SIST EN IEC 62770:2025

SLOVENSKI STANDARD
01-januar-2025
Tekočine za elektrotehniko - Neuporabljeni naravni estri za transformatorje in
podobno električno opremo
Fluids for electrotechnical applications - Unused natural esters for transformers and
similar electrical equipment
Flüssigkeiten für elektrotechnische Anwendungen - Neue natürliche Ester für
Transformatoren und ähnliche elektrische Betriebsmittel
Fluides pour applications électrotechniques - Esters naturels neufs pour transformateurs
et matériels électriques analogues
Ta slovenski standard je istoveten z: EN IEC 62770:2024
ICS:
29.040.01 Izolacijski fluidi na splošno Insulating fluids in general
29.180 Transformatorji. Dušilke Transformers. Reactors
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 62770

NORME EUROPÉENNE
EUROPÄISCHE NORM November 2024
ICS 29.040.01 Supersedes EN 62770:2014
English Version
Fluids for electrotechnical applications - Unused natural esters
for transformers and similar electrical equipment
(IEC 62770:2024)
Fluides pour applications électrotechniques - Esters Flüssigkeiten für elektrotechnische Anwendungen - Neue
naturels neufs pour transformateurs et matériels électriques natürliche Ester für Transformatoren und ähnliche
analogues elektrische Betriebsmittel
(IEC 62770:2024) (IEC 62770:2024)
This European Standard was approved by CENELEC on 2024-11-12. 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 CEN-CENELEC
Management Centre 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 CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 62770:2024 E
European foreword
The text of document 10/1215/FDIS, future edition 2 of IEC 62770, prepared by TC 10 "Fluids for
electrotechnical applications" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN IEC 62770:2024.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2025-11-30
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2027-11-30
document have to be withdrawn
This document supersedes EN 62770:2014 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 62770:2024 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 standard indicated:
IEC 60076-14 NOTE Approved as EN 60076-14
IEC 60296 NOTE Approved as EN IEC 60296
IEC 60422 NOTE Approved as EN IEC 60422
IEC 61039 NOTE Approved as EN 61039
IEC 61099 NOTE Approved as EN 61099
IEC 61868 NOTE Approved as EN 61868
IEC 63012 NOTE Approved as EN IEC 63012
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1 Where an International Publication has been modified by common modifications, indicated by (mod), the
relevant EN/HD applies.
NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60156 - Insulating liquids - Determination of the EN IEC 60156 -
breakdown voltage at power frequency -
Test method
IEC 60247 - Insulating liquids - Measurement of relative EN 60247 -
permittivity, dielectric dissipation factor (tan
d) and d.c. resistivity
IEC 60475 - Method of sampling insulating liquids EN IEC 60475 -
IEC 60666 - Detection and determination of specified EN 60666 -
additives in mineral insulating oils
IEC 60814 - Insulating liquids - Oil-impregnated paper EN 60814 -
and pressboard - Determination of water
by automatic coulometric Karl Fischer
titration
IEC 61125 - Insulating liquids - Test methods for EN IEC 61125 -
oxidation stability - Test method for
evaluating the oxidation stability of
insulating liquids in the delivered state
IEC 61198 - Mineral insulating oils - Methods for the EN 61198 -
determination of 2-furfural and related
compounds
IEC 61619 - Insulating liquids - Contamination by EN 61619 -
polychlorinated biphenyls (PCBs) - Method
of determination by capillary column gas
chromatography
IEC 61620 - Insulating liquids - Determination of the EN 61620 -
dielectric dissipation factor by
measurement of the conductance and
capacitance - Test method
IEC 62021-3 - Insulating liquids - Determination of acidity EN 62021-3 -
- Part 3: Test methods for non-mineral
insulating oils
IEC 62535 - Insulating liquids - Test method for EN 62535 -
detection of potentially corrosive sulphur in
used and unused insulating oil
IEC 62697-1 - Test methods for quantitative EN 62697-1 -
determination of corrosive sulfur
compounds in unused and used insulating
liquids - Part 1: Test method for
quantitative determination of
dibenzyldisulfide (DBDS)
ISO 2049 - Petroleum products - Determination of - -
colour (ASTM scale)
ISO 2592 - Petroleum and related products - EN ISO 2592 -
Determination of flash and fire points -
Cleveland open cup method
ISO 3016 - Petroleum and related products from EN ISO 3016 -
natural or synthetic sources -
Determination of pour point
ISO 3104 - Petroleum products - Transparent and EN ISO 3104 -
opaque fluids - Determination of kinematic
viscosity and calculation of dynamic
viscosity
ISO 3675 - Crude petroleum and liquid petroleum EN ISO 3675 -
products - Laboratory determination of
density - Hydrometer method
ISO 12185 - Crude petroleum and petroleum products - EN ISO 12185 -
Determination of density - Oscillating U-
tube method
ASTM D1500 - Standard Test Method for ASTM Color of - -
Petroleum Products (ASTM Colour Scale)
ASTM D7042 - Standard Test Method for Dynamic - -
Viscosity and Density of Liquids by
Stabinger Viscometer (and the Calculation
of Kinematic Viscosity)
IEC 62770 ®
Edition 2.0 2024-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fluids for electrotechnical applications – Unused natural esters for

transformers and similar electrical equipment

Fluides pour applications électrotechniques – Esters naturels neufs pour

transformateurs et matériels électriques analogues

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.040.01  ISBN 978-2-8322-9528-1

