EN IEC 60071-2:2023

SLOVENSKI STANDARD
01-september-2023
Koordinacija izolacije - 2. del: Smernice za uporabo (predlagan horizontalni
standard)
Insulation co-ordination - Part 2: Application guidelines (Proposed horizontal standard)
Isolationskoordination – Teil 2: Anwendungsrichtlinie
Coordination de l'isolement - Partie 2: Lignes directrices en matière d'application
Ta slovenski standard je istoveten z: EN IEC 60071-2:2023
ICS:
29.080.01 Električna izolacija na Electrical insulation in
splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 60071-2

NORME EUROPÉENNE
EUROPÄISCHE NORM June 2023
ICS 29.080.30 Supersedes EN IEC 60071-2:2018
English Version
Insulation co-ordination - Part 2: Application guidelines
(IEC 60071-2:2023)
Coordination de l'isolement - Partie 2: Lignes directrices en Isolationskoordination - Teil 2: Anwendungsrichtlinie
matière d'application (IEC 60071-2:2023)
(IEC 60071-2:2023)
This European Standard was approved by CENELEC on 2023-06-28. 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
© 2023 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60071-2:2023 E

European foreword
The text of document 99/356/CDV, future edition 5 of IEC 60071-2, 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
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2024-03-28
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2026-06-28
document have to be withdrawn
This document supersedes EN IEC 60071-2:2018 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 60071-2:2023 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 60099-4:2014 NOTE Approved as EN 60099-4:2014 (not modified)
IEC 60099-5 NOTE Approved as EN IEC 60099-5
IEC 60099-8 NOTE Approved as EN IEC 60099-8
IEC 60507 NOTE Approved as EN 60507
IEC 62271-1:2017 NOTE Approved as EN 62271-1:2017 (not modified)
IEC 62271-100:2008 NOTE Approved as EN 62271-100:2009 (not modified)
IEC 60721-2-3:2013 NOTE Approved as EN 60721-2-3:2014 (not modified)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60060-1 2010 High-voltage test techniques - Part 1: EN 60060-1 2010
General definitions and test requirements
IEC 60071-1 2019 Insulation co-ordination - Part 1: EN IEC 60071-1 2019
Definitions, principles and rules
IEC 60505 2011 Evaluation and qualification of electrical EN 60505 2011
insulation 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/TR 60071-4 2004 Insulation co-ordination - Part 4: - -
Computational guide to insulation co-
ordination and modelling of electrical
networks
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

IEC 60071-2:2023 © IEC 2023 – 3 –
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 . 68
9.2.1 General . 68
9.2.2 Insulation co-ordination for operating voltages and temporary
overvoltages . 68
9.2.3 Insulation co-ordination for slow-front overvoltages . 68
9.2.4 Insulation co-ordination for fast-front overvoltages . 69
9.2.5 Overvoltage protection of cable lines . 69
9.3 GIL (gas insulated transmission line) / GIB (Gas-insulated busduct) . 70
9.3.1 General . 70
9.3.2 Insulation co-ordination for operating voltages and temporary
overvoltages . 70
9.3.3 Insulation co-ordination for slow-front overvoltages . 70
9.3.4 Insulation co-ordination for fast-front overvoltages . 71
9.3.5 Overvoltage protection of GIL/GIB lines . 71
9.4 Substation . 71
9.4.1 General . 71
9.4.2 Insulation co-ordination for overvoltages. 72
Annex A (informative) Determination of temporary overvoltages due to earth faults . 75
Annex B (informative) Weibull probability distributions . 79

