IEC 62271-103:2021

IEC 62271-103 ®
Edition 2.0 2021-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
High-voltage switchgear and controlgear –
Part 103: Alternating current switches for rated voltages above 1 kV up to and
including 52 kV
Appareillage à haute tension –
Partie 103: Interrupteurs à courant alternatif pour tensions assignées
supérieures à 1 kV et inférieures ou égales à 52 kV

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform IEC online collection - oc.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews. With a subscription you will always
committee, …). It also gives information on projects, replaced have access to up to date content tailored to your needs.
and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 000 terminological entries in English
details all new publications released. Available online and
and French, with equivalent terms in 18 additional languages.
once a month by email.
Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc
If you wish to give us your feedback on this publication or
need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Recherche de publications IEC - IEC online collection - oc.iec.ch
webstore.iec.ch/advsearchform Découvrez notre puissant moteur de recherche et consultez
La recherche avancée permet de trouver des publications IEC gratuitement tous les aperçus des publications. Avec un
en utilisant différents critères (numéro de référence, texte, abonnement, vous aurez toujours accès à un contenu à jour
comité d’études, …). Elle donne aussi des informations sur adapté à vos besoins.
les projets et les publications remplacées ou retirées.

Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
Le premier dictionnaire d'électrotechnologie en ligne au
Restez informé sur les nouvelles publications IEC. Just
monde, avec plus de 22 000 articles terminologiques en
Published détaille les nouvelles publications parues.
anglais et en français, ainsi que les termes équivalents dans
Disponible en ligne et une fois par mois par email.
16 langues additionnelles. Egalement appelé Vocabulaire

Electrotechnique International (IEV) en ligne.
Service Clients - webstore.iec.ch/csc

Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-nous:
sales@iec.ch.
IEC 62271-103 ®
Edition 2.0 2021-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
High-voltage switchgear and controlgear –

Part 103: Alternating current switches for rated voltages above 1 kV up to and

including 52 kV
Appareillage à haute tension –

Partie 103: Interrupteurs à courant alternatif pour tensions assignées

supérieures à 1 kV et inférieures ou égales à 52 kV

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.130.10 ISBN 978-2-8322-9770-4

– 2 – IEC 62271-103:2021 © IEC 2021
CONTENTS
FOREWORD . 8
1 Scope . 10
2 Normative references . 10
3 Terms and definitions . 11
3.1 General terms and definitions . 11
3.2 Assemblies of switchgear and controlgear . 11
3.3 Parts of assemblies . 11
3.4 Switching devices . 12
3.5 Parts of switchgear and controlgear . 12
3.6 Operational characteristics of switchgear and controlgear . 13
3.7 Characteristic quantities . 13
3.8 Index of definitions . 17
4 Normal and special service conditions . 18
5 Ratings . 18
5.1 General . 18
5.2 Rated voltage (U ) . 18
r
5.3 Rated insulation level (U , U , U ) . 18
d p s
5.4 Rated frequency (f ) . 18
r
5.5 Rated continuous current (I ) . 18
r
5.6 Rated short-time withstand current (I ) . 19
k
5.7 Rated peak withstand current (I ) . 19
p
5.8 Rated duration of short-circuit (t ) . 19
k
5.9 Rated supply voltage of auxiliary circuits and control circuits (U ) . 19
a
5.10 Rated supply frequency of auxiliary and control circuits . 19
5.11 Rated pressure of compressed gas supply for controlled pressure systems . 19
5.101 Rated mainly active load-breaking current (I ) . 19
load
5.102 Rated closed-loop breaking current (I ) . 19
loop
5.103 Rated parallel power transformer breaking current for special purpose
switches (I ) . 19
pptr
5.104 Rated cable-charging breaking current (I ) . 19
cc
5.105 Rated line-charging breaking current (I ) . 19
lc
5.106 Rated single capacitor bank breaking current for special purpose switches
(I ) . 20
sb
5.107 Rated back-to-back capacitor bank breaking current for special purpose
switches (I ) . 20
bb
5.108 Rated back-to-back capacitor bank inrush making current for special
purpose switches (I ) . 20
in
5.109 Rated earth fault breaking current (I ) . 20
ef1
5.110 Rated cable- and line-charging breaking current under earth fault conditions
(I ) . 20
ef2
5.111 Rated motor breaking current for special purpose switches (I ) . 20
mot
5.112 Rated short-circuit making current (I ) . 21
ma
5.113 Types of switches and their associated ratings . 21

