IEC TS 60076-14:2009

IEC/TS 60076-14 ®
Edition 2.0 2009-05
TECHNICAL
SPECIFICATION
Power transformers –
Part 14: Design and application of liquid-immersed power transformers using
high-temperature insulation materials

IEC/TS 60076-14:2009(E)
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IEC/TS 60076-14 ®
Edition 2.0 2009-05
TECHNICAL
SPECIFICATION
Power transformers –
Part 14: Design and application of liquid-immersed power transformers using
high-temperature insulation materials

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
X
ICS 29.180 ISBN 978-2-88910-042-2
– 2 – TS 60076-14 © IEC:2009(E)
CONTENTS
FOREWORD.5
INTRODUCTION.7
1 Scope.9
2 Normative references .9
3 Terms and definitions .10
4 Insulation materials .12
4.1 General .12
4.2 Ageing and lifetime of insulation materials.12
4.3 Solid insulation.15
4.4 Wire enamel insulation .17
4.5 Insulating liquids .17
5 Insulation systems.20
5.1 General .20
5.2 Insulation system types .20
5.2.1 Homogeneous high-temperature insulation system .20
5.2.2 Hybrid insulation system.20
5.2.3 Semi-hybrid insulation system .22
5.2.4 Mixed insulation system.23
6 Temperature limits.24
7 Transformer accessories and compatibility .26
7.1 General .26
7.2 Bushings .27
7.3 Tap-changer.27
7.4 Gasket material .27
7.5 Tank painting .27
7.6 Coolers .28
7.7 Pumps.28
7.8 Tank and conservator.28
7.9 Adhesives .28
7.10 Current transformers .28
7.11 Temperature gauges and indicators.28
7.12 Protective relays .28
7.13 Auxiliary cables .28
8 Special design considerations .29
8.1 Short-circuit considerations .29
8.2 Dielectric requirements.29
8.3 Temperature requirements .29
8.4 Overload .30
8.5 Effects of harmonic currents.31
8.6 Liquid preservation system.31
9 Required information .31
9.1 Information to be provided by the purchaser.31
9.1.1 Ambient temperatures and loading cycle .31
9.1.2 Harmonic currents .31
9.1.3 Other unusual service conditions .31

TS 60076-14 © IEC:2009(E) – 3 –
9.2 Information to be provided by the manufacturer.32
9.2.1 Thermal characteristics .32
9.2.2 Reference temperature.32
9.2.3 Guarantees .32
10 Rating plate and additional information.32
10.1 Rating and warning plates .32
10.1.1 Rating plate.32
10.1.2 Warning plate .32
10.2 Transformer manual .32
11 Testing .33
11.1 General .33
11.2 Requirements for routine, type and special tests .33
11.2.1 General .33
11.2.2 Routine tests .33
11.2.3 Type tests .33
11.2.4 Special tests.33
11.3 Temperature-rise test .33
11.3.1 General .33
11.3.2 Evaluation of temperature-rise tests for mixed insulation systems .33
11.4 Dielectric type tests.36
12 Supervision, diagnostics, and maintenance .36
12.1 General .36
12.2 Transformers filled with mineral insulating oil .36
12.3 Transformers filled with high-temperature insulating liquids.36
Annex A (informative) Calculation of bubble generation temperature .37
Annex B (informative) A perspective of transformer temperatures from Tables 4 and 5 .42
Bibliography.43

Figure 1 – Example of a thermal endurance graph .14
Figure 2 – Illustration of solid insulation in a hybrid insulation system .21
Figure 3 – Illustration of solid insulation in a semi-hybrid insulation system .22
Figure 4 – Illustration of solid insulation in a mixed insulation system .23
Figure 5 – Temperature gradient conductor to liquid .30
Figure 6 – Modified temperature diagram for windings with mixed insulation system.35
Figure A.1 – Bubble evolution temperature chart.38
Figure A.2 – Moisture equilibrium curves for cellulose and mineral oil.39
Figure A.3 – Logarithmic moisture equilibrium curves for cellulose and mineral oil.40
Figure A.4 – Water content of paper versus bubble evolution temperature for
parameters taken from the example .41

Table 1 – Typical properties of solid insulation materials .16
Table 2 – Typical enamels for wire insulation.17
Table 3 – Typical performance characteristics of unused insulating liquids .19
Table 4 – Temperature limits for transformers with mineral oil or alternative liquid
operated at 60 K top liquid temperature rise.25
Table 5 – Temperature limits for transformers with homogeneous high-temperature
insulation systems .26

– 4 – TS 60076-14 © IEC:2009(E)
Table B.1 – Comparison of theoretically possible transformer temperature rises .42

TS 60076-14 © IEC:2009(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER TRANSFORMERS –
Part 14: Design and application of liquid-immersed power
transformers using high-temperature insulation materials

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.
The main task of IEC technical committees is to prepare International Standards. In
exceptional circumstances, a technical committee may propose the publication of a technical
specification when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC 60076-14, which is a technical specification, has been prepared by IEC technical
committee 14: Power transformers.

