SIST-TP CLC IEC/TR 62271-307:2019

SLOVENSKI STANDARD
01-oktober-2019
Visokonapetostne stikalne in krmilne naprave - 307. del: Navodilo za podaljšanje
veljavnosti preskusov tipa za izmenične (AC) stikalne in krmilne naprave v
kovinskih ohišjih in ohišjih iz trdih izolacijskih materialov za naznačene napetosti
nad 1 kV do vključno 52 kV (CLC IEC/TR 62271-307:2019)
High-voltage switchgear and controlgear - Part 307: Guidance for the extension of
validity of type tests of AC metal and solid-insulation enclosed switchgear and
controlgear for rated voltages above 1 kV and up to and including 52 kV (CLC IEC/TR
62271-307:2019)
Hochspannungs-Schaltgeräte und -Schaltanlagen - Teil 307: Leitfaden für die
Erweiterung des Geltungsbereichs von Typprüfungen von metall- und
isolierstoffgekapselten Wechselstrom-Schaltanlagen für Bemessungsspannungen über 1
kV und bis einschließlich 52 kV (CLC IEC/TR 62271-307:2019)
Appareillage à haute tension - Partie 307: Lignes directrices pour l'extension de validité
des essais de type d'appareillages en courant alternatif sous enveloppe métallique et
d’isolation solide pour tensions assignées supérieures à 1 kV et jusqu'à 52 kV inclus
(CLC IEC/TR 62271-307:2019)
Ta slovenski standard je istoveten z: CLC IEC/TR 62271-307:2019
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.

TECHNICAL REPORT CLC IEC/TR 62271-307

RAPPORT TECHNIQUE
TECHNISCHER BERICHT
July 2019
ICS 29.130.10
English Version
High-voltage switchgear and controlgear - Part 307: Guidance
for the extension of validity of type tests of AC metal and solid-
insulation enclosed switchgear and controlgear for rated
voltages above 1 kV and up to and including 52 kV
(IEC/TR 62271-307:2015)
Appareillage à haute tension - Partie 307: Lignes directrices Hochspannungs-Schaltgeräte und -Schaltanlagen - Teil
pour l'extension de validité des essais de type 307: Leitfaden für die Erweiterung des Geltungsbereichs
d'appareillages en courant alternatif sous enveloppe von Typprüfungen von metall- und isolierstoffgekapselten
métallique et d'isolation solide pour tensions assignées Wechselstrom-Schaltanlagen für Bemessungsspannungen
supérieures à 1 kV et jusqu'à 52 kV inclus über 1 kV und bis einschließlich 52 kV
(IEC/TR 62271-307:2015) (IEC/TR 62271-307:2015)

This Technical Report was approved by CENELEC on 2019-06-17.

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,
Turkey 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
© 2019 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. CLC IEC/TR 62271-307:2019 E

European foreword
This document (CLC IEC/TR 62271-307:2019) consists of the text of IEC/TR 62271-307:2015
prepared by SC 17C "Assemblies" of IEC/TC 17 "High-voltage switchgear and controlgear".
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.

Endorsement notice
The text of the International Standard IEC/TR 62271-307:2015 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 standards
indicated:
IEC 60865-1 NOTE Harmonized as EN 60865-1
IEC 60071-1:2006 NOTE Harmonized as EN 60071-1:2006 (not modified)
IEC 60071-1:2006/A1:2010 NOTE Harmonized as EN 60071-1:2006/A1:2010 (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.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60050-441 1984 International Electrotechnical Vocabulary. - -
Switchgear, controlgear and fuses
+ A1 2000  - -
IEC 62271-1 2007 High-voltage switchgear and controlgear -- EN 62271-1 2008
Part 1: Common specifications
+ A1 2011  + A1 2011
IEC 62271-200 2011 High-voltage switchgear and controlgear - EN 62271-200 2012
Part 200: AC metal-enclosed switchgear
and controlgear for rated voltages above 1
kV and up to and including 52 kV
IEC 62271-201 2014 High-voltage switchgear and controlgear - EN 62271-201 2014
Part 201: AC solid-insulation enclosed
switchgear and controlgear for rated
voltages above 1 kV and up to and
including 52 kV
IEC TR 62271-307 ®
Edition 1.0 2015-09
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
colour
inside
High-voltage switchgear and controlgear –

