IEC 62770:2024

IEC 62770 ®
Edition 2.0 2024-10
COMMENTED VERSION
INTERNATIONAL
STANDARD
colour
inside
Fluids for electrotechnical applications – Unused natural esters for transformers
and similar electrical equipment
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Secretariat Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform IEC Products & Services Portal - products.iec.ch
The advanced search enables to find IEC publications by a
Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews, graphical symbols and the glossary.
committee, …). It also gives information on projects, replaced With a subscription you will always have access to up to date
and withdrawn publications. content tailored to your needs.

IEC Just Published - webstore.iec.ch/justpublished
Electropedia - www.electropedia.org
Stay up to date on all new IEC publications. Just Published
The world's leading online dictionary on electrotechnology,
details all new publications released. Available online and
containing more than 22 500 terminological entries in English
once a month by email.
and French, with equivalent terms in 25 additional languages.

Also known as the International Electrotechnical Vocabulary
IEC Customer Service Centre - webstore.iec.ch/csc
(IEV) online.
If you wish to give us your feedback on this publication or

need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
IEC 62770 ®
Edition 2.0 2024-10
COMMENTED VERSION
INTERNATIONAL
STANDARD
colour
inside
Fluids for electrotechnical applications – Unused natural esters for transformers
and similar electrical equipment
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.040.01 ISBN 978-2-8322-9859-6
– 2 – IEC 62770:2024 CMV © IEC 2024
CONTENTS
FOREWORD .4
INTRODUCTION .6
1 Scope .7
2 Normative references .7
3 Terms, definitions and abbreviated terms .9
3.1 Terms and definitions .9
3.2 Abbreviated terms . 10
4 Properties, their significance and test methods . 10
4.1 General . 10
4.2 Physical properties . 10
4.2.1 Appearance and colour . 10
4.2.2 Viscosity . 10
4.2.3 Pour point . 11
4.2.4 Water content . 11
4.2.5 Density . 12
4.3 Electrical properties . 12
4.3.1 Breakdown voltage . 12
4.3.2 Dielectric dissipation factor (DDF) . 12
4.3.3 Relative permittivity (dielectric constant) . 12
4.4 Chemical properties . 12
4.4.1 Acidity . 12
4.4.2 Corrosive sulfur . 12
4.4.3 Additive content. 12
4.4.4 Furfural content . 13
4.5 Performance . 13
4.5.1 General . 13
4.5.2 Oxidation stability . 13
4.6 Health, safety and environmental (HSE) properties . 14
4.6.1 Fire point and flash point . 14
4.6.2 Polychlorinated biphenyls (PCBs) . 14
4.6.3 Biodegradation . 14
4.6.4 Aquatic toxicity . 14
5 Classification, identification, general delivery requirements, and sampling . 15
5.1 Classification . 15
5.2 Identification and general delivery requirements . 15
5.3 Sampling . 15
Annexe A (normative) Summary of the test method for evaluating oxidation stability
of unused natural esters . 17
A.1 Introductory remark General . 17
A.2 Test conditions . 17
A.3 Precision . 17
A.4 Relative repeatability (r) . 17
A.5 Relative reproducibility (R) . 17
Annex B (informative) Specifications of low-viscosity insulating fluids derived from
natural esters .
Bibliography . 19

List of comments . 21

Table 1 – Abbreviated terms . 10
Table 2 – General specifications . 16
Table A.1 – Relative repeatability and relative reproducibility obtained for different
parameters during RRT . 17
Table B.1 – Specifications for low-viscosity of monoesters derived from natural esters .

– 4 – IEC 62770:2024 CMV © IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FLUIDS FOR ELECTROTECHNICAL APPLICATIONS –
UNUSED NATURAL ESTERS FOR TRANSFORMERS
AND SIMILAR ELECTRICAL EQUIPMENT

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 itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
This commented version (CMV) of the official standard IEC 62770:2024 edition 2.0 allows
the user to identify the changes made to the previous IEC 62770:2013
edition 1.0. Furthermore, comments from IEC TC 10 experts are provided to explain the
reasons of the most relevant changes, or to clarify any part of the content.
A vertical bar appears in the margin wherever a change has been made. Additions are in
green text, deletions are in strikethrough red text. Experts' comments are identified by a
blue-background number. Mouse over a number to display a pop-up note with the
comment.
This publication contains the CMV and the official standard. The full list of comments is
available at the end of the CMV.

IEC 62770 has been prepared by IEC technical committee 10: Fluids for electrotechnical
applications. It is an International Standard.
This second edition cancels and replaces the first edition published in 2013. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition: 1
a) Introduction of IEC 63012 which details other liquids not covered by this document.
IEC 63012 was published in 2019 after the first edition of IEC 62770 (2013).
b) New Table 1 inserted which clarifies definitions.
c) Appearance and colour requirements now merged.
d) Pour p
...