IEC 62770:2013

IEC 62770 ®
Edition 1.0 2013-11
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

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IEC 62770 ®
Edition 1.0 2013-11
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
PRICE CODE
INTERNATIONALE
CODE PRIX Q
ICS 29.040 ISBN 978-2-8322-1191-5

– 2 – 62770  IEC:2013
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 9
4 Properties, their significance and test methods . 9
4.1 General . 9
4.2 Physical properties . 9
4.2.1 Appearance . 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 . 10
4.3.1 Breakdown voltage . 10
4.3.2 Dielectric dissipation factor (DDF) . 10
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 . 11
4.5 Performance . 11
4.5.1 Oxidation stability . 11
4.5.2 Total acidity . 12
4.5.3 Viscosity . 12
4.5.4 Dielectric dissipation factor (DDF) . 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 . 12
4.6.4 Toxicity . 12
5 Classification, identification, general delivery requirements and sampling . 12
5.1 Classification . 12
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 Introductory remark . 15
A.2 Test conditions . 15
A.3 Precision . 15
A.4 Relative repeatability (r) . 15
A.5 Relative reproducibility (R) . 15
Annex B (informative) Specifications of low-viscosity insulating fluids derived from
natural esters . 16
Bibliography . 17

62770  IEC:2013 – 3 –
Table 1 – General specifications . 14
Table A.1 – Relative repeatability and relative reproducibility obtained for different
parameters during RRT . 15
Table B.1 – Specifications for low-viscosity of monoesters derived from natural esters . 16

– 4 – 62770  IEC:2013
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
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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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 62770 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
10/909/FDIS 10/933/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.

62770  IEC:2013 – 5 –
The committee has decided that the contents of this publication will remain unchanged until
the stability 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.
– 6 – 62770  IEC:2013
INTRODUCTION
Because of their higher fire points and better environmental compatibility relative to 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 standard 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, e.g. sealed transformers and reactors because these fluids are
prone to rapid oxidation.
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 limitation prior to use.
Unused natural esters which are the subject of this standard 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 standard could lead to a hazardous
situation. Attention is drawn to the relevant standard test method for guidance.
The disposal of natural esters, chemicals and sample containers mentioned in this standard
should be carried out in accordance with current national legislation with regard to the impact
on the environment. Every precaution should be taken to prevent the release of natural esters
into the environment.
62770  IEC:2013 – 7 –
FLUIDS FOR ELECTROTECHNICAL APPLICATIONS –
UNUSED NATURAL ESTERS FOR TRANSFORMERS
AND SIMILAR ELECTRICAL EQUIPMENT

1 Scope
This International Standard describes specifications and test methods for unused natural
esters in transformers and similar oil-impregnated electrical equipment in which a liquid is
required as an insulating and heat transfer medium.
Use of natural esters is not recommended for electrical equipment that is open to the
atmosphere.
In this standard the term “natural esters” applies to insulating fluids for transformers and
similar electrical equipment with suitable biodegradability and environmental compatibility.
Such natural esters are vegetable oils obtained from seeds and oils obtained from other
suitable biological materials and delivered to an agreed point, at a set time period. These oils
are comprised of triglycerides.
Natural esters with additives are within the scope of this standard. Because of their different
chemical composition, natural esters differ from insulating mineral oils and other insulating
fluids that have high fire points, such as synthetic esters or silicone fluids.
Natural, ester-derived insulating fluids with low viscosity have been introduced but are not
covered by this standard. Pertinent properties of such fluids are given in Annex B.
This standard is applicable only to unused natural esters. Reclaimed natural esters and
natural esters blended with non-natural esters fluids are beyond the scope of this standard.
The chemical nomenclature and scientific notations used in the standard are in accordance
with the IUPAC handbook (Quantities, Units and Symbols in Physical Chemistry).
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60076-14, Power transformers - Part 14: Liquid-immersed power transformers using high-
temperature insulation materials
IEC 60156, Insulating liquids – Determination of the breakdown voltage at power frequency –
Test method
IEC 60247, Insulating liquids – Measurement of relative permittivity, dielectric dissipation
factor and DC resistivity of insulating fluids
IEC 60296, Fluids for electrotechnical applications – Unused mineral insulating oils for
transformers and switchgear
IEC 60475, Method of sampling liquid dielectrics
IEC 60666, Detection and determination of specific additives in mineral insulating oils

