SIST EN 60076-11:2005

SLOVENSKI SIST EN 60076-11:2005

STANDARD
februar 2005
Močnostni transformatorji – 11. del: Suhi transformatorji (IEC 60076-11:2004)
Power transformers - Part 11: Dry-type transformers (IEC 60076-11:2004)
ICS 29.180 Referenčna številka
SIST EN 60076-11:2005(en)
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

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EUROPEAN STANDARD EN 60076-11
NORME EUROPÉENNE
EUROPÄISCHE NORM July 2004

ICS 29.180 Supersedes EN 60726:2003


English version


Power transformers
Part 11: Dry-type transformers
(IEC 60076-11:2004)


Transformateurs de puissance Leistungstransformatoren
Partie 11: Transformateurs de type sec Teil 11: Trockentransformatoren
(CEI 60076-11:2004) (IEC 60076-11:2004)






This European Standard was approved by CENELEC on 2004-07-01. 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 Central Secretariat 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 Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels


© 2004 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60076-11:2004 E

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EN 60076-11:2004 - 2 -
Foreword
The text of document 14/476/FDIS, future edition 1 of IEC 60076-11, prepared by IEC TC 14, Power
transformers, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 60076-11 on 2004-07-01.
This European Standard supersedes EN 60726:2003.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2005-04-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2007-07-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60076-11:2004 was approved by CENELEC as a European
Standard without any modification.
__________

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- 3 - EN 60076-11:2004
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications
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.
NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
IEC 60050 Series International Electrotechnical Vocabulary- -

IEC 60071 Series Insulation co-ordination EN 60071 Series

IEC 60076-1 1993 Power transformers EN 60076-1 1997
(mod) Part 1: General A11 1997
A1 1999 A1 2000
A12 2002

1) 2)
IEC 60076-2 - Part 2: Temperature rise EN 60076-2 1997
(mod)

1) 2)
IEC 60076-3 - Part 3: Insulation levels, dielectric tests EN 60076-3 2001
and external clearances in air

1) 2)
IEC 60076-5 - Part 5: Ability to withstand short circuit EN 60076-5 2000

1) 2)
IEC 60076-10 - Part 10: Determination of sound levels EN 60076-10 2001

1)
IEC 60085 - Electrical insulation - Thermal - -
classification

1) 2)
IEC 60270 - High-voltage test techniques - Partial EN 60270 2001
discharge measurements

1)
IEC 60332-3-10 - Test on electric cables under fire - -
conditions
Part 3-10: Test for vertical flame spread
of vertically-mounted bunched wires or
cables - Apparatus

1) 2)
IEC 60529 - Degrees of protection provided by EN 60529 1991
enclosures (IP Code) + corr. May 1993

IEC 60905 1987 Loading guide for dry-type power - -
transformers

1) 2)
IEC 61330 - High-voltage/low-voltage prefabricated EN 61330 1996
substations


1)
Undated reference.
2)
Valid edition at date of issue.

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NORME CEI
INTERNATIONALE IEC
60076-11
INTERNATIONAL
Première édition
STANDARD
First edition
2004-05
Transformateurs de puissance –
Partie 11:
Transformateurs de type sec
Power transformers –
Part 11:
Dry-type transformers
© IEC 2004 Droits de reproduction réservés ⎯ Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
CODE PRIX
PRICE CODE W
Commission Electrotechnique Internationale
International Electrotechnical Commission
ɆɟɠɞɭɧɚɪɨɞɧɚɹɗɥɟɤɬɪɨɬɟɯɧɢɱɟɫɤɚɹɄɨɦɢɫɫɢɹ
Pour prix, voir catalogue en vigueur
For price, see current catalogue

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60076-11 © IEC:2004 – 3 –
CONTENTS
FOREWORD.9
1 Scope.13
2 Normative references.13
3 Definitions.15
4 Service conditions .15
4.1 General.15
4.2 Normal service conditions .15
4.3 Electromagnetic compatibility (EMC) .17
4.4 Provision for unusual service conditions .17
4.5 Transport and storage conditions .19
5 Tappings.19
6 Connections.19
7 Ability to withstand short circuit .19
8 Rating.21
8.1 General.21
8.2 Rated power.21
8.3 Preferred values of rated power .21
8.4 Operation at higher than rated voltage .21
8.5 Operation with fan cooling .21
8.6 Operation in an enclosure .21
9 Rating plate.23
9.1 Rating plate fitted to the transformer .23
9.2 Rating plate fitted to the transformer enclosure .23
10 Identification according to cooling method .23
10.1 Identification symbols.23
10.2 Arrangement of symbols.25
11 Temperature-rise limits.25
11.1 Normal temperature-rise limits.25
11.2 Reduced temperature rises for transformers designed for high cooling air
temperatures or special air cooling conditions .27
11.3 High altitude temperature rise correction .27
12 Insulation levels.27
12.1 General.27
12.2 Transformers for use at high altitudes .31
13 Climatic, environmental and fire behaviour classes.31
13.1 Climatic classes.31
13.2 Environmental classes.31
13.3 Fire behaviour classes.31
13.4 Test criteria for climatic, environmental and fire behaviour classes.33
14 General requirements for tests .33
15 Measurement of winding resistance (routine test) .33

