SIST EN IEC 62991:2025

Particular requirements for source switching equipment (SSE) (IEC 62991:2022)

This International Standard applies to Source Switching Equipment, hereafter referred to as SSE(s), for household and similar uses, primarily intended to be used for Energy Efficiency purposes with local production and/or storage of energy.
This standard has been drafted following principles of:
- IEC guides 118 and 119 for Energy Efficiency;
- IEC guide 110 for safety.
SSEs are intended to be installed in low voltage prosumer electrical installations (PEI) to deliver the electrical energy:
- either to current-using equipment (direct feeding mode or island mode);
- or to the grid (reverse feeding mode).
SSEs are intended to select and/or combine two power sources (e.g. selected among grid, local power source, storage units) within an Electrical Energy Management system (EEMS). SSEs may also be used for backup supply.
NOTE SSEs capable to select more than two sources are under consideration.
SSEs are part of the fixed electrical installation.
This standard applies to SSEs for operation in:
- AC single or multiphase circuits with rated voltages not exceeding 440 V AC, frequencies of 50 Hz, 60 Hz or 50/60 Hz and rated currents not exceeding 125 A. They are intended to be used in installations with prospective short circuit current not exceeding 25 000 A, or
- DC circuits. SSE for DC circuits are under consideration (next edition).
SSEs may be operated:
- manually (M-SSE), or
- remotely (R-SSE), or
- automatically (A-SSE), or
- a combination of the above methods of operation, e.g. manual and remote.
SSEs are constructed either as Combined-SSEs (C-SSEs, based on dedicated products suc as circuit breakers, switches or contactors) or Non-Combined SSEs (NC-SSEs).
SSEs are intended for use in circuits where protection against electrical shock and over-current according to IEC 60364 is provided, unless the SSE already contains such protective function.
SSEs are normally installed by instructed persons (IEC 60050-195:1998, 195-04-02) or skilled persons (IEC 60050-195:1998, 195-04-01). SSEs are normally used by ordinary persons (IEC 60005-195:1998, 195-04-03) and do not require maintenance.
The requirements of this standard apply for standard environmental 420 conditions as given in clause 7. They are applicable to SSEs intended for use in an environment with pollution degree 2 and overvoltage categories III according to IEC 60664-1:2020. SSEs have at least a degree of protection IP 20 according to IEC 60529. Additional requirements may be necessary for devices used in locations having more severe environmental conditions.
SSEs do not, by their nature, provide an isolation function nor the overcurrent protection. However, isolation and overcurrent protection functions as covered by relevant product standards may be provided by Combined SSEs.
In some countries, it is not permitted to have synchronization of local sources with the grid for particular grid conditions, e.g. when fluctuations of the grid voltage or frequency are outside the tolerance limits.
This document does not apply to transfer switching equipment (TSE) intended to be used by skilled persons, as covered by IEC 60947-6-1:2021.

Besondere Anforderungen an Quellenumschalteinrichtungen (SSE) (IEC 62991:2022)

Exigences particulières relatives au matériel de commutation de source (SSE) (IEC 62991:2022)

L'IEC 62291:2022 s'applique au matériel de commutation de source, ci-après dénommé "SSE", destiné à un usage domestique ou analogue, essentiellement prévu pour être utilisé pour les besoins de l'efficacité énergétique (EE) avec la production locale et/ou le stockage local de l'énergie.
Le SSE est destiné à être installé dans des installations électriques de prosommateurs (PEI - prosumer electrical installation) à basse tension pour délivrer l'énergie électrique:

   
• au matériel d'utilisation (mode d'alimentation directe ou mode en réseau séparé);

   
• ou au réseau (mode d'alimentation inverse).

Posebne zahteve za opremo za preklapljanje virov (SSE) (IEC 62991:2022)

