548/2014 - Commission Regulation (EU) No 548/2014 of 21 May 2014 implementing Directive 2009/125/EC of the European Parliament and of the Council with regard to small, medium and large power transformers

TC - Correction of technical errors

TC - Correction of technical errors

The scope of this document is to define the energy performance of Medium Power Transformers in compliance with prEN 50708-1-1:2019.

This document is part of the of the EN 50708 series which applies to transformers in compliance with EN 60076 1.

The scope of this document is to define performance requirements of Large Power Transformers in compliance with prEN 50708 1 1:2019.
NOTE    This document covers the transformers under the EU Regulation N. 548/2014 and Amendment of 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.

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 indications for single phase transformers, auto transformers, multi winding transformers and for transformers with OD and OF cooling systems.
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.

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 indications for single phase transformers, auto transformers, multi winding transformers and for transformers with OD and OF cooling systems. 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.

This European Standard gives Ecodesign requirements for small power transformers complying with the EN 61558 series and in relation to Commission Regulation (EU) N° 548/2014 implementing the European Directive 2009/125/EC.
This European Standard is applicable to transformers with 50 Hz AC input and output with a rated power of 1 kVA or more and a voltage lower than 1 kV, except those excluded in the regulation.
For transformers with a voltage between 1 kV and 1,1 kV, this standard may be used as a guide.

This European Standard gives Ecodesign requirements for small power transformers complying with the EN 61558 series and in relation to Commission Regulation (EU) N° 548/2014 implementing the European Directive 2009/125/EC. This European Standard is applicable to transformers with 50 Hz AC input and output with a rated power of 1 kVA or more and a voltage lower than 1 kV, except those excluded in the regulation. For transformers with a voltage between 1 kV and 1,1 kV, this standard may be used as a guide.

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 to 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:
a)   instrument transformers, specifically designed to supply measuring instruments, meters, relays and other similar apparatus;
b)   transformers with low-voltage windings specifically designed for use with rectifiers to provide a DC supply;
c)   transformers specifically designed to be directly connected to a furnace;
d)   transformers specifically designed for offshore applications and floating offshore applications;
e)   transformers specially designed for emergency installations;
f)   transformers and auto-transformers specifically designed for railway feeding systems;
g)   earthing or grounding transformers, this is, three-phase transformers intended to provide a neutral point for system grounding purposes;
h)   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;
i)   starting transformers, specifically designed for starting three-phase induction motors so as to eliminate supply voltage dips;
j)   testing transformers, specifically designed to be used in a circuit to produce a specific voltage or current for the purpose of testing electrical equipment;
k)   welding transformers, specifically designed for use in arc welding equipment or resistance welding equipment;
l)   transformers specifically designed for explosion-proof and underground mining applications;
m)   transformers specifically designed for deep water (submerged) applications;
n)   medium Voltage (MV) to Medium Voltage (MV) interface transformers up to 5 MVA;
o)   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;
p)   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.
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.
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.

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 to 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: a) instrument transformers, specifically designed to supply measuring instruments, meters, relays and other similar apparatus; b) transformers with low-voltage windings specifically designed for use with rectifiers to provide a DC supply; c) transformers specifically designed to be directly connected to a furnace; d) transformers specifically designed for offshore applications and floating offshore applications; e) transformers specially designed for emergency installations; f) transformers and auto-transformers specifically designed for railway feeding systems; g) earthing or grounding transformers, this is, three-phase transformers intended to provide a neutral point for system grounding purposes; h) 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; i) starting transformers, specifically designed for starting three-phase induction motors so as to eliminate supply voltage dips; j) testing transformers, specifically designed to be used in a circuit to produce a specific voltage or current for the purpose of testing electrical equipment; k) welding transformers, specifically designed for use in arc welding equipment or resistance welding equipment; l) transformers specifically designed for explosion-proof and underground mining applications; m) transformers specifically designed for deep water (submerged) applications; n) medium Voltage (MV) to Medium Voltage (MV) interface transformers up to 5 MVA; o) 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; p) 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. 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. 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.

IEC 60076-10:2016 defines sound pressure and sound intensity measurement methods from which sound power levels of transformers, reactors and their associated cooling devices are determined. The methods are applicable to transformers, reactors and their cooling devices - either fitted to or separate from the transformer - as covered by the IEC 60076 and IEC 61378 series. This standard is primarily intended to apply to measurements made at the factory. Conditions on-site can be very different because of the proximity of objects, including other transformers. Nevertheless, this standard is applied to the extent possible for on site measurements. This edition includes the following significant technical changes with respect to the previous edition: - additional useful definitions introduced; - definition of distribution type transformers introduced for the purpose this standard; - new clause for sound level measurement specification introduced; - requirement for 1/3 octave band measurements introduced for transformers other than distribution type transformers; - standard measurement distance changed from 0,3 m to 1 m for transformers other than distribution type transformers; - height of measurement surface is now clearly defined to count from the reflecting plane; - measurement surface formula unified; - correction criteria for intensity method introduced; - rules for sound measurements on dry-type reactors introduced; - figures revised; - new informative test report templates introduced (Annex B); - IEC 60076-10-1 (application guide) revised in parallel providing worthwhile information for the use of this standard.

EN 50629 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.

To improve the definitions of transformers excluded from the COMMISSION REGULATION (EU) No 548/2014 as well as any other definition requiring further clarification

This European Standard applies to new three-phase and single-phase power transformers with Um > 36 kV.
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.
Transformers considered to be out of the scope of this document are the following:
•   Instrument transformers;
•   Earthing transformers;
•   Traction transformers on rolling stock;
•   Starting transformers;
•   Testing transformers;
•   Welding transformers;
•   Explosion-proof and underground mining transformers;
•   Transformers for deep water (submerged) applications.

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 indications for single phase transformers, auto transformers, multi winding transformers and for transformers with OD and OF cooling systems. 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.

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.

The scope of this document is to define the energy performance of Medium Power Transformers in compliance with EN 50708-1-1:2020.

TC - Correction of technical errors

This document is part of the EN 50708 series which applies to transformers in compliance with EN 60076-1.

TC - Correction of technical errors

EN 50588-1 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.

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
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.

To improve the definitions of transformers excluded from the COMMISSION REGULATION (EU) No 548/2014 as well as other definitions requiring further clarification

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 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.