Part 307: Guidance for the extension of validity of type tests of AC metal and

solid-insulation enclosed switchgear and controlgear for rated voltages above

1 kV and up to and including 52 kV

Appareillage à haute tension –

Partie 307: Lignes directrices pour l'extension de validité des essais de type

d'appareillages en courant alternatif sous enveloppe métallique et d’isolation

solide pour tensions assignées supérieures à 1 kV et jusqu'à 52 kV inclus

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.130.10 ISBN 978-2-8322-2903-3

– 2 – IEC TR 62271-307:2015  IEC 2015
CONTENTS
FOREWORD . 5
1 General . 7
1.1 Scope . 7
1.2 Normative references . 7
2 Terms and definitions . 7
3 Use of extension criteria . 9
3.1 General . 9
3.2 Parameters for extension criteria . 10
3.3 Use of calculations . 10
3.3.1 General . 10
3.3.2 Temperature rise calculations . 11
3.3.3 Electric field calculations . 11
3.3.4 Mechanical stress calculations. 11
3.3.5 Short-circuit current calculations . 11
3.3.6 Internal arc pressure rise calculations . 12
3.4 Information needed for extension of type test validity . 12
4 Application of extension criteria . 12
4.1 Dielectric tests . 12
4.2 Temperature rise tests . 13
4.3 Mechanical tests . 15
4.4 Short-time and peak withstand current tests . 15
4.5 Making and breaking tests . 16
4.6 Internal arc fault tests . 17
4.6.1 General . 17
4.6.2 Extension criteria with respect to design . 17
4.6.3 Extension criteria with respect to ratings and installation conditions . 18
5 Extending the validity of type tests . 19
5.1 General . 19
5.2 Extension of validity of a test report to other functional units (situation a) . 20
5.3 Validation of a family by selection of test objects (situation b) . 21
5.3.1 General . 21
5.3.2 Mapping of the family . 21
5.3.3 Specification of test objects . 22
5.4 Validation of an assembly by existing test reports (situation c) . 22
5.5 Validation of a design modification (situation d) . 23
Annex A (informative) Rationale for the extension criteria . 24
A.1 General . 24
A.2 Dielectric tests . 24
A.2.1 General . 24
A.2.2 Clearances (Items 1 and 2) . 24
A.2.3 Insulating supports and material (Items 3 and 4) . 24
A.2.4 Live parts (Items 5 and 6) . 25
A.2.5 Open contact gap and isolating distance (Items 7 and 8) . 25
A.2.6 Minimum functional pressure for insulation (Item 9) . 25
A.3 Temperature rise tests . 25
A.3.1 General . 25

IEC TR 62271-307:2015  IEC 2015 – 3 –
A.3.2 Centre distance between phase conductors (Item 1) . 26
A.3.3 Phase to earth distance (Item 2) . 26
A.3.4 Enclosure and compartment volume (Item 3) . 26
A.3.5 Insulating gas (Item 4) . 27
A.3.6 Conductors (Items 5 and 6) . 27
A.3.7 Conductor joints and connections (Items 7, 8 and 9) . 27
A.3.8 Ventilation area of partitions and enclosure (Item 10) . 27
A.3.9 Power dissipation of components (Item 11) . 28
A.3.10 Insulating barriers (Item 12) . 28
A.3.11 Insulating coating of conductors and enclosures (Item 13 and 14) . 28
A.3.12 Insulating material in contact with conductors (Item 15) . 29
A.4 Mechanical tests . 29
A.4.1 General . 29
A.4.2 Shutter systems (Item 1) . 29
A.4.3 Contacts of removable parts (Item 2) . 30
A.4.4 Interlocking systems (Items 3 and 4). 30
A.5 Short-time and peak withstand current tests . 30
A.5.1 General . 30
A.5.2 Centre distance between phase conductors (Item 1) . 31
A.5.3 Conductors (Items 2, 5 and 6). 31
A.5.4 Insulating conductor supports (Items 3 and 4) . 31
A.5.5 Insulating material in contact with conductors (Item 7) . 32
A.5.6 Enclosure, partitions or bushings (Item 8) . 32
A.5.7 Contacts of removable part (Item 9) . 32
A.6 Making and breaking tests . 32
A.6.1 General . 32
A.6.2 Clearance between phases and to earth (Items 1 and 2) . 33
A.6.3 Enclosure and compartment volume (Item 3) . 33
A.6.4 Insulating gas (Item 4) . 33
A.6.5 Conductors (Items 5 and 6) . 33
A.6.6 Insulating supports (Items 7, 8 and 9) . 33
A.7 Internal arc fault tests . 34
A.7.1 General . 34
A.7.2 Clearance between phases and to earth (Items 1 and 2) . 34
A.7.3 Compartment volume (Item 3) . 34
A.7.4 Pressure of insulating gas (Item 4) . 35
A.7.5 Material in the region of arc initiation (Items 5, 6, 7 and 8) . 35
A.7.6 Pressure relief opening devices (Items 9, 10 and 11) . 35
A.7.7 Enclosure and compartments (Items 12, 13, 14 and 15) . 36
A.8 Rationale for extension criteria with respect to arc fault ratings and
installation conditions . 36
A.8.1 General . 36
A.8.2 Rated arc fault current and duration (items 1 and 2) . 36
A.8.3 Rated voltage (item 3) . 36
A.8.4 Rated frequency (item 4) . 37
A.8.5 Arrangement of assembly (items 5, 6 and 7) . 37
A.8.6 Indoor or outdoor installation (item 8) . 37
A.8.7 Type of accessibility (item 9) . 37
A.8.8 Accessible sides (item 10) . 37

