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1/55

echnical Study Report

ENERGY EFFICIENT

TRANSFORMERS


2/55Energy Efficient Transformers

This report was produced under the project entitled Supporting Action

on Climate Change through a Network of National Climate Change Focal

Points in South-east Asia (SEAN-CC) implemented by UNEP and funded by

Ministry of Foreign Affairs of the Government of Finland.Dec 2011



SECTION 1: INTRODUCTION 2

1.1 ype of ransformers 21.2 Substation ransformers 21.3 Distribution ransformers 71.4 Energy Savings Outlook 8

SECTION 2: DESCRIBE THE PROPOSED TECHNOLOGY 112.1 ransformer Efficiency 122.2 ransformer Losses 122.3 raditional echnologies 132.4 Cost Economics 16

SECTION 3: REQUIREMENTS OF THE TECHNOLOGY 20

INTERVENTION3.1 New echnology Awareness and Acceptance 213.2 Contribution to Energy Efficiency and Global Warming Goals 223.3 Characterization of the Utility Market 22

3.4 National/International Policies and Initiatives 233.5 Potential Mechanisms for Change 243.6 International Perspective 24

SECTION 4: ANALYSIS, RECOMMENDATIONS AND 31

ACTION PLANS4.1 Use of High-efficiency ransformers 324.2 Amorphous ransformers 37

4.3 Running Cool for Lower Energy Costs 424.4 Projected Energy Savings Using Metglas AMDs 424.5 Superconducting ransformers 43

SECTION 5: FOLLOW-UP TO THE TECHNOLOGY 45

5.1 Research & Development 465.2 Energy Efficient Distribution ransformers rends 475.3 Some of the Short erm and Long erm Measures aken by BEE 53

5.4 Policies & Regulations 52

Contents



SECION1

1



Section1

INTRODUCTION

Before invention of transformers, in initial days of electrical industry, power was distributed as direct

current at low voltage. Te voltage drop in lines limited the use of electricity to only urban areas where

consumers were served with distribution circuits of small length. All the electrical equipment had to be

designed for the same voltage. Development of the first transformer around 1885 dramatically changed

transmission and distribution systems. Te alternating current (AC) power generated at a low voltage

could be stepped up for the transmission purpose to higher voltage and lower current, reducing voltage

drops and transmission losses. Use of transformers made it possible to transmit the power economically

hundreds of kilometers away from the generating station. Step-down transformers then reduced the

voltage at the receiving stations for distribution of power at various standardized voltage levels for its

use by the consumers. ransformers have made AC systems quite flexible because the various parts and

equipment of the power system can be operated at economical voltage levels by use of transformers

with suitable voltage rating. Te voltage levels are different in different countries depending upon their

system design. ransformers can be broadly classified, depending upon their application as given below.

1.1 Types of Transformers

1.1.1 Power Transformers

ANSI/IEEE defines a transformer as a staticelectrical device, involving no continuouslymoving parts, used in electric power systems totransfer power between circuits through the useof electromagnetic induction. Te term powertransformer is used to refer to those transformers

used between the generator and the distributioncircuits, and these are usually rated at 500 KVAand above. Power systems typically consist of alarge number of generation locations, distributionpoints, and interconnections within the system orwith nearby systems, such as a neighboring utility.Te complexity of the system leads to a varietyof transmission and distribution voltages. Powertransformers must be used at each of these points

where there is a transition between voltage levels.

Fig. 1.1.1 Power Transformer

2



Section1

1.1.2 Distribution Transformers

In 1886, George Westinghouse built the firstlong-distance alternating-current electric lightingsystem in Great Barrington, MA. Te powersource was a 25-hp steam engine driving an

alternator with an output of 500 V and 12 A. Inthe middle of town, 4000 ft away, transformerswere used to reduce the voltage to serve lightbulbs located in nearby stores and offices (Powel,1997).

Any transformer that takes voltage from aprimary distribution circuit and steps downor reduces it to a secondary distribution circuit

or a consumers service circuit is a distributiontransformer. Although many industry standardstend to limit this definition by KVA rating (e.g.,5 to 500 KVA), distribution transformers canhave lower ratings and can have ratings of 5000KVA or even higher, so the use of KVA ratingsto define transformer types is being discouraged(IEEE, 2002b).

1.1.3 Phase-Shifting Transformers

Te necessity to control the power flow roseearly in the history of the development ofelectrical power systems. When high-voltagegrids were superimposed on local systems,

parallel-connected systems or transmission linesof different voltage levels became standard.Nowadays large high-voltage power grids areconnected to increase the reliability of theelectrical power supply and to allow exchangeof electrical power over large distances.Complications, attributed to several factors suchas variation in power generation output and/orpower demand, can arise and have to be dealt

with to avoid potentially catastrophic systemdisturbances. Additional tools in the form ofphase-shifting transformers (PSs) are availableto control the power flow to stabilize the grids.Tese may be justified to maintain the requiredquality of the electrical power supply.

1.1.4 Rectifier Transformers

Power electronic circuits can convert alternatingcurrent (ac) to direct current (dc). Tese are calledrectifier circuits. Power electronic circuits can alsoconvert direct current to alternating current. Teseare called inverter circuits. Both of these circuitsare considered to be converters. A transformer thathas one of its windings connected to one of thesecircuits, as a dedicated transformer, is a convertertransformer, or rectifier transformer. IEC

standards refer to these transformers as convertertransformers, while IEEE standards refer to thesetransformers as rectifier transformers. Becauseit is IEEE practice to refer to these transformersas rectifier transformers, that same term isused throughout this discussion. ransformersconnected to circuits with a variety of loads,but which may contain some electronic circuitsthat produce harmonics, are not considered to

be rectifier transformers. However, they mayhave harmonic heating effects similar to rectifiertransformers. Tose transformers are coveredunder IEEE.

Fig. 1.1.2 Three-Phase Distribution Transformer

Fig. 1.1.3 Quadrature booster set (300 MVA, 50 Hz,40012*1.25%/11512*1.45 kV).

3



Section1

Recommended Practice for Establishingransformer Capability when Supplying Non-Sinusoidal Load Currents, ANSI/IEEE C57.110.

Fig. 1.1.4 A 12-pulse Circuit 31 5450-kVA, 4160-V delta primary to2080-V delta and wye secondaries, cast coil transformer in case.

1.1.5 Dry-Type Transformers

A dry-type transformer is one in which theinsulating medium surrounding the windingassembly is a gas or dry compound. Basically, anytransformer can be constructed as dry as long as

the ratings, most especially the voltage and KVA,can be economically accommodated without theuse of insulating oil or other liquid media. Tissection covers single- and three-phase, ventilated,non-ventilated, and sealed dry type transformerswith voltage in excess of 600 V in the highest-voltage winding.

Fig. 1.1.5 Cast Resin Dry Type Transformer

Many perceptions of dry-type transformersare associated with the class of design byvirtue of the range of ratings or end-useapplications commonly associated withthat form of construction Of course, the

fundamental principles are no different fromthose encountered in liquid-immersed designs,as discussed in other chapters. Considerationsinvolving harmonics are especially notable in thisregard.

Consequently, this chapter is brief, expoundingonly on those topics that are particularly relevantfor a transformer because it is dry.

1.1.6 Instrument Transformers

Instrument transformers are primarily used toprovide isolation between the main primarycircuit and the secondary control and measuringdevices. Tis isolation is achieved by magneticallycoupling the two circuits. In addition to isolation,levels in magnitude are reduced to safer levels.

Instrument transformers are divided into twocategories: voltage transformers (V) and currenttransformers (C). Te primary winding of theV is connected in parallel with the monitoredcircuit, while the primary winding of the Cis connected in series. Te secondary windingsproportionally transform the primary levels totypical values of 120 V and 5 A. Monitoring

devices such as watt-meters, power-factor meters,voltmeters, ammeters, and relays are oftenconnected to the secondary circuits.

4



Section1

Fig. 1.1.6 (a) 69-kV single-bushing VT,(b) High-voltage wound-type CT in combination steel tank, oil, and porcelain construction.

(a) (b)

5



Section1

1.1.7 Step-Voltage Regulators

Distribution systems must be designed in sucha way that voltage magnitudes always remainwithin a specified range as required by standards.Tis is accomplished through the use of voltage-

control equipment and effective system design.Regulating power transformers (load-tap-changing transformers, or LCs), three-phasestep-voltage regulators, single-phase step-voltageregulators, and Auto-Boosters are typicaltransformer-type equipment used to improve thevoltage profile of a power system.

