DOWEI

CONTENTS

FOREWORD 4

1Scope 6

2Normative references 6

3Terms and definitions 7

4Abbreviated terms and symbols 14

4.1General 14

4.2Subscripts 14

4.3Letter symbols 14

4.4Abbreviations 15

5Procedure for insulation co-ordination 15

5.1General outline of the procedure 15

5.2Determination of the representative voltages and overvoltages (Urp) 16

5.3Determination of the co-ordination withstand voltages (Ucw) 18

5.4Determination of the required withstand voltage (Urw) 18

5.5Selection of the rated insulation level 19

5.6List of standard rated short-duration power frequency withstand voltages 20

5.7List of standard rated impulse withstand voltages 20

5.8Ranges for highest voltage for equipment 20

5.9Environmental conditions 20

5.9.1Normal environmental conditions 20

5.9.2Standard reference atmospheric conditions 20

5.10Selection of the standard insulation level 20

5.11Background of the standard insulation level 24

5.11.1General 24

5.11.2Standard rated switching impulse withstand voltage 25

5.11.3Standard rated lightning impulse withstand voltage 25

6Requirements for standard withstand voltage tests 25

6.1General requirements 25

6.2Standard short-duration power-frequency withstand voltage tests 26

6.3Standard impulse withstand voltage tests 26

6.4Alternative test situation 27

6.5Phase-to-phase and longitudinal insulation standard withstand voltage tests

for equipment in range I 27

6.5.1Power-frequency  tests 27

6.5.2Phase-to-phase (or longitudinal) insulation lightning impulse tests 28

6.6Phase-to-phase and longitudinal insulation standard withstand voltage tests

for equipment in range II 28

Annex A (normative)  Clearances in air to assure a specified impulse withstand voltage

installation 29

A.1General 29

A.2Lightning impulse 30

A.3Switching impulse 31

Annex B (informative)  Rated insulation levels for highest voltages of equipment Um

not standardized by IEC 33

Bibliography 34

Figure 1 – Flow chart for the determination of rated or standard insulation level 16

Table 1 – Classes and shapes of overvoltages, Standard voltage shapes and Standard withstand voltage tests 17

Table 2 – Standard insulation levels for range I (1 kV < Um ≤ 245 kV) 22

Table 3 – Standard insulation levels for range II (Um > 245 kV) 23

Table A.1 – Correlation between standard rated lightning impulse withstand voltages

and minimum air clearances 30

Table A.2 – Correlation between standard rated switching impulse withstand voltages

and minimum phase-to-earth air clearances 31

Table A.3 – Correlation between standard rated switching impulse withstand voltages

and minimum phase-to-phase air clearances 32

Table B.1 – Rated insulation levels for highest voltages of equipment Um not standardized by IEC 33

INSULATION CO-ORDINATION –

Part 1: Definitions, principles and rules

1 Scope

This part of IEC 60071 applies to three-phase AC systems having a highest voltage for equipment above 1 kV. It specifies the procedure for the selection of the rated withstand voltages for the phase-to-earth, phase-to-phase and longitudinal insulation of the equipment and the installations of these systems. It also gives the lists of the standard withstand voltages from which the rated withstand voltages are selected.

This document describes that the selected withstand voltages are associated with the highest voltage for equipment. This association is for insulation co-ordination purposes only. The requirements for human safety are not covered by this document.

Although the principles of this document also apply to transmission line insulation, the values of their withstand voltages can be different from the standard rated withstand voltages.

The apparatus committees are responsible for specifying the rated withstand voltages and the test procedures suitable for the relevant equipment taking into consideration the recommendations of this document.

NOTE  In IEC 60071-2, all rules for insulation co-ordination given in this document are justified in detail, in particular the association of the standard rated withstand voltages with the highest voltage for equipment. When more than one set of standard rated withstand voltages is associated with the same highest voltage for equipment, guidance is provided for the selection of the most suitable set.

This  horizontal  standard  is  primarily  intended  for  use  by  technical  committees  in  the preparation of standards in accordance with the principles laid down in IEC Guide 108.

One of the responsibilities of a technical committee is, wherever applicable, to make use of horizontal standards in the preparation of its publications. The contents of this horizontal standard will not apply unless specifically referred to or included in the relevant publications.

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 60038, IEC standard voltages

IEC 60060-1, High-voltage test techniques – Part 1: General definitions and test requirements

IEC 60071-2, Insulation co-ordination – Part 2: Application guidelines

IEC 60099-4, Surge arresters – Part 4: Metal-oxide surge arresters without gaps for a.c. systems

Table 2 – Standard insulation levels for range I (1 kV < Um ≤ 245 kV)

Table 3 – Standard insulation levels for range II (Um > 245 kV) (1 of 2)

Bibliography

IEC 60050-614:2016,  International  electrotechnical  vocabulary  –  Part  614:  Generation, transmission and distribution of electricity – Operation

IEC 60507, Artificial pollution tests on high-voltage ceramic and glass insulators to be used on a.c. systems

IEC 60633, High-voltage direct current (HVDC) transmission – Vocabulary

IEC TS 60815-1, Selection and dimensioning of high-voltage insulators intended for use in polluted conditions – Part 1: Definitions, information and general principles

IEC Guide 108, Guidelines for ensuring the coherency of IEC publications – Application of horizontal standards