– 6 – TS 60076-14 © IEC:2009(E)
This second edition cancels and replaces the first edition published in 2004. It is a technical
revision.
This edition includes the following significant technical changes with respect to the previous
edition:
• additional clarification added to the introduction;
• addition of an introduction to the ageing and lifetime of insulation materials;
• enhancement of insulation system descriptions;
• clarification of temperature rise limits and the addition of overload temperature limits.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
14/591A/DTS 14/600/RVC
Full information on the voting for the approval of this technical specification 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.
A list of all parts of the IEC 60076 series can be found, under the general title Power
transformers, on the IEC website.
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
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

TS 60076-14 © IEC:2009(E) – 7 –
INTRODUCTION
The average temperature rise in liquid-immersed transformer windings has for several tens of
years been limited to 65/70 K and the top oil temperature rise to 60 K, as specified in
IEC 60076-2.
Winding conductors in these transformers have historically been insulated with cellulosic
paper or enamel. Other solid insulation materials have also been cellulose-based products.
The insulation liquid has, for the most part been mineral insulating oil. These materials are
still dominant.
Consequently, most of the accumulated experience of transformers in service is based on
these insulation materials and these temperature limits. In some cases, space or weight
limitations require the designer to reduce the transformer dimensions with higher temperature
rises as a consequence. The application of insulation materials (both solid and liquid) with
better ageing properties at elevated temperatures than the traditional ones is necessary in
order to provide an acceptable life expectancy. High-temperature solid insulation materials
have also occasionally been used only in certain parts of the windings where high
temperature has been expected.
Recent temperature measurements by means of fibre-optics have indicated that the hot-spot
temperature may sometimes be higher than predicted, and in certain cases considerably
higher. This has created concern regarding higher rate of ageing than expected. The
measurements have provided knowledge regarding where the hot-spots are situated and
where high-temperature materials might be applied.
High-temperature insulation, from enamel and tape wrap for conductors, to spacer and
mechanical support materials are already used in power, distribution, mobile, locomotive and
rectifier transformers. Class K liquids, with a fire point greater than 300 °C are suitable for
temperatures higher than mineral insulating oil and have been used for decades. Their use
and range of application is increasing rapidly. For many years, manufacturers have met the
needs of special applications by designing transformers using high-temperature materials to
achieve lower weight, higher power density, improved fire safety or increased life.
The purpose of this technical specification is to begin the process of standardizing the
development of liquid-immersed transformers that use high-temperature insulation. As a
system, the solid insulation may encompass a broad range of materials with varying degrees
of thermal capability. The insulating and cooling liquids also vary substantially from mineral oil
to any of a number of new class K liquids that also have a broad range of thermal capability.
The liquid and solid insulation materials found in any standard type of modern liquid-
immersed transformer compose an insulation system that has evolved and developed over
more than 100 years. Accordingly, the rules and guidelines for application are also robust and
rather well developed. In contrast, high-temperature insulation materials and applications for
transformers that use these materials are relatively new in both development and application.
It should not therefore be surprising that much of the information is neither well developed nor
completely understood. However, it is important to establish and maintain a document that
provides a starting point for discussion between the manufacturer and the user. It is expected
that this technical specification would be updated regularly as development progresses.
This document is not intended to stand alone, but rather builds on the wealth of information
and guidelines documented in the other parts of the IEC 60076 series. Accordingly, this
document follows two guiding principles. The first principle is that liquid-immersed
transformers are well known and are well defined in other parts of this series and therefore,
the details of these transformers are not repeated in this technical specification, except where
reference has value, or where repetition is considered appropriate for purposes of emphasis
or comparison.
– 8 – TS 60076-14 © IEC:2009(E)
The second principle is that the usual liquid-immersed transformer, insulated with kraft paper,
pressboard, wood, mineral oil and many other commonly used materials operating at
established temperature limits, are well known and considered normal or conventional. All
other insulation materials, either solid or liquid that have a thermal capability higher than the
materials used in this well known system of insulation materials are considered high-
temperature.
Consequently, this “standard” or “normal” insulation system is defined as the “conventional”
insulation system for comparison purposes and these normal thermal limits are presented for
reference to illustrate the differences between other higher-temperature systems. Commonly
used solid and liquid insulations are also tabulated in a general way to allow easy comparison
of typical properties and to demonstrate the added range and capabilities of relatively
unfamiliar materials.
This technical specification addresses loading, overloading, testing and accessories in the
same manner. Only selected information for the “conventional” transformers is included for
comparison purposes or for emphasis. All other references are directed to the appropriate IEC
document.
TS 60076-14 © IEC:2009(E) – 9 –
POWER TRANSFORMERS –
Part 14: Design and application of liquid-immersed power
transformers using high-temperature insulation materials

