SIST EN 50708-1-1:2020

SLOVENSKI STANDARD
SIST EN 50708-1-1:2020
01-julij-2020
Nadomešča:
SIST EN 50588-1:2017
SIST EN 50629:2015
SIST EN 50629:2015/A1:2016
SIST EN 50629:2015/A2:2018
Močnostni transformatorji - Dodatne evropske zahteve - 1-1. del: Skupni del -
Splošne zahteve
Power transformers - Additional European requirements: Part 1-1: Common part -
General requirements
Transformateurs de puissance - Exigences européennes supplémentaires : Partie 1 -
Partie commune
Ta slovenski standard je istoveten z: EN 50708-1-1:2020
ICS:
29.180 Transformatorji. Dušilke Transformers. Reactors
SIST EN 50708-1-1:2020 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 50708-1-1:2020

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SIST EN 50708-1-1:2020


EUROPEAN STANDARD EN 50708-1-1

NORME EUROPÉENNE

EUROPÄISCHE NORM
May 2020
ICS 29.180 Supersedes EN 50588-1:2017 (PART), EN 50629:2015
(PART) and all of its amendments and corrigenda (if any)
English Version
Power transformers - Additional European requirements: Part 1-
1: Common part - General requirements
Transformateurs de puissance - Exigences européennes To be completed
supplémentaires : Partie 1 - Partie commune
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 50708-1-1:2020 E

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Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Service condition . 10
5 Ratings and general requirements . 11
5.1 Rated power . 11
5.2 Rated frequency . 11
5.3 Energy performance . 11
5.3.1 Energy performance requirements . 11
5.3.2 Exclusion from energy performance requirements . 11
5.3.3 Reference conditions . 12
5.3.4 Technical documentation . 12
6 Rating plate . 13
7 Tolerances . 13
7.1 Tolerance during factory acceptance tests . 13
7.2 Tolerances for Market surveillance. 14
8 Tests . 14
8.1 General . 14
8.2 Measurement of cooling consumption . 14
9 Accessories and fittings . 14
10 Capitalization of losses . 14
11 Transformer overhaul . 15
Annex A (normative) Peak efficiency calculation . 16
A.1 Efficiency Index. 16
A.2 Peak Efficiency Index . 16
A.3 PEI calculation for transformers having more than two windings . 17
Annex B (informative) Capitalization of losses . 19
B.1 General Theory, Concept of Capitalization . 19
B.2 Impact of capitalization values . 19
B.3 Capitalization formula . 20
B.3.1 General . 20
B.3.2 Calculation of factor A . 20
B.3.3 Calculation of factor B . 21
B.3.4 Use of A and B for tender evaluation. 23
B.3.5 Determination of factors A and B . 24
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Annex C (informative) A-deviations . 26
Annex D (informative) Additional considerations related to energy performances. 27
D.1 General . 27
D.2 Autotransformers . 27
D.3 Voltage and insulation level . 27
D.4 More than two windings. 27
D.5 Short-circuit impedance . 27
D.6 Tapping range . 27
D.7 Losses on taps different than rated tap . 28
D.8 Separate phases . 28
Annex E (informative) Transformer overhaul . 29
E.1 General . 29
E.1.1 Overview . 29
E.1.2 Energy performance. 29
E.1.3 Life expectancy . 29
E.2 Classification of overhaul activities . 29
E.2.1 Overview . 29
E.2.2 Repair. 30
E.2.3 Upgrade . 30
E.2.4 Refurbishment . 30
E.2.5 Retrofit . 31
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 . 32
Bibliography . 33

