EN 62535:2009

SLOVENSKI STANDARD
01-april-2009
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Insulating liquids - Test method for detection of potentially corrosive sulphur in used and
unused insulating oil (IEC 62535:2008)
Isolierflüssigkeiten - Prüfverfahren für den Nachweis von potenziell korrosivem Schwefel
in gebrauchtem und ungebrauchtem Isolieröl (IEC 62535:2008)
Liquides isolants - Méthode d'essai pour la détection du soufre potentiellement corrosif
dans les huiles usagées et neuves (CEI 62535:2008)
Ta slovenski standard je istoveten z: EN 62535:2009
ICS:
29.040.10 Izolacijska olja Insulating oils
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 62535
NORME EUROPÉENNE
January 2009
EUROPÄISCHE NORM
ICS 29.040.10
English version
Insulating liquids -
Test method for detection of potentially corrosive sulphur
in used and unused insulating oil
(IEC 62535:2008)
Liquides isolants -  Isolierflüssigkeiten -
Méthode d'essai pour la détection Prüfverfahren für den Nachweis
du soufre potentiellement corrosif von potenziell korrosivem Schwefel in
dans les huiles usagées et neuves gebrauchtem und ungebrauchtem Isolieröl
(CEI 62535:2008) (IEC 62535:2008)

This European Standard was approved by CENELEC on 2008-12-01. 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, Bulgaria, Cyprus, the
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.

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

Central Secretariat: avenue Marnix 17, B - 1000 Brussels

© 2009 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62535:2009 E
Foreword
The text of document 10/746/FDIS, future edition 1 of IEC 62535, prepared by IEC TC 10, Fluids for
electrotechnical applications, was submitted to the IEC-CENELEC parallel vote and was approved by
CENELEC as EN 62535 on 2008-12-01.
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) 2009-09-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2011-12-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 62535:2008 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 60567 NOTE  Harmonized as EN 60567:2005 (not modified).
__________
– 3 – EN 62535:2009
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following referenced documents are indispensable for the application 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  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year

1)
- Copper and copper alloys - Copper rod, bar EN 13601 -
-
and wire for general electrical purposes

1)
IEC 60475 - Method of sampling liquid dielectrics - -

1)
IEC 60554-3-1 - Specification for cellulosic papers for - -
electrical purposes -
Part 3: Specifications for individual
materials - Sheet 1: General purpose
electrical paper
1)
ASTM D1275 - Methods A and B: Standard test method for - -
corrosive sulfur in electrical insulating oils

1)
ASTM D130 - Standard test method for corrosiveness to - -
copper from petroleum products by copper
strip test
1)
DIN 51353 - Testing of insulating oils; detection of - -
corrosive sulfur; silver strip test

1)
Undated reference.
IEC 62535
Edition 1.0 2008-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Insulating liquids – Test method for detection of potentially corrosive sulphur in
used and unused insulating oil

Liquides isolants – Méthode d’essai pour la détection du soufre potentiellement
corrosif dans les huiles usagées et neuves

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
P
CODE PRIX
ICS 29.040.10 ISBN 2-8318-1004-6
– 2 – 62535 © IEC:2008
CONTENTS
FOREWORD.3
INTRODUCTION.5
1 Scope.6
2 Normative references .6
3 Terms and definitions .6
4 Sampling .7
5 Procedure .7
5.1 Principle.7
5.2 Apparatus and materials.7
5.3 Method.8
6 Inspection and interpretation .8
6.1 General .8
6.2 Copper .9
6.3 Paper .9
6.4 Result .9
7 Repeatability and reproducibility.9
8 Report .10
Annex A (informative) Copper strip method to detect corrosive and potentially
corrosive sulphur in oil.11
Annex B (informative) Analysis for copper sulphide on insulating paper by scanning
electron microscope-energy dispersive X-ray spectrometry (SEM/EDX) .14
Bibliography.16

62535 © IEC:2008 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INSULATING LIQUIDS –
TEST METHOD FOR DETECTION OF POTENTIALLY CORROSIVE
SULPHUR IN USED AND UNUSED INSULATING OIL

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
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
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 62535 has been prepared by IEC technical committee 10: Fluids
for electrotechnical applications.
The text of this standard is based on the following documents:
FDIS Report on voting
10/746/FDIS 10/749/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.

– 4 – 62535 © IEC:2008
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition; or
• amended.
62535 © IEC:2008 – 5 –
INTRODUCTION
In recent years, several failures of transformers and reactors due to copper sulphide
formation in/on the cellulose insulation have been reported worldwide. The tendency of
transformer oils to form copper sulphide in the presence of copper is seen as one of the major
contributing factors.
The most common reason for such failures is arcing between adjacent disks or conductors of
a winding, due to the formation of deposits of copper sulphide on the cellulosic insulating
paper.
It has been demonstrated that existing test methods for corrosive sulphur, ASTM D1275
method A and DIN 51353, are unable to detect oils having potentially corrosive behaviour.
For this reason, IEC technical committee 10 has prepared this International Standard for the
detection of potentially corrosive sulphur in mineral insulating oils. The wrapped conductor
test method is suitable for used and unused mineral oils.
This test method is based on a study performed by Conseil International des Grands Réseaux
Electriques (CIGRE) working group A2.32 [1] .
Health and safety
This International Standard does not purport to address all the safety problems associated
with its use. It is the responsibility of the user of the standard to establish appropriate health
and safety practices and determine the applicability of regulatory limitations prior to use.
The mineral oils wh
...