FOREWORD

1 Scope

2 Normative references

3 Terms and definitions

3.1 General

3.2 Terminals and neutral point

3.3 Windings

3.4 Rating

3.5 Tappings

3.6 Losses and no-load current

3.7 Short-circuit impedance and voltage drop

3.9 Insulation

3.10 Connections

3.11 Test classification

3.12 Meteorological data with respect to cooling

3.13 Other definitions

4 Service conditions

4.1 General

4.2 Normal service conditions

5 Rating and general requirements

5.1 Rated power

5.1.1 General

5.1.2 Preferred values of rated power

5.1.3 Minimum power under alternative cooling modes

5.1.4 Loading beyond rated power

5.2 Cooling mode

5.3 Load rejection on transformers directly connected to a generator

5.4 Rated voltage and rated frequency

5.4.1 Rated voltage

5.4.2 Rated frequency

5.4.3 Operation at higher than rated voltage and/or at other than rated frequency

5.5 Provision for unusual service conditions

5.6 Highest voltage for equipment Um and dielectric tests levels

5.7 Additional information required for enquiry

5.7.1 Transformer classification

5.7.2 Winding connection and number of phases

5.7.3 Sound level

5.7.4 Transport

5.8 Components and materials

6 Requirements for transformers having a tapped winding

6.1 General – Notation of tapping range

6.2 Tapping voltage – tapping current. Standard categories of tapping voltage variation. Maximum voltage tapping

6.3 Tapping power. Full-power tappings – reduced-power tappings

6.4 Specification of tappings in enquiry and order

6.4.1 General

6.4.2 Constructional specification

6.4.3 Functional specification

6.5 Specification of short-circuit impedance

6.6 Load loss and temperature rise

7 Connection phase displacement symbols

7.1 Connection and phase displacement symbols for three-phase transformers and for single phase transformers connected in a three phase bank

7.1.1 Connection symbol

7.1.2 Phase displacement in clock number notation

7.1.3 Windings not intended to be loaded

7.1.4 Reconnectable windings

7.1.5 Examples

7.2 Connection and phase displacement symbols for single phase transformers not in three phase bank

7.2.1 Connection symbol

7.2.2 Phase displacement in clock number notation

7.2.3 Windings not intended to be loaded

7.2.4 Reconnectable windings

8 Rating plates

8.1 General

8.2 Information to be given in all cases

8.3 Additional information to be given when applicable

9 Safety, environmental and other requirements

9.1 Safety and environmental requirements

9.1.1 Liquid leaks

9.1.2 Safety considerations

9.2 Dimensioning of neutral connection

9.3 Liquid preservation system

9.4 DC currents in neutral circuits

9.5 Centre of gravity marking

10 Tolerances

11 Tests

11.1 General requirements for routine, type and special tests

11.1.1 General

11.1.2 Routine tests

11.1.3 Type tests

11.1.4 Special tests

11.2 Measurement of winding resistance

11.2.1 General

11.2.2 Dry-type transformers

11.2.3 Liquid-immersed type transformers

11.3 Measurement of voltage ratio and check of phase displacement

11.4 Measurement of short-circuit impedance and load loss

11.5 Measurement of no-load loss and current

11.6 Measurement of zero-sequence impedance(s) on three-phase transformers

11.7 Tests on on-load tap-changers ─ Operation test

11.8 Leak testing with pressure for liquid immersed transformers (tightness test)

11.9 Vacuum deflection test for liquid immersed transformers

11.10 Pressure deflection test for liquid immersed transformers

11.11 Vacuum tightness test on site for liquid immersed transformers

11.12 Check of core and frame insulation

12 Electromagnetic compatibility (EMC)

13 High frequency switching transients

Annex A (informative) Check list of information to be provided with enquiry and order

Annex B (informative) Examples of specifications for transformers with tappings

Annex C (informative) Specification of short-circuit impedance by boundaries

Annex D (informative) Examples of three-phase transformer connections

Annex E (normative) Temperature correction of load loss

Annex F (informative) Facilities for future fitting of condition monitoring systems to transformers

Annex G (informative) Environmental and safety considerations

Bibliography

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IEC 60076-1:2011

Gulf StandardGSO IEC 60076-1:2014

GSO IEC 60076-1:2014Gulf Standard

GSO IEC 60076-1:2014

IEC 60076-1:2011

مواصفة قياسية خليجية

محولات القدرة –الجزء 1: عام

Gulf Standard

Power transformer –Part1:General

ICS:	17.220.20 ; 29.180

English Language – اللغةالإنجليزيةEdition 1 – 06/08/2014 – 1 الطبعة

هذه الوثيقة محمية بالقانون

ما لم ينص على خلاف ذلك، لا يجوز إعادة إنتاج أي جزء من هذا المنشور أو استخدامه بأي شكل آخر أو بأي وسيلة، إلكترونية أو ميكانيكية، بما في ذلك التصوير، أو النشر على الإنترنت أو الإنترانت، دون إذن كتابي مسبق من هيئة التقييس لدول مجلس التعاون لدول الخليج العربية على العنوان أدناه أو الدول الأعضاء في الهيئة داخل بلدانهم.

All rights reserved to GCC Standardization Organization (GSO). Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either GSO at the address below or GSO's member body in the country of the requester.

