SIST EN 50588-1:2015

SLOVENSKI STANDARD
SIST EN 50588-1:2015
01-september-2015
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SIST EN 50464-1:2007
SIST EN 50464-1:2007/A1:2012
SIST EN 50541-1:2011
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Medium power transformers 50 Hz, with highest voltage for equipment not exceeding 36
kV - Part 1: General requirements
Mittelleistungstransformatoren 50 Hz, mit einer höchsten Spannung für Betriebsmittel
nicht über 36 kV - Teil 1: Allgemeine Anforderungen
Transformateurs 50 Hz de moyenne puissance, de tension la plus élevée pour le
matériel ne dépassant pas 36 kV - Partie 1: Exigences générales
Ta slovenski standard je istoveten z: EN 50588-1:2015
ICS:
29.180 Transformatorji. Dušilke Transformers. Reactors
SIST EN 50588-1:2015 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 50588-1:2015

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SIST EN 50588-1:2015


EUROPEAN STANDARD EN 50588-1

NORME EUROPÉENNE

EUROPÄISCHE NORM
June 2015
ICS 29.180 Supersedes EN 50464-1:2007, EN 50541-1:2011
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 Mittelleistungstransformatoren 50 Hz, mit einer höchsten
la plus élevée pour le matériel ne dépassant pas 36 kV - Spannung für Betriebsmittel nicht über 36 kV - Teil 1:
Partie 1: Exigences générales 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
© 2015 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
 Ref. No. EN 50588-1:2015 E

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

Contents
Foreword .4
1 Scope .5
2 Normative references .6
3 Terms and definitions .6
4 Environmental classes .7
5 Electrical characteristics .7
5.1 Highest voltages for equipment for winding with U > 1,1 kV .7
m
5.2 Rated voltage for winding with U ≤ 1,1 kV .7
m
5.3 Tapping .8
5.4 Connection designations for three phase transformers .8
6 Load loss, no load loss, PEI, sound power level, short-circuit impedance .8
6.1 General .8
6.2 Transformers with rated power S ≤ 3 150 kVA .9
r
6.2.1 General information .9
6.2.2 One winding with U ≤ 24 kV and the other one with U ≤ 1,1 kV . 10
m m
6.2.3 Load loss and no load loss in case of other insulation level . 12
6.2.4 Load loss and no load loss in case of dual voltage . 12
6.3 Transformers with rated power 3 150 kVA < S < 40 000 kVA . 13
r
6.4 Transformers with special requirements . 14
6.4.1 Rated power not included in the list . 14
6.4.2 Transformers equipped with tapping connections suitable for operation
while transformer is energised or on load and rated power S
r
≤ 3 150 kVA . 14
6.4.3 Liquid immersed pole mounted transformers . 15
6.4.4 PEI values for single-phase liquid immersed transformers with
Sr ≤ 100 kVA . 16
7 Tolerances . 16
7.1 Tolerances during factory acceptance tests . 16
7.1.1 General . 16
7.1.2 Transformers subject to maximum losses . 16
7.1.3 Transformers subject to minimum PEI . 16
7.2 Tolerances for Market surveillance . 16
7.2.1 Acceptance criteria . 16
7.2.2 Transformers subjected to max losses . 17
7.2.3 Transformers subjected to PEI . 17
7.3 Uncertainties for market surveillance verification . 17
8 Rating plate. 18
9 Tests . 18
9.1 Routine tests . 18
9.2 Type tests . 18
9.3 Special tests . 18
9.4 Special test for corrugated tank . 18
9.4.1 General information . 18
9.4.2 Temperature variation . 18
2