Ta mednarodni standard se uporablja za opremo za preklapljanje virov (v nadaljevanju: »oprema SSE«), namenjeno za gospodinjstvo in podobne načine uporabe, ki je namenjena predvsem za izboljšanje energetske učinkovitosti z lokalno proizvodnjo in/ali shranjevanjem energije. Ta standard je bil pripravljen po načelih: – vodil IEC 118 in 119 za energetsko učinkovitost; – vodila IEC 110 za varnost. Oprema SSE je namenjena namestitvi v nizkonapetostne električne inštalacije aktivnih odjemalcev (PEI) za dovajanje električne energije: – opremi, ki porablja tok (način neposrednega napajanja ali način otočnega napajanja); ali – v omrežje (način povratnega napajanja). Oprema SSE je namenjena izbiri in/ali kombiniranju dveh virov energije (npr. izbranih med omrežjem, lokalnim virom napajanja, enotami za shranjevanje) znotraj sistema upravljanja z električno energijo (EEMS). Oprema SSE se lahko uporablja tudi za rezervno napajanje. OPOMBA: Oprema SSE, ki omogoča izbiro več kot dveh virov, je v obravnavi. Oprema SSE je del stalne električne inštalacije. Ta standard se uporablja za opremo SSE v: – enofaznih ali večfaznih izmeničnih tokokrogih z nazivno napetostjo, ki ne presega 440 V AC, frekvenco 50 Hz, 60 Hz ali 50/60 Hz in nazivnim tokom največ 125 A. Namenjena je za uporabo v inštalacijah s predvidenim kratkostičnim tokom, ki ne presega 25.000 A; ali – enosmernih tokokrogih. Oprema SSE za enosmerne tokokroge je v obravnavi (naslednja izdaja). Oprema SSE se lahko upravlja: – ročno (M-SSE); – daljinsko (R-SSE); – samodejno (A-SSE); – s kombinacijo teh načinov (npr. ročno in daljinsko). Oprema SSE je zasnovana kot kombinirana oprema SSE (C-SSE), ki temelji na namenskih izdelkih, kot so odklopniki, stikala ali kontaktorji, ali nekombinirana oprema SSE (NC-SSE). Oprema SSE je namenjena uporabi v tokokrogih, kjer je zagotovljena zaščita pred električnim udarom in prenapetostjo v skladu s standardom IEC 60364, razen če oprema SSE že vključuje takšno zaščitno funkcijo. Opremo SSE običajno namestijo poučene (IEC 60050-195:1998, 195-04-02) ali usposobljene osebe (IEC 60050-195:1998, 195-04-01). Opremo SSE običajno uporabljajo laiki (IEC 60005-195:1998, 195-04-03) in je ni potrebno vzdrževati. Zahteve tega standarda veljajo za standardne okoljske pogoje 420, navedene v točki 7. Uporabljajo se za opremo SSE, namenjeno uporabi v okolju s stopnjo onesnaženja 2 in prenapetostnimi kategorijami III v skladu s standardom IEC 60664-1:2020. Oprema SSE vključuje najmanj stopnjo zaščite IP 20 v skladu s standardom IEC 60529. Za naprave, ki se uporabljajo na lokacijah z bolj neugodnimi okoljskimi pogoji, so lahko potrebne dodatne zahteve. Oprema SSE sama po sebi ne zagotavlja izolacijske funkcije niti nadtokovne zaščite. Vendar pa lahko kombinirana oprema SSE zagotavlja izolacijo in nadtokovno zaščito, kot je zajeto v ustreznih standardih za izdelke. V nekaterih državah ni dovoljena sinhronizacija lokalnih virov z omrežjem za posebne pogoje omrežja, npr. kadar so nihanja omrežne napetosti ali frekvence zunaj meja dovoljenih odstopanj. Ta dokument se ne uporablja za opremo za samodejno predajanje stikanja (TSE), namenjeno uporabi s strani usposobljenih oseb, kot je zajeto v standardu IEC 60947-6-1:2021.

General Information

• Status: Published
• Public Enquiry End Date: 09-Sep-2021
• Publication Date: 11-Jun-2025
• ICS: 27.015 - Energy efficiency. Energy conservation in general
• ICS: 91.140.50 - Electricity supply systems
• Technical Committee: EPR - Electrical accessories
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 24-Apr-2025
• Due Date: 29-Jun-2025
• Completion Date: 12-Jun-2025
• Directive: 2014/30/EU - Directive 2014/30/EU of the European Parliament and of the Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to electromagnetic compatibility (recast)
• Directive: 2014/35/EU - Directive 2014/35/EU of the European Parliament and of the Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to the making available on the market of electrical equipment designed for use within certain voltage limits
• Mandate: M/511 - Mandate to CEN, CENELEC and ETSI relating to harmonised standards in the field of the Low Voltage Directive
• Mandate: M/552 - [C(2016) 7641 final] Standardisation request as regards harmonised standards in support of Directive 2014/30/EU of the European Parliament and of the Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to electromagnetic compatibility
• Ref Project: EN IEC 62991:2025 - Particular requirements for source switching equipment (SSE)

Overview

SIST EN IEC 62991:2025 (identical to EN IEC 62991:2025 / IEC 62991:2022) specifies particular requirements for Source Switching Equipment (SSE) for household and similar prosumer uses. The standard targets SSEs intended primarily for energy efficiency applications with local energy production and/or storage, installed as part of a low-voltage Prosumer Electrical Installation (PEI) or Electrical Energy Management System (EEMS). SSEs select and/or combine two power sources (e.g., grid, local generation, storage) to supply loads (direct/ island mode) or feed the grid (reverse feeding). SSEs are part of the fixed electrical installation and can be manual, remote, automatic, or combinations thereof.

