Bsi bs en 50588 1 2015 + a1 2016

If additional cooling system such as fans or pumps… are used only for temporary overload conditions and not for continuous rating, then such overloading rating cannot be claimed to be as

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Medium power transformers

50 Hz, with highest voltage for equipment not exceeding 36 kV

Part 1: General requirements BSI Standards Publication

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NORME EUROPÉENNE

English VersionMedium power transformers 50 Hz, with highest voltage for equipment not exceeding 36 kV - Part 1: General requirements

Transformateurs 50 Hz de moyenne puissance, de tension

la plus élevée pour le matériel ne dépassant pas 36 kV

-Partie 1: Exigences générales

Mittelleistungstransformatoren 50 Hz, mit einer höchsten Spannung für Betriebsmittel nicht über 36 kV - Teil 1:

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

European Committee for Electrotechnical StandardizationComité Européen de Normalisation ElectrotechniqueEuropäisches Komitee für Elektrotechnische Normung

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

National foreword

This British Standard is the UK implementation of EN50588-1:2015+A1:2016 It supersedes BS EN 50464-1:2007+A1:

2012 and BS EN 50541-1:2011 which arewithdrawn

BSI, as a member of CENELEC, is obliged to publish

EN 50588-1:2015+A1:2016 as a British Standard However, attention

is drawn to the fact that during the development of this EuropeanStandard the UK committee voted against its approval as a Europeanstandard The UK committee submitted a negative vote for thefollowing reasons:

a) This standard is not applicable to transformers for tram systems, whichhave the same, or similar, operating characteristics to railways The UKcommittee is of the opinion that the relevant exclusion in clause 1 shouldread ‘transformers and auto-transformers specifically designed for railwayand other traction feeding systems’

b) The UK committee advises that the de-energised tapping range forsingle-phase liquid immersed transformers with Sr ≤ 100 kVA should be ≤7,5 % as this is the limit for pad-mounted transformers in the

United Kingdom

The start and finish of text introduced or altered by amendment isindicated in the text by tags Tags indicating changes to CEN text carrythe number of the CEN amendment For example, text altered by CENamendment A1 is indicated by 

The UK participation in its preparation was entrusted to TechnicalCommittee PEL/14, Power Transformers

A list of organizations represented on this committee can be obtained onrequest to its secretary

This publication does not purport to include all the necessary provisions of

a contract Users are responsible for its correct application

Published by BSI Standards Limited 2017ISBN 978 0 580 97536 3

Amendments/corrigenda issued since publication

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NORME EUROPÉENNE

English Version Medium power transformers 50 Hz, with highest voltage for equipment not exceeding 36 kV - Part 1: General requirements

Transformateurs 50 Hz de moyenne puissance, de tension

la plus élevée pour le matériel ne dépassant pas 36 kV -

Partie 1: Exigences générales

Mittelleistungstransformatoren 50 Hz, mit einer höchsten Spannung für Betriebsmittel nicht über 36 kV - Teil 1:

Allgemeine Anforderungen

This European Standard was approved by CENELEC on 2015-06-25 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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management Centre has the

same status as the official versions

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom

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

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

Ref No EN 50588-1:2015 E

June 2015

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5�1 Highest voltages for equipment for winding with Um > 1,1 kV �� 9

5�2 Rated voltage for winding with Um ≤ 1,1 kV �� 9 5�3 Tapping �� 95�4 Connection designations for three phase transformers �� 9

6 Load loss, no load loss, PEI, sound power level, short-circuit impedance �� 10 6�1 General �� 10

6�2 Transformers with rated power Sr ≤ 3 150 kVA �� 116�2�1 General information �� 11

6�2�2 One winding with Um ≤ 24 kV and the other one with Um ≤ 1,1 kV �� 126�2�3 Load loss and no load loss in case of other insulation level �� 146�2�4 Load loss and no load loss in case of dual voltage �� 146�2�5 Three winding transformers for PV applications �� 15

6.3 Transformers with rated power 3 150 kVA < Sr < 40 000 kVA �� 156�4 Transformers with special requirements �� 176�4�1 Rated power not included in the list �� 176�4�2 Transformers equipped with tapping connections suitable for

operation while transformer is energised or on load and rated

power Sr ≤ 3 150 kVA �� 176�4�3 Liquid immersed pole mounted transformers �� 186�4�4 PEI values for single-phase liquid immersed transformers with

Sr ≤ 100 kVA �� 19

7 Tolerances �� 197�1 Tolerances during factory acceptance tests �� 19 7�1�1 General �� 19

7�1�2 Transformers subject to maximum losses �� 197�1�3 Transformers subject to minimum PEI �� 197�2 Tolerances for Market surveillance �� 197.2.1 Acceptance criteria �� 197�2�2 Transformers subjected to max losses �� 207�2�3 Transformers subjected to PEI �� 207�3 Uncertainties for market surveillance verification �� 20

8 Rating plate �� 21

9 Tests �� 219�1 Routine tests �� 219�2 Type tests �� 219�3 Special tests �� 219�4 Special test for corrugated tank �� 219�4�1 General information �� 219�4�2 Temperature variation �� 22

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9�4�3 Sealing temperature �� 229�4�4 Calculation of the volume variation �� 229�4�5 Test procedure �� 229.5 Other technologies with level of no load loss AAA0 �� 23

10 Design requirements �� 2310�1 Liquid immersed transformers �� 2310�1�1 Type of liquid preservation system and degree of sealing �� 2310�1�2 Terminal markings�� 23 10�1�3 Terminations �� 24

10�1�4 Distance between bushings �� 24 10�1�5 Rollers �� 2410�2 Dry-type transformers �� 24 10�2�1 Terminals �� 24 10�2�2 Enclosure �� 24

11 Accessories �� 2511�1 Liquid immersed transformers �� 2511�2 Dry-type transformers �� 25Annex A (informative) Calculation of PEI and kPEI �� 27A.1 Calculation of Peak Efficiency Index �� 27A.2 Calculation of kPEI �� 27Ann ex ZZ (informative) Relationship between this European Standard and the

requirements of Commission Regulation (EC) No 548/2014 of 21 May 2014 on

implementing Directive 2009/125/EC of the European Parliament and of the Council with regard to small, medium and large power transformers �� 29Bibliography �� 32