– 8 – 62770  IEC:2013
IEC 60814, Insulating liquids – Oil-impregnated paper and pressboard – Determination of
water by automatic coulometric Karl Fischer titration
IEC 61100, Classification of insulating liquids according to fire-point and net calorific value
IEC 61125:1992, Unused hydrocarbon-based insulating fluids – Test methods for evaluating
the oxidation stability
IEC 61198, Mineral insulating oils – Methods for the determination of 2-furfural and related
compounds
IEC 61619, Insulating liquids – Contamination by polychlorinated biphenyls (PCBs) – Method
of determination by capillary column gas chromatography
IEC 61620, Insulating liquids – Determination of the dielectric dissipation factor by
measurement of the conductance and capacitance – Test method
IEC 62021-3, Insulating liquids – Determination of acidity – Part 3: Test methods for non
mineral insulating oils
IEC 62535:2008, Insulating liquids – Test method for detection of potentially corrosive sulfur
in used and unused insulating oils
IEC 62697-1, Test method for quantitative determination of corrosive sulfur compounds in
unused and used insulating liquids – Part 1: Test method for quantitative determination of
dibenzyl disulfide (DBDS)
ISO 2592, Determination of flash and fire point – Cleveland open cup method
ISO 2719, Determination of flash point – Pensky-Martens closed cup method
ISO 3016, Petroleum products – Determination of pour point
ISO 3104, Petroleum products – Transparent and opaque fluids – Determination of kinematic
viscosity and calculation of dynamic viscosity
ISO 3675, Crude petroleum and liquid petroleum products – Laboratory determination of
density – Hydrometer method
ISO 12185, Crude petroleum and petroleum products – Determination of density – Oscillating
U-tube method
ASTM D 1275, Standard Test Method for Corrosive Sulfur in Electrical Insulating Oils
OECD 201-203, Test Guidelines for ecotoxicity
OECD 301, Guideline for testing of chemicals adopted by European Council on July 17th 1992
US EPA, Office of Prevention, Pesticides and Toxic Substances (OPPTS)
835.311, Fate, Transport and Transformation Test Guidelines
—————————
Withdrawn in 2009 and partially replaced by IEC 61039.
To be published.
62770  IEC:2013 – 9 –
3 Terms and definitions
For the purposes of this document, the following definitions apply.
3.1
additives
suitable chemical substances which are deliberately added to natural ester insulating fluids in
order to improve certain characteristics, e.g. pour point, viscosity, foaming, and oxidation
stability
Note 1 to entry: Examples include antioxidants, pour-point depressants, electrostatic charging tendency
depressant, metal passivator or deactivators, antifoam agent, refining process improver, etc.
3.2
corrosive sulfur
free sulfur and corrosive sulfur compounds detected by subjecting metals such as copper to
contact with an insulating liquid under standardized conditions
[SOURCE: IEC 60050-212:2010, definition 212-18-20, modified – inclusion of "metals such
as"]
3.3
natural esters
vegetable oils obtained from seeds and oils obtained from other suitable biological materials
and comprised of triglycerides
3.4
potentially corrosive sulfur
organo-sulfur compounds present in transformer oils that may cause copper sulfide formation
[SOURCE: IEC 62535:2008, definition 3.1 – modified, the NOTE to entry has been omitted]
3.5
unused natural esters
unused natural esters as delivered by the supplier
Note 1 to entry: Such a liquid has not been used in, nor been in contact with electrical equipment or other
equipment not required for its manufacture, storage or transport.
Note 2 to entry: The manufacturer and supplier of unused natural esters will have taken all reasonable
precautions to ensure that the natural esters are not contaminated with polychlorinated biphenyls, polychlorinated
terphenyls or polycyclic aromatics (PCB,PCT, PCAs,) or corrosive sulfur compounds; used, reclaimed, or
dechlorinated oils, or other contaminants.
4 Properties, their significance and test methods
4.1 General
Salient characteristics of unused natural esters are listed in Table 1.
NOTE Additional information on natural esters for transformers and similar electrical equipment is available in
CIGRE brochure 436 and IEEE report C57.147.
4.2 Physical properties
4.2.1 Appearance
A visual inspection of unused natural esters (with light transmitted through approximately
10 cm thickness of natural esters at ambient temperature) indicates the presence of visible
contaminants, free water and suspended matter.

