SIST EN IEC 63552:2026

SLOVENSKI STANDARD
01-december-2026
Stikalna naprava za otočenje (SDFI) (IEC 63552:2026)
Switching device for islanding (SDFI) (IEC 63552:2026)
Besondere Anforderungen an Schaltgeräte für Inselbetrieb (IEC 63552:2026)
Appareil de connexion pour le passage en réseau séparé (SDFI) (IEC 63552:2026)
Ta slovenski standard je istoveten z: EN IEC 63552:2026
ICS:
27.015 Energijska učinkovitost. Energy efficiency. Energy
Ohranjanje energije na conservation in general
splošno
29.130.20 Nizkonapetostne stikalne in Low voltage switchgear and
krmilne naprave controlgear
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 63552

NORME EUROPÉENNE
EUROPÄISCHE NORM August 2026
ICS 27.015; 29.020
English Version
Switching device for islanding (SDFI)
(IEC 63552:2026)
Appareil de connexion pour le passage en réseau séparé Besondere Anforderungen an Schaltgeräte für Inselbetrieb
(SDFI) (IEC 63552:2026)
(IEC 63552:2026)
This European Standard was approved by CENELEC on 2026-07-07. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 63552:2026 E
European foreword
The text of document 23K/133/FDIS, future edition 1 of IEC 63552, prepared by SC 23K "Electrical
Energy Efficiency products" of IEC/TC 23 "Electrical accessories" was submitted to the IEC-CENELEC
parallel vote and approved by CENELEC as EN IEC 63552:2026.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2027-08-31
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2029-08-31
document have to be withdrawn
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 63552:2026 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standard indicated:
IEC 60364 (series) NOTE Approved as HD 60364 (series)
IEC 60364-8-1:2019 NOTE Approved as HD 60364-8-1:2019 (not modified)
IEC 60947-6-1:2021 NOTE Approved as EN IEC 60947-6-1:2023 (not modified)
IEC 63402 (series) NOTE Approved as EN IEC 63402 (series)
IEC 63402-1:2025 NOTE Approved as EN IEC 63402-1:2025 (not modified)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60364-8-82 2022 Low-voltage electrical installations - Part 8- HD 60364-8-82 2025
82: Functional aspects - Prosumer's low-
voltage electrical installations
IEC 60669-2-4 - Switches for household and similar fixed EN IEC 60669-2-4 -
electrical installations - Part 2-4: Particular
requirements - Isolating switches
IEC 60898-1 2015 Electrical accessories - Circuit-breakers for EN 60898-1 2019
overcurrent protection for household and
similar installations - Part 1: Circuit-
breakers for a.c. operation
- - + A11 2024
IEC 60898-2 - Electrical accessories - Circuit-breakers for EN 60898-2 -
overcurrent protection for household and
similar installations - Part 2: Circuit-
breakers for AC and DC operation
IEC 60947-2 - Low-voltage switchgear and controlgear - EN IEC 60947-2 -
Part 2: Circuit-breakers
IEC 60947-3 - Low-voltage switchgear and controlgear - EN IEC 60947-3 -
Part 3: Switches, disconnectors, switch-
disconnectors and fuse-combination units
IEC 60947-10 - Low-voltage switchgear and controlgear - EN IEC 60947-10 -
Part 10: Semiconductor circuit-breakers
IEC 61000-4-2 - Electromagnetic compatibility (EMC) - Part EN IEC 61000-4-2 -
4-2: Testing and measurement techniques
- Electrostatic discharge immunity test
IEC 61000-4-3 - Electromagnetic compatibility (EMC) - Part EN IEC 61000-4-3 -
4-3 : Testing and measurement techniques
- Radiated, radio-frequency,
electromagnetic field immunity test
IEC 61000-4-4 - Electromagnetic compatibility (EMC) - Part EN 61000-4-4 -
4-4: Testing and measurement techniques
- Electrical fast transient/burst immunity
test
IEC 61000-4-5 - Electromagnetic compatibility (EMC) - Part EN 61000-4-5 -
4-5: Testing and measurement techniques
- Surge immunity test
IEC 61000-4-6 - Electromagnetic compatibility (EMC) - Part EN IEC 61000-4-6 -
4-6: Testing and measurement techniques
- Immunity to conducted disturbances,
induced by radio-frequency fields
IEC 61000-4-8 - Electromagnetic compatibility (EMC) - Part EN 61000-4-8 -
4-8: Testing and measurement techniques
- Power frequency magnetic field immunity
test
IEC 61000-4-11 - Electromagnetic compatibility (EMC) - Part EN IEC 61000-4-11 -
