: Selection and erection of
electrical equipment – Other equipment
IEC 60364-6:2016, Low voltage electrical installations– Part 6: Verification
IEC 60417 (all parts), Graphical symbols for use on equipment
IEC 60664-1:2007, Insulation coordination for equipment within low-voltage systems –
Part 1: Principles, requirements and tests
IEC 60669-1, Switches for household and similar fixed-electrical installations –
Part 1: General requirements
IEC 60669-2-1, Switches for household and similar fixed electrical installations –
Part 2-1: Particular requirements – Electronic switches
IEC 60669-2-2, Switches for household and similar fixed electrical installations –
Part 2-2: Particular requirements – Electromagnetic remote-control switches (RCS)
IEC 60669-2-3, Switches for household and similar fixed electrical installations –
Part 2-3: Particular requirements – Time-delay switches (TDS)
IEC 60669-2-4, Switches for household and similar fixed electrical installations –
Part 2-4: Particular requirements – Isolating switches
IEC 60669-2-5, Switches for household and similar fixed electrical installations –
Part 2-5: Particular requirements – Switches and related accessories for use in home and
building electronic systems (HBES)
IEC 60669-2-6, Switches for household and similar fixed electrical installations –
Part 2-6: Particular requirements – Fireman's switches for exterior and interior signs and
luminaires
IEC 60670-24, Boxes and enclosures for electrical accessories for household and similar fixed
electrical installations – Part 24: Particular requirements for enclosures for housing protective
devices and other power dissipating electrical equipment
IEC 60884 (all parts), Plugs and socket-outlets for household and similar purposes
IEC 60898 (all parts), Electrical accessories – Circuit-breakers for overcurrent protection for
household and similar installations
IEC 60906 (all parts), IEC system of plugs and socket-outlets for household and similar
purposes
IEC 60947-2:2016, Low-voltage switchgear and controlgear – Part 2: Circuit-breakers
IEC 60947-3, Low-voltage switchgear and controlgear – Part 3: Switches, disconnectors,
switch-disconnectors and fuse-combination units
IEC 60947-4-1, Low-voltage switchgear and controlgear – Part 4-1: Contactors and motor-
starters – Electromechanical contactors and motor-starters
IEC 60947-4-2, Low-voltage switchgear and controlgear – Part 4-2: Contactors and motor-
starters – AC semiconductor motor controllers and starters

+AMD2:2024 CSV © IEC 2024
IEC 60947-4-3, Low-voltage switchgear and controlgear – Part 4-3: Contactors and motor-
starters – AC semiconductor controllers and contactors for non-motor loads
IEC 60947-5-1, Low-voltage switchgear and controlgear – Part 5-1: Control circuit devices
and switching elements – Electromechanical control circuit devices
IEC 60947-6-1, Low-voltage switchgear and controlgear – Part 6-1: Multiple function
equipment – Transfer switching equipment
IEC 60947-6-2, Low-voltage switchgear and controlgear – Part 6-2: Multiple function
equipment – Control and protective switching devices (or equipment) (CPS)
IEC 61008 (all parts), Residual current operated circuit-breakers without integral overcurrent
protection for household and similar uses (RCCBs)
IEC 61009 (all parts), Residual current operated circuit-breakers with integral overcurrent
protection for household and similar uses (RCBOs)
IEC 61095, Electromechanical contactors for household and similar purposes
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 61439-6, Low-voltage switchgear and controlgear assemblies – Part 6: Busbar trunking
systems (busways)
IEC 61534 (all parts), Powertrack systems
IEC 61557-8, Electrical safety in low voltage distribution systems up to 1 000 V a.c. and
1 500 V d.c. – Equipment for testing, measuring or monitoring of protective measures –
Part 8: Insulation monitoring devices for IT systems
IEC 61557-9, Electrical safety in low voltage distribution systems up to 1 000 V a.c. and
1 500 V d.c. – Equipment for testing, measuring or monitoring of protective measures –
Part 9: Equipment for insulation fault location in IT systems
IEC 61643-11, Low-voltage surge protective devices – Part 11: Surge protective devices
connected to low-voltage power systems – Requirements and test methods
IEC 61643-12, Low-voltage surge protective devices – Part 12: Surge protective devices
connected to low-voltage power distribution systems – Selection and application principles
IEC 61984:2008, Connectors – Safety requirements and tests
IEC 61995 (all parts), Devices for the connection of luminaires for household and similar
purposes
IEC 62020, Electrical accessories – Residual current monitors for household and similar uses
(RCMs)
IEC 62208, Empty enclosures for low-voltage switchgear and controlgear assemblies –
General requirements
REDLINE VERSION – 12 – IEC 60364-5-53:2019+AMD1:2020
+AMD2:2024 CSV © IEC 2024
IEC 62305 (all parts), Protection against lightning
IEC 62423, Type F and type B residual current operated circuit-breakers with and without
integral overcurrent protection for household and similar uses
IEC 62606, General requirements for arc fault detection devices
IEC 62626-1, Low-voltage switchgear and controlgear enclosed equipment – Part 1: Enclosed
switch-disconnectors outside the scope of IEC 60947-3 to provide isolation during repair and
maintenance work
530.3 Terms and definitions
For the purposes of this document, the following terms and definitions 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.
530.3.1
disconnector
mechanical switching device which in the open position complies with the requirements
specified for the isolating function
Note 1 to entry: A disconnector is capable of opening and closing a circuit when either negligible current is
broken or made, or when no significant change in the voltage across the terminals of each of the poles of the
disconnector occurs. It is also capable of carrying currents under normal circuit conditions and carrying for a
specified time currents under abnormal conditions such as those of short-circuit.
[SOURCE: IEC 60050-441:2000, 441-14-05, modified – Referring to isolating function instead
of isolating distance.]
530.3.2
switch disconnector
switch which, in the open position, satisfies the isolating requirements specified for a
disconnector
[SOURCE: IEC 60050-441:1984, 441-14-12]
530.3.3
mechanical switch
device capable of making, carrying and breaking currents through contacts controlled by
mechanical operation under normal circuit conditions which may include specified operating
overload conditions and also carrying for specified time currents under specified abnormal
circuit conditions such as those of short-circuit
Note 1 to entry: A switch can be capable of making but not breaking short-circuit currents.
[SOURCE: IEC 60050-441:2000, 441-14-10, modified – "through contacts controlled by
mechanical operation" has been added.]
530.3.4
switching-off for mechanical maintenance
opening operation of a switching device intended to inactivate an item or items of electrically
powered equipment for the purpose of preventing a hazard, other than due to electric shock or
to arcing, during non-electrical work on the equipment