Fig. 1.1.7 Single Phase Auto Booster Four-Step VoltageRegulator

1.1.8 Constant-Voltage Transformers

Constant-voltage transformers (CV) havebeen used for many years, primarily as a noise-isolation device. Recently, they have found valuewhen applied as a voltage-sag protection device

for industrial and commercial facilities. Teindustrial use of constant-voltage transformers(also called CVs and ferroresonant transformers)goes back to the early 1940s. Joseph G. Sola,a German-born engineer, discovered the CVtechnology [1,2] based on a single transformerrather than an arrangement of transformers,separate filters, and capacitors. Tis innovationprovides several important advantages: its

inherent robustness (CV consists of just threeor four windings and a high-reliability capacitor),its imperviousness to continuous short circuits(whether it is turned on into a short circuit orfrom full load), and its capability to maintainoutput-voltage stabilization on a cycle-to-cyclebasis for significantly large overvoltages andundervoltages.

Fig. 1.1.8 Components of a typical constant-voltage transformer.

Single-phase step-voltage regulators maintain aconstant voltage by on-load voltage regulationwherever the voltage magnitude is beyondspecified upper and lower limits. A commonpractice among utilities is to stay within preferredvoltage levels and ranges of variation as set forthby ANSI 84.1, Voltage Rating for Electric PowerSystems and Equipment.

PrimarySection ofthe Core

Air Gap

ResonatingWinding

SecondarySection ofthe Core

ResonantCapacitor

SecondaryWinding

MagneticShunt

PrimaryWinding

6



Section1

Commercial

DistributionTransformer

Substation Transformer

Industrial Agricultural

Resident

Fig. 1.2 Electrical Distribution System

1.2 Substation Transformers

A substation is a high-voltage electric facility. It isused to switch generators, equipment and circuitsor lines in and out of system. A Substation is alsoused to change AC voltages from one level toanother, or change alternating current to directcurrent or direct current to alternating current.Tere are small substations and large one. Tesmall substation are little more than a transformerand relate switches, while the large one hasseveral transformers an dozens of switches andequipment.

Tere are generally four types of substation, butsome substations there are a combination of twoor more types.

Substation Transformer Types

Step-Up ransmission Substations Step-Down ransmission Substation Distribution Substation Underground Distribution Substation

1.3 Distribution Transformers

Distribution transformers: Using distributiontransformers, the primary feeder voltage isreduced to actual utilization voltage (~415 or 460V) for domestic/ industrial use. A great variety oftransformers fall into this category due to manydifferent arrangements and connections. Loadon these transformers varies widely, and they areoften overloaded. A lower value of no-load loss is

desirable to improve all-day efficiency. Hence, theno-load loss is usually capitalized with a high rateat the tendering stage. Since very little supervisionis possible, users expect the least maintenanceon these transformers. Te cost of supplyinglosses and reactive power is highest for thesetransformers.

7



Section1

1.4 Energy Savings Outlook

ransformers typically can be expected to operate20-30 years or more, so buying a unit based onlyon its initial cost is uneconomical and foolish.ransformer life-cycle cost (also called total

cost of ownership) takes into account not onlythe initial transformer cost but also the cost tooperate and maintain the transformer over itslife. Tis requires that the total owning cost(CO) be calculated over the life span of thetransformer. With this method, it is now possibleto calculate the real economic choice betweencompeting models. (Tis same method can beused to calculate the most economical total costof ownership of any long-lived device and tocompare competing models on the same basis.)Te CO method not only includes the value ofpurchase price and future losses but also allowsthe user to adjust for tax rates, cost of borrowingmoney, different energy rates, etc.

1.4.1 Why focus on distribution

transformers?

Energy losses throughout the worlds electricaldistribution networks amount to 1 279 Wh.Tey vary from country to country between3.7% and 26.7% of the electricity use,which implies that there is a large potentialfor improvement. After lines, distributiontransformers are the second largest loss-

making component in electricity networks.ransformers are relatively easy to replace,certainly in comparison with lines or cables,and their efficiency can fairly easily be classified,labeled and standardized. Moreover, moderntechnology exists to reduce losses by up to 80%.Te worldwide electricity savings potential ofswitching to high efficiency transformers isestimated to be at least 200 Wh, equivalent to

the Benelux electricity consumption. Tis savingspotential is not only technically advantageous,but also brings economic and environmental

benefits. aking the full life cycle cost intoaccount, selecting high efficiency transformersis normally an economically sound investmentdecision despite their higher purchase price. Asa result, high efficiency transformers yield a neteconomic gain for global society. A reductionof energy consumption is also an importantadvantage for the worlds environment { not leastbecause of the resulting reduction in greenhousegas emissions.

With this savings potential available, seven ofthe largest economies in the world have beentaking actions to improve transformer efficiency:Australia, China, Europe, Japan, Canada and the

USA. Tey have set up programs { mandatoryor voluntary { based on minimum standards orefficiency labels. Up to now, the programs inAustralia, China, India and Japan are the mostadvanced.

1.4.2 Network Losses

Losses of the electricity network world-wide

can be estimated at 1 279 Wh, or 9.2% ofelectricity use. While some level of losses isinevitable, tables 1.4.1 and 1.4.2 show a variationin losses from less than 4% to more than 20%.Tis variation cannot be explained alone bysize of country, size of the electricity system orpopulation.

Network losses in certain countries have

decreased steadily over the past decades. Te datashows that there remains a large potential forimprovement. Network losses are important forseveral reasons. Tey represent a global economicloss of US$ 61 billion, adding unnecessarily tothe cost of electricity. Especially in developingcountries, losses use scarce generating capacity.

Over 700 million tons of greenhouse gas

emissions can be associated with these losses.able 1.4.3 shows an indicative breakdown oftransmission and distribution losses, based on alimited number of case studies:

8



Section1

ypically, a third of losses occur in transformers,and two thirds in the rest of the system.

Approximately 70% of losses occur in thedistribution system. Tere is a very high potential

for high efficiency distribution transformers, as atechnology to improve network losses. Tere areseveral good reasons for such a focus:

Distribution transformers represent the 2ndlargest loss component in the network

Replacing transformers is easier than changingcables or lines

ransformers have a large potential for loss

reduction. echnologies exist to reduce lossesby up to 80%.

Country Electricity use

(TWh)

Network losses

(TWh)

Network losses

(%)

EuropeWestern Europe

3 0462 540

222185 7.3

Former Soviet Union 1135 133 11.7

North America 4 293 305 7.1

Latin AmericaBrazil

721336

13161

18.3

AsiaJapanAus, NZChinaIndia

3 913964219

1 312497

381982194133

9.19.57.226.7

Africa / ME 826 83 10.0

otal 13 934 1 279 9.2

Table 1.4.1: Estimated network losses in the world* Leonardo Energy Transformers Leonardo-energy.org

9



Section1

Country 1980 1990 1999 2000

Finland 6.2 4.8 3.6 3.7

Netherlands 4.7 4.2 4.2 4.2

Belgium 6.5 6.0 5.5 4.8

Germany 5.3 5.2 5.0 5.1Italy 10.4 7.5 7.1 7.0

Denmark 9.3 8.8 5.9 7.1

United States 10.5 10.5 7.1 7.1

Switzerland 9.1 7.0 7.5 7.4

France 6.9 9.0 8.0 7.8

Austria 7.9 6.9 7.9 7.8

Sweden 9.8 7.6 8.4 9.1Australia 11.6 8.4 9.2 9.1

United Kingdom 9.2 8.9 9.2 9.4

Portugal 13.3 9.8 10.0 9.4

Norway 9.5 7.1 8.2 9.8

Ireland 12.8 10.9 9.6 9.9

Canada 10.6 8.2 9.2 9.9

Spain 11.1 11.1 11.2 10.6

New Zealand 14.4 13.3 13.1 11.5

Average 9.5 9.1 7.5 7.5

European Union 7.9 7.3 7.3 7.3

Table 1.4.2: Transmission and distribution losses in selected countries* Leonardo Energy Transformers Leonardo-energy.org

% of total Trans former Lin es Other

Case D DUSA - example 1USA - example 2

4.02.2

16.236.5

32.345.5

10.543.0

2.07.8

Australia - example 2.0 40.0 20.0 38.0

UK - example 1UK - example 2

8.010.0

24.032.0

21.045.0

15.043.0 2.0

Market assessment 10.0 35.0 15.0 19.0 2

Average 6.0 30.6 35.0 41.6 2.8Table 1.4.3: Breakdown of Transmission (T) & Distribution (D) losses* Leonardo Energy Transformers Leonardo-energy.org

10



SECION2

11



Section2

2.1 Transformer Efficiency

Te efficiency of a transformer, like any otherdevice, is defined as the ratio of useful outputpower to input power.

