IEC 60071-1:2019

IEC 60071-1 ®
Edition 9.0 2019-08
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
HORIZONTAL STANDARD
Insulation co-ordination –
Part 1: Definitions, principles and rules

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IEC 60071-1 ®
Edition 9.0 2019-08
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
HORIZONTAL STANDARD
Insulation co-ordination –
Part 1: Definitions, principles and rules

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.080.30 ISBN 978-2-8322-7295-4

– 2 – IEC 60071-1:2019 RLV  IEC 2019
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Abbreviated terms and symbols . 10
4.1 General . 15
4.2 Subscripts . 15
4.3 Letter symbols . 15
4.4 Abbreviations . 16
5 Procedure for insulation co-ordination . 16
5.1 General outline of the procedure . 16
5.2 Determination of the representative voltages and overvoltages (U ) . 17
rp
5.3 Determination of the co-ordination withstand voltages (U ) . 19
cw
5.4 Determination of the required withstand voltage (U ) . 19
rw
5.5 Selection of the rated insulation level . 20
5.6 List of standard rated short-duration power frequency withstand voltages . 21
5.7 List of standard rated impulse withstand voltages . 21
5.8 Ranges for highest voltage for equipment . 21
5.9 Environmental conditions . 21
5.9.1 Normal environmental conditions . 21
5.9.2 Standard reference atmospheric conditions . 21
5.10 Selection of the standard insulation level . 22
5.11 Background of the standard insulation level . 26
5.11.1 General . 26
5.11.2 Standard rated switching impulse withstand voltage . 27
5.11.3 Standard rated lightning impulse withstand voltage . 27
6 Requirements for standard withstand voltage tests . 27
6.1 General requirements . 27
6.2 Standard short-duration power-frequency withstand voltage tests . 28
6.3 Standard impulse withstand voltage tests. 28
6.4 Alternative test situation . 29
6.5 Phase-to-phase and longitudinal insulation standard withstand voltage tests
for equipment in range I . 29
6.5.1 Power-frequency tests . 29
6.5.2 Phase-to-phase (or longitudinal) insulation lightning impulse tests . 30
6.6 Phase-to-phase and longitudinal insulation standard withstand voltage tests
for equipment in range II . 30
Annex A (normative) Clearances in air to assure a specified impulse withstand voltage
installation . 31
A.1 General . 31
A.2 Range I Lightning impulse . 32
A.3 Range II Switching impulse . 34
Annex B (informative) Values of Rated insulation levels for 1kV < U ≤ 245 kV for
m
highest voltages for of equipment, U , not standardized by IEC based on current
m
practice in some countries . 36
Bibliography . 37

Figure 1 – Flow chart for the determination of rated or standard insulation level . 17

Table 1 – Classes and shapes of overvoltages, Standard voltage shapes and Standard
withstand voltage tests . 18
Table 2 – Standard insulation levels for range I (1 kV < U ≤ 245 kV) . 24
m
Table 3 – Standard insulation levels for range II (U > 245 kV) . 25
m
Table A.1 – Correlation between standard rated lightning impulse withstand voltages
and minimum air clearances . 33
Table A.2 – Correlation between standard rated switching impulse withstand voltages
and minimum phase-to-earth air clearances . 34
Table A.3 – Correlation between standard rated switching impulse withstand voltages
and minimum phase-to-phase air clearances . 35
Table B.1- Values of rated insulation levels for 1kV < U ≤ 245 kV for highest voltages
m
for equipment U not standardized by IEC based on current practice in some countries .
m
Table B.1 – Rated insulation levels for highest voltages of equipment U not
m
standardized by IEC. 36

– 4 – IEC 60071-1:2019 RLV  IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
INSULATION CO-ORDINATION –
Part 1: Definitions, principles and rules

FOREWORD
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International Standard IEC 60071-1 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.
This ninth edition cancels and replaces the eighth edition published in 2006 and
Amendment 1:2010. This edition constitutes a technical revision.
It has the status of a horizontal standard in accordance with IEC Guide 108.
The main changes from the previous edition are as follows:
a) all references are updated to current IEC standards, and the bibliography is deleted;
b) some definitions are clarified in order to avoid overlapping and ensure clear understanding;
c) letter symbols are changed and corrected in order to keep the consistency with relevant
IEC standards;
d) some ti
...