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60076-11 © IEC:2004 – 5 –
16 Measurement of voltage ratio and check of phase displacement (routine test) .35
17 Measurement of short-circuit impedance and load loss (routine test) .35
18 Measurement of no-load loss and current (routine test) .35
19 Separate-source AC withstand voltage test (routine test).35
20 Induced AC withstand voltage test (routine test) .35
21 Lightning impulse test (type test) .37
22 Partial discharge measurement (routine and special test) .37
22.1 General.37
22.2 Basic measuring circuit (typical only).37
22.3 Calibration of the measuring circuit .37
22.4 Voltage application.39
22.5 Partial discharge acceptance levels.41
23 Temperature-rise test (type test) .43
23.1 General.43
23.2 Methods of loading .43
23.3 Winding temperature-rise correction for reduced current .49
23.4 Determination of steady state conditions .49
24 Measurement of sound level (special test) .49
25 Short-circuit test (special test) .51
26 Environmental test (special test).51
26.1 General.51
26.2 Validity of the test .51
26.3 Testing procedure.51
27 Climatic test (special test) .53
27.1 Thermal shock test (special test) .53
27.2 Validity of the test .53
27.3 Thermal shock test for C1 class transformers .55
27.4 Thermal shock test for C2 class transformers .57
28 Fire behaviour test (special test) .57
28.1 General.57
28.2 Checking of corrosive and harmful gases emission.57
28.3 Fire behaviour test for F1 class transformer .59
28.4 Quantities to be measured and measuring devices .63
28.5 Calibration of the test chamber without test object.63
28.6 Test method.63
28.7 Test report.65
28.8 Criteria for evaluating the test results .65
29 Tolerances.67
30 Protection against direct contact.67
31 Degrees of protection provided by enclosures .67
32 Earthing terminal.67
33 Information required with enquiry and order.67
Annex A (informative) Installation and safety of dry-type transformers .73

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60076-11 © IEC:2004 – 7 –
Figure 1 – Basic measuring circuit for the partial discharge test for a single-phase
transformer .39
Figure 2 – Basic measuring circuit for the partial discharge test for a three-phase
transformer .39
Figure 3 – Voltage application for routine partial discharge test .41
Figure 4 – Voltage application for special partial discharge test .41
Figure 5 – Example of back-to- back method – Single phase. .47
Figure 6 – Example of back-to-back method – Three-phase.47
Figure 7 – Test chamber .69
Figure 8 – Test chamber details.71
Table 1 – Letter symbols.25
Table 2 – Winding temperature-rise limits .27
Table 3 – Insulation levels based on European practice.29
Table 4 – Insulation levels based on North American practice.29
Table 5 – sequence of tests .33
Table 6 – Dimensions of test chamber (see Figures 7 and 8) .61

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60076-11 © IEC:2004 – 9 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER TRANSFORMERS –
Part 11: Dry-type transformers
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.
International Standard IEC 60076-11 has been prepared by IEC technical committee 14:
Power transformers.
This standard cancels and replaces IEC 60726 (1982) and its amendment 1 (1986).
The text of this standard is based on the following documents:
FDIS Report on voting
14/476/FDIS 14/484/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.

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60076-11 © IEC:2004 – 11 –
IEC 60076 consists of the following parts, under the general title Power transformers:
Part 1: General
Part 2: Temperature rise
Part 3: Insulation levels, dielectric tests and external clearances in air
Part 4: Guide to lightning impulse and switching impulse testing – Power transformers
and reactors
Part 5: Ability to withstand short-circuit
1
Part 6: Reactors
1
Part 7: Loading guide for oil-immersed power transformers
Part 8: Application guide
Part 10: Determination of sound levels
1
Part 10-1: Determination of transformer and reactor sound levels – User guide
Part 11: Dry-type transformers
1
Part 12: Loading guide for dry-type power transformers
1
Part 13: Self protected liquid filled transformers
Part 14: Guide for the design and application of liquid-immersed power transformers
1
using high-temperature insulation materials
1
Part 15: Gas-filled-type power transformers
The committee has decided that the contents of this publication will remain unchanged until
2006. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
___________
1
Under consideration.