+AMD2:2024 CSV © IEC 2024
[SOURCE: IEC 60050-826:2004, 826-17-02]
530.3.5
emergency switching-off
opening operation of a switching device intended to remove electric power from an electrical
installation to avert or alleviate a hazardous situation
[SOURCE: IEC 60050-826:2004, 826-17-03]
530.3.6
emergency stopping
operation intended to stop as quickly as possible a movement which has become dangerous
[SOURCE: IEC 60050-826:2004, 826-17-04]
530.3.7
functional switching
operation intended to switch on or off or vary the supply of electric energy to an electrical
installation or parts of it for normal operating purposes
[SOURCE: IEC 60050-826:2004, 826-17-05]
530.3.8
SPD assembly
one SPD or a set of SPDs, in both cases including all SPD disconnectors required by the SPD
manufacturer, providing the required overvoltage protection for a type of system earthing
530.3.9
SPD disconnector
disconnector
device for disconnecting an SPD, or part of an SPD, from the power system
Note 1 to entry: This disconnecting dev
...

IEC 60364-5-53 ®
Edition 4.0 2019-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Low-voltage electrical installations –
Part 5-53: Selection and erection of electrical equipment – Devices
for protection for safety, isolation, switching, control and monitoring

Installations électriques à basse tension –
Partie 5-53: Choix et mise en œuvre des matériels électriques – Dispositifs
de protection pour assurer la sécurité, le sectionnement, la coupure,
la commande et la surveillance

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IEC 60364-5-53 ®
Edition 4.0 2019-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Low-voltage electrical installations –

Part 5-53: Selection and erection of electrical equipment – Devices

for protection for safety, isolation, switching, control and monitoring

Installations électriques à basse tension –

Partie 5-53: Choix et mise en œuvre des matériels électriques – Dispositifs

de protection pour assurer la sécurité, le sectionnement, la coupure,

la commande et la surveillance

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.130.01; 91.140.50 ISBN 978-2-8322-7598-6

– 2 – IEC 60364-5-53:2019 © IEC 2019
CONTENTS
FOREWORD . 6
530.1 Scope . 8
530.2 Normative references . 8
530.3 Terms and definitions . 11
530.4 General and common requirements. 14
530.5 Erection of equipment . 14
531 Devices for protection against indirect contact by automatic disconnection of
supply. 14
531.1 Overcurrent protective devices . 14
531.1.1 TN systems . 14
531.1.2 TT systems . 14
531.1.3 IT systems . 15
531.2 Residual current protective devices. 15
531.2.1 General conditions of installation . 15
531.2.2 Selection of devices according to their method of application . 15
531.2.3 TN systems . 15
531.2.4 TT systems . 16
531.2.5 IT systems . 16
531.3 Insulation monitoring devices . 16
532 Devices and precautions for protection against thermal effects . 16
532.1 General . 16
532.2 Locations with a particular risk of fire . 16
532.2.1 General . 16
532.2.2 Locations with external influences BD2, BD3 or BD4 . 17
532.2.3 Locations with external influences BE2 . 17
532.3 Selection of arc fault detection devices (AFDD) . 18
533 Devices for protection against overcurrent . 18
533.1 General requirements . 18
533.1.1 General . 18
533.1.2 Compliance with standards . 18
533.1.3 Fuses . 19
533.2 Selection of devices for protection against overload current . 19
533.2.1 General . 19
533.2.2 Presence of harmonic currents . 20
533.2.3 Unequal current sharing between parallel conductors . 20
533.3 Selection of devices for protection against short-circuit current . 20
533.3.1 Thermal stresses . 20
533.3.2 Breaking capacity . 21
533.4 Positioning of overcurrent protection devices . 21
533.4.1 General . 21
533.4.2 Positioning of devices for overload protection . 21
533.4.3 Positioning of devices for short-circuit protection . 22
533.5 Co-ordination of overload and short-circuit protective functions. 23
533.5.1 Protective functions provided by one device . 23
533.5.2 Protective functions provided by separate devices . 23
534 Devices for protection against transient overvoltages . 23

534.1 General . 23
534.2 Void . 24
534.3 Void . 24
534.4 Selection and erection of SPDs . 24
534.4.1 SPD location and SPD test class . 24
534.4.2 Transient overvoltage protection requirements . 25
534.4.3 Connection types . 25
534.4.4 Selection of SPDs . 27
534.4.5 Protection of the SPD against overcurrent . 31
534.4.6 Fault protection . 33
534.4.7 SPDs installation in conjunction with RCDs. 34
534.4.8 Connections of the SPD . 34
534.4.9 Effective protective distance of SPDs . 36
534.4.10 Connecting conductors of SPDs . 37
535 Co-ordination of protective devices . 37
535.1 Selectivity between overcurrent protective devices . 37
535.1.1 General . 37
535.1.2 Partial selectivity . 38
535.1.3 Full selectivity . 38
535.1.4 Total selectivity . 38
535.1.5 Enhanced selectivity . 38
535.2 Co-ordination between residual current protective devices and OCPDs. 39
535.3 Selectivity between residual current protective devices . 39
535.4 Selectivity of RCD and OCPD . 39
535.5 Combined short-circuit protection of OCPDs . 39
536 Isolation and switching . 40
536.2 Isolation . 40
536.2.1 General . 40
536.2.2 Devices for isolation . 41
536.3 Switching-off for mechanical maintenance . 42
536.3.1 General . 42
536.3.2 Devices for switching-off for mechanical maintenance . 42
536.4 Emergency switching . 43
536.4.1 General . 43
536.4.2 Devices for emergency switching-off . 43
536.4.3 Devices for emergency stopping . 44
536.5 Functional switching (control) . 44
536.5.1 General . 44
536.5.2 Devices for functional switching . 44
537 Monitoring . 45
537.1 General . 45
537.1.1 Monitoring devices . 45
537.1.2 Selection of insulation monitoring devices (IMDs) . 45
537.1.3 Selection of residual current monitoring devices (RCMs) . 45
537.2 IT systems for continuity of supply . 45
537.2.1 General . 45
537.2.2 Insulation monitoring devices (IMDs) . 46
537.2.3 Installation of IMDs . 46
537.3 IT public distribution system . 46