4-11: Testing and measurement
techniques - Voltage dips, short
interruptions and voltage variations
immunity tests for equipment with input
current up to 16 A per phase
IEC 61000-6-1 - Electromagnetic compatibility (EMC) - Part EN IEC 61000-6-1 -
6-1: Generic standards - Immunity
standard for residential, commercial and
light-industrial environments
IEC 62991 2022 Particular requirements for source EN IEC 62991 2025
switching equipment (SSE)
IEC 63445 2025 System referencing conductor switching EN IEC 63445 2025
device
CISPR 14-1 - Electromagnetic compatibility - EN IEC 55014-1 -
Requirements for household appliances,
electric tools and similar apparatus - Part
1: Emission
IEC 63552 ®
Edition 1.0 2026-06
INTERNATIONAL
STANDARD
Switching device for islanding (SDFI)

ICS 27.015; 29.020 ISBN 978-2-8327-1264-1

IEC 63552:2026-06(en)
IEC 63552:2026 © IEC 2026
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 7
2 Normative references . 8
3 Terms and definitions . 9
4 Classification . 13
4.1 General . 13
4.2 According to the construction . 14
4.3 According to the method of integration of SRCSD . 14
4.4 According to the method of operation . 15
4.5 According to kind of current . 15
4.6 According to the number of switched poles . 15
4.7 According to SRCSD interlocking means . 15
4.8 According to the reclosing mode . 15
4.9 According to islanding means . 15
4.10 According to the type of isolation . 15
4.11 According to the type of local sources . 15
5 Characteristics . 16
6 Markings and product information . 16
7 Standard conditions for operation in service . 17
8 Requirements for construction and operation . 18
8.1 General requirements . 18
8.2 Construction requirements . 19
8.2.1 Mechanism . 19
8.2.2 SDFI operation and interlocking . 19
8.2.3 Manual reclosing of the SDFI . 21
8.2.4 Voltage and frequency deviations . 22
8.2.5 Voltage withstand between open contacts . 22
8.3 Reclosing operations (reconnection to grid connected mode) . 22
8.4 Operational endurance . 24
8.5 EMC . 24
9 Type tests . 24
9.1 General . 24
9.2 SDFI operation and interlocking . 24
9.3 Tests for manual reclosing . 25
9.4 Verification of operations upon deviations . 25
9.5 Test for reclosing operations . 26
9.5.1 General . 26
9.5.2 SDFI provided for closing without synchronization . 26
9.5.3 SDFI provided for reclosing with synchronization . 27
9.6 EMC tests . 28
9.6.1 General . 28
9.6.2 Electromagnetic emission . 28
9.6.3 Electromagnetic immunity . 28
Bibliography . 30

IEC 63552:2026 © IEC 2026
Figure 1 – Example of islandable PEI architecture . 6
Figure 2 – Example of SDFI architecture . 14
Figure 3 – SDFI operation principle . 20
Figure 4 – Example of architecture of a PEI operating in TT in connected mode and
becoming TN in island mode . 21
Figure 5 – Example of sequence diagram for operation upon source deviation and grid
loss for transition to island mode . 22
Figure 6 – Grid reconnection – without synchronization (open transition) . 23
Figure 7 – Grid reconnection – with synchronization (closed transition) . 23
Figure 8 – Example of typical undervoltage ride through capability profile . 26

Table 1 – Requirements and position for markings and other product information . 16
Table 2 – Values of influencing quantities . 18
Table 3 – Immunity tests and performance criteria . 29
Table 4 – Performance criteria . 29

IEC 63552:2026 © IEC 2026
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Switching device for islanding (SDFI)

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
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preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
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expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 63552 has been prepared by subcommittee 23K: Electrical energy efficiency products, of
IEC technical committee 23: Electrical accessories. It is an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
23K/133/FDIS 23K/135/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
IEC 63552:2026 © IEC 2026
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.
