SIST EN IEC 62271-105:2024

SLOVENSKI STANDARD
01-januar-2024
Visokonapetostne stikalne in krmilne naprave - 105. del: Kombinacije stikal za
izmenični tok z varovalkami za naznačene napetosti nad 1 kV do vključno 52 kV
(IEC 62271-105:2021)
High-voltage switchgear and controlgear - Part 105: Alternating current switch-fuse
combinations for rated voltages above 1 kV up to and including 52 kV (IEC 62271-
105:2021)
Hochspannungs-Schaltgeräte und -Schaltanlagen - Teil 105: Wechselstrom-
Lastschalter-Sicherungs-Kombinationen für Bemessungsspannungen über 1 kV bis
einschließlich 52 kV (IEC 62271-105:2021)
Appareillage à haute tension - Partie 105: Combinés interrupteurs-fusibles pour courant
alternatif de tensions assignées supérieures à 1 kV et jusqu'à 52 kV inclus (IEC 62271-
105:2021)
Ta slovenski standard je istoveten z: EN IEC 62271-105:2023
ICS:
29.130.10 Visokonapetostne stikalne in High voltage switchgear and
krmilne naprave controlgear
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 62271-105

NORME EUROPÉENNE
EUROPÄISCHE NORM November 2023
ICS 29.130.10 Supersedes EN 62271-105:2012
English Version
High-voltage switchgear and controlgear - Part 105: Alternating
current switch-fuse combinations for rated voltages above 1 kV
up to and including 52 kV
(IEC 62271-105:2021)
Appareillage à haute tension - Partie 105: Combinés Hochspannungs-Schaltgeräte und -Schaltanlagen -
interrupteurs-fusibles pour courant alternatif de tensions Teil 105: Wechselstrom-Lastschalter-Sicherungs-
assignées supérieures à 1 kV et jusqu'à 52 kV inclus Kombinationen für Bemessungsspannungen über 1 kV bis
(IEC 62271-105:2021) einschließlich 52 kV
(IEC 62271-105:2021)
This European Standard was approved by CENELEC on 2021-07-20. 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
© 2023 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 62271-105:2023 E

European foreword
The text of document 17A/1300/FDIS, future edition 3 of IEC 62271-105, prepared by SC 17A
"Switching devices" of IEC/TC 17 "High-voltage switchgear and controlgear" was submitted to the IEC-
CENELEC parallel vote and approved by CENELEC as EN IEC 62271-105:2023.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2024-05-10
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2026-11-10
document have to be withdrawn
This document supersedes EN 62271-105:2012 and all of its amendments and corrigenda (if any).
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 62271-105:2021 was approved by CENELEC as a
European Standard without any modification. In the official version, for Bibliography, the following note
has to be added for the standard indicated:
IEC 62271-202 NOTE Harmonized as EN 62271-202
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.
Clause 2 of EN 62271-1:2017 applies with the following additions:
Publication Year Title EN/HD Year
IEC 60050-441 - International Electrotechnical Vocabulary. - -
Switchgear, controlgear and fuses
IEC 60282-1 2020 High-voltage fuses - Part 1: Current- EN IEC 60282-1 2020
limiting fuses
IEC 62271-1 2017 High-voltage switchgear and controlgear - EN 62271-1 2017
Part 1: Common specifications for
alternating current switchgear and
controlgear
IEC 62271-100 2021 High-voltage switchgear and controlgear - EN IEC 62271-100 2021
Part 100: Alternating-current circuit-
breakers
IEC 62271-102 2018 High-voltage switchgear and controlgear - EN IEC 62271-102 2018
Part 102: Alternating current
disconnectors and earthing switches
IEC 62271-103 2021 High-voltage switchgear and controlgear - EN IEC 62271-103 2023
Part 103: Alternating current switches for
rated voltages above 1 kV up to and
including 52 kV
Annex ZB
(informative)
A-deviations
A-deviation: National deviation due to regulations, the alteration of which is for the time being outside
the competence of the CEN and/or CENELEC member.
This European Standard does not fall under any Directive/Regulation of the EU.
In the relevant CEN and/or CENELEC countries, these A-deviations are valid instead of the respective
provisions of the European Standard until the national situation causing the A-deviation has changed
Clause Deviation
General Italy
CAPITOLO VSR 8.B D.M. 1 DICEMBRE 1980 e succ. Modifiche
Disciplina dei contenitori a pressione di gas con membrature miste di materiale isolante
e di materiale metallico, contenenti parti attive di apparecchiature elettriche.
Gas filled compartments having a design pressure exceeding 0,5 bar (gauge) or a
volume exceeding 2 m shall be designed according to the Italian pressure vessel code
for electrical switchgear.
IEC 62271-105 ®
Edition 3.0 2021-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
High-voltage switchgear and controlgear –