Te percentage efficiency of a transformer isin the range of 95 to 99%. For large powertransformers with low loss designs, the efficiencycan be as high as 99.7%.

Tere is a possibility of error if the efficiency is

determined from the measured values of outputand input powers, as the wattmeter readings mayhave an error of about 1%. Hence, it is a moreaccurate approach if the efficiency is determinedusing the measured values of losses by the opencircuit and short circuit tests.

Although the load power factor has some effect

on the mutual flux and hence the core loss, theeffect is insignificant, allowing us to assume thatthe core loss is constant at all the load conditions.Although the efficiency of a transformer is givenby the ratio of output power to input power,there are some specific applications of transformerin which its performance cannot be judged onlyby this efficiency. Distribution transformers, forexample, supply a load which varies over a wide

range throughout the day. For such transformers,the parameter all-day efficiency is of morerelevance. Te output and losses are computedfor a period of 24 hours using the load cycle.No-load losses are constant (independent ofload); hence it is important to design distributiontransformers with a lower value of no-load lossesso that a higher value of all day energy efficiencyis achieved.

DESCRIBE THE PROPOSED TECHNOLOGY

2.2 Transformer Losses

Tere are three different types of losses:

No-load loss (also called iron loss or core loss):Caused by the hysteresis and eddy currents inthe core. It is present whenever the transformeris connected, and independent of the load. Itrepresents a constant, and therefore significant,energy drain.

Load loss (or copper loss or short circuit loss):Caused by the resistive losses in the windingsand leads, and by eddy currents in the

structural steelwork and the windings. It varieswith the square of the load current.

Cooling loss (only in transformers with fancooling): Caused by the energy consumptionof a fan. Te bigger the other losses, the morecooling is needed and the higher the coolingloss. Tese losses can be avoided if operationaltemperature is kept low by different loss

reduction measures.

2.2.1. Transformer Losses Standards

Tere are European specifications for powersystems transformers, which set standards forperformance, including power losses. Tese haveconsolidated earlier national standards, and arecompatible with International ElectrotechnicalCommission (IEC) world standards. Tey have

been developed by the European Committee forElectrotechnical Standardisation (CENELEC), inconsultation with UNIPEDE.

Te distribution transformer standards applicablewithin EU are all documented. Non-utilityoutdoor distribution transformers are superficiallyvery similar to utility transformers, but thespecifications and sizes may be different. For

example, many European railways are suppliedat 15kV, 162/3Hz, single phase. Miningtransformers are often flameproof.

12



Section2

Distribution transformers with conventionaloil cooling and installed on indoor sites, forexample the basement of a large commercialbuilding, are considered to pose a possiblefire risk. Tey are required by the building

regulations in many EU countries either to usenon-flammable coolants, or to be dry-type,without coolants. Polychlorinated biphenyls(PCBs), the principal coolant used in the past,have been linked with the production of highlytoxic chlorine compounds, mainly dioxins, athigh temperatures. Non-toxic coolants are nowavailable, and cast resin clad transformers offer analternative to dry-type construction. Reliability

is reported to be the main factor influencing theway in which distribution transformers are chosenby consulting engineers and non-utility sectorcustomers. Teir installations are relatively smallin scale, and unlike utility networks may haveonly limited back-up in the case of transformerfailure.

2.3 Traditional Technologies

2.3.1 Distribution TransformerTechnology

1) Design Concepts

ransformer design is extremely specialized, andrequires a capable and experienced design team.ransformers are manufactured against specificcustomer invitations to tender, taking into

account the following basic parameters:

flux density (or induction), a measure ofthe loading of the iron core. Each magneticsteel has its typical inherent core loss, directlyrelated to its flux density. Once above thesaturation induction of the steel, the fluxwill leave the core and no-load losses are nolonger under control. Maximum flux density

should therefore be limited to well belowthis saturation point. Energy-efficiency canbe improved by selecting better performing,

lower core loss steels, or by reducing fluxdensity in a specific core by increasing thecore size

current densityin the copper windings.Increasing conductor cross-section reduces

the current density. Tis will improve energyefficiency, but also result in higher cost.Because copper losses are dependent on theloading of the transformer, it is necessary toconsider how the unit is to be installed andused in practice

iron/copper balance.Te balance betweenthe relative quantities of iron and copperin the core and windings. A copper-rich

unit has a high efficiency across a wide rangeof load currents. An iron-rich unit has alower initial cost price, and may be moreeconomical when transformers are expected tobe lightly loaded.

Tese basic considerations must then becombined with a wide range of other factors,

to enable a competitive tender to be submittedto the customer. Copper and iron prices arecontinually changing, and this can affect thebalance between the two materials.

A variety of proprietary steels are available forbuilding the core, and the techniques to be usedfor the construction of the transformer core,windings, insulation and housing need to be

decided. Alternative materials, such as aluminumcoils or pre-formed copper windings, could beconsidered. Te energy efficiency of a distributiontransformer, in terms of losses, is usually specifiedby the customer.

a) ransformer Steels

Te energy efficiency of distributiontransformers is fundamentally dependent

on the type of steel used for building thetransformer core. Please see Fig 9. Morespecialized steels, particularly suitable for

13



Section2

distribution and larger transformers, havedeveloped in a number of stages.

Tin hot-rolled steel sheet, with a siliconcontent of about 3%, became the basicmaterial for fabricating electromagneticcores in about 1900. Individual sheets wereseparated by insulating layers to combine lowhysteresis losses with high resistivity. Coldrolling and more sophisticated insulationtechniques were progressively developed.Grain-oriented silicon steels, in which the

magnetic properties of transformer steels areimproved by rolling and annealing, to alignthe orientation of the grains, became availablein the mid-1950s. Various processing andcoating techniques, combined with a reducedsilicon content, were incorporated into highpermeability grain-oriented steels, about 10years later. During the 1980s, techniques wereintroduced for domain refinement, reducing

domain width by mechanical processes,principally laser-etching.

b) Grain-oriented Steels

Conventional grain-orientated (CGO) steelsare rolled from silicon- iron slabstock, and

coated on both sides with a thin layer ofoxide insulating material to reduce eddy-currents. Tey are supplied in Europe inabout 10 standard thickness. Te Europeanstandard, EN10107, reflects the internationalIEC 60404 standard, and describes a rangeof gauges from 0.23-0.50mm (previouslyM3-M7, a nomenclature which is recognizedworld-wide). CGO steels remain the standard

raw material for distribution transformermanufacture in Europe. Tey are estimatedto account for over 70% of the total steelconsumption in distribution transformerproduction, estimated at about 100,000 tonsper year. Demand is still very much skewedto the thicker gauges. Tinner gauge CGOand other more sophisticated raw materials areconsiderably more expensive, reflecting higher

capital investment and technology levels,as well as additional processing steps. Coreproduction costs are also higher.

14



Section2

High permeability steels are manufacturedto the same European Standard as CGO,and are available in about five gauges rangingfrom 0.23-0.30mm. Tey account for about20% of total consumption in transformer

manufacture.

c) Conductor

Te conductor materials for winding the coilsof distribution transformers are supplied inthe form of wire, narrow strip or sheet. Teyhave not experienced the same significant stepchanges in recent years as core steels. Te maindevelopments have been: the availability ofcopper and aluminum wire-rod produced bycontinuous casting and rolling (CCR) processes,combined with mechanized handling techniques.Tis has enabled semi-fabricators to offer wireand strip in much longer lengths than waspreviously possible, increasing transformerreliability. Te welded or brazed joints in strip,which were inevitable in rod produced from

wire-bar, created weak points in the finished coilsl both copper and aluminum are now available inwide sheet and foil form with high dimensionaltolerances. Sheet has extensively replaced strip forthe LV windings of distribution transformers.

d) Other Materials

Developments have also taken place in the other

components used in distribution transformermanufacture. Te most significant are thedevelopment of flame-proof coolants to replacePCBs, and the use of cast resin encapsulationas an alternative to dry construction in non-liquid cooled transformers. More sophisticatedinsulating papers and boards, including syntheticand self-bonding papers, are also available.

