SIST EN 50629:2015

SLOVENSKI STANDARD
SIST EN 50629:2015
01-september-2015
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(QHUJ\SHUIRUPDQFHRIODUJHSRZHUWUDQVIRUPHUV8P!N9RU6U•09$
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Ta slovenski standard je istoveten z: EN 50629:2015
ICS:
27.015 (QHUJLMVNDXþLQNRYLWRVW Energy efficiency. Energy
2KUDQMDQMHHQHUJLMHQD conservation in general
VSORãQR
29.180 Transformatorji. Dušilke Transformers. Reactors
SIST EN 50629:2015 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 50629:2015

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SIST EN 50629:2015


EUROPEAN STANDARD EN 50629

NORME EUROPÉENNE

EUROPÄISCHE NORM
June 2015
ICS 29.180

English Version
Energy performance of large power transformers (Um > 36 kV or
Sr ≥ 40 MVA)
Performance énergétique des transformateurs de grande Energiekennwerte von Großleistungstransformatoren (Um >
puissance (Um > 36 kV ou Sr ≥ 40 MVA) 36 kV oder Sr ≥ 40 MVA)
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
© 2015 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
 Ref. No. EN 50629:2015 E

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SIST EN 50629:2015
EN 50629:2015 (E)
Contents Page
Foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 7
3 Terms and definitions . 7
4 Efficiency and Efficiency Index calculation . 8
4.1 General . 8
4.2 Efficiency Index general formula . 8
4.3 Peak Efficiency Index . 9
5 Minimum Peak Efficiency Index values . 10
5.1 Standardised values of Minimum PEI . 10
5.2 Optimization of transformer losses according to application . 12
5.3 Rating plate data . 12
5.4 Transformer asset data . 12
5.5 Tolerances, measurement uncertainties and market surveillance. 12
5.5.1 Factory acceptance . 12
5.5.2 Verification procedure for market surveillance . 13
6 Transformers categories currently excluded . 13
7 Capitalisation of losses . 14
Annex A (normative) Minimum PEI for dry type large power transformers . 15
Annex B (informative) Peak Efficiency Index formula, graphs and calculations . 16
B.1 Calculation of k . 16
PEI
B.2 Graph of Efficiency Index and load factor with loss contributions . 17
B.3 Graphs of prescribed PEI values and rated power . 18
B.4 Independence of PEI to rated power. 19
B.5 Calculation of losses from PEI, k and S . 20
PEI r
Annex C (informative) Form for data requested . 21
C.1 Example of form for data requested . 21
C.2 Indications for filling the table . 22
Annex D (informative) Benchmark of Peak Efficiency Index . 23
D.1 General . 23
D.2 Benchmark figures . 23
D.3 Variations from the benchmark . 28
D.3.1 General . 28
D.3.2 Autotransformers. 28
D.3.3 Voltage and insulation level . 28
D.3.4 More than two windings . 28
D.3.5 Short-circuit impedance . 28
D.3.6 Tapping range . 29
D.3.7 Losses on taps different that rated tap . 29
D.3.8 Separate phases . 30
D.4 Exceptions from benchmark . 30
D.4.1 General . 30
D.4.2 Transformers with unusual combinations of windings and voltages . 30
D.4.3 Installation restrictions . 30
D.4.4 Offshore installation . 30
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SIST EN 50629:2015
EN 50629:2015 (E)
D.4.5 Transportation restrictions . 30
D.4.6 Transformers for temporary installation . 30
D.4.7 Converter transformers . 30
D.4.8 Dry-type and gas insulated transformers . 30
D.4.9 Other exemptions . 31
Annex E (informative) Capitalisation of losses . 32
E.1 General Theory, Concept of Capitalisation. 32
E.2 Impact of capitalisation values . 32
E.3 Capitalisation formula . 33
E.3.1 General . 33
E.3.2 Calculation of factor A . 34
E.3.3 Calculation of factor B . 35
E.3.4 Use of A and B for tender evaluation . 37
E.3.5 Determination of factors A and B . 37
Annex F (informative) Background on verification tolerances during market surveillance . 39
Annex 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 . 40
Bibliography . 41

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SIST EN 50629:2015
EN 50629:2015 (E)
Foreword
This document (EN 50629:2015) has been prepared by CLC/TC 14, "Power transformers".
The following dates are fixed:
- latest date by which this document has (dop) 2016-06-25
to be implemented at national level by
publication of an identical national
standard or by endorsement
- latest date by which the national (dow) 2018-06-25
standards conflicting with this
document have to be withdrawn

