IEC TS 60076-14:2009
(Main)Power transformers - Part 14: Design and application of liquid-immersed power transformers using high-temperature insulation materials
Power transformers - Part 14: Design and application of liquid-immersed power transformers using high-temperature insulation materials
IEC 60076-14:2009(E) 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. 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. This new edition includes the following significant technical changes with respect to the previous edition:
- enhancement of insulation system descriptions;
- clarification of temperature rise limits
- and the addition of overload temperature limits.
General Information
Relations
Standards Content (Sample)
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)
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
Copyright © 2009 IEC, Geneva, Switzerland
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.
Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de la CEI ou du Comité national de la CEI du pays du demandeur.
Si vous avez des questions sur le copyright de la CEI ou si vous désirez obtenir des droits supplémentaires sur cette
publication, utilisez les coordonnées ci-après ou contactez le Comité national de la CEI de votre pays de résidence.
IEC Central Office
3, rue de Varembé
CH-1211 Geneva 20
Switzerland
Email: inmail@iec.ch
Web: www.iec.ch
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 corrigenda or an amendment might have been published.
ƒ Catalogue of IEC publications: www.iec.ch/searchpub
The IEC on-line Catalogue enables you to search by a variety of criteria (reference number, text, technical committee,…).
It also gives information on projects, withdrawn and replaced publications.
ƒ IEC Just Published: www.iec.ch/online_news/justpub
Stay up to date on all new IEC publications. Just Published details twice a month all new publications released. Available
on-line and also by email.
ƒ Electropedia: www.electropedia.org
The world's leading online dictionary of electronic and electrical terms containing more than 20 000 terms and definitions
in English and French, with equivalent terms in additional languages. Also known as the International Electrotechnical
Vocabulary online.
ƒ Customer Service Centre: www.iec.ch/webstore/custserv
If you wish to give us your feedback on this publication or need further assistance, please visit the Customer Service
Centre FAQ or contact us:
Email: csc@iec.ch
Tel.: +41 22 919 02 11
Fax: +41 22 919 03 00
---------------------- Page: 2 ----------------------
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
® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 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
---------------------- Page: 4 ----------------------
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
---------------------- Page: 5 ----------------------
– 4 – TS 60076-14 © IEC:2009(E)
Table B.1 – Comparison of theoretically possible transformer temperature rises .42
---------------------- Page: 6 ----------------------
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
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.
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.
---------------------- Page: 7 ----------------------
– 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.
---------------------- Page: 8 ----------------------
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.
---------------------- Page: 9 ----------------------
– 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.
---------------------- Page: 10 ----------------------
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
---------------------- Page: 11 ----------------------
– 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]
---------------------- Page: 12 ----------------------
TS 60076-14 © IEC:2009(E) – 11 –
3
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.