5.113.1 Types of switches . 21
5.113.2 Rated making and breaking currents for general purpose switches . 21
5.113.3 Rated making and breaking currents for limited purpose switches . 22
5.113.4 Rated making and breaking currents for special purpose switches . 22
5.113.5 Ratings for switches backed by fuses . 22
5.114 Mechanical endurance class of switches . 23
5.114.1 Class M1 switch . 23
5.114.2 Class M2 switch . 23
5.115 Electrical endurance class of general purpose switches . 23
5.115.1 Class E1 general purpose switch . 23
5.115.2 Class E2 general purpose switch . 23
5.115.3 Class E3 general purpose switch . 23
5.116 Capacitive breaking capability class of switches . 23
5.116.1 General . 23
5.116.2 Class C1 switch . 23
5.116.3 Class C2 switch . 24
6 Design and construction . 24
6.1 Requirements for liquids in switchgear and controlgear . 24
6.2 Requirements for gases in switchgear and controlgear . 24
6.3 Earthing of switchgear and controlgear . 24
6.4 Auxiliary and control equipment and circuits . 24
6.5 Dependent power operation . 24
6.6 Stored energy operation . 24
6.7 Independent unlatched operation (independent manual or power operation) . 24
6.8 Manually operated actuators . 24
6.9 Operation of releases . 24
6.10 Pressure/level indication . 24
6.11 Nameplates. 25
6.11.1 General . 25
6.11.2 Application . 25
6.12 Locking devices . 27
6.13 Position indication . 27
6.14 Degrees of protection provided by enclosures . 27
6.15 Creepage distances for outdoor insulators . 27
6.16 Gas and vacuum tightness . 27
6.17 Tightness for liquid systems . 27
6.18 Fire hazard (flammability) . 27
6.19 Electromagnetic compatibility (EMC) . 28
6.20 X-ray emission . 28
6.21 Corrosion . 28
6.22 Filling levels for insulation, switching and/or operation . 28
6.101 Making and breaking operations . 28
6.102 Requirements for switch-disconnectors . 28
6.103 Mechanical strength . 28
6.104 Securing the position . 28
6.105 Indication and signalling of position . 28
6.105.1 General requirements . 28
6.105.2 Indication of position . 29
6.105.3 Signalling of position by auxiliary contacts . 30

