IEC 60071-2:2018

Insulation co-ordination - Part 2: Application guidelines

IEC 60071-2:2018 is now available as IEC 60071-2:2018 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 60071-2:2018 constitutes application guidelines and deals with the selection of insulation levels of equipment or installations for three-phase electrical systems. It gives 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. It covers three-phase systems with nominal voltages above 1 kV. This edition includes the following significant technical changes with respect to the previous edition:
a) the annex on clearance in air to assure a specified impulse withstand voltage installation is deleted because the annex in IEC 60071-1 is overlapped;
b) 4.2 and 4.3 on surge arresters are updated;
c) 4.3.5 on very-fast-front overvoltages is revised. Annex J on insulation co-ordination for very-fast-front overvoltages in UHV substations is added;
d) Annex H on atmospheric correction – altitude correction is added.
e) Annex I on evaluation method of non-standard lightning overvoltage shape is added.
It has the status of a horizontal standard in accordance with IEC Guide 108.

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

IEC 60071-2:2018 est disponible sous forme de IEC 60071-2:2018 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.
L'IEC 60071-2:2018 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. 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. Il traite des réseaux triphasés de tension nominale supérieure à 1 kV. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) l'annexe relative à la distance d'isolement dans l'air pour installation garantissant une tension de tenue aux chocs spécifiée est supprimée car cette annexe est déjà présente dans l'IEC 60071-1;
b) 4.2et 4.3relatifs aux parafoudres ont été mis à jour;
c) 4.3.5relatif aux surtensions à front très rapide a été révisé. L'Annexe J relative à la coordination de l'isolement pour les surtensions à front très rapide dans les postes UHT a été ajoutée;
d) l'Annexe H relative à la correction atmosphérique – correction de l'altitude a été ajoutée;
e) l'Annexe I relative à la méthode d'évaluation de la forme de la surtension de foudre non normalisée a été ajoutée.
Elle a le statut de norme horizontale conformément au Guide IEC 108.

General Information

• Status: Published
• Publication Date: 15-Mar-2018
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 29.080.30 - Insulation systems
• Technical Committee: TC 28 - Insulation co-ordination
• Current Stage: DELPUB - Deleted Publication
• Start Date: 29-Nov-2019
• Completion Date: 24-May-2023

Relations

• Revises: IEC 60071-2:1996 - Insulation co-ordination - Part 2: Application guide
• Effective Date: 05-Sep-2023
• Revised: IEC 60071-2:2023 - Insulation co-ordination - Part 2: Application guidelines
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 60071-2 ®
Edition 4.0 2018-03
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
HORIZONTAL STANDARD
Insulation co-ordination –
Part 2: Application guidelines

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IEC 60071-2 ®
Edition 4.0 2018-03
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
HORIZONTAL STANDARD
Insulation co-ordination –
Part 2: Application guidelines

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.080.30 ISBN 978-2-8322-5498-1

– 2 – IEC 60071-2:2018 RLV  IEC 2018

CONTENTS
FOREWORD . 9

General .

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 Representative voltage stresses in service . 18
4.1 Origin and classification of voltage stresses . 18
4.2 Characteristics of overvoltage protective protection devices. 18
4.2.1 General remarks . 20
4.2.2 Metal-oxide surge arresters without gaps (MOSA) . 21
Spark gaps .
4.2.3 Line surge arresters (LSA) for overhead transmission and distribution
lines . 22
4.3 Representative voltages and overvoltages . 23
4.3.1 Continuous (power-frequency) voltage . 23
4.3.2 Temporary overvoltages . 23
4.3.3 Slow-front overvoltages . 27
4.3.4 Fast-front overvoltages . 33
4.3.5 Very-fast-front overvoltages [13] . 37
5 Co-ordination withstand voltage . 38
5.1 Insulation strength characteristics . 38
5.1.1 General . 38
5.1.2 Influence of polarity and overvoltage shapes . 40
5.1.3 Phase-to-phase and longitudinal insulation . 40
5.1.4 Influence of weather conditions on external insulation . 41
5.1.5 Probability of disruptive discharge of insulation . 41
5.2 Performance criterion . 43
5.3 Insulation co-ordination procedures . 43
5.3.1 General . 43

5.3.2 Insulation co-ordination procedures for continuous (power-frequency)
voltage and temporary overvoltage . 44
5.3.3 Insulation co-ordination procedures for slow-front overvoltages . 46
5.3.4 Insulation co-ordination procedures for fast-front overvoltages . 51
6 Required withstand voltage . 52
6.1 General remarks . 52
6.2 Atmospheric correction . 52
6.2.1 General remarks . 52
6.2.2 Altitude correction . 52
6.3 Safety factors. 54
6.3.1 General . 54
6.3.2 Ageing . 54
6.3.3 Production and assembly dispersion . 54
6.3.4 Inaccuracy of the withstand voltage . 54

6.3.5 Recommended safety factors (K ) . 55
s
7 Standard withstand voltage and testing procedures . 55

7.1 General remarks . 55

7.1.1 Overview . 55

7.1.2 Standard switching impulse withstand voltage . 55

7.1.3 Standard lightning impulse withstand voltage . 56

7.2 Test conversion factors . 56

7.2.1 Range I. 56

7.2.2 Range II . 57

7.3 Determination of insulation withstand by type tests . 57
7.3.1 Test procedure dependency upon insulation type . 57
7.3.2 Non-self-restoring insulation . 58
7.3.3 Self-restoring insulation . 58
7.3.4 Mixed insulation . 58
7.3.5 Limitations of the test procedures . 59
7.3.6 Selection of the type test procedures . 60
7.3.7 Selection of the type test voltages . 60
8 Special considerations for overhead lines . 61
8.1 General remarks . 61
8.2 Insulation co-ordination for operating voltages and temporary overvoltages . 61
8.3 Insulation co-ordination for slow-front overvoltages . 61
8.3.1 General . 61
8.3.2 Earth-fault overvoltages . 62
8.3.3 Energization and re-energization overvoltages . 62
8.4 Insulation co-ordination for lightning overvoltages . 62
8.4.1 General . 62
8.4.2 Distribution lines . 62
8.4.3 Transmission lines . 63
9 Special considerations for substations . 63
9.1 General remarks . 63
9.1.1 Overview . 63
9.1.2 Operating voltage . 63
9.1.3 Temporary overvoltage . 63
9.1.4 Slow-front overvoltages . 64
9.1.5 Fast-front overvoltages . 64

9.2 Insulation co-ordination for overvoltages . 64
9.2.1 Substations in distribution systems with U up to 36 kV in range I . 64
m
9.2.2 Substations in transmission systems with U between 52,5 kV and
m
245 kV in range I . 65
9.2.3 Substations in transmission systems in range II . 66
Annex (normative) Clearances in air to assure a specified impulse withstand voltage
installation .
Annex A (informative) Determination of temporary overvoltages due to earth faults . 71
Annex B (informative) Weibull probability distributions . 75
B.1 General remarks . 75
B.2 Disruptive discharge probability of external insulation . 76
B.3 Cumulative frequency distribution of overvoltages . 78
Annex C (informative) Determination of the representative slow-front overvoltage due
to line energization and re-energization . 81

– 4 – IEC 60071-2:2018 RLV  IEC 2018

C.1 General remarks .
...