In this document, the following print types are used:
– conformity statements: in italic type.
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.
IEC 63552:2026 © IEC 2026
INTRODUCTION
IEC 60364-8-82 aims to ensure that low-voltage electrical installations are compatible with both
current and future methods for safely and effectively delivering electrical energy to current-
using equipment, regardless of whether the energy comes from Distribution System Operator
(DSO) or local generation. IEC 60364-8-82 provides requirements and recommendations for to
low-voltage electrical installations, whether or not they are connected to a distribution network,
and are capable of operating:
– with either local power supplies,
– or with local storage units,
– or with both,
and that monitors and controls the energy from the locally connected sources delivering it to:
– either current-using equipment,
– or local storage units,
– or distribution networks.
Such electrical installations are designated as prosumer's electrical installations (PEIs) by
IEC 60364-8-82 which defines specific devices (or functions) to ensure the correct and safe
operation of PEI depending on their operating mode. In the case of an islandable PEI,
IEC 60364-8-82 defines a "Switching Device For islanding (SDFI)", identified as device 4 in
Figure 1.
IEC 63552:2026 © IEC 2026
Key
1 Distribution network 8 Non-sheddable loads (sensitive loads)
2 Point of connection (POC) 9 Sheddable loads (adjustable loads)
3 Main switching device 10 Solar generator
4 Switching device for islanding (SDFI) 11 Electrical energy storage system
5 System referencing conductor switching device 12 Other generator (wind, etc.)
6 Source switching device 13 Main distribution board
7 Load switching device
SOURCE: IEC 60364-8-82:2022, Figure 4.
Figure 1 – Example of islandable PEI architecture
The objectives of this document is to define the functions, requirements and tests of a SDFI in
line with the requirements stated in IEC 60364-8-82.

IEC 63552:2026 © IEC 2026
1 Scope
This document applies to switching device for islanding, hereafter referred to as SDFI, for
household and similar uses, primarily intended to be used for energy efficiency (EE) purposes
with local production or local storage of energy, or with both.
SDFI are intended to be installed in low voltage prosumer electrical installations (PEI) able to
operate in island mode as defined in IEC 60364-8-82, so called islandable PEI.
SDFI are used to disconnect the PEI from the grid to allow operating the PEI in island mode
and further reconnect the PEI to the grid.
They are intended to be used in islandable PEI which operate:
– in connected mode (direct feeding mode or reverse feeding mode), and
– in island mode,
as defined in IEC 60364-8-82.
NOTE 1 See definitions 3.10 and 3.13 of island mode and for connected mode respectively.
NOTE 2 Switching of a PEI to island mode can be subject to local regulations (grid codes) or to specific agreement
with system operators. Reverse feeding is also usually subject to local regulations (grid codes).
SDFI are part of the electrical installation.
This document applies to SDFI for operation in AC single or multiphase main circuits with rated
voltages not exceeding 440 V AC, frequencies of 50 Hz, 60 Hz or 50/60 Hz. They are intended
to be used in installations with prospective short circuit currents not exceeding 25 000 A.
NOTE 3 DC operations are not covered by this edition and are kept under consideration for a future revision of this
document.
The SDFI is composed at least of one switching unit (SU) and a control unit (CU) to monitor its
switching operations from grid connected to island mode and reverse wise.
The SDFI can be provided with a communication interface for exchange with external systems
such as the Customer Energy Manager (CEM) defined in IEC 63402 series.
According to the intended use, the SDFI can be interlocked with a system referencing conductor
switching device (SRCSD) according to IEC 63445 or it can be integrated with a SRCSD in a
single unit.
NOTE 4 According to its intended use, the SDFI can also be used as an interface switch with the interface protection
(integrated or not). See 3.19 and 3.20.