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Foreword

This document (EN 50588-1:2015) has been prepared by CLC/TC 14 "Power transformers"

The following dates are fixed:

- latest date by which this document has

to be implemented at national level by

publication of an identical national

standard or by endorsement

(dop) 2016-06-25

- latest date by which the national

standards conflicting with this

document have to be withdrawn

(dow) 2018-06-25

This document supersedes EN 50464-1:2007 and EN 50541-1:2011

EN 50588-1:2015 includes the following significant technical changes with respect to

EN 50464-1:2007 and EN 50541-1:2011:

- both liquid filled and dry-type transformers are covered in the same document;

- the scope of applicability is extended in terms of rated power;

- new values of no load loss, load loss and sound power level for different values of rated

power are specified;

- for transformers having rated power above 3 150 kVA, the concept of Peak Efficiency Index

is introduced

Attention is drawn to the possibility that some of the elements of this document may be the subject

of patent rights CENELEC [and/or CEN] shall not be held responsible for identifying any or all such

patent rights

This document has been prepared under a mandate given to CENELEC by the European

Commission and the European Free Trade Association, and supports requirements of Commission

Regulation (EC)

For the relationship with requirements of Commission Regulation (EC) see informative Annex ZZ,

which is an integral part of this document

5

1 Scope

This European Standard covers medium power transformers ‘Medium power transformer’ means apower transformer with a highest voltage for equipment higher than 1,1 kV, but not exceeding 36 kV and a rated power equal to or higher than 5 kVA but lower than 40 MVA

National practices may require the use of highest voltages for equipment up to (but not including)

52 kV, when the rated voltage is less than 36 kV (such as Um= 38,5 kV or Um= 40,5 kV) This isconsidered to be an unusual case of a large power transformer, where the requirements are those

for a medium power transformer with Um= 36 kV

NOTE 1 ‘Large power transformer’ means a power transformer with a highest voltage for equipmentexceeding 36 kV and a rated power equal or higher than 5 kVA, or a rated power equal to or higher than

40 MVA regardless of the highest voltage for equipment Large power transformers are in the scope of

The following transformers are excluded from this European Standard:

- instrument transformers, specifically designed to supply measuring instruments, meters,relays and other similar apparatus;

- transformers with low-voltage windings specifically designed for use with rectifiers to provide a DC supply;

- transformers specifically designed to be directly connected to a furnace;

- transformers specifically designed for offshore applications and floating offshore applications;

- transformers specially designed for emergency installations;

- transformers and auto-transformers specifically designed for railway feeding systems;

- earthing or grounding transformers, this is, three-phase transformers intended to provide aneutral point for system grounding purposes;

- traction transformers mounted on rolling stock, this is, transformers connected to an AC or

DC contact line, directly or through a converter, used in fixed installations of railwayapplications;

- starting transformers, specifically designed for starting three-phase induction motors so as

to eliminate supply voltage dips;

- testing transformers, specifically designed to be used in a circuit to produce a specificvoltage or current for the purpose of testing electrical equipment;

- welding transformers, specifically designed for use in arc welding equipment or resistance welding equipment;

- transformers specifically designed for explosion-proof and underground mining applications,

- transformers specifically designed for deep water (submerged) applications;

- medium Voltage (MV) to Medium Voltage (MV) interface transformers up to 5 MVA;

- large power transformers where it is demonstrated that for a particular application,technically feasible alternatives are not available to meet the minimum efficiencyrequirements set out by the commission regulation (EU) No 548/2014;

- large power transformers which are like for like replacements in the same physicallocation/installation for existing large power transformers, where this replacement cannot be achieved without entailing disproportionate costs associated to their transportation and/orinstallation

4

Foreword to amendment A1

This document (EN 50588-1:2015/A1:2016) has been prepared by CLC/TC 14 "Power transformers"

- latest date by which this document has to be

implemented at national level by publication of

an identical national standard or by

endorsement

(dop) 2017-05-23

- latest date by which the national standards

conflicting with this document have to

be withdrawn

(dow) 2019-05-23

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent rights

This document has been prepared under a mandate given to CENELEC by the European Commission and

the European Free Trade Association, and supports requirements of Commission Regulation (EU)

For the relationship with Commission Regulation (EU) see informative Annex ZZ, which is an integral part of

EN 50588-1:2015

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4

Foreword

This document (EN 50588-1:2015) has been prepared by CLC/TC 14 "Power transformers"

- latest date by which this document has

to be implemented at national level by

publication of an identical national

standard or by endorsement

(dop) 2016-06-25

- latest date by which the national

standards conflicting with this

document have to be withdrawn

(dow) 2018-06-25

This document supersedes EN 50464-1:2007 and EN 50541-1:2011

EN 50588-1:2015 includes the following significant technical changes with respect to

EN 50464-1:2007 and EN 50541-1:2011:

- both liquid filled and dry-type transformers are covered in the same document;

- the scope of applicability is extended in terms of rated power;

- new values of no load loss, load loss and sound power level for different values of rated

power are specified;

- for transformers having rated power above 3 150 kVA, the concept of Peak Efficiency Index

is introduced

Attention is drawn to the possibility that some of the elements of this document may be the subject

of patent rights CENELEC [and/or CEN] shall not be held responsible for identifying any or all such

patent rights

This document has been prepared under a mandate given to CENELEC by the European

Commission and the European Free Trade Association, and supports requirements of Commission

Regulation (EC)

For the relationship with requirements of Commission Regulation (EC) see informative Annex ZZ,

which is an integral part of this document

5

1 Scope

This European Standard covers medium power transformers ‘Medium power transformer’ means a power transformer with a highest voltage for equipment higher than 1,1 kV, but not exceeding 36 kV and a rated power equal to or higher than 5 kVA but lower than 40 MVA

National practices may require the use of highest voltages for equipment up to (but not including)

52 kV, when the rated voltage is less than 36 kV (such as Um = 38,5 kV or Um = 40,5 kV) This is considered to be an unusual case of a large power transformer, where the requirements are those

for a medium power transformer with Um = 36 kV

NOTE 1 ‘Large power transformer’ means a power transformer with a highest voltage for equipment exceeding 36 kV and a rated power equal or higher than 5 kVA, or a rated power equal to or higher than