– 4 – IEC TR 62271-307:2015  IEC 2015
Annex B (informative) Examples for the extension of validity of type tests . 38
B.1 General . 38
B.2 Design modification of a cable terminal in air insulated switchgear (AIS). 38
B.3 Design modification of an AIS bus riser functional unit by adding current
transformers . 39
B.4 Design modification of a key-lock in the door of a functional unit of AIS . 41
B.5 Extension of a ring-main unit (GIS) to functional units with larger width. 41
B.6 Extension of a family of gas insulated switchgear (GIS) by a functional unit . 43
Bibliography . 46

Figure 1 – Extension of validity of one test report; situation a) . 20
Figure 2 – Validation of a family by selection of appropriate test objects; situation b) . 21
Figure 3 – Validation of actual assembly with existing test reports; situation c) . 23
Figure B.1 – Cable terminals in the connection compartment of air insulated switchgear. 38
Figure B.2 – Addition of block-type current transformers into the bus riser functional
unit of air insulated switchgear . 40
Figure B.3 – Special type of key-lock as replacement for a standard key-lock in the
door of air insulated switchgear . 41
Figure B.4 – Front view and top cross sectional view of a combination of functional
units making up a ring-main unit . 42
Figure B.5 – Cross-section of two different functional units of GIS . 44

Table 1 – Examples of design parameters. 10
Table 2 – Extension criteria for dielectric withstand performance . 13
Table 3 – Extension criteria for temperature rise performance . 14
Table 4 – Extension criteria for mechanical performance . 15
Table 5 – Extension criteria for short-time and peak withstand current performance . 16
Table 6 – Extension criteria for making and breaking capacity . 17
Table 7 – Extension criteria for internal arc fault withstand performance . 18
Table 8 – Extension criteria for internal arc fault classification with respect to
installation conditions . 19
Table B.1 – Affirmation of extension criteria with respect to dielectric withstand
performance of a functional unit . 39
Table B.2 – Affirmation of extension criteria with respect to short-time current
withstand performance of a functional unit . 40
Table B.3 – Affirmation of extension criteria with respect to temperature rise
performance of a ring-main-unit . 43
Table B.4 – Affirmation of extension criteria with respect to internal arc classification of
a GIS circuit-breaker compartment . 44

IEC TR 62271-307:2015  IEC 2015 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HIGH-VOLTAGE SWITCHGEAR AND CONTROLGEAR –

Part 307: Guidance for the extension of validity of type tests of
AC metal and solid-insulation enclosed switchgear and controlgear
for rated voltages above 1 kV and 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.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC TR 62271-307, which is a technical report, has been prepared by subcommittee 17C:
Assemblies, of IEC technical committee 17: High-voltage switchgear and controlgear.
This Technical Report is to be read in conjunction with IEC 62271-200 published in 2011 and
IEC 62271-201 published in 2014.

