IEC 62271-105:2012

IEC 62271-105 ®
Edition 2.0 2012-09
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

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IEC 62271-105 ®
Edition 2.0 2012-09
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
PRICE CODE
INTERNATIONALE
CODE PRIX XA
ICS 29.130.10 ISBN 978-2-83220-401-6

– 2 – 62271-105 © IEC:2012
CONTENTS
FOREWORD . 5
1 General . 7
1.1 Scope . 7
1.2 Normative references . 8
2 Normal and special service conditions . 8
3 Terms and definitions . 8
3.1 General terms . 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 Operation . 10
3.7 Characteristic quantities . 10
3.101 Fuses . 14
4 Ratings . 15
4.1 Rated voltage (U ) . 15
r
4.2 Rated insulation level . 15
4.3 Rated frequency (f ) . 15
r
4.4 Rated normal current and temperature rise . 15
4.4.1 Rated normal current (I ) . 15
r
4.4.2 Temperature rise . 15
4.5 Rated short-time withstand current (I ) . 15
k
4.6 Rated peak withstand current (I ) . 15
p
4.7 Rated duration of short-circuit (t ) . 15
k
4.8 Rated supply voltage of closing and opening devices and of auxiliary and
control circuits (U ) . 16
a
4.9 Rated supply frequency of closing and opening devices and of auxiliary
circuits . 16
4.10 Rated pressure of compressed gas supply for controlled pressure systems . 16
4.11 Rated filling levels for insulation and/or operation . 16
4.101 Rated short-circuit breaking current . 16
4.102 Rated transient recovery voltage . 16
4.103 Rated short-circuit making current . 16
4.104 Rated transfer current (striker operation) (I ) . 17
rtransfer
4.105 Rated take-over current for release-operated combinations (I ) . 17
to
5 Design and construction . 17
5.1 Requirements for liquids in switch-fuse combinations . 17
5.2 Requirements for gases in switch-fuse combinations . 17
5.3 Earthing of switch-fuse combinations . 17
5.4 Auxiliary and control equipment . 17
5.5 Dependent power operation . 17
5.6 Stored energy operation . 17
5.7 Independent manual or power operation (independent unlatched operation) . 17
5.8 Operation of releases . 17
5.9 Low- and high-pressure interlocking and monitoring devices . 17
5.10 Nameplates . 17

62271-105 © IEC:2012 – 3 –
5.11 Interlocking devices . 18
5.12 Position indication . 18
5.13 Degrees of protection provided by enclosures. 18
5.14 Creepage distances for outdoor insulators . 18
5.15 Gas and vacuum tightness . 19
5.16 Liquid tightness . 19
5.17 Fire hazard (flammability) . 19
5.18 Electromagnetic compatibility (EMC). 19
5.19 X-ray emission . 19
5.20 Corrosion . 19
5.101 Linkages between the fuse striker(s) and the switch release . 19
5.102 Low over-current conditions (long fuse-pre-arcing time conditions) . 19
6 Type tests . 20
6.1 General . 20
6.1.1 Grouping of tests . 20
6.1.2 Information for identification of specimens . 21
6.1.3 Information to be included in the type-test reports . 21
6.2 Dielectric tests . 21
6.3 Radio interference voltage (r.i.v.) tests . 21
6.4 Measurement of the resistance of circuits . 21
6.5 Temperature-rise tests . 21
6.6 Short-time withstand current and peak withstand current tests . 21
6.7 Verification of the protection . 21
6.8 Tightness tests . 21
6.9 Electromagnetic compatibility tests (EMC) . 21
6.10 Additional tests on auxiliary and control circuits . 21
6.11 X-radiation test procedure for vacuum interrupters. 22
6.101 Making and breaking tests . 22
6.101.1 General . 22
6.101.2 Conditions for performing the tests . 22
6.101.3 Test-duty procedures . 28
6.101.4 Behaviour of the combination during tests . 33
6.101.5 Condition of the apparatus after testing . 33
6.102 Mechanical operation tests . 34
6.103 Mechanical shock tests on fuses . 34
6.104 Thermal test with long pre-arcing time of fuse . 35
6.105 Extension of validity of type tests . 35
6.105.1 Dielectric . 35
6.105.2 Temperature rise . 35
6.105.3 Making and breaking . 35
7 Routine tests . 36
7.101 Mechanical operating tests . 36
8 Guide for the selection of switch-fuse combinations . 36
8.1 Selection of rated values . 36
8.2 Continuous or temporary overload due to changed service conditions . 37
8.101 Guide for the selection of switch-fuse combination for transformer protection . 37
8.101.1 General . 37
8.101.2 Rated short-circuit breaking current . 37