40 MVA regardless of the highest voltage for equipment Large power transformers are in the scope of

The following transformers are excluded from this European Standard:

- instrument transformers, specifically designed to supply measuring instruments, meters, relays and other similar apparatus;

- transformers with low-voltage windings specifically designed for use with rectifiers to provide a DC supply;

- transformers specifically designed to be directly connected to a furnace;

- transformers specifically designed for offshore applications and floating offshore applications;

- transformers specially designed for emergency installations;

- transformers and auto-transformers specifically designed for railway feeding systems;

- earthing or grounding transformers, this is, three-phase transformers intended to provide a neutral point for system grounding purposes;

- traction transformers mounted on rolling stock, this is, transformers connected to an AC or

DC contact line, directly or through a converter, used in fixed installations of railway applications;

- starting transformers, specifically designed for starting three-phase induction motors so as

to eliminate supply voltage dips;

- testing transformers, specifically designed to be used in a circuit to produce a specific voltage or current for the purpose of testing electrical equipment;

- welding transformers, specifically designed for use in arc welding equipment or resistance welding equipment;

- transformers specifically designed for explosion-proof and underground mining applications,

- transformers specifically designed for deep water (submerged) applications;

- medium Voltage (MV) to Medium Voltage (MV) interface transformers up to 5 MVA;

- large power transformers where it is demonstrated that for a particular application, technically feasible alternatives are not available to meet the minimum efficiency requirements set out by the commission regulation (EU) No 548/2014;

- large power transformers which are like for like replacements in the same physical location/installation for existing large power transformers, where this replacement cannot be achieved without entailing disproportionate costs associated to their transportation and/or installation

5

In case one of the last two exclusions is claimed, this should be documented at the signature of the contract with a declaration made by the customer�



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6

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies

EN 50180 Bushings above 1 kV up to 52 kV and from 250 A to 3,15 kA for liquid

filled transformers — Part 1: General requirements for bushings

EN 50181 Plug-in type bushings above 1 kV up to 52 kV and from 250 A to 2,50 kA

for equipment other than liquid filled transformers

EN 50216 (all parts) Power transformer and reactor fittings

EN 50386 Bushings up to 1 kV and from 250 A to 5 kA, for liquid filled transformers

EN 50387 Busbar bushings up to 1 kV and from 1,25 kA to 5 kA, for liquid filled

transformers

EN 50464-4 Three-phase oil-immersed distribution transformers 50 Hz, from 50 kVA to

2 500 kVA with highest voltage for equipment not exceeding 36 kV — Part 4: Requirements and tests concerning pressurised corrugated tanks

EN 60076 (all parts) Power transformers (IEC 60076, all parts)

EN 60076-19 Power transformers — Part 19: Rules for the determination of

uncertainties in the measurement of the losses on power transformers and reactors (IEC/TS 60076-19)

EN 60085 Electrical insulation — Thermal evaluation and designation

EN 60505 Evaluation and qualification of electrical insulation systems (IEC 60505)

EN 61100 Classification of insulating liquids according to fire point and net calorific

value (IEC 61100)

IEC/TR 60616 Terminal and tapping markings for power transformers

3 Terms and definitions

For the purposes of this document, the terms and definitions given in EN 60076-1:2011 and the following apply

3.1 load factor

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application For dated references, only the edition cited applies For undated

references, the latest edition of the referenced document (including any amendments) applies

transformers

value (IEC 61100)

For the purposes of this document, the terms and definitions given in EN 60076-1:2011 and the

following apply

3.1

load factor

k

ratio of actual input current over the rated current of transformer where the actual current and rated

current are constant over time

Note 1 to entry: Normally 0 ≤ k ≤ 1

EI

ratio of the transmitted apparent power of a transformer minus electrical losses to the transmitted apparent power of the transformer

3.4 Peak Efficiency Index PEI

highest value of efficiency index that can be achieved at the optimum value of load factor Note 1 to entry: See Annex A for derivation

3.5 load factor of Peak Efficiency Index

k PEI

load factor at which Peak Efficiency Index occurs Note 1 to entry: See Annex A for derivation

3.6 declared value

regulatory value given in Clause 6 which is to be used for market surveillance activities Note 1 to entry: Declared values and guaranteed values according to EN 60076-1 are two different concepts Guaranteed values are related to contract, whereas declared values are related to compliance verifications with COMMISSION REGULATION (EU) No 548/2014

5.1 Highest voltages for equipment for winding with Um > 1,1 kV

Insulation levels and dielectric test shall be in accordance with the requirements of EN 60076-3

The values of the highest voltage Um for equipment are:

3,6 kV– 7,2 kV – 12 kV – 17,5 kV – 24 kV – 36 kV

NOTE National practices may require the use of highest voltages for equipment up to (but not including) 52 kV, when the

rated voltage is less than 36 kV (such as Um = 38,5 kV or Um = 40,5 kV)

5.2 Rated voltage for winding with Um ≤ 1,1 kV

For Um ≤ 1,1 kV the preferred rated voltage value shall be chosen in the hereunder list:

400 V – 410 V – 415 V – 420 V – 433 V – 690 V NOTE This document may be applied either as a whole or in part, to transformers with rated low voltages below 400 V and above 690 V

BS EN 50588-1:2015+A1:2016

EN 50588-1:2015+A1:2016

6

NOTE 3 This standard covers the transformers under the Commission Regulation (EU) No 548/2014 and

gives additional specific guidance for single phase transformers, multi winding transformers and for transformers

with OF or OD cooling systems, necessary for the correct application of energy efficiency requirements to these

categories of transformers�



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6

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies

transformers

value (IEC 61100)

For the purposes of this document, the terms and definitions given in EN 60076-1:2011 and the following apply

highest value of efficiency index that can be achieved at the optimum value of load factor

Note 1 to entry: See Annex A for derivation

3.5

load factor of Peak Efficiency Index

k PEI

load factor at which Peak Efficiency Index occurs

3.6

declared value

regulatory value given in Clause 6 which is to be used for market surveillance activities

Note 1 to entry: Declared values and guaranteed values according to EN 60076-1 are two different concepts Guaranteed values are related to contract, whereas declared values are related to compliance verifications with COMMISSION REGULATION (EU) No 548/2014