SDFI are intended for use in circuits where protection against electrical shock and overcurrent
is provided according to installation rules for low voltage electrical installations, unless the SDFI
already contains such protective function. SDFI are not requested to provide isolation function
and overcurrent protection according to IEC 60364-8-82. However, the isolation function can
be provided by a SDFI fulfilling the requirements of the relevant product standards.
SDFI are installed by instructed persons (IEC 60050-195:2021, 195-04-02) or skilled persons
(IEC 60050-195:2021, 195-04-01). They are intended to be used by ordinary persons
(IEC 60005-195:2021, 195-04-03) and do not require maintenance.
It is important to note that the main overcurrent protective device of installations cannot be used
as a SDFI in single dwellings or similar islandable PEI (see Clause D.5 of IEC 60364-8-82:2022)
IEC 63552:2026 © IEC 2026
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 60364-8-82:2022, Low-voltage electrical installations - Part 8-82: Functional aspects -
Prosumer's low-voltage electrical installations
IEC 60669-2-4, Switches for household and similar fixed electrical installations - Part 2-4:
Particular requirements - Isolating switches
IEC 60898-1:2015, Electrical accessories - Circuit-breakers for overcurrent protection for
household and similar installations - Part 1: Circuit-breakers for a.c. operation
IEC 60898-2, Electrical accessories - Circuit-breakers for overcurrent protection for household
and similar installations - Part 2: Circuit-breakers for AC and DC operation
IEC 60947-2, 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 60947-10, Low-voltage switchgear and controlgear - Part 10: Semiconductor circuit-
breakers
IEC 61000-4-2, Electromagnetic compatibility (EMC) - Part 4-2: Testing and measurement
techniques - Electrostatic discharge immunity test
IEC 61000-4-3, Electromagnetic compatibility (EMC) - Part 4-3: Testing and measurement
techniques - Radiated, radio-frequency, electromagnetic field immunity test
IEC 61000-4-4, Electromagnetic compatibility (EMC) - Part 4-4: Testing and measurement
techniques - Electrical fast transient/burst immunity test
IEC 61000-4-5, Electromagnetic compatibility (EMC) - Part 4-5: Testing and measurement
techniques - Surge immunity test
IEC 61000-4-6, Electromagnetic compatibility (EMC) - Part 4-6: Testing and measurement
techniques - Immunity to conducted disturbances, induced by radio-frequency fields
IEC 61000-4-8, Electromagnetic compatibility (EMC) - Part 4-8: Testing and measurement
techniques - Power frequency magnetic field immunity test
IEC 61000-4-11, Electromagnetic compatibility (EMC) - Part 4-11: Testing and measurement
techniques - Voltage dips, short interruptions and voltage variations immunity tests for
equipment with input current up to 16 A per phase
IEC 61000-6-1, Electromagnetic compatibility (EMC) - Part 6-1: Generic standards - Immunity
standard for residential, commercial and light-industrial environments
___________
Under preparation. Stage at the time of publication: IEC FDIS 60947-10:2025.
IEC 63552:2026 © IEC 2026
IEC 62991:2022, Particular requirements for source switching equipment (SSE)
IEC 63445:2025, System referencing conductor switching device
CISPR 14-1, Electromagnetic compatibility - Requirements for household appliances, electric
tools and similar apparatus - Part 1: Emission
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
– IEC Electropedia: available at https://www.electropedia.org/
– ISO Online browsing platform: available at https://www.iso.org/obp
3.1
electrical energy management system
EEMS
system monitoring, operating, controlling and managing energy resources and loads of the
installations
Note 1 to entry: The EEMS can be a dedicated system or part of an integrated system, such as a home and building
electronic system (HBES) or building management system (BMS or BACS) or other similar management system.
[SOURCE: IEC 60364-8-82:2022, 82.3.7]
3.2
Customer Energy Manager
CEM
internal automation function for optimizing the energy consumption, production and storage
within the premises according to the preferences of the customer using internal flexibilities and
typically based on external information received through the Energy Management Gateway and
possibly other data sources
Note 1 to entry: A EEMS as defined in 3.1 of this document and in 3.2.1 of IEC 60364-8-1:2019 provides the same
function as a CEMS except that the EEMS is limited to electrical energy management.