– 4 – IEC 60071-2:2023 © IEC 2023
B.1 General remarks . 79
B.2 Disruptive discharge probability of external insulation . 80
B.3 Cumulative frequency distribution of overvoltages . 83
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 . 86
C.3 Probability distribution of the representative amplitude of the prospective

overvoltage phase-to-phase . 89
C.4 Insulation characteristic . 90
C.5 Numerical example . 93
Annex D (informative) Transferred overvoltages in transformers . 98
D.1 General remarks . 98
D.2 Transferred temporary overvoltages . 99
D.3 Capacitively transferred surges . 99
D.4 Inductively transferred surges . 101
Annex E (informative) Determination of lightning overvoltages by simplified method . 105
E.1 General remarks . 105
E.2 Determination of the limit distance (X ) . 105
p
E.2.1 Protection with arresters in the substation . 105
E.2.2 Self-protection of substation . 106
E.3 Estimation of the representative lightning overvoltage amplitude. 107
E.3.1 General . 107
E.3.2 Shielding penetration . 107
E.3.3 Back flashovers . 108
E.4 Simplified approach . 110
E.5 Assumed maximum value of the representative lightning overvoltage . 112
Annex F (informative) Calculation of air gap breakdown strength from experimental

data . 114
F.1 General . 114
F.2 Insulation response to power-frequency voltages . 114
F.3 Insulation response to slow-front overvoltages . 115
F.4 Insulation response to fast-front overvoltages . 116
Annex G (informative) Examples of insulation co-ordination procedure . 120
G.1 Overview. 120
G.2 Numerical example for a system in range I (with nominal voltage of 230 kV) . 120
G.2.1 General . 120
G.2.2 Part 1: no special operating conditions . 121
G.2.3 Part 2: influence of capacitor switching at station 2 . 128
G.2.4 Part 3: flow charts related to the example of Clause G.2 . 130
G.3 Numerical example for a system in range II (with nominal voltage of 735 kV) . 135
G.3.1 General . 135
G.3.2 Step 1: determination of the representative overvoltages –
values of U . 135
rp
G.3.3 Step 2: determination of the co-ordination withstand voltages –
values of U . 136
cw
G.3.4 Step 3: determination of the required withstand voltages – values of
U . 137
rw
IEC 60071-2:2023 © IEC 2023 – 5 –
G.3.5 Step 4: conversion to switching impulse withstand voltages (SIWV) . 138
G.3.6 Step 5: selection of standard insulation levels . 139
G.3.7 Considerations relative to phase-to-phase insulation co-ordination . 139
G.3.8 Phase-to-earth clearances . 140
G.3.9 Phase-to-phase clearances . 141
G.4 Numerical example for substations in distribution systems with U up to
m
36 kV in range I . 141
G.4.1 General . 141
G.4.2 Step 1: determination of the representative overvoltages –
values of U . 142
rp
G.4.3 Step 2: determination of the co-ordination withstand voltages –

values of U . 142
cw
G.4.4 Step 3: determination of required withstand voltages – values of U . 143
rw
G.4.5 Step 4: conversion to standard short-duration power-frequency and
lightning impulse withstand voltages . 144
G.4.6 Step 5: selection of standard withstand voltages . 145
G.4.7 Summary of insulation co-ordination procedure for the example of

Clause G.4 . 145
Annex H (informative) Atmospheric correction – Altitude correction application
example . 147
H.1 General principles . 147
H.1.1 Atmospheric correction in standard tests . 147
H.1.2 Task of atmospheric correction in insulation co-ordination . 148
H.2 Atmospheric correction in insulation co-ordination . 150
H.2.1 Factors for atmospheric correction . 150
H.2.2 General characteristics for moderate climates . 150
H.2.3 Special atmospheric conditions . 151
H.2.4 Altitude dependency of air pressure . 152
H.3 Altitude correction . 153
H.3.1 Definition of the altitude correction factor . 153
H.3.2 Principle of altitude correction . 154
H.3.3 Altitude correction for standard equipment operating at altitudes up to
1 000 m . 155
H.3.4 Altitude correction for standard equipment operating at altitudes above
1 000 m . 156
H.4 Selection of the exponent m . 156
H.4.1 General . 156
H.4.2 Derivation of exponent m for switching impulse voltage . 157
H.4.3 Derivation of exponent m for critical switching impulse voltage . 159
Annex I (informative) Evaluation method of non-standard lightning overvoltage shape
for representative voltages and overvoltages . 162
I.1 General remarks . 162
I.2 Lightning overvoltage shape . 162
I.3 Evaluation method for GIS . 162
I.3.1 Experiments . 162
I.3.2 Evaluation of overvoltage shape . 163
I.4 Evaluation method for transformer . 163
I.4.1 Experiments . 163
I.4.2 Evaluation of overvoltage shape . 164