Key technical topics and requirements

• Scope and application: SSEs for AC single- and multi-phase circuits up to 440 V AC, frequencies 50 Hz / 60 Hz / 50–60 Hz, and rated currents up to 125 A; intended for installations with prospective short-circuit current ≤ 25 000 A. DC SSEs are under consideration for future editions.
• Modes of operation: Manual (M‑SSE), Remote (R‑SSE), Automatic (A‑SSE), or combinations.
• Construction types: Combined-SSE (C‑SSE) - built from dedicated products (circuit breakers, switches, contactors) and Non-Combined SSE (NC‑SSE).
• Functional behavior: Supports direct feeding (island), reverse feeding to grid, and backup supply. Synchronization and interlock options are defined; synchronization with the grid may be restricted by local grid rules.
• Safety and environment: Drafted following IEC Guides for energy efficiency (118, 119) and safety (110). Designed for pollution degree 2, overvoltage category III, minimum protection degree IP20, and standard environmental conditions (clause 7).
• Limitations: SSEs do not inherently provide isolation or overcurrent protection unless integrated in C‑SSEs. The standard excludes transfer switching equipment (TSE) covered by IEC 60947‑6‑1.

Practical applications

• Residential and small commercial prosumer installations with solar PV, battery storage and energy management systems.
• Devices used to switch between grid and local sources for energy efficiency, demand management, backup power and controlled reverse feeding.
• Integration into smart home and microgrid systems where safe source selection and coordination are required.

Who should use this standard

• Manufacturers and designers of SSEs and related switching devices
• Electrical installers and system integrators for prosumer and low-voltage installations
• Test laboratories, product certifiers and conformity assessment bodies
• Energy managers, utilities and regulators assessing safe grid connection and reverse‑feeding practices

Related standards (selected)

Key referenced standards include IEC 60364 (low-voltage installations), IEC 60664‑1 (insulation coordination), IEC 60529 (IP codes), and EMC and safety standards cited in Annex ZA (e.g., IEC 61000 series, IEC 60695, IEC 60898). Compliance with SIST EN IEC 62991:2025 supports safe, energy-efficient SSE integration in prosumer installations.

Standards Content (Sample)

SLOVENSKI STANDARD
01-julij-2025
Posebne zahteve za opremo za preklapljanje virov (SSE) (IEC 62991:2022)
Particular requirements for source switching equipment (SSE) (IEC 62991:2022)
Besondere Anforderungen an Quellenumschalteinrichtungen (SSE) (IEC 62991:2022)
Exigences particulières relatives au matériel de commutation de source (SSE) (IEC
62991:2022)
Ta slovenski standard je istoveten z: EN IEC 62991:2025
ICS:
27.015 Energijska učinkovitost. Energy efficiency. Energy
Ohranjanje energije na conservation in general
splošno
91.140.50 Sistemi za oskrbo z elektriko Electricity supply systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 62991

