IEC 62271-107:2012

IEC 62271-107 ®
Edition 2.0 2012-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
High-voltage switchgear and controlgear –
Part 107: Alternating current fused circuit-switchers for rated voltages above
1 kV up to and including 52 kV

Appareillage à haute tension –
Partie 107: Circuits-switchers fusiblés pour courant alternatif de tension
assignée supérieure à 1 kV et jusqu'à 52 kV inclus

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IEC 62271-107 ®
Edition 2.0 2012-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
High-voltage switchgear and controlgear –

Part 107: Alternating current fused circuit-switchers for rated voltages above

1 kV up to and including 52 kV

Appareillage à haute tension –

Partie 107: Circuits-switchers fusiblés pour courant alternatif de tension

assignée supérieure à 1 kV et jusqu'à 52 kV inclus

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX X
ICS 29.130.10 ISBN 978-2-83220-119-0

– 2 – 62271-107 © IEC:2012
CONTENTS
FOREWORD . 5

1 General . 7

1.1 Scope . 7

1.2 Normative references . 7

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 . 9
3.7 Characteristic quantities . 10
3.101 Fuses . 12
4 Ratings . 12
4.1 Rated voltage (U ) . 13
r
4.2 Rated insulation level . 13
4.3 Rated frequency (f ) . 13
r
4.4 Rated normal current and temperature rise . 13
4.4.1 Rated normal current (I ) . 13
r
4.4.2 Temperature rise. 13
4.4.101 Rated maximum thermal current (I ) . 13
th
4.5 Rated short-time withstand current (I ) . 13
k
4.6 Rated peak withstand current (I ) . 13
p
4.7 Rated duration of short circuit (t ) . 14
k
4.8 Rated supply voltage of closing and opening devices and of auxiliary and
control circuits (U ) . 14
a
4.9 Rated supply frequency of closing and opening devices and of auxiliary
circuits . 14
4.10 Rated pressure of compressed gas supply for controlled pressure systems . 14
4.11 Rated filling levels for insulation and/or operation . 14
4.101 Rated short-circuit breaking current I . 14
sc
4.102 Rated transient recovery voltage . 14
4.103 Rated short-circuit making current . 14
4.104 Rated take-over current . 15
5 Design and construction . 15
5.1 Requirements for liquids in fused circuit-switchers . 15
5.2 Requirements for gases in fused circuit-switchers. 15
5.3 Earthing of fused circuit-switchers . 15
5.4 Auxiliary and control equipment . 15
5.5 Dependent power operation . 16
5.6 Stored energy operation . 16
5.7 Independent manual or power operation (independent unlatched operation) . 16
5.8 Operation of releases . 16
5.9 Low- and high- pressure interlocking and monitoring devices. 16
5.10 Nameplates . 16

62271-107 © IEC:2012 – 3 –
5.11 Interlocking devices . 17

5.12 Position indication . 17

5.13 Degrees of protection by enclosures . 17

5.14 Creepage distances for outdoor insulators . 17

5.15 Gas and vacuum tightness . 17

5.16 Liquid tightness . 17

5.17 Fire hazard (flammability) . 17

5.18 Electromagnetic compatibility (EMC) . 17

5.19 X-ray emission . 17

5.20 Corrosion . 17

5.101 Linkages between the fuse striker(s) and the circuit-switcher release . 18
5.102 Low over-current conditions (long fuse pre-arcing time conditions) . 18
6 Type tests . 18
6.1 General . 18
6.1.1 Grouping of tests . 19
6.1.2 Information for identification of specimens . 19
6.1.3 Information to be included in type-test reports . 19
6.2 Dielectric tests . 19
6.3 Radio interference voltage (r.i.v.) test . 19
6.4 Measurement of the resistance of circuits . 19
6.5 Temperature-rise tests . 19
6.6 Short-time withstand current and peak withstand current tests . 19
6.7 Verification of the protection . 19
6.8 Tightness tests . 20
6.9 Electromagnetic compatibility tests (EMC) . 20
6.10 Additional tests on auxiliary and control circuits . 20
6.11 X-radiation test procedure for vacuum interrupters . 20
6.101 Making and breaking tests . 20
6.101.1 Conditions for performing the tests. 20
6.101.2 Test duty procedures . 25
6.101.3 Behaviour of the fused circuit-switcher during tests . 30
6.101.4 Condition of the apparatus after tests . 30
6.102 Mechanical operation tests . 31
6.102.1 Condition of fused circuit-switcher during and after mechanical
operation tests . 32