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SIST EN 50588-1:2015
EN 50588-1:2015 (E)
9.4.3 Sealing temperature . 19
9.4.4 Calculation of the volume variation . 19
9.4.5 Test procedure . 19
9.5 Other technologies with level of no load loss AAA . 20
0
10 Design requirements . 20
10.1 Liquid immersed transformers . 20
10.1.1 Type of liquid preservation system and degree of sealing . 20
10.1.2 Terminal markings . 20
10.1.3 Terminations . 21
10.1.4 Distance between bushings . 21
10.1.5 Rollers . 21
10.2 Dry-type transformers . 21
10.2.1 Terminals . 21
10.2.2 Enclosure . 21
11 Accessories . 22
11.1 Liquid immersed transformers . 22
11.2 Dry-type transformers . 22
Annex A (informative) Calculation of PEI and k . 24
PEI
A.1 Calculation of Peak Efficiency Index. 24
A.2 Calculation of k . 24
PEI
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 . 26
Bibliography . 29

3

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

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.
4

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SIST EN 50588-1:2015
EN 50588-1:2015 (E)
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 U = 38,5 kV or U = 40,5 kV). This is
m m
considered to be an unusual case of a large power transformer, where the requirements are those
for a medium power transformer with U = 36 kV.
m
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
EN 50629.
NOTE 2 Transformers with tap changer (DETC or OLTC) are included in this European Standard even if
they have separate tapping winding.
The object of this European Standard is to set up requirements related to electrical characteristics
and design of medium power transformers.
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

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SIST EN 50588-1:2015
EN 50588-1:2015 (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 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
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.
3.2
transmitted apparent power
kS
r
product of the load factor and the rated power
6

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SIST EN 50588-1:2015
EN 50588-1:2015 (E)
3.3
Efficiency Index
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.

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
5.1 Highest voltages for equipment for winding with U > 1,1 kV
m
Insulation levels and dielectric test shall be in accordance with the requirements of EN 60076-3.
The values of the highest voltage U for equipment are:
m
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 U = 38,5 kV or U = 40,5 kV).
m m

5.2 Rated voltage for winding with U ≤ 1,1 kV
m
For U ≤ 1,1 kV the preferred rated voltage value shall be chosen in the hereunder list:
m
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.
7

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SIST EN 50588-1:2015
EN 50588-1:2015 (E)
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
S ≤ 100 kVA 100 kVA < S < 5 000 kVA S ≥ 5 000 kVA
r r r
YNd or Dyn or YNyn
Yzn or Dyn Dyn

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 S ≤ 100kVA, for three phase transformers with a rated power S ≤ 3 150 kVA and minimum
r r
Peak Efficiency Index for three phase transformers with rated power S > 3 150 kVA and
r
S < 40 000 kVA.
r
The losses and Peak Efficiency Index classes remain the same for all highest voltage for equipment
values (U ) regardless of the additional loss corrections specified in 6.2.3 and 6.2.4.
m
Description and requirements for special cases are given in 6.4.
8

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SIST EN 50588-1:2015
EN 50588-1:2015 (E)
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 AAA , then AA , then A . For load
0 0 0
loss the same logic is used with the most efficient class is A , then B , then C .
k k k
The names of the loss classes are the same for all of the highest voltage for equipment values (U )
m
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).
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 transformer
according to EN 60076-2, EN 60076-11 and EN 60076-14.
The symbols used are:
P : no load loss at rated voltage and rated frequency, on the rated tap according to EN 60076-1;
0
P : load loss at rated current and rated frequency on the rated tap corrected to reference
k
temperature according to EN 60076-1;
L : A weighted sound power level of transformers according to EN 60076-10.
WA
6.2 Transformers with rated power S ≤ 3 150 kVA
r
6.2.1 General information
Figure 1 indicates clauses to be chosen according to the highest voltage for equipment values U
m
on the primary and on the secondary windings.

Figure 1 — Choice of clauses according to the highest voltage for equipment values U
m
Numbering into brackets are the references to the lines of Table 5.
9