2) Coil Winding and Assembly

Te processes of winding the conductor coilsand then fitting them onto the assembled core

are labor-intensive, and require skilled workers.Again the performance and energy efficiency ofa distribution transformer greatly depends onthese steps. Mechanized winding, under operatorcontrol, is increasingly used for producing

coils based upon copper wire, wide strip andaluminum foil.

Te main types of coil which are now used indistribution transformers are: spiral sheet windings, using wide copper

strip or aluminum foil. A relatively recentdevelopment, used in place of helical coils forthe LV windings of distribution transformers,

particularly where there are only a smallnumber of turns required in the coil

multilayer coilsfor HV windings. Tecomplete winding is a single unit, wound inwire, consisting of several layers and a numberof turns per layer.

disc coils, particularly for the HV windings ofdry-type transformers. A number of radiallywound discs produced from a single lengthof conductor, separated from one another byinsulating spacers.

2.4 Cost Economics

2.4.1 Distribution TransformerStandards

Most of the characteristics of distributiontransformers are specified in national orinternational product standards. Te applicationof standards can be legally required, or by specificreference in the purchase contract.

Generally, the purpose of standards is to facilitatethe exchange of products in both home andoverseas markets, and to improve product quality,health, safety and the environment. Internationalstandards are also of importance in reducing trade

barriers. For distribution transformers purchasedin the European Union, three levels of standardsare applicable:

15



Section2

world-wide standards (ISO, IEC, ANSI) European standards and regulations (EN, HD) national standards (e.g. BSI, NF, DIN, NEN,

UNE, OEL).

European Harmonization Documents areinitiated if there is a need for a Europeanstandard. Te draft HD is a compilation of thedifferent national standards on the subject. TeHD is finalized by eliminating as many nationaldifferences as possible.

When a harmonization document (HD) hasbeen issued, conflicting national standards have

to be withdrawn within a specified period oftime, or modified to be compatible with the HD.Usually, the HD is the predecessor of an Europeanstandard (EN), which must be adopted as anational standard in the EU member countries.Tus, purchase orders which refer to nationalstandards are compatible with European standards(EN) and/or harmonization documents (HD).

Among the many international standards fordistribution transformers, two main EuropeanHarmonization Documents specify energyefficiency levels:

HD428: Tree-phase oil-immerseddistribution transformers 50Hz, from 50 to2,500kVA with highest voltage for equipmentnot exceeding 36kV

HD538: Tree-phase dry-type distributiontransformers 50Hz, from 100 to 2,500kVA,with highest voltage for equipment notexceeding 36 kV.

A separate HD is under consideration for pole-mounted transformers. In the next Section, theefficiency limits defined in these standards arediscussed. Te standards however leave considerablefreedom for local deviations in energy efficiency,which implies that energy loss levels may (and do)still vary across European countries and even inother countries. (Please see able 2.4.1)

Country /Region Standard Subject

USA Guide for Determining Energy Efficiencyfor Distribution ransformers (P1-1996). National Electrical ManufacturersAssociation. 1996. Standard est Method for Measuring the

Energy Consumption of Distributionransformers (P2-1998).

National Electrical ManufacturersAssociation. 1998. Power transformers - Application guide,

60076-8, IEC:1997

Efficiency standards and OCformula

International Design, calculation aspectsincluding measurement oflosses

Europe Cenelec 1992, Harmonization documentsHD 428, HD538 oil and dry typetransformers

Efficiency standards andcost capitalization formula

Variety of country standards defining efficiency levels; MEPS in Australia, Canada,China, Japan, Mexico, proposed in India and New Zealand, non mandatory in EuropeTable 2.4.1: Main transformer efficiency standards* Leonardo Energy Transformers Leonardo-energy.org

16



Section2

2.4.2 Life-cycle Costing

Most company structures separate the purchasingfunction from operations. Tis results in asituation where the purchase of a transformer isoften based on the delivery price only. In most

cases however, transformers with the lowestpurchase price are also the ones with the highestlosses. Since transformers have a long life span,these extra losses can add up to a considerableamount, exceeding the initial price by severaltimes.

When comparing two different types oftransformers, one should take into account the

total cost during the lifespan of the transformer,in other words, the otal Cost of Ownership(CO).

CO consists of several components: purchaseprice, installation cost, value of the energylosses and maintenance costs over its life,and decommissioning costs. Except for PCB

cooled transformers, the last two elements arerelatively insensitive to the type and design of thetransformer, and are consequently seldom takeninto account. Purchase price and energy losses arethe two key factors. When different technologiesare compared, e.g. dry-type or oil-immersed,installation costs can be considerably different,and should be taken into account.

o evaluate the total cost of losses, their NetPresent Value at the moment of purchase needsto be calculated, to put them into the sameperspective as the purchase price. Tis is doneby calculating the otal Capitalized Cost of thelosses, CCloss, calculated from the estimatedaverage cost per kWh (C), the cost of capital (r)and the life time of the transformer in years (n),where Eloss was defined.

Eloss

[kW] = (P0+ P

k* I

2) * 8760

In which: P

0is the no-load loss [kW]

Pkis the load loss [kW]

I is the rms-average load of the transformer2

8760 is the number of hours in a year

CCloss

= Eloss

* C * (1 + r)n - 1 / r * (1 + r)n

While the load profile over time and the futureprice evolution of energy is not known exactly,the use of trend line values can give goodestimates of the total cost of the losses.

2.4.3 Economic analysis of loss

reduction

Te energy efficiencies of distributiontransformers range from around 94% for a smallA-A transformer, to more than 99% for anamorphous-core distribution transformer withHD 428 C-level losses (C-AMD), the mostefficient type available.

On average, the loss in a distribution transformeris around 1.5 { 2.0% of the energy transferred.Considering that transformers are workingcontinuously, significant losses can build up. Bychoosing the right technology, these losses can bereduced by up to 80%.

As the tables below show, the pay-back period forinvesting in high efficiency transformers is relatively

short, certainly regarding their long life span (25 -30 years). Please see able 2.4.1 and 2.4.2.

1. Changing an industrial 1600 KVA transformerfrom a A-A type to a C-C type will pay back in1.4 years. Te Internal Rate of Return (IRR) forinvestments in efficient transformers is consistentlyabove 10% and sometimes as high as 70%.

2. Considering the low risk of the investment, thisshould make efficient transformers attractive toboth industrial companies and grid operators. But

17



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Efficiency class Efficiency (%)Energy saved

(kWh / year)

PaybackIRR (% -25

years)A-A 94.71 996 - -

C-C 96.46 2 277 5.0 20

A-AMD 98.71 2 310 7.7 12

C-AMD 98.77 - 8.6 11

Table 2.4.2: Energy saving & return for a high efficiency 100 kVA transformer* Leonardo Energy Transformers Leonardo-energy.org

Efficiency class Efficiency (%)Energy saved

(kWh / year)Payback

IRR (% -25

years)A-A 98.04 3 143 - -

C-C 98.64 6 833 2.8 36

A-AMD 99.35 7 085 5.7 17

C-AMD 99.40 - 6.6 15

Table 2.4.3: Energy saving & return for a high efficiency 1600 kVA transformer* Leonardo Energy Transformers Leonardo-energy.org

in the case of grid operators, there is at present noincentive to invest. Loss reduction then remains the

only factor, as they have to be covered by the gridoperators, as is the case in most countries.

2.4.4 Externalities

As shown in the previous section, a higherefficiency benefits the owner of the transformer,reducing CO. On a larger scale, those costsavings are beneficial for the whole economy,enabling the lower cost of production to result inlower tariffs to customers.

Each kWh also has an external cost, i.e. theenvironmental and health costs to society thatare not fully reflected in the price of electricity.Tese externalities originate from the varioustypes of emissions resulting from the combustionof fossil fuel. Apart from CO2, the mainoffenders are SO2 and NOx which contributeto the acidification of the environment. Tesepollutants have long range transborder effects

and have therefore become a major concern formost European countries. From table 2.4.3, theaverage external cost for the worlds generation

mix can be estimated at 5 US Cents / kWh3. Asaving of 200 Wh/year represents, in monetaryequivalent, a reduction of 10 billion US$ inenvironmental cost.

