IEC 60076-11:2018

Power transformers - Part 11: Dry-type transformers

IEC 60076-11:2018 applies to dry-type power transformers (including auto-transformers) having values of highest voltage for equipment up to and including 72,5 kV and at least one winding operating at greater than 1,1 kV. This document 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;
- 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 document may be applicable as a whole or in parts. This second edition cancels and replaces the first edition published in 2004 and constitutes a technical revision. The main changes with regard to the previous edition are as follows:
- Extension of the scope up to 72,5kV
- Enclosure management in regards of the performance
- Management of the dielectric and thermal features with altitude
- New climatic classes for a better adaptation of customers’ need
- Establishment of the relation between location and environmental classes
- For fire behaviour classes, limitation at 1000kVA and process of test more robust
- Introduction of Seismic class
- Recommendations for amorphous transformers
Keywords: dry-type transformers
The contents of the corrigendum of March 2019 and the Interpretation sheet 1 of July 2020 have been included in this copy.

Transformateurs de puissance - Partie 11 : Transformateurs de type sec

L'IEC 60076-11:2018 applique aux transformateurs de type sec (y compris les autotransformateurs) dont les valeurs de tension la plus élevée pour le matériel sont inférieures ou égales à 72,5 kV avec au moins un enroulement fonctionnant à plus de 1,1 kV. Le présent document ne s'applique pas aux:
- transformateurs de type sec avec un diélectrique gazeux autre que l'air;
- transformateurs monophasés de moins de 5 kVA;
- transformateurs polyphasés de moins de 15 kVA;
- transformateurs de mesure;
- transformateurs de démarrage;
- transformateurs d'essai;
- transformateurs de traction montés sur matériel roulant;
- transformateurs antidéflagrants et de mines;
- transformateurs de soudure;
- transformateurs de réglage de tension;
- petitstransformateurs de puissance pour lesquels la sécurité est spécialement à prendre en compte.
Lorsqu'il n'existe pas de norme IEC pour les transformateurs mentionnés ci-dessus ou pour d'autres transformateurs spéciaux, le présent document peut être appliquée en tout ou en partie. Cette deuxième édition annule et remplace la première édition publiée en 2004 dont elle constitue une révision technique.
Les principales modifications par rapport à l'édition précédente sont les suivantes:
- Extension du domaine d'application jusqu'à 72,5 kV
- Prise en compte des enveloppes en ce qui concerne les performances
- Prise en compte des caractéristiques diélectriques et thermiques en fonction de l'altitude
- Nouvelles classes climatiques pour une meilleure adaptation des besoins des clients
- Établissement de la relation entre l'emplacement et les classes d'environnement
- Pour les classes de comportement au feu, limitation à 1 000 kVA et processus d'essai plus robuste
- Introduction d'une classe sismique
- Recommandations pour les transformateurs amorphes
Mots-clés: transformateurs de type sec
Le contenu du corrigendum de mars 2019 et la feuille d'interprétation 1 de juillet 2020 (seulement en anglais) a été pris en considération dans cet exemplaire.

General Information

• Status: Published
• Publication Date: 14-Aug-2018
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 29.180 - Transformers. Reactors
• Technical Committee: TC 14 - Power transformers
• Drafting Committee: MT 60076-11 - TC 14/MT 60076-11
• Current Stage: PPUB - Publication issued
• Start Date: 03-Aug-2018
• Completion Date: 15-Aug-2018

Relations

• Revised: IEC 60076-11:2018/ISH1:2020 - Interpretation sheet 1 - Power transformers - Part 11: Dry-type transformers
• Effective Date: 05-Sep-2023
• Revises: IEC 60076-11:2004 - Power transformers - Part 11: Dry-type transformers
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 60076-11 ®
Edition 2.0 2018-08
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Power transformers –
Part 11: Dry-type transformers

IEC IEC 60076-11:2018-08 RLV(en)

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
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IEC 60076-11 ®
Edition 2.0 2018-08
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Power transformers –
Part 11: Dry-type transformers

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.180 ISBN 978-2-8322-5967-2

© IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
IEC 60076-11
Edition 2.0  2018-08
POWER TRANSFORMERS –
Part 11: Dry-type transformers

INTERPRETATION SHEET 1
This interpretation sheet has been prepared by IEC technical committee 14: Power
transformers.
The text of this interpretation sheet is based on the following documents:
DISH Report on voting
14/1052/DISH 14/1054/RVDISH
Full information on the voting for the approval of this interpretation sheet can be found in the
report on voting indicated in the above table.