– 6 – IEC TR 62271-307:2015  IEC 2015
The text of this Technical Report is based on the following documents:
Enquiry draft Report on voting
17C/625/DTR 17C/632/RVC
Full information on the voting for the approval of this Technical Report 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.
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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
IEC TR 62271-307:2015  IEC 2015 – 7 –
HIGH-VOLTAGE SWITCHGEAR AND CONTROLGEAR –

Part 307: Guidance for the extension of validity of type tests of
AC metal and solid-insulation enclosed switchgear and controlgear
for rated voltages above 1 kV and up to and including 52 kV

1 General
1.1 Scope
This Part of IEC 62271, which is a Technical Report, refers to prefabricated metal-enclosed
and solid-insulation enclosed (both hereinafter called enclosed) switchgear and controlgear
assemblies for alternating current of rated voltages above 1 kV and up to and including 52 kV
as specified in IEC 62271-200 and IEC 62271-201, and to other equipment included in the
same enclosure with any possible mutual influence.
This Technical Report may be used for the extension of the validity of type tests performed on
one test object with a defined set of ratings to another switchgear assembly of the same
family with a different set of ratings or different arrangements of components. It supports the
selection of representative test objects composed of functional units of a family of switchgear
and controlgear aimed at the optimization of type tests in order to perform a consistent
conformity assessment.
This Technical Report utilises a combination of sound technical and physical principles,
manufacturer and user experience and calculations to establish guidance for the extension of
validity of type tests, covering various design and rating aspects.
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.
IEC 60050-441:1984, International Electrotechnical Vocabulary. Switchgear, controlgear and
fuses
IEC 60050-441:1984/AMD1:2000
IEC 62271-1:2007, High-voltage switchgear and controlgear – Part 1: Common specifications
IEC 62271-1:2007/AMD1:2011
IEC 62271-200:2011, 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 62271-201:2014, High-voltage switchgear and controlgear – Part 201: AC solid-insulation
enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including
52 kV
2 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-441,
IEC 62271-1, IEC 62271-200, IEC 62271-201, as well as the following apply.
NOTE Some standard terms and definitions are recalled here for ease of reference.

– 8 – IEC TR 62271-307:2015  IEC 2015
2.101
switchgear and controlgear
general term covering switching devices and their combination with associated control,
measuring, protective and regulating equipment, also assemblies of such devices and
equipment with associated interconnections, accessories, enclosures and supporting
structures
[SOURCE: IEC 60050-441:1984, 441-11-01]
2.102
family of switchgear and controlgear
functional units designed to be physically combined in assemblies and providing a range of
ratings and characteristics (e.g. current, voltage, degree of protection)
2.103
functional unit (of an assembly)
a part of an assembly of switchgear and controlgear comprising all the components of the
main circuits and auxiliary circuits that contribute to the fulfilment of a single function
Note 1 to entry: Functional units may be distinguished according to the function for which they are intended e.g.:
incoming unit, through which electrical energy is normally fed into the assembly, outgoing unit through which
electrical energy is normally supplied to one or more external circuits.
[SOURCE: IEC 60050-441:1984, 441-13-04]
2.104
assembly (of switchgear and controlgear)
a combination of switchgear and/ or controlgear completely assembled with all internal
electrical and mechanical interconnections
Note 1 to entry: An assembly is comprised of one or more functional units
[SOURCE: IEC 60050-441:1984, 441-12-01, modified – addition of a note to entry.]
2.105
component
essential part of the high voltage or earthing circuits of metal and solid-insulation enclosed
switchgear and controlgear which serves a specific function
Note 1 to entry: Examples of components include: circuit-breaker, disconnector, switch, fuse, instrument
transformer, bushing, bus-bar.
[SOURCE: IEC 62271-200:2011, 3.113, modified – rephrasing of the definition and addition of
a note to entry.]
2.106
main circuit
all the high voltage conductive parts of metal and solid-insulation enclosed switchgear and
controlgear included in a circuit which is intended to carry the rated normal current
[SOURCE: IEC 60050-441:1984, 441-13-02, modified – rephrasing of the definition.]
2.107
test object
item submitted to a test, including any accessories, unless otherwise specified
[SOURCE: IEC 60050-151:2001, 151-16-28]

