IEC 60664-1:2020/AMD1:2025

IEC 60664-1 ®
Edition 3.0 2025-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
BASIC SAFETY PUBLICATION
PUBLICATION FONDAMENTALE DE SÉCURITÉ
HORIZONTAL PUBLICATION
PUBLICATION HORIZONTALE
AMENDEMENT 1
AMENDEMENT 1
Insulation coordination for equipment within low-voltage supply systems –
Part 1: Principles, requirements and tests

Coordination de l'isolement des matériels dans les réseaux d'énergie électrique
à basse tension –
Partie 1: Principes, exigences et essais
ICS 29.080.30  ISBN 978-2-8327-0344-1

IEC 60664-1:2020-05/AMD1:2025-05(en-fr)

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– 2 – IEC 60664-1:2020/AMD1:2025
© IEC 2025
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INSULATION COORDINATION FOR EQUIPMENT
WITHIN LOW-VOLTAGE SUPPLY SYSTEMS –

Part 1: Principles, requirements and tests

AMENDMENT 1
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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Amendment 1 to IEC 60664:2020 has been prepared by IEC technical committee 109:
Insulation co-ordination for low-voltage equipment.
The text of this Amendment is based on the following documents:
Draft Report on voting
109/235/FDIS 109/240/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
© IEC 2025
The language used for the development of this Amendment is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications/.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
___________
Throughout the document (except in the Bibliography), delete:
IEC 60364-4-44:2007
and replace with:
IEC 60364-4-44:2024.
1 Scope
Replace the first paragraph with the following:
This part of IEC 60664 deals with insulation coordination for electrical equipment having a
rated voltage up to AC 1 000 V or DC 1 500 V connected to low-voltage supply systems.
NOTE 1 Throughout this document, the term equipment is used with the meaning of electrical equipment.
Renumber NOTE 1 and NOTE 2 respectively as NOTE 2 and NOTE 3.
Add, at the end of the existing last paragraph, the following NOTE:
NOTE 4 Further explanations and examples with regard to the use of this document are provided in
IEC TR 60664-2-1.
– 4 – IEC 60664-1:2020/AMD1:2025
© IEC 2025
3.1 Terms and definitions
Add the following new terms:
3.1.48
electric power network
particular installations, substations, lines or cables for the transmission and distribution of
electricity
Note 1 to entry: The boundaries of the different parts of this network are defined by appropriate criteria, such as
geographical situation, ownership, voltage, etc.
[SOURCE: IEC 60050-601:1985, 601-01-02]
3.1.49
electrical installation
assembly of electrical equipment which is used for the generation, transmission, conversion,
distribution and/or use of electric energy
Note 1 to entry: The electrical installation includes energy sources e.g. local power supplies such as batteries,
capacitors and all other sources of stored electric energy.
[SOURCE: IEC 60050-651:2014, 651-26-01, modified – "e.g. local power supplies" has been
added to the Note to entry.]
3.1.50
electrical equipment
item used for generation, conversion, transmission, distribution or utilization of electric energy
Note 1 to entry: Examples of such items are electric machines, transformers, switchgear and controlgear, measuring
instruments, protective devices, wiring systems, and current-using equipment.
[SOURCE: IEC 60050-826:2022, 826-16-01]
3.1.51
electrochemical migration
transport of ions in an electrolyte due to an electric field
[SOURCE: IEC 60050-114:2014, 114-04-06]

4.2.2.5 Attenuation of transient overvoltage levels
Add, after third paragraph, the following:
Technical committees shall consider the end of life of the means to limit transient overvoltages.

4.3.2 Equipment energized directly from the mains supply
Replace the existing text of 4.3.2 with the following:
Equipment is considered to be energized directly from the mains supply when the equipment
is galvanically connected to an electric power network (either public or private).

© IEC 2025
When defining the rated impulse withstand voltage of equipment, technical committees shall
take into account the following overvoltage categories:
– Overvoltage category IV applies at, or in the proximity of, the point where an electrical
installation is connected to an electric power network.
NOTE 1 Equipment of overvoltage category IV has a very high impulse withstand capability providing the
required high degree of reliability at these locations, for example upstream of the main distribution board.
– Overvoltage category III applies in an electrical installation downstream of and including
the main distribution board.
NOTE 2 Examples of such equipment include distribution boards, local generation, circuit-breakers, wiring
systems (see IEC 60050-826:2022, 826-15-01), including cables, busbars, junction boxes, switches, socket-
outlets) and equipment for industrial use and some other equipment, e.g. stationary motors.
– Overvoltage category II applies for equipment connected to an electrical installation.
NOTE 3 Examples of such equipment are appliances, portable tools and similar loads with pluggable or
permanent connection to the electrical installation.
– Overvoltage category I applies to equipment that may only be connected to an electrical
installation when specific measures are provided.
NOTE 4 Such specific measures are related to transient overvoltages as well as to temporary overvoltages
and are addressed in 4.3.4.
Where a higher
...