NORME EUROPÉENNE
EUROPÄISCHE NORM April 2025
ICS 03.100.70; 27.015; 29.020
English Version
Particular requirements for source switching equipment (SSE)
(IEC 62991:2022)
Exigences particulières relatives au matériel de Besondere Anforderungen an
commutation de source (SSE) Quellenumschalteinrichtungen (SSE)
(IEC 62991:2022) (IEC 62991:2022)
This European Standard was approved by CENELEC on 2025-02-19. 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
© 2025 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 62991:2025 E
European foreword
The text of document 23K/78/FDIS, future edition 1 of IEC 62991, 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 62991:2025.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2026-04-30
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2028-04-30
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.
This document has been prepared under a standardization request addressed to CENELEC by the
European Commission. The Standing Committee of the EFTA States subsequently approves these
requests for its Member States.
For the relationship with EU Legislation, see informative Annex ZZ, which is an integral part of this
document.
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 62991:2022 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 60038 NOTE Approved as EN 60038
IEC 60112 NOTE Approved as EN IEC 60112
IEC 60364-4-41 NOTE Approved as HD 60364-4-41
IEC 60364-8-1:2019 NOTE Approved as HD 60364-8-1:2019 (not modified)
IEC 60529 NOTE Approved as EN 60529
IEC 60669-1:2017 NOTE Approved as EN 60669-1:2018
IEC 60947-1:2020 NOTE Approved as EN IEC 60947-1:2021 (not modified)
IEC 60947-4-1:2018 NOTE Approved as EN IEC 60947-4-1:2019 (not modified)
IEC 60947-6-1:2021 NOTE Approved as EN IEC 60947-6-1:2023 (not modified)
IEC 61000-6-1 NOTE Approved as EN IEC 61000-6-1
IEC 61140 NOTE Approved as EN 61140
IEC 62019 NOTE Approved as EN 62019
IEC 62933-1:2018 NOTE Approved as EN IEC 62933-1:2018 (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 60068-2-78 - Environmental testing – Part 2-78: EN 60068-2-78 2013
Tests – Test Cab: Damp heat, steady
state
IEC 60085 - Electrical insulation – Thermal EN 60085 2008
evaluation and designation
IEC 60127-1 - Miniature fuses – Part 1: Definitions EN IEC 60127-1 2024
for miniature fuses and general

requirements for miniature fuse-links

IEC 60212 - Standard conditions for use prior to EN 60212 2011
and during the testing of solid
electrical insulating materials
IEC 60228 - Conductors of insulated cables EN IEC 60228 2024

IEC 60317-0-1 2013 Specifications for particular types of EN 60317-0-1 2014
winding wires - Part 0-1: General
+ A1 2019
requirements - Enamelled round
copper wire
IEC 60364-8-82 2022 Low voltage electrical installations- - -
Part 8-82: Prosumer’s low-voltage
electrical installations
IEC 60384-14 2013 Fixed capacitors for use in electronic EN 60384-14 2013
equipment – Part 14: Sectional
+ A1 2016 + A1 2016
specification – Fixed capacitors for
+ AC 2016
electromagnetic interference
suppression and connection to the
supply mains
Dated as no EN equivalent exists.
Publication Year Title EN/HD Year
IEC 60417 database Graphical symbols for use on - -
equipment (available at
http://www.graphical-
symbols.info/equipment)
IEC 60664-1 2020 Insulation coordination for equipment EN IEC 60664-1 2020
within low-voltage systems - Part 1:
+ AC 2020-12
Principles, requirements and tests
IEC 60664-3 - Insulation coordination for equipment EN 60664-3 2017
within low-votage systems - Part 3:
Use of coating, potting or moulding for
protection against pollution
IEC 60669 series Switches for household and similar EN 60669-1 2018
fixed-electrical installations
+ AC 2018-11
+ AC 2020-02
EN IEC 60669-2-1 2022
+ A11 2022
+ AC 2024-01
EN 60669-2-2 2006
EN 60669-2-3 2006
EN 60669-2-4 2005
EN 60669-2-5 2016
EN 60669-2-6 2012
IEC 60695-2-10 - Fire hazard testing - Part 2-10: EN IEC 60695-2-10 2021
Glowing/hot-wire based test methods -
+ AC 2024-01
Glow-wire apparatus and common test
procedure
IEC 60695-2-11 2021 Fire hazard testing – Part 2-11: EN IEC 60695-2-11 2021
Glowing/hot-wire based test methods
– Glow-wire flammability test method
for end-products (GWEPT)
IEC 60898-1 - Electrical accessories - Circuit- EN 60898-1 2019
breakers for overcurrent protection for

household and similar installations -

Part 1: Circuit-breakers for a.c.
operation
IEC 60898-2 - Electrical accessories - Circuit- EN 60898-2 2021
breakers for overcurrent protection for