2.4.5 Non-technical losses

Distribution losses are calculated as the difference

between electricity paid by clients and energysupplied by a medium voltage transformer to thedistribution network. Losses can be technical, ornon-technical. Non-technical losses can be:

Electricity theft Invoicing errors Bankruptcies of clients Measurement errors

Electricity theft is a social problem, and hardto solve, since it addresses a large portion of

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Section2

Fuel

External Cost

US$ / kWh

Part of generation

%

Contribution

US$ / kWh

Coal 8.3 39 3.2

Oil 11.6 8 0.9

Gas 3.8 17 0.6

Nuclear 1.0 17 0.2

Hydro 0.3 17 0.1

Renewable 0.3 2.9 2 0.0

otal 100 5.0

Table 2.4.4: The external cost of electricity for the world generation mix, based on 63 studies* Leonardo Energy Transformers Leonardo-energy.org

the population in certain countries. It is notthe subject of this paper, which addressestechnological solutions to increase efficiency. But

care should be taken in interpreting loss figures todistinguish between technical and non-technicallosses.

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3.1 New Technology Awarenessand Acceptance

3.1.1 New Developments inTransformer Materials

1) Domain Refined Steels

A further reduction of losses is achieved bydomain limitation. Domain refined steels areproduced mainly by proprietary laser etchingprocesses. ogether with grain-oriented steel,they offer material with specific losses ranging

from about 0.85-1.75W/kg at 1.7/50Hz fordistribution transformer manufacture.

Commercially available domain-refined steelis typically 0.23mm thick. ogether withamorphous iron, see below, it has a market sharein Europe for transformer manufacture of about10%.

2) Amorphous Iron

Distribution transformers built with amorphousiron cores can have more than 70% reduction inno-load losses compared to the best conventionaldesigns. Tere is only one known producerworld-wide of amorphous iron material suitablefor distribution transformer manufacture.Amorphous iron became commercially available

in the early 1980s. It is reported to have beenused in the construction of several hundredthousand distribution transformers in the US,Japan, India and China. European experience ofmanufacturing and installing amorphous irondistribution transformers in the EU has beenvery limited. Tis is partly due to network designcharacteristics which differ from US and Japanesepractice. However a very large (1,600kVA)

amorphous iron three-phase distributiontransformer has recently been built and installedin the EU.

REQUIREMENTS OF THE TECHNOLOGYINTERVENTION

3.1.2. Future Developments

Research and development on magnetic steels

is vigorously pursued world-wide. Te licensingof new processes has been extremely prevalentin this sector for many years. Distributiontransformers appear to represent a poor returnon recent development effort, with the possibleexception of amorphous iron, because of thecompetitive nature of the market. However newmagnetic steel developments also benefit fromother applications, notably electric motors andsmall transformers.

Future emphasis on energy efficiency andenvironmental impact could change this picture.Among areas of interest are: the ending of certain patents on amorphous

iron processes, which could encourage otherproducers to enter the market

the adoption of the design of amorphous irontransformers to European practice (i.e. usea three legged Evans-core design for Dy-connected transformers, resulting in reducedlength, cost and noise)

mechanical or thermal processes other thanlaser etching for domain limitation

the use of thinner steels. Magnetic steels withgauges as low as 0.05mm are being offered

in narrow strip for small transformers andcoils. For larger transformers 0.18mm steelis available, but both raw material and corefabrication costs rise very rapidly as the gaugeis reduced.

3.1.3 Superconducting Transformers

A number of superconducting distributiontransformers have been built. One company

has developed a nitrogen-cooled 630kVA hightemperature superconductor (HS) transformer,which was installed in the Swiss electricity

21



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supply network in 1997. Tis is a single-phasetransformer, and considerable engineeringproblems are reported in producing three-phaseversions.

It is widely agreed that superconductivity will

always remain much more expensive for powerdistribution transformers than conventionaltechnology. Te most promising areas appearto be in specialist applications, particularlytraction transformers, where increasingly largetransformers are required for train motors inrailway networks.

3.1.4 Technology Sources

Power systems transformers are very specializedproducts, and R&D activities outside the majortransformer manufacturing companies arelimited. Even here most effort is centered onpractical product development, together with thetesting and evaluation of new materials. Onlya few distribution transformer manufacturersin Europe have significant fundamental R&D

capabilities dedicated to transformer research.

Much of the recent work on the steels usedin distribution transformers has originatedfrom Japan and the United States, althoughEuropean companies have a world reputationfor the steels and non-ferrous alloys used insmaller transformers. Some of the technology foradding value to conductors and coils, such as the

continuous cold rolling of narrow strip, has alsobeen imported. However there are a number ofcenters of excellence in Europe, with a capabilityfor R&D and demonstration of distributiontransformers or component materials. ManyEuropean universities have a capability inmagnetic materials within their electricalengineering or materials departments.

3.2 Contribution to EnergyEfficiency and Global WarmingGoals

Emissions data suggested by the InternationalInstitute for Energy Conservation (IIEC) forEurope is 0.4kg CO2/kWh. Electrical energysavings of 22.3Wh will provide emissionssavings of 8.9 million tons of CO2. Te

European Union is committed to a reduction of8 per cent on 1990 levels (266 million tons) by2008-2012.

Te potential savings from energy-efficientdistrubution transformers could reach 7.3 Wh.Tis is approximately over 1% of the Europeancommitment.

o put the overall potential saving of 22.3Whinto perspective, this is equivalent to the annualenergy use of over 5.1 million homes or theelectricity produced by three of the largest coalburning power stations in Europe.

Distribution transformers have not yet been thefocus of energy saving measures and could, if

developed, contribute significantly to Europeantargets for reduction.

3.3 Characterization of the UtilityMarket

Utility markets account for approximatelyhalf the installed transformer capacity inEurope. Troughout Europe, the purchasing oftransformers seems to be reasonably standardized,

with the utilities having open tender practicesin line with European Purchasing Directives.In almost all cases, losses (iron and copper) arefactored into the specification, with minimumstandards in line with internationally acceptedstandards. However, the specifications ineach country differ in relation to the loadcharacteristics (rural/urban), the network being

served or the requirements for low noise emission(e.g. in German urban areas).

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Selection of the supplier is usually made on thefirst cost principle, i.e. the supplier providingthe lowest cost offer that meets the specificationwins the business. Few exceptions are made wherea supplier offers a more efficient transformer

(i.e. lower life-time cost), but at a slightly higherprice. Te one exception to this is the Nordiccountries, where the efficiency of the transformerin specific applications is given a high priority,with the specification giving the efficiency of thetransformer a very high rating.

In almost all EU countries, first cost is the drivingprinciple. Where the utility is state owned,

limitations on capital expenditure are paramountto assist in meeting the ever tighteningbudgets brought about by the strict monetaryrequirements associated with the . Where theutility is in private ownership, the availability ofcapital for efficient transformer purchases alwayscompetes against more attractive (i.e. quickerpayback) investments that can be made by the

utility in other areas. In both cases, the lack ofinterest in efficient transformers is compoundedby the electricity suppliers inability to pass thecost of any losses on to the consumer, henceremoving any incentive to overall system, andconsequentially transformer, performance.

3.4 National/International Policiesand Initiatives

Across Europe, transformers are manufactured toindividual national standards. Tese are broadlycompatible with the European specification,Harmonization Document 428. Tis in turnis based on the International Electro-technicalCommission World Standard IEC60076.Trough this harmonization of standards, amechanism is in place for communicating and

enforcing more rigorous requirements for energyefficiency. However at present, compliance withHD428 is purely voluntary. For this mechanismto be effective in increasing the overall level

of transformer efficiency across Europe, thespecification would have to be formally adoptedby CENELEC as a standard and compliance (viathe provisions of any national standard) wouldhave to be compulsory.

Despite this apparent standardization, nationalstandards can vary significantly. Each countryhas its own specific issues related to distributionsystem strength, capacity considerations, etc.Other differences result from variations inparticular circumstances within countries. InFrance, the majority of generation is by nuclearpower station. Te marginal cost of generation is

therefore very low and the environmental impactis negligible because emissions are minimal.French utilities are therefore under no pressure topurchase energy-efficient transformers and lowestfirst cost transformers are specified as standard.In Germany, where many transformers are basedin the centre of residential areas, there are verystringent noise regulations. Tere are also often

size restrictions.

Harmonizing the East/West supply systems andstandardizing the equipment are also causingproblems.

Te situation is further confused with theregulators in each country setting varying goalsfor the utility companies. In almost all cases,

continuity of supply is the key factor. However,variations on other priorities are profuse andcover cost of electricity to the customer, voltagetolerances, safety, noise, overall environmentalimpact of the system, etc.