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60076-11 © IEC:2004 – 13 –
POWER TRANSFORMERS –
Part 11: Dry-type transformers
1 Scope
This part of IEC 60076 applies to dry-type power transformers (including auto-transformers)
having values of highest voltage for equipment up to and including 36 kV and at least one
winding operating at greater than 1,1 kV. The standard applies to all construction
technologies.
This standard does not apply to:
– gas-filled dry type transformers where the gas is not air;
– single-phase transformers rated at less than 5 kVA;
– polyphase transformers rated at less than 15 kVA;
– instrument transformers (see IEC 60044 and IEC 60186);
– starting transformers;
– testing transformers;
– traction transformers mounted on rolling stock;
– flameproof and mining transformers;
– welding transformers;
– voltage regulating transformers;
– small power transformers in which safety is a special consideration.
Where IEC standards do not exist for the transformers mentioned above or for other special
transformers, this standard may be applicable as a whole or in parts.
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 60050 (all parts), International electrotechnical vocabulary (IEV)
IEC 60071 (all parts), Insulation co-ordination
IEC 60076-1:1993, Power transformers – Part 1: General
Amendment 1 (1999)
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

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60076-11 © IEC:2004 – 15 –
IEC 60076-5, Power transformers – Part 5: Ability to withstand short-circuit
IEC 60076-10, Power transformers – Part 10: Determination of sound levels
IEC 60085, Thermal evaluation and classification of electrical insulation
IEC 60270, High-voltage test techniques – Partial discharge measurements
IEC 60332-3-10, Tests on electric cables under fire conditions – Part 3-10: Test for vertical
flame spread of vertically-mounted bunched wires or cables – Apparatus
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60905:1987, Loading guide for dry-type power transformers
IEC 61330, High-voltage/low voltage prefabricated substations
3 Terms and definitions
For the purpose of this part of IEC 60076, the following terms and definitions apply.
3.1
dry-type transformer
transformer of which the magnetic circuit and windings are not immersed in an insulating
liquid
3.2
totally enclosed dry-type transformer
transformer in an un-pressurised enclosure cooled by the circulation of the internal air
3.3
enclosed dry-type transformer
transformer in a ventilated enclosure cooled by the circulation of the external air
3.4
non-enclosed dry-type transformer
transformer supplied without a protective enclosure cooled by natural or forced air ventilation
4 Service conditions
4.1 General
The requirements of IEC 60076-1 apply to dry-type transformers only in so far as they are
referred to in this standard.
4.2 Normal service conditions
4.2.1 General
Unless otherwise stated, the service conditions in 4.2.2 to 4.2.6 apply. When transformers are
required to operate outside the normal service conditions, de-rating in accordance with 11.2
and/or 11.3 applies.

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60076-11 © IEC:2004 – 17 –
4.2.2 Altitude
A height above sea level not exceeding 1 000 m.
4.2.3 Temperature of cooling air
The temperature of cooling air not exceeding:
40 °C at any time;
30 °C monthly average of the hottest month;
20 °C yearly average.
and not below:
–25 °C in the case of outdoor transformers;
–5 °C in the case of indoor transformers.
where the monthly and yearly averages are as defined in 3.12 of IEC 60076-1.
4.2.4 Wave-shape of supply voltage
A supply voltage of which the waveshape is approximately sinusoidal.
NOTE This requirement is normally not critical in public supply systems but may have to be considered in
installations with considerable converter loading. In such cases, there is a conventional rule that the deformation
shall neither exceed 5 % total harmonic content nor 1 % even harmonic content, see IEC 61000-2-4. Also note the
importance of current harmonics for load loss and temperature rise, see IEC 61378-1.
4.2.5 Symmetry of polyphase supply voltages
For three-phase transformers, a set of three-phase supply voltages which are approximately
symmetrical.
4.2.6 Humidity
The relative humidity of the surrounding air shall be less than 93 %. No drops of water shall
be present on the surface of the coils.
4.3 Electromagnetic compatibility (EMC)
Transformers shall be considered as passive elements in respect to emission and immunity to
electromagnetic disturbances.
4.4 Provision for unusual service conditions
The purchaser shall identify in his enquiry any service conditions not covered by the normal
service conditions in 4.2. Examples of such conditions are:
– high or low ambient temperature outside the limits prescribed in 4.2.3;
– restricted ventilation;
– altitude in excess of the limit prescribed in 4.2.2;
– damaging fumes and vapours;
– steam;
– humidity in excess of the limit prescribed in 4.2.6;
– dripping water;
– salt spray;

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60076-11 © IEC:2004 – 19 –
– excessive and abrasive dust;
– high harmonic content of the load current;
– distortion of the supply voltage waveform;
– fast transient overvoltages over the limits prescribed in 12.1 and Clause 21;
– associated power factor correction and method of capacitor switching to limit inrush
current;
– superimposed DC current;
– seismic qualification which would otherwise require special considerations in the design;
– extreme mechanical shock and vibrations;
– transport and storage conditions not covered by the normal condition described in 4.5.
Transformer specification for operation under such abnormal conditions shall be subject to
agreement
...