– 4 – IEC 62271-103:2021 © IEC 2021
6.106 No-load transformer breaking . 30
7 Type tests . 30
7.1 General . 30
7.1.1 Basics . 30
7.1.2 Information for identification of test objects . 31
7.1.3 Information to be included in the type-test reports . 31
7.2 Dielectric tests . 31
7.2.9 Artificial pollution tests for outdoor insulators . 31
7.2.10 Partial discharge tests . 31
7.3 Radio interference voltage (RIV) test . 31
7.4 Resistance measurement . 32
7.5 Continuous current tests . 32
7.6 Short-time withstand current and peak withstand current tests . 32
7.6.1 General . 32
7.6.2 Arrangement of the equipment and of the test circuit . 32
7.6.3 Test current and duration . 32
7.6.4 Conditions of the test object after test . 32
7.7 Verification of the protection . 32
7.8 Tightness tests . 32
7.9 Electromagnetic compatibility (EMC) tests . 32
7.10 Additional tests on auxiliary and control circuits . 32
7.10.1 General . 32
7.10.2 Functional tests . 32
7.10.3 Verification of the operational characteristics of auxiliary contacts . 33
7.10.4 Environmental tests . 33
7.10.5 Dielectric test . 33
7.11 X-radiation test for vacuum interrupters . 33
7.101 Making and breaking tests . 33
7.101.1 Test duties for general purpose switches . 33
7.101.2 Test duties for limited purpose switches . 36
7.101.3 Test duties for special purpose switches . 36
7.101.4 Arrangement of the switch for tests . 37
7.101.5 Earthing of test circuit and switch . 38
7.101.6 Test parameters . 38
7.101.7 Test circuits . 41
7.101.8 Behaviour of switch during breaking tests . 56
7.101.9 Condition of switch after breaking tests and short-circuit making tests . 57
7.101.10 Type-test reports . 57
7.102 Mechanical and environmental tests . 59
7.102.1 Miscellaneous provisions for mechanical and environmental tests . 59
7.102.2 Mechanical operation test at ambient air temperature . 60
7.102.3 Low and high temperature tests . 61
7.102.4 Humidity test on auxiliary and control circuits . 65
7.102.5 Operation under severe ice conditions . 67
7.102.6 Tests to verify the proper functioning of the position-indicating device . 67
7.103 Common checks after tests . 68
7.103.1 Checking the capability of the switch to carry its rated continuous
current . 68

7.103.2 Checking the integrity of vacuum in case of a switch using a vacuum
interrupter . 69
8 Routine tests . 70
8.101 General . 70
8.102 Mechanical operating tests . 70
9 Guide to the selection of switchgear and controlgear (informative) . 70
9.101 General . 70
9.102 Conditions affecting application . 70
9.103 Insulation coordination . 71
9.104 Selection of class of switch . 71
9.104.1 General purpose switch . 71
9.104.2 Limited purpose switch . 71
9.104.3 Special purpose switch . 71
9.105 Tests for special applications . 71
10 Information to be given with inquiries, tenders and orders (informative) . 71
10.1 General . 71
10.2 Information with inquiries and orders. 72
10.3 Information with tenders . 72
11 Transport, storage, installation, operating instructions and maintenance. 73
12 Safety . 73
13 Influence of the product on the environment . 73
Annex A (normative) Tolerances on test quantities for type tests . 74
Annex B (informative) Explanation of the determination for the value of I and I . 76
ef1 ef2
B.1 Usage of rating I and I . 76
ef1 ef2
B.1.1 General . 76
B.1.2 Isolated neutral system . 76
B.1.3 High impedance earthed neutral systems . 78
B.1.4 Resonant earthed neutral systems (Petersen coil) . 79
B.1.5 Synthesis . 80
B.2 Calculation of I and I . 81
ef1 ef2
B.2.1 General . 81
B.2.2 Calculation of I . 84
ef1
B.2.3 Calculation of I . 84
ef2
Annex C (informative) List of notes concerning certain countries . 86
Bibliography . 87

Figure 1 – Position-indicating/signalling device(s) . 29
Figure 2 – Three-phase test circuit for mainly active load current switching for test
duty TD . 42
load
Figure 3 – Single-phase test circuit for mainly active load current switching for test
duty TD . 43
load
Figure 4 – Three-phase test circuit for distribution line closed-loop and parallel
transformer current switching test for test duties TD and TD . 45
loop pptr
– 6 – IEC 62271-103:2021 © IEC 2021
Figure 5 – Single-phase test circuit for distribution line closed-loop and parallel
transformer current switching test, for test duties TD and TD . 45
loop pptr
Figure 6 – General test circuit for three- and single-phase capacitive switching tests . 51
Figure 7 – Prospective recovery voltage and related specified parameter values for
capacitive current breaking tests . 53
Figure 8 – Three-phase test circuit for earth fault breaking current tests, for test
duty TD . 54
ef1
Figure 9 – Three-phase test circuit for cable-charging breaking current tests under
earth fault conditions, for test duty TD . 55
ef2
Figure 10 – Three-phase test circuit for short-circuit making current test for test
duty TD . 55
ma
Figure 11 – Single-phase test circuit for short-circuit making current test for test
duty TD . 56
ma
Figure 12 – Test sequences for low and high temperature tests . 62
Figure 13 – Humidity test . 66
Figure B.1 – Earth fault in isolated neutral system . 76
Figure B.2 – Capacitive current in non-faulty phases of isolated neutral system . 78
Figure B.3 – Earth fault in high impedance earthed neutral system . 79
Figure B.4 – Earth fault in resonant or compensate earthed neutral system . 80
Figure B.5 – Example of sequence to find and isolate a faulty branch in an overhead
network . 82
Figure B.6 – Example of sequence to find and isolate a faulty branch in a cable
network . 83