___________
14.3.2 Temperature-rise test
Question
The independent certification body in Poland "Instytut Energetyki" carries out the testing of
transformers or its inspectors witness this testing at the manufacturers' premises. The
description of resistance measurement during the temperature rise test has caused a dispute
between a manufacturer and the inspector on where exactly the resistance should be
measured. The inspector requested that the resistance be measured on "winding lead exits"
inside the enclosure, while the manufacturer argued for the measurement to be made on
"winding terminals" which in its opinion were the bushings on the enclosure cover.
ICS 29.180
– 2 – IEC 60076-11:2018/ISH1:2020
© IEC 2020
Subclause 14.3.2.1 General, states:
The winding temperature rise shall be established by the rise in resistance method or
by superposition method. For the determination of the average winding temperature
rise the measured temperatures of the cooling air or of the water intake of the cooling
equipment shall be used.
For three-phase transformers, the resistance measurements shall be made between
the central and an outer phase line terminals.
NOTE When the temperature rise is performed it is advisable to measure the windings resistance close to the
windings.
Where should the measurements be made?
Interpretation
Testing of the winding resistance at transformer terminals (bushings) includes leadwork or
busbars and often also multiple connections. Because of this, the tested winding resistance
and its change due to heating is affected by the resistance of all these leads and connections.
Consequently, the derived winding temperature rise if measured at the transformer terminals
could be lower than if the winding resistance were tested directly on the winding lead exits.
That is why the standard suggests (in the NOTE) that measurement of the windings'
resistance be carried out close to the windings. That way, the accuracy of the indirect winding
temperature measurement by resistance is higher.
In the case of dry-type transformers without enclosures, it is possible to have access close to
the winding lead exits and not only to the transformer line terminals. Therefore,
measurements shall normally be made at such locations.
On the other hand, if the dry-type transformer is equipped with an enclosure, the resistance
measurement close to the winding lead exits requires opening the enclosure to have access
to carry out the test (hence, affecting the normal cooling efficiency of the unit). Nevertheless,
the advice to measure the resistance normally close to the winding lead exits holds. Limiting
the enclosure opening by using special through elements for the cabling and/or by closing the
required opening by temporary means as well as possible will minimize the impact on the
normal cooling efficiency.
– 2 – IEC 60076-11:2018 RLV © IEC 2018
CONTENTS
FOREWORD . 6
1 Scope . 8
2 Normative references. 8
3 Terms and definitions . 9
4 Service conditions . 10
4.1 General . 10
4.2 Normal service conditions . 10
4.3 Electromagnetic compatibility (EMC) . 12
5 Rating and general requirements . 12
5.1 General . 12
5.2 Rated power . 12
5.2.1 General . 12
5.2.2 Operation Definition of the rated power with fans cooling or heat
exchangers . 13
5.2.3 Transformer IP00 (without enclosure) . 13
5.2.4 Operation in an Transformer with enclosure . 13
5.2.5 Preferred values of rated power . 14
5.2.6 Loading beyond rated power . 14
5.3 Provision for unusual service conditions . 14
5.4 Transportation and storage conditions . 15
5.4.1 Transport limitation . 15
5.4.2 Transport acceleration . 15
5.4.3 Temperature and environment conditions for transport and storage . 15
5.5 Rated voltage and rated frequency . 15
5.5.1 Rated voltage . 15
5.5.2 Rated frequency . 16
5.6 Operation at higher than rated voltage . 16
5.7 Highest voltage for equipment U and dielectric tests levels . 16
m
5.8 Identification according to cooling method . 16
5.8.1 General . 16
5.8.2 Identification symbols . 16
5.8.3 Arrangement of symbols . 17
5.9 Guaranteed temperature rise at rated conditions . 17
5.10 Additional information required for enquiry . 17
5.11 Sound level . 17
5.12 Components and materials . 17
6 Tappings . 17
7 Connections . 18
8 Ability to withstand short circuit . 18
9 Rating plate . 18
9.1 Rating plate fitted to the transformer . 18
9.2 Rating plate fitted to the transformer enclosure . 19
10 Temperature-rise limits . 19
10.1 Normal temperature-rise limits . 19