3,6 kV– 7,2 kV – 12 kV – 17,5 kV – 24 kV – 36 kV

Note 2 to entry: The term “low-voltage winding” refers to the winding having the lowest rated voltage as per

EN 60076-1, whatever its voltage level�

Note 3 to entry: This definition does not include:

- transformers which are intended to provide AC from DC sources such as transformers for wind turbine and photo voltaic applications;

- transformers designed for DC transmission and distribution applications�



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7

3.3 Efficiency Index

EI

k PEI

3,6 kV– 7,2 kV – 12 kV – 17,5 kV – 24 kV – 36 kV

ratio of the transmitted apparent power of a transformer minus electrical losses to the transmitted

apparent power of the transformer

3.4

Peak Efficiency Index

PEI

3.5

k PEI

3.6

declared value

Note 1 to entry: Declared values and guaranteed values according to EN 60076-1 are two different concepts

Guaranteed values are related to contract, whereas declared values are related to compliance verifications with

COMMISSION REGULATION (EU) No 548/2014

4 Environmental classes

Classification of insulating liquids according to fire point and net calorific value is given in EN 61100

Climatic, environmental and fire behaviour classes for dry–type transformers are defined in

EN 60076-11

5 Electrical characteristics

3,6 kV– 7,2 kV – 12 kV – 17,5 kV – 24 kV – 36 kV

400 V – 410 V – 415 V – 420 V – 433 V – 690 V NOTE This document may be applied either as a whole or in part, to transformers with rated low voltages

below 400 V and above 690 V

BS EN 50588-1:2015 EN 50588-1:2015 (E)

8

The values for short duration power frequency withstand and/or for the lightning impulse withstand test between windings and earth need to be stated by the purchaser The most usual values are respectively 10 kV and 30 kV

5.3 Tapping

Taps can be provided with DETC or OLTC devices:

- DETC: De-energised tap changer

- OLTC: On load tap changer For DETC the preferred tapping ranges are ± 2,5 % with 3 tap positions and ± 2 x 2,5 % with 5 tap positions On special request ± 4 x 2,5 % with 9 tap positions can be provided Tapping ranges greater than ± 10 % or with more than 9 tap positions are unusual and subject to specific agreement

For transformer equipped with OLTC the tapping range shall be smaller than ± 15 % with a maximum of 17 tap positions Tapping ranges greater than ± 15 % or with more than 17 tap positions are unusual and subject to specific agreement

Tapping ranges outside the above definitions have to be specified by agreement between manufacturer and purchaser

5.4 Connection designations for three phase transformers

Preferred connection designations, following IEV [421-10-09], shall be in accordance with the provisions of Table 1

Table 1 — Connections

Sr ≤ 100 kVA 100 kVA < Sr < 5 000 kVA Sr ≥ 5 000 kVA Yzn or Dyn Dyn YNd or Dyn or YNyn

The clock hour figure should be 5 or 11 for Dyn or Yzn and 0 for Yy

Connections and clock hour figure shall be specified by the purchaser preferably amongst the choice given above

6 Load loss, no load loss, PEI, sound power level, short-circuit impedance

6.1 General

The following tables give the maximum level of losses for single phase transformers with a rated

power Sr ≤ 100kVA, for three phase transformers with a rated power Sr ≤ 3 150 kVA and minimum

Peak Efficiency Index for three phase transformers with rated power Sr > 3 150 kVA and

Sr < 40 000 kVA

The losses and Peak Efficiency Index classes remain the same for all highest voltage for equipment

values (Um) regardless of the additional loss corrections specified in 6.2.3 and 6.2.4

Description and requirements for special cases are given in 6.4

transformer to be installed on fixed or floating offshore platforms, offshore wind turbines or on board

of ships and all kind of vessels

3.7.4

transformers specially designed for emergency installations

transformer designed only to provide cover for a specific time limited situation when the normal power

supply is interrupted either due to an unplanned occurrence such as failure or a station refurbishment,

but not to permanently upgrade an existing substation

Note 1 to entry: Such transformer could have some specific features that make it suitable for emergency or

temporary use as opposed to normal use� Example of some specific features:

- multiple windings making it suitable for use at several locations;

- special low weight or dimensions for easy transport, or special capability to be disassembled into smaller units

for transport;

- increased overload capability achieved by the use of special materials;

- permanent mounting on a transporter arrangement�

3.7.5

transformers and auto-transformers specifically designed for railway feeding systems

transformer as defined in EN 50329

3.7.6

earthing or grounding transformers, this is, three-phase transformers intended to provide a

neutral point for system grounding purposes

transformer as defined in paragraph 3�1�10 of EN 60076-6:2008

3.7.7

traction transformer

transformer installed on board of rolling stock inserted in the traction and auxiliary circuits of rolling

stock and in the scope of EN 60310

3.7.8

starting transformers, specifically designed for starting three-phase induction motors so as

to eliminate supply voltage dips

transformer that is de energized during normal operation, used for the purpose of starting a rotating

machine

3.7.9

Medium Voltage (MV) to Medium Voltage (MV) interface transformers up to 5 MVA

transformer used in network voltage conversion program and placed at the junction between two

voltage levels of two MV networks and which needs to be able to cope with emergency overloads

Note 1 to entry: Such units may or maybe not part of a packaged compact substation including also MV

Reclosers and protection equipment�



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7

3.3 Efficiency Index

EI

k PEI

3,6 kV– 7,2 kV – 12 kV – 17,5 kV – 24 kV – 36 kV

ratio of the transmitted apparent power of a transformer minus electrical losses to the transmitted

apparent power of the transformer

3.4

Peak Efficiency Index

PEI

3.5

k PEI

3.6

declared value

Note 1 to entry: Declared values and guaranteed values according to EN 60076-1 are two different concepts

Guaranteed values are related to contract, whereas declared values are related to compliance verifications with

COMMISSION REGULATION (EU) No 548/2014

4 Environmental classes

Classification of insulating liquids according to fire point and net calorific value is given in EN 61100

Climatic, environmental and fire behaviour classes for dry–type transformers are defined in

EN 60076-11

5 Electrical characteristics

3,6 kV– 7,2 kV – 12 kV – 17,5 kV – 24 kV – 36 kV

400 V – 410 V – 415 V – 420 V – 433 V – 690 V NOTE This document may be applied either as a whole or in part, to transformers with rated low voltages

below 400 V and above 690 V

BS EN 50588-1:2015 EN 50588-1:2015 (E)