– 4 – 62271-105 © IEC:2012
8.101.3 Primary fault condition caused by a solid short-circuit on the
transformer secondary terminals . 37
8.102 Coordination of switch and fuses for extension of the reference list . 38
8.102.1 General . 38
8.102.2 Rated normal current . 38
8.102.3 Low over-current performance . 39
8.102.4 Transfer current . 39
8.102.5 Take-over current . 39
8.102.6 Extension of the validity of type tests . 39
8.103 Operation . 39
9 Information to be given with enquiries, tenders and orders . 40
9.1 Information with enquiries and orders . 40
9.2 Information with tenders . 40
10 Transport, storage, installation, operation and maintenance . 40
11 Safety . 41
12 Influence of the product on the environment . 41
Annex A (informative) Example of the coordination of fuses, switch and transformer . 42
Annex B (normative) Procedure for determining transfer current . 45
Annex C (normative) Tolerances on test quantities for type tests . 50
Bibliography . 51

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 markings . 18
Table 2 – Standard values of prospective TRV for test-duty TD based on
Itransfer
practice in Europe . 30
Table 3 – Standard values of prospective TRV for test-duty TD based on
Itransfer
practice in the United States of America and Canada . 31
Table 4 – Summary of test parameters for test duties . 32
Table C.1 – Tolerances on test quantities for type tests . 50

62271-105 © IEC:2012 – 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-
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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.
International Standard IEC 62271-105 has been prepared by subcommittee 17A, High-voltage
switchgear and controlgear, of IEC technical committee 17: Switchgear and controlgear.
This second edition cancels and replaces the first edition of IEC 62271-105, published in
2002, and constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
– implementation of figures at the place where they are cited first;
– renumbering of tables;
– addition of some of the proposals from IEC paper 17A/852/INF;
– addition of missing subclauses of IEC 62271-1;
– implementation of 6.105 "Extension of validity of type tests" and consequently removing of
the relevant parts in the different existing clauses;

– 6 – 62271-105 © IEC:2012
– change of 7th paragraph of 6.101.4 as there is now a definition of NSDD given in 3.7.4 of
IEC 62271-1:2007. Harmonization with IEC 62271-107;
– some referenced clauses in other standards like IEC 60282-1 were changed and therefore
changed the editions under 1.2 to the ones referred to;
– addition of a new Annex C defining tolerances.
The text of this standard is based the following documents:
FDIS Report on voting
17A/1013/FDIS 17A/1022/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
This standard is to be read in conjunction with IEC 62271-1:2007, to which it refers and which
is applicable, unless otherwise specified in this standard. In order to simplify the indication of
corresponding requirements, the same numbering of clauses and subclauses is used as in
IEC 62271-1. 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 publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
62271-105 © IEC:2012 – 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 General
1.1 Scope
Subclause 1.1 of IEC 62271-1:2007 is not applicable, and is replaced as follows:.
This part of IEC 62271 applies to three-pole units for public and industrial distribution systems
which are functional assemblies of switches including switch-disconnectors and current-
limiting fuses designed so as to be capable of
– breaking, at the rated recovery 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 fuse-circuit-breakers, fuse-contactors, combinations for motor-circuits or
to combinations incorporating single capacitor bank switches.
In this standard, 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 combination.
In practice, different types of fuses may be combined with one type of switch, which give
several combinations with different characteristics, in particular concerning the rated currents.
Moreover, for maintenance purposes, the user should know the types of fuses that can be
combined to a given switch without impairing compliance to the standard, and the
corresponding characteristics of the so-made combination.
A switch-fuse combination is then defined by its type designation and a list of selected fuses
is defined by the manufacturer, the so-called “reference list of fuses”. Compliance with this
standard of a given combination means that every combination using one of the selected
fuses is proven to be in compliance with this standard.
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 may be fitted
with either an over-current release or a shunt release.
NOTE In this standard 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.
This standard 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.
Fuses are covered by IEC 60282-1.
Devices that require dependent manual operation are not covered by this standard.