Outreach Dept, Knowledge Management Section

GCC Standardization Organization (GSO)

P.O.Box: 85245 Riyadh 12511

Kingdom of Saudi Arabia

إدارة التواصل، قسم إدارة المعرفة

هيئة التقييس لدول مجلس التعاون لدول الخليج العربية (GSO)

ص. ب: 85245 الرياض 12511

المملكة العربية السعودية

Tel:

+966115208000

:هاتف

Fax:

+966115208010

:فاكس

E-Mail:

csc@gso.org.sa

:بريد إلكتروني

Website:

www.gso.org.sa

:موقع ويب

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IEC 60076-1:2011

Gulf StandardGSO IEC 60076-1:2014

GSO IEC 60076-1:2014Gulf Standard

Gulf Foreword

GCC Standardization Organization (GSO) is a regional organization which consists of the national standardization bodies of GCC member states. One of GSO main functions is to issue gulf standards and technical regulations through specialized technical committees.

GSO Technical Council in its meeting number (33) held on 09/10/1435 H, which corresponds to 06/08/2014, has approved Gulf Standard GSO IEC 60076-1:2014 titled "Power transformer –Part1:General" in English language which was studied and adopted by endorsement from International Electrotechnical Commission Standard IEC 60076-1:2011 through the technical program of GSO Technical Committee for Electrical and Electronic Products (TC03) in UNITED ARAB EMIRATES schedule .

تقديم خليجي

هيئة التقييس لدول مجلس التعاون لدول الخليج العربية هيئة إقليمية تضم في عضويتها أجهزة التقييس الوطنية في الدول الأعضاء ، ومن مهام الهيئة إعداد المواصفات القياسية واللوائح الفنية الخليجية بواسطة لجان فنية متخصصة.

قرر المجلس الفني لهيئة التقييس لدول مجلس التعاون لدول الخليج العربية في الاجتماع الـ (33) بتاريخ 1435/10/09 هـ ،الموافق 2014/08/06م اعتماد المواصفة القياسية الخليجية رقم GSO IEC 60076-1:2014 وعنوانها "محولات القدرة –الجزء 1: عام" باللغة الانجليزية التي تم دراستها وتبنيها بالمصادقة عن اللجنة الدولية الكهروتقنية رقم IEC 60076-1:2011 ضمن برنامج عمل اللجنة الفنية الخليجية للمواصفات الكهربائية والإلكترونية (TC03) المدرجة في خطة الإمارات العربية المتحدة .

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IEC 60076-1:2011 ED3 © IEC 2011

– –

IEC 60076-1:2011 ED3 © IEC 2011

Gulf StandardGSO IEC 60076-1:2014

GSO IEC 60076-1:2014Gulf Standard

IEC 60076-1

	INTERNATIONAL STANDARD	Edition 3.0 2011-04


	Power transformers – Part 1: General

IEC 60076-1:2011 ED3

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Gulf StandardGSO IEC 60076-1:2014

GSO IEC 60076-1:2014Gulf Standard

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.

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Tel.: +41 22 919 02 11 info@iec.ch www.iec.ch

About the IEC The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes International Standards for all electrical, electronic and related technologies. 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 corrigendum or an amendment might have been published.

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IEC 60076-1:2011 ED3 © IEC 2011

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IEC 60076-1:2011 ED3 © IEC 2011

Gulf StandardGSO IEC 60076-1:2014

GSO IEC 60076-1:2014Gulf Standard

IEC 60076-1

	INTERNATIONAL STANDARD	Edition 3.0 2011-04


	Power transformers – Part 1: General

INTERNATIONAL

ELECTROTECHNCIAL

COMMISSION

ICS 29.180ISBN 9782889124381Warning! Make sure that you obtained this publication from an authorized distributor.© Registered trademark of the International Electrotechnical Commission

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IEC 60076-1:2011 ED3 © IEC 2011

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IEC 60076-1:2011 ED3 © IEC 2011

Gulf StandardGSO IEC 60076-1:2014

GSO IEC 60076-1:2014Gulf Standard

CONTENTS

FOREWORD

1 Scope

2 Normative references

3 Terms and definitions

3.1 General

3.2 Terminals and neutral point

3.3 Windings

3.4 Rating

3.5 Tappings

3.6 Losses and no-load current

3.7 Short-circuit impedance and voltage drop

3.9 Insulation

3.10 Connections

3.11 Test classification

3.12 Meteorological data with respect to cooling

3.13 Other definitions

4 Service conditions

4.1 General

4.2 Normal service conditions

5 Rating and general requirements

5.1 Rated power

5.1.1 General

5.1.2 Preferred values of rated power

5.1.3 Minimum power under alternative cooling modes

5.1.4 Loading beyond rated power

5.2 Cooling mode

5.3 Load rejection on transformers directly connected to a generator

5.4 Rated voltage and rated frequency

5.4.1 Rated voltage

5.4.2 Rated frequency

5.4.3 Operation at higher than rated voltage and/or at other than rated frequency

5.5 Provision for unusual service conditions

5.6 Highest voltage for equipment Um and dielectric tests levels

5.7 Additional information required for enquiry

5.7.1 Transformer classification

5.7.2 Winding connection and number of phases

5.7.3 Sound level

5.7.4 Transport

5.8 Components and materials

6 Requirements for transformers having a tapped winding

6.1 General – Notation of tapping range

6.2 Tapping voltage – tapping current. Standard categories of tapping voltage variation. Maximum voltage tapping

6.3 Tapping power. Full-power tappings – reduced-power tappings

6.4 Specification of tappings in enquiry and order

6.4.1 General

6.4.2 Constructional specification

6.4.3 Functional specification

6.5 Specification of short-circuit impedance

6.6 Load loss and temperature rise

7 Connection phase displacement symbols

7.1 Connection and phase displacement symbols for three-phase transformers and for single phase transformers connected in a three phase bank