8

The values for short duration power frequency withstand and/or for the lightning impulse withstand test between windings and earth need to be stated by the purchaser The most usual values are respectively 10 kV and 30 kV

5.3 Tapping

- OLTC: On load tap changer For DETC the preferred tapping ranges are ± 2,5 % with 3 tap positions and ± 2 x 2,5 % with 5 tap positions On special request ± 4 x 2,5 % with 9 tap positions can be provided Tapping ranges greater than ± 10 % or with more than 9 tap positions are unusual and subject to specific agreement

For transformer equipped with OLTC the tapping range shall be smaller than ± 15 % with a maximum of 17 tap positions Tapping ranges greater than ± 15 % or with more than 17 tap positions are unusual and subject to specific agreement

Tapping ranges outside the above definitions have to be specified by agreement between manufacturer and purchaser

Preferred connection designations, following IEV [421-10-09], shall be in accordance with the provisions of Table 1

Connections and clock hour figure shall be specified by the purchaser preferably amongst the choice given above

6.1 General

Sr < 40 000 kVA

BS EN 50588-1:2015+A1:2016

EN 50588-1:2015+A1:2016

9

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BS EN 50588-1:2015 EN 50588-1:2015 (E)

8

The values for short duration power frequency withstand and/or for the lightning impulse withstand

test between windings and earth need to be stated by the purchaser The most usual values are

respectively 10 kV and 30 kV

5.3 Tapping

- OLTC: On load tap changer

For DETC the preferred tapping ranges are ± 2,5 % with 3 tap positions and ± 2 x 2,5 % with 5 tap

positions On special request ± 4 x 2,5 % with 9 tap positions can be provided Tapping ranges

greater than ± 10 % or with more than 9 tap positions are unusual and subject to specific

agreement

For transformer equipped with OLTC the tapping range shall be smaller than ± 15 % with a

maximum of 17 tap positions Tapping ranges greater than ± 15 % or with more than 17 tap

positions are unusual and subject to specific agreement

Tapping ranges outside the above definitions have to be specified by agreement between

manufacturer and purchaser

Preferred connection designations, following IEV [421-10-09], shall be in accordance with the

provisions of Table 1

Connections and clock hour figure shall be specified by the purchaser preferably amongst the

choice given above

6.1 General

power Sr≤ 100kVA, for three phase transformers with a rated power Sr≤ 3 150 kVA and minimum

Sr< 40 000 kVA

The names of the loss classes are the same for all of the highest voltage for equipment values (Um) whatever the corrections done on the values described in the following clauses

Other values of short-circuit impedance can be specified by the purchaser for particular systemservice conditions, e.g in the case of parallel operations in all tables of this clause

The sound power levels, given in the tables in Clause 6 are preferred and maximum values Thesound power levels can be specified by the purchaser or by agreement between manufacturer and purchaser for different values

For liquid immersed transformer and for dry-type transformer, load loss, Peak Efficiency Index and short circuit impedance shall be given at the reference temperature defined in EN 60076-1

To calculate and to compare the Peak Efficiency Index and the load loss of different transformersthe correct reference temperature shall be taken according to their insulation system temperature (see EN 60076-1:2011, 11.1.1)

The insulation materials used in transformer shall have an insulation system temperature according

to EN 60085 and EN 60505 and in compliance with the temperature rise limits for the transformeraccording to EN 60076-2, EN 60076-11 and EN 60076-14

The symbols used are:

P0: no load loss at rated voltage and rated frequency, on the rated tap according to EN 60076-1;

Pk: load loss at rated current and rated frequency on the rated tap corrected to referencetemperature according to EN 60076-1;

LWA: A weighted sound power level of transformers according to EN 60076-10

6.2 Transformers with rated power Sr≤ 3 150 kVA

6.2.1 General information

Figure 1 indicates clauses to be chosen according to the highest voltage for equipment values Um

on the primary and on the secondary windings

Figure 1 — Choice of clauses according to the highest voltage for equipment values Um

Numbering into brackets are the references to the lines of Table 5

8

5.3 Tapping

agreement

choice given above

6.1 General

Sr < 40 000 kVA

BS EN 50588-1:2015

EN 50588-1:2015 (E)

9

Several classes of losses are defined in this standard with a ranking of efficiency for no load loss

and for load loss The most efficient class for no load loss is class AAA0, then AA0, then A0 For load

loss the same logic is used with the most efficient class is Ak, then Bk, then Ck

The names of the loss classes are the same for all of the highest voltage for equipment values (Um)

whatever the corrections done on the values described in the following clauses

Other values of short-circuit impedance can be specified by the purchaser for particular system

service conditions, e.g in the case of parallel operations in all tables of this clause

The sound power levels, given in the tables in Clause 6 are preferred and maximum values The

sound power levels can be specified by the purchaser or by agreement between manufacturer and

purchaser for different values

For liquid immersed transformer and for dry-type transformer, load loss, Peak Efficiency Index and

short circuit impedance shall be given at the reference temperature defined in EN 60076-1

To calculate and to compare the Peak Efficiency Index and the load loss of different transformers

the correct reference temperature shall be taken according to their insulation system temperature

(see EN 60076-1:2011, 11.1.1)

to EN 60085 and EN 60505 and in compliance with the temperature rise limits for the transformer

according to EN 60076-2, EN 60076-11 and EN 60076-14

Pk: load loss at rated current and rated frequency on the rated tap corrected to reference

temperature according to EN 60076-1;

BS EN 50588-1:2015

EN 50588-1:2015 (E)

9

(see EN 60076-1:2011, 11.1.1)

Other values of short-circuit impedance can be specified by the purchaser for particular systemservice conditions, e.g in the case of parallel operations in all tables of this clause

The sound power levels, given in the tables in Clause 6 are preferred and maximum values Thesound power levels can be specified by the purchaser or by agreement between manufacturer and purchaser for different values

To calculate and to compare the Peak Efficiency Index and the load loss of different transformersthe correct reference temperature shall be taken according to their insulation system temperature (see EN 60076-1:2011, 11.1.1)

to EN 60085 and EN 60505 and in compliance with the temperature rise limits for the transformeraccording to EN 60076-2, EN 60076-11 and EN 60076-14