10.2 Reduced temperature rises for transformers designed for high cooling air
medium temperatures or special air cooling medium conditions . 20
10.3 High altitude temperature rise correction . 20
11 Insulation levels . 21
11.1 General . 21
11.2 Transformers for use at high altitudes . 22
12 Climatic, environmental and fire behaviour classes . 23
12.1 Climatic classes . 23
12.2 Environmental classes . 24
12.2.1 Transformers for indoor application with or without enclosure and for
outdoor application with enclosure . 24
12.2.2 Dry-type transformers without enclosure for outdoor application . 25
12.3 Fire behaviour classes . 25
12.4 Test criteria for climatic, environmental and fire behaviour classes . 25
13 Seismic . 26
13.1 General . 26
13.2 General seismic class approach . 27
13.2.1 Generalities . 27
13.2.2 The standard amplitude method . 27
13.2.3 The calculated amplitude method . 28
14 Test . 29
14.1 General requirements fo
...

IEC 60076-11 ®
Edition 2.0 2018-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Power transformers –
Part 11: Dry-type transformers

Transformateurs de puissance –
Partie 11: Transformateurs de type sec

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
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About the IEC
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International Standards for all electrical, electronic and related technologies.

About IEC publications
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latest edition, a corrigenda or an amendment might have been published.

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IEC 60076-11 ®
Edition 2.0 2018-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Power transformers –
Part 11: Dry-type transformers

Transformateurs de puissance –

Partie 11: Transformateurs de type sec

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.180 ISBN 978-2-8322-5910-8

– 2 – IEC 60076-11:2018 © IEC 2018
CONTENTS
FOREWORD . 6
1 Scope . 8
2 Normative references. 8
3 Terms and definitions . 9
4 Service conditions . 10
4.1 General . 10
4.2 Normal service conditions . 10
4.3 Electromagnetic compatibility (EMC) . 11
5 Rating and general requirements . 12
5.1 General . 12
5.2 Rated power . 12
5.2.1 General . 12
5.2.2 Definition of the rated power with fans cooling or heat exchangers . 12
5.2.3 Transformer IP00 (without enclosure) . 12
5.2.4 Transformer with enclosure . 12
5.2.5 Preferred values of rated power . 13
5.2.6 Loading beyond rated power . 13
5.3 Provision for unusual service conditions . 13
5.4 Transportation and storage . 14
5.4.1 Transport limitation . 14
5.4.2 Transport acceleration . 14
5.4.3 Temperature and environment conditions for transport and storage . 14
5.5 Rated voltage and rated frequency . 15
5.5.1 Rated voltage . 15
5.5.2 Rated frequency . 15
5.6 Operation at higher than rated voltage . 15
5.7 Highest voltage for equipment U and dielectric tests levels . 15
m
5.8 Identification according to cooling method . 15
5.8.1 General . 15
5.8.2 Identification symbols . 15
5.8.3 Arrangement of symbols . 16
5.9 Guaranteed temperature rise at rated conditions . 16
5.10 Additional information required for enquiry . 16
5.11 Sound level . 16
5.12 Components and materials . 16
6 Tappings . 16
7 Connections . 17
8 Ability to withstand short circuit . 17
9 Rating plate . 17
9.1 Rating plate fitted to the transformer . 17
9.2 Rating plate fitted to the transformer enclosure . 18
10 Temperature-rise limits . 18
10.1 Normal temperature-rise limits . 18
10.2 Reduced temperature rises for transformers designed for high cooling
medium temperatures or special cooling medium conditions . 19

10.3 High altitude temperature rise correction . 19
11 Insulation levels . 19
11.1 General . 19
11.2 Transformers for use at high altitudes . 20
12 Climatic, environmental and fire behaviour classes . 21
12.1 Climatic classes . 21
12.2 Environmental classes . 21
12.2.1 Transformers for indoor application with or without enclosure and for
outdoor application with enclosure . 21
12.2.2 Dry-type transformers without enclosure for outdoor application . 22
12.3 Fire behaviour classes . 22
12.4 Test criteria for climatic, environmental and fire behaviour classes . 23
13 Seismic . 23
13.1 General . 23
13.2 General seismic class approach . 24
13.2.1 Generalities . 24
13.2.2 The standard amplitude method . 24
13.2.3 The calculated amplitude method . 25
14 Test . 26
14.1 General requirements for tests . 26
14.2 Routine tests . 27
14.2.1 Measurement of winding resistance . 27
14.2.2 Measurement of voltage ratio and check of phase displacement . 27
14.2.3 Measurement of short-circuit impedance and load loss . 27
14.2.4 Measurement of no-load loss and current . 28
14.2.5 Applied voltage test (AV) . 28
...