Tere appears to be little overall attemptto encourage the uptake of energy-efficienttransformers by any national government or

regulator. In the UK, the regulator includes anefficiency incentive in the pricing formula forsupply, but this is marginal compared with other

23



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considerations. Te following example describeshow one electricity supply company assessed thevalue of fitting amorphous core transformers intoits network.

3.5 National/International Policiesand Initiatives

Across Europe, transformers are manufactured toindividual national standards. Tese are broadlycompatible with the European specification,Harmonization Document 428. Tis in turnis based on the International Electro-technicalCommission World Standard IEC60076.

Trough this harmonization of standards, amechanism is in place for communicating andenforcing more rigorous requirements for energyefficiency. However at present, compliance withHD428 is purely voluntary. For this mechanismto be effective in increasing the overall levelof transformer efficiency across Europe, thespecification would have to be formally adoptedby CENELEC as a standard and compliance (via

the provisions of any national standard) wouldhave to be compulsory.

Despite this apparent standardization, nationalstandards can vary significantly. Each countryhas its own specific issues related to distributionsystem strength, capacity considerations, etc.Other differences result from variations inparticular circumstances within countries. In

France, the majority of generation is by nuclearpower station. Te marginal cost of generation istherefore very low and the environmental impactis negligible because emissions are minimal.French utilities are therefore under no pressure topurchase energy-efficient transformers and lowestfirst cost transformers are specified as standard.In Germany, where many transformers are basedin the centre of residential areas, there are very

stringent noise regulations. Tere are also oftensize restrictions.

Harmonizing the East/West supply systems andstandardizing the equipment are also causingproblems.

Te situation is further confused with the

regulators in each country setting varying goalsfor the utility companies. In almost all cases,continuity of supply is the key factor. However,variations on other priorities are profuse andcover cost of electricity to the customer, voltagetolerances, safety, noise, overall environmentalimpact of the system, etc.

Tere appears to be little overall attempt

to encourage the uptake of energy-efficienttransformers by any national government orregulator. In the UK, the regulator includes anefficiency incentive in the pricing formula forsupply, but this is marginal compared with otherconsiderations.

3.6 Potential Mechanisms for Change

Tere appears to be several potential mechanismsthat could change the buying behavior oftransformer purchasers. Each potentialmechanism is briefly examined below.

3.6.1 No Change Scenario

It is possible that no action at the EU level will berequired, as national governments begin to realizethe implications of international commitments

on CO2 and act at national level to improve theefficiency of transformers purchased. However,realistically this is unlikely to occur, due to thelong term nature of savings from transformersand the complex nature of specification and thepurchasing cycle. National governments are muchmore likely to concentrate on simpler targets, e.g.improvements in the performance of domesticappliances, etc.

24



Section3

3.6.2 Enforceable Minimum Standards

Discussions have already taken place betweenEC DGXVII, COREL and EURELECRICto discuss the possibility of voluntary agreementsor a European Directive to initiate reduced

losses from distribution transformers through aminimum standard.

A minimum standard of sorts already exists inthe Harmonization Document 428 (standardfor three-phase oil immersed distributiontransformers, 50 Hz, from 50kVA to 2500 kVAwith highest voltage for equipment not exceeding36kVA). Tis standard could be made more

prescriptive and specify improved minimumlosses for all types of transformer.

Such a standard could then be made mandatorythrough an EU Directive.

Unfortunately, such an approach is likely to bestrongly resisted at national level, due to the

specific needs of each national distribution systemand local political considerations. Further, theimposition of overall standards for efficiencyhigher than those already in force would causeproblem s, due to the variations in demandprofiles from the various end use applications, e.g.rural/urban uses.

An alternative approach would be for the EU

to place obligatory requirements on nationalregulators to include efficiency as one of theirkey elements when forming regulatory policy. Itis unlikely that such an approach would work as,without specific guidelines, regulators are likelyto simply pay lip-service to the issue. Further, thepreparation of specific guidelines may imposeon the principles of subsidiarity and would bedifficult to draft in any case.

3.6.3 Financial Incentives

Te major cause of purchases of less efficient

transformers is the requirement of manypurchasers for the lowest first cost. If somefinancial mechanism could be introduced,that would make the purchase of efficienttransformers more attractive, it is likely to have a

major impact on the marketplace. Such financialincentives appear to fall into three categories:If a mechanism was in place to define efficienttransformers (e.g. transformer labels describedbelow), it would be possible to offer rebateson purchases of higher efficiency units, hencelowering the purchase cost differential betweenthe more and less efficient units.

Unfortunately, the rebate would be extremely

expensive, given the number of transformerspurchased across the EU annually. Further, such ascheme could only be sustained for a short periodand following withdrawal, the marketplace wouldalmost certainly revert to the original situationwith no lasting market transformation.

Changing national taxation systems to make

the capitalization of transformers moreattractive, e.g. shortening the allowable assetswrite- off period, is likely to have a majorimpact on the purchases made by utility buyers(other buyers are unlikely to purchase enoughtransformers for this to have any significantimpact relative to other considerations). However,this would have to be made a national issue,as the EU is specifically excluded from direct

interference with national taxation issues. Assuch, it is unlikely that individual member stateswould adopt such a policy, due to the complexrequirements in drafting the required legislationand policing claims under the system. Increasingresponsibility for cost of losses. Obviously,financial costs associated with losses fromtransformers owned by end users are alreadyborne by the end user. However, losses accruing

from transformers owned by utilities are currentlyalmost universally transferred to the end user aspart of the cost of electricity.

25



Section3

Tis situation is difficult to change where theutility is state owned. However, where the utilityis privatized, there is an opportunity to use thiscost of losses as an incentive to improve thesystem. At present, if the utility improves the

efficiency of the system, then the amount of costof losses is adjusted accordingly, hence the utilitymakes little improvement in profit.

A realignment of the pricing structure , to allowa fixed amount of cost for losses to be passedto the consumer, with the savings from anyreduction in losses split between the consumerand the utility (say on a 50:50 basis), would

improve the business case for examining lifetimecosting. Such a system would allow investmentsin efficient transformers to be more competitiveagainst other demands on the capital budgetsof the utilities. However, this is again a nationalissue, with the individual pricing regimes comingunder the control of the national regulators.

3.6.4 Liberalization

Te costs and profits of network companiesin a liberalized electricity market are in mostcountries limited by regulation or regulatedtariffs. Tis may inhibit investments in energyefficiency measures, for instance high efficiencytransformers. Te risk is that companies are morefocused on short term cost savings and fail toinvest in systems that would save more in the

long run.

If the correct regulatory framework is developed,investments in improving the efficiency of anetwork can also be stimulated under marketregulation. Te following is a short description ofthe 4 main barriers and possible remedies.

1. Most models of regulation rely on a partial

redistribution of savings to consumers.Tis discourages companies from makinginvestments for efficiency improvements, since

cost reduction from the investment are sharedwith the consumers. Allow some carryover of measurable

efficiency gains, so that investing in energyefficiency becomes more attractive for the

network companies.

2. Capital-intensive investments are very sensitiveto future changes, e.g. in the regulatory regime.Tis discourages investments in efficiencyimprovements. Give special incentives to promote capital-

intensive energy efficiency measures. Createa stable, long term system of regulation.

3. Te regulatory framework tends to concentrateon cost savings in the short term.

Tese do not encourage companies to take thelife cycle costs of equipment intoaccount.

4. Energy losses are calculated withoutconsideration of external costs. ake the true cost of network losses into

account.

3.6.5 Labelling system

Lack of knowledge is a significant barrier to thepurchase of energy- efficient transformers. Tis isparticularly true of large energy users, where there

is a desire to use efficient transformers, but notthe technical ability to specify them effectively.

A labeling system that indicated the efficiency oftransformers under specific load profiles wouldassist this group considerably, and is likely tocause a significant movement in the market.While there are obvious difficulties in creatinga labeling system for transformers, given the

variability of losses depending upon application,it is possible to develop a labeling system thatprovides the user with appropriate guidance in

26



Section3

most instances. Such a system is currently underdevelopment for electric motors, a product withsimilar difficulties in efficiency definition.

Te introduction of a labeling system also

provides a framework from which futureminimum standards may be derived (if deemedappropriate). Te framework could also be usedfor financial incentives, should they be required ata national level.