household and similar installations -
Part 2: Circuit-breakers for AC and DC
operation
IEC 61000-4-2 - Electromagnetic compatibility (EMC) - EN 61000-4-2 2009
Part 4-2: Testing and measurement
techniques - Electrostatic discharge
immunity test
IEC 61000-4-3 - Electromagnetic compatibility (EMC) - EN IEC 61000-4-3 2020
Part 4-3: Testing and measurement
techniques - Radiated, radio-
frequency, electromagnetic field
immunity test
Publication Year Title EN/HD Year
IEC 61000-4-4 - Electromagnetic compatibility (EMC) - EN 61000-4-4 2012
Part 4-4: Testing and measurement
techniques - Electrical fast
transient/burst immunity test
IEC 61000-4-5 - Electromagnetic compatibility (EMC) - EN 61000-4-5 2014
Part 4-5: Testing and measurement
+ A1 2017
techniques - Surge immunity test
IEC 61000-4-6 - Electromagnetic compatibility (EMC) - EN IEC 61000-4-6 2023
Part 4-6: Testing and measurement
techniques - Immunity to conducted
disturbances, induced by radio-
frequency fields
IEC 61000-4-8 - Electromagnetic compatibility (EMC) - EN 61000-4-8 2010
Part 4-8: Testing and measurement
techniques - Power frequency
magnetic field immunity test
IEC 61000-4-11 - Electromagnetic compatibility (EMC) - EN IEC 61000-4-11 2020
Part 4-11: Testing and measurement
+ AC 2020-06
techniques - Voltage dips, short
+ AC 2022-10
interruptions and voltage variations
immunity tests
IEC 61032 1997 Protection of persons and equipment EN 61032 1998
by enclosures - Probes for verification
IEC 61095 2009 Electromechanical contactors for EN 61095 2009
household and similar purposes
IEC 61558-2-6 - Safety of transformers, reactors, EN 61558-2-6 2009
power supply units and similar
products for supply voltages up to
1 100 V - Part 2-6: Particular
requirements and tests for safety
isolating transformers and power
supply units incorporating safety
isolating transformers
IEC 62873-3-1 2020 Residual current operated circuit- - -
breakers for household and similar
use - Part 3-1: Particular requirements
for devices with screwless-type
terminals for external copper
conductors
IEC 62873-3-3 2022 Residual current operated circuit- - -
breakers for household and similar
use - Part 3-3: Specific requirements
for devices with screw-type terminals
for external untreated aluminium
conductors and with aluminium screw-
type terminals for use with copper or
with aluminium conductors
Dated as no EN equivalent exists.
Dated as no EN equivalent exists.
Publication Year Title EN/HD Year
CISPR 14-1 2020 Electromagnetic compatibility – EN IEC 55014-1 2021
Requirements for household
appliances, electric tools and similar
apparatus - Part 1: Emission
equipment
ISO 306 - Plastics – Thermoplastic materials – EN ISO 306 2022
Determination of Vicat softening
temperature (VST)
Annex ZZ
(informative)
Relationship between this European standard and the safety
objectives of Directive 2014/35/EU [2014 OJ L96] aimed to be
covered
This European standard has been prepared under a Commission’s standardisation request relating to
harmonised standards in the field of the Low Voltage Directive, M/511, to provide one voluntary means
of conforming to safety objectives of Directive 2014/35/EU of the European Parliament and of the
Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to the
making available on the market of electrical equipment designed for use within certain voltage limits
[2014 OJ L96].
Once this standard is cited in the Official Journal of the European Union under that Directive,
compliance with the normative clauses of this standard given in Table ZZ.1 confers, within the limits of
the scope of this standard, a presumption of conformity with the corresponding safety objectives of
that Directive, and associated EFTA regulations.
Table ZZ.1 — Correspondence between this European standard and Annex I of Directive
2014/35/EU [2014 OJ L96]
Clause(s) / subclause(s)
Safety Objectives of Directive
Remarks / Notes
2014/35/EU
of this EN
(1) (a) 4, 5, 6 - 9.2
(1) (b) 4 - Annex D, 5, 8.1 - 9.1, 8.2.2 -
9.3, 8.2.3 - 9.11, 8.2.5 - 9.5,
8.2.6 - 9.6, 8.7.2.2 - 9.11.2
(1) (c) 7, 8.1 - 9.1
(2) (a), (b), (c) and (d) 8.2.2 - 9.3, 8.2.3 - 9.11, 8.2.4 -
9.4, 8.3 - 9.7, 8.4 - 9.8, 8.5 - 9.9,
8.6 - 9.10, 8.7 - 9.11, 8.11 -
9.15, 8.12 - 9.16.2, 9.1 - Annex
D
(3) (a), (b) and (c) 8.2.2 - 9.3, 8.4 - 9.8, 8.7 - 9.11,
8.8 - 9.12, 8.9 - 9.13, 8.10 -
9.14, 8.11 - 9.15, 8.12 - 9.16.3,
8.13 - 9.17
WARNING 1 — Presumption of conformity stays valid only as long as a reference to this European
standard is maintained in the list published in the Official Journal of the European Union. Users of this
standard should consult frequently the latest list published in the Official Journal of the European
Union.
WARNING 2 — Other Union legislation may be applicable to the product(s) falling within the scope of
this standard.
IEC 62991 ®
Edition 1.0 2022-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Particular requirements for source switching equipment (SSE)

