EN 50708-3-1:2020

SLOVENSKI STANDARD
01-julij-2020
Nadomešča:
SIST EN 50629:2015
SIST EN 50629:2015/A1:2016
SIST EN 50629:2015/A2:2018
Močnostni transformatorji - Dodatne evropske zahteve - 3-1. del: Veliki močnostni
transformator - Splošne zahteve
Power transformers - Additional European requirements: Part 3-1 Large power
transformer - General requirements
Transformateurs de puissance - Exigences européennes supplémentaires: Partie 3-1 :
Transformateurs de grande puissance
Ta slovenski standard je istoveten z: EN 50708-3-1:2020
ICS:
29.180 Transformatorji. Dušilke Transformers. Reactors
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 50708-3-1

NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2020
ICS 29.180 Supersedes EN 50629:2015 (PART) and all of its
amendments and corrigenda (if any)
English Version
Power transformers - Additional European requirements: Part 3-
1 Large power transformer - General requirements
Transformateurs de puissance - Exigences européennes To be completed
supplémentaires: Partie 3-1 : Transformateurs de grande
puissance
This European Standard was approved by CENELEC on 2019-10-09. 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, 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: Rue de la Science 23, B-1040 Brussels
© 2020 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN 50708-3-1:2020 E
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Service condition . 5
5 Rating and general requirements. 5
5.1 Energy performance requirements . 5
5.1.1 General . 5
5.1.2 Minimum PEI values . 5
5.1.3 Optimization of transformer losses according to application . 8
6 Rating plate . 8
7 Tolerances . 8
8 Acceptance Tests . 8
9 Accessories and fittings . 8
10 Capitalization of losses . 8
11 Transformers overhaul . 8
Annex A (Informative) Peak Efficiency Index formula, graphs and calculations . 9
Annex ZZ (informative) Relationship between this European Standard and the ecodesign
requirements of Commission Regulation (EU) No 548/2014 of 21 May 2014 and its
amendment No 2019/1783 of 1 October 2019 on implementing Directive 2009/125/EC of
the European Parliament and of the Council with regard to small, medium and large
power transformers aimed to be covered . 14
Bibliography . 16