7.1.1 Connection symbol

7.1.2 Phase displacement in clock number notation

7.1.3 Windings not intended to be loaded

7.1.4 Reconnectable windings

7.1.5 Examples

7.2 Connection and phase displacement symbols for single phase transformers not in three phase bank

7.2.1 Connection symbol

7.2.2 Phase displacement in clock number notation

7.2.3 Windings not intended to be loaded

7.2.4 Reconnectable windings

8 Rating plates

8.1 General

8.2 Information to be given in all cases

8.3 Additional information to be given when applicable

9 Safety, environmental and other requirements

9.1 Safety and environmental requirements

9.1.1 Liquid leaks

9.1.2 Safety considerations

9.2 Dimensioning of neutral connection

9.3 Liquid preservation system

9.4 DC currents in neutral circuits

9.5 Centre of gravity marking

10 Tolerances

11 Tests

11.1 General requirements for routine, type and special tests

11.1.1 General

11.1.2 Routine tests

11.1.3 Type tests

11.1.4 Special tests

11.2 Measurement of winding resistance

11.2.1 General

11.2.2 Dry-type transformers

11.2.3 Liquid-immersed type transformers

11.3 Measurement of voltage ratio and check of phase displacement

11.4 Measurement of short-circuit impedance and load loss

11.5 Measurement of no-load loss and current

11.6 Measurement of zero-sequence impedance(s) on three-phase transformers

11.7 Tests on on-load tap-changers ─ Operation test

11.8 Leak testing with pressure for liquid immersed transformers (tightness test)

11.9 Vacuum deflection test for liquid immersed transformers

11.10 Pressure deflection test for liquid immersed transformers

11.11 Vacuum tightness test on site for liquid immersed transformers

11.12 Check of core and frame insulation

12 Electromagnetic compatibility (EMC)

13 High frequency switching transients

Annex A (informative) Check list of information to be provided with enquiry and order

Annex B (informative) Examples of specifications for transformers with tappings

Annex C (informative) Specification of short-circuit impedance by boundaries

Annex D (informative) Examples of three-phase transformer connections

Annex E (normative) Temperature correction of load loss

Annex F (informative) Facilities for future fitting of condition monitoring systems to transformers

Annex G (informative) Environmental and safety considerations

Bibliography

INTERNATIONAL ELECTROTECHNICAL COMMISSION

International StandardIEC 60076-1:2011 ED3

Power transformers - Part 1: General

FOREWORD

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.

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.

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.

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.

IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any services carried out by independent certification bodies.

All users should ensure that they have the latest edition of this publication.

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.

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.

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 60076‑1 has been prepared by IEC technical committee 14: Power transformers.

This third edition cancels and replaces the second edition published in 1993, and its Amendment 1(1999). It is a technical revision.

This edition includes the following significant technical changes with respect to the previous edition:

–

addition of a definition of harmonic content;

–

addition of a subclause on transport;

–

addition of functional method of specification;

–

addition of connection symbols for single phase transformers;

–

addition of safety and environmental requirements;

–

addition of requirements for liquid preservation systems;

–

addition of a clause on DC currents;

–

addition of vacuum, pressure and leak tests on tanks;

–

the requirements formerly in Annex A are now incorporated in the text and Annex A is now an informative checklist;

–

informative annexes have been added on facilities for condition monitoring and environmental and safety considerations.

The text of this standard is based on the following documents:

FDIS	Report on voting
14/675/FDIS	14/682/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.

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 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.

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Gulf StandardGSO IEC 60076-1:2014

GSO IEC 60076-1:2014Gulf Standard

International StandardIEC 60076-1:2011 ED3

Power transformers - Part 1: General

1Scope

This part of IEC 60076 applies to three-phase and single-phase power transformers (including auto-transformers) with the exception of certain categories of small and special transformers such as:

–

single-phase transformers with rated power less than 1 kVA and three-phase transformers less than 5 kVA;

–

transformers, which have no windings with rated voltage higher than 1 000 V;

–

instrument transformers;

–

traction transformers mounted on rolling stock;

–

starting transformers;

–

testing transformers;

–

welding transformers;

–

explosion-proof and mining transformers;

–

transformers for deep water (submerged) applications.

When IEC standards do not exist for such categories of transformers (in particular transformer having no winding exceeding 1000 V for industrial applications), this part of IEC 60076 may still be applicable either as a whole or in part.

This standard does not address the requirements that would make a transformer suitable for mounting in a position accessible to the general public.

For those categories of power transformers and reactors which have their own IEC standards, this part is applicable only to the extent in which it is specifically called up by cross-reference in the other standard. Such standards exist for:

–

reactors in general (IEC 60076‑6);

–

dry-type transformers (IEC 60076‑11);

–

self-protected transformers (IEC 60076‑13);

–

gas-filled power transformers (IEC 60076‑15);

–

transformers for wind turbine applications (IEC 60076‑16);

–

traction transformers and traction reactors (IEC 60310);

–

converter transformers for industrial applications (IEC 61378‑1);

–

converter transformers for HVDC applications (IEC 61378‑2).

