EN 61472:2004

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EUROPEAN STANDARD EN 61472
NORME EUROPÉENNE
EUROPÄISCHE NORM November 2004

ICS 13.260; 29.240.20; 29.260.99

English version
Live working –
Minimum approach distances for a.c. systems
in the voltage range 72,5 kV to 800 kV –
A method of calculation
(IEC 61472:2004)
Travaux sous tension –  Arbeiten unter Spannung –
Distances minimales d'approche Mindest-Arbeitsabstände für
pour des réseaux à courant alternatif Wechselspannungsnetze im
de tension comprise entre 72,5 kV Spannungsbereich von 72,5 kV
et 800 kV – bis 800 kV –
Une méthode de calcul Berechnungsverfahren
(CEI 61472:2004) (IEC 61472:2004)

This European Standard was approved by CENELEC on 2004-10-01. 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 Central Secretariat 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 Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2004 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 61472:2004 E
Foreword
The text of document 78/582/FDIS, future edition 2 of IEC 61472, prepared by IEC TC 78, Live
working, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 61472 on 2004-10-01.
This standard has been prepared according to the requirements of EN 61477: Live working –
Minimum requirements for the utilization of tools,devices and equipement, where applicable.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2005-07-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2007-10-01
__________
Endorsement notice
The text of the International Standard IEC 61472:2004 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 standards indicated:
IEC 60060-1 NOTE Harmonized as HD 588.1 S1:1991 (not modified).
IEC 60071-1 NOTE Harmonized as EN 60071-1:1995 (not modified).
IEC 60071-2 NOTE Harmonized as EN 60071-2:1997 (not modified).
IEC 60743 NOTE Harmonized as EN 60743:2001 (not modified).
IEC 61477 NOTE Harmonized as EN 61477:2002 (not modified).

__________
NORME CEI
INTERNATIONALE IEC
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
2004-07
Travaux sous tension –
Distances minimales d'approche
pour des réseaux à courant alternatif
de tension comprise entre 72,5 kV
et 800 kV –
Une méthode de calcul
Live working –
Minimum approach distances
for a.c. systems in the voltage range
72,5 kV to 800 kV –
A method of calculation
© IEC 2004 Droits de reproduction réservés ⎯ Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
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Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
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Pour prix, voir catalogue en vigueur
For price, see current catalogue

61472 © IEC:2004 – 3 –
CONTENTS
FOREWORD.7
1 Scope.11
2 Terms, definitions and symbols .11
3 Methodology.17
4 Factors influencing calculations.19
5 Evaluation of risks.27
6 Calculation of minimum approach distance D .29
A
Annex A (informative) Ergonomic distance.37
Annex B (informative) Overvoltages.41
Annex C (informative) Dielectric strength of air .49
Annex D (informative) Gap factor k .53
g
Annex E (informative) Allowing for atmospheric conditions .57
Annex F (informative) Influence of electrically floating objects on the dielectric strength .65
Annex G (informative) Live working near contaminated, damaged or moist insulation .79
Bibliography.85
Figure 1 – Illustration of two floating objects of different dimensions and at different
distances from the axis of the gap (see 4.3.4).33
Figure 2 – Typical live working tasks (see Clause 2 and 4.3.4) .35
Figure B.1 – Ranges of u at the open ended line due to closing and reclosing
e2
according to the type of network (meshed or antenna) with and without closing
resistors and shunt reactors (see B.2.1.1).47
Figure F.1 – Reduction in the discharge voltage of the air gap due to alteration in the
electric field caused by the presence of a floating-potential conductive object in critical
position along the axis of the gap (phase to earth rod-rod configuration) –
250 µs /2 500 µs impulse (see F.3.1.2 et F.3.1.3) .73
Figure F.2 – Reduction in the discharge voltage of the air gap due to alteration in the
electric field caused by the presence of a floating-potential conductive object in critical
position along the axis of the gap (phase to phase conductor-conductor configuration)
– 250 µs /2 500 µs impulse (see F.3.1.2 et F.3.1.3) .75
Figure F.3 – Reduction of the dielectric strength as a function of the clearance D for
constant values of β – Phase to earth rod-rod configuration (see F.3.1.3 and F.3.2) .77
Figure F.4 – Reduction of the dielectric strength as a function of the clearance D for
constant values of β – Phase to phase conductor-conductor configuration (see F.3.1.3
and F.3.2) .77

61472 © IEC:2004 – 5 –
Table 1 – Floating object factor k .25
f
Table 2 – Example of calculation of electrical distance for some switching overvoltage
values.31
Table B.1 – Classification of overvoltages according to IEC 60071-1 .45
Table D.1 – Gap factors for some actual phase to earth configurations .55
Table E.1 – Atmospheric factor k for different reference altitudes and values of U .61
a 90
Table G.1 – Example of maximum number of damaged insulators calculation (gap
factor 1,4) .81
Table G.2 – Example of maximum number of damaged insulators calculation (gap
factor 1,2) .83

61472 © IEC:2004 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LIVE WORKING –
MINIMUM APPROACH DISTANCES FOR AC SYSTEMS
IN THE VOLTAGE RANGE 72,5 kV TO 800 kV –
A METHOD OF CALCULATION
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61472 has been prepared by technical committee 78: Live
working.
This second edition cancels and replaces the first edition of IEC 61472 published in 1998.
This second edition constitutes a technical revision.
This document has been prepared according to the requirements of IEC 61477: Live working
– Minimum requirements for the utilization of tools, devices and equipment, where applicable.

61472 © IEC:2004 – 9 –
Significant changes with regard to the first edition are the following: this second edition
– revises the application range of this method of calculation to 72,5 kV and above;
– expands in a detailed manner the calculation of the influence of floating objects;
– refers closely to the relevant brochures of CIGRE and to IEC 60071-2.
The text of this standard is based on the following documents:
FDIS Report on voting
78/582/FDIS 78/586/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publicatio
...