[SOURCE: IEC 63402-1:2025, 3.1.1, modified – Note 1 to entry added.]
3.3
Energy Management Gateway
EMG
access point (functional entity) sending and receiving smart grid related information and
commands between an actor in the grid and the CEM, letting the CEM decide how to process
the events
Note 1 to entry: The communication is often ensured through an internet connection.
[SOURCE: IEC 63402-1:2025, 3.1.3]
IEC 63552:2026 © IEC 2026
3.4
switching device for islanding
SDFI
device dedicated to the change from grid connected mode to island mode and from island mode
to connected mode for an islandable PEI, functionally speaking, to separate/link the local
sources from/to the distribution network
Note 1 to entry: See also 3.20.
[SOURCE: IEC 60364-8-82:2022, 1st paragraph of 82.6.3.4.3]
3.5
system referencing conductor switching devices
SRCSD
device connected between the system referencing conductor and the local earthing
arrangement of the PEI
[SOURCE: IEC 63445:2025, 3.3]
3.6
source switching equipment
SSE
equipment able to select (power) sources when certain conditions are met or following human
intervention
Note 1 to entry: For example, SSE for back-up applications may contain one or more switching devices and all
associated control means for disconnecting load circuits from one source and reconnecting them to another source
when certain conditions are met.
Note 2 to entry: For example, SSE for grid connected PEI defined in IEC 60364-8-82:2022 may contain one or more
switching devices and associated control means for switching load circuits from one normal source to another source,
when certain conditions are met, maintaining the loads always energized.
[SOURCE: IEC 62991:2022, 3.1.28]
3.7
prosumer
entity or party which can be both a producer and a consumer of electrical energy
[SOURCE: IEC 60364-8-82:2022, 82.3.5]
3.8
prosumer's electrical installation
PEI
low-voltage electrical installation connected or not to a distribution network able to operate:
– with local power supplies, and/or
– with local storage units,
and that monitors and controls the energy from the connected sources delivering it to:
– current-using equipment, and/or
– local storage units, and/or
– distribution network.
[SOURCE: IEC 60364-8-82:2022, 82.3.6]
IEC 63552:2026 © IEC 2026
3.9
islandable PEI
PEI intended for operating either being connected to a distribution network or being
disconnected from the distribution network
Note 1 to entry: An islandable PEI is in a connected mode or an intentionally island mode.
[SOURCE: IEC 60364-8-82:2022, 82.3.15]
3.10
island mode
operating mode in which the PEI is disconnected from the distribution network
Note 1 to entry: An island mode can be either the result of the action of automatic protections or the result of a
deliberate action.
[SOURCE: IEC 60050-692:2017, 692-02-11, modified – The term "electric island" has been
replaced with "island mode", the definition has been adapted to the PEI and Note 2 to entry has
been deleted.]
3.11
direct feeding mode
operating mode in which the distribution network supplies the PEI
Note 1 to entry: Local storage units can supply current-using equipment or be charged by local power supplies
and/or the distribution system.
[SOURCE: IEC 60364-8-82:2022, 82.3.9]
3.12
reverse feeding mode
operating mode in which the PEI supplies the distribution network
Note 1 to entry: Local storage units can supply current-using equipment and/or the distribution system or be
charged by local power supplies.
[SOURCE: IEC 60364-8-82:2022, 82.3.10]
3.13
connected mode
operating mode in which the PEI is connected to the distribution network
EXAMPLE Direct feeding mode, reverse feeding mode or no feeding mode (i.e. without any energy exchange
between the PEI and the distribution network).
[SOURCE: IEC 60364-8-82:2022, 82.3.11]
3.14
interlock
means to prevent simultaneous closing of SRCSD and SDFI,
under all conditions
[SOURCE: IEC 63445:2025, 3.11]
IEC 63552:2026 © IEC 2026
3.15
synchronization
condition of an electrical system intentionally allowing the connection of two voltage sources in
parallel for a short duration
Note 1 to entry: The local power source when set in grid forming mode is a voltage source.
[SOURCE: IEC 62991:2022, 3.1.17, modified – Replacing "different power" with "voltage",
addition of "condition of an" in the definition and addition of Note 1 to entry.]