3.6.5 Labelling system

Lack of knowledge is a significant barrier to thepurchase of energy- efficient transformers. Tis isparticularly true of large energy users, where thereis a desire to use efficient transformers, but notthe technical ability to specify them effectively.

A labeling system that indicated the efficiency oftransformers under specific load profiles wouldassist this group considerably, and is likely tocause a significant movement in the market.

While there are obvious difficulties in creatinga labeling system for transformers, given thevariability of losses depending upon application,it is possible to develop a labeling system thatprovides the user with appropriate guidance inmost instances. Such a system is currently underdevelopment for electric motors, a product withsimilar difficulties in efficiency definition.

Te introduction of a labeling system alsoprovides a framework from which futureminimum standards may be derived (if deemedappropriate). Te framework could also be usedfor financial incentives, should they be required ata national level.

3.6.6 Voluntary schemes

Voluntary schemes do not have the disadvantages

of a mandatory minimum standard.

Te targets can often be set at a more ambitious

level and reviewing them is less diffcultand less time consuming. Consequently, it is amuch more exible system.

Te main difficulty to overcome in voluntary

programs is reaching a reasonable degree ofparticipation often taking a few years.

Te goal of a voluntary program should be tomake the incentives and the image so importantthat it becomes difficult for companies to ignore.High image value, a meaningful brand presence,and a strong policy context for instance make theJapanese oprunner program a good example of

an effective scheme.

3.7 International Perspective

3.7.1 US and Canada

Te US DOE is in the process of implementinga test standard for distribution transformers,following a report from Oak Ridge thatsupports a DOE determination that minimum

performance requirements for distributiontransformers can be justified.

Following on from the test standard, formal analysisand legislation will be implemented. Te standardis not expected to be issued until after 2000.

Te transformer industry opposes the prospect

of a mandatory minimum and would prefer avoluntary standard (NEMA P1).

Te Oak Ridge study concluded that the P1levels of energy efficiency do not meet the DOEcriteria. A US Energy Star program whichprovides energy efficiency labeling, currentlypromotes the P1 levels of energy efficiency.Canada is in the midst of consultation to

implement mandatory levels equivalent toP1, with a view to revising them once the USlegislation has been implemented.

27



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3.7.2 China

Shanghai Zhixin Electrical Industry Co Ltd.have been developing a relationship with GEunder a license agreement to produce amorphouscore transformers since June 1997. Te contract

was signed in February 1998. Currently theyare importing most of the components andassembling them in Shanghai. A core windingmachine has been purchased, to be installed inmid-July 1999.

Average transformer size is 400kVA. ShanghaiUrban Power Distribution Bureau have installed116 sets of amorphous core transformers, saved

770,000kWh power per year, worth about27,900,000 RMB (3.2 million).

Information from the company identifies theno load losses as 20% of those in a conventionaltransformer. Te incremental cost is 30% overthat of a conventional transformer. Tey havea target to reduce this to 20% when more

components are manufactured in China.Currently the estimated payback is 2.5 years.

ransformer sales in China are estimated to be350,000 per year.

Te company has a production target of 2,000/year, which will rise to 3,000/year, and can seeno technical barriers to more transformers being

manufactured in China if the market can bestimulated. Te main barrier to uptake is theincreased cost over the conventional product.

3.7.3 Australia and New Zealand

Te Australian program for energy efficiency indistribution transformers, executed by the NationalAppliance and Equipment Energy EfficiencyCommittee (NAEEEC), works on two levels.

First, there is the Minimum Energy PerformanceStandard (MEPS), a regulation that bans

transformers which do not meet minimumefficiency levels. Te standards are defined foroil-filled distribution transformers between 10and 2 500 KVA and for dry-type distributiontransformers between 15 and 2 500 KVA, both

at 50% load. Te MEPS are mandated bylegislation, effective 1 October 2004. Under thestimulus of the National Greenhouse Strategyand thanks to the strong will of the partiesinvolved, the creation of the MEPS passedsmoothly. Te field study to define the scope wasstarted in 2000, with the minimum standardswritten in 2002.

Te second track, currently under development,is the creation of further energy efficiencyperformance standards resulting in a scheme forvoluntary high efficiency labeling.

New Zealand follows the Australian regulationfor distribution transformers.

3.7.4 Europe

CENELEC has defined efficiency standards fordistribution transformers in the range from 50to 2500 KVA. HD428 stipulates A, B and Ccategories for load and no-load losses. HD538advises a maximum for the load and no-loadlosses of dry type transformers. Te efficiencyranges defined by these standards are relativelywide. Te minimum efficiency in the highest

category (CC) is still far below the efficiencyof the best in class and far below the 5-startransformer defined by the Indian Bureau ofEnergy Efficiency. CENELEC is currentlydefining new efficiency categories with lowerlosses.

In 1999, a Termie project of the EuropeanUnion assessed the total energy losses in

distribution transformers. Te savings potentialin the 15 countries of the EU was estimated to be22 Wh.

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A mandatory minimum efficiency standardfor distribution transformers is not expectedto be introduced in the near future. Tis isdisappointing, given the availability of world-class transformer technology in Europe.

3.7.5 India

In India, the Bureau of Energy Efficiency (BEE)has developed a 5-star classification scheme fordistribution transformers in the range from25 to 200 KVA. Te scheme is a co-operativeventure between public and private organizationsthat issues rules and recommendations underthe statutory powers vested with it. Te 5-starprogram stipulates a lower and a higher limit forthe total losses in transformers, at 50% load. Tescheme recommends replacing transformers withhigher star rated units. Te 5-star unit representsworld class technology, while 3-stars is recom-mended as a minimum, and already followed bymany utilities. India historically has a rather poorperformance in transformer energy efficiency, but

this 5-star program could become an importantdriver for change.

3.7.6 Japan

In Japan, transformers are a part of theoprunner Program which either defines theefficiency for various categories of a producttype, or uses a formula to calculate minimumefficiency. Tis program, which covers 18different categories of appliances, has somemajor differences compared to other minimumefficiency performance programs.

Te minimum standard is not based on theaverage efficiency level of products currentlyavailable, but on the highest efficiency levelachievable. However, the program does notimpose this level immediately, but sets a target

date by which this efficiency level must bereached. A manufacturers product range must,on average, meet the requirement. It is notapplied to individual products.

3.7.7 Mexico

As in Australia, the Mexican standard includesvoluntary and mandatory elements. Te Normas

Oficiales Mexicanas (NOM) define minimumefficiency performance standards for transformersin the range from 5 to 500 KVA, and acompulsory test procedure for determining thisperformance. For each power category, maximumload and no-load losses are imposed.

29



SECION4

30



Section4

4.1 Use of High-efficiencyTransformers

4.1.1 Achievable Loss Levels

Te HD428 C-C loss level for oil-filleddistribution transformers may, as mentionedbefore, be regarded as providing a high practicalstandard of energy efficiency for a distributiontransformer.

Tere is no internationally agreed definition of

an energy-efficient transformer. It is proposedto use the term energy-efficient transformer forthe following transformers:

l oil-filled transformers: range C-C (HD428.1)and D-E (HD428.3)

l dry-type transformers up to and including

24kV: 20% lower than specified in HD538.1.HD538 mentions one list of preferred values,but explicitly allows the possibility for nationalstandards to specify a second series with loadand/or no-load losses at least 15% lower. Sometransformer manufacturers offer dry-typetransformers in normal and low-loss versionsl dry-type transformers 36kV: 20% better thanspecified in HD538.2, analogous to the previous

category.

An important reason for choosing the valuessuggested above is the fact that these levels areentirely feasible within the current state of theart of nearly all transformer manufacturers. Inthe remainder of this report, the class of energy-efficient transformers is often referred to as C-C,as the oil-filled transformers form the majority of

the transformers, and, among these, units up to24kV are the most numerous.

ANALYSIS, RECOMMENDATIONS, ANDACTION PLANS

An alternative way of defining energy-efficienttransformers would be to by considering the

energy-efficiency levels of the transformerssold on the market. Tis is be analogous to theconcept of the US energy star transformerprogram.

Here transformers with energy efficiency equalto or above that of the most efficient 35% beingcurrently sold meet the requirement for EnergyStar rating.

Another way to define energy-efficienttransformers would be the application of specialwindings, advanced steels or amorphous iron. Anargument against this definition is that there area number of practical considerations involved indeciding on the optimum choice of transformerfor installation into a network.

Moreover, the energy loss level is the keyperformance indicator of each transformer designwith respect to energy efficiency and wouldconsequently the fairest benchmark.