Part 105: Alternating current switch-fuse combinations for rated voltages above

1 kV up to and including 52 kV

Appareillage à haute tension –

Partie 105: Combinés interrupteurs-fusibles pour courant alternatif de tensions

assignées supérieures à 1 kV et jusqu'à 52 kV inclus

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.130.10 ISBN 978-2-8322-9864-0

– 2 – IEC 62271-105:2021  IEC 2021
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 8
3 Terms and definitions . 8
3.1 General terms and definitions . 8
3.2 Assemblies of switchgear and controlgear . 8
3.3 Parts of assemblies . 8
3.4 Switching devices . 8
3.5 Parts of switchgear and controlgear . 9
3.6 Operational characteristics of switchgear and controlgear . 10
3.7 Characteristic quantities . 10
3.101 Fuses. 13
4 Normal and special service conditions . 14
5 Ratings . 14
5.1 General . 14
5.2 Rated voltage (U ) . 15
r
5.3 Rated insulation level (U , U , U ) . 15
d p s
5.4 Rated frequency (f ) . 15
r
5.5 Rated continuous current (I ) . 15
r
5.6 Rated short-time withstand current (I ) . 15
k
5.7 Rated peak withstand current (I ) . 15
p
5.8 Rated duration of short-circuit (t ) . 15
k
5.9 Rated supply voltage of auxiliary and control circuits (U ) . 15
a
5.10 Rated supply frequency of auxiliary and control circuits . 15
5.11 Rated pressure of compressed gas supply for controlled pressure systems . 15
5.101 Rated short-circuit breaking current . 16
5.102 Rated short-circuit making current . 16
5.103 Rated transfer current (striker operation) (I ) . 16
rtransfer
5.104 Rated take-over current for release-operated combinations (I ) . 16
rto
6 Design and construction . 16
6.1 Requirements for liquids in switch-fuse combinations . 16
6.2 Requirements for gases in switch-fuse combinations . 16
6.3 Earthing of switch-fuse combinations . 16
6.4 Auxiliary and control equipment and circuits . 17
6.5 Dependent power operation . 17
6.6 Stored energy operation . 17
6.7 Independent unlatched operation (independent manual or power operation) . 17
6.8 Manually operated actuators . 17
6.9 Operation of releases . 17
6.10 Pressure/level indication . 17
6.11 Nameplates. 17
6.12 Locking devices . 19
6.13 Position indication . 19
6.14 Degrees of protection provided by enclosures . 19