Pk: load loss at rated current and rated frequency on the rated tap corrected to referencetemperature according to EN 60076-1;

BS EN 50588-1:2015+A1:2016

EN 50588-1:2015+A1:2016

10

If different values of apparent power are assigned under different circumstances, for example, with

different methods of cooling (ONAN/ONAF, AN/AF, etc…), all values must be reported on the rating

plate and the highest of these values is the rated power� This applies also in case a provision for a

future value of apparent power is made (for example future ONAF, future AF, etc…)

Any evaluation of losses shall be done on continuous rated power as stated in EN 60076-1 If

additional cooling system such as fans or pumps… are used only for temporary overload conditions

and not for continuous rating, then such overloading rating cannot be claimed to be as rated power

and then not mentioned on the rating plate�

values (Um) regardless of the additional loss corrections specified in 6.2.3, 6�2�4 and 6�2�5�

The loss classes correspond to the values measured during the factory acceptance test without

any tolerances�

More specifically:

a) The reference temperature for liquid immersed transformers with rated average winding

temperature rise less than or equal to 65 K for OF or ON, or 70 K for OD is 75 °C;

b) For transformers with other rated average winding temperature rise, the reference temperature

is equal to the rated average winding temperature rise + 20 °C, or rated winding temperature

rise + yearly external cooling medium average temperature, whichever is higher�



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BS EN 50588-1:2015 EN 50588-1:2015 (E)

8

5.3 Tapping

agreement

choice given above

6.1 General

Sr < 40 000 kVA

Other values of short-circuit impedance can be specified by the purchaser for particular system service conditions, e.g in the case of parallel operations in all tables of this clause

The sound power levels, given in the tables in Clause 6 are preferred and maximum values The sound power levels can be specified by the purchaser or by agreement between manufacturer and purchaser for different values

To calculate and to compare the Peak Efficiency Index and the load loss of different transformers the correct reference temperature shall be taken according to their insulation system temperature (see EN 60076-1:2011, 11.1.1)

to EN 60085 and EN 60505 and in compliance with the temperature rise limits for the transformer according to EN 60076-2, EN 60076-11 and EN 60076-14

Pk: load loss at rated current and rated frequency on the rated tap corrected to reference temperature according to EN 60076-1;

6.2 Transformers with rated power Sr ≤ 3 150 kVA

8

5.3 Tapping

agreement

choice given above

6.1 General

Sr < 40 000 kVA

BS EN 50588-1:2015

EN 50588-1:2015 (E)

9

(see EN 60076-1:2011, 11.1.1)

BS EN 50588-1:2015

EN 50588-1:2015 (E)

9

(see EN 60076-1:2011, 11.1.1)

Other values of short-circuit impedance can be specified by the purchaser for particular system service conditions, e.g in the case of parallel operations in all tables of this clause

The sound power levels, given in the tables in Clause 6 are preferred and maximum values The sound power levels can be specified by the purchaser or by agreement between manufacturer and purchaser for different values

To calculate and to compare the Peak Efficiency Index and the load loss of different transformers the correct reference temperature shall be taken according to their insulation system temperature (see EN 60076-1:2011, 11.1.1)

to EN 60085 and EN 60505 and in compliance with the temperature rise limits for the transformer according to EN 60076-2, EN 60076-11 and EN 60076-14

Pk: load loss at rated current and rated frequency on the rated tap corrected to reference temperature according to EN 60076-1;

6.2.2 One winding with Um ≤ 24 kV and the other one with Um ≤ 1,1 kV

The following tables are defined for step down or step up transformer with one winding with

Um ≤ 24 kV and the other one with Um ≤ 1,1 kV

Table 2 and Table 3 are for liquid immersed transformers and Table 4 for dry-type transformers

For the transformers AAA0 see special requirements in 9.5

Table 2 — No load loss (P 0 ) and sound power level for liquid immersed transformers

Rated power AAA 0 AA 0 LWA A 0 LWA

power 3 150 kVA < Sr < 40 000 kVA is given in paragraph 6.3.



If a purchaser needs to compare transformer with different insulation systems and different average winding temperature rises, the reference temperature should be according to b) above 



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Table 3 — Load loss (P k ) and short circuit impedance for liquid immersed transformers

Rated power Ak Bk Ck Short-circuit Impedance

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Table 3 — Load loss (P k ) and short circuit impedance for liquid immersed transformers

Rated power Ak Bk Ck Short-circuit Impedance

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BS EN 50588-1:2015 EN 50588-1:2015 (E)

12

Transformers can be requested and offered with sound power level LWA other than the listed values

The sound power level LWA for transformers AAA0 has to be agreed between manufacturer and

purchaser

NOTE Some cells in Table 4 are empty because these combinations are not covered according the

European Regulation No 548/2014 of May 21, 2014

6.2.3 Load loss and no load loss in case of other insulation level

The level of losses given in 6.2.2 shall be weighted by the correction factors given in Table 5 below,

in order to take care of variations related to the highest voltage for equipment values

Table 5 — Correction of load loss and no load loss in case other insulation level

Ref highest voltage for equipment

1,1 kV < Um≤ 24 kV and the

other with 1,1 kV < Um≤ 24 kV

The maximum levels of losses indicated in Table 2, Table 3 and Table 4 can be increased by 10 % for no load loss and

by 10 % for load loss

6.2.4 Load loss and no load loss in case of dual voltage

in order to take care of variations related to dual voltage windings

For transformer having insulation level according to Table 5 and having dual voltage according to

Table 6 the loss level shall take into account both corrections

Table 6 — Correction of load loss and no load loss in case of dual voltage Ref Dual voltage Correction of load loss and no load loss

A One winding In case of transformers with one high-voltage winding and two voltages

available from tapped low-voltage winding, losses shall be calculated based

on the higher low-voltage and shall comply with the levels indicated in Table 2, Table 3 and Table 4

The maximum available power on the lower low-voltage on such transformers shall be no more than 0,85 times its rated power

In case of transformers with one high-voltage winding with two voltages available from a tap, the maximum available power on the lower high-voltage

on such transformer shall be limited to 0,85 of its nominal rated power

In the case where the full rated power is available regardless of the combination of voltages, the levels of losses indicated in Table 2, Table 3 and Table 4 can be increased by 15 % for no load loss and by 10 % for load loss