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European foreword
This document (EN 50708-1-1:2020) 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 50588-1:2017 and EN 50629:2015 and all of their 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 essential requirements of Commission Regulation (EC).
For the relationship with the Commission Regulation (EC) see informative Annex ZZ, which is an integral part
of this document.
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Introduction
The EN 50708 series, “Power transformers – Additional European requirements” has been prepared by
CENELEC TC 14 to address specific European requirements of power transformers related EU Regulations
and local practices.
Technical requirements set by the EN 50708 series supplement, modify or replace certain requirements of the
other EN standards derived from equivalent IEC international standards.
This series contains general requirements on energy performance, accessories, fittings, tests, mechanical
requirements etc. structured as follows:
— Part 1 series - Common requirements;
— Part 2 series - Medium power transformers;
— Part 3 series - Large power transformers.
The EN 50708-X parts with X greater than 1 contain particular requirements for a different category of
transformers or transformer applications which are based on the requirements of the general parts of
EN 50708-1-1.
The EN 50708-X parts should be considered in conjunction with the requirements of the general part.
The particular requirements of these subparts of EN 50708 supplement, modify or replace certain requirements
of the general parts of EN 50708-1-1 and/or EN 50708-1-X being valid at the time of publication of this part. 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 part
also apply. This part may 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 subpart follows the pattern and corresponding references of EN 50708-1-1.
The numbers following the particular number of this part 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 part, 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.
It is acknowledged that environmental requirements including energy in the use phase are a significant aspect
that can be addressed through product design. As the material content increases to improve energy
performance, it is advisable to make a proper life cycle assessment including recycling of the extra raw material
and the overall energy used to produce and transport transformers. Some guidelines are given in EN 60076-1.
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1 Scope
This document is part of the EN 50708 series which applies to transformers in compliance with EN 60076-1.
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 50329:2003, Railway applications - Fixed installations - Traction transformers
EN 50708-2-1:2020, Power transformers - Additional European requirements: Part 2-1 Medium power
transformer - General requirements
EN 50708-3-1:2020, Power transformers - Additional European requirements: Part 3-1 Large power transformer
- General requirements
EN 60076 (all parts), Power transformers (IEC 60076 series)
EN 60310:2016, Railway applications - Traction transformers and inductors on board rolling Stock (IEC 60310)
EN 61378-1:2011, Convertor transformers - Part 1: Transformers for industrial applications (IEC 61378-1:2011)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 60076-1:2011 and the following 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
3.1
medium power transformer
MPT
power transformer with all windings having a rated power lower than or equal to 3 150 kVA, and highest voltage
for equipment greater than 1,1 kV and lower than or equal to 36 kV
Note 1 to entry: The definitions of power transformer and winding are given in EN 60076-1.
Note 2 to entry: The national practice of the Czech Republic could require the use of the highest voltages for equipment
in AC three-phase systems of 38,5 kV instead of 36 kV and 25 kV instead of 24 kV. These units have a rated power lower
than or equal to 3 150 kVA:
— with U = 38,5 kV are considered as U = 36 kV (ref. to EN 50708-2-1:2020);
m m
— with U = 25 kV are considered as U = 24 kV (ref. to EN 50708-2-1:2020).
m m
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3.2
large power transformer
LPT
power transformer with at least one winding having either a rated power greater than 3 150 kVA or highest
voltage for equipment greater than 36 kV
Note 1 to entry: The definitions of power transformer and winding is given in EN 60076-1.
Note 2 to entry: The national practice of Czech Republic requires the use of the highest voltages for equipment in AC three-
phase systems of 38,5 kV instead of 36 kV and 25 kV instead of 24 kV. These units have a rated power greater than 3 150
kVA:
— with U = 38,5 kV are considered as U = 36 kV (ref. to EN 50708-3-1:2020);
m m
— with U = 25 kV are considered as U = 24 kV (ref. to EN 50708-3-1:2020).
m m
3.3
medium power pole-mounted transformer
power transformer with a rated power of up to 400 kVA suitable for outdoor service and specifically designed to
be mounted on the support structures of overhead power lines
Note 1 to entry: The definitions of power transformer and winding are given in EN 60076-1.
Note 2 to entry: For definitions of pole see IEV [466–07–01].
3.4
load factor
k
ratio of actual input current over the rated current of transformer
Note 1 to entry: Normally the ratio is 0 ≤ k ≤ 1.
3.5
transmitted apparent power
kSr
product of the load factor and rated power
3.6
Efficiency Index
EI
ratio of the transmitted apparent power of a transformer minus electrical losses to the transmitted apparent
power of the transformer
3.7
Peak Efficiency Index
PEI
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
Note 1 to entry: PEI is the maximum value of EI that can be achieved at the optimum value of load factor.
3.8
load factor of Peak Efficiency Index
k
PEI
load factor at which Peak Efficiency Index occurs
Note 1 to entry: Alternative cooling modes can require an iterative calculation of the kPEI. In any case, the kPEI is defined
at the point where the highest PEI occurs.
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3.9
declared value
values given in the technical documentation and where applicable, the values used to calculate these values
Note 1 to entry: The values given are pursuant to point 2 of Directive 2009/125/EC, Annex IV.
3.9.1
declared value of loss
loss measured by the manufacturer and written in the test report part of technical documentation and on the