– 6 – IEC 60071-2:2023 © IEC 2023
Annex J (informative) Insulation co-ordination for very-fast-front overvoltages in UHV
substations . 169
J.1 General . 169
J.2 Influence of disconnector design . 169
J.3 Insulation co-ordination for VFFO . 170
Annex K (informative) Application of shunt reactors to limit TOV and SFO of high
voltage overhead transmission line . 172
K.1 General remarks . 172
K.2 Limitation of TOV and SFO . 172
K.3 Application of the neutral grounding reactor to limit resonance overvoltage
and secondary arc current . 172
K.4 SFO and Beat frequency overvoltage limited by neutral arrester . 173
K.5 SFO and FFO due to SR de-energization . 174
K.6 Limitation of TOV by Controllable SR . 174
K.7 Insulation coordination of the SR and neutral grounding reactor . 174
K.8 Self-excitation TOV of synchronous generator . 174
Annex L (informative) Calculation of lightning stroke rate and lightning outage rate . 175
L.1 General . 175
L.2 Description in CIGRE [37] . 175
L.3 Flash program in IEEE [49] . 176
L.4 [Case Study] Calculation of Lightning Stroke Rate and Lightning Outage
Rate (Appendix D in CIGRE TB 839 [37]) . 176
L.4.1 Basic flow of calculation method . 176
L.4.2 Comparison of Calculation Results with Observations . 179
Bibliography . 181

Figure 1 – Range of 2 % slow-front overvoltages at the receiving end due to line
energization and re-energization [27] . 28
Figure 2 – Ratio between the 2 % values of slow-front overvoltages phase-to-phase

and phase-to-earth [28], [29] . 29
Figure 3 – Diagram for surge arrester connection to the protected object . 36
Figure 4 – Modelling of transmission lines and substations/power stations . 42
Figure 5 – Distributive discharge probability of self-restoring insulation described on a
linear scale . 51
Figure 6 – Disruptive discharge probability of self-restoring insulation described on a
Gaussian scale . 52
Figure 7 – Evaluation of deterministic co-ordination factor K . 52
cd
Figure 8 – Evaluation of the risk of failure . 53
Figure 9 – Risk of failure of external insulation for slow-front overvoltages as a function

of the statistical co-ordination factor K . 55
cs
Figure 10 – Dependence of exponent m on the co-ordination switching impulse
withstand voltage . 58
Figure 11 – Probability P of an equipment to pass the test dependent on the difference
K between the actual and the rated impulse withstand voltage . 64
Figure 12 – Example of a schematic substation layout used for the overvoltage stress
location . 71
Figure A.1 – Earth fault factor k on a base of X /X for R /X = R = 0 . 76
0 1 1 1 f
IEC 60071-2:2023 © IEC 2023 – 7 –
Figure A.2 – Relationship between R /X and X /X for constant values of earth fault
0 1 0 1
factor k where R = 0 . 76
Figure A.3 – Relationship between R /X and X /X for constant values of earth fault
0 1 0 1
factor k where R = 0,5 X . 77
1 1
Figure A.4 – Relationship between R /X and X /X for constant values of earth fault
0 1 0 1
factor k where R = X . 77
1 1
Figure A.5 – Relationship between R /X and X /X for constant values of earth fault
0 1 0 1
factor k where R = 2X . 78
1 1
Figure B.1 – Conversion chart for the reduction of the withstand voltage due to placing

insulation configurations in parallel . 85
Figure C.1 – Probability density and cumulative distribution for derivation of the
representative overvoltage phase-to-earth . 86
Figure C.2 – Example for bivariate phase-to-phase overvoltage curves with constant
probability density and tangents giving the relevant 2 % values . 94
Figure C.3 – Principle of the determination of the representative phase-to-phase