Exigences particulières relatives au matériel de commutation de source (SSE)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 03.100.70; 27.015; 29.020 ISBN 978-2-8322-6198-9

– 2 – IEC 62991:2022 © IEC 2022
CONTENTS
FOREWORD . 8
INTRODUCTION . 10
1 Scope . 12
2 Normative references . 13
3 Terms and definitions . 15
3.1 General definitions . 15
3.2 Additional definitions for NC-SSE and SSE control units (controllers) of
C-SSE . 25
3.3 Additional definitions dedicated to C-SSE . 26
4 Classification . 27
4.1 According to the method of operation . 27
4.2 According to the construction . 27
4.3 According to the kind of current . 28
4.4 According to the number of switched poles . 28
4.5 According to the type of terminals . 28
4.6 According to the SSE's intended application . 28
4.7 According to coupling method . 28
4.7.1 SSE with synchronization . 28
4.7.2 SSE with interlock . 28
4.7.3 SSE with synchronization and interlock . 28
4.8 According to the transition type . 28
4.9 According to the possibility to select sources . 28
4.10 According to the utilization category . 28
4.11 According to the possibility to provide an OFF position . 28
4.12 According to the method of mounting . 29
4.13 According to the protection against external influences . 29
4.14 According to functional categories . 29
5 Characteristics . 31
5.1 General . 31
5.2 Type and characteristics of the equipment . 32
5.3 Characteristics of NC-SSE . 32
5.3.1 General . 32
5.3.2 Characteristics of main circuits . 32
5.3.3 Utilization categories . 35
5.3.4 Characteristics of control circuits, including electrical interlocks . 35
5.3.5 Characteristics of auxiliary circuits . 37
5.4 Characteristics of C-SSE . 37
5.4.1 General . 37
5.4.2 Characteristics of main circuits . 37
5.4.3 Utilization categories . 38
5.4.4 Characteristics of control circuits, including electrical interlocks . 38
5.4.5 Characteristics of auxiliary circuits . 39
6 Markings and product information . 39
7 Standard conditions for operation in service . 40
7.1 General . 40
7.2 Ambient temperature range in normal use . 41

IEC 62991:2022 © IEC 2022 – 3 –
7.3 Relative humidity . 41
7.4 Altitude . 41
7.5 Conditions of installation . 41
7.6 Pollution degree . 41
8 Requirements for construction and operation . 41
8.1 General . 41
8.2 Mechanical design . 42
8.2.1 General . 42
8.2.2 Constructional requirements . 42
8.2.3 Mechanism and operating means. 44
8.2.4 Clearances and creepage distances and distances through sealing
compound . 46
8.2.5 Screws, current-carrying parts and connections . 49
8.2.6 Terminals for external conductors . 50
8.3 Protection against electric shock . 52
8.4 Dielectric properties . 52
8.4.1 General . 52
8.4.2 Dielectric properties . 52
8.5 Temperature-rise . 52
8.6 Making and breaking capacity . 53
8.7 Performances . 54
8.7.1 General . 54
8.7.2 Operating conditions . 55
8.7.3 Operational performance . 57
8.8 Resistance to heat . 58
8.9 Resistance of insulating material to abnormal heat and to fire . 58
8.10 Resistance to rusting . 59
8.11 Coordination with short-circuit protective devices (SCPDs) . 59
8.12 EMC . 59
8.13 Resistance to abnormal conditions . 59
8.14 Components . 59
8.14.1 General . 59
8.14.2 Fuses . 60
8.14.3 Capacitors . 60
8.14.4 Resistors . 61
8.14.5 Transformers . 61
9 Type tests . 61
9.1 General requirements . 61
9.1.1 Type tests and test sequences . 61
9.1.2 Test conditions . 61
9.1.3 Test procedure . 63
9.2 Tests of indelibility of markings . 63
9.3 Tests of the mechanical strength . 63
9.3.1 Tests of the resistance to mechanical stresses of insulating means . 63
9.3.2 Verification of installation and connections . 73
9.3.3 Tests of fixings of covers, cover plates and actuating members . 75
9.3.4 Tests of attachment of knobs . 76
9.3.5 Tests of covers, cover plates or actuating members – Accessibility to
live parts. 77