1 Scope
This part of IEC 60076 provides specification, design, testing and loading information for use
by both the manufacturer and user of liquid-immersed power transformers employing either
high-temperature insulation or combinations of high-temperature and conventional insulation.
It is applicable to:
– power transformers designed in accordance with IEC 60076-1,
– convertor transformers designed to IEC 61378 series,
– arc furnace transformers,
and covers the use of various liquid and solid insulation combinations.
Whilst standards for traction transformers fall under the authority of IEC technical
committee 9, this part of IEC 60076, however, may be applicable as a guideline for the use of
high-temperature insulation materials in traction transformers.
2 Normative references
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.
IEC 60076-1:1993, Power transformers – Part 1: General
IEC 60076-2, Power transformers – Part 2: Temperature rise
IEC 60076-3, Power transformers – Part 3: Insulation levels, dielectric tests and external
clearances in air
IEC 60076-5, Power transformers – Part 5: Ability to withstand short-circuit
IEC 60076-7:2005, Power transformers – Part 7: Loading guide for oil-immersed power
transformers
IEC 60085, Electrical insulation – Thermal evaluation and designation
IEC 60216-1, Electrical insulating materials – Properties of thermal endurance – Part 1:
Ageing procedures and evaluation of test results
IEC 60296, Fluids for electrotechnical applications – Unused mineral insulating oils for
transformers and switchgear
IEC 60317 (all parts), Specifications for particular types of winding wires