overvoltage U . 95
pre
Figure C.4 – Schematic phase-phase-earth insulation configuration . 96
Figure C.5 – Description of the 50 % switching impulse flashover voltage of a phase-
phase-earth insulation . 96
Figure C.6 – Inclination angle of the phase-to-phase insulation characteristic in range
"b" dependent on the ratio of the phase-phase clearance D to the height H above
t
earth . 97
Figure D.1 – Distributed capacitances of the windings of a transformer and the
equivalent circuit describing the windings . 103
Figure D.2 – Values of factor J describing the effect of the winding connections on the
inductive surge transference . 104
Figure H.1 – Principle of the atmospheric correction during test of a specified

insulation level according to the procedure of IEC 60060-1 . 148
Figure H.2 – Principal task of the atmospheric correction in insulation co-ordination
according to IEC 60071-1 . 149
Figure H.3 – Comparison of atmospheric correction δ × k with relative air pressure
h
p/p for various weather stations around the world . 152
Figure H.4 – Deviation of simplified pressure calculation by exponential function in this

document from the temperature dependent pressure calculation of ISO 2533 . 153
Figure H.5 – Principle of altitude correction: decreasing withstand voltage U of
equipment with increasing altitude . 155
Figure H.6 – Sets of m-curves for standard switching impulse voltage including the
variations in altitude for each gap factor . 159
Figure H.7 – Exponent m for standard switching impulse voltage for selected gap
factors covering altitudes up to 4 000 m . 159
Figure H.8 – Sets of m-curves for critical switching impulse voltage including the
variations in altitude for each gap factor . 160
Figure H.9 – Exponent m for critical switching impulse voltage for selected gap factors
covering altitudes up to 4 000 m . 160
Figure H.10 – Accordance of m-curves from Figure 10 with determination of exponent
m by means of critical switching impulse voltage for selected gap factors and altitudes. 161
Figure I.1 – Examples of lightning overvoltage shapes . 164

– 8 – IEC 60071-2:2023 © IEC 2023
Figure I.2 – Example of insulation characteristics with respect to lightning overvoltages
of the SF gas gap (Shape E) . 165
Figure I.3 – Calculation of duration time T . 165
d
Figure I.4 – Shape evaluation flow for GIS and transformer . 166
Figure I.5 – Application to GIS lightning overvoltage . 167
Figure I.6 – Example of insulation characteristics with respect to lightning overvoltage
of the turn-to-turn insulation (Shape C) . 167
Figure I.7 – Application to transformer lightning overvoltage . 168
Figure J.1 – Insulation co-ordination for very-fast-front overvoltages. 171
Figure L.1 – Outline of the CIGRE method for lightning performance of an overhead
line . 176
Figure L.2 – Flowchart to calculate lightning outage rate of transmission lines . 178
Figure L.3 – Typical conductor arrangements of large-scale transmission lines . 179
Figure L.4 – Lightning stroke rate to power lines -calculations and observations- . 179
Figure L.5 – Lightning outage rate -calculations and observations- . 180

Table 1 – Test conversion factors for range I, to convert required SIWV to SDWV and
LIWV . 61
Table 2 – Test conversion factors for range II to convert required SDWV to SIWV . 62
Table 3 – Selectivity of test procedures B and C of IEC 60060-1 . 63
Table B.1 – Breakdown voltage versus cumulative flashover probability – Single

insulation and 100 parallel insulations . 82
Table E.1 – Corona damping constant K . 106
co
Table E.2 – Factor A for various overhead lines . 112
Table F.1 – Typical gap factors K for switching impulse breakdown phase-to-earth
(according to [1] and [4]) . 118
Table F.2 – Gap factors for typical phase-to-phase geometries . 119
Table G.1 – Summary of minimum required withstand voltages obtained for the
example shown in G.2.2 . 127
Table G.2 – Summary of required withstand voltages obtained for the example shown
in G.2.3 . 129
Table G.3 – Values related to the insulation co-ordination procedure for the example
in G.4. 146
Table H.1 – Comparison of functional expressions of Figure 10 with the selected
parameters from the derivation of m-curves with critical switching impulse . 161
Table I.1 – Evaluation of the lightning overvoltage in the GIS of UHV system . 165
Table I.2 – Evaluation of lightning overvoltage in the transformer of 500 kV system . 168

IEC 60071-2:2023 © IEC 2023 – 9 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INSULATION CO-ORDINATION –
Part 2: Application guidelines

FOREWORD
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