SIST EN IEC 60071-11:2023
(Main)Insulation co-ordination - Part 11：Definitions, principles and rules for HVDC system
Insulation co-ordination - Part 11：Definitions, principles and rules for HVDC system
IEC 60071-11:2022 applies to high-voltage direct current (HVDC) systems. It specifies the principles on the procedures for the determination of the specified withstand voltages, creepage distance and air clearances for the equipment and the installations of these systems.
This document gives the insulation co-ordination principles related to line commutated converter (LCC) and voltage sourced converters (VSC) HVDC systems. The main principles of this document also apply to other special converter configurations of LCC, such as the capacitor commutated converter (CCC) as well as the controlled series compensated converter (CSCC), etc.
This document applies to insulation co-ordination of equipment connected between the converter AC bus (including the AC harmonic filters, the converter transformer, the circuit breakers) and the DC line side. The line and cable terminations in so far as they influence the insulation co-ordination of converter station equipment are also covered.
This document applies only for HVDC applications in power systems and not for industrial conversion equipment. Principles and guidance given are for insulation co-ordination purposes only. The requirements for human safety are not covered by this document.
This international standard replaces, in conjunction with IEC 60071-12, IEC 60071-5 published in 2014.
This edition includes the following significant technical changes with respect to IEC 60071‑5:2014:
- This standard applies to both LCC and VSC HVDC systems whereas IEC 60071-5 only dealt with LCC HVDC system;
- Annex C (normative) gives the recommended specified withstand voltage (LI and SI);
- Annex C (normative) gives the minimum air clearances;
- Annex E shows the correlation of clauses between this standard and IEC 60071-5:2014.
Isolationskoordination - Teil 11: Begriffe, Grundsätze und Anforderungen für HVDC Systeme
Coordination de l'isolement - Partie 11: Définitions, principes et règles relatifs au réseau CCHT
L'IEC 60071-11:2022 s'applique aux réseaux à courant continu à haute tension (CCHT). Elle spécifie les principes relatifs aux procédures de détermination des tensions de tenue spécifiées, de la ligne de fuite et des distances d'isolement dans l'air pour l'équipement et l'installation de ces réseaux.
Le présent document donne les principes de coordination de l'isolement relatifs aux réseaux CCHT qui comportent des convertisseurs commutés par le réseau (LCC) et des convertisseurs à source de tension (VSC). Les principes fondamentaux du présent document s'appliquent également à d'autres configurations spécifiques de LCC, comme le convertisseur à condensateur commuté (CCC), le convertisseur à condensateurs en série contrôlés (CCSC), etc.
Le présent document s'applique à la coordination de l'isolement du matériel raccordé entre la barre à courant alternatif du convertisseur (y compris les filtres d'harmoniques côté courant alternatif, le transformateur convertisseur, les disjoncteurs) et le côté courant continu. Il traite également des terminaisons de lignes et de câbles, en raison de leur incidence sur la coordination de l'isolement du matériel des postes de conversion.
Le présent document ne s'applique qu'aux applications CCHT dans les réseaux d'alimentation, et non au matériel de conversion à usage industriel. Les principes et les recommandations ne sont fournis que dans le cadre de la coordination de l'isolement. Les exigences relatives à la sécurité des personnes ne sont pas traitées dans le présent document.
Cette Norme internationale remplace, conjointement avec l'IEC 60071-12, l'IEC 60071-5 parue en 2014.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'IEC 60071‑5:2014:
- la présente norme s'applique aux réseaux CCHT LCC et VSC, tandis que l'IEC 60071-5 concernait uniquement le réseau CCHT LCC;
- l'Annexe C (normative) fournit la tension de tenue spécifiée recommandée (LI et SI);
- l'Annexe C (normative) fournit les distances minimales d'isolement dans l'air;
- l'Annexe E indique la correspondance entre les articles/paragraphes de la présente norme et ceux de l'IEC 60071-5:2014.
Koordinacija izolacije - 11. del: Definicije, načela in pravila za visokonapetostni enosmerni (HVDC) sistem
Standard IEC 60071-11:2022 se uporablja za visokonapetostne enosmerne (HVDC) sisteme. Določa načela o postopkih za zagotavljanje navedenih vzdržnih napetosti, plazilnih razdalj in zračnih razdalj za opremo in inštalacije teh sistemov.
Ta dokument podaja načela za koordinacijo izolacije v zvezi z vodovno komutiranimi pretvorniki (LCC) in napetostnimi pretvorniki (VSC) visokonapetostnih enosmernih sistemov. Glavna načela tega dokumenta veljajo tudi za druge posebne konfiguracije vodovno komutiranih pretvornikov, kot sta kondezatorsko komutiran pretvornik (CCC) in krmiljen serijsko kompenziran pretvornik (CSCC) itd.
Ta dokument se uporablja za koordinacijo izolacije opreme, ki je povezana med vozlišče izmeničnega toka pretvornika (vključno s harmoničnimi filtri izmeničnega toka, pretvornikom-transformatorjem, odklopnikom) in stranjo voda z enosmernim tokom. Zajeti so tudi zaključki vodov in kablov, če vplivajo na koordinacijo izolacije opreme pretvorniške postaje.
Ta dokument se uporablja samo za uporabe visokonapetostnih enosmernih sistemov v napajalnih sistemih in ne za industrijsko pretvorno opremo. Podana načela in smernice so namenjeni samo koordinaciji izolacije. Zahteve za varnost ljudi niso obravnavane v tem dokumentu.