IEC 62271-105:2021  IEC 2021 – 3 –
6.15 Creepage distances for outdoor insulators . 19
6.16 Gas and vacuum tightness . 19
6.17 Tightness for liquid systems . 19
6.18 Fire hazard (flammability) . 19
6.19 Electromagnetic compatibility (EMC) . 19
6.20 X-ray emission . 19
6.21 Corrosion . 19
6.22 Filling levels for insulation, switching and/or operation . 19
6.101 Linkages between the fuse striker(s) and the switch release . 19
6.102 Low over-current conditions (long fuse-pre-arcing time conditions) . 19
7 Type tests . 20
7.1 General . 20
7.1.1 Basics . 20
7.1.2 Information for identification of test objects . 20
7.1.3 Information to be included in type-test reports . 20
7.2 Dielectric tests . 21
7.3 Radio interference voltage (RIV) test . 21
7.4 Resistance measurement . 21
7.5 Continuous current tests . 21
7.6 Short-time withstand current and peak withstand current tests . 21
7.7 Verification of the protection . 21
7.8 Tightness tests . 21
7.9 Electromagnetic compatibility tests (EMC) . 21
7.10 Additional tests on auxiliary and control circuits . 21
7.11 X-radiation test for vacuum interrupters . 21
7.101 Making and breaking tests . 22
7.101.1 General . 22
7.101.2 Conditions for performing the tests . 22
7.101.3 Test-duty procedures . 28
7.101.4 Behaviour of the combination during tests . 33
7.101.5 Condition of the apparatus after testing . 34
7.102 Mechanical operation tests . 35
7.103 Mechanical shock tests on fuses . 35
7.104 Thermal test with long pre-arcing time of fuse . 35
7.105 Extension of validity of type tests . 36
7.105.1 Dielectric . 36
7.105.2 Continuous current tests . 36
7.105.3 Making and breaking . 36
8 Routine tests . 36
8.101 Mechanical operating tests . 37
9 Guide to the selection of switch-fuse combinations (informative) . 37
9.101 Guide to the selection of switch-fuse combination for transformer protection . 37
9.101.1 General . 37
9.101.2 Rated short-circuit breaking current . 38
9.101.3 Primary fault condition caused by a solid short-circuit on the
transformer secondary terminals . 38
9.102 Coordination of switch and fuses for extension of the reference list of fuses . 39
9.102.1 General . 39
9.102.2 Rated continuous current . 39

– 4 – IEC 62271-105:2021  IEC 2021
9.102.3 Low over-current performance . 39
9.102.4 Transfer current . 39
9.102.5 Take-over current . 39
9.102.6 Extension of the validity of type tests . 40
10 Information to be given with enquiries, tenders and orders (informative) . 40
10.1 General . 40
10.2 Information with enquiries and orders . 40
10.3 Information with tenders . 40
11 Transport, storage, installation, operating instructions and maintenance. 40
12 Safety . 41
13 Influence of the product on the environment . 41
Annex A (informative) Example of the coordination of fuses, switch and transformer . 42
Annex B (normative) Procedures for determining transfer current . 45
B.1 Background. 45
B.2 Mathematical determination of ∆T . 45
B.3 Simplified method for determination of transfer current . 48
Annex C (normative) Tolerances on test quantities for type tests . 50
Bibliography . 52

Figure 1 – Arrangement of test circuits for test duties TD and TD . 23
Isc IWmax
Figure 2 – Arrangement of test circuits for test-duty TD . 24
Itransfer
Figure 3 – Arrangement of test circuits for test-duty TD . 24
Ito
Figure 4 – Determination of power-frequency recovery voltage . 26
Figure 5 – Representation of a specified TRV by a two-parameter reference line and a
delay line . 27
Figure 6 – Example of a two-parameter reference line for a TRV . 28
Figure 7 – Characteristics for determining take-over current . 32
Figure 8 – Transfer current in relation to the primary fault current I due to a solid
sc
short circuit in the transformer secondary terminal . 38
Figure A.1 – Characteristics relating to the protection of an 11 kV, 400 kVA
transformer . 43
Figure A.2 – Discrimination between HV and LV fuses . 44
Figure B.1 – Practical determination of the transfer current . 46
Figure B.2 – Determination of the transfer current with the iterative method . 48

Table 1 – Nameplate information . 18
Table 2 – Summary of the conditions for combining tests and alternative procedures . 23
Table 3 – Values of prospective TRV for test-duty TD based on practice in
Itransfer
Europe . 30
Table 4 – Values of prospective TRV for test-duty TD based on practice in the
Itransfer
United States of America . 31
Table 5 – Summary of test parameters for test duties . 33
Table C.1 – Tolerances on test quantities for type tests . 50

IEC 62271-105:2021  IEC 2021 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HIGH-VOLTAGE SWITCHGEAR AND CONTROLGEAR –

Part 105: Alternating current switch-fuse combinations
for rated voltages above 1 kV up to and including 52 kV