6.102.2 Condition of the fuses during and after mechanical operation tests . 32
6.103 Extension of validity of type tests . 32
6.103.1 Dielectric properties . 32
6.103.2 Temperature rise. 32
6.103.3 Making and breaking . 33
7 Routine tests . 33
7.101 Mechanical operating tests . 33
8 Guide for the selection of fused circuit-switchers . 34
8.1 Selection of rated values . 34
8.2 Continuous or temporary overload due to changed service conditions . 34
8.101 Additional criteria . 34
8.102 Short-circuit breaking current . 34
8.103 Rated maximum thermal current . 35
8.104 Currents between thermal current and I of the fuses . 35
– 4 – 62271-107 © IEC:2012
8.105 Transfer current . 35

8.106 Take-over current . 35

8.107 Extension of the validity of type tests . 35

8.108 Operation . 36

8.109 Comparison of performances of fused circuit-switchers with performances

of switch-fuse combinations and circuit-breakers . 36

9 Information to be given with enquiries, tenders and orders . 37

9.1 Information to be given with enquiries and orders . 37

9.2 Information to be given with tenders . 37

10 Rules for transport, storage, installation, operation and maintenance . 38

11 Safety . 38
12 Influence of the product on the environment . 38
Annex A (informative) Applicability of the rated take-over current test duty . 39
Bibliography . 47

Figure 1 – Characteristics for determining the take-over current . 15
Figure 2 – Arrangement of test circuits for test duties TD , TD , TD and TD . 22
Ith Isc Ito Ilow
Figure 3 – Representation of a specified TRV by a two-parameter reference line and a
delay line . 24
Figure 4 – Example of a two parameters envelope for a TRV . 25
Figure 5 – Measurement of the power frequency recovery voltage with striker operation . 27
Figure A.1 – Visualization of the application margin for a given fuse . 41

Table 1 – Nameplate markings . 16
Table 2 – Summary of test parameters for test duties . 29
Table 3 – Comparison between switch-fuse combination and fused circuit-switcher . 37
Table 4 – Comparison between fused circuit-switcher and circuit breaker . 37
Table A.1 – Minimum application margin Am according to fuse characteristic . 44
Table A.2 – Minimum protection time delay . 45
Table A.3 – Examples of possible need for time delay . 45

62271-107 © IEC:2012 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
HIGH-VOLTAGE SWITCHGEAR AND CONTROLGEAR –

Part 107: Alternating current fused circuit-switchers

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
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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
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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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
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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 62271-107 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, published in 2005. It constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition.
– the reference to IEC 60694 has been changed to IEC 62271-1;
– the new clauses and subclauses from IEC 62271-1 have been added and where
necessary new wording has been provided;
• 4.11 Rated filling levels for insulation and/or operation
• 5.19 X-ray emission
• 5.20 Corrosion
– 6 – 62271-107 © IEC:2012
• 6.10 Additional tests on auxiliary and control circuits

• 6.11 X-radiation test procedure for vacuum interrupters

• 12 Influence of the product on the environment

– the normative references have been updated: IEC 60265-1 to IEC 62271-103, IEC 60787

to IEC/TR 60787, IEC 60466 to IEC 62271-201, and IEC/TR 60787 was moved to the

bibliography;
– the figures and tables have been placed in the document where they are first cited;

– the numbering of figures and tables has been changed to obtain the correct order;

– the definition of NSDD was deleted. This definition is included in IEC 62271-1;

– the acceptance criteria have been aligned with 6.101.4 of IEC 62271-103:2011;
– the various provisions expressed about "extension of the validity of type tests" have been
grouped under 6.103: some of the rules were duplicated in Clauses 6 and 8, and it seems
better fitted to deal within each type test sub-clause only with the type test to be
performed. Conditions have not been changed, but the wording is clearer;
– new numbering of subclauses in Clauses 8 and 9 to avoid conflict with clauses from
IEC 62271-1.
The text of this standard is based on the following documents:
FDIS Report on voting
17A/997/FDIS 17A/1004/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 International Standard is to be read in conjunction with IEC 62271-1:2007, 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. Amendments to these clauses and subclauses are given under the same
numbering, whilst additional subclauses, are numbered from 101.
A list of all the parts in the IEC 62271 series, 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 maintenance result 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.
62271-107 © IEC:2012 – 7 –
HIGH-VOLTAGE SWITCHGEAR AND CONTROLGEAR –