Ta mednarodni standard skupaj s standardom IEC 60071-12 nadomešča standard IEC 60071-5, objavljen leta 2014.
Ta izdaja vključuje naslednje pomembne tehnične spremembe glede na standard IEC 60071-5:2014:
Ta standard se uporablja za visokonapetostne enosmerne sisteme z vodovno komutiranimi pretvorniki in napetostnimi pretvorniki, medtem ko je standard IEC 60071-5 obravnaval samo visokonapetostne enosmerne sisteme z vodovno komutiranimi pretvorniki;
– Dodatek C (normativni) podaja priporočene specifične zdržne napetosti;
– Dodatek C (normativni) podaja minimalne zračne razdalje;
– Dodatek E prikazuje korelacijo med tem standardom in standardom IEC 60071-5:2014.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN IEC 60071-11:2023
01-maj-2023
Nadomešča:
SIST EN 60071-5:2015
Koordinacija izolacije - 11. del: Definicije, načela in pravila za visokonapetostni
enosmerni (HVDC) sistem
Insulation co-ordination - Part 11：Definitions, principles and rules for HVDC system
Isolationskoordination - Teil 11: Begriffe, Grundsätze und Anforderungen für HVDC
Systeme
Coordination de l'isolement - Partie 11: Définitions, principes et règles relatifs au réseau
CCHT
Ta slovenski standard je istoveten z: EN IEC 60071-11:2022
ICS:
29.080.01 Električna izolacija na Electrical insulation in
splošno general
SIST EN IEC 60071-11:2023 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN IEC 60071-11:2023
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SIST EN IEC 60071-11:2023
EUROPEAN STANDARD EN IEC 60071-11
NORME EUROPÉENNE
EUROPÄISCHE NORM December 2022
ICS 29.080.30 Supersedes EN 60071-5:2015 (partially)
English Version
Insulation co-ordination - Part 11:Definitions, principles and rules
for HVDC system
(IEC 60071-11:2022)
Coordination de l'isolement - Partie 11: Définitions, Isolationskoordination - Teil 11: Begriffe, Grundsätze und
principes et règles relatifs au réseau CCHT Anforderungen für HVDC Systeme
(IEC 60071-11:2022) (IEC 60071-11:2022)
This European Standard was approved by CENELEC on 2022-12-13. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60071-11:2022 E
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SIST EN IEC 60071-11:2023
EN IEC 60071-11:2022 (E)
European foreword
The text of document 99/374/FDIS, future edition 1 of IEC 60071-11, prepared by IEC/TC 99
"Insulation co-ordination and system engineering of high voltage electrical power installations above
1,0 kV AC and 1,5 kV DC" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN IEC 60071-11:2022.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2023-09-13
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2025-12-13
document have to be withdrawn
This document, in conjunction with EN IEC 60071-12:2022, supersedes (partially) EN 60071-5:2015
and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 60071-11:2022 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 standard indicated:
IEC 60071-5:2014 NOTE Harmonized as EN 60071-5:2015 (not modified)
IEC 60700-1:2015 NOTE Harmonized as EN 60700-1:2015 (not modified)
IEC 60633 NOTE Harmonized as EN IEC 60633
IEC 60099-5:2018 NOTE Harmonized as EN IEC 60099-5:2018 (not modified)
IEC 60505:2011 NOTE Harmonized as EN 60505:2011 (not modified)
IEC 60721-3-0:2020 NOTE Harmonized as EN IEC 60721-3-0:2020 (not modified)
IEC/TR 60919-2:2008 NOTE Harmonized as CLC/TR 60919-2:2010 (not modified)
2
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SIST EN IEC 60071-11:2023
EN IEC 60071-11:2022 (E)
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 60060-1 - High-voltage test techniques - Part 1: EN 60060-1 -
General definitions and test
requirements
IEC 60071-1 2019 Insulation co-ordination - Part 1: EN IEC 60071-1 2019
Definitions, principles and rules
IEC 60071-2 2018 Insulation co-ordination - Part 2: EN IEC 60071-2 2018
Application guidelines
IEC 60099-4 2014 Surge arresters - Part 4: Metal-oxide EN 60099-4 2014
surge arresters without gaps for a.c.
systems
IEC/TS 60815-1 2008 Selection and dimensioning of high- - -
voltage insulators intended for use in
polluted conditions - Part 1: Definitions,
information and general principles
IEC/TS 60815-2 2008 Selection and dimensioning of high- - -
voltage insulators intended for use in
polluted conditions - Part 2: Ceramic and
glass insulators for a.c. systems
IEC/TS 60815-3 2008 Selection and dimensioning of high- - -
voltage insulators intended for use in
polluted conditions - Part 3: Polymer
insulators for a.c. systems
3
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SIST EN IEC 60071-11:2023
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SIST EN IEC 60071-11:2023
IEC 60071-11
®
Edition 1.0 2022-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Insulation co-ordination –
Part 11: Definitions, principles and rules for HVDC system
Coordination de l'isolement –
Partie 11: Définitions, principes et règles relatifs au réseau CCHT
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.080.30 ISBN 978-2-8322-6026-5
Warning! Make sure that you obtained this publication from an authorized distributor.
Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
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SIST EN IEC 60071-11:2023
– 2 – IEC 60071-11:2022 © IEC 2022
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Symbols and abbreviations . 13
4.1 General . 13
4.2 Subscripts . 14
4.3 Letter symbols . 14
4.4 Abbreviations . 15
5 Principles of insulation co-ordination . 15
5.1 General . 15
5.2 Essential differences between AC and DC systems . 15
5.3 Insulation co-ordination procedure . 16
5.4 Differences of withstand voltage selection in AC and DC systems . 16
6 Design procedure of insulation co-ordination . 18
6.1 General . 18
6.2 Arrester characteristics . 18
6.3 Insulation characteristics . 18
6.4 Determination of the representative overvoltages (U ) . 18
rp
6.5 Determination of the co-ordination withstand voltages (U ) . 19
cw
6.6 Determination of the required withstand voltages (U ) . 19
rw
6.7 Determination of the specified withstand voltage (U ) . 21
w
7 Requirements for withstand voltage tests. 21
8 Creepage distances . 21
8.1 General . 21
8.2 Base voltage for creepage distance . 22
8.3 Creepage distance for outdoor insulation under DC voltage . 22
8.4 Creepage distance for indoor insulation under DC or mixed voltage . 22
8.5 Creepage distance of AC insulators . 22
9 Clearances in air . 23
Annex A (informative) Typical HVDC converter station schemes . 24
Annex B (informative) Example of air clearances calculation . 28
B.1 Introductory remarks . 28
B.2 Calculated minimum air clearance for switching impulse stress . 28
B.2.1 General . 28
B.2.2 Example calculation . 29
B.3 Calculated minimum air clearance for lightning impulse stress . 29
B.3.1 General . 29
B.3.2 Example calculation . 30
Annex C (normative) Example of typical DC voltages with possible insulation levels
and corresponding air clearances . 31
C.1 Introductory remarks . 31
C.2 List of typical DC voltagesand possible insulation levels . 31
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IEC 60071-11:2022 © IEC 2022 – 3 –
C.3 Example of presumed switching impulse insulation levels and minimum air
clearances . 31
C.4 Example of presumed lightning impulse insulation levels and minimum air
clearances . 33
C.5 Possible/Presumed specified DC withstand voltages . 33
C.5.1 General . 33
C.5.2 Specified DC withstand voltages . 34
C.5.3 List of specified power frequency withstand voltages . 34
Annex D (informative) Typical arrester characteristics . 35
Annex E (informative) The Correlation of clauses between IEC 60071-11 and
IEC 60071-5:2014 . 36
Bibliography . 37
Figure 1 – Comparison of the selection between withstand voltages for AC equipment
and for HVDC converter station equipment . 17
Figure A.1 – Possible arrester locations in one pole of bipole LCC converter station
with 12-pulse converters in series . 25
Figure A.2 – Possible arrester locations in one pole of bipolar of VSC converter
stations . 26
Figure A.3 – Possible arrester locations in symmetrical monopole VSC converter
stations . 26
Figure D.1 – Typical arrester V-I characteristics . 35
Table 1 – Classes and shapes of overvoltages, standard voltage shapes and standard
withstand voltage tests . 9
Table 2 – Comparison of the insulation co-ordination procedure of AC and DC systems . 16
Table 3 – Indicative values of ratios of required impulse withstand voltage to impulse
protective level . 20
Table A.1 – Symbol description . 27
Table C.1 – Typical DC voltages and switching/lightning impulse withstand voltage . 32
Table C.2 – Correlation between presumed rated switching impulse withstand voltages
and minimum phase-to-earth air clearances . 33
Table C.3 – Correlation between presumed rated lightning impulse withstand voltages
and minimum phase-to-earth air clearances . 34
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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INSULATION CO-ORDINATION –
Part 11: Definitions, principles and rules for HVDC system
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 60071-11 has been prepared by IEC technical committee 99: Insulation co-ordination and
system engineering of high voltage electrical power installations above 1,0 kV AC and
1,5 kV DC. It is an International Standard.
This international standard replaces, in conjunction with IEC 60071-12, IEC 60071-5 published
in 2014.
This edition includes the following significant technical changes with respect to
IEC 60071-5:2014:
a) This standard applies to both LCC and VSC HVDC systems whereas IEC 60071-5 only dealt
with LCC HVDC system;
b) Annex C (normative) gives the recommended specified withstand voltage (LI and SI);
c) Annex C (normative) gives the minimum air clearances;
d) Annex E shows the correlation of clauses between this standard and IEC 60071-5:2014.
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SIST EN IEC 60071-11:2023
IEC 60071-11:2022 © IEC 2022 – 5 –
The text of this International Standard is based on the following documents:
Draft Report on voting
99/374/FDIS 99/394/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.
A list of all parts in the IEC 60071 series, published under the general title Insulation
co-ordination, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
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INTRODUCTION
As the demand for electrical energy is growing, more and more HVDC projects have appeared,
and the voltage up to ±1 100 kV so far. However, the nominal voltage, nominal current and
insulation levels for HVDC system are not yet as standardized as the AC system.
In October 2016, IEC Technical Committee 28 (Insulation co-ordination) established AHG 8
(Ad hoc group 8) to make the roadmap for HVDC system insulation co-ordination standards.
After IEC TC 28 was merged into IEC TC 99 in 2017, JWG 13 (Joint working group 13) was
built by IEC TC 99 and TC 115 and was responsible for making the series standards for HVDC
system according to the approved roadmap, as follows:
a) Part 11: Definitions, principles and rules for HVDC system;
b) Part 12: Application guidelines for LCC HVDC converter stations;
c) Part 13: Application guidelines for VSC HVDC converter stations;
d) Part 14: Insulation co-ordination for AC/DC filters;
e) Part 15: Insulation co-ordination for DC transmission lines.
