Energy Conservation by Low Loss Energy Conservation by Low Loss

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T. Kefalas 1 , A. Kladas 1 , Μ. Τsili 2 , Ε. Amoiralis 3 , P. Georgilakis 1 , «Energy Conservation by Low Loss Energy Conservation by Low Loss Energy Conservation by Low Loss Energy Conservation by Low Loss Distribution Transformers Adapted to Distribution Transformers Adapted to Distribution Transformers Adapted to Distribution Transformers Adapted to Load Characteristics Load Characteristics Load Characteristics Load Characteristics» G. Loizos 4 , and A. Souflaris 4 1 School of Electrical and Computer Engineering, National Technical University of Athens 2 Hellenic Transmission System Operator S.A. 3 Department of Production Engineering and Management, Technical University of Crete 4 Schneider Electric AE, GR-32011, Inofyta, Viotia, Greece

Transcript of Energy Conservation by Low Loss Energy Conservation by Low Loss

Page 1: Energy Conservation by Low Loss Energy Conservation by Low Loss

T. Kefalas1, A. Kladas1, Μ. Τsili2, Ε. Amoiralis3, P. Georgilakis1,

««««Energy Conservation by Low Loss Energy Conservation by Low Loss Energy Conservation by Low Loss Energy Conservation by Low Loss Distribution Transformers Adapted to Distribution Transformers Adapted to Distribution Transformers Adapted to Distribution Transformers Adapted to

Load CharacteristicsLoad CharacteristicsLoad CharacteristicsLoad Characteristics»»»»

T. Kefalas , A. Kladas , Μ. Τsili , Ε. Amoiralis , P. Georgilakis ,

G. Loizos4, and A. Souflaris4

1School of Electrical and Computer Engineering, National Technical University of Athens

2Hellenic Transmission System Operator S.A.

3Department of Production Engineering and Management, Technical University of Crete

4Schneider Electric AE, GR-32011, Inofyta, Viotia, Greece

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Impact of distribution transformer no-load losses• The importance of distribution transformer no-load loss on the operation of modern

electricity grids is often underestimated.

• Internationally, distribution transformer no-load loss constitutes nearly 25% of the transmission and distribution losses of electricity grids.

• Greenhouse gas emissions due to the combustion of fossil fuels to offset no-load losses of the transformers installed in the distribution grid.losses of the transformers installed in the distribution grid.

• Increase in operating cost of the transformer.

Purpose of the paper• To illustrate the significance of distribution transformer no-load loss in periods

of high electric energy cost.

• The presentation of a novel numerical methodology for wound core transformers no-load loss analysis, enabling to determine the economically and technically optimum transformer.

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Losses in the electrical gridLosses in the electrical grid

International and European statistical data• Losses in the electricity network worldwide are estimated to about 1,279 TWh i.e.,

9.2% of total electricity generated or a global economic loss of 61 billion USD.

• In the European Union (EU-27), according to Strategies for development and diffusion of Energy Efficient Distribution Transformers (SEEDT), losses of distribution transformers are calculated at 33 TWh / year.distribution transformers are calculated at 33 TWh / year.

Greek statistical data• The number of installed distribution transformers in Greece is estimated to about

155,000 units. PPC owns about 140,000 units.

• Electricity power requirements of 56 MW or to energy requirements of about 490 GWh / year due to no-load losses.

• PPC installs approximately 7,300 new distribution transformers each year.

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Transformer noTransformer no--load loss evaluationload loss evaluation

Transformer no-load loss computation is achieved by combining the local peak flux

density distribution with the experimentally determined local specific core losses.

The peak flux density calculation of distribution transformers under no-load distribution transformers under no-load operation is achieved by using nonlinear

magnetostatic finite element analysis. The procedure is based on a four-step scheme.

Local specific core losses are determined experimentally by using search coils and an

advanced data acquisition experimental setup.

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Finite element package for distribution

transformer no-load loss evaluation

No-load loss computational capabilities:

1. Wound cores

2. 1-phase transformers

3. 3-phase transformers

4. B-H representation

5. B-SCL representation

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Wound core finite element distribution

Geometry Magnetic field intensity

Flux density Magnetic vector potential

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Experimental setupExperimental setup

The experimental The experimental setup consists of:setup consists of:

PCPCNI 6143 PCI NI 6143 PCI DAQ cardDAQ card

Active voltage Active voltage Active voltage Active voltage differential probedifferential probe

Current probeCurrent probeVariable Variable

transformertransformer

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Longitudinal flux density measurements Longitudinal flux density measurements

30 two turn search 30 two turn search coils were wound coils were wound around the total around the total

width of the sheetwidth of the sheet10 along the limb10 along the limb10 along the limb10 along the limb10 along the yoke10 along the yoke

10 along the corner10 along the corner

Used for Used for determining local determining local specific core losses specific core losses

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Using tensor, reluctivity or permeability, representation of the wound core, an accurate estimation of the peak flux density

Computed and experimental 1-phase wound core distribution transformer

no-load loss agree within 1% to 4%

Comparison of computed and experimental resultsComparison of computed and experimental results

peak flux density distribution is achieved.

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Comparison of computed and experimental local

flux density distribution. At core corner and leg

for B = 1.55 T. for B = 1.55 T.

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Comparison of computed and experimental local

flux density distribution. At core corner and leg

for B = 1.86 T. for B = 1.86 T.

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Comparison of computed and measured no-load loss of 3-phase wound core shell type

distribution transformers

Computed and experimental results agree within 1% and 6%.

Computed no-load losses are underestimated but in some cases there are overestimated.

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Design optimization procedureDesign optimization procedureThe optimization of the wound core transformer design is carried out by combining the no-

load loss evaluation methodology with the branch and bound optimization procedure.

The proposed optimization method was compared with the conventional heuristic methodology used in the transformer manufacturing industry.

Algorithm of the optimization procedure.

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Comparison of conventional and proposed optimization methods for distribution transformers of nominal capacity 160 kVA, ΒΑ’ loss class, 160 kVA, ΑC’ loss class, 400 kVA,

ΒΑ’ loss class, and 400 kVA, ΑC’ loss class.

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Comparison of conventional and proposed optimization methods for distribution transformers of nominal capacity 1000 kVA, ΒΑ’ loss class, 1000 kVA, ΑC’ loss class, 1600

kVA, ΒΑ’ loss class, and 1600 kVA, ΑC’ loss class.

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Cost percentage difference between optimum design of the conventional and proposed methodology per transformer nominal capacity.

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High efficiency distribution transformers constitute a technology that is capable of reducing network losses due to the following reasons:

•Distribution transformers represent the second major component of losses in the grid.

•Replacement of transformers is easier than changing high and medium voltage lines.

•There are significant margins for reducing transformer losses, as there are nowadays technologies capable of reducing losses up to 80% during the lifetime of a transformer.

ConclusionConclusion

On this basis, it becomes clear that there are several reasons for using high efficiency distribution transformers as a technology for improving the efficiency of the electricity grid.

An accurate prediction of no-load losses during the design phase is very important for transformer manufacturers since it contributes to the following:

•The reduction of safety margins for no-load losses.

•Avoid payment of no-load loss penalties.

•The reduction of delivery time of newly manufactured transformers.