Table 1 – Preferred values of rated line- and cable-charging breaking currents for
general purpose switches . 22
Table 2 – Nameplate information . 25
Table 3 – Test duties for general purpose switches – Test duties for three-phase tests
on three-pole operated, general purpose switches . 34
Table 4 – Test duties for general purpose switches – Single-phase tests on three-pole
general purpose switches operated pole-after-pole and single-pole general purpose
switches applied on three-phase systems . 34
Table 5 – Test duties for special purpose switches – Three-phase tests on three-pole
operated switches . 36
Table 6 – Test duties for special purpose switches – Single-phase tests on three-pole
switches operated pole-after-pole and single-pole switches applied on three-phase
systems . 37
Table 7 – Summary of the conditions for combining tests and alternative procedures . 39
a
Table 8 – Supply circuit TRV parameters for mainly active load current breaking tests . 43
Table 9 – TRV parameters for distribution line closed loop breaking tests . 46
Table 10 – TRV parameters for parallel power transformer breaking current tests . 47
Table 11 – Prospective recovery voltage parameter limits for capacitive current
breaking tests . 53
Table A.1 – Tolerances on test quantities for type tests . 74
Table B.1 – Need of ratings I and I in non-effectively earthed neutral systems . 80
ef1 ef2
Table B.2 – Values relating to the examples in Figure B.5 and Figure B.6 for
capacitance and capacitive current for cables and overhead lines [6], [10], [11] . 85

Table B.3 – Values for I . 85
ef2
– 8 – IEC 62271-103:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HIGH-VOLTAGE SWITCHGEAR AND CONTROLGEAR –

Part 103: Alternating current switches for rated voltages
above 1 kV up to and including 52 kV

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC Publication(s)"). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC 62271-103 has been prepared by subcommittee 17A: Switching devices, of IEC technical
committee 17: High-voltage switchgear and controlgear. It is an International Standard.
This second edition cancels and replaces the first edition published in 2011. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) this document has been aligned with IEC 62271-1:2017 and IEC 62271-102:2018;
b) clarifications regarding the behaviour of the switch during breaking tests regarding current
interruption and restrikes have been added;
c) conditions of the switch after making and breaking tests have been clarified;
d) a new informative Annex B intended to provide guidance for the calculation of I and I
ef1 ef2
has been added;
e) new rules for the combination of 50 Hz and 60 Hz switching tests have been defined and a
new table (Table 7) has been added;
f) tests with specified TRV have been modified to be in accordance with the practice described
in IEC 62271-100;
g) the behaviour of the switch during breaking tests has been clarified and boundaries for
restrike allowance have been defined;
h) explanations for short-circuit making tests have been added;
i) vacuum integrity check after mechanical operations has been defined;
j) all test voltages for single-phase capacitive testing have been grouped under 7.101.7.3.2
and have been confirmed by simulation and calculation.
The text of this International Standard is based on the following documents:
Draft Report on voting
17A/1297/FDIS 17A/1303/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
This document is to be read in conjunction with IEC 62271-1:2017, to which it refers and which
is applicable unless otherwise specified. In order to simplify the indication of corresponding
requirements, the same numbering of clauses and subclauses is used as in IEC 62271-1:2017.
Amendments to these clauses and subclauses are given under the same numbering whilst
additional subclauses are numbered from 101.
A list of all parts in the IEC 62271 series, published under the general title High-voltage
switchgear and controlgear, can be found on the IEC website.
The reader's attention is drawn to the fact that Annex C lists all of the "in-some-country" clauses
on differing practices of a less permanent nature relating to the subject of this document.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document 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.