As expected, the loss level of energy-efficienttransformers as defined above does not representthe maximum efficiency which is technically

possible. Both load and no-load losses may bereduced significantly.

Load losses may be reduced beyond the levelsmentioned above by following technical designmeasures:

increasing the conductor section of thetransformer windings, which reduces

conductor resistance and thus load losses. oa lesser extent, the application of ribbon orsheet conductors also contributes to reducingload losses. Te disadvantage of increasing the

31



Section4

conductor section is the higher investmentcost. Another disadvantage is the larger sizeof the transformer, which may exceed themaximum sizes specified by the purchaser.Tis is partially offset by the reduction of heat

production in the transformer, which lowersthe need for cooling.

application of superconductor material forthe windings, eliminating load losses. Tistechnology is not yet mature and still veryexpensive. Te main application will lie inlarger transformers.

Another drawback of superconducting

transformers is the inability to withstand short-circuit currents of the level that are commonin medium-voltage networks. Tese problemsneed to be solved before the superconductingtransformer will become a viable option.No-load losses may be reduced beyond the levelsmentioned above by following technical designmeasures:

increasing the core section, which reduces themagnetic field in the transformer core and thusthe no-load losses. However, this results inhigher investment cost. Another disadvantageis the larger size of the transformer, which mayexceed the maximum sizes specified by thepurchaser.

application of high-grade modern transformercore steel. It should be noted that the C-C

level can be reached without applying laser-etched transformer steel, the latter beingregularly used in large transformers.

reduction of the thickness of the corelaminations.

application of amorphous core material. Tesaving potential with respect to no-load lossesis high, as shown in the table below, where theamorphous transformer is compared to the

conventional types according to HD428.

Energy-efficient transformers are generallyregarded by European customers as technically

sound but uneconomic. Te number ofextremely energy-efficient transformers (beyondthe C-C level) operating in Europe is quite low,compared with the United States. We estimatethat about 200 amorphous distribution iron

transformers have so far been installed, manyof which are very small, and probably a slightlylarger number using laser-etched domain-refinedsteel. Te amorphous iron installations we haveidentified are as follows: yearly peak load: the highest load of the

transformer as a percentage of its rated power.Tis load is only present for a small part of theyear.

running time: the ratio of energy transmittedduring a year [kWh] and the yearly peak load[kW] - physically, this figure indicates howmuch time it would take to transmit the yearlyenergy at a power equal to the yearly peakload. A low value indicates strong fluctuationsof the load, a high value a relatively constantload. Te average transformer load is the yearlypeak load, multiplied by the running time over8760 hours.

loss time: the ratio of the yearly energy loss[kWh] and the maximum losses occurring ina year [kW] - this figure indicates how muchtime it would take for the transformer to losethe yearly energy loss when loaded at themaximum load occurring in the year.

Te data above result into the following data foran A-A and a CC transformer with an averageload profile as indicated above:

Te no-load (iron) losses account for 95% of theyearly losses in the case of a 100kVA transformer,and 66% of the no-load losses in a 1,600kVAtransformer.

For very lightly loaded transformers, theefficiency falls rapidly. Tere are several reasonswhy some transformers are so lightly loaded.Often a limited number of transformer types

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used by a utility (advantages of lower stock) isthe cause, or allowing for a load increase. Usually,the distribution network is dimensioned withcertain expectations of load growth, in order topostpone upgrading of the infrastructure as long

as possible. A final factor is the usual technicalpractice to apply safety margins to electricalequipment. Tis is good for the load losses, butincreases the no-load losses.

Te extremely low loads encountered at sometransformers seem to suggest the need for smallerdistribution transformer sizes, or cores withextremely low losses.

Although the figures used are based on empiricalrules validated by measurements, there is a widespread in the average transformer loading and therunning time. Although some utilities keep trackof the maximum loads of transformers, there areno representative transformer load data availablefor the European Union.

4.1.2 Deviations from the standard lossvalues

Apart from the efficiency class and the loadprofile, many other factors may influence trans-former losses:

medium-voltage (MV) network voltage -the core (iron) losses are dependent on the

network voltage. A higher network voltageleads to higher core (iron) losses. For instance,5% increase of the network voltage may cause10-20% higher core losses, depending on thetype of core material and the design of thetransformer.

Te loss levels of individual transformers are,therefore, always specified for a defined network

voltage. For an individual transformer the effectcan easily be measured. In an electrical network,the voltage at each substation varies according to

the electrical distance to the feeding point and theload situation. A special case is the gradual change(between 1989 and 2004) of the network voltagewithin Europe from 220V or 240V to 230V asdefined in IEC60038. In some cases, the increase

from 220V to 230V is realized by increasing thevoltage level in the medium-voltage network,which leads to increased losses in the distributiontransformers.

On the other hand, the decrease from 240V to230V may be achieved by decreasing the voltagelevel in the medium-voltage network, which leadsto lower losses in the distribution transformers

Operating temperature of the transformer.Conductor losses slightly increase with theoperating temperature of the transformer.

Te loss levels of individual transformersare, therefore, always specified for a definedoperating temperature

Production deviations of the transformer.Tis is a quality assurance aspect, which willnormally not yield large deviations from thecontracted loss values

Ageing of the transformer. Older transformersmay deteriorate in several modes, one ofwhich is a loss increase. Normally, this effect isneglected. Tere are, however, some concernsabout ageing of amorphous cores

- Poor power quality. Te presence of non-linear

loads in the network will lead to harmoniccurrent components in the transformer.Tese harmonic currents tend to heat thetransformer, but normally the transformer designallows for some harmonic contents of the loadcurrent. Normally, this effect is not taken intoaccount, except in industrial or comparableinstallations with many distorting loads.

Accounting for these factors for a networkwould require a detailed knowledge of operatingconditions, Usually, efficiency class and

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transformer loading are the two dominant factors,the other factors are not taken into account whenassessing transformer losses.

4.1.3 Loss Evaluation

A transformer purchaser aims to buy the cheapesttransformer, i.e. with the lowest total cost ofOwnership, which complies with the require-ments for a given application. Te total cost ofownership of a transformer consists of severalcomponents, including purchase price, the valueof energy losses, maintenance and repair costsover the lifetime, and decommissioning cost.

Te purchase price and the energy losses are thetwo key factors for comparison of the differenttransformers. Installation, maintenance, repairand decommission costs are seldom taken intoaccount for choosing between transformers asthey are relatively insensitive to transformerdesign.

In cases where transformers of differenttechnologies are compared, e.g. dry-type and oil-immersed, installation costs (e.g. fire protection,oil containment provisions) will be considerablydifferent and do need to be taken into account.When comparing two transformers with differentpurchase prices and/or different losses, one musttake into account that the purchase price is paidat the moment of purchase, while the cost of

losses come into effect during the lifetime of thetransformer.

Usually the costs are converted to the momentof purchase by assigning capital values. Whentransformers are compared with respect to energylosses, the process is called loss evaluation.In the basic process of loss evaluation, threetransformer figures are needed: purchase price load loss no-load loss

For the specified load loss of a transformer, thepurchaser can assign a cost figure per kW of lossrepresenting the capitalized value (net presentvalue) of the load losses over the lifetime of thetransformer or a shorter time scale e.g. 5 or 10

years. Tis cost figure is based on the expectedtransformer load over time, the average costper kWh and the interest rate chosen by thepurchaser.

Similarly, for the no-load loss of a transformer,the purchaser can assign a cost figure per kW ofno-load loss representing the capitalized value ofthe no-load losses. Tis cost figure is also based

on the average cost per kWh and the interest ratechosen by the purchaser.

As nearly all transformers are connected to thegrid for 100% of the time, and the no-load lossesare independent on the load, the load curve is notrelevant. Te average cost per kWh will tend tobe lower than for the load losses, as the latter willtend to coincide with peak loads, at which timeenergy is very expensive.

Since different transformer users have differentoperating costs and cost of capital assumptions,the otal Cost of Ownership (CO), mentionedsection 2.4.2, is distinct for every user. Tus,CO of a transformer can be further simplifiedand expressed as the sum of the purchase price

(Ct), the cost of no-load losses and the cost of theload losses, or as a formula:CO = Ct + A x Po + B x Pk

where A represents the assigned cost of no-loadlosses per watt, Po the value of the no-load lossesper watt, B the assigned cost of load losses perwatt and Pk the value of the load losses per watt.Tis formula can also be found in the HD