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SIST EN 50588-1:2015
EN 50588-1:2015 (E)
The level of losses shall be matched to the highest voltage for equipment (U ) according to
m
Figure 1.
NOTE Higher insulation levels are usually associated with higher clearance which in turn involves higher
level of losses.
6.2.2 One winding with U ≤ 24 kV and the other one with U ≤ 1,1 kV
m m
The following tables are defined for step down or step up transformer with one winding with
U ≤ 24 kV and the other one with U ≤ 1,1 kV.
m m
Table 2 and Table 3 are for liquid immersed transformers and Table 4 for dry-type transformers.
For the transformers AAA see special requirements in 9.5.
0
Table 2 — No load loss (P ) and sound power level for liquid immersed transformers
0
Rated AAA AA L A L
0 0 WA 0 WA
power
kVA W W dB(A) W dB(A)
≤ 25 35 63 36 70 37
50 45 81 38 90 39
100 75 130 40 145 41
160 105 189 43 210 44
250 150 270 46 300 47
315 180 324 48 360 49
400 220 387 49 430 50
500 260 459 50 510 51
630 300 540 51 600 52
800 330 585 52 650 53
1000 390 693 54 770 55
1250 480 855 55 950 56
1600 600 1080 57 1200 58
2000 730 1305 59 1450 60
2500 880 1575 62 1750 63
3150 1100 1980 63 2200 64

The sound power level L for transformers AAA has to be agreed between manufacturer and
WA 0
purchaser.

10

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SIST EN 50588-1:2015
EN 50588-1:2015 (E)
Table 3 — Load loss (P ) and short circuit impedance for liquid immersed transformers
k
Rated power A B C Short-circuit Impedance
k k k
kVA W W W %
≤ 25 600 725 900 4
50 750 875 1100 4
100 1250 1475 1750 4
160 1750 2000 2350 4
250 2350 2750 3250 4
315 2800 3250 3900 4
400 3250 3850 4600 4
500 3900 4600 5500 4
630 4600 5400 6500 4 or 6
800 6000 7000 8400 6
1000 7600 9000 10500 6
1250 9500 11000  6
1600 12000 14000  6
2000 15000 18000  6
2500 18500 22000  6
3150 23000 27500  6
Table 4 — Losses, short circuit impedance and sound power levels for dry-type
transformers
Rated power P P P L Short-circuit
k 0 0 WA
Impedance
A B AAA AA A
k k 0 0 0

kVA W W W W dB (A) W dB (A) %
≤ 50 1500 1700 115 180 48 200 49 6
100 1800 2050 160 252 50 280 51 6
160 2600 2900 230 360 53 400 54 6
250 3400 3800 300 468 56 520 57 6
400 4500 5500 430 675 59 750 60 6
630 7100 7600 630 990 61 1100 62 6
800 8000 750 1170 63 1300 64 6
1000 9000 890 1395 64 1550 65 6
1250 11000 1035 1620 66 1800 67 6
1600 13000 1265 1980 67 2200 68 6
2000 16000 1495 2340 69 2600 70 6
2500 19000 1780 2790 70 3100 71 6
3150 22000 2185 3420 73 3800 74 6
11

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SIST EN 50588-1:2015
EN 50588-1:2015 (E)
Transformers can be requested and offered with sound power level L other than the listed values.
WA
The sound power level L for transformers AAA has to be agreed between manufacturer and
WA 0
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 Correction of load loss and no load loss
values.
1 One winding with The maximum levels of losses indicated in Table 2, Table 3
1,1 kV < U ≤ 24 kV and the and Table 4 can be increased by 10 % for no load loss and
m
other with by 10 % for load loss.
1,1 kV < U ≤ 24 kV
m
2 One winding with The maximum levels of losses indicated in Table 2, Table 3
24 kV < U ≤ 36 kV and the
and Table 4 can be increased by 15 % for no load loss and
m
other with U ≤ 1,1 kV by 10 % for load loss and short circuit impedance unless
m
otherwise specified should be increased by adding a value
of 0,5 %.
3 One winding with The maximum levels of losses indicated in Table 2, Table 3
24 kV < U ≤ 36 kV and the and Table 4 can be increased by 20 % for no load loss and
m
other with U > 1,1 kV by 15 % for load loss and short circuit impedance unless
m
otherwise specified should be increased by adding a value
of 0,5 %.
6.2.4 Load loss and no load loss in case of dual voltage
The level of losses given in 6.2.2 shall be weighted by the correction factors given in Table 6 below,
in order to take car
...