– 4 – IEC 60364-5-53:2019 © IEC 2019
537.4 Off-line systems in TN, TT and IT systems . 46
Annex A (informative) Position of devices for overload protection . 48
A.1 General . 48
A.2 Cases where overload protection need not be placed at the origin of the
branch circuit . 48
Annex B (informative) Position of devices for short-circuit protection . 50
B.1 General . 50
B.2 Cases where short-circuit protection need not be placed at the origin of
branch circuit . 50
Annex C (informative) SPD installation – Examples of installation diagrams according
to system configurations . 52
C.1 TT system – 3 phase supply plus neutral . 52
C.2 TN-C and TN-C-S systems – 3 phase supply . 56
C.3 TN-S system – 3 phase supply plus neutral . 60
C.4 IT system – 3 phase supply with or without neutral . 62
Annex D (informative) Installation supplied by overhead lines . 65
Annex E (normative) Reference standards for devices for isolation and switching . 66
Annex F (informative) List of notes concerning certain countries . 68
Bibliography . 75

Figure 1 – Example of installation of class I, class II and class III tested SPDs . 25
Figure 2 – Connection type CT1 (4+0-configuration) for a three-phase system with
neutral . 26
Figure 3 – Connection type CT1 (3+0-configuration) for a three-phase system . 26
Figure 4 – Connection type CT2 (e.g. 3+1-configuration) for a three-phase system with

neutral . 27
Figure 5 – Connection points of an SPD assembly . 31
Figure 6 – Example of overcurrent protection in the SPD branch by using a dedicated
external overcurrent protective device. 32
Figure 7 – Protective device, which is a part of the installation, also used to protect the
SPD . 33
Figure 8 – Connection of the SPD . 35
Figure 9 – Example of installation of an SPD in order to decrease lead length of SPD

supply conductors . 36
Figure 10 – Example of selectivity . 38
Figure 11 – Example of currents and their correlation to selectivity . 39
Figure 12 – Example of combined short-circuit protection of OCPDs . 40
Figure A.1 – Overload protective device (P ) not at the origin of branch circuit (B) . 48
Figure A.2 – Overload protective device (P ) installed within 3 m of the origin of the
branch circuit (B) . 49
Figure B.1 – Limited change of position of short-circuit protective device (P ) on a
branch circuit . 50
Figure B.2 – Short-circuit protective device P installed at a point on the supply side
of the origin of a branch circuit . 51
Figure C.1 – Example of SPDA installation with connexion type CT2 on the supply side
(upstream) of the main RCD in TT system. 52
Figure C.2 – Example of SPD installation with connexion type CT2 on the supply side
(upstream) of the main RCD in TT system. 53

Figure C.3 – Example of SPDA installation on the load side (downstream) of the main
RCD in TT system . 54
Figure C.4 – Example of SPD installation on the load side (downstream) of the RCD in

TT system . 55
Figure C.5 – Example of SPDA installation in TN-C system . 56
Figure C.6 – Example of SPD installation with connexion type CT1 in TN-C system . 57
Figure C.7 – Example of SPD installation in TN-C-S system where the PEN is
separated into PE and N at the origin of the installation (upstream of the SPD) . 58
Figure C.8 – Example of SPDs installation in TN-C-S in different distribution boards . 59
Figure C.9 – Example of SPDA installation in TN-S system . 60
Figure C.10 – Example of SPDs installation in TN-S . 61
Figure C.11 – Example of SPDA installation in IT system with neutral . 62
Figure C.12 – Example of SPD installation in IT system without neutral . 63
Figure C.13 – Example of SPD installation in IT system with neutral . 64
Figure F.1 – Single user . 71
Figure F.2 – Several users . 71
Figure F.3 – Lamp control circuit with switching in the neutral conductor . 73

Table 1 – Required rated impulse voltage of equipment . 28
Table 2 – U of the SPD dependent on supply system configuration . 29
c
Table 3 – Nominal discharge current (I ) in kA depending on supply system and
n
connection type . 30
Table 4 – Selection of impulse discharge current (I ) where the building is protected
imp
against direct lightning strike . 30
Table 5 – Connection of the SPD dependent on supply system . 34
Table D.1 – Selection of impulse discharge current (I ) . 65
imp
Table E.1 – Devices for isolation and switching. 66

– 6 – IEC 60364-5-53:2019 © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LOW-VOLTAGE ELECTRICAL INSTALLATIONS –

Part 5-53: Selection and erection of electrical equipment – Devices for
protection for safety, isolation, switching, control and monitoring

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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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.
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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.
International Standard IEC 60364 has been prepared by IEC technical committee 64:
Electrical installations and protection against electric shock.
This bilingual version (2019-11) corresponds to the monolingual English version, published in
2019-02.
This fourth edition cancels and replaces the third edition published in 2001,
Amendment 1:2002 and Amendment 2:2015. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) revision of all clauses except 531 and 534;
b) introduction of a new Clause 537 Monitoring;
c) Clause 530 contains all normative references and all terms and definitions.