European foreword
This document (EN 50708-3-1:2020) has been prepared by CLC/TC 14, “Power transformers”.
The following dates are fixed:
• latest date by which this document has (dop) 2020-11-22
to be implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2023-05-22
standards conflicting with this document
have to be withdrawn
This document supersedes EN 50629:2015 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CENELEC 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.
Introduction
For the purpose of this document, the requirements of the general EN 50708-1-1:2020 apply.
This document contains particular requirements for specific transformers or transformer applications, which are
based on the requirements of the general EN 50708-1-1:2020.
This document should be considered in conjunction with the requirements of the general parts.
The particular requirements of the different subparts of EN 50708 supplement, modify or replace certain
requirements of the general parts of EN 50708-1 and/or EN 50708-1-X being valid at the time of publication of
this document. The absence of references to the exclusion of a part or a clause of a general part means that
the corresponding clauses of the general part are applicable (undated reference).
Requirements of other -X parts with X greater than 1 being eventually relevant for cases covered by this
document also apply. This document could therefore also supplement, modify or replace certain of these
requirements valid at the time of publication of this document.
The main clause numbering of each part follows the pattern and corresponding references of
EN 50708-1-1:2020. The numbers following the particular number of this document are those of the
corresponding parts, or clauses of the other parts of the EN 50708 series, valid at the time of publication of this
document, as indicated in the normative references of this document (dated reference).
In the case where new or amended general parts with modified numbering were published after the subpart
was issued, the clause numbers referring to a general part in subparts might no longer align with the latest
edition of the general part. Dated references should be observed.
1 Scope
The scope of this document is to define performance requirements of Large Power Transformers in compliance
with EN 50708-1-1:2020.
NOTE This document covers the transformers under Commission Regulation (EU) No 548/2014 of 21 May 2014 and
its amendment No 2019/1783 of 1 October 2019, gives additional specific guidance for single phase transformers,
autotransformers, multi winding transformers and for transformers with OD and OF cooling systems, necessary for the
correct application of energy efficiency requirements to these categories of transformers.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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.
EN 50708-1-1:2020, Power transformers - Additional European requirements: Part 1-1: Common part - General
requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 50708-1-1:2020 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
4 Service condition
The additional requirements for service condition are given in EN 50708-1-1:2020.
5 Rating and general requirements
5.1 Energy performance requirements
5.1.1 General
For Large power transformers the energy performance requirement consist of a minimum value of Peak
Efficiency Index which is the maximum value of the Efficiency Index.
The Peak Efficiency Index is to be calculate in accordance with EN 50708-1-1:2020.
The tables in this clause indicate the minimum energy performances for TIER1 and TIER2.
TIER1 has been applied since 1 July 2015 for the values of losses following Commission Regulation (EU) No
548/2014 of 21 May 2014 and its amendment No 2019/1783 of 1 October 2019.
TIER2 shall be applied from 1 July 2021 for the values of losses following Commission Regulation (EU) No
548/2014 of 21 May 2014 and its amendment No 2019/1783 of 1 October 2019.
5.1.2 Minimum PEI values
Liquid immersed and dry type large power transformers shall have Minimum Peak Efficiency Index values
according to Table 1, Table 2 and Table 3 respectively.
For rated powers different from the ones reported in Table 1, Table 2 and Table 3, the corresponding PEI value
shall be obtained by linear interpolation from the two adjacent values.
The PEI requirements apply to transformers and auto-transformers.
For auto-transformers the reference power for PEI values is the rated power.
Three phase or single phase transformers shall be evaluated against the rated power of the individual
transformer.
Table 1 — Values of minimum Peak Efficiency Index for liquid immersed large power transformers
Minimum Peak Efficiency Index (%)
S
r
(MVA)
Tier 1 Tier 2
≤ 0,025 97,742 98,251
0,05 98,584 98,891
0,1 98,867 99,093
0,16 99,012 99,191
0,25 99,112 99,283
0,315 99,154 99,320
0,4 99,209 99,369
0,5 99,247 99,398
0,63 99,295 99,437
0,8 99,343 99,473
1 99,360 99,484
1,25 99,418 99,487
1,6 99,424 99,494
2 99,426 99,502
2,5 99,441 99,514
3,15 99,444 99,518
4 99,465 99,532
5 99,483 99,548
6,3 99,510 99,571
8 99,535 99,593
10 99,560 99,615
12,5 99,588 99,640
16 99,615 99,663
20 99,639 99,684
25 99,657 99,700
31,5 99,671 99,712
40 99,684 99,724
50 99,696 99,734
63 99,709 99,745
80 99,723 99,758
100 99,737 99,770
125 99,737 99,780
160 99,737 99,790
≥ 200 99,737 99,797
Table 2 — Values of minimum Peak Efficiency Index for dry-type large power transformers with
Um ≤ 36 kV
Minimum Peak Efficiency Index (%)
S
r
(MVA)
Tier 1 Tier 2
3,15 < S ≤ 4 99,348 99,382
r
5 99,354 99,387
6,3 99,356 99,389
8 99,357 99,390
≥ 10 99,357 99,390
Table 3 — Values of minimum Peak Efficiency Index for dry-type large power transformers with
Um > 36 kV
Minimum Peak Efficiency Index (%)
S
r
(MVA)
Tier 1 Tier 2
≤ 0,05 96,174 96,590
0,1 97,514 97,790
0,16 97,792 98,016
0,25 98,155 98,345
0,4 98,334 98,570
0,63 98,494 98,619
0,8 98,677 98,745
1 98,775 98,837
1,25 98,832 98,892
1,6 98,903 98,960
2 98,942 98,996
2,5 98,933 99,045
3,15 99,048 99,097
4 99,158 99,225
5 99,200 99,265
6,3 99,242 99,303
8 99,298 99,356
10 99,330 99,385
12,5 99,370 99,422
16 99,416 99,464
20 99,468 99,513
25 99,521 99,564
31,5 99,551 99,592
40 99,567 99,607
50 99,585 99,623
≥ 63 99,590 99,626
5.1.3 Optimization of transformer losses according to application
The minimum PEI value prescribed, 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 t
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