IEC TR 62271-307:2015  IEC 2015 – 9 –
2.108
extension (of validity) criterion
criterion based on the design parameters, which can be applied to validate the performance of
an untested assembly based on the positive results of a test performed on another assembly
for a specific characteristic
2.109
homogeneous group
group of functional units of a family of switchgear and controlgear having design parameters
which allows for a specific characteristic extending the validity of the result of a type test
performed on one member of the group to the rest of the group
2.110
clearance
the distance between two conductive parts along a string stretched the shortest way between
these conductive parts
[SOURCE: IEC 60050-441:1984, 441-17-31]
2.111
clearance between phases
the clearance between any conductive parts of adjacent phases
[SOURCE: IEC 60050-441:1984, 441-17-32; modified – modification of the term.]
2.112
clearance to earth
the clearance between any conductive parts and any parts which are earthed or intended to
be earthed
[SOURCE: IEC 60050-441:1984, 441-17-33]
2.113
centre distance between phases
distance between the centres of adjacent phase conductors
3 Use of extension criteria
3.1 General
Because of the variety of types of functional units, ratings and possible combinations of
components, it is not practical to perform type tests with all the possible assemblies of
enclosed switchgear and controlgear. Therefore, the performance of a particular assembly
may be evaluated by reference to type test reports of other assemblies of the same family of
switchgear and controlgear. Subclauses 4.1 to 4.6 provide for each kind of type test (or
characteristic) a non-exhaustive list of design parameters, which should be analysed for
extension of validity.
The analysis should be based on sound technical and physical principles and may be
supported by calculations, if applicable.
Each design parameter of the assembly to be assessed listed in the respective column of the
tables in 4.1 to 4.6 should be compared with the design parameter of the already type tested
assembly applying the acceptance criteria provided in the same tables. The affirmation of
every extension criterion allows a test performed on one assembly having specific
characteristics to be applied to another assembly of the same family with different
characteristics (e.g. some of the ratings or dimensions). For example, the affirmation of

– 10 – IEC TR 62271-307:2015  IEC 2015
item (1) in Table 2 reads: the clearance between phases of the assessed assembly is larger
or equal the clearance between phases of the tested assembly.
If any of the extension criteria cannot be affirmed, further evidence is required e.g. by
technical arguments, calculation /simulation or specific tests. Calculations can only be applied
in a comparative sense as indicated in 3.3.
3.2 Parameters for extension criteria
The criteria for the extension of type tests available for a family of switchgear and controlgear
depend on a number of design parameters such as the ones listed in Table 1. Every assembly
is characterized by its own set of design parameters.
Component parameters are design and operating parameters that influence the capability of
the component with respect to its own ratings. These parameters are controlled and specified
by the manufacturer of the component. All applications of a component within a family of
switchgear and controlgear should meet the manufacturer’s specified tolerances for
component parameters. The extension of validity of type tests according to a component
standard is outside the scope of this Technical Report.
NOTE Some switching devices, such as earthing switches, may not be available as a separate component and
need to be tested inside an assembly according to their relevant component standards.
Table 1 – Examples of design parameters
Design parameter Related to
Raw material of a contact in a switching device Component
Geometry of a contact in a switching device Component
Opening and closing speed of a switching device Component
Allowable rebound time of a switching device Component
Clearance between phases Component / assembly
Clearance to earth Component / assembly
Pressure of insulating gas in a compartment Component / assembly
Insulation class of all insulation parts in contact with conductors Component / assembly
Length of unsupported section of bus-bar Assembly
Arrangement of components Assembly
NOTE This table includes examples only; it is not intended to be complete

Assembly parameters are those parameters that are directly influenced by the design of an
assembly of a family of switchgear and controlgear, however, they may depend on component
parameters. Assembly parameters are considered within the scope of this Technical Report.
3.3 Use of calculations
3.3.1 General
For the purpose of this Technical Report, calculations and simulations may only be applied in
a comparative sense using calculation results available for a type tested assembly and results
obtained for another assembly that is under investigation. The comparison is always based on
the design parameters and the acceptance criteria in Tables 2 to 7.
In many cases the performance of a given assembly, with respect to a particular type test,
cannot be evaluated by a single value of a design parameter due to the complexity of the
design. For example, the clearance between phase conductors might vary considerably along
the current path. Calculations have the potential to compare the respective design parameter
with spatial resolution supporting a comparison using technical arguments and expertise.