The text of this International Standard is based on the following documents:
FDIS Report on voting
64/2352/FDIS 64/2359/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
The French version of this standard has not been voted upon.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The reader's attention is drawn to the fact that Annex F lists all of the “in-some-country”
clauses on differing practices relating to the subject of this standard.
A list of all parts in the IEC 60364 series, published under the general title Low-voltage
electrical installations, 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 "http://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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication 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.
– 8 – IEC 60364-5-53:2019 © IEC 2019
LOW-VOLTAGE ELECTRICAL INSTALLATIONS –

Part 5-53: Selection and erection of electrical equipment – Devices for
protection for safety, isolation, switching, control and monitoring

530.1 Scope
This document provides requirements for:
a) isolation, switching, control and monitoring, and
b) selection and erection of:
1) devices for isolation, switching, control and monitoring, and
2) devices to achieve compliance with measures of protection for safety.
530.2 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 60204-1, Safety of machinery – Electrical equipment of machines – Part 1: General
requirements
IEC 60269-2, Low-voltage fuses – Part 2: Supplementary requirements for fuses for use by
authorized persons (fuses mainly for industrial application) – Examples of standardized
systems of fuses A to K
IEC 60269-3, Low-voltage fuses – Part 3: Supplementary requirements for fuses for use by
unskilled persons (fuses mainly for household and similar applications) – Examples of
standardized systems of fuses A to F
IEC 60269-4, Low-voltage fuses – Part 4: Supplementary requirements for use-links for the
protection of semiconductor devices
IEC 60309 (all parts), Plugs, socket-outlets and couplers for industrial purposes
IEC 60364 (all parts), Low-voltage electrical installations
IEC 60364-4-41:2005, Low-voltage electrical installations – Part 4-41: Protection for safety –
Protection against electric shock
IEC 60364-4-41:2005/AMD1:2017
IEC 60364-4-42:2010, Low-voltage electrical installations – Part 4-42: Protection for safety –
Protection against thermal effects
IEC 60364-4-42:2010/AMD1:2014
IEC 60364-4-43:2008, Low-voltage electrical installations – Part 4-43: Protection for safety –
Protection against overcurrent
IEC 60364-4-44:2007, Low-voltage electrical installations – Part 4-44: Protection for safety –
Protection against voltage disturbances and electromagnetic disturbances
IEC 60364-4-44:2007/AMD1:2015
IEC 60364-5-55, Electrical installations of buildings – Part 5-55: Selection and erection of
electrical equipment – Other equipment
IEC 60364-6:2016, Low voltage electrical installations– Part 6: Verification
IEC 60417 (all parts), Graphical symbols for use on equipment
IEC 60664-1:2007, Insulation coordination for equipment within low-voltage systems –
Part 1: Principles, requirements and tests
IEC 60669-1, Switches for household and similar fixed-electrical installations –
Part 1: General requirements
IEC 60669-2-1, Switches for household and similar fixed electrical installations –
Part 2-1: Particular requirements – Electronic switches
IEC 60669-2-2, Switches for household and similar fixed electrical installations –
Part 2-2: Particular requirements – Electromagnetic remote-control switches (RCS)
IEC 60669-2-3, Switches for household and similar fixed electrical installations –
Part 2-3: Particular requirements – Time-delay switches (TDS)
IEC 60669-2-4, Switches for household and similar fixed electrical installations –
Part 2-4: Particular requirements – Isolating switches
IEC 60669-2-5, Switches for household and similar fixed electrical installations –
Part 2-5: Particular requirements – Switches and related accessories for use in home and
building electronic systems (HBES)
IEC 60669-2-6, Switches for household and similar fixed electrical installations –
Part 2-6: Particular requirements – Fireman's switches for exterior and interior signs and
luminaires
IEC 60670-24, Boxes and enclosures for electrical accessories for household and similar fixed
electrical installations – Part 24: Particular requirements for enclosures for housing protective
devices and other power dissipating electrical equipment
IEC 60884 (all parts), Plugs and socket-outlets for household and similar purposes
IEC 60898 (all parts), Electrical accessories – Circuit-breakers for overcurrent protection for
household and similar installations
IEC 60906 (all parts), IEC system of plugs and socket-outlets for household and similar
purposes
IEC 60947-2:2016, Low-voltage switchgear and controlgear – Part 2: Circuit-breakers
IEC 60947-3, Low-voltage switchgear and controlgear – Part 3: Switches, disconnectors,
switch-disconnectors and fuse-combination units
IEC 60947-4-1, Low-voltage switchgear and controlgear – Part 4-1: Contactors and motor-
starters – Electromechanical contactors and motor-starters
IEC 60947-4-2, Low-voltage switchgear and controlgear – Part 4-2: Contactors and motor-
starters – AC semiconductor motor controllers and starters

– 10 – IEC 60364-5-53:2019 © IEC 2019
IEC 60947-4-3, Low-voltage switchgear and controlgear – Part 4-3: Contactors and motor-
starters – AC semiconductor controllers and contactors for non-motor loads
IEC 60947-5-1, Low-voltage switchgear and controlgear – Part 5-1: Control circuit devices
and switching elements – Electromechanical control circuit devices
IEC 60947-6-1, Low-voltage switchgear and controlgear – Part 6-1: Multiple function
equipment – Transfer switching equipment
IEC 60947-6-2, Low-voltage switchgear and controlgear – Part 6-2: Multiple function
equipment – Control and protective switching devices (or equipment) (CPS)
IEC 61008 (all parts), Residual current operated circuit-breakers without integral overcurrent
protection for household and similar uses (RCCBs)
IEC 61009 (all parts), Residual current operated circuit-breakers with integral overcurrent
protection for household and similar uses (RCBOs)
IEC 61095, Electromechanical contactors for household and similar purposes
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 61439-6, Low-voltage switchgear and controlgear assemblies – Part 6: Busbar trunking
systems (busways)
IEC 61534 (all parts), Powertrack systems
IEC 61557-8, Electrical safety in low voltage distribution systems up to 1 000 V a.c. and
1 500 V d.c. – Equipment for testing, measuring or monitoring of protective measures –
Part 8: Insulation monitoring devices for IT systems
IEC 61557-9, Electrical safety in low voltage distribution systems up to 1 000 V a.c. and
1 500 V d.c. – Equipment for testing, measuring or monitoring of protective measures –
Part 9: Equipment for insulation fault location in IT systems
IEC 61643-11, Low-voltage surge protective devices – Part 11: Surge protective devices
connected to low-voltage power systems – Requirements and test methods
IEC 61643-12, Low-voltage surge protective devices – Part 12: Surge protective devices
connected to low-voltage power distribution systems – Selection and application principles
IEC 61984:2008, Connectors – Safety requirements and tests
IEC 61995 (all parts), Devices for the connection of luminaires for household and similar
purposes
IEC 62020, Electrical accessories – Residual current monitors for household and similar uses
(RCMs)
IEC 62208, Empty enclosures for low-voltage switchgear and controlgear assemblies –
General requirements
IEC 62305 (all parts), Protection against lightning
IEC 62423, Type F and type B residual current operated circuit-breakers with and without
integral overcurrent protection for household and similar uses
IEC 62606, General requirements for arc fault detection devices
IEC 62626-1, Low-voltage switchgear and controlgear enclosed equipment – Part 1: Enclosed
switch-disconnectors outside the scope of IEC 60947-3 to provide isolation during repair and
maintenance work
530.3 Terms and definitions
For the purposes of this document, the following terms and definitions 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.
530.3.1
disconnector
mechanical switching device which in the open position complies with the requirements
specified for the isolating function
Note 1 to entry: A disconnector is capable of opening and closing a circuit when either negligible current is
broken or made, or when no significant change in the voltage across the terminals of each of the poles of the
disconnector occurs. It is also capable of carrying currents under normal circuit conditions and carrying for a
specified time currents under abnormal conditions such as those of short-circuit.
[SOURCE: IEC 60050-441:2000, 441-14-05, modified – Referring to isolating function instead
of isolating distance.]
530.3.2
switch disconnector
switch which, in the open position, satisfies the isolating requirements specified for a
disconnector
[SOURCE: IEC 60050-441:1984, 441-14-12]
530.3.3
mechanical switch
device capable of making, carrying and breaking currents through contacts controlled by
mechanical operation under normal circuit conditions which may include specified operating
overload conditions and also carrying for specified time currents under specified abnormal
circuit conditions such as those of short-circuit
Note 1 to entry: A switch can be capable of making but not breaking short-circuit currents.
[SOURCE: IEC 60050-441:2000, 441-14-10, modified – "through contacts controlled by
mechanical operation" has been added.]
530.3.4
switching-off for mechanical maintenance
opening operation of a switching device intended to inactivate an item or items of electrically
powered equipment for the purpose of preventing a hazard, other than due to electric shock or
to arcing, during non-electrical work on the equipment