B Both windings The levels of losses indicated in Table 2, Table 3 and Table 4 shall be

increased by 20 % for no load loss and by 20 % for load loss in case of dual voltage on both windings These levels of losses are given on the basis that the rated power is the same regardless of the combination of voltages

12

purchaser

12

purchaser

BS EN 50588-1:2015

EN 50588-1:2015 (E)

13

6.3 Transformers with rated power 3 150 kVA < Sr < 40 000 kVA

Peak efficiency Index (PEI) is the maximum value of the ratio of the transmitted apparent power of a transformer minus the electrical losses to the transmitted apparent power of the transformer

The Peak Efficiency Index includes the losses associated with the cooling system (Pc0) that is in service in the no-load condition If additional cooling is required for the transformer to operate at

kPEI, then the additional cooling loss required for this cooling shall be added to Pc0 in the calculation

of PEI Any additional cooling and associated cooling loss in excess of that required at kPEI

necessary to achieve rated power is excluded

NOTE This applies to transformers equipped with heat-exchangers which need pumps and fans to provide heat dissipation (e.g ODAF, ODWF, OFWF, OFAF, OFAN, ONAF, KNAF)

The minimum PEI value, which shall be met in all cases, can be obtained with different combinations of no load and load losses This is equivalent to different load factors at which PEI occurs The ratio of the load and no load losses needs to be tailored to the application in order to obtain the best actual efficiency in service In order to achieve this, the following methods are available:

- Providing capitalization values for no load and load losses that reflect the anticipated loading (this is the recommended method);

- Prescribing maximum values for no load and load losses;

- Specifying minimum efficiency index at a specific load factor

Annex A includes the calculation method for the PEI Table 7 and Table 8 indicate the PEI for

transformers with rated power Sr > 3 150 kVA

Table 7— Minimum Peak Efficiency Index (PEI) for Liquid immersed transformers

RATED POWER (kVA) PEI (%)

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12

The sound power level LWA for transformers AAA0 has to be agreed between manufacturer and purchaser

NOTE Some cells in Table 4 are empty because these combinations are not covered according the European Regulation No 548/2014 of May 21, 2014

Table 5 — Correction of load loss and no load loss in case other insulation level Ref highest voltage for equipment

For transformer having insulation level according to Table 5 and having dual voltage according to Table 6 the loss level shall take into account both corrections

BS EN 50588-1:2015 EN 50588-1:2015 (E)

12

purchaser

In the case where the full rated power is available regardless of the combination of voltages, the levels of losses indicated in Table 2, Table 3 and

Table 4 can be increased by 15 % for no load loss and by 10 % for load loss

increased by 20 % for no load loss and by 20 % for load loss in case of dual voltage on both windings These levels of losses are given on the basis that

the rated power is the same regardless of the combination of voltages

BS EN 50588-1:2015 EN 50588-1:2015 (E)

12

purchaser

BS EN 50588-1:2015 EN 50588-1:2015 (E)

12

purchaser

12

The sound power level LWA for transformers AAA0 has to be agreed between manufacturer and purchaser

NOTE Some cells in Table 4 are empty because these combinations are not covered according the European Regulation No 548/2014 of May 21, 2014

Table 5 — Correction of load loss and no load loss in case other insulation level Ref highest voltage for equipment

For transformer having insulation level according to Table 5 and having dual voltage according to Table 6 the loss level shall take into account both corrections

BS EN 50588-1:2015

EN 50588-1:2015 (E)

13

Peak efficiency Index (PEI) is the maximum value of the ratio of the transmitted apparent power of a transformer minus the electrical losses to the transmitted apparent power of the transformer

The Peak Efficiency Index includes the losses associated with the cooling system (Pc0) that is in service in the no-load condition If additional cooling is required for the transformer to operate at

NOTE This applies to transformers equipped with heat-exchangers which need pumps and fans to provide heat dissipation (e.g ODAF, ODWF, OFWF, OFAF, OFAN, ONAF, KNAF)

The minimum PEI value, which shall be met in all cases, can be obtained with different combinations of no load and load losses This is equivalent to different load factors at which PEI occurs The ratio of the load and no load losses needs to be tailored to the application in order to obtain the best actual efficiency in service In order to achieve this, the following methods are available:

- Providing capitalization values for no load and load losses that reflect the anticipated loading (this is the recommended method);

For transformers having dual voltage on both windings for which both voltages on one winding are fully rated in combination with one of the voltages on the other winding, the levels of losses shall be based on the highest power and the values indicated in Table 2, Table 3 and Table 4 can be increased

by 15 % for no load losses and by 10 % for load losses� The level of losses shall refer to the highest voltages of both windings� This remains valid even if further voltage combinations are available�

For transformer having insulation level according to Table 5 and having dual voltage according to Table 6 the loss level shall take into account both corrections�

6.2.5 Three winding transformers for PV applications

Dual voltage correction factors given in Table 6, Ref A, apply also to transformers for photovoltaic applications, which have two low voltage windings that each have half the rated power of the high voltage winding�



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BS EN 50588-1:2015 EN 50588-1:2015 (E)

14

Table 8 — Minimum Peak Efficiency Index (PEI) for dry-type transformers

The value of noise and short circuit impedance shall be defined during enquiry stage

6.4 Transformers with special requirements

6.4.1 Rated power not included in the list

For transformer having a rated power different from the values given in the tables, a linear interpolation shall be made based on the neighbouring values for losses and PEI

6.4.2 Transformers equipped with tapping connections suitable for operation while

transformer is energised or on load and rated power Sr ≤ 3 150 kVA

When transformers are equipped with tapping connections suitable for operation while transformer

is energised or on load for voltage adaptation purposes, the level of load loss and no load loss of the list of this standard shall be increased as per COMMISSION REGULATION (EU) No 548/2014

of 21 May 2014:

- From 01/07/2015 the maximum allowable levels of losses set out in Table 2, Table 3 and Table 4 for the cases detailed in Table ZZ.1 shall be increased by 20 % for no load losses and 5 % for load losses

- From 01/07/2021 the maximum allowable levels of losses set out in Table 2, Table 3 and Table 4 for the cases detailed in Table ZZ.1 shall be increased by 10 % for no load losses and 0 % for load losses