IEC TR 62271-307:2015  IEC 2015 – 11 –
Depending on the type test and the particular design parameter, sometimes a simple model of
the relevant switchgear might be sufficient using an analytical or empirical formula, and
sometimes a complete three-dimensional simulation model might be required using a complex
numerical tool provided the results of the simulation tool are consistent and repeatable.
The validation of software tools and calculation methods themselves is outside the scope of
this Technical Report. Some of these calculation methods are briefly mentioned below with
their particular characteristics.
3.3.2 Temperature rise calculations
The Technical Report IEC TR 60890 [1] provides calculation procedures for low voltage
assemblies, which could also be applied to high voltage switchgear assemblies having regard
to the particular limitations of this calculation method. The calculation is done in dependence
of the total power generated inside, the area of enclosure walls and their mounting conditions,
the number of horizontal partitions, and the area of ventilation openings. The temperature of
air inside the tested compartment is the parameter to compare.
For complex geometries, a comparison may be performed by thermal networks, where the
whole assembly with all components is divided into discrete elements built from heat
generating resistors and heat conducting and convection elements. Also, more complex CFD
tools (computational fluid dynamics) may be applied requiring a complete 3-dimensional
model of the switchgear.
3.3.3 Electric field calculations
The dielectric withstand performance of two assemblies may be assessed by an electric field
simulation of both designs comparing the resulting electric field strengths. Finite element (FE)
or finite volume (FV) software tools exist, which allow simulating even complex three-
dimensional geometries. A CIGRE publication [2] concludes in particular with respect to
electric field calculations: “Simulation is an excellent and instructive tool… to predict
performance, where performance is proven by tests on similar designs (interpolation)“.
It may be remarked that this Technical Report does not provide information for extrapolation
but only for interpolation of characteristics, e.g. extending validity to higher values of electric
field strengths is not covered.
3.3.4 Mechanical stress calculations
Simulation software for operating mechanisms exists and can give information on the
mechanical stress on parts of the mechanism. However, it is not feasible to assess the
mechanical endurance by these programs. Therefore at the present state of available
simulation software, it is not recommended to use simulations for the extension of validity of
mechanical type tests. Nevertheless, the strength of single parts or mechanical supports may
be assessed by such calculations.
3.3.5 Short-circuit current calculations
With respect to the short-time current withstand performance, guidance and calculation
formulas for bus-bar designs can be found in a guideline on short-circuit withstand of low
voltage assemblies [3, 4, 5]. This includes the determination of mutual electromagnetic forces
between phase conductors and the resulting mechanical stress which is able to bend bus-bar
conductors and damage insulators. The mechanical stress on bus-bars and forces on the
supports may be assessed through stress analysis programs, when applying the calculated
t might be
electro-magnetic forces. Additionally, a calculation of the thermal stress using I
k k
done when the assessment is made for a lower I and higher t than the ones tested.
k k
______________
Numbers in square brackets refer to the Bibliography.

– 12 – IEC TR 62271-307:2015  IEC 2015
3.3.6 Internal arc pressure rise calculations
The comparison of the pressure withstand performance of two assemblies may be
substantiated by pressure rise calculations for the compartments under investigation [6]. The
calculations are able to provide the pressure rise in the compartments under consideration of
the opening of pressure relief devices. An assessment of the strength of the enclosure walls
under the pressure stress can be made for simple geometries using calculation formula,
otherwise using finite element mechanical stress analysis.
The flow of hot gases expelled from the compartment may be simulated by CFD programs,
however, it is, at the time of the publication of this Technical Report, not possible to simulate
the ignition of indicators, which is an important acceptance criterion in the type test. Therefore
such programs have limited applications for the extension of type test validity.
3.4 Information needed for extension of type test validity
For the extension of type test validity, similar information on the assembly under evaluation
should be collected as is required for type test objects according to IEC 62271-1:2007, 6.1.3.
In addition, the tables given in Clause 4 should be used to provide for each characteristic i.e.
type test relevant information on design parameters of the tested object and of the functional
units under evaluation. Only the tables that are relevant for the characteristic under evaluation
need to be used.
The applicable type test reports of the tested assembly should be provided as f
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