– 10 – 62770  IEC:2013
4.2.2 Viscosity
Viscosity influences heat transfer and therefore affects the increase of temperature in the
transformer and other equipment. The lower the viscosity, the easier the oil circulates leading
to better heat transfer. Viscosities at lower temperatures is a critical factor for cold start of
transformers with ON cooling (absence of circulation can lead to possible overheating at hot
spots). It can have negative impact on the speed of moving parts such as on-load tap changer
mechanism, pumps and regulators. Due consideration should be given to viscosity at the
lowest cold start energizing temperature (LCSET). Viscosity at 40 °C and 100 °C shall be
measured according to ISO 3104.
4.2.3 Pour point
Pour point of unused natural esters is the lowest temperature at which the natural esters will
just flow. Pour point shall be measured in accordance with ISO 3016.
Crystallization behaviour of natural esters depends on time and temperature. Crystals should
not be present in liquid at application temperature; precautions shall be taken if oil
temperature inside the electrical device is lower than 0 °C. Below this temperature thermal
and dielectric behavior of the device with natural esters can be adversely affected. A well-
defined method to measure crystallization behavior is not available at present.
4.2.4 Water content
Water content of natural esters affects their dielectric properties. Water content shall be
measured in accordance with IEC 60814.
NOTE Due to the moderately polar nature of natural esters, water content at which free water will appear and
cause deterioration of electric strength is significantly higher in natural esters than that in mineral insulating oils.
4.2.5 Density
Density of natural esters shall be measured in accordance with ISO 3675 (reference method),
but ISO 12185 is also acceptable.
4.3 Electrical properties
4.3.1 Breakdown voltage
Breakdown voltage of unused natural esters shall be measured in accordance with
IEC 60156.
Because of the difference in properties of natural esters, an initial set-up time is required; it
may range between 15 min and 30 min, when there are no visible bubbles in the liquid before
measurements are made.
4.3.2 Dielectric dissipation factor (DDF)
DDF is a measure for dielectric losses caused by the liquid. High DDF can indicate
contamination of the liquid with moisture, particles or soluble polar contaminants or poor
refining quality. DDF shall be measured in accordance with IEC 60247 or IEC 61620 at 90 °C.
In case of dispute, IEC 60247 at 90 °C should be used.
By agreement between parties, DDF may be measured at temperatures other than 90 °C. In
such cases the measurement temperature should be stated in the report.