At several places in this part it is specified or recommended that an 'agreement' should be reached concerning alternative or additional technical solutions or procedures. Such agreement is made between the manufacturer and the purchaser. The matters should preferably be raised at an early stage and the agreements included in the contract specification.

2Normative 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 60076‑2, Power transformers – Part 2: Temperature rise for liquid-immersed transformers

IEC 60076‑3:2000, Power transformers – Part 3: Insulation levels, dielectric tests and external clearances in air

IEC 60076‑5:2006, Power transformers – Part 5: Ability to withstand short circuit

IEC 60076‑10:2001, Power transformers – Part 10: Determination of sound levels

IEC 60076‑11:2004, Power transformers – Part 11: Dry-type transformers

IEC 60137:2008, Insulated bushings for alternating voltages above 1 000 V

IEC 60214‑1:2003, Tap-changers – Part 1: Performance requirements and test methods

IEC 60296:2003, Fluids for electrotechnical applications – Unused mineral insulating oils for transformers and switchgear

IEC 60721‑3‑4:1995, Classification of environmental conditions – Part 3: Classification of groups of environmental parameters and their severities – Section 4: Stationary use at non-weatherprotected locations

ISO 9001:2008, Quality management systems – Requirements

3.1General

3.1.1

power transformer

a static piece of apparatus with two or more windings which, by electromagnetic induction, transforms a system of alternating voltage and current into another system of voltage and current usually of different values and at the same frequency for the purpose of transmitting electrical power

[SOURCE: IEC 60050‑421:1990, 421‑01‑01

modified

]

3.1.2

auto-transformer

a transformer in which at least two windings have a common part

[SOURCE: IEC 60050‑421:1990, 421‑01‑11]

Note 1 to entry: Where there is a need to express that a transformer is not auto-connected, use is made of terms such as separate winding transformer, or double-wound transformer (see IEC 60050‑421:1990, 421‑01‑13).

3.1.3

series transformer

a transformer, other than an autotransformer, of which one winding is intended to be connected in series with a circuit in order to alter its voltage and/or shift its phase. The other winding is an energizing winding

[SOURCE: IEC 60050‑421:1990, 421‑01‑12

modified

]

Note 1 to entry: Series transformers were called booster transformers in earlier editions of this standard.

3.1.4

liquid-immersed type transformer

a transformer in which the magnetic circuit and windings are immersed in liquid

3.1.5

dry-type transformer

a transformer in which the magnetic circuit and windings are not immersed in an insulating liquid

[SOURCE: IEC 60050‑421:1990, 421‑01‑16]

3.1.6

liquid preservation system

system in a liquid-filled transformer by which the thermal expansion of the liquid is accommodated.

Note 1 to entry: Contact between the liquid and external air may sometimes be diminished or prevented.

3.1.7

specified value

the value specified by the purchaser at the time of order

3.1.8

design value

the expected value given by the number of turns in the design in the case of turns ratio or calculated from the design in the case of impedance, no-load current or other parameters

3.1.9

highest voltage for equipment Um applicable to a transformer winding

the highest r.m.s. phase-to-phase voltage in a three-phase system for which a transformer winding is designed in respect of its insulation

3.2Terminals and neutral point

3.2.1

terminal

a conducting element intended for connecting a winding to external conductors

3.2.2

line terminal

a terminal intended for connection to a line conductor of a network

[SOURCE: IEC 60050‑421:1990, 421‑02‑01]

3.2.3

neutral terminal

for three-phase transformers and three-phase banks of single-phase transformers:

the terminal or terminals connected to the common point (the neutral point) of a star-connected or zigzag connected winding

for single-phase transformers:

the terminal intended for connection to a neutral point of a network

[SOURCE: IEC 60050‑421:1990, 421‑02‑02

modified

]

3.2.4

neutral point

the point of a symmetrical system of voltages which is normally at zero potential

3.2.5

corresponding terminals

terminals of different windings of a transformer, marked with the same letter or corresponding symbol

[SOURCE: IEC 60050‑421:1990, 421‑02‑03]

3.3Windings

3.3.1

winding

the assembly of turns forming an electrical circuit associated with one of the voltages assigned to the transformer

[SOURCE: IEC 60050‑421:1990, 421‑03‑01

modified

]

Note 1 to entry: For a three-phase transformer, the 'winding' is the combination of the phase windings (see 3.3.3).

3.3.2

tapped winding

a winding in which the effective number of turns can be changed in steps

3.3.3

phase winding

the assembly of turns forming one phase of a three-phase winding

[SOURCE: IEC 60050‑421:1990, 421‑03‑02

modified

]

Note 1 to entry: The term 'phase winding' should not be used for identifying the assembly of all coils on a specific leg.

3.3.4

high-voltage winding

HV winding*

the winding having the highest rated voltage

[SOURCE: IEC 60050‑421:1990, 421‑03‑03]

3.3.5

low-voltage winding

LV winding*

the winding having the lowest rated voltage

[SOURCE: IEC 60050‑421:1990, 421‑03‑04]

Note 1 to entry: For a series transformer, the winding having the lower rated voltage may be that having the higher insulation level.