Such corrections are applicable irrespectively of the technology used to perform the voltage adaptation

The losses of the transformers counted, shall be the overall losses whatever the kind of transformers, included all devices to manage the AVR inside the transformers

For transformer having insulation level according to Table 5 and having tapping connections suitable for operation while transformer is energised or on load for voltage adaptation purposes both corrections shall be taken into account

NOTE AVR: Automatic Voltage Regulation: to automatically control the input or output voltage of the transformer for on-load voltage regulation purposes

13

Peak efficiency Index (PEI) is the maximum value of the ratio of the transmitted apparent power of a

transformer minus the electrical losses to the transmitted apparent power of the transformer

The Peak Efficiency Index includes the losses associated with the cooling system (Pc0) that is in

service in the no-load condition If additional cooling is required for the transformer to operate at

NOTE This applies to transformers equipped with heat-exchangers which need pumps and fans to

provide heat dissipation (e.g ODAF, ODWF, OFWF, OFAF, OFAN, ONAF, KNAF)

The minimum PEI value, which shall be met in all cases, can be obtained with different

combinations of no load and load losses This is equivalent to different load factors at which PEI

occurs The ratio of the load and no load losses needs to be tailored to the application in order to

obtain the best actual efficiency in service In order to achieve this, the following methods are

available:

- Providing capitalization values for no load and load losses that reflect the anticipated

loading (this is the recommended method);

RATED POWER (kVA) AA PEI (%) A

Table 8 — Minimum Peak Efficiency Index (PEI) for dry-type transformers

The value of noise and short circuit impedance shall be defined during enquiry stage

6.4 Transformers with special requirements

6.4.1 Rated power not included in the list

For transformer having a rated power different from the values given in the tables, a linear

interpolation shall be made based on the neighbouring values for losses and PEI

6.4.2 Transformers equipped with tapping connections suitable for operation while

transformer is energised or on load and rated power Sr ≤ 3 150 kVA

When transformers are equipped with tapping connections suitable for operation while transformer

is energised or on load for voltage adaptation purposes, the level of load loss and no load loss of

the list of this standard shall be increased as per COMMISSION REGULATION (EU) No 548/2014

of 21 May 2014:

- From 01/07/2015 the maximum allowable levels of losses set out in Table 2, Table 3 and

Table 4 for the cases detailed in Table ZZ.1 shall be increased by 20 % for no load losses and 5 % for load losses

- From 01/07/2021 the maximum allowable levels of losses set out in Table 2, Table 3 and

Table 4 for the cases detailed in Table ZZ.1 shall be increased by 10 % for no load losses and 0 % for load losses

Such corrections are applicable irrespectively of the technology used to perform the voltage

adaptation

The losses of the transformers counted, shall be the overall losses whatever the kind of

transformers, included all devices to manage the AVR inside the transformers

For transformer having insulation level according to Table 5 and having tapping connections

suitable for operation while transformer is energised or on load for voltage adaptation purposes both

corrections shall be taken into account

NOTE AVR: Automatic Voltage Regulation: to automatically control the input or output voltage of the

transformer for on-load voltage regulation purposes

BS EN 50588-1:2015+A1:2016

EN 50588-1:2015+A1:2016

16

The PEI requirements in Table 7 and Table 8 apply to autotransformers and separate winding

transformers having three windings as follows Assuming that ratings are x/y/z, then:

– if x and y are equal and z is lower or equal than one third of x or y, the PEI shall be the one

corresponding to x or y rating and the losses of winding z shall not be considered for PEI

calculation;

– if x is equal to the sum of y and z, the PEI shall be the one corresponding to x rating and the three

winding losses shall be considered for PEI calculation;

– in all other cases, the PEI shall be the one corresponding to maximum of the three ratings� Load

loss must be measured for each winding pairs and the load combination to be used for PEI

calculation is:

EN 50588-1:2015/A1:2016 (E)

7

For transformer having insulation level according to Table 5 and having dual voltage according to Table 6 the

loss level shall take into account both corrections.”

After 6.2.4, add the following new subclause:

“6.2.5 Three winding transformers for PV applications

Dual voltage correction factors given in Table 6, Ref A, apply also to transformers for photovoltaic

applications, which have two low voltage windings that each have half the rated power of the high voltage

winding.”

5 Modification to 6.3, Transformers with rated power 3 150 kVA < Sr < 40 000 kVA

At the end of 6.3, after “The value of noise and short circuit impedance shall be defined during enquiry stage.",

add the following new paragraphs:

"The PEI requirements in Table 7 and Table 8 apply to autotransformers and separate winding transformers

having three windings as follows Assuming that ratings are x/y/z, then:

- if x and y are equal and z is lower or equal than one third of x or y, the PEI shall be the one corresponding

to x or y rating and the losses of winding z shall not be considered for PEI calculation;

- if x is equal to the sum of y and z, the PEI shall be the one corresponding to x rating and the three winding

losses shall be considered for PEI calculation;

- in all other cases, the PEI shall be the one corresponding to maximum of the three ratings Load loss must

be measured for each winding pairs and the load combination to be used for PEI calculation is:

z y

x z z y

x y x

+ +

NOTE 1 In general, transformers of similar design criteria, but with more than two windings, have higher total losses

and lower PEI values This formula also allows for the verification of PEI requirements in transformers other than two

winding transformers, such as three winding transformers and autotransformers For the computation of the load loss for

each winding, the criteria given in IEC 60076-8 can be taken as reference

NOTE 2 For example, for a 6 000/6 000/3 000 kVA, the PEI limit shall be that of 6 000 kVA and the load combination for

load loss calculation shall be:

2000 / 4000 / 6000 3000

6000

6000 3000

3000 6000

6000 6000

+ +

The approach used for three winding transformers can be applied in principle to transformers with more than

three windings

For transformers with re-connectable windings PEI calculation shall be made based on loss measurements

taken at the highest rated voltage(s)."





Tiêu đề	Medium Power Transformers 50 Hz, With Highest Voltage For Equipment Not Exceeding 36 Kv Part 1: General Requirements
Trường học	British Standards Institution
Chuyên ngành	Standards
Thể loại	Standard
Năm xuất bản	2017
Thành phố	London

Định dạng
Số trang	36
Dung lượng	2,52 MB