62770  IEC:2013 – 11 –
4.3.3 Relative permittivity (dielectric constant)
It is the ratio of the amount of electrical energy stored in the liquid at an applied voltage,
relative to that stored in a vacuum. It shall be measured in accordance with IEC 60247 or
IEC 61620 at 90 °C. In case of dispute, IEC 60247 at 90 °C should be used.
NOTE Typical value 2,8 – 3,3.
4.4 Chemical properties
4.4.1 Acidity
Unused natural esters should be near neutral; acidity shall be measured in accordance with
IEC 62021-3.
NOTE Natural esters may contain very low concentrations of free fatty acids; presence of free fatty acids can
affect acidity of natural esters.
4.4.2 Corrosive sulfur
Free corrosive sulfur and potentially corrosive compounds are detected by contacting copper
with insulating liquid under standardized conditions (IEC 62535 or ASTM D1275B). Known
corrosive sulfur compounds such as dibenzyl disulphide (DBDS) shall not be present above
detection limit (IEC 62697-1).
NOTE Corrosive sulfur compounds are not naturally present in vegetable oils or other natural esters. The tests
can verify that additives are non-corrosive and cross-contamination with potentially corrosive oils has not occurred.
4.4.3 Additive content
Additives include antioxidants, metal deactivators, pour point depressants, etc. Antioxidant
additive slows down the oxidation of esters and, in turn, the formation of gels and acidity. One
such antioxidant is 2, 6-di-tert-butyl-p-cresol (DBPC), also known as BHT, but others are also
used. Detection and measurement of defined anti-oxidant additives shall be in accordance
with IEC 60666 or other suitable methods.Total concentration of additives shall be less than a
weight fraction of 5 %.
The supplier with mutual consent should declare the generic types of all additives, and their
concentrations in the case of antioxidants and passivators. Information on initial type and
concentration of additives is useful for supervision and maintenance guidance during the life
of natural esters in transformers and similar electrical equipment.
4.4.4 Furfural content
Furanic compounds, including 2-Furfural, are degradation products of Kraft insulating paper;
such compounds are not typically present in unused natural esters. 2-Furfural and related
compounds shall be determined in accordance with IEC 61198.
NOTE Certain furanic compounds may be present at trace levels in unused natural esters.
4.5 Performance
NOTE This concerns the properties that are related to the long-term behaviour of natural ester insulating fluids in
service and/or their reaction to high electric stress and temperature. Acceptable operating temperatures for esters
are provided in IEC 60076-14.
4.5.1 Oxidation stability
Unused natural esters are recommended for application only in equipment that is not open to
atmosphere because these fluids are prone to rapid oxidation. Oxidation stability of these
fluids can be assessed with modifications to the procedure as described in Method C of
IEC 61125:1992.
– 12 – 62770  IEC:2013
NOTE The modifications in IEC 61125 for natural esters are given in Annex A.
4.5.2 Total acidity
Acidity of natural esters subjected to oxidation stability test. Acidity should be measured in
accordance with 1.9.4 of IEC 61125:1992.
4.5.3 Viscosity
Viscosity of natural esters subjected to oxidation stability test shall be measured at 40 °C
according to ISO 3104.
4.5.4 Dielectric dissipation factor (DDF)
DDF measurements after oxidation stability test provides a measure for dielectric losses
resulting from the water and soluble polar compounds formed in a dielectric liquid as a result
of oxidation. DDF shall be measured in accordance with IEC 60247 or IEC 61620.
4.6 Health, safety and environmental (HSE) properties
NOTE These are the properties that are related to safe handling of natural esters and minimization of their adverse
impact. Examples can include flash and fire points, polycyclic aromatics (PCAs), and polychlorinated
biphenyls/polychlorinated terphenyls (PCBs/PCTs).
4.6.1 Fire point and flash point
The safe operation of electrical equipment requires an adequately high fire point that is
measured in accordance with ISO 2592. Flash point is measured according to ISO 2719.
4.6.2 Polychlorinated biphenyls (PCBs)
Unused natural esters shall be free from PCBs.
Concentrations of these chemicals can be measured according to IEC 61619; total
-1.
concentration shall be less than 2 mg kg
NOTE PCBs and related compounds can be present in unused natural esters only because of cross-
contamination.
4.6.3 Biodegradation
Natural esters exhibit better environmental compatibility relative to petroleum-derived
insulating mineral oils. Specific tests need to be undertaken to demonstrate ready
biodegradability of these fluids. Tests include OECD 301B, C or F; or US EPA – OPPTS
835.311.
NOTE Natural esters can be classified in accordance with IEC 61039, based on biodegradability observed with
OECD 301:1992.
4.6.4 Toxicity
Unused natural esters are considered non-toxic and suppliers shall supply assays that define
the product as non-toxic.
NOTE Toxicity of natural esters can be assessed with test methods such as a modified Ames test or other
suitable internationally recognized assays such as OECD 201-203; US EPA 600/4.82.068:1983.
5 Classification, identification, general delivery requirements and sampling
5.1 Classification
For the purpose of this standard, natural esters are classified in a single class.

62770  IEC:2013 – 13 –
– less flammable natural esters.
NOTE There are other natural ester derived liquids, which may have a different classification. However, these
liquids are not covered by this standard, an example of such liquids is described in Annex B.
5.2 Identification and general delivery requirements
a) Natural esters are normally delivered in bulk, rail tank cars, tank containers, or packed in
drums or (intermediate bulk containers). These shall be clean and suitable for this purpose
in order to avoid any contamination.
b) Liquid drums and sample containers shall carry at least the following markings:
– supplier’s designation;
– classification;
– liquid net weight.
c) Each natural esters delivery shall be accompanied by a document from the supplier
specifying at least: supplier’s designation, liquid classification and quality certificate. At
the request of the purchaser and by mutual consent, the supplier should declare all
generic types of additives and their concentrations in a datasheet in accordance with the
international and local regulations.
5.3 Sampling
Sampling shall be carried out in accordance with the procedure described in IEC 60475.