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.
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SIST EN 50629:2015
EN 50629:2015 (E)
Introduction
This European Standard has been prepared at the request of the European Commission under the mandate
EC 24/2011 and applies to large power transformers covered by the COMMISSION REGULATION (EU) N.
548/2014 of 21 May 2014.
For large power transformers (LPT) the strict definition of efficiency based on transmitted and absorbed active
power alone is not useful for evaluating the energy performance because the losses are either fixed (no load
loss), or depend on current (load loss) and therefore conventional efficiency would be zero if only reactive
power is transmitted (reactive power transmission is very important for network operation). The conventional
calculation of efficiency is therefore not helpful for comparing transformer designs which may be used over a
range of operating conditions.
In general for LPT it is not possible to give optimal values for load and no load losses for a particular rated
power because of the variety of applications which affect the energy performance.
In order to define an index that is specific to the transformer design, but applicable to a wide range of uses,
rather than a figure that varies from second to second depending on system conditions, it is essential to
characterize the energy performance of power transformers. For this reason a metric – Peak Efficiency Index
(PEI) – has been developed which is based on real power losses and total power transmitted and is
independent of load phase angle, load factor and rated power.
This document provides a standard method for evaluating the energy performance of power transformers
through the use of the Peak Efficiency Index, gives benchmark figures for PEI and the reasons why certain
transformers may have efficiencies which are higher or lower than the benchmark.
Setting a reasonable value of minimum Peak Efficiency Index will be effective in improving the overall
efficiency of the installed transformer population by eliminating transformers with poor efficiency, with the
exception of some transformers subject to specific limitations.
The use of a minimum value of Peak Efficiency Index sets a floor for transformer efficiency performance, but
the use of proper loss capitalisation for purchasing transformers is essential to select a transformer with the
optimal economically justified level of efficiency. Users not using loss capitalisation are strongly encouraged to
investigate the benefits of doing so.
For large units above 100 MVA the economically achievable efficiency of a transformer may be limited by the
technical parameters of the network (e.g. impedance), and specific transport and installation constraints. As
the units concerned are usually purchased by large transmission system owners, who typically use high
values of loss capitalization, those units above 100 MVA already tend to be state of the art as far as efficiency
is concerned.
For transformers with unusual configurations and/or very severe size or weight limitations it may be
unreasonable to meet the minimum efficiency requirement for either technical or economic reasons. In these
cases it will be acceptable to demonstrate that the highest reasonable level of efficiency has been achieved
(see Clause 6).
It is considered that the approach to energy performance set out in this document could also be applicable in
principle to transformers outside the scope of this standard.

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SIST EN 50629:2015
EN 50629:2015 (E)
1 Scope
This European Standard applies to new three-phase and single-phase power transformers 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.
The scope of this European Standard is the following:
- Defining the appropriate energy efficiency criteria;
- Setting of benchmark minimum efficiency levels for new transformers based on an assessment of the
energy efficiency of the European transformer population installed in the last 10 years;
- Proposing higher minimum efficiency levels for improving the energy efficiency of new transformers;
- Providing guidance for consideration of Total Cost of Ownership.
This European Standard provides also a form for efficiency data collection to inform future efficiency
benchmark levels.
NOTE 1 This standard covers the transformers under the EU Regulation N. 548/2014 and 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.
Transformers considered to be out of the scope of this document are the following:
- 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 EU
REGULATION N. 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.
For dry type large power transformers Minimum PEI values have been published in European Regulation and
these values are included in Annex A.
NOTE 2 To retain consistency, the same list of exclusions in the EU Regulation N. 548/2014, has also been
reproduced here. Within the above EU exclusion list, some had been excluded simply because no PEI data was available
to CENELEC at the time on which to base appropriate PEI levels. Consequently, as such information becomes available in
the future, it may be possible to derive suitable PEI Levels. Accordingly these particular categories are listed in Clause 6
as suitable for future consideration.
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SIST EN 50629:2015
EN 50629:2015 (E)
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 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)