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IEC 60071-11:2022 © IEC 2022 – 7 –
INSULATION CO-ORDINATION –
Part 11: Definitions, principles and rules for HVDC system
1 Scope
This part of IEC 60071 applies to high-voltage direct current (HVDC) systems. It specifies the
principles on the procedures for the determination of the specified withstand voltages, creepage
distance and air clearances for the equipment and the installations of these systems.
This document gives the insulation co-ordination principles related to line commutated
converter (LCC) and voltage sourced converters (VSC) HVDC systems. The main principles of
this document also apply to other special converter configurations of LCC, such as the capacitor
commutated converter (CCC) as well as the controlled series compensated converter (CSCC),
etc.
This document applies to insulation co-ordination of equipment connected between the
converter AC bus (including the AC harmonic filters, the converter transformer, the circuit
breakers) and the DC line side. The line and cable terminations in so far as they influence the
insulation co-ordination of converter station equipment are also covered.
This document applies only for HVDC applications in power systems and not for industrial
conversion equipment. Principles and guidance given are for insulation co-ordination purposes
only. The requirements for human safety are not covered by 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 60060-1, High-voltage test techniques – Part 1: General definitions and test requirements
IEC 60071-1:2019, Insulation co-ordination – Part 1: Definitions, principles and rules
IEC 60071-2:2018, Insulation co-ordination – Part 2: Application guidelines
IEC 60099-4:2014, Surge arresters – Part 4: Metal-oxide surge arresters without gaps for a.c.
systems
IEC TS 60815-1:2008, Selection and dimensioning of high-voltage insulators intended for use
in polluted conditions – Part 1: Definitions, information and general principles
IEC TS 60815-2:2008, Selection and dimensioning of high-voltage insulators intended for use
in polluted conditions – Part 2: Ceramic and glass insulators for a.c. systems
IEC TS 60815-3:2008, Selection and dimensioning of high-voltage insulators intended for use
in polluted conditions – Part 3: Polymer insulators for a.c. systems
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3 Terms and definitions
For the purposes of this document, the following terms and definitions 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 Many of the following definitions refer to insulation co-ordination concepts (IEC 60071-1), or to arrester
parameters (IEC 60099-4).
3.1
insulation co-ordination
selection of the dielectric strength of equipment in relation to the operating voltages and
overvoltages which can appear on the system for which the equipment is intended and taking
into account the service environment and the characteristics of the available preventing and
protective devices
[SOURCE: IEC 60071-1:2019, 3.1, modified – The note to entry has been removed.]
3.2
nominal DC voltage
mean value of the DC voltage required to transmit nominal power at nominal current
3.3
highest DC voltage
highest value of DC voltage for which the equipment and system is designed to operate
continuously, in respect of its insulation as well as other characteristics
3.4
symmetrical monopole
HVDC converter with symmetrical DC voltage outputs on the two pole terminals
Note 1 to entry: A symmetrical monopole is generally applicable only to the VSC HVDC systems.
Note 2 to entry: “Symmetrical monopole” is used even though there are two polarities with DC voltages, because
only one converter is unable to provide the redundancy which is generally provided by “bipole”.
Note 3 to entry: In the symmetrical monopole operation, persistent overvoltage appears at the sound (healthy) pole
when a fault occurs at the opposite pole.
3.5
asymmetrical monopole
for the HVDC converter with asymmetrical DC voltage outputs on the two terminals, one terminal
is generally earthed
3.6
bipole
in general, two asymmetrical monopoles form a bipolar DC circuit
3.7
overvoltage
voltage having a value exceeding the corresponding highest steady state voltage of the system
Note 1 to entry: Table 1 presents (as per IEC 60071-1) the classification of these voltages which are defined in
3.7.1 to 3.7.2.3.
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SIST EN IEC 60071-11:2023
IEC 60071-11:2022 © IEC 2022 – 9 –
Table 1 – Classes and shapes of overvoltages, standard voltage shapes
and standard withstand voltage tests
Low frequency Transient
Class
Continuous Temporary Slow-front Fast-front Very-fast-front
1/f
Tf
1/f
1/f
Voltage or 2
over-
T
p
voltage
T
1
shapes Tt Tt 1/f
2
1/f1
T2
Tt T
2
T ≤ 100 ns
f
T ≥ 3 600s
t
10 Hz < f <
Range of
20 μs < T ≤ 0,1 μs < T ≤
f = 50 Hz or
p 1
500 Hz 0,3 MHz < f <
voltage or
1
1/T = f =
60 Hz
t 1 5 000 μs 20 μs
over-
100 MHz
0 Hz
0,02 s ≤ T ≤
voltage
T ≥ 3 600s t
T ≤ 20 ms T ≤ 300 μs
t
2 2
30 kHz < f <
shapes
2
3 600 s
f < 2 500 Hz
2
300 kHz
1/f
1/f
Standard
u +Δu
n
un
u -Δu a
voltage n
shapes
sec)
T Tt T
t T 1
p
Tt
T
2
T
2
∆U
f = 50 Hz 48 Hz ≤ f ≤
≤3% T = 250 μs T = 1,2 μs
b
p 1
U or 60 Hz 62 Hz
n
T = 2 500 μs T = 50 μs
a
2 2
a T T = 60 s
T t t
t
Short-
Standard
duration
withstand DC voltage Switching Lightning impulse
a a
power
a
voltage impulse test test
test
frequency
test
test
a
To be specified by the relevant apparatus committees.
b
Unless otherwise specified by the relevant Technical Committees, standard voltage shapes should be in
accordance with IEC 60060-1.