3.3.6

intermediate-voltage winding*

a winding of a multi-winding transformer having a rated voltage intermediate between the highest and lowest winding rated voltages

[SOURCE: IEC 60050‑421:1990, 421‑03‑05]

3.3.7

auxiliary winding

a winding intended only for a small load compared with the rated power of the transformer

[SOURCE: IEC 60050‑421:1990, 421‑03‑08]

3.3.8

stabilizing winding

a supplementary delta-connected winding provided in a star-star-connected or star-zigzag-connected transformer to decrease its zero-sequence impedance, see 3.7.3

[SOURCE: IEC 60050‑421:1990, 421‑03‑09

modified

]

Note 1 to entry: A winding is referred to as a stabilizing winding only if it is not intended for three-phase connection to an external circuit.

3.3.9

common winding

the common part of the windings of an auto-transformer

[SOURCE: IEC 60050‑421:1990, 421‑03‑10]

3.3.10

series winding

the part of the winding of an auto-transformer or the winding of a series transformer which is intended to be connected in series with a circuit

[SOURCE: IEC 60050‑421:1990, 421‑03‑11

modified

]

3.3.11

energizing winding (of a series transformer)

the winding of a series transformer which is intended to supply power to the series winding

[SOURCE: IEC 60050‑421:1990, 421‑03‑12

modified

]

3.3.12

auto-connected windings

the series and common windings of an auto-transformer

3.4Rating

3.4.1

rating

those numerical values assigned to the quantities which define the operation of the transformer in the conditions specified in this part of IEC 60076 and on which the manufacturer's guarantees and the tests are based

3.4.2

rated quantities

quantities (voltage, current, etc.), the numerical values of which define the rating

Note 1 to entry: For transformers having tappings, rated quantities are related to the principal tapping (see 3.5.2), unless otherwise specified. Corresponding quantities with analogous meaning, related to other specific tappings, are called tapping quantities (see 3.5.9).

Note 2 to entry: Voltages and currents are always expressed by their r.m.s. values, unless otherwise specified.

3.4.3

rated voltage of a winding

the voltage assigned to be applied, or developed at no-load, between the terminals of an untapped winding, or of a tapped winding connected on the principal tapping (see 3.5.2), for a three-phase winding it is the voltage between line terminals

[SOURCE: IEC 60050‑421:1990, 421‑04‑01

modified

]

Note 1 to entry: The rated voltages of all windings appear simultaneously at no-load when the voltage applied to one of them has its rated value.

Note 2 to entry: For single-phase transformers intended to be connected in star to form a three-phase bank or to be connected between the line and the neutral of a three phase system, the rated voltage is indicated as the phase-to-phase voltage, divided by

\sqrt{3}

for example

400 / \sqrt{3} kV

Note 3 to entry: For single phase transformers intended to be connected between phases of a network, the rated voltage is indicated as the phase-to-phase voltage.

Note 4 to entry: For the series winding of a three-phase series transformer, which is designed as an open winding (see 3.10.5), the rated voltage is indicated as if the windings were connected in star.

3.4.4

rated voltage ratio

the ratio of the rated voltage of a winding to the rated voltage of another winding associated with a lower or equal rated voltage

[SOURCE: IEC 60050‑421:1990, 421‑04‑02

modified

]

3.4.5

rated frequency

the frequency at which the transformer is designed to operate

[SOURCE: IEC 60050‑421:1990, 421‑04‑03

modified

]

3.4.6

rated power

conventional value of apparent power assigned to a winding which, together with the rated voltage of the winding, determines its rated current

Note 1 to entry: Both windings of a two-winding transformer have the same rated power which by definition is the rated power of the whole transformer.

3.4.7

rated current

the current flowing through a line terminal of a winding which is derived from rated power Sr and rated voltage Ur for the winding

[SOURCE: IEC 60050‑421:1990, 421‑04‑05

modified

]

Note 1 to entry: For a three-phase winding the rated current Ir is given by:

I_{r} = \frac{S_{r}}{\sqrt{3} \times U_{r}}

Note 2 to entry: For single-phase transformer windings intended to be connected in delta to form a three-phase bank, the rated current is indicated as line current divided by

\sqrt{3}

I_{r} = \frac{I_{line}}{\sqrt{3}}

Note 3 to entry: For a single phase transformer not intended to be connected to form a three phase bank, the rated current is

I_{r} = \frac{S_{r}}{U_{r}}

Note 4 to entry: For open windings (see 3.10.5) of a transformer, the rated current of the open windings is the rated power divided by the number of phases and by the rated voltage of the open winding:

I_{r} = \frac{S_{r}}{No . of phases \times U_{r}}

3.5Tappings

3.5.1

tapping

in a transformer having a tapped winding, a specific connection of that winding, representing a definite effective number of turns in the tapped winding and, consequently, a definite turns ratio between this winding and any other winding with a fixed number of turns

Note 1 to entry: One of the tappings is the principal tapping, and other tappings are described in relation to the principal tapping by their respective tapping factors. See definitions of these terms below.

3.5.2

principal tapping

the tapping to which the rated quantities are related

[SOURCE: IEC 60050‑421:1990, 421‑05‑02]

3.5.3

tapping factor (corresponding to a given tapping)

the ratio:

\frac{U_{d}}{U_{r}} (tapping factor)

100 \frac{U_{d}}{U_{r}} (tapping factor expressed as a percentage)

where

Ur	is the rated voltage of the winding (see 3.4.3);
Ud	is the voltage which would be developed at no-load at the terminals of the winding, at the tapping concerned, by applying rated voltage to an untapped winding

Note 1 to entry: For series transformers, the tapping factor is the ratio of the voltage of the series winding corresponding to a given tapping to Ur.