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
Large Power Transformer
LPT
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
3.2
load factor
k
ratio of actual input current over the rated current of transformer
Note 1 to entry: Normally 0 ≤ k ≤ 1.
3.3
transmitted apparent power
kS
r
product of the load factor and the rated power
3.4
Efficiency Index
EI
ratio of the transmitted apparent power of a transformer minus electrical losses to the transmitted apparent
power of the transformer
3.5
Peak Efficiency Index
PEI
highest value of efficiency index that can be achieved at the optimum value of load factor
3.6
load factor of Peak Efficiency Index
k
PEI
load factor at which Peak Efficiency Index occurs
3.7
declared value
regulatory value given in Table 1 which is to be used for market surveillance activities
Note 1 to entry: According to EN 60076-1, ‘declared value’ and ‘guaranteed value’ refer to two different concepts.
‘Guaranteed Values’ relate to the values cited in the commercial contract, whereas ‘declared values’ are those values
which are cited to establish compliance with EU Regulation N. 548/2014.
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4 Efficiency and Efficiency Index calculation
4.1 General
The energy performance of a transformer can be stated in a variety of ways, principally by giving:
a) The no-load and load losses at rated load or at a particular reference power;
b) The efficiency at a defined power factor and particular load factor, for example 50 % or 100 % of rated
load;
c) The Peak Efficiency Index and the load at which it occurs.
The general definition of efficiency raises some complications such as whether the electrical consumption of
the cooling equipment of transformer at no-load or at a particular load shall be included in the calculation.
For the scope of this standard the Peak Efficiency Index has been chosen to set benchmark efficiency figures
because it does not impose a particular load factor (which may vary greatly depending on the application) and
because it does not depend explicitly on the rated power of the transformer. Peak efficiency is an intrinsic
parameter of the transformer that does not depend on whether the transformer has alternative ratings
depending on cooling modes.
The Peak Efficiency Index includes the losses associated with the cooling system that is in service in the no-
load condition. If additional cooling is required at the load factor where PEI occurs, then the additional cooling
loss required for this cooling shall be computed in the calculation of PEI. Any further additional cooling and
associated cooling loss necessary to achieve rated power is excluded.
NOTE 1 This applies to transformers equipped with heat-exchangers which need pumps and fans to provide heat
dissipation (e.g. ODAF, ODWF, OFWF, OFAF, OFAN).
NOTE 2 If the loss capitalisation method is used in the transformer procurement process, then it may be expected that
the Peak Efficiency Index will occur at approximately the loading where the ratio between load and no-load losses is equal
to the ratio between the capitalisation rates for load and no-load loss, except where this has been modified by the relative
cost of reducing load and no-load losses (See Annex D).
4.2 Efficiency Index general formula
The Efficiency Index at load factor k is calculated in accordance with Formula 1:
kS - (P +P )−(k²P+P (k))
r c0 k ck
0
𝐸𝐸(k) =   (pu) (1)
kS
r
Where
P is the no load loss measured at rated voltage and rated frequency, on the rated tap;
0
P is the electrical power required by the cooling system for no load operation, derived from the
c0
type test measurements of the power taken by the fan and liquid pump motors;
P is the measured load loss at rated current and rated frequency on the rated tap corrected to
k
reference temperature according to EN 60076-1;
P (k) is the additional electrical power required (in addition to P ) by the cooling system for
ck c0
operation at k times the rated load derived from the type test measurements of the power
taken by the fan and liquid pump motors;
S is the rated power of the transformer or autotransformer on which P is based;
r k
k is the load factor.
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EN 50629:2015 (E)
NOTE 1 This approach respects the philosophy of EN 60076 (all parts) which refers the rated power to the rated
voltage and current of one of the transformer windings.
The derivation of P at k involves establishing the total power consumption of the fans and the pumps (from
ck PEI
type test measurements) and then ascribing a proportion of this total cooling loss to that required at PEI
loading. The proportion used is the ratio of the average electrical loss of the fans and pumps used at k and
PEI
average yearly ambient temperature (20 °C unless otherwise specified) to the total electrical loss of the
pumps and fans installed.
If fans and pumps have variable speed drives, an additional type test measurement may be required to
determine P at k .
ck PEI
NOTE 2 No routine measurements of cooling power consumption are required.
For the PEI calculation, the following shall be considered.
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.
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.
For the scope of this document and for sake of simplicity it is conventionally assumed that:
- the voltage and load current systems are symmetrical and sinusoidal;
- the line voltage is equal to the rated voltage.
4.3 Peak Efficiency Index
Under the assumption that the cooling at no load is sufficient to operate at k (this assumption is used to
PEI
simplify the calculation), the load factor which maximises the Efficiency Index is given by:
P +P
0 c0
k =� (pu) (2)
PEI
P
k
For symbols meaning refer to 4.2, Formula 1.
The formula to be used for Peak Efficiency Index calculation is therefore Formula 3, which is obtained from
Formula (1) by replacing k with k as defined in Formula (2) and by assuming P (k )=0:
PEI ck PEI
2(P +P )
0 c0
PEI = 1 − (pu) (3)
P +P
0
c0
S�
r
P
k

For symbols meaning refer to 4.2, Formula 1.
NOTE 1 Demonstration of the mathematical derivation is given in B.1.
NOTE 2 An example is given in B.2.2.
As mentioned in 4.1, if additional cooling is required at the load factors where PEI occurs, then the assumption
P (k ) = 0 does not hold, then the term P (k ) shall be added to P in the formula for PEI for the
ck PEI ck PEI c0
transformers in the scope of this standard.
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EN 50629:2015 (E)
2[P +P +P (𝑘 )]
0 c0 ck 𝑃𝑃𝑃
PEI = 1 − (pu) (4)
�P +P +P (𝑘 )�
0 c0 ck 𝑃𝑃𝑃
S�
r
P
k
NOTE 3 An example is given in B.2.3.
⁄
NOTE 4 The value of Formula 3 depends on the ratio 𝑆 �𝑃 which does not vary significantly if S is changed (for
r
𝑟 𝑘
example by changing cooling mode) provided P is measured at S .
k r

5 Minimum Peak Efficiency Index values
5.1 Standardised values of Minimum PEI
The Minimum Peak Efficiency Index values for liquid immersed transformers are given in Table 1 and those
for dry
...