rating plate
Note 1 to entry: This definition applies both to no-load loss and to load loss.
Note 2 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 Commision Regulation
(EU) No 548/2014.
Note 3 to entry: This definition complies with item g) of point 2 of Directive 2009/125/EC, Annex IV.
3.9.2
declared value of no-load loss
P
0
no-load loss measured by the manufacturer and written in the test report part of technical documentation and
on the rating plate
Note 1 to entry: For definition of no-load loss, see EN 60076-1.
3.9.3
declared value of load loss
P
k
load loss measured by the manufacturer and written in the test report part of technical documentation and on
the rating plate
Note 1 to entry: For definition of load loss see EN 60076-1.
3.9.4
declared value of electrical power required by the cooling system for no load operation
P
c0
electrical power required by fan and liquid pump motors for no load operation as derived from the transformer
type test certificates
Note 1 to entry: The electrical power required by the cooling system for no load operation is not measured all the time
because this is a type test according to EN 60076-1.
3.9.5
declared value of additional electrical power required by the cooling system for the load factor of k
P (k)
ck
additional electrical power required (in addition to Pc0) by the cooling system for continuous operation at k times
the rated load ensuring the compliance with the temperature rise derived from the transformer type test
measurements of the power taken by the fan and liquid pump motors
Note 1 to entry: The electrical power required by the cooling system for k times the rated load operation is not measured
all the time, because this is a type test according to EN 60076-1. It can be extrapolated from the temperature rise test.
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3.9.6
declared value of PEI
PEI calculated from the declared values of no-load loss, load loss and power required by the cooling system for
load operation at k according to the above definitions
PEI
3.10
dual voltage transformer
transformer with one or more windings with two voltages available in order to be able to operate and supply
rated power at either of two different voltage values
3.11
acceptance test
contractual test to prove to the customer that the item meets certain conditions of its specification
Note 1 to entry: The test may be witnessed by purchaser or/and third party.
Note 2 to entry: The common IEC acceptance tests do not require witnesses. Routine tests are performed on every
transformer; for this reason the factory acceptance test shall be agreed between purchaser and supplier at the order stage.
[SOURCE: IEV ref 151-16-23]
3.12
witnessed testing
active observance of the physical testing of the product under investigation by another party, to draw conclusions
on the validity of the test and the test results and which may include conclusions on the compliance of testing
and calculations methods used with applicable standards and legislation
3.13
instrument transformer
transformer intended to transmit an information signal to measuring instruments, meters and protective or
control devices or similar apparatus even if it supplies energy for the operation of connected equipment
Note 1 to entry: The difference between the definition in Commission Regulation 548/2014 and the CENELEC one is in
the use of the word ‘supply’ rather than ‘transmit an information signal’.
[SOURCE: EN 61869-1:2009, 3.1.1, modified]
3.14
transformer with low-voltage windings specifically designed for use with rectifiers to provide a DC
supply
transformer specifically designed and intended to supply power electronic or rectifier loads specified according
to EN 61378-1:2011
Note 1 to entry: This definition covers transformers designed for use with rectifiers to provide a DC supply in certain
applications.
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.
Therefore, they are part of the scope of this document and are expected to comply with Commission Regulation (EU)
No. 548/2014.
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3.15
transformer specifically designed for offshore applications and floating offshore applications
transformer to be installed on fixed or floating offshore platforms, offshore wind turbines or on board ships and
all kinds of vessels
3.16
transformer specially designed for emergency installations
transformer designed to only 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 material;
— permanent mounting on a transporter arrangement.
3.17
transformers and auto-transformers specifically designed for railway feeding systems
transformer as defined in EN 50329:2003
3.18
earthing or grounding transformers, this is, three-phase transformers intended to provide a neutral
point for system grounding purposes
three-phase transformer or reactor connected in a power system to provide a neutral connection for earthing
either directly or via an impedance
[SOURCE: EN 60076-6:2008, 3.1.10, modified]
3.19
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 60310:2016
3.20
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, and used for the purpose of starting a rotating machine
3.21
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.
4 Service condition
See EN 60076-1.
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5 Ratings and general requirements
5.1 Rated power
The reference rated power for any losses evaluation is the continuous rated power as stated in EN 60076-1.
If additional cooling system such as fans or pumps are to provide additional power for a situation limited in time
when the normal power supply is interrupted due to either an unplanned occurrence (such as a power failure)
or a station refurbishment, but not to permanently upgrade an existing substation, then such overloading rating
cannot be claimed to be the rated power.
5.2 Rated frequency
The rated frequency is the normal undisturbed frequency of the network where the transformer is installed,
unless otherwise specified the rated frequency is 50 Hz.
5.3 Energy performance
5.3.1 Energy performance requirements
The energy performance of a transformer in accordance with this standard is defined as follows:
a) Maximum no-load and load losses at rated power for three-phase MPT;
b) The Peak Efficiency Index and the load at which it occurs for LPT.
For Peak efficiency calculation see Annex A.
In case of forced cooling system, the consumption of the cooling system shall be considered together with the
...