– 8 – 62271-105 © IEC:2012
Switches, including their specific mechanism, shall be 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.
1.2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
Subclause 1.2 of IEC 62271-1:2007 is applicable with the following additions:
IEC 60282-1:2009, High-voltage fuses – Part 1: Current-limiting fuses
IEC/TR 60787:2007, Application guide for the selection of high-voltage current-limiting fuse-
links for transformer circuits
IEC 62271-1:2007, High-voltage switchgear and controlgear – Part 1: Common specifications
IEC 62271-100:2008, High-voltage switchgear and controlgear – Part 100: Alternating-current
circuit-breakers
IEC 62271-102:2001, High-voltage switchgear and controlgear – Part 102: Alternating current
disconnectors and earthing switches
IEC 62271-103:2011, High-voltage switchgear and controlgear – Part 103: Switches for rated
voltages above 1 kV up to and including 52 kV
2 Normal and special service conditions
Clause 2 of IEC 62271-1:2007 is applicable.
3 Terms and definitions
Clause 3 of IEC 62271-1:2007 is applicable with the the following additions.
3.1 General terms
Subclause 3.1 of IEC 62271-1:2007 is applicable.
3.2 Assemblies of switchgear and controlgear
Subclause 3.2 of IEC 62271-1:2007 is applicable.
3.3 Parts of assemblies
Subclause 3.3 of IEC 62271-1:2007 is applicable.
3.4 Switching devices
Subclause 3.4 of IEC 62271-1:2007 is applicable, with the following additions

62271-105 © IEC:2012 – 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 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 60050-441:2007, 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 60050-441:2007, 441-14-17]
3.4.105
switch-disconnector
switch which, in the open position, satisfies the isolating requirements specified for a
disconnector
[SOURCE: IEC 60050-441:2007, 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 62271-1:2007 is applicable, with the following additions.
3.5.101
release (of a mechanical switching device)
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 60050-441:2007, 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 60050-441:2007, 441-16-33]
3.5.103
shunt release
release energized by a source of voltage

– 10 – 62271-105 © IEC:2012
Note 1 to entry: The source of voltage may be independent of the voltage of the main circuit.
[SOURCE: IEC 60050-441:2007, 441-16-41]
3.6 Operation
Subclause 3.6 of IEC 62271-1:2007 is applicable, with the following additions.
3.6.101
independent manual operation (of a mechanical switching device)
stored energy operation where the energy originates from manual power, stored and released
in one continuous operation, such that the speed and force of the operation are independent
of the action of the operator
[SOURCE: IEC 60050-441:2007, 441-16-16]
3.6.102
stored energy operation (of a mechanical switching device)
operation by means of energy stored in the mechanism itself prior to the completion of the
operation and sufficient to complete it under predetermined conditions
Note 1 to entry: This kind of operation may be subdivided according to:
a) The manner of storing the energy (spring, weight, etc.);
b) The origin of the energy (manual, electric, etc.);
c) The manner of releasing the energy (manual, electric, etc.).
[SOURCE: IEC 60050-441:2007, 441-16-15]
3.7 Characteristic quantities
Subclause 3.7 of IEC 62271-1:2007 is applicable, with the following additions.
3.7.101
prospective current (of a circuit and with respect to a switching device or a fuse)
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 60050-441:2007, 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 60050-441:2007, 441-17-02]
3.7.103
maximum prospective peak current (of an a.c. circuit)
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.
62271-105 © IEC:2012 – 11 –
[SOURCE: IEC 60050-441:2007, 441-17-04]
3.7.104
prospective breaking current (for a pole of a switching device or a fuse)
prospective current evaluated at a time corresponding to the instant of the initiation of the
breaking process
Note 1 to entry: Specifications concerning the instant of the initiation of the breaking process are to be found in
the relevant publications. For mechanical switching devices or fuses, it is usually defined as the moment of
initiation of the arc during the breaking process.
[SOURCE: IEC 60050-441:2007, 441-17-06]
3.7.105
breaking current (of a switching device or a fuse)
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 60050-441:2007, 441-17-07]
3.7.106
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 60050-441:2007, 441-18-29]
3.7.107
short-circuit making capacity
making capacity for which the prescribed conditions include a short circuit at the terminals of
the switching device
[SOURCE: IEC 60050-441:2007, 441-17-10]
3.7.108
cut-off current
let-through current (of a fuse)
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 60050-441:2007, 441-17-12]
3.7.109
transfer current (striker operation)
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.
3.7.110
take-over current
current co-ordinate of the intersection between the time-current characteristics of two over-
current protective devices
[SOURCE: IEC 60050-441:2007, 441-17-16]