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9.3.6 Tests of covers, cover plates or actuating members – Accessibility to
non-earthed metal parts separated from live parts . 78
9.3.7 Tests of covers, cover plates or actuating members – Accessibility to
insulating parts, earthed metal parts, the live parts of SELV ≤ 25 V AC
or metal parts separated from live parts . 78
9.3.8 Tests of covers, cover plates or actuating members – Application of
gauges . 78
9.3.9 Tests of grooves, holes and reverse tapers. 80
9.4 Measurements of clearances and creepage distances. 81
9.5 Test of reliability of screws, current-carrying parts and connections . 82
9.6 Test of reliability of screw-type terminals for external copper conductors . 82
9.7 Tests for the protection against electric shock . 84
9.8 Tests of dielectric properties . 86
9.8.1 General . 86
9.8.2 Tests of the resistance to humidity. 87
9.8.3 Tests of the insulation resistance of the main circuits . 87
9.8.4 Tests of the dielectric strength of main circuits . 88
9.8.5 Tests of the insulation resistance and dielectric strength of other circuits . 90
9.8.6 Verification of impulse withstand voltages (across clearances and
through solid insulations) . 91
9.9 Tests of temperature-rise . 92
9.9.1 General . 92
9.9.2 Test setup . 92
9.9.3 Test procedure . 94
9.10 Tests of making and breaking capacity . 94
9.11 Verification of performances . 95
9.11.1 General . 95
9.11.2 Verification of interlocking function . 95
9.11.3 Verification of controls, sequences and limits of operations . 98
9.11.4 Verification of the operational performance capability . 102
9.12 Tests of heat resistance . 103
9.12.1 Basic heating test . 103
9.12.2 Ball-pressure test on parts of insulating material necessary to retain
current-carrying parts and parts of the earthing circuit in position . 104
9.12.3 Ball-pressure test on parts of insulating material not necessary to retain

current-carrying parts and parts of the earthing circuit in position . 104
9.13 Tests of the resistance of insulating material to abnormal heat and to fire . 104
9.14 Resistance to rusting . 106
9.15 Tests of coordination with short-circuit protective devices (SCPDs) . 107
9.15.1 General . 107
9.15.2 Test conditions . 107
9.15.3 Tests of coordination between the SSE and the SCPDs . 112
9.16 EMC tests . 113
9.16.1 General . 113
9.16.2 Electromagnetic emission . 113
9.16.3 Electromagnetic immunity . 113
9.17 Tests under abnormal conditions . 117
9.17.1 General . 117
9.17.2 Tests under fault conditions . 119
9.17.3 Overload tests . 121

IEC 62991:2022 © IEC 2022 – 5 –
9.18 Tests of components . 121
Annex A (informative) Examples of possible use of SSE . 125
A.1 General concept of prosumer's low-voltage electrical installation . 125
A.2 Examples of SSE use . 128
Annex B (informative) Correspondence between ISO and AWG copper conductors . 133
Annex C (normative) Determination of clearances and creepage distances . 134
C.1 General . 134
C.2 Orientation and location of a creepage distance . 134
C.3 Creepage distances where more than one material is used . 134
C.4 Creepage distances split by floating conductive part . 134
C.5 Measurement of creepage distances and clearances . 134
Annex D (normative) Test sequences and number of specimens . 137
Annex E (normative) Arrangement for the detection of the emission of ionized gases
during short-circuit tests . 139
Bibliography . 142

