Energy Saving Opportunities for Transformers

Hans De Keulenaer

Outokumpu Tara Mines

Energy Efficient Motors & Transformers Workshop

May 7, 2002

15-May-02 2

Content

• Introduction

• Technical issues & standards

• Economic equations

• Ecological equations

• The business case for high efficiency transformers

• Conclusion

15-May-02 3

Why transformer efficiency is an issue?

• All electricity passes through several stages of transformation

• Savings potential of 22 TWh / year for EU

• Technology exists

• Economic potential

• Many pieces to the sustainable energy puzzle

15-May-02 4

Losses in distribution transformers

• No load loss, or iron loss (Po)

• Load loss, or copper loss (Pk)– DC loss– Extra losses

• eddy current loss in windings• stray loss

• Other losses (ventilation, …)

15-May-02 5

No load loss

Extra loss

Resisitive loss

Conventional loadloss excl harmonics

Extra loss due toharmonics

Unloaded Rated load Actual load Actual load (excl harmonics) (incl harmonics)

Load loss

Losses in distribution transformers

15-May-02 6

Iron loss

• Occurs 24 hours / day, 365 days / year

• Example: 1,600 KVA, Po = 2,600 W– Annually 2,600 W * 8,760 hrs = 22.8 MWh / yr– 30 yrs = 684 MWh

– Emissions (0.4 kg CO2 / kWh) = 274 tonnes

– 5 c / kWh = 34,200 €

15-May-02 7

Historical evolution in the production of magnetic steel

YEAR(approx.)

CORE MATERIAL THICKNESS(mm)

EPSTEIN VALUE(W/kg at 50Hz)

TYPE

1895 Iron wire 6 (1.0T)1910 Warm rolled FeSi 0.35 2 (1.5T)1950 Cold rolled CGO 0.35 1 (1.5T) M6x1960 Cold rolled CGO 0.3 0.9 (1.5T) M5x1965 Cold rolled CGO 0.27 0.84 (1.5T) M4x1970 Cold rolled HiB 0.3 0.8 (1.5T) M0H1975 Amorphous metal 0.03 0.2 (1.3T)1980 Cold rolled CGO

Cold rolled HiB0.230.23

0.75 (1.5T)0.70 (1.5T)

M3xM0H

1983 Laser treated HiB 0.23 0.6 (1.5T) ZDKH1985 Cold rolled CGO 0.18 0.67 (1.5T) M2x1987 Plasma treated HiB 0.23 0.6 (1.5T) Plasma PJ1991 Chem.Etched HiB 0.23 0.6 (1.5T) PDR

15-May-02 8

Evolution of magnetic steel since the introduction of cold-rolled magnetic steel

15-May-02 9

Copper loss

• Occurs only when transformer is loaded• Varies quadratically with the load• Example: 1,600 kVA, Pk = 17 kW, 50% loaded

– Annually 17 kW * 8,760 hrs * 0.5^2 = 37.2 MWh/yr– 30 yrs = 1.11

GWh

– Emissions (0.4 kg CO2 / kWh) = 444 tonnes

– 5 c / kWh = 55,500 €

15-May-02 10

Loading

• Case 1:– 30% of time 80% load– 70% of time 10% load

• Case 2:– 8 hours @ 80%– 8 hours @ 40%– 8 hours @ 10%

15-May-02 11

Typical load profilekW (15 avg)

-50

0

50

100

150

200

250

300

350

400

450

500

550

600

650

700

750

800

22/1

0/01

19:

45

23/1

0/01

0:1

5

23/1

0/01

4:4

5

23/1

0/01

9:1

5

23/1

0/01

13:

45

23/1

0/01

18:

15

23/1

0/01

22:

45

24/1

0/01

3:1

5

24/1

0/01

7:4

5

24/1

0/01

12:

15

24/1

0/01

16:

45

24/1

0/01

21:

15

25/1

0/01

1:4

5

25/1

0/01

6:1

5

25/1

0/01

10:

45

25/1

0/01

15:

15

25/1

0/01

19:

45

26/1

0/01

0:1

5

26/1

0/01

4:4

5

26/1

0/01

9:1

5

26/1

0/01

13:

45

26/1

0/01

18:

15

26/1

0/01

22:

45

27/1

0/01

3:1

5

27/1

0/01

7:4

5

27/1

0/01

12:

15

27/1

0/01

16:

45

27/1

0/01

21:

15

28/1

0/01

1:4

5

28/1

0/01

5:1

5

28/1

0/01

9:4

5

28/1

0/01

14:

15

28/1

0/01

18:

45

28/1

0/01

23:

15

29/1

0/01

3:4

5

29/1

0/01

8:1

5

29/1

0/01

12:

45

kW to T1

kW to T4

kW tot

15-May-02 12

Results

• Energy transformed:– 1,600 kVA * 0.5 * 8,760 = 7,008 MWh / year

• Efficiency = 7,008 / (7,008 + 22.8 + 37.2) = 99.2%

• Lifetime cost:– Transformer: 10,000 € 10%– Iron loss: 34,200 € 35%– Copper loss: 55,500 € 55%– Total 99,700 € 100%

15-May-02 13

Transformer efficiency

90%

91%

92%

93%

94%

95%

96%

97%

98%

99%

100%

0% 25% 50% 75% 100%

400 kVA,400 kVA,efficiencyefficiencylevel A-A’level A-A’(HD428) (HD428)

15-May-02 14

Efficiency @ low load

75%

80%

85%

90%

95%

100%

0% 5% 10% 15% 20% 25%

400 kVA,400 kVA,efficiencyefficiencylevel A-A’level A-A’(HD428)(HD428)