3.16
open transition
break before make transfer operation that intentionally breaks the load current from one source
for a period of time prior to making it to the other source
Note 1 to entry: SSE with open transition may operate with a time delay e.g. for power backup application.
[SOURCE: IEC 60947-6-1:2021, 3.4.7, modified – Note 1 to entry has been added.]
3.17
closed transition
make before break transfer operation that intentionally makes the load current of a second
synchronized source for a short period of time before breaking it from the first source
[SOURCE: IEC 60947-6-1:2021, 3.4.9]
3.18
isolation
isolating function
function intended to cut off the supply from all or a discrete section of the installation by
separating the installation from every source of electrical energy for reasons of safety
[SOURCE: IEC 60898-1:2015, 3.6.10]
3.19
interface protection
combination of protection relay functions which open the interface switch of a generating unit
and prevents its closure, whichever is appropriate, in the case of:
– a fault on the electric power distribution network;
– an unintentional islanding situation;
– voltage and/or frequency being outside the tolerance of their operating ranges for
continuous operation.
[SOURCE: IEC TS 62786-1:2023, 3.1.14, modified - "distribution" added in the first indent.]
3.20
interface switch
switch (circuit breaker, switch or contactor) installed in the prosumer's electrical installation, for
separating the part(s) of the prosumer's electrical installation that contains at least one
generation unit from the network
Note 1 to entry: See also Figure 1 of IEC TS 62786-1:2023.
Note 2 to entry: In some situations, the interface switch can be used to enable island operation of part of the
prosumer's electrical installation, if technically feasible.
[SOURCE: IEC TS 62786-1:2023, 3.1.33, modified - Reference to the IEC standard adding and
replaced "producer's network" by "prosumer's electrical installation".]
IEC 63552:2026 © IEC 2026
3.21
voltage source deviation
change in voltage level from the nominal voltage of the monitored source
Note 1 to entry: In this document, the term is often used stating only the term "source deviation".
[SOURCE: IEC 60947-6-1:2021, 3.4.3, modified – Replacing "supply" by "source" and adding
the note.]
3.22
frequency source deviation
change in frequency from the nominal operating frequency of the monitored source
Note 1 to entry: In this document, the term is often used stating only the term "source".
[SOURCE: IEC 60947-6-1:2021, 3.4.4, modified – Replacing "supply" by "source" and adding
the note.]
3.23
point of connection
POC
reference point where the prosumer's electrical installation is connected to the distribution
network
Note 1 to entry: A PEI can have several points of connection for resilience.
Note 2 to entry: In IEC 60364 (all parts), the concept of origin of the installation is also used, origin of the installation
meaning the point at which energy is delivered to the electrical installation. The POC is a specific origin of the
installation, the one connected to the distribution network. Other origins of the installation can be the connection to
the local power supply, to the storage system.
Note 3 to entry: Connection or disconnection of the prosumer electrical installation from the distribution network
generally occurs at the POC.
[SOURCE: IEC 60050-617:2009, 617-04-01 modified – The definition has been adapted to the
PEI and the notes to entry have been added.]
3.24
control unit
all part(s) intended for managing the operation(s) of the switching unit (of the
SDFI) including the operating means
Note 1 to entry: Depending on the type of SDFI, the control unit may include different features such as manual
operating means, sensing, interlock, synchronization, control of settings, etc. For the purposes of this document,
control means do not include means intended for purposes other than controls, e.g. local or remote signalling.
[SOURCE: IEC 62991:2020, 3.1.35, modified – replacing "SSE" by "SDFI" in the definition and
in the note, and removing notes 2, 3 and 4.]
4 Classification
4.1 General
The architecture of the SDFI is shown Figure 2.
IEC 63552:2026 © IEC 2026
Key
1 Switching device for islanding (SDFI) 6 Electrical Energy Management (EEM) or the
Customer Energy Manager (CEM)
2 Control unit (CU)
7 Grid
3 Switching unit (SU)
8 Local source(s)
4 System referencing conductor switching device
(SRCSD) 9 Loads
5 Interlock (of the SRCSD with SDFI) 10 Earth

Figure 2 – Example of SDFI architecture
The control unit (CU) with or without sensing means (also called measurement circuits).