– 10 – IEC 62271-103:2021 © IEC 2021
HIGH-VOLTAGE SWITCHGEAR AND CONTROLGEAR –

Part 103: Alternating current switches for rated voltages
above 1 kV up to and including 52 kV

1 Scope
This part of IEC 62271 is applicable to three-phase, alternating current switches and switch-
disconnectors for their switching function, having making and breaking current ratings, for
indoor and outdoor installations, for rated voltages above 1 kV up to and including 52 kV and
for rated frequencies from 16 2/3 Hz up to and including 60 Hz. This document is also applicable
to single-pole switches used on three-phase systems.
This document is also applicable to the operating devices of these switches and to their auxiliary
equipment.
For switch-disconnectors, refer also to IEC 62271-102 for their disconnecting function.
Devices not covered by this document are:
– devices that require a dependent manual operation;
– earthing switches. Earthing switches forming an integral part of a switch are covered by
IEC 62271-102;
– switching devices attached as an element of a high-voltage fuse assembly or its mounting
and operated by opening and closing the fuse assembly.
General principles and provisions of this document can also be applicable to single pole
switches intended for application in single-phase systems, the requirements for dielectric tests
and making and breaking tests being in accordance with the requirements of the specific
application.
This document establishes requirements for general, limited and special purpose switches used
in distribution systems.
NOTE Except where special clarification is required, the term "switch" is used to refer to all kinds of switches and
switch-disconnectors within the scope of this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60050-441, International Electrotechnical Vocabulary (IEV) – Part 441: Switchgear,
controlgear and fuses (available at http://www.electropedia.org)
IEC 60529:1989, Degrees of protection provided by enclosures (IP Code)
IEC 60529:1989/AMD1:1999
IEC 60529:1989/AMD1:2013
IEC 62262:2002, Degrees of protection provided by enclosures for electrical equipment against
external mechanical impacts (IK code)

IEC 62271-1:2017, High-voltage switchgear and controlgear – Part 1: Common specifications
for alternating current switchgear and controlgear
IEC 62271-102:2018, High-voltage switchgear and controlgear – Part 102: Alternating current
disconnectors and earthing switches
IEC 62271-110:2017, High-voltage switchgear and controlgear – Part 110: Inductive load
switching
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-441 and
IEC 62271-1 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
NOTE Terms and definitions are classified in accordance with IEC 62271-1:2017.
3.1 General terms and definitions
Subclause 3.1 of IEC 62271-1:2017 is applicable with the following additions:
3.1.101
effectively earthed neutral system
system earthed through a sufficiently low impedance such that for all system conditions the
ratio of the zero-sequence reactance to the positive-sequence reactance (X /X ) is positive and
0 1
less than 3, and the ratio of the zero-sequence resistance to the positive-sequence reactance
(R /X ) is positive and less than 1
0 1
Note 1 to entry: Normally such systems are solidly earthed (neutral) systems or low impedance earthed (neutral)
systems.
Note 2 to entry: The earthing conditions depend not only on the physical earthing conditions around the relevant
location but also on the total system.
3.1.102
non-effectively earthed neutral system
system other than effectively earthed neutral system, not meeting the conditions given in
3.1.101
Note 1 to entry: Normally such systems are isolated neutral systems, high impedance earthed (neutral) systems or
resonant earthed (neutral) systems
Note 2 to entry: The earthing conditions depend not only on the physical earthing conditions around the relevant
location but also on the total system.
3.2 Assemblies of switchgear and controlgear
Subclause 3.2 of IEC 62271-1:2017 applies.
3.3 Parts of assemblies
Subclause 3.3 of IEC 62271-1:2017 applies.

– 12 – IEC 62271-103:202
...