3.7.1
temporary overvoltage
overvoltages of relatively long duration (ranging from 0,02 to 3 600 s as per IEC 60071-1)
Note 1 to entry:
...
SLOVENSKI STANDARD
oSIST prEN IEC 60071-11:2022
01-marec-2022
Koordinacija izolacije - 11. del: Definicije, načela in pravila za visokonapetostni
enosmerni (HVDC) sistem
Insulation co-ordination - Part 11：Definitions, principles and rules for HVDC system
Ta slovenski standard je istoveten z: prEN IEC 60071-11:2022
ICS:
29.080.30 Izolacijski sistemi Insulation systems
oSIST prEN IEC 60071-11:2022 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN IEC 60071-11:2022
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oSIST prEN IEC 60071-11:2022
99/353/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 60071-11 ED1
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2022-01-07 2022-04-01
SUPERSEDES DOCUMENTS:
99/322/CD, 99/350/CC
IEC TC 99 : INSULATION CO-ORDINATION AND SYSTEM ENGINEERING OF HIGH VOLTAGE ELECTRICAL POWER INSTALLATIONS ABOVE 1,0
KV AC AND 1,5 KV DC
SECRETARIAT: SECRETARY:
Australia Ms Erandi Chandrasekare
OF INTEREST TO THE FOLLOWING COMMITTEES: PROPOSED HORIZONTAL STANDARD:
TC 8,SC 22F,TC 115
Other TC/SCs are requested to indicate their interest, if any,
in this CDV to the secretary.
FUNCTIONS CONCERNED:
EMC ENVIRONMENT QUALITY ASSURANCE SAFETY
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft for
Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of which they
are aware and to provide supporting documentation.
TITLE:
Insulation co-ordination - Part 11：Definitions, principles and rules for HVDC system
PROPOSED STABILITY DATE: 2026
NOTE FROM TC/SC OFFICERS:
Copyright © 2021 International Electrotechnical Commission, IEC. All rights reserved. It is permitted to download this
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.
You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without
permission in writing from IEC.
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1
2 CONTENTS
3
4 FOREWORD . 4
5 1 Scope . 7
6 1.1 General . 7
7 1.2 Additional background . 7
8 2 Normative references . 7
9 3 Terms and definitions . 8
10 4 Symbols and abbreviations . 14
11 4.1 General . 14
12 4.2 Subscripts . 14
13 4.3 Letter symbols . 14
14 4.4 Abbreviations . 14
15 5 Principles of insulation co-ordination . 15
16 5.1 General . 15
17 5.2 Essential differences between AC and DC systems. 15
18 5.3 Insulation co-ordination procedure . 16
19 5.4 Differences of withstand voltage selection in AC and DC systems . 16
20 6 Design procedure of insulation co-ordination . 18
21 6.1 General . 18
22 6.2 Arrester characteristics . 18
23 6.3 Insulation characteristics . 18
24 6.4 Determination of the representative overvoltages (U ) . 19
rp
25 6.5 Determination of the co-ordination withstand voltages (Ucw) . 19
26 6.6 Determination of the required withstand voltages (U ) . 19
rw
27 6.7 Determination of the specified withstand voltage (Uw) . 21
28 7 Requirements for withstand voltage tests . 21
29 8 Creepage distances . 21
30 8.1 General . 21
31 8.2 Base voltage for creepage distance . 21
32 8.3 Creepage distance for outdoor insulation under DC voltage . 22
33 8.4 Creepage distance for indoor insulation under DC or mixed voltage . 22
34 8.5 Creepage distance of AC insulators . 22
35 9 Clearances in air . 23
36 Annex A (informative) Typical HVDC converter station schemes . 24
37 Annex B (informative) Example of air clearances calculation . 27
38 Annex C (normative) Example of typical DC voltages with possible insulation levels
39 and corresponding air clearances . 30
40 Annex D (informative) Typical arrester characteristics. 34
41 Bibliography . 35
42
43 Figure 1 –Comparison of the selection between withstand voltages for AC equipment
44 and HVDCconverter station equipment . 17
45 Figure A.1 – Possible arrester locations in a pole with two 12-pulse converters in
46 series of LCC converter station . 25
47 Figure A.2–Possible arrester locations in one pole of bipolar of VSC converter stations . 25
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48 Figure A.3 –Possible arrester locations in symmetrical monopole VSC converter
49 stations . 26
50
51 Table 1 – Classes and shapes of overvoltages, Standard voltage shapes and Standard
52 withstand voltage tests . 9
53 Table 2 – Comparison the insulation coordination procedure of AC and DC systems . 16
54 Table 3 – Indicative values of ratios of required impulse withstand voltage to impulse
55 protective level . 20
56 Table A.1– Symbol description . 26
57 Table C.1– Typical DC voltages and switching/lightning impulse withstand voltage . 31
58 Table C.2– Correlation between presumed rated switching impulse withstand voltages
59 and minimum phase-to-earth air clearances . 32
60 Table C.3– Correlation between presumed rated lightning impulse withstand voltages
61 and minimum phase-to-earth air clearances . 33
62
63
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64 INTERNATIONAL ELECTROTECHNICAL COMMISSION
65 ____________
66
67 INSULATION CO-ORDINATION –
68
69 Part 11: Definitions, principles and rules for HVDC system
70
71
72
73 FOREWORD
74 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
75 all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
76 international co-operation on all questions concerning standardization in the electrical and electronic fields. To
77 this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
78 Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
79 Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
80 in the subject dealt with may participate in this preparatory work. International, governmental and non-
81 governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
82 with the International Organization for Standardization (ISO) in accordance with conditions determined by
83 agreement between the two organizations.