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,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their
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
transparently to the maximum extent possible in their national and regional publications. Any divergence between
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
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
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) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC 62271-105 has been prepared by subcommittee 17A: Switching devices, of IEC technical
committee 17: High-voltage switchgear and controlgear. It is an International Standard.
This third edition cancels and replaces the second edition published in 2012. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the document has been updated to be in alignment with the second edition of
IEC 62271-1:2017;
b) rated TRV has been removed (TRV is only a test parameter), as in the latest revision of
IEC 62271-100;
– 6 – IEC 62271-105:2021  IEC 2021
c) differentiation has been introduced between requirements expressed for fulfilling the
function expected from a switch-fuse combination, from requirements only relevant when
the function is performed by a stand-alone device. The goal is to avoid duplication or
conflicts of requirements with a standard dealing with assemblies, when the function is
implemented within such an assembly.
The text of this International Standard is based the following documents:
FDIS Report on voting
17A/1300/FDIS 17A/1306/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.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
This document is to be read in conjunction with IEC 62271-1:2017, to which it refers and which
is applicable unless otherwise specified. In order to simplify the indication of corresponding
requirements, the same numbering of clauses and subclauses is used as in IEC 62271-1:2017.
Amendments to these clauses and subclauses are given under the same numbering, whilst
additional subclauses are numbered from 101.
A list of all parts in the IEC 62271 series, published under the general title High-voltage
switchgear and controlgear, 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 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.
IEC 62271-105:2021  IEC 2021 – 7 –
HIGH-VOLTAGE SWITCHGEAR AND CONTROLGEAR –

Part 105: Alternating current switch-fuse combinations
for rated voltages above 1 kV up to and including 52 kV

1 Scope
This part of IEC 62271 applies to three-pole units for public and industrial distribution systems
which are functional assemblies of switches composed of switches or switch-disconnectors and
current-limiting fuses designed so as to be capable of
– breaking, at the rated voltage, any current up to and including the rated short-circuit
breaking current;
– making, at the rated voltage, circuits to which the rated short-circuit breaking current
applies.
It does not apply to combinations of fuses with circuit-breakers, contactors or circuit switchers,
nor for combinations for motor-circuits nor to combinations incorporating single capacitor bank
switches.
This document applies to combinations designed with rated voltages above 1 kV up to and
including 52 kV for use on three-phase alternating current systems of either 50 Hz or 60 Hz.
In this document, the word "combination" is used for a combination in which the components
constitute a functional assembly. Each association of a given type of switch and a given type
of fuse defines one type of switch-fuse combination. Different types of fuses can be combined
with one type of switch, which give several combinations with different characteristics, in
particular concerning the rated continuous currents.
A switch-fuse combination is therefore defined by its type designation and a list of selected
fuses defined by the manufacturer, the so-called "reference list of fuses". Compliance with this
document of a given combination means that every combination using one of the selected fuses
is proven to be in compliance with this document.
The fuses are incorporated in order to extend the short-circuit breaking rating of the combination
beyond that of the switch alone. They are fitted with strikers in order both to open automatically
all three poles of the switch on the operation of a fuse and to achieve a correct operation at
values of fault current above the minimum melting current but below the minimum breaking
current of the fuses. In addition to the fuse strikers, the combination can be fitted with either an
over-current release or a shunt release.
NOTE In this document the term "fuse" is used to designate either the fuse or the fuse-link where the general
meaning of the text does not result in ambiguity.
Fuses are in accordance with IEC 60282-1:2020.
Devices that require dependent manual operation are not covered by this document.
Switches, including their specific mechanism, are in accordance with IEC 62271-103 except for
the short-time current and short-circuit making requirements where the current-limiting effects
of the fuses are taken into account.
Earthing switches forming an integral part of a combination are covered by IEC 62271-102.