Part 107: Alternating current fused circuit-switchers

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 operated units for distribution systems that are
functional assemblies of a circuit-switcher and current-limiting fuses designed so as to be
capable of:
– breaking, at the rated recovery voltage, any load or fault 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.
They are intended to be used for circuits or applications requiring only a normal mechanical
and electrical endurance capability. Such applications cover protection of HV/LV transformers
for instance, but exclude distribution lines or cables, as well as motor circuits and capacitor
bank circuits.
Short-circuit conditions with low currents, up to the fused circuit-switcher rated take-over
current, are dealt with by supplementary devices (strikers, relays, etc.), properly arranged,
tripping the circuit-switcher. Fuses are incorporated in order to ensure that the short-circuit
breaking capacity of the device is above that of the circuit-switcher.
NOTE 1 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 fused circuit-switchers 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. Comparison with other existing switching devices is provided in Clause 8.
NOTE 2 Other circuit-switchers exist; see reference [1] .

Devices that require a dependent manual operation are not covered by this standard.
Fuses are covered by IEC 60282-1.
Earthing switches forming an integral part of a circuit-switcher are covered by IEC 62271-102.
Installation in enclosure, if any, is covered either by IEC 62271-200 or by IEC 62271-201.
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
___________
Numbers between brackets refer to the Bibliography.

– 8 – 62271-107 © IEC:2012
undated references, the latest edition of the referenced document (including any

amendments) applies.
IEC 60282-1:2009, High-voltage fuses – Part 1: Current-limiting fuses

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
IEC 62271-105:—, 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 62271-200, High-voltage switchgear and controlgear – Part 200: AC metal-enclosed
switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV
IEC 62271-201, High-voltage switchgear and controlgear – Part 201: AC insulation-enclosed
switchgear and controlgear for rated voltages above 1 kV and 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 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.
___________
To be published.
62271-107 © IEC:2012 – 9 –
3.4.101
circuit-switcher
mechanical switching device suitable for making, carrying and interrupting currents under

normal circuit conditions and for interrupting specified fault currents that may be less than its

short-time withstand current
.
Note 1 to entry: Other circuit-switchers exist; see reference [1]

3.4.102
fused circuit-switcher
device comprising a three-pole circuit-switcher and three current limiting fuses, capable of

making and breaking any load or fault current up to its short-circuit breaking current, under

TRV and power factor conditions defined in this standard
3.4.103
fused circuit-switcher base
device base
fused circuit-switcher without fuse-links mounted
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
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
[SOURCE: IEC 60050-441: 2007, 441-16-33]
3.5.103
shunt release
release energized by a source of voltage
[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 the fused circuit-switcher)
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 the fused circuit-switcher)
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
[SOURCE: IEC 60050-441: 2007, 441-16-15]

– 10 – 62271-107 © IEC:2012
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

[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
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: 2007, 441-17-04]
3.7.104
prospective breaking current
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
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]

62271-107 © IEC:2012 – 11 –
3.7.108
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]

3.7.109
thermal current
I
th
maximum current carried continuously without the temperature rise of the various parts

exceeding the limits specified

3.7.110
fused short-circuit current
conditional short-circuit current when the current limiting device is a fuse
[SOURCE: IEC 60050-441: 2007, 441-17-21]
3.7.111
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: 2007, 441-17-24]
3.7.112
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]
3.7.113
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]
3.7.114
power frequency recovery voltage
recovery voltage after the transient voltage phenomena have subsided
[SOURCE: IEC 60050-441: 2007, 441-17-27]
3.7.115
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

– 12 – 62271-107 © IEC:2012
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]

3.7.116
minimum opening time (of the fused circuit-switcher)
minimum interval of time between the initiation of the opening, from an external source, and
the first instant of the separation of the arcing contacts in any one pole

3.7.117
fuse-initiated opening time (of a fused circuit-switcher)

time taken from the instant at which arcing in the fuse commences to the instant when the

arcing contacts have separated in all poles
Note 1 to entry: This definition applies only for fused circuit-switchers fitted with fuse-striker release.
3.101 Fuses
3.101.1
fuse-base
fuse mount
fixed part of a fuse provided with contacts and terminals
[SOURCE: IEC 60050-441: 2007, 441-18-02]
3.101.2
striker
mechanical device forming part of a fuse-link which, when the fuse operates, releases the
energy required to cause operation of other apparatus or indicators or to provide interlocking
[SOURCE: IEC 60050-441: 2007, 441-18-18]
3.101.3
cut-off 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: 2007, 441-17-12]
3.101.4
I²t
Joule integral
integral of the square of the current over a given time interval:

t
2 2
I t= i dt
∫
t
2 2
Note 1 to entry: The pre-arcing I t is the I t integral extended over the pre-arcing time of the fuse.
2 2
Note 2 to entry: The operating I t is the I t integral extended over the operating time of the fuse.
Note 3 to entry: The energy in joules liberated in one ohm of resistance in a circuit protected by a fuse is equal to
2 2
the value of the operating I t expressed in A s.
[SOURCE: IEC 60050-441: 2007, 441-18-23]
4 Ratings
Clause 4 of IEC 62271-1:2007 is applicable with the following additions and exceptions.

62271-107 © IEC:2012 – 13 –
In addition to the ratings listed in IEC 62271-1:2007 the following ratings apply:

a) rated short-circuit breaking current;

b) rated transient recovery voltage;

c) rated short-circuit making current;

d) rated take-over current;
e) rated maximal thermal current.

4.1 Rated voltage (U )
r
Subclause 4.1 of IEC 62271-1:2007 is applicable.

4.2 Rated insulation level
Subclause 4.2 of IEC 62271-1:2007 is applicable.
4.3 Rated frequency (f )
r
Subclause 4.3 of IEC 62271-1:2007 is applicable with the following addition.
NOTE In some cases, the rated characteristics of a fused circuit-switcher when used on a 60 Hz system may be
different from its rated characteristics when used on a 50 Hz system.
4.4 Rated normal current and temperature rise
4.4.1 Rated normal current (I )
r
Subclause 4.4.1 of IEC 62271-1:2007 is not applicable.
A rated normal current is normally not assigned to the fused circuit-switcher. When fused
circuit-switchers are combined into larger enclosed assemblies, the rated normal current of
the connecting busbars shall be in accordance with IEC 62271-200 or IEC 62271-201.
See also 4.4.101.
4.4.2 Temperature rise
Subclause 4.4.2 of IEC 62271-1:2007 is applicable with the following addition.
As far as fuses are concerned, Clause 6 of IEC 60282-1: 2009 applies.
4.4.101 Rated maximum thermal current (I )
th
The rated maximum thermal current is the maximum value of the thermal current for the fused
circuit-switcher.
It is not required that the thermal current is selected from the R10 series.
NOTE The actual thermal current depends on the fuses installed.
4.5 Rated short-time withstand current (I )
k
Subclause 4.5 of IEC 62271-1:2007 is not applicable.
4.6 Rated peak withstand current (I )
p
Subclause 4.6 of IEC 62271-1:2007 is not applicable.

– 14 – 62271-107 © IEC:2012
4.7 Rated duration of short circuit (t )
k
Subclause 4.7 of IEC 62271-1:2007 is not applicable.

4.8 Rated supply voltage of closing and opening devices and of auxiliary

and control circuits (U )
a
Subclause 4.8 of IEC 62271-1:2007 is applicable.

4.9 Rated supply frequency of closing and opening devices and of auxiliary circuits

Subclause 4.9 of IEC 62271-1:2007 is applicable.

4.10 Rated pressure of compressed gas supply for controlled pressure systems
Subclause 4.10 of IEC 62271-1:2007 is applicable.
4.11 Rated filling levels for insulation and/or operation
Subclause 4.11 of IEC 62271-1:2007 is applicable.
4.101 Rated short-circuit breaking current I
sc
The rated short-circuit breaking current is the highest prospective short-circuit current which
the fused circuit-switcher shall be capable of breaking under the conditions of use and
behaviour prescribed in this standard in a circuit having a power-frequency recovery voltage
corresponding to the rated voltage of the fused circuit-switcher and having a prospective
transient recovery voltage equal to the rated value specified in 4.102.
The rated short-circuit breaking current is expressed by the r.m.s. value of its a.c. component.
The rated short-circuit breaking currents shall be selected from the R10 series as follows:
8 – 10 – 12,5 – 16 – 20 – 25 – 31,5 – 40 – 50 – 63 – 80 – 100 kA
NOTE 1 It is recognized that the series impedance of the fused circuit-switcher or rapid operation of the fuse or
fused circuit-switcher sometimes causes one or both of the following effects:
a) a reduction of short-circuit current to a value appreciably below that which would otherwise be reached.
b) such rapid operation that the short-circuit current wave is distorted from its normal form.
This is why the term "prospective current" is used when assessing breaking and making performances.
NOTE 2 The
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