– 2 – IEC 62770:2024 © IEC 2024
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and abbreviated terms . 8
3.1 Terms and definitions . 8
3.2 Abbreviated terms . 9
4 Properties, their significance and test methods . 9
4.1 General . 9
4.2 Physical properties . 9
4.2.1 Appearance and colour . 9
4.2.2 Viscosity . 10
4.2.3 Pour point . 10
4.2.4 Water content . 10
4.2.5 Density . 10
4.3 Electrical properties . 11
4.3.1 Breakdown voltage . 11
4.3.2 Dielectric dissipation factor (DDF) . 11
4.3.3 Relative permittivity (dielectric constant) . 11
4.4 Chemical properties . 11
4.4.1 Acidity . 11
4.4.2 Corrosive sulfur . 11
4.4.3 Additive content . 11
4.4.4 Furfural content . 12
4.5 Performance . 12
4.5.1 General . 12
4.5.2 Oxidation stability . 12
4.6 Health, safety and environmental (HSE) properties . 12
4.6.1 Fire point and flash point . 12
4.6.2 Polychlorinated biphenyls (PCBs) . 12
4.6.3 Biodegradation . 13
4.6.4 Aquatic toxicity . 13
5 Classification, identification, general delivery requirements, and sampling . 13
5.1 Classification . 13
5.2 Identification and general delivery requirements . 13
5.3 Sampling. 13
Annex A (normative) Summary of the test method for evaluating oxidation stability
of unused natural esters . 15
A.1 General . 15
A.2 Test conditions . 15
A.3 Precision . 15
A.4 Relative repeatability (r) . 15
A.5 Relative reproducibility (R) . 15
Bibliography . 16

IEC 62770:2024 © IEC 2024 – 3 –
Table 1 – Abbreviated terms . 9
Table 2 – General specifications . 14
Table A.1 – Relative repeatability and relative reproducibility obtained for different
parameters during RRT . 15

– 4 – IEC 62770:2024 © 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.
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:
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.

IEC 62770:2024 © IEC 2024 – 5 –
d) Pour point: Introduction of the importance of LCSET with advice on cold temperature
behaviour of natural esters.
e) Additives: new agreed wording inserted on the declaration of additives
f) Flash and fire points: now only determined by Cleveland Open Cup method, since the
Pensky-Martens closed cup method was identified as problematic with natural esters.
g) Toxicity: Aquatic toxicity now emphasized.
h) Annex B removed as it is no longer needed since the publication of IEC 63012.
The text of this International Standard is based on the following documents:
Draft Report on voting
10/1215/FDIS 10/1243/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
– 6 – IEC 62770:2024 © IEC 2024
INTRODUCTION
Because of their higher fire points and lower environmental impact relative to hydrocarbon
petroleum derived insulating mineral oil, the use of vegetable oils and other natural esters is on
the rise as insulating and heat transfer fluids in electrical devices such as transformers.
This document sets performance criteria for unused natural esters earmarked for electrical
applications. However, the use of natural esters is recommended only for equipment that is not
open to the atmosphere, for example sealed transformers and reactors because these liquids
are susceptible to oxidation.
This document does not purport to address all the safety problems associated with its use. It is
the responsibility of the user of the document to establish appropriate health and safety
practices and determine the applicability of regulatory limitations prior to use.
Unused natural esters which are the subject of this document should be handled with due regard
to personal hygiene. Direct contact with eyes should be avoided. In case of eye contact,
irrigation with copious amounts of clean running water should be carried out and medical advice
sought.
Performance of some of the tests mentioned in this document could lead to a hazardous
situation. Attention is drawn to the relevant document test method for guidance.

IEC 62770:2024 © IEC 2024 – 7 –
FLUIDS FOR ELECTROTECHNICAL APPLICATIONS –
UNUSED NATURAL ESTERS FOR TRANSFORMERS
AND SIMILAR ELECTRICAL EQUIPMENT

1 Scope
This document describes specifications and test methods for unused natural esters in
transformers and similar liquid-immersed electrical equipment in which a liquid is required as
an insulating and heat transfer medium. The exposure of natural ester to air leads to
deterioration of the insulating liquid. Use of natural esters is therefore restricted to sealed units,
or with the conservator tank protected from the contact with atmosphere by a membrane or
other suitable system.
In this document the term "natural esters" applies to insulating liquids for transformers and
similar electrical equipment with suitable biodegradability and lower environmental impact.
Such natural esters are vegetable oils obtained from seeds, and oils obtained from other
su
...