– 14 – 62770  IEC:2013
Table 1 – General specifications
Property Test method Limits
Physical
Clear, free from sediment and suspended
Appearance
matter
2 -1
Viscosity at 100 °C ISO 3104 Max. 15 mm ·s
2 -1
Viscosity at 40 °C ISO 3104 Max. 50 mm ·s

Pour point ISO 3016 Max. –10 °C

-1
Water content IEC 60814 Max. 200 mg·kg
-3
Density at 20 °C ISO 3675 or ISO 12185 Max. 1 000 kg·m
Electrical
a
Breakdown voltage IEC 60156 (2,5 mm gap) Min. 35 kV
Dissipation factor (tan δ) 90 °C IEC 60247 Max. 0,05
Chemical
-1
Soluble acidity IEC 62021-3 Max. 0,06 mg KOH g
oil
Corrosive sulfur IEC 62535 or ASTM D1275B Non corrosive
DBDS IEC 62697-1 Below detection limit
IEC 60666 or other suitable
Total additives Max. weight fraction 5 %
methods
b
Performance – Salient properties after oxidation stability test in accordance with Method C of IEC 61125:1992

-1
Total acidity 1.9.4 of IEC 61125:1992 Max. 0,6 mg KOH g
oil
Viscosity at 40 °C ISO 3104 Max. 30 % increase over the initial value
DDF (tan δ) at 90 °C IEC 60247 Max. 0,5
Health, safety and environment (HSE)
Fire point ISO 2592 Min. 300 °C
Flash point ISO 2719 Min. 250 °C
US EPA OECD 301 B, C or F
Biodegradation Readily biodegradable
US EPA OPPTS 835.311
a
At delivery.
b
See Annex A for details of oxidation stability parameters.

62770  IEC:2013 – 15 –
Annex A
(normative)
Summary of the test method for evaluating oxidation stability
of unused natural esters
A.1 Introductory remark
Oxidation stability of natural esters is evaluated under accelerated aging conditions similar to
those described in Method C of IEC 61125:1992.
Aliquots of the natural esters samples are maintained at 120 °C in the presence of a solid
copper catalyst, while a constant volume of air is bubbled through the samples for 48 h. The
resistance to oxidation is estimated by measuring volatile acidity, soluble acidity, sludge
formation, viscosity and DDF. The values obtained for these parameters after accelerated
oxidation are compared against the values obtained prior to accelerated oxidation.
A.2 Test conditions
All test conditions i.e. the amount of natural esters, length and diameter of copper catalyst,
oxidation temperature and oxidant (air) flow rate are the same as described in Method C of
IEC 61125:1992. The only modification is in the duration for accelerated aging, which is set at
48 h.
A.3 Precision
Precision values obtained during the Round Robin test on commercially available natural
esters after 48 h oxidation are given in Table A.1. Relative reproducibility for each parameter
is based on results obtained from 11 participating laboratories. The values reported in Table
A.1 are in general agreement with values reported for mineral insulating oils in IEC 61125.
A.4 Relative repeatability (r)
Duplicate determinations carried out by one laboratory at the 95 % confidence level.
A.5 Relative reproducibility (R)
Duplicate determinations carried out by different laboratories at the 95 % confidence level.
Table A.1 – Relative repeatability and relative reproducibility obtained
for different parameters during RRT
Parameter r R
% %
Viscosity at 40 °C 5 7,5
Total acidity 13 38
Sludge 22 57
DDF (tan δ) at 90 °C – 47
– 16 – 62770  IEC:2013
Annex B
(informative)
Specifications of low-viscosity insulating fluids derived
from natural esters
From a chemical and biochemical point of view, the natural esters (i.e. esters that can be
found in biological materials) comprise many other molecules besides the triglycerides to
which the definition of natural esters in this standard refers.
The triglycerides are the main constituents of vegetable oils (and animal fats) and these fluids
are usually characterized by high fire point and flash point, which categorize them in class K
according to IEC 61100. Compared to mineral oils, they are less flammable but they have also
a higher viscosity and a higher pour point.
NOTE According to IEC 61100, class K fluids have a fire point > 300 °C (according to ISO 2592 – open cup) and a
flash point > 250 °C (according to ISO 2719 – closed cup)
Other insulating fluids, derived from various natural esters, have been developed for use in
some electrotechnical applications (e.g. low/medium voltage power transformers with ONAN
cooling). Such fluids mainly consist of fatty acid mono-esters that allow lowering the viscosity
or mixtures of triglycerides and fatty acid mono-esters.
The properties of the low-viscosity insulating fluids derived from natural esters are close to
those of mineral oils, as shown in Table B.1.