[SOURCE: IEC 60050‑421:1990, 421‑05‑03

modified

]

3.5.4

plus tapping

a tapping whose tapping factor is higher than 1

[SOURCE: IEC 60050‑421:1990, 421‑05‑04]

3.5.5

minus tapping

a tapping whose tapping factor is lower than 1

[SOURCE: IEC 60050‑421:1990, 421‑05‑05]

3.5.6

tapping step

the difference between the tapping factors, expressed as a percentage, of two adjacent tappings

[SOURCE: IEC 60050‑421:1990, 421‑05‑06]

3.5.7

tapping range

the variation range of the tapping factor, expressed as a percentage, compared with the value '100'

Note 1 to entry: If this factor ranges from 100 + a to 100 – b, the tapping range is said to be: +a %, –b % or ±a %, if a = b.

[SOURCE: IEC 60050‑421:1990, 421‑05‑07]

3.5.8

tapping voltage ratio (of a pair of windings)

the ratio which is equal to the rated voltage ratio:

–

multiplied by the tapping factor of the tapped winding if this is the high-voltage winding;

–

divided by the tapping factor of the tapped winding if this is the low-voltage winding

[SOURCE: IEC 60050‑421:1990, 421‑05‑08]

Note 1 to entry: While the rated voltage ratio is, by definition, at least equal to 1, the tapping voltage ratio can be lower than 1 for certain tappings when the rated voltage ratio is close to 1.

3.5.9

tapping quantities

those quantities the numerical values of which define the duty of a particular tapping (other than the principal tapping)

Note 1 to entry: Tapping quantities exist for any winding in the transformer, not only for the tapped winding (see 6.2 and 6.3).The tapping quantities are:

–

tapping voltage (analogous to rated voltage, 3.4.3);

–

tapping power (analogous to rated power, 3.4.6);

–

tapping current (analogous to rated current, 3.4.7).

[SOURCE: IEC 60050‑421:1990, 421‑05‑10

modified

]

3.5.10

full-power tapping

a tapping whose tapping power is equal to the rated power

[SOURCE: IEC 60050‑421:1990, 421‑05‑14]

3.5.11

reduced-power tapping

a tapping whose tapping power is lower than the rated power

[SOURCE: IEC 60050‑421:1990, 421‑05‑15]

3.5.12

on-load tap-changer

OLTC

a device for changing the tapping connections of a winding, suitable for operation while the transformer is energized or on load

[SOURCE: IEC 60050‑421:1990, 421‑11‑01]

3.5.13

de-energized tap-changer

DETC

a device for changing the tapping connections of a winding, suitable for operation only while the transformer is de-energized (isolated from the system)

3.5.14

maximum allowable tapping service voltage

the voltage at rated frequency a transformer is designed to withstand continuously without damage at any particular tap position at the relevant tapping power

Note 1 to entry: This voltage is limited by Um.

Note 2 to entry: This voltage will normally be limited to 105 % of the rated tapping voltage unless a higher voltage is required by the purchaser’s specification of the tapping (see 6.4) either explicitly or as a result of a specification according to 6.4.2.

3.6Losses and no-load current

NOTEThe values are related to the principal tapping (see 3.5.2), unless another tapping is specifically stated.

3.6.1

no-load loss

the active power absorbed when a rated voltage (tapping voltage) at a rated frequency is applied to the terminals of one of the windings, the other winding or windings being open-circuited

[SOURCE: IEC 60050‑421:1990, 421‑06‑01

modified

]

3.6.2

no-load current

the r.m.s. value of the current flowing through a line terminal of a winding when rated voltage (tapping voltage) is applied at a rated frequency to that winding, the other winding or windings being open-circuited

Note 1 to entry: For a three-phase transformer, the value is the arithmetic mean of the values of current in the three lines.

Note 2 to entry: The no-load current of a winding is often expressed as a percentage of the rated current of that winding. For a multi-winding transformer, this percentage is referred to the winding with the highest rated power.

[SOURCE: IEC 60050‑421:1990, 421‑06‑02

modified

]

3.6.3

load loss

the absorbed active power at a rated frequency and reference temperature (see 11.1), associated with a pair of windings when rated current (tapping current) is flowing through the line terminals of one of the windings, and the terminals of the other winding are short-circuited. Further windings, if existing, are open-circuited

Note 1 to entry: For a two-winding transformer, there is only one winding combination and one value of load loss. For a multi-winding transformer, there are several values of load loss corresponding to the different two-winding combinations (see Clause 7 of IEC 60076‑8:1997). A combined load loss figure for the complete transformer is referred to a specified winding load combination. In general, it is usually not accessible for direct measurement in testing.

Note 2 to entry: When the windings of the pair have different rated power values, the load loss is referred to rated current in the winding with the lower rated power and the reference power should be mentioned.

3.6.4

total losses

the sum of the no-load loss and the load loss

Note 1 to entry: The power consumption of the auxiliary plant is not included in the total losses and is stated separately.

[SOURCE: IEC 60050‑421:1990, 421‑06‑05

modified

]

3.7Short-circuit impedance and voltage drop

3.7.1

short-circuit impedance of a pair of windings

the equivalent series impedance

Z = R + j X

, in ohms, at rated frequency and reference temperature, across the terminals of one winding of a pair, when the terminals of the other winding are short-circuited and further windings, if existing, are open-circuited: for a three-phase transformer the impedance is expressed as phase impedance (equivalent star connection)

Note 1 to entry: In a transformer having a tapped winding, the short-circuit impedance is referred to a particular tapping. Unless otherwise specified, the principal tapping applies.

