IEC 60071-2:2023

Insulation co-ordination - Part 2: Application guidelines

IEC 60071-2:2023 constitutes application guidelines and deals with the selection of insulation levels of equipment or installations for three-phase AC systems. Its aim is to give guidance for the determination of the rated withstand voltages for ranges I and II of IEC 60071‑1 and to justify the association of these rated values with the standardized highest voltages for equipment. This association is for insulation co-ordination purposes only. The requirements for human safety are not covered by this document. This document covers three-phase AC systems with nominal voltages above 1 kV, phase-to-earth, phase-to-phase and longitudinal insulation. It has the status of a horizontal standard in accordance with IEC Guide 108. This edition includes the following significant technical changes with respect to the previous edition:
a) Clause 4 Concepts governing the insulation co-ordination has been added.
b) Subclause 5.3 has been revised, and Subclause 5.4 Detailed simulation has been added because it is widely applied in the recent practices of insulation coordination.
c) Special considerations for cable line and GIL/GIB have been added in Clause 9.
d) Annex K (informative) Application of line shunt reactor to limitation of TOV and SFO in high voltage overhead transmission lines has been added.
e) Annex L (informative) Calculation of lightning stroke rate and lightning outage rate has been added.

Coordination de l'isolement - Partie 2: Lignes directrices en matière d'application

L'IEC 60071-2:2023 constitue des lignes directrices en matière d'application et concerne le choix des niveaux d'isolement des matériels ou des installations pour les réseaux triphasés en courant alternatif. Elle a pour objet de donner des recommandations pour la détermination des tensions de tenue assignées pour les plages I et II de l'IEC 60071-1 et de justifier l'association de ces valeurs assignées avec les valeurs normalisées des tensions les plus élevées pour le matériel. Cette association ne couvre que les besoins de la coordination de l'isolement. Les exigences relatives à la sécurité des personnes ne sont pas traitées dans le présent document. Le présent document traite des réseaux triphasés en courant alternatif de tension nominale supérieure à 1 kV. Le présent document traite de l'isolement phase-terre, entre phases et longitudinal. Le présent document a le statut d'une norme horizontale conformément au Guide 108 de l'IEC. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) l'Article 4, Concepts applicables à la coordination de l'isolement, a été ajouté;
lb) e 5.3 a été révisé et le 5.4, Simulation détaillée, a été ajouté, car la simulation est largement appliquée dans les récentes pratiques de coordination de l'isolement;
c) des points particuliers ont été ajoutés pour les câbles et pour les lignes de transport/barres blindées à isolation gazeuse à l'Article 9;
d) l'Annexe K (informative), Application d'une inductance shunt pour la limitation des TOV et des SFO dans les lignes de transport aériennes à haute tension, a été ajoutée;
e) l'Annexe L (informative), Calcul du taux de foudroiement et du taux de coupure due à la foudre, a été ajoutée.

General Information

• Status: Published
• Publication Date: 23-May-2023
• ICS: 29.080.30 - Insulation systems
• Technical Committee: TC 99 - Insulation co-ordination and system engineering of high voltage electrical power installations above 1,0 kV AC and 1,5 kV DC
• Drafting Committee: MT 9 - TC 99/MT 9
• Current Stage: PPUB - Publication issued
• Start Date: 14-Jun-2023
• Completion Date: 24-May-2023

Relations

• Revises: IEC 60071-2:2018 - Insulation co-ordination - Part 2: Application guidelines
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 60071-2 ®
Edition 5.0 2023-05
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
HORIZONTAL PUBLICATION
Insulation co-ordination –
Part 2: Application guidelines

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.

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About the IEC
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IEC 60071-2 ®
Edition 5.0 2023-05
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
HORIZONTAL PUBLICATION
Insulation co-ordination –
Part 2: Application guidelines
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.080.30 ISBN 978-2-8322-7074-5