– 8 – IEC 62271-105:2021  IEC 2021
In addition, switches which include other functions (not covered by IEC 62271-103) are covered
by their relevant standards (e.g. IEC 62271-102 for disconnectors and earthing switches).
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.
Clause 2 of IEC 62271-1:2017 applies with the following additions:
IEC 60050-441, International Electrotechnical Vocabulary (IEV) – Part 441: Switchgear,
controlgear and fuses (available at http://www.electropedia.org)
IEC 60282-1:2020, High-voltage fuses – Part 1: Current-limiting fuses
IEC 62271-1:2017, High-voltage switchgear and controlgear – Part 1: Common specifications
for alternating current switchgear and controlgear
IEC 62271-100:2021, High-voltage switchgear and controlgear – Part 100: Alternating-current
circuit-breakers
IEC 62271-102:2018, High-voltage switchgear and controlgear – Part 102: Alternating current
disconnectors and earthing switches
IEC 62271-103:2021, High-voltage switchgear and controlgear – Part 103: Switches for rated
voltages above 1 kV up to and including 52 kV
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-441 and the
following 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
NOTE Some of the terms given in IEC 60050-441 are listed hereunder.
3.1 General terms and definitions
Subclause 3.1 of IEC 62271-1:2017 applies.
3.2 Assemblies of switchgear and controlgear
Subclause 3.2 of IEC 62271-1:2017 applies.
3.3 Parts of assemblies
Subclause 3.3 of IEC 62271-1:2017 applies.
3.4 Switching devices
Subclause 3.4 of IEC 62271-1:2017 applies, with the following additions:

IEC 62271-105:2021  IEC 2021 – 9 –
3.4.101
switch-fuse combination
combination of a three-pole switch with three fuses provided with strikers, the operation of any
striker causing all three poles of the switch to open automatically
Note 1 to entry: The switch-fuse combination includes the fuse-switch combination.
3.4.102
switch-fuse combination base
combination base
switch-fuse combination without fuse-links mounted
3.4.103
switch-fuse
switch in which one or more poles have a fuse in series in a composite unit
[SOURCE: IEC 60050-441:2000, 441-14-14]
3.4.104
fuse-switch
switch in which a fuse-link or a fuse-carrier with fuse-link forms the moving contact
[SOURCE: IEC 60050-441:2000, 441-14-17]
3.4.105
switch-disconnector
switch which, in the open position, satisfies the isolating requirements specified for a
disconnector
[SOURCE: IEC 60050-441:2000, 441-14-12]
3.4.106
release-operated combination
combination in which automatic opening of the switch can also be initiated by either an over-
current release or a shunt release
3.5 Parts of switchgear and controlgear
Subclause 3.5 of IEC 62271-1:2017 applies, with the following additions:
3.5.101
release
device, mechanically connected to a mechanical switching
device, which releases the holding means and permits the opening or the closing of the
switching device
[SOURCE: IEC 60050-441:2000, 441-15-17]
3.5.102
over-current release
release which permits a mechanical switching device to open with or without time-delay when
the current in the release exceeds a predetermined value
Note 1 to entry: This value can in some cases depend upon the rate-of-rise of current.
[SOURCE: IEC 60050-441:2000, 441-16-33]

– 10 – IEC 62271-105:2021  IEC 2021
3.5.103
shunt release
release energized by a source of voltage
Note 1 to entry: The source of voltage may be independent of the voltage of the main circuit.
[SOURCE: IEC 60050-441:2000, 441-16-41]
3.6 Operational characteristics of switchgear and controlgear
Subclause 3.6 of IEC 62271-1:2017 applies.
3.7 Characteristic quantities
Subclause 3.7 of IEC 62271-1:2017 applies, with the following additions:
3.7.101
prospective current
current that would flow in the
circuit if each pole of the switching device or the fuse were replaced by a conductor of negligible
impedance
Note 1 to entry: The method to be used to evaluate and to express the prospective current is to be specified in the
relevant publications.
[SOURCE: IEC 60050-441:2000, 441-17-01]
3.7.102
prospective peak current
peak value of a prospective current during the transient period following initiation
Note 1 to entry: The definition assumes that the current is made by an ideal switching device, i.e. with instantaneous
transition from infinite to zero impedance. For circuits where the current can follow several different paths, e.g.
polyphase circuits, it further assumes that the current is made simultaneously in all poles, even if only the current in
one pole is considered.
[SOURCE: IEC 60050-441:2000, 441-17-02]
3.7.103
maximum prospective peak current
prospective peak current when initiation of the current takes place at the
instant which leads to the highest possible value
Note 1 to entry: For a multiple device in a polyphase circuit, the maximum prospective peak current refers to a
single-pole only.
[SOURCE: IEC 60050-441:2000, 441-17-04]
3.7.104
breaking current
current in a pole of a switching device or in a fuse at the
instant of initiation of the arc during a breaking process
[SOURCE: IEC 60050-441:2000, 441-17-07]