Table B.1 – Specifications for low-viscosity of monoesters derived
from natural esters
Property Test method Limits
Physical
2 -1
Viscosity at 100 °C ISO 3104 Max. 6 mm ·s
2 -1
Viscosity at 40 °C ISO 3104 Max. 18 mm ·s
2 -1
Viscosity at 0 °C ISO 3104 Max. 90 mm ·s

a
Pour point ISO 3016 Max. –25 °C
Electrical
b
Breakdown voltage IEC 60156 (2,5 mm gap) Min. 35 kV
Dissipation factor
IEC 60247 Max. 0,05
(tan δ) at 90 °C
Health, safety and environment (HSE)
Fire point ISO 2592 (open cup) Min. 175 °C
Flash point ISO 2719 (closed cup) Min. 135 °C
US EPA OECD 301 B,C,F
Biodegradation Readily biodegradable
US EPA OPPTS 835.311
a
LCSET Lowest cold start energizing temperature –10 K.
b
At delivery and ≥70 kV after treatment (see IEC 60296 for a description of the laboratory treatment).

62770  IEC:2013 – 17 –
Bibliography
IEC 60050-212:2010, International Electrotechnical Vocabulary – Part 212: Electrical
insulating solids, liquids and gases
IEC 60050-421, International Electrotechnical Vocabulary – Chapter 421: Power transformers
and reactors
IEC 60422, Mineral insulating oils in electrical equipment – Supervision and maintenance
guidance
IEC 61039, Classification of insulating fluids
IEC 61099, Specification for unused synthetic organic esters for electrical purposes
IEC 61868, Mineral insulating oils – Determination of kinematic viscosity at very low
temperatures
ASTM D6871: Standard specification for natural (vegetable oil) ester fluids used in electrical
apparatus
International Union of Pure and Applied Chemistry (IUPAC) Handbook of terms and definitions
CIGRE Brochure 436, Experiences in Service with New Insulating Liquids. Working Group A2.
35, October, 2010
th
IEEE C57.147 , Guide for Acceptance and Maintenance of Natural Ester Fluids in
Transformers
IP 346, Determination of polycyclic aromatics in unused base oils and asphaltene free
petroleum fraction – Dimethyl sulfoxide extraction refractive index method
US EPA 600/4.82.068:1983, Interim Procedure for Conducting the Salmonella/Microsomal
Mutagenicity Assay (Ames Test)

_____________
– 18 – 62770  CEI:2013
SOMMAIRE
AVANT-PROPOS . 20
INTRODUCTION . 22
1 Domaine d’application . 23
2 Références normatives . 23
3 Termes et définitions . 25
4 Propriétés, leur signification et méthodes d’essai. . 26
4.1 Généralités . 26
4.2 Propriétés physiques . 26
4.2.1 Apparence . 26
4.2.2 Viscosité . 26
4.2.3 Point d’écoulement . 26
4.2.4 Teneur en eau . 26
4.2.5 Densité . 26
4.3 Propriétés électriques . 27
4.3.1 Tension de claquage . 27
4.3.2 Facteur de dissipation diélectrique (FDD) . 27
4.3.3 Permittivité relative (constante diélectrique) . 27
4.4 Propriétés chimiques . 27
4.4.1 Acidité . 27
4.4.2 Soufre corrosif . 27
4.4.3 Teneur en additifs . 27
4.4.4 Teneur en furfural . 28
4.5 Performance . 28
4.5.1 Stabilité à l’oxydation . 28
4.5.2 Acidité totale. 28
4.5.3 Viscosité . 28
4.5.4 Facteur de dissipation diélectrique (FDD) .
...