– 2 – IEC 60071-2:2023 RLV © IEC 2023
CONTENTS
FOREWORD . 9
1 Scope . 11
2 Normative references . 11
3 Terms, definitions, abbreviated terms and symbols . 12
3.1 Terms and definitions . 12
3.2 Abbreviated terms . 12
3.3 Symbols . 12
4 Concepts governing the insulation co-ordination . 18
5 Representative voltage stresses in service . 19
5.1 Origin and classification of voltage stresses . 19
5.2 Characteristics of overvoltage protection devices . 20
5.2.1 General remarks . 20
5.2.2 Metal-oxide surge arresters without gaps (MOSA) . 20
5.2.3 Line surge arresters (LSA) for overhead transmission and distribution
lines . 22
5.3 General approach for the determination of representative voltages and
overvoltages . 23
5.3.1 Continuous (power-frequency) voltage . 23
5.3.2 Temporary overvoltages . 23
5.3.3 Slow-front overvoltages . 26
5.3.4 Fast-front overvoltages . 32
5.3.5 Very-fast-front overvoltages . 36
5.4 Determination of representative overvoltages by detailed simulations . 37
5.4.1 General overview . 37
5.4.2 Temporary overvoltages . 37
5.4.3 Slow-front overvoltages . 38
5.4.4 Fast-front overvoltages . 39
5.4.5 Very-fast-front overvoltages . 43
6 Co-ordination withstand voltage . 44
6.1 Insulation strength characteristics . 44
6.1.1 General . 44
6.1.2 Influence of polarity and overvoltage shapes . 46
6.1.3 Phase-to-phase and longitudinal insulation . 47
6.1.4 Influence of weather conditions on external insulation . 47
6.1.5 Probability of disruptive discharge of insulation . 47
6.2 Performance criterion . 49
6.3 Insulation co-ordination procedures . 49
6.3.1 General . 49
6.3.2 Insulation co-ordination procedures for continuous (power-frequency)
voltage and temporary overvoltage . 50
6.3.3 Insulation co-ordination procedures for slow-front overvoltages . 51
6.3.4 Insulation co-ordination procedures for fast-front overvoltages . 56
6.3.5 Insulation co-ordination procedures for very-fast-front overvoltages . 57
7 Required withstand voltage . 57
7.1 General remarks . 57
7.2 Atmospheric correction . 57
7.2.1 General remarks . 57

7.2.2 Altitude correction . 58
7.3 Safety factors. 59
7.3.1 General . 59
7.3.2 Ageing . 60
7.3.3 Production and assembly dispersion . 60
7.3.4 Inaccuracy of the withstand voltage . 60
7.3.5 Recommended safety factors (K ) . 60
s
8 Standard withstand voltage and testing procedures . 61
8.1 General remarks . 61
8.1.1 Overview . 61
8.1.2 Standard switching impulse withstand voltage . 61
8.1.3 Standard lightning impulse withstand voltage . 61
8.2 Test conversion factors . 62
8.2.1 Range I. 62
8.2.2 Range II . 62
8.3 Determination of insulation withstand by type tests . 63
8.3.1 Test procedure dependency upon insulation type . 63
8.3.2 Non-self-restoring insulation . 63
8.3.3 Self-restoring insulation . 63
8.3.4 Mixed insulation . 64
8.3.5 Limitations of the test procedures . 65
8.3.6 Selection of the type test procedures . 65
8.3.7 Selection of the type test voltages . 65
9 Special considerations for overhead lines apparatus and transmission line . 66
9.1 Overhead line . 66
9.1.1 General remarks . 66
9.1.2 Insulation co-ordination for operating voltages and temporary
overvoltages . 67
9.1.3 Insulation co-ordination for slow-front overvoltages . 67
9.1.4 Insulation co-ordination for lightning fast-front overvoltages . 68
9.2 Cable line . 69
9.2.1 General . 69
9.2.2 Insulation co-ordination for operating voltages and temporary
overvoltages . 69
9.2.3 Insulation co-ordination for slow-front overvoltages . 69
9.2.4 Insulation co-ordination for fast-front overvoltages . 70
9.2.5 Overvoltage protection of cable lines . 70
9.3 GIL (gas insulated transmission line) / GIB (Gas-insulated busduct) . 71
9.3.1 General . 71
9.3.2 Insulation co-ordination for operating voltages and temporary
overvoltages . 71
9.3.3 Insulation co-ordination for slow-front overvoltages . 71
9.3.4 Insulation co-ordination for fast-front overvoltages . 72
9.3.5 Overvoltage protection of GIL/GIB lines . 72
9.4 Special considerations for substations Substation . 68
9.4.1 General remarks . 72
9.4.2 Insulation co-ordination for overvoltages. 73
Annex A (informative) Determination of temporary overvoltages due to earth faults . 76
Annex B (informative) Weibull probability distributions . 80

– 4 – IEC 60071-2:2023 RLV © IEC 2023
B.1 General remarks . 80
B.2 Disruptive discharge probability of external insulation . 81
B.3 Cumulative frequency distribution of overvoltages . 84
Annex C (informative) Determination of the representative slow-front overvoltage due
to line energization and re-energization . 86
C.1 General remarks . 86
C.2 Probability distribution of the representative amplitude of the prospective
overvoltage phase-to-earth .
...