– 12 – IEC 60364-5-53:2019 © IEC 2019
[SOURCE: IEC 60050-826:2004, 826-17-02]
530.3.5
emergency switching-off
opening operation of a switching device intended to remove electric power from an electrical
installation to avert or alleviate a hazardous situation
[SOURCE: IEC 60050-826:2004, 826-17-03]
530.3.6
emergency stopping
operation intended to stop as quickly as possible a movement which has become dangerous
[SOURCE: IEC 60050-826:2004, 826-17-04]
530.3.7
functional switching
operation intended to switch on or off or vary the supply of electric energy to an electrical
installation or parts of it for normal operating purposes
[SOURCE: IEC 60050-826:2004, 826-17-05]
530.3.8
SPD assembly
one SPD or a set of SPDs, in both cases including all SPD disconnectors required by the SPD
manufacturer, providing the required overvoltage protection for a type of system earthing
530.3.9
SPD disconnector
disconnector
device for disconnecting an SPD, or part of an SPD, from the power system
Note 1 to entry: This disconnecting device is not required to have isolating capability for safety purposes. It is to
prevent a persistent fault on the system and is used to give an indication of an SPD’s failure. Disconnectors can be
internal (built in) or external (required by the manufacturer). There may be more than one disconnector function, for
example an overcurrent protection function and a thermal protection function. These functions may be in separate
units.
[SOURCE: IEC 61643-11:2011, 3.1.28]
530.3.10
mode of protection of an SPD
intended current path, between terminals that contains protective components, e.g. line-to-
line, line-to-earth, line-to-neutral, neutral-to-earth
[SOURCE: IEC 61643-11:2011, 3.1.8]
530.3.11
follow current interrupt rating
I
fi
prospective short-circuit current that an SPD is able to interrupt without operation of a
disconnector
[SOURCE: IEC 61643-11:2011, 3.1.39]

530.3.12
short-circuit current rating
I
SCCR
maximum prospective short-circuit current from the power system for which the SPD, in
conjunction with the disconnector specified, is rated
[SOURCE: IEC 61643-11:2011, 3.1.27]
530.3.13
voltage protection level
U
P
maximum voltage to be expected at the SPD terminals due to an impulse stress with defined
voltage steepness and an impulse stress with a discharge current with given amplitude and
waveshape
Note 1 to entry: The voltage protection level is g
...

IEC 60364-5-53 ®
Edition 4.1 2020-12
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Low-voltage electrical installations –
Part 5-53: Selection and erection of electrical equipment – Devices
for protection for safety, isolation, switching, control and monitoring

Installations électriques à basse tension –
Partie 5-53: Choix et mise en oeuvre des matériels électriques – Dispositifs
de protection pour assurer la sécurité, le sectionnement, la coupure,
la commande et la surveillance

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IEC 60364-5-53 ®
Edition 4.1 2020-12
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Low-voltage electrical installations –

Part 5-53: Selection and erection of electrical equipment – Devices

for protection for safety, isolation, switching, control and monitoring

Installations électriques à basse tension –

Partie 5-53: Choix et mise en oeuvre des matériels électriques – Dispositifs

de protection pour assurer la sécurité, le sectionnement, la coupure,

la commande et la surveillance

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.130.01; 91.140.50 ISBN 978-2-8322-9201-3

IEC 60364-5-53 ®
Edition 4.1 2020-12
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
Low-voltage electrical installations –
Part 5-53: Selection and erection of electrical equipment – Devices
for protection for safety, isolation, switching, control and monitoring

Installations électriques à basse tension –
Partie 5-53: Choix et mise en oeuvre des matériels électriques – Dispositifs
de protection pour assurer la sécurité, le sectionnement, la coupure,
la commande et la surveillance