84 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
85 consensus of opinion on the relevant subjects since each technical committee has representation from all
86 interested IEC National Committees.
87 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
88 Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
89 Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
90 misinterpretation by any end user.
91 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
92 transparently to the maximum extent possible in their national and regional publications. Any divergence
93 between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
94 the latter.
95 5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
96 assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
97 services carried out by independent certification bodies.
98 6) All users should ensure that they have the latest edition of this publication.
99 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
100 members of its technical committees and IEC National Committees for any personal injury, property damage or
101 other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
102 expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
103 Publications.
104 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
105 indispensable for the correct application of this publication.
106 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
107 patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
108 IEC 60071-11 has been prepared by IEC technical committee 99: Insulation co-ordination and
109 system engineering of high voltage electrical power installations above 1,0 kV AC and 1,5 kV
110 DC. It is an International Standard.
111 This International Standard and IEC 60071-12 'Application guidelines for LCC HVDC converter
112 stations' jointly replace IEC 60071-5 published in 2014.
113 The sections arrangement of this standard and corresponding sections of IEC 60071-5:2014 are as
114 follows:
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IEC 60071-11 IEC 60071-5:2014
1 Scope 1
1.1 General 1.1
1.2 Additional background 1.2
2 Normative references 2
3 Terms and definitions 3
4 Symbols and abbreviations 4
4.1 General 4.1
4.2 Subscripts 4.2
4.3 Letter symbols 4.3
4.4 Abbreviations 4.4
5 Principles of insulation co-ordination 6
5.1 General 6.1
5.2 Essential differences between AC and DC systems 6.2
5.3 Insulation co-ordination procedure 6.3
5.4 Differences of withstand voltage selection in AC and DC 6.4
systems
6 Design procedure of insulation co-ordination 9
6.1 General 9.1
6.2 Arrester characteristics 8.1
6.3 Insulation characteristics 9.3
6.4 Determination of the representativeovervoltages (U ) 9.4
rp
6.5 Determination of the co-ordination withstand voltages (U ) 9.5
cw
6.6 Determination of the required withstand voltages (U ) 9.6
rw
6.7 Determination of the specified withstand voltage (U ) 9.7
w
7 Requirements for withstand voltage tests -
8 Creepage distances 11
8.1 General 11.1
8.2 Base voltage for creepage distance 11.2
8.3 Creepage distance for outdoor insulation under DC voltage 11.3
8.4 Creepage distance for indoor insulation under DC or mixed 11.4
voltage
8.5 Creepage distance of AC insulators 11.5
9 Clearances in air 12
Annex A (informative)
Typical HVDC converter station arrester protection schemes
Annex B (informative)
Example of air clearances calculation
Annex C (normative)
Example of typical DC voltages with possible insulation levels
and corresponding air clearances
Annex D (informative)
Annex D
Typical arrester characteristics
115
116 The text of this International Standard is based on the following documents:
Draft Report on voting
XX/XX/FDIS XX/XX/RVD
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117
118 Full information on the voting for its approval can be found in the report on voting indicated in
119 the above table.
120 The language used for the development of this International Standard is English.
121 This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
122 accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,
123 available at www.iec.ch/members_experts/refdocs. The main document types developed by
124 IEC are described in greater detail at http://www.iec.ch/standardsdev/publications.
125 The committee has decided that the contents of this document will remain unchanged until the
126 stability date indicated on the IEC website under webstore.iec.ch in the data related to the
127 specific document. At this date, the document will be
128 • reconfirmed,
129 • withdrawn,
130 • replaced by a revised edition, or
131 • amended.
132
133
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134 INSULATION CO-ORDINATION–
135
136 Part 11: Definitions, principles and rules for HVDC system
137
138
139
140 1 Scope
141 1.1 General
142 This standard applies to High-voltage direct current (HVDC) systems. It specifies the
143 principles on the procedures for the determination of the specified withstand voltages,
144 creepage distance and air clearances for the equipment and the installations of these systems.
145 This standard gives the insulation co-ordination principles related to line commutated
146 converter (LCC) and voltage sourced converters (VSC) HVDC systems. The main principles of
147 this standard also apply to other special converter configurations of LCC, such as the
148 capacitor commutated converter (CCC) as well as the controlled series compensated
149 converter (CSCC) etc.
150 This standard applies to insulation co-ordination of equipment connected between the
151 converter AC bus (including the AC harmonic filters, the converter transformer, the circuit
152 breakers) and the DC line side. The line and cable terminations in so far as they influence the
153 insulation co-ordination of converter station equipment are also covered.
154 This standard applies only for HVDC applications in power systems and not for industrial
155 conversion equipment. Principles and guidance given are for insulation co-ordination
156 purposes only. The requirements for human safety are not covered by this standard.