Note 2 to entry: This quantity can be expressed in relative, dimensionless form, as a fraction z of the reference impedance Zref, of the same winding of the pair. In percentage notation:

z = 100 \frac{Z}{Z_{ref}}

where

$Z_{ref} = \frac{U^{2}}{S_{r}}$	(formula valid for both three-phase and single-phase transformers);
U	is the voltage (rated voltage or tapping voltage) of the winding to which Z and Zref belong;
Sr	is the reference value of rated power.

The relative value is also equal to the ratio between the applied voltage during a short-circuit measurement which causes the relevant rated current (or tapping current) to flow, and rated voltage (or tapping voltage). This applied voltage is referred to as the short-circuit voltage (IEC 60050‑421:1990, 421‑07‑01) of the pair of windings. It is normally expressed as a percentage.

[SOURCE: IEC 60050‑421:1990, 421‑07‑02

modified

]

3.7.2

voltage drop or rise for a specified load condition

the arithmetic difference between the no-load voltage of a winding and the voltage developed at the terminals of the same winding at a specified load and power factor, the voltage supplied to (one of) the other winding(s) being equal to:

–

its rated value if the transformer is connected on the principal tapping (the no-load voltage of the winding is then equal to its rated value);

–

the tapping voltage if the transformer is connected on another tapping.

This difference is generally expressed as a percentage of the no-load voltage of the winding

Note 1 to entry: For multi-winding transformers, the voltage drop or rise depends not only on the load and power factor of the winding itself, but also on the load and power factor of the other windings (see IEC 60076‑8).

[SOURCE: IEC 60050‑421:1990, 421‑07‑03]

3.7.3

zero-sequence impedance (of a three-phase winding)

the impedance, expressed in ohms per phase at rated frequency, between the line terminals of a three-phase star-connected or zigzag-connected winding, connected together, and its neutral terminal

[SOURCE: IEC 60050‑421:1990, 421‑07‑04

modified

]

Note 1 to entry: The zero-sequence impedance may have several values because it depends on how the terminals of the other winding or windings are connected and loaded.

Note 2 to entry: The zero-sequence impedance may be dependent on the value of the current and the temperature, particularly in transformers without any delta-connected winding.

Note 3 to entry: The zero-sequence impedance may also be expressed as a relative value in the same way as the (positive sequence) short-circuit impedance (see 3.7.1).

3.8

Temperature rise

The difference between the temperature of the part under consideration and the temperature of the external cooling medium (see IEC 60076‑2)

[SOURCE: IEC 60050‑421:1990, 421‑08‑01

modified

]

3.9Insulation

For terms and definitions relating to insulation, see IEC 60076‑3.

3.10Connections

3.10.1

star connection

the winding connection so arranged that each of the phase windings of a three-phase transformer, or of each of the windings for the same rated voltage of single-phase transformers associated in a three-phase bank, is connected to a common point (the neutral point) and the other end to its appropriate line terminal

[SOURCE: IEC 60050‑421:1990, 421‑10‑01

modified

]

Note 1 to entry: Star connection is sometimes referred to as Y-connection.

3.10.2

delta connection

the winding connection so arranged that the phase windings of a three-phase transformer, or the windings for the same rated voltage of single-phase transformers associated in a three-phase bank, are connected in series to form a closed circuit

[SOURCE: IEC 60050‑421:1990, 421‑10‑02

modified

]

Note 1 to entry: Delta connection is sometimes referred to as D-connection.

3.10.3

open-delta connection

the winding connection in which the phase windings of a three-phase transformer, or the windings for the same rated voltage of single-phase transformers associated in a three-phase bank, are connected in series without closing one corner of the delta

[SOURCE: IEC 60050‑421:1990, 421‑10‑03]

3.10.4

zigzag connection

Z-connection

a winding connection consisting of two winding sections, the first section connected in star, the second connected in series between the first section and the line terminals: the two sections are arranged so that each phase of the second section is wound on a different limb of the transformer to the part of the first section to which it is connected

Note 1 to entry: See Annex D for cases where the winding sections have equal voltages.

3.10.5

open windings

the phase windings of a three-phase transformer which are not interconnected within the transformer

[SOURCE: IEC 60050‑421:1990, 421‑10‑05

modified

]

3.10.6

phase displacement (of a three-phase winding)

the angular difference between the phasors representing the voltages between the neutral point (real or imaginary) and the corresponding terminals of two windings, a positive-sequence voltage system being applied to the high-voltage terminals, following each other in alphabetical sequence if they are lettered, or in numerical sequence if they are numbered: the phasors are assumed to rotate in a counter-clockwise sense

[SOURCE: IEC 60050‑421:1990, 421‑10‑08

modified

]

Note 1 to entry: See Clause 7 and Annex D.

Note 2 to entry: The high-voltage winding phasor is taken as reference, and the displacement for any other winding is conventionally expressed by the 'clock notation', that is, the hour indicated by the winding phasor when the H.V. winding phasor is at 12 o'clock (rising numbers indicate increasing phase lag).