– 2 – IEC 60364-5-53:2019+AMD1:2020 CSV
© IEC 2020
CONTENTS
FOREWORD . 6
530.1 Scope . 8
530.2 Normative references . 8
530.3 Terms and definitions . 11
530.4 General and common requirements. 14
530.5 Erection of equipment . 14
531 Devices for protection against indirect contact by automatic disconnection of
supply.
531.1 Overcurrent protective devices .
531.1.1 TN systems .
531.1.2 TT systems .
531.1.3 IT systems .
531.2 Residual current protective devices.
531.2.1 General conditions of installation .
531.2.2 Selection of devices according to their method of application .
531.2.3 TN systems .
531.2.4 TT systems .
531.2.5 IT systems .
531.3 Insulation monitoring devices .
531 Equipment for protection against electric shock . 16
531.1 General . 16
531.2 Devices for automatic disconnection of supply . 17
531.2.1 General . 17
531.2.2 Overcurrent protective devices . 17
531.2.3 Residual current protective devices . 19
531.3 Equipment for protection by double or reinforced insulation . 22
531.4 Equipment for protection by electrical separation . 24
531.5 Equipment for protection by extra-low-voltage provided by SELV and PELV
systems . 24
531.5.1 Sources for SELV or PELV systems . 24
531.5.2 Selection of plugs and socket-outlets . 24
531.6 Devices for additional protection . 24
531.7 Monitoring devices . 25
532 Devices and precautions for protection against thermal effects . 25
532.1 General . 25
532.2 Locations with a particular risk of fire . 25
532.2.1 General . 25
532.2.2 Locations with external influences BD2, BD3 or BD4 . 25
532.2.3 Locations with external influences BE2 . 26
532.3 Selection of arc fault detection devices (AFDD) . 26
533 Devices for protection against overcurrent . 27
533.1 General requirements . 27
533.1.1 General . 27
533.1.2 Compliance with standards . 27
533.1.3 Fuses . 28
533.2 Selection of devices for protection against overload current . 28

© IEC 2020
533.2.1 General . 28
533.2.2 Presence of harmonic currents . 29
533.2.3 Unequal current sharing between parallel conductors . 29
533.3 Selection of devices for protection against short-circuit current . 29
533.3.1 Thermal stresses . 29
533.3.2 Breaking capacity . 30
533.4 Positioning of overcurrent protection devices . 30
533.4.1 General . 30
533.4.2 Positioning of devices for overload protection . 30
533.4.3 Positioning of devices for short-circuit protection . 31
533.5 Co-ordination of overload and short-circuit protective functions. 32
533.5.1 Protective functions provided by one device . 32
533.5.2 Protective functions provided by separate devices . 32
534 Devices for protection against transient overvoltages . 32
534.1 General . 32
534.2 Void . 33
534.3 Void . 33
534.4 Selection and erection of SPDs . 33
534.4.1 SPD location and SPD test class . 33
534.4.2 Transient overvoltage protection requirements . 34
534.4.3 Connection types . 34
534.4.4 Selection of SPDs . 36
534.4.5 Protection of the SPD against overcurrent . 40
534.4.6 Fault protection . 42
534.4.7 SPDs installation in conjunction with RCDs. 43
534.4.8 Connections of the SPD . 43
534.4.9 Effective protective distance of SPDs . 45
534.4.10 Connecting conductors of SPDs . 46
535 Co-ordination of protective devices . 46
535.1 Selectivity between overcurrent protective devices . 46
535.1.1 General . 46
535.1.2 Partial selectivity . 47
535.1.3 Full selectivity . 47
535.1.4 Total selectivity . 47
535.1.5 Enhanced selectivity . 47
535.2 Co-ordination between residual current protective devices and OCPDs. 48
535.3 Selectivity between residual current protective devices . 48
535.4 Selectivity of RCD and OCPD . 48
535.5 Combined short-circuit protection of OCPDs . 48
536 Isolation and switching . 49
536.2 Isolation . 49
536.2.1 General . 49
536.2.2 Devices for isolation . 50
536.3 Switching-off for mechanical maintenance . 51
536.3.1 General . 51
536.3.2 Devices for switching-off for mechanical maintenance . 51
536.4 Emergency switching . 52
536.4.1 General . 52
536.4.2 Devices for emergency switching-off . 52

– 4 – IEC 60364-5-53:2019+AMD1:2020 CSV
© IEC 2020
536.4.3 Devices for emergency stopping . 53
536.5 Functional switching (control) . 53
536.5.1 General . 53
536.5.2 Devices for functional switching . 53
537 Monitoring . 54
537.1 General . 54
537.1.1 Monitoring devices . 54
537.1.2 Selection of insulation monitoring devices (IMDs) . 54
537.1.3 Selection of residual current monitoring devices (RCMs) . 54
537.2 IT systems for continuity of supply . 54
537.2.1 General . 54
537.2.2 Insulation monitoring devices (IMDs) . 55
537.2.3 Installation of IMDs . 55
537.3 IT public distribution system . 55
537.4 Off-line systems in TN, TT and IT systems . 55
Annex A (informative) Position of devices for overload protection . 57
A.1 General . 57
A.2 Cases where overload protection need not be placed at the origin of the
branch circuit . 57
Annex B (informative) Position of devices for short-circuit protection . 59
B.1 General . 59
B.2 Cases where short-circuit protection need not be placed at the origin of
branch circuit . 59
Annex C (informative) SPD installation – Examples of installation diagrams according
to system configurations . 61
C.1 TT system – 3 phase supply plus neutral . 61
C.2 TN-C and TN-C-S systems – 3 phase supply . 65
C.3 TN-S system – 3 phase supply plus neutral . 69
C.4 IT system – 3 phase supply with or without neutral . 71
Annex D (informative) Installation supplied by overhead lines . 74
Annex E (normative) Reference standards for devices for isolation and switching . 75
Annex F (informative) List of notes concerning certain countries . 77
Annex G (informative) Description of the different types of residual current devices

(RCDs) . 86
Bibliography . 90

Figure 1 – Example of installation of class I, class II and class III tested SPDs . 34
Figure 2 – Connection type CT1 (4+0-configuration) for a three-phase system with
neutral . 35
Figure 3 – Connection type CT1 (3+0-configuration) for a three-phase system . 35
Figure 4 – Connection type CT2 (e.g. 3+1-configuration) for a three-phase system with
neutral . 36
Figure 5 – Connection points of an SPD assembly . 40
Figure 6 – Example of overcurrent protection in the SPD branch by using a dedicated
external overcurrent protective device. 41
Figure 7 – Protective device, which is a part of the installation, also used to protect
the SPD . 42
Figure 8 – Connection of the SPD . 44