157 This horizontal standard is primarily intended for use by technical committees in the
158 preparation of standards in accordance with the principles laid down in IEC Guide 108.
159 One of the responsibilities of a technical committee is, wherever applicable, to make use of
160 horizontal standards in the preparation of its publications. The contents of this horizontal
161 standard will not apply unless specifically referred to or included in the relevant publications.
162 1.2 Additional background
163 The use of power semi-conductor device in a series and/or parallel arrangement, along with
164 the unique control and protection strategies employed in the conversion process, has
165 ramifications requiring particular consideration of overvoltage protection of equipment in
166 converter stations compared with substations in AC systems.
167 The basic principles and design objectives of insulation co-ordination of converter stations, in
168 so far as they differ from normal AC system practice, are described.
169 NOTE In IEC 60071-12, Application guidelines, all rules for insulation co-ordination given in this standard are
170 justified in detail, in particular the association of the specified withstand voltages with the rated voltage for
171 equipment, and arrester configuration.
172 2 Normative references
173 The following documents are referred to in the text in such a way that some or all of their
174 content constitutes requirements of this document. For dated references, only the edition
175 cited applies. For undated references, the latest edition of the referenced document (including
176 any amendments) applies.
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177 IEC 60060-1, High-voltage test techniques – Part 1: General definitions and test requirements
178 IEC 60071-1:2019, Insulation co-ordination – Part 1: Definitions, principles and rules
179 IEC 60071-2:2018, Insulation co-ordination – Part 2: Application guidelines
180 IEC 60099-4:2014, Surge arresters – Part 4: Metal-oxide surge arresters without gaps for a.c.
181 systems
182 IEC 60633, Terminology for high-voltage direct current (HVDC) transmission
183 IEC 60700-1:2015, Thyristor valves for high voltage direct current (HVDC) power transmission
184 – Part 1 Electrical testing
185 IEC TS 60815-1:2008, Selection and dimensioning of high-voltage insulators intended for use
186 in polluted conditions – Part 1: Definitions, information and general principles
187 IEC TS 60815-2:2008, Selection and dimensioning of high-voltage insulators intended for use
188 in polluted conditions – Part 2: Ceramic and glass insulators for a.c. systems
189 IEC TS 60815-3:2008, Selection and dimensioning of high-voltage insulators intended for use
190 in polluted conditions – Part 3: Polymer insulators for a.c. systems
191 IEC TS 60815-4:2016, Selection and dimensioning of high-voltage insulators intended for use
192 in polluted conditions – Part 4: Insulators for d.c. systems.
193 3 Terms and definitions
194 For the purposes of this document, the following terms and definitions apply.
195 ISO and IEC maintain terminological databases for use in standardization at the following
196 addresses:
197 • IEC Electropedia: available at http://www.electropedia.org/
198 • ISO Online browsing platform: available at http://www.iso.org/obp
199 NOTE Many of the following definitions refer to insulation co-ordination concepts (IEC 60071-1), or to arrester
200 parameters (IEC 60099-4).
201 3.1
202 insulation co-ordination
203 selection of the dielectric strength of equipment in relation to the operating voltages and
204 overvoltages which can appear on the system for which the equipment is intended and taking
205 into account the service environment and the characteristics of the available preventing and
206 protective devices
207 [SOURCE: IEC 60071-1: 2019, 3.1]
208 3.2
209 nominal DC voltage
210 mean value of the DC voltage required to transmit nominal power at nominal current
211 3.3
212 highest DC voltage
213 highest value of DC voltage for which the equipment is designed to operate continuously, in
214 respect of its insulation as well as other characteristics
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215 3.4
216 overvoltage
217 voltage having a value exceeding the corresponding highest steady state voltage of the
218 system
219 Note 1 to entry: Table 1 presents (as per IEC 60071-1) the classification of these voltages which are defined in
220 3.4.1 to 3.4.2.3.
221
222 Table 1 – Classes and shapes of overvoltages, Standard voltage shapes
223 and Standard withstand voltage tests
Low frequency Transient
Class
Continuous Temporary Slow-front Fast-front Very-fast-front
T
f
1/f
1/f
2
1/f
Voltage or
over-
Tp
voltage
T1
T
t
1/f
2
shapes T
t 1/f
1
T
Tt 2
T
2
T≤ 100 ns
f
10 Hz
Range of
0,3 MHz
T≥3 600s 1
t 20 µs
f = 50 Hz or
p 1
500 Hz
voltage or
100 MHz
60 Hz
5 000 µs 20 µs
over- 1/T = f = 0 Hz
t 1
voltage 0,02 s ≤T≤ 30 kHz
t 2
T≥3 600s
T ≤ 20 ms T ≤ 300 µs
t
2 2
f <2 500 Hz
2
shapes
3 600 s 300 kHz
1/f
1/f
un+Δu
u
n
un-Δu
Standard
se
a
voltage T Tp T
Tt t 1
Tt
shapes
T
2
T2
b
∆U
f = 50 Hz
48 Hz ≤f≤
≤ 3%
T = 250 µs T = 1,2 µs
p 1
or 60 Hz
U 62 Hz
n
T = 2 500 µs T = 50 µs
a
2 2
a
T T = 60 s
T t t
t
Standard Short-duration
DC voltage Switching impulse Lightning impulse
a
withstand power a
a
test test test
voltage test frequency test
a
To be specified by the relevant apparatus committees.
b
Unless otherwise specified by the relevant Technical Committees, standard voltage shapes should be in accordance with IEC
60060-1.