IEC 62271-105:2021  IEC 2021 – 11 –
3.7.105
minimum breaking current
minimum value of prospective current that a fuse-link is capable of breaking at a stated voltage
under prescribed conditions of use and behaviour
[SOURCE: IEC 60050-441:2000, 441-18-29]
3.7.106
short-circuit making capacity
making capacity for which the prescribed conditions include a short circuit at the terminals of
the switching device
[SOURCE: IEC 60050-441:2000, 441-17-10]
3.7.107
cut-off current
let-through current
maximum instantaneous value of current attained during the breaking operation of a switching
device or a fuse
Note 1 to entry: This concept is of particular importance when the switching device or the fuse operates in such a
manner that the prospective peak current of the circuit is not reached.
[SOURCE: IEC 60050-441:2000, 441-17-12]
3.7.108
transfer current
I
transfer
value of the three-phase symmetrical current at which the fuses and the
switch exchange breaking duties
Note 1 to entry: Above this value the three-phase current is interrupted by the fuses only. Immediately below this
value, the current in the first-pole-to-clear is interrupted by the fuse and the current in the other two poles by the
switch, or by the fuses, depending on the tolerances of the fuse time current characteristic and the fuse-initiated
opening time of the switch.
3.7.109
take-over current
current co-ordinate of the intersection between the time-current characteristics of two over-
current protective devices
[SOURCE: IEC 60050-441:2000, 441-17-16]
3.7.110
minimum take-over current
current determined by the point of intersection of the time-
current characteristics of the fuse and the switch corresponding to
a) the maximum break-time plus, where applicable, the maximum operating time of an external
over-current or earth-fault relay,
b) the minimum pre-arcing time of the fuse
3.7.111
maximum take-over current
current determined by the point of intersection of the time-
current characteristics of the fuse and the switch corresponding to:
a) the minimum opening time plus, where applicable, the minimum operating time of an
external over-current or earth-fault relay,
b) the maximum operating time of the fuse

– 12 – IEC 62271-105:2021  IEC 2021
3.7.112
applied voltage
voltage which exists across the terminals of a pole of a switching
device just before the making of the current
[SOURCE: IEC 60050-441:2000, 441-17-24]
3.7.113
recovery voltage
voltage which appears across the terminals of a pole of a switching device or a fuse after the
breaking of the current
Note 1 to entry: This voltage may be considered in two successive intervals of time, one during which a transient
voltage exists, followed by a second one during which the power-frequency or the steady-state recovery voltage
alone exists.
[SOURCE: IEC 60050-441:2000, 441-17-25]
3.7.114
transient recovery voltage
TRV
recovery voltage during the time in which it has a significant transient character
Note 1 to entry: The transient recovery voltage may be oscillatory or non-oscillatory or a combination of these
depending on the characteristics of the circuit and the switching device. It includes the voltage shift of the neutral of
a polyphase circuit.
Note 2 to entry: The transient recovery voltages in three-phase circuits is, unless otherwise stated, that across the
first pole to clear, because this voltage is generally higher than that which appears across each of the other two
poles.
[SOURCE: IEC 60050-441:2000, 441-17-26]
3.7.115
power-frequency recovery voltage
recovery voltage after the transient voltage phenomena have subsided
[SOURCE: IEC 60050-441:2000, 441-17-27]
3.7.116
prospective transient recovery voltage
transient recovery voltage following the breaking of the prospective symmetrical
current by an ideal switching device
Note 1 to entry: The definition assumes that the switching device or the fuse, for which the prospective transient
recovery voltage is sought, is replaced by an ideal switching device, i.e. having instantaneous transition from zero
to infinite impedance at the very instant of zero current, i.e. at the "natural" zero. For circuits where the current can
follow several different paths, e.g. a polyphas
...