Figure 1 – Energy efficiency management system (EEMS). 10
Figure 2 – Principle of management of two sources with source switching equipment
(SSE) . 11
Figure 3 – Example of A-SSE . 30
Figure 4 – Example of R-SSE . 31
Figure 5 – Example of M-SSE . 31
Figure 6 – Pendulum impact test apparatus . 65
Figure 7 – Pendulum impact test apparatus (striking element) . 66
Figure 8 – Mounting support of specimens . 67
Figure 9 – Mounting block for a flush type SSE . 68
Figure 10 – Example of mounting support of panel board type SSE . 69
Figure 11 – Example of mounting support for a rear fixed SSE. 70
Figure 12 – Application of forces on a rail-mounted SSE . 72
Figure 13 – Determination of the direction of the forces to be applied . 74
Figure 14 – Direction for the conductor pull of 30 N for 1 min . 75
Figure 15 – Gauge (thickness: about 2 mm) for the verification of the outline of covers,
cover plates or actuating members . 78
Figure 16 – Example of application of the gauge of Figure 15 on covers fixed without
screws on a mounting surface or supporting surface . 79
Figure 17 – Examples of applications of the gauge of Figure 15 . 80
Figure 18 – Gauge for verification of grooves, holes and reverse tapers . 81
Figure 19 – Sketch showing the direction of application of the gauge of Figure 18 . 81
Figure 20 – Jointed test finger (test probe B according to IEC 61032:1997) . 85
Figure 21 – Test pin for checking the protection against electric shock . 86
Figure 22 – Actuator test force . 97
Figure 23 – Test circuit for connection to source 1 and source 2 . 99
Figure 24 – Ball-pressure test apparatus. 104
Figure 25 – Diagrammatic representation . 105
Figure 26 – Typical diagram for all coordination tests . 108

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Figure 27 – Detail of impedances Z and Z . 109
Figure 28 – Minimum clearances and creepage distances on printed boards . 120
Figure 29 – Surge test – Test circuit . 122
Figure 30 – Surge test – Example of a switch to be used in the test circuit. 123
Figure A.1 – Example of PEI . 126
Figure A.2 – Example of an individual PEI . 127
Figure A.3 – Example of a shared PEI with a distribution system within the PEI in
parallel to the DSO distribution system . 128
Figure A.4 – Example of SSE use in an individual PEI with PV production and storage

on the DC side . 129
Figure A.5 – Example of SSE use in an individual PEI with PV production and storage
on the AC side . 130
Figure A.6 – Example of SSE use for power backup with storage or a generating set . 131
Figure A.7 – Example of SSE use for power backup with storage only . 132
Figure C.1 – Example 1 . 135
Figure C.2 – Example 2 . 135
Figure C.3 – Example 3 . 135
Figure C.4 – Example 4 . 135
Figure C.5 – Example 5 . 136
Figure C.6 – Example 6 . 136
Figure C.7 – Example 7 . 136
Figure E.1 – Test arrangement . 140
Figure E.2 – Grid . 141
Figure E.3 – Grid circuit . 141

Table 1 – Source switching functional categories . 29
Table 2 – Preferred values of rated voltages . 33
Table 3 – Rated impulse voltage as a function of the nominal voltage of the installation . 34
Table 4 – Utilization categories . 35
Table 5 – Requirements and position for markings and other product information . 39
Table 6 – Cross-sectional areas (S) of test copper conductors corresponding to the
rated currents . 43
Table 7 – Minimum clearances and creepage distances . 47
Table 8 – Connectable cross-sections of copper conductors for screw-type terminals . 50
Table 9 – Temperature-rise values . 53
Table 10 – Making and breaking conditions for tests of making and breaking capacities . 54
Table 11 – OFF-time durations for the verification of making and breaking capacities

for utilization categories . 54
Table 12 – Making and breaking conditions for the operational performance . 58
Table 13 – Number of operations for operational performance . 58
Table 14 – Capacitors . 61
Table 15 – Tightening torque for the verification of the mechanical strength of screw-
type terminals . 62
Table 16 – Height of fall for impact test . 71

IEC 62991:2022 © IEC 2022 – 7 –
Table 17 – Forces to be applied to covers, cover plates or actuating members whose
fixing is not dependent on screws . 76
Table 18 – Test values for pulling out test . 83
Table 19 – Test voltage, points of application and minimum values of insulating
resistance for the verification of dielectric strength . 89
Table 20 – Test voltages of auxiliary circuits . 90
Table 21 – Test voltage for verification of impulse withstand voltage . 92
Table 22 – Temperature-rise test currents and cross-sectional areas of copper
conductors . 93
Table 23 – Actuator test force . 97
Table 24 – Minimum values of I t and I . 110
p
Table 25 – Power factors for short-circuit tests . 111
Table 26 – Immunity tests (overview) . 114
Table 27 – Performance criteria . 114
Table 28 – Voltage dip test values . 115
Table 29 – Short-interruption test values . 115
Table 30 – Surge test voltages . 115
Table 31 – Fast transient test values . 116
Table 32 – Permissible temperature rise values . 118
Table B.1 – Correspondence between ISO and AWG copper conductors . 133
Table D.1 – Test sequences and number of specimens for tests . 138

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PARTICULAR REQUIREMENTS FOR
SOURCE SWITCHING EQUIPMENT
...