224
225 3.4.1
226 temporary overvoltage
227 overvoltages of relatively long duration (ranging from 0,02 to 3 600 s as per IEC 60071-1)
228 Note 1 to entry: The overvoltage may be undamped or weakly damped.
229 3.4.2
230 transient overvoltage
231 short-duration overvoltage of a few millisecond or less, oscillatory or non-oscillatory, usually
232 highly damped
233 [SOURCE: IEC 60071-1: 2019, 3.17.3]
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234 3.4.2.1
235 slow-front overvoltage
236 transient overvoltage, usually unidirectional, with time to peak 20 μs < T ≤ 5 000 μs, and
p
237 tail duration T ≤ 20 ms
2
238 Note 1 to entry: For the purpose of insulation co-ordination, slow-front overvoltages are classified according to
239 their shape, regardless of their origin. Although considerable deviations from the standard shapes occur on actual
240 systems, in this standard it is considered sufficient in most cases to describe such overvoltages by their
241 classification and peak value.
242 3.4.2.2
243 fast-front overvoltage
244 overvoltage at a given location on a system, due to a lightning discharge or other cause, the
245 shape of which can be regarded, for insulation co-ordination purposes, as similar to that of
246 the standard impulse (IEC 60060-1) used for lightning impulse tests
247 Note 1 to entry: Fast-front overvoltage is defined as transient overvoltage, usually unidirectional, with time to peak
248 0,1 μs < T ≤ 20 μs, and tail duration T ≤ 300 μs in IEC 60071-1:2019, 3.17.3.2.
1 2
249 Note 2 to entry: For the purpose of insulation co-ordination, fast-front overvoltages are classified according to their
250 shape, regardless of their origin. Although considerable deviations from the standard shapes occur on actual
251 systems, in this standard it is considered sufficient in most cases to describe such overvoltages by their
252 classification and peak value.
253 3.4.2.3
254 very-fast-front overvoltage
255 transient overvoltage, usually unidirectional, with time to peak T < 0,1 μs, and with or without
f
256 superimposed oscillations at frequency 30 kHz < f < 100 MHz
257 [SOURCE: IEC 60071-1:2019, 3.17.3.3]
258 3.4.2.4
259 steep-front overvoltage
260 transient overvoltage classified as a kind of fast-front overvoltage with time to peak3 ns < T <
1
261 1,2 μs
262 Note 1 to entry: A steep-front impulse voltage for test purposes is defined in IEC 60700-1.
263 Note 2 to entry: The front time is decided by means of system studies.
264 3.4.2.5
265 combined overvoltage
266 overvoltage consisting of two voltage components simultaneously applied between each of
267 the two-phase terminals of a phase-to-phase (or longitudinal) insulation and earth
268 Note 1 to entry: Combined overvoltage can include temporary, slow-front, fast-front or very-fast front overvoltages.
269 Note 2 to entry: It is classified by the component of higher peak value.
270 3.5
271 representative overvoltages
272 U
rp
273 overvoltages assumed to produce the same dielectric effect on the insulation as overvoltages
274 of a given class occurring in service due to various origins
275 Note 1 to entry: In this standard it is generally assumed that the representative overvoltages are characterized by
276 their assumed or obtained maximum values.
277 [SOURCE: IEC 60071-1:2019, 3.19]
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278 3.5.1
279 representative slow-front overvoltage
280 RSFO
281 voltage value between terminals of an equipment having the shape of a standard switching
282 impulse
283 3.5.2
284 representative fast-front overvoltage
285 RFFO
286 voltage value between terminals of an equipment having the shape of a standard lightning
287 impulse
288 3.5.3
289 representative steep-front overvoltage
290 RSTO
291 voltage value with a standard shape having a time to crest less than that of a standard
292 lightning impulse, but not less than that of a very-fast-front overvoltage as defined by IEC
293 60071-1
294 Note 1 to entry: A steep-front impulse voltage for test purposes is defined in Figure 1 of IEC 60700-1:2015. The
295 front time is decided by means of system studies.
296 3.6
297 co-ordination withstand voltage
298 U
cw
299 for each class of voltage, value of the withstand voltage of the insulation configuration, in
300 actual service conditions, that meets the performance criterion
301 [SOURCE: IEC 60071-1:2019, 3.24]
302 3.7
303 required withstand voltage
304 U
rw
305 test voltage that the insulation must withstand in a standard withstand voltage test to ensure
306 that the insulation will meet the performance criterion when subjected to a given class of
307 overvoltages in actual service conditions and for the whole service duration. The required
308 withstand voltage has the shape of the co-ordination withstand voltage, and is specified with
309 reference to all the conditions of the standard withstand voltage test selected to verify it
310 [SOURCE: IEC 60071-1:2019, 3.27]
311 3.8
312 specified withstand voltage
313 U
w
314 test voltage suitably selected equal to or above the required withstand voltage (U )
rw
315 Note 1 to entry: For AC equipment, values of withstand voltages U are standardized as per IEC 60071-1. For
w
316 HVDC equipment, the specified withstand voltages are rounded up to convenient practical values.
317 Note 2 to entry: The standard impulse shapes used for withstand tests on equipment as well as the test procedures
318 are defined in IEC 60060-1 and IEC 60071-1. For some DC equipment (e.g. the thyristor valves), the standard
319 impulse shapes may be modified in order to more rea
...
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