3.10.7

connection symbol

a conventional notation indicating the connections of the high-voltage, intermediate-voltage (if any), and low-voltage windings and their relative phase displacement(s) expressed as a combination of letters and clock-hour figure(s)

[SOURCE: IEC 60050‑421:1990, 421‑10‑09

modified

]

3.11Test classification

3.11.1

routine test

a test to which each individual transformer is subjected

3.11.2

type test

a test made on a transformer which is representative of other transformers, to demonstrate that these transformers comply with the specified requirements not covered by the routine tests: a transformer is considered to be representative of others if it is built to the same drawings using the same techniques and materials in the same factory

Note 1 to entry: Design variations that are clearly irrelevant to a particular type test would not require that type test to be repeated.

Note 2 to entry: Design variations that cause a reduction in values and stresses relevant to a particular type test do not require a new type test if accepted by the purchaser and the manufacturer.

Note 3 to entry: For transformers below 20 MVA and Um ≤ 72,5 kV significant design variations may be acceptable if supported by demonstration of compliance with type test requirements.

3.11.3

special test

a test other than a type test or a routine test, agreed by the manufacturer and the purchaser

Note 1 to entry: Special tests can be carried out on one transformer or all transformers of a particular design, as specified by the purchaser in the enquiry and order for every special test.

3.12Meteorological data with respect to cooling

3.12.1

temperature of cooling medium at any time

the maximum temperature of the cooling medium measured over many years

3.12.2

monthly average temperature

half the sum of the average of the daily maxima and the average of the daily minima during a particular month over many years

3.12.3

yearly average temperature

one-twelfth of the sum of the monthly average temperatures

30mm

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– –

Gulf StandardGSO IEC 60076-1:2014

GSO IEC 60076-1:2014Gulf Standard

Bibliography

IEC 60050‑421:1990, International Electrotechnical Vocabulary – Chapter 421: Power transformers and reactors

IEC 60060 (all parts), High-voltage test techniques

IEC 60068‑3‑3, Environmental testing – Part 3: Guidance – Seismic test methods for equipments

IEC 60076‑4, Power transformers – Part 4: Guide to lightning impulse and switching impulse testing – Power transformers and reactors

IEC 60076‑6, Power transformers – Part 6: Reactors

IEC 60076‑7, Power transformers – Part 7: Loading guide for oil-immersed power transformers

IEC 60076‑8:1997, Power transformers – Part 8: Application guide

IEC 60076‑10‑1, Power transformers – Part 10-1: Determination of sound levels – Application guide

IEC 60076‑12, Power transformers – Part 12: Loading guide for dry-type power transformers

IEC 60076‑13, Power transformers – Part 13: Self-protected liquid-filled transformers

IEC/TS 60076-14, Power transformers – Part 14: Design and application of liquid-immersed power transformers using high-temperature insulation materials

IEC 60076‑15: 2008, Power transformers – Part 15: Gas-filled power transformers

IEC 60076‑16, Power transformers – Part 16 : Transformers for wind turbines application1

IEC 60270, High voltage test techniques – Partial discharge measurements

IEC 60310, Railway applications – Traction transformers and inductors on board rolling stock

IEC 60529:1989, Degrees of protection provided by enclosures (IP Code)

IEC/TR 60616:1978, Terminal and tapping markings for power transformers

IEC/TS 60815 (all parts), Selection and dimensioning of high-voltage insulators intended for use in polluted conditions

IEC 61378 (all parts), Convertor transformers

IEC 61378‑1, Convertor transformers – Part 1: Transformers for industrial applications

IEC 61378‑2, Convertor transformers – Part 2: Transformers for HVDC applications

IEC 62032, Guide for the application, specification, and testing of phase-shifting transformers

IEC 62262, Degrees of protection provided by enclosures for electrical equipment against external mechanical impact (IK code)

ISO 3:1973, Preferred numbers – Series of preferred numbers

ISO 2178:1982, Non-magnetic coatings on magnetic substrates – Measurement of coating thickness – Magnetic method

ISO 2409:2007, Paints and varnishes – Cross-cut test

ISO 12944 (all parts), Paints and varnishes – Corrosion protection of steel structures by protective paint systems

ISO 14001, Environmental management systems – Specification with guidance for use

ISO 14122 (all parts), Safety of machinery – Permanent means of access to machinery

ANSI/IEEE C57.12.00, General requirements for liquid-immersed distribution, power and regulating transformers

ANSI/IEEE C57.12.90, IEEE standard test code for liquid-immersed distribution, power and regulating transformers

IEEE C57.142, Guide to describe the occurrence and mitigation of switching transients induced by transformer, switching device, and system interaction

CIGRE Brochure 156, Guide for customers specifications for transformers 100 MVA and 123 kV and above

CIGRE Brochure 204, Guide for transformer design review

CIGRE Brochure 343, Recommendations for Condition Monitoring and Condition Assessment Facilities for Transformers

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INTERNATIONALELECTROTECHNICALCOMMISSION3, rue de VarembéPO Box 131CH-1211 Geneva 20SwitzerlandTel: +41 22 919 02 11 info@iec.ch www.iec.ch

*The winding which receives active power from the supply source in service is referred to as a 'primary winding', and that which delivers active power to a load as a 'secondary winding'. These terms have no significance as to which of the windings has the higher rated voltage and should not be used except in the context of direction of active power flow (see IEC 60050‑421:1990, 421‑03‑06 and 07). A further winding in the transformer, usually with lower value of rated power than the secondary winding, is then often referred to as 'tertiary winding', see also definition 3.3.8.

1To be published