The sensing means can be part of the SDFI (e.g. part of the control unit) or the overall CEM
system (CEMS or EEMS).
According to this document, the CU is supposed to integrate control means for the operations
(e.g. synchronization check before reclosing) and the interlock with the SRCSD.
The control unit, sensing unit and any connecting accessories can be delivered assembled
together in the factory with the switching unit or assembled on site.
The switching unit (SU) allows the islanding and reconnecting operations in safe conditions as
requested in IEC 60364-8-82. This can require the interlocking with an SRCSD according to
IEC 60364-8-82.
The SDFI shall be classified according to 4.2 to 4.11.
4.2 According to the construction
SDFI with a switching unit (SU) based on:
– switches complying with the IEC 60669-2-4 or IEC 60947-3;
– circuit-breakers complying with IEC 60898-1, IEC 60898-2, IEC 60947-2 or IEC 60947-10.
4.3 According to the method of integration of SRCSD
– SDFI with the SRCSD not integrated in a single device;
– SDFI with the SRCSD integrated in a single device.
NOTE SDFI can be based on separate devices or with all devices assembled together into a single device but with
the switching unit based on 4.2. See Figure 2.
IEC 63552:2026 © IEC 2026
4.4 According to the method of operation
– electrically controlled: SDFI with an integrated control unit (CU) for managing its switching
operations. This may or may not include automatic islanding function upon voltage or
frequency deviations;
– manually (non-electrically) controlled;
– or both electrically controlled and manually (non-electrically) controlled.
When manual mode is available and if the SDFI is used as the interface switch, it shall be
ensured that the manual mode does not prevent the SDFI from opening upon orders received
from the interface protection.
NOTE The SDFI can also have communication interfaces for SDFI remotely controlled by the CEM.
4.5 According to kind of current
– for AC use;
– for DC use (under consideration).
4.6 According to the number of switched poles
– two-pole SDFI;
– three-pole SDFI;
– four-pole SDFI.
4.7 According to SRCSD interlocking means
– SDFI without interlocking;
– SDFI with mechanical or electrical interlocking means.
NOTE When the SDFI is integrated with the SRCSD according to 4.1 in a single device, the interlock is also
integrated.
4.8 According to the reclosing mode
– SDFI without synchronization (open transition);
– SDFI with synchronized reclosing (closed transition).
4.9 According to islanding means
– SDFI without automatic islanding means;
– SDFI with automatic islanding means.
NOTE Operation of the SDFI with automatic islanding means is based on voltage and frequency source deviations.
4.10 According to the type of isolation
– SDFI not suitable for isolation;
– SDFI suitable for isolation.
NOTE IEC 60364-8-82:2022 does not require isolation for the SDFI.
4.11 According to the type of local sources
– SDFI suitable for use with inverter-based sources only (i.e. excluding generators);
– SDFI suitable for use with any kind of local sources including generators.
IEC 63552:2026 © IEC 2026
5 Characteristics
The characteristics of the switching unit of an SDFI are covered by:
– IEC 60669-2-4 or IEC 60947-3 for SDFI based on switches;
– IEC 60898-1, IEC 60898-2, IEC 60947-2 or IEC 60947-10 for SDFI based on circuit-
breakers.
The characteristics of the control unit and auxiliary circuits are covered by IEC 62991:2022,
5.4.
In addition, the following characteristics apply to the control unit and auxiliary circuits:
– the voltage and frequency deviation limits;
– the characteristics of control circuits and auxiliary circuits (e.g. rated voltage and currents,
limits) if any.
The maximum number of operating cycles shall be declared. The preferred number of operating
cycles is: 4 000, 6 000, 12 000 and 25 000, where 4 000 is the requested minimum value.
6 Markings and product information
Identification of the SDFI shall comply with relevant IEC product standards according to
manufacturer's declaration based on Clause 4 and relevant items of Table 1.
Table 1 – Requirements and position for markings and other product information
a a a
Marking or information item Markings Documentation
b
a Manuf
...