© IEC 2020
Figure 9 – Example of installation of an SPD in order to decrease lead length of SPD
supply conductors . 45
Figure 10 – Example of selectivity . 47
Figure 11 – Example of currents and their correlation to selectivity . 48
Figure 12 – Example of combined short-circuit protection of OCPDs . 49
Figure A.1 – Overload protective device (P ) not at the origin of branch circuit (B) . 57
Figure A.2 – Overload protective device (P ) installed within 3 m of the origin of the
branch circuit (B) . 58
Figure B.1 – Limited change of position of short-circuit protective device (P ) on a
branch circuit . 59
Figure B.2 – Short-circuit protective device P installed at a point on the supply side
of the origin of a branch circuit . 60
Figure C.1 – Example of SPDA installation with connexion type CT2 on the supply side

(upstream) of the main RCD in TT system. 61
Figure C.2 – Example of SPD installation with connexion type CT2 on the supply side
(upstream) of the main RCD in TT system. 62
Figure C.3 – Example of SPDA installation on the load side (downstream) of the main
RCD in TT system . 63
Figure C.4 – Example of SPD installation on the load side (downstream) of the RCD in

TT system . 64
Figure C.5 – Example of SPDA installation in TN-C system . 65
Figure C.6 – Example of SPD installation with connexion type CT1 in TN-C system . 66
Figure C.7 – Example of SPD installation in TN-C-S system where the PEN is
separated into PE and N at the origin of the installation (upstream of the SPD) . 67
Figure C.8 – Example of SPDs installation in TN-C-S in different distribution boards . 68
Figure C.9 – Example of SPDA installation in TN-S system . 69
Figure C.10 – Example of SPDs installation in TN-S . 70
Figure C.11 – Example of SPDA installation in IT system with neutral . 71
Figure C.12 – Example of SPD installation in IT system without neutral . 72
Figure C.13 – Example of SPD installation in IT system with neutral . 73
Figure F.1 – Single user . 82
Figure F.2 – Several users . 82
Figure F.3 – Lamp control circuit with switching in the neutral conductor . 84
Figure G.1 – Possible earth fault currents in systems with semiconductors . 89

Table 1 – Required rated impulse voltage of equipment . 37
Table 2 – U of the SPD dependent on supply system configuration . 38
c
Table 3 – Nominal discharge current (I ) in kA depending on supply system and
n
connection type . 39
Table 4 – Selection of impulse discharge current (I ) where the building is protected
imp
against direct lightning strike . 39
Table 5 – Connection of the SPD dependent on supply system . 43
Table D.1 – Selection of impulse discharge current (I ) . 74
imp
Table E.1 – Devices for isolation and switching. 75

– 6 – IEC 60364-5-53:2019+AMD1:2020 CSV
© IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LOW-VOLTAGE ELECTRICAL INSTALLATIONS –

Part 5-53: Selection and erection of electrical equipment – Devices for
protection for safety, isolation, switching, control and monitoring

FOREWORD
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This consolidated version of the official IEC Standard and its amendment has been
prepared for user convenience.
IEC 60364-5-53 edition 4.1 contains the fourth edition (2019-02) [documents
64/2352/FDIS and 64/2359/RVD] and its amendment 1 (2020-12) [documents
64/2457/FDIS and 64/2465/RVD].
In this Redline version, a vertical line in the margin shows where the technical content
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© IEC 2020
International Standard IEC 60364 has been prepared by IEC technical committee 64:
Electrical installations and protection against electric shock.
This fourth edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) revision of all clauses except 531 and 534;
b) introduction of a new Clause 537 Monitoring;
c) Clause 530 contains all normative references and all terms and definitions.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The reader's attention is drawn to the fact that Annex F lists all of the “in-some-country”
clauses on differing practices relating to the subject of this standard.
A list of all parts in the IEC 60364 series, published under the general title Low-voltage
electrical installations, can be found on the IEC website.
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understanding of its contents. Users should therefore print this document using a
colour printer.
– 8 – IEC 60364-5-53:2019+AMD1:2020 CSV
© IEC 2020
LOW-VOLTAGE ELECTRICAL INSTALLATIONS –

Part 5-53: Selection and erection of electrical equipment – Devices for
protection for safety, isolation, switching, control and monitoring