– 12 – 62271-105 © IEC:2012
3.7.111
minimum take-over current (of a release-operated combination)
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
3.7.112
maximum take-over current (of a release-operated combination)
current determined by the point of intersection of the time-current characteristics of the fuse
and the switch corresponding to:
a) the minimum break time plus, where applicable, the minimum operating time of an external
over-current or earth-fault relay,
b) the maximum pre-arcing time of the fuse
3.7.113
fused short-circuit current
conditional short-circuit current when the current limiting device is a fuse
[SOURCE: IEC 60050-441:2007, 441-17-21]
3.7.114
applied voltage (for a switching device)
voltage which exists across the terminals of a pole of a switching device just before the
making of the current
[SOURCE: IEC 60050-441:2007, 441-17-24]
3.7.115
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 60050-441:2007, 441-17-25]
3.7.116
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 60050-441:2007, 441-17-26]
3.7.117
power-frequency recovery voltage
recovery voltage after the transient voltage phenomena have subsided
[SOURCE: IEC 60050-441:2007, 441-17-27]

62271-105 © IEC:2012 – 13 –
3.7.118
prospective transient recovery voltage (of a circuit)
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 polyphase circuit, the definition further assumes that the breaking of the
current by the ideal switching device takes place only in the pole considered.
[SOURCE: IEC 60050-441:2007, 441-17-29]
3.7.119
fuse-initiated opening time (of the switch-fuse combination)
time taken from the instant at which arcing in the fuse commences to the instant when the
arcing contacts of the switch of the combination have separated in all poles (including all
elements influencing this time)
3.7.120
release-initiated opening time (of the switch-fuse combination)
release-initiated opening time is defined according to the tripping method as stated below with
any time-delay device forming an integral part of the switch adjusted to a specified setting:
a) for a switch tripped by any form of auxiliary power, interval of time between the instant of
energizing the opening release, the switch being in the closed position, and the instant
when the arcing contacts have separated in all poles;
b) for a switch tripped (other than by the striker) by a current in the main circuit without the
aid of any form of auxiliary power, interval of time between the instant at which,
the switch being in the closed position, the current in the main circuit reaches the
operating value of the over-current release and the instant when the arcing contacts
have separated in all poles
3.7.121
minimum release-initiated opening time (of the switch-fuse combination)
release-initiated opening time when the specified setting of any time-delay device forming an
integral part of the switch is its minimum setting
3.7.122
maximum release-initiated opening time (of the switch-fuse combination)
release-initiated opening time when the specified setting of any time-delay device forming
an integral part of the switch is its maximum setting
3.7.123
break-time
interval of time between the beginning of the opening time of a mechanical switching device
(or the pre-arcing time of a fuse) and the end of the arcing time
[SOURCE: IEC 60050-441:2007, 441-17-39]
3.7.124
arcing time (of a pole or a fuse)
interval of time between the instant of the initiation of the arc in a pole or a fuse and the
instant of final arc extinction in that pole or that fuse
[SOURCE: IEC 60050-441:2007, 441-17-37]

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