– 10 – TS 60076-14 © IEC:2009(E)
IEC 60554-3 (all parts), Specification for cellulosic papers for electrical purposes – Part 3:
Specifications for individual materials
IEC 60641-3 (all parts), Pressboard and presspaper for electrical purposes – Part 3:
Specifications for individual materials
IEC 60674-3 (all parts), Plastic films for electrical purposes – Part 3: Specifications for
individual materials
IEC 60819-3 (all parts), Non-cellulosic papers for electrical purposes – Part 3: Specifications
for individual materials
IEC 60836, Specifications for unused silicone insulating liquids for electrotechnical purposes
IEC 60851-4, Winding wires – Test methods – Part 4: Chemical properties
IEC 60867, Insulating liquids – Specifications for unused liquids based on synthetic aromatic
hydrocarbons
IEC 60893-3 (all parts), Insulating materials – Industrial rigid laminated sheets based on
thermosetting resins for electrical purposes – Part 3: Specifications for individual materials
IEC 61099, Specifications for unused synthetic organic esters for electrical purposes
IEC 61100, Classification of insulating liquids according to fire-point and net calorific value
IEC 61212-3 (all parts), Insulating materials – Industrial rigid round laminated tubes and rods
based on thermosetting resins for electrical purposes – Part 3: Specifications for individual
materials
IEC 61378-1, Convertor transformers – Part 1: Transformers for industrial applications
IEC 61629-1, Aramid pressboard for electrical purposes – Part 1: Definitions, designations
and general requirements
ISO 2592, Determination of flash and fire points – Cleveland open cup method
ISO 2719, Determination of flash-point – Pensky-Martens closed cup method
3 Terms and definitions
For the purposes of this document, the following terms and definitions, as well as those of
IEC 60076-1 and IEC 60076-2 apply.
3.1
insulation system
a system composed of solid insulating materials and an insulating liquid
3.2
temperature index TI
numerical value of the temperature in degrees Celsius derived from the thermal endurance
relationship at a time of 20 000 hours (or other specified time)
[IEV 212-02-08, modified]
TS 60076-14 © IEC:2009(E) – 11 –
3.3
halving interval HIC
numerical value of the temperature interval in degrees Celsius which expresses the halving of
the time to end-point taken at the temperature equal to TI
[IEV 212-02-10, modified]
3.4
thermal class
designation of Electrical Insulation Materials (EIM) or Electrical Insulation Systems (EIS)
equal to the numerical value of the maximum used temperature in degrees Celsius for which
the EIM/EIS is appropriate
[IEC 60085, 3.11, modified]
3.5
conventional
adjective that refers to temperature rise limits and insulation materials applied in systems
consisting of mineral oil and non-thermally upgraded paper
3.6
thermally upgraded paper (TUP)
cellulose-based paper which has been chemically modified to reduce the rate at which the
paper decomposes. Ageing effects are reduced either by partial elimination of water forming
agents (as in cyanoethylation) or by inhibiting the formation of water through the use of
stabilizing agents (as in amine addition, dicyandiamide). A paper is considered as thermally
upgraded if it meets the life criteria defined in ANSI/IEEE C57.100; 50 % retention in tensile
strength after 65 000 hours in a sealed tube at 110 °C or any other time/temperature
combination given by the equation:
⎛ 15 000 ⎞ ⎛ 15 000 15 000 ⎞
⎜ ⎟ ⎜ ⎟
− 28,082 −
(1)
⎜ ⎟ ⎜ ⎟
( θ + 273 ) ( θ + 273 )() 110 + 273
⎝ h ⎠ ⎝ h ⎠
Time (h) = e ≈ 65 000 × e
Because the thermal upgrading chemicals used today contain nitrogen, which is not present in
Kraft pulp, the degree of chemical modification is determined by testing for the amount of
nitrogen present in the treated paper. Typical values for nitrogen content of thermally
upgraded papers are between 1 % and 4 % when measured in accordance with
ASTM D-982.
NOTE This definition was approved by the IEEE Transformers Committee Task Force for the Definition of
Thermally Upgraded Paper on 7 October 2003.
[IEC 60076-7, 3.12]
3.7
high-temperature
refers to temperature rise limits and insulation materials applied in systems consisting of solid
materials and/or liquid operating at higher temperatures than conventional
3.8
hybrid insulation system
high-temperature solid insulation material adjacent to all winding conductors either bare or
insulated (including all conductor insulation, spacers, strips and cylinders in direct contact
with the winding conductor) and cellulose-based materials in lower temperature areas where
thermal class 105 limits are met (see Figure 2)
3.9
semi-hybrid insulation system
high-temperature materials used only for conductor insulation (see Figure 3)