IEC 60071-2 ®
Edition 5.0 2023-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
HORIZONTAL PUBLICATION
PUBLICATION HORIZONTALE
Insulation co-ordination –
Part 2: Application guidelines

Coordination de l'isolement –
Partie 2: Lignes directrices en matière d'application

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
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International Standards for all electrical, electronic and related technologies.

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IEC 60071-2 ®
Edition 5.0 2023-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
HORIZONTAL PUBLICATION
PUBLICATION HORIZONTALE
Insulation co-ordination –
Part 2: Application guidelines

Coordination de l'isolement –
Partie 2: Lignes directrices en matière d'application

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.080.30 ISBN 978-2-8322-6988-6

– 2 – IEC 60071-2:2023 © IEC 2023
CONTENTS
FOREWORD . 9
1 Scope . 11
2 Normative references . 11
3 Terms, definitions, abbreviated terms and symbols . 12
3.1 Terms and definitions . 12
3.2 Abbreviated terms . 12
3.3 Symbols . 13
4 Concepts governing the insulation co-ordination . 18
5 Representative voltage stresses in service . 19
5.1 Origin and classification of voltage stresses . 19
5.2 Characteristics of overvoltage protection devices . 19
5.2.1 General remarks . 19
5.2.2 Metal-oxide surge arresters without gaps (MOSA) . 20
5.2.3 Line surge arresters (LSA) for overhead transmission and distribution
lines . 22
5.3 General approach for the determination of representative voltages and
overvoltages . 22
5.3.1 Continuous (power-frequency) voltage . 22
5.3.2 Temporary overvoltages . 22
5.3.3 Slow-front overvoltages . 26
5.3.4 Fast-front overvoltages . 32
5.3.5 Very-fast-front overvoltages . 36
5.4 Determination of representative overvoltages by detailed simulations . 37
5.4.1 General overview . 37
5.4.2 Temporary overvoltages . 37
5.4.3 Slow-front overvoltages . 38
5.4.4 Fast-front overvoltages . 39
5.4.5 Very-fast-front overvoltages . 43
6 Co-ordination withstand voltage . 44
6.1 Insulation strength characteristics . 44
6.1.1 General . 44
6.1.2 Influence of polarity and overvoltage shapes . 45
6.1.3 Phase-to-phase and longitudinal insulation . 46
6.1.4 Influence of weather conditions on external insulation . 47
6.1.5 Probability of disruptive discharge of insulation . 47
6.2 Performance criterion . 49
6.3 Insulation co-ordination procedures . 49
6.3.1 General . 49
6.3.2 Insulation co-ordination procedures for continuous (power-frequency)
voltage and temporary overvoltage . 50
6.3.3 Insulation co-ordination procedures for slow-front overvoltages . 51
6.3.4 Insulation co-ordination procedures for fast-front overvoltages . 55
6.3.5 Insulation co-ordination procedures for very-fast-front overvoltages . 56
7 Required withstand voltage . 56
7.1 General remarks . 56
7.2 Atmospheric correction . 56
7.2.1 General remarks . 56

7.2.2 Altitude correction . 57
7.3 Safety factors. 58
7.3.1 General . 58
7.3.2 Ageing . 59
7.3.3 Production and assembly dispersion . 59
7.3.4 Inaccuracy of the withstand voltage . 59
7.3.5 Recommended safety factors (K ) . 59
s
8 Standard withstand voltage and testing procedures . 60
8.1 General remarks . 60
8.1.1 Overview . 60
8.1.2 Standard switching impulse withstand voltage . 60
8.1.3 Standard lightning impulse withstand voltage . 60
8.2 Test conversion factors . 61
8.2.1 Range I. 61
8.2.2 Range II . 61
8.3 Determination of insulation withstand by type tests . 62
8.3.1 Test procedure dependency upon insulation type . 62
8.3.2 Non-self-restoring insulation . 62
8.3.3 Self-restoring insulation . 62
8.3.4 Mixed insulation . 63
8.3.5 Limitations of the test procedures . 64
8.3.6 Selection of the type test procedures . 64
8.3.7 Selection of the type test voltages . 64
9 Special considerations for apparatus and transmission line . 65
9.1 Overhead line . 65
9.1.1 General . 65
9.1.2 Insulation co-ordination for operating voltages and temporary
overvoltages . 66
9.1.3 Insulation co-ordination for slow-front overvoltages . 66
9.1.4 Insulation co-ordination for fast-front overvoltages . 67
9.2 Cable line .
...