530.1 Scope
This document provides requirements for:
a) isolation, switching, control and monitoring, and
b) selection and erection of:
1) devices for isolation, switching, control and monitoring, and
2) devices to achieve compliance with measures of protection for safety.
530.2 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 60204-1, Safety of machinery – Electrical equipment of machines – Part 1: General
requirements
IEC 60269-2, Low-voltage fuses – Part 2: Supplementary requirements for fuses for use by
authorized persons (fuses mainly for industrial application) – Examples of standardized
systems of fuses A to K
IEC 60269-3, Low-voltage fuses – Part 3: Supplementary requirements for fuses for use by
unskilled persons (fuses mainly for household and similar applications) – Examples of
standardized systems of fuses A to F
IEC 60269-4, Low-voltage fuses – Part 4: Supplementary requirements for use-links for the
protection of semiconductor devices
IEC 60309 (all parts), Plugs, socket-outlets and couplers for industrial purposes
IEC 60364 (all parts), Low-voltage electrical installations
IEC 60364-4-41:2005, Low-voltage electrical installations – Part 4-41: Protection for safety –
Protection against electric shock
IEC 60364-4-41:2005/AMD1:2017
IEC 60364-4-42:2010, Low-voltage electrical installations – Part 4-42: Protection for safety –
Protection against thermal effects
IEC 60364-4-42:2010/AMD1:2014
IEC 60364-4-43:2008, Low-voltage electrical installations – Part 4-43: Protection for safety –
Protection against overcurrent
IEC 60364-4-44:2007, Low-voltage electrical installations – Part 4-44: Protection for safety –
Protection against voltage disturbances and electromagnetic disturbances
IEC 60364-4-44:2007/AMD1:2015
© IEC 2020
IEC 60364-5-55, Electrical installations of buildings – Part 5-55: Selection and erection of
electrical equipment – Other equipment
IEC 60364-6:2016, Low voltage electrical installations– Part 6: Verification
IEC 60417 (all parts), Graphical symbols for use on equipment
IEC 60664-1:2007, Insulation coordination for equipment within low-voltage systems –
Part 1: Principles, requirements and tests
IEC 60669-1, Switches for household and similar fixed-electrical installations –
Part 1: General requirements
IEC 60669-2-1, Switches for household and similar fixed electrical installations –
Part 2-1: Particular requirements – Electronic switches
IEC 60669-2-2, Switches for household and similar fixed electrical installations –
Part 2-2: Particular requirements – Electromagnetic remote-control switches (RCS)
IEC 60669-2-3, Switches for household and similar fixed electrical installations –
Part 2-3: Particular requirements – Time-delay switches (TDS)
IEC 60669-2-4, Switches for household and similar fixed electrical installations –
Part 2-4: Particular requirements – Isolating switches
IEC 60669-2-5, Switches for household and similar fixed electrical installations –
Part 2-5: Particular requirements – Switches and related accessories for use in home and
building electronic systems (HBES)
IEC 60669-2-6, Switches for household and similar fixed electrical installations –
Part 2-6: Particular requirements – Fireman's switches for exterior and interior signs and
luminaires
IEC 60670-24, Boxes and enclosures for electrical accessories for household and similar fixed
electrical installations – Part 24: Particular requirements for enclosures for housing protective
devices and other power dissipating electrical equipment
IEC 60884 (all parts), Plugs and socket-outlets for household and similar purposes
IEC 60898 (all parts), Electrical accessories – Circuit-breakers for overcurrent protection for
household and similar installations
IEC 60906 (all parts), IEC system of plugs and socket-outlets for household and similar
purposes
IEC 60947-2:2016, Low-voltage switchgear and controlgear – Part 2: Circuit-breakers
IEC 60947-3, Low-voltage switchgear and controlgear – Part 3: Switches, disconnectors,
switch-disconnectors and fuse-combination units
IEC 60947-4-1, Low-voltage switchgear and controlgear – Part 4-1: Contactors and motor-
starters – Electromechanical contactors and motor-starters
IEC 60947-4-2, Low-voltage switchgear and controlgear – Part 4-2: Contactors and motor-
starters – AC semiconductor motor controllers and starters

– 10 – IEC 60364-5-53:2019+AMD1:2020 CSV
© IEC 2020
IEC 60947-4-3, Low-voltage switchgear and controlgear – Part 4-3: Contactors and motor-
starters – AC semiconductor controllers and contactors for non-motor loads
IEC 60947-5-1, Low-voltage switchgear and controlgear – Part 5-1: Control circuit devices
and switching elements – Electromechanical control circuit devices
IEC 60947-6-1, Low-voltage switchgear and controlgear – Part 6-1: Multiple function
equipment – Transfer switching equipment
IEC 60947-6-2, Low-voltage switchgear and controlgear – Part 6-2: Multiple function
equipment – Control and protective switching devices (or equipment) (CPS)
IEC 61008 (all parts), Residual current operated circuit-breakers without integral overcurrent
protection for household and similar uses (RCCBs)
IEC 61009 (all parts), Residual current operated circuit-breakers with integral overcurrent
protection for household and similar uses (RCBOs)
IEC 61095, Electromechanical contactors for household and similar purposes
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 61439-6, Low-voltage switchgear and controlgear assemblies – Part 6: Busbar trunking
systems (busways)
IEC 61534 (all parts), Powertrack systems
IEC 61557-8, Electrical safety in low voltage distribution systems up to 1 000 V a.c. and
1 500 V d.c. – Equipment for testing, measuring or monitoring of protective measures –
Part 8: Insulation monitoring devices for IT systems
IEC 61557-9, Electrical safety in low voltage distribution systems up to 1 000 V a.c. and
1 500 V d.c. – Equipment for testing, measuring or monitoring of protective measures –
Part 9: Equipment for insulation fault location in IT systems
IEC 61643-11, Low-voltage surge protective devices – Part 11: Surge protective devices
connected to low-voltage power systems – Requirements and test methods
IEC 61643-12, Low-voltage surge protective devices – Part 12: Surge protective devices
connected to low-voltage power distribution systems – Selection and application principles
IEC 61984:2008, Connectors – Safety requirements and tests
IEC 61995 (all parts), Devices for the connection of luminaires for household and similar
purposes
IEC 62020, Electrical accessories – Residual current monitors for household and similar uses
(RCMs)
IEC 62208, Empty enclosures for low-voltage switchgear and controlgear assemblies –
General requirements
© IEC 2020
IEC 62305 (all parts), Protection against lightning
IEC 62423, Type F and type B residual current operated circuit-breakers with and without
integral overcurrent protection for household and similar uses
IEC 62606, General requirements for arc fault detection devices
IEC 62626-1, Low-voltage switchgear and controlgear enclosed equipment – Part 1: Enclosed
switch-disconnectors outside the scope of IEC 60947-3 to provide isolation during repair and
maintenance work
530.3 Terms and definitions
For the purposes of this document, the following terms and definitions 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.
530.3.1
disconnector
mechanical switching device which in the open position complies with the requirements
specified for the isolating function
Note 1 to entry: A disconnector is capable of opening and closing a circuit when either negligible current is
broken or made, or when no significant change in the voltage across the terminals of each of the poles of the
disconnector occurs. It is also capable of carrying currents under normal circuit conditions and carrying for a
specified time currents under abnormal conditions such as those of short-circuit.
[SOURCE: IEC 60050-441:2000, 441-14-05, modified – Referring to isolating function instead
of isolating distance.]
530.3.2
switch disconnector
switch which, in the open position, satisfies the isolating requirements specified for a
disconnector
[SOURCE: IEC 60050-441:1984, 441-14-12]
530.3.3
mechanical switch
device capable of making, carrying and breaking currents through contacts controlled by
mechanical operation under normal circuit conditions which may include specified operating
overload conditions and also carrying for specified time currents under specified abnormal
circuit conditions such as those of short-circuit
Note 1 to entry: A switch can be capable of making but not breaking short-circuit currents.
[SOURCE: IEC 60050-441:2000, 441-14-10, modified – "through contacts controlled by
mechanical operation" has been added.]
530.3.4
switching-off for mechanical mai
...