– 12 – TS 60076-14 © IEC:2009(E)
3.10
mixed insulation system
high-temperature solid insulation material adjacent to the winding conductors located in the
hotter regions (including all conductor insulation and, if necessary, spacers, strips and
cylinders in contact with these conductors) and cellulose-based materials in the rest of the
winding and other lower temperature areas where thermal class 105 limits are met (see
Figure 4)
3.11
homogeneous insulation system
high-temperature insulation used in all areas exposed to temperatures higher than would be
suitable for conventional insulation systems together with high-temperature insulating liquid
3.12
reference temperature
20 °C + rated mean winding temperature rise
4 Insulation materials
4.1 General
This clause lists many high-temperature Electrical Insulation Materials (EIM) for informational
purposes only. The appearance of these materials does not imply that any specific
combination is suitable for use in high-temperature liquid-immersed transformer applications,
as an Electrical Insulation System (EIS).
Common solid materials currently available are listed in Table 1 along with typical parameters
and characteristics, which are necessary for proper evaluation. It is important to note that
design parameters specific to the material selected should be obtained from the manufacturer
of the product. The insulation materials may be conveniently separated into solids, wire
enamels and liquids.
Each material should be evaluated for compatibility with other materials in the system and not
only for thermal capability. It should also be noted that whilst the thermal capability of the
individual materials may be satisfactory, the interaction of these individual elements in the
system might render the system unacceptable.
4.2 Ageing and lifetime of insulation materials
Material ageing is the result of a process that splits the molecules of the insulation material
and consequently changes some material properties. This is an endothermic process, which
means that sufficient energy must be supplied to enable the atoms to split the molecules. In
transformers, this energy is provided mainly by the transformer losses. The more energy
supplied, the faster the splitting rate. The energy takes the form of heat, which increases the
temperature. The temperature is then a relevant indicator of the ageing rate and the lifetime.
Other factors than the temperature, such as the presence of acids, oxygen and/or water may
influence the lifetime. Assuming that these other factors are constant, the lifetime of insulation
material normally follows the equation:
b
T
L = a × e (2)
___________
This sublcause presents the classic theory of ageing for a simple material. More detailed analyses of the
complex mechanisms of material ageing in a typical transformer may be found in the technical papers listed in
the Bibliography.
TS 60076-14 © IEC:2009(E) – 13 –
where
L is the lifetime in hours;
a is a constant with the dimension hour;
e is the base of the natural logarithm (2,718…);
b is a constant with the dimension Kelvin;
T is the temperature in Kelvin.
Equation (2) is derived from Arrhenius’ equation. When taking the natural logarithm on both
sides of Equation (2), the result is:
b
ln( L) = ln( a) + (3)
T
Equation (3) is represented by a straight line (in semi logarithmic coordinates of L versus 1/T),
which is determined by means of a thermal endurance test described in IEC 60216-1.
End of life criterion must be defined prior to the thermal endurance test. It may be an absolute
value or a percentage of the original value of a material property that is crucial for the
insulating function of the material, and preferably a property that deteriorates faster than other
vital properties of the material. For mineral oil-immersed transformers with cellulose-based
insulation, the tensile strength of the paper that covers the winding conductors is often used
as one of the parameters that determine the degree of ageing of the whole transformer. The
degree of polymerization (DP) is also used as an ageing indicator, with a value of 200
generally considered to be end of life for cellulose-based insulation.
During the thermal endurance test, samples of the material are heated to several different
temperatures and the time to end of life is noted. The time durations versus the reciprocal
value of the absolute temperatures are plotted in a coordinate system, where the time axis
has a logarithmic scale (see Figure 1).
The dots in the diagram are the results from a thermal endurance test. The straight line is the
regression line. As will be seen, the dots are situated closely to the regression line, which
confirms that the lifetime versus temperature relationship for the tested material follows
Arrhenius’ equation.
– 14 – TS 60076-14 © IEC:2009(E)

Y
1000 000
–23-23 25325 390/T90 T 0
/
y = 6x10 xe
y = 6 × 10 × e
R = 0,983 5
100 000
R = 0,9835
10 000
TI = 143 ºC
1 000
HIC = 5 ºC
100 X
0,002 55 0,002 5 0,002 45 0,002 4 0,002 35 0,002 3 0,002 25 0,002 2
1/T  (1/K)
IEC  678/09
Key
–1
X axis: Reciprocal value of the absolute temperature in K
Y axis: Lifetime in h (hours)
NOTE The X axis (1/T) is normally represented right-to-left, so that higher temperatures are at the right hand side
of the graph.
Figure 1 – Example of a thermal endurance graph
A vertical line is drawn at the point where the extended regression line crosses the 20 000 h
ordinate, and this vertical line hits the abscissa axis at a point corresponding to a temperature
of 143 ºC. This means that the temperature index TI of this material is 143 ºC.
Another vertical line is drawn from the point where the regression line crosses the 10 000 h
ordinate, and this vertical line hits the abscissa axis at a point corresponding to 148 ºC. The
halving interval HIC is then the difference between 148 and 143, which equals 5 ºC.
A lifetime of 20 000 h (somewhat more than 2 years) at the temperature index TI would
normally be too short as an acceptable lifetime. To obtain an acceptable lifetime the thermal
class assigned to the material must be chosen lower than TI. How much lower depends on
how long a lifetime the user of the material requires. The relation between lifetime and
temperature can be read from the extended regression line in the diagram or calculated by
means of the regression line equation at the upper right corner of the diagram.
If for example 20 years (175 200 h) lifetime is required, the thermal class should be 128 ºC. If
30 years (262 800 h) lifetime is required, the thermal class should be 126 ºC.
The thermal class is equal to the maximum service temperature that the user of the material
finds appropriate, taking into account the required lifetime of the transformer where the
material is going to be used. The loading pattern of the transformer and the real ambient
temperatures at the site where the transformer will be situated should also be considered. The
transformer may in many cases be loaded below its rated loading for long periods, which
would reduce the ageing rate and extend the lifetime.

TS 60076-14 © IEC:2009(E) – 15 –
In some performed tests, the end of life has been defined to have occurred when 50 % of the
initial tensile strength is consumed. However, this limit, or any other defined limit for end of
life, should not be perceived too literally. A transformer may operate satisfactorily for many
years after the end of life according to this definition is reached. The decomposition of the
material happens gradually. There are no sharp limits. This defined end of life serves more as
a warning that the ability of the transformer to withstand stresses under abnormal service
conditions, like high short-circuit currents is essentially lower compared to a new transformer.
Also transport of the transformer from one site to another involves a higher risk.
4.3 Solid insulation
Solid insulation is available in the form of paper, film, sheet and board as well as various
shapes for mechanical applications used within the dielectric structure. Table 1 lists many
readily available materials, along with typical parameters. The table also includes cellulose-
based products for comparison purposes. Note that this typical performance information is
based on components tested individually as isolated samples in air. Dielectric and thermal
performance as a system, when immersed in the selected insulating liquid may be
substantially different from the component values and the values associated with
impregnation in a specific liquid.
It should also not be assumed that the system thermal class would necessarily default to the
lowest temperature class of the system’s individual components. On the contrary, the thermal
capability will often favour the highest temperature component. However, the individual
component thermal class should provide guidance in the selection and positioning of the
various materials within the insulation design.
Based on the interpretation of test data during the development of alternative fluids, it has
been proposed that liquids with significantly higher water saturation levels at operating
temperatures may allow higher operating temperature limits for the solid insulation because of
their ability to remove the moisture from the paper.

– 16 –            TS 60076-14 © IEC:2009(E)

Table 1 – Typical properties of solid insulation materials
Material Thermal IEC Relative Dissipation factor Moisture Density Form
class standard permittivity (%) absorption (g/cm )
(IEC 60085) reference at 25 °C (%)
(°C)
At 25 °C At 100 °C
Cellulose-based 105 60554-3 3,3 – 4,1 0,4 1,0 7,0 0,97 – 1,2 Paper
Cellulose-based 120 3,3 – 4,1 0,4 1,0 7,0 0,97 – 1,2 Paper
Thermally
upgraded
Cellulose-based 105 60641-3 2,9 – 4,6 0,4 1,0 7,0 0,8 – 1,35 Board
Stratified resin 130 5,8 2,5 2,3 1,36 Board
bonded paper
(bakelite)
Polyphenylene 155 3,0 0,06 0,12 0,05 1,35 Film
sulfide (PPS)
a
Polyester glass 130 – 200 60893-3 4,8 1,3 – 7,0 N/A 0,2 – 1,1 1,8 – 2,0 Sheet
a
Polyester glass 130 – 220 61212-3 N/A N/A N/A 0,16 – 0,28 1,8 – 2,0 Shapes
Polyimide 220 60674-3 3,4 0,2 0,2 1,0 – 1,8 1,33 – 1,42 Film
Aramid 220 60819-3 1,6 – 3,2 0,5 0,5 5,0 0,72 – 1,10 Paper
Aramid 220 61629-1 2,6 – 3,5 0,5 0,5 5,0 0,70 – 1,15 Board
NOTE 1 All data has been taken from measurements in air.
NOTE 2 Relative permittivity and dissipation factor data are referenced to 50/60 Hz.
NOTE 3 Moisture data is based on air having a relative humidity of 50 %.
a
Typically only used in lower voltage applications due to possible air entrapment during the manufacturing process.

TS 60076-14 © IEC:2009(E) – 17 –
4.4 Wire enamel insulation
The list in Table 2 shows a broad range of available insulating enamels used to coat both
round and rectangular copper and aluminium winding wires. Additional information may be
found in the specific applicable sections of the IEC 60317 series. Note that the appearance of
a coating in this list does not imply compatibility with any of the many available dielectric
liquids. Procedures for verifying compatibility with different liquids are defined in IEC 60851-4.
Table 2 – Typical enamels for wire insulation
Chemical name Thermal IEC 60317 Common Common name
class applicable acronym
part
Polyvinyl acetal 105 1, 14, 17 PVF or PVA Polyvinyl formal
120 12, 18
Polyurethane 130 2, 4 UEW Polyurethane
155 20, 35
180 51
Polyurethane with 130 19 UEWN Nylon over polyurethane
polyamide overcoat 155 21
Polyester 130 34, 41, 45 PEW Polyester
155 3, 16, 54
Polyester with 180 22, 24 PEWN Nylon over polyester
polyamide overcoat HPEWN
Polyesterimide 180 8, 15, 23, 28, EIW Polyesterimide
36, 37
Polyester 200 13, 25, 29, 38 HPEAIW Polyester polyamideimide
polyamideimide
Polyesterimide with 200 13, 25, 29, 38 EAIW Amide-imide over
polyam
...