15-May-02 15

Efficiency standards

• Two approaches– European approach: specify Po and Pk

• CENELEC HD428 (oil) Po class A’, B’, C’Pk class A, B, C(nine combinations)

• CENELEC HD538 (dry) one class for Po, Pk

– US approach: specify efficiency at average load (typically 35-50%)

15-May-02 16

Load Losses for Distribution Transformers No-Load Losses for Distribution Transformers

RATED

POWER

OIL-FILLED (HD428) UP TO 24kV2) DRY TYPE

(HD538)

OIL-FILLED (HD428) UP TO 24kV2) DRY TYPE

(HD538)

LIST A LIST B LIST C 12kV

PRIMARY 3)

LIST A’ LIST B’ LIST C’ 12kV

PRIMARY 3)

kVA W W W W W W W W

50 1,100 1,350 875 N/A 190 145 125 N/A

100 1,750 2,150 1,475 2,000 320 260 210 440

160 2,350 3,100 2,000 2,700 460 375 300 610

250 3,250 4,200 2,750 3,500 650 530 425 820

400 4,600 6,000 3,850 4,900 930 750 610 1,150

630 /4%1) 6,500 8,400 5,400 7,300 1,300 1,030 860 1,500

630 /6% 6,750 8,700 5,600 7,600 1,200 940 800 1,370

1000 10,500 13,000 9,500 10,000 1,700 1,400 1,100 2,000

1600 17,000 20,000 14,000 14,000 2,600 2,200 1,700 2,800

2500 26,500 32,000 22,000 21,000 3,800 3,200 2,500 4,300

Source: CENELEC

Distribution transformer efficiency standards

15-May-02 17

Extreme cases

High loss >> AA’ Low loss >> CC’

15-May-02 18

97.5%

98.5%

99.5%

Rating (kVA)

HD428 BA'

HD428 CC'

NEMA TP1

China S9

HD428 AA'

C-Amorphous

Comparison of efficiency at 50% loadComparison of efficiency at 50% load

15-May-02 19

Conductor materials

• Cu and Al transformers can be built to comply to the same performance and quality standard

• Smaller ratings are typically cheaper with Cu• In general, use of Cu leads to:

– heavier, but more compact windings– a smaller core– a smaller, more compact transformer– a lower noise level– less oil-content

15-May-02 20

400 KVA AA' design

90%

100%

110%

120%

130%

cost total mass noise volume

Cu

-re

f =

100

Cu design

Al design

400 KVA CC' design

90%

100%

110%

120%

130%

cost total mass noise volume

Cu

-re

f =

100

Cu design

Al design

1600 KVA AA' design

90%

100%

110%

120%

130%

cost total mass noise volume

Cu

-re

f =

100

Cu design

Al design

1600 KVA CC' design

90%

100%

110%

120%

130%

cost total mass noise volume

Cu

-re

f =

100

Cu design

Al design

Copper and Aluminium Designsfor the same efficiency

15-May-02 21

Dry-type versus oil-filled transformers

• higher initial cost

• higher no-load losses

• lower load losses

• harmonics cause less extra heating and ageing

• better fire protection

• no oil spilling container

15-May-02 22

79%

9%

12% Resistance

Magnetic

Eddy Current

Total loss = 1685 W

Full load losses in a 100kVA C-C’ transformer

15-May-02 23

Harmonic profile of a typical Personal Computer

15-May-02 24

41%53%

6%

Resistance

Magnetic

Eddy Current

Total loss = 3245 W

Full load losses in a 100kVA C-C’ transformer

15-May-02 25

CP

PttempWorking

f

k 17393.190

102t

TtimeLife

yearsTtimeLife

f

fk

P

PPt

13.02402 3.8

10

where T is working temperature at rated fundamental power, Pf,, Pk is the total power and T is the rated life-time in years

Effect of additional losses on life-time

15-May-02 26

Harmonic cultureTHD and K-factor (30 min. average)

0

10

20

30

40

50

60

22/1

0/01

20:

30

23/1

0/01

2:0

0

23/1

0/01

7:3

0

23/1

0/01

13:

00

23/1

0/01

18:

30

24/1

0/01

0:0

0

24/1

0/01

5:3

0

24/1

0/01

11:0

0

24/1

0/01

16:

30

24/1

0/01

22:

00

25/1

0/01

3:3

0

25/1

0/01

9:0

0

25/1

0/01

14:

30

25/1

0/01

20:

00

26/1

0/01

1:3

0

26/1

0/01

7:0

0

26/1

0/01

12:

30

26/1

0/01

18:

00

26/1

0/01

23:

30

27/1

0/01

5:0

0

27/1

0/01

10:

30

27/1

0/01

16:

00

27/1

0/01

21:

30

28/1

0/01

2:0

0

28/1

0/01

7:3

0

28/1

0/01

13:

00

28/1

0/01

18:

30

29/1

0/01

0:0

0

29/1

0/01

5:3

0

29/1

0/01

11:0

0

29/1

0/01

16:

30

V1 HD THD SD

I1 HD THD SD

I1 HD KF TD

15-May-02 27

Economic evaluation

• 2 approaches to buy a transformer– Specify Po and Pk– Specify A & B factors

Ct = Purchase price + A * Po + B * PkCt = Purchase price + A * Po + B * Pk

8760)1(

1)1(

C kWhn

n

ii

iA

2

8760)1(

1)1(

r

lkWhn

n

I

I

ii

iB C

With I = interest rate 7%n = lifetime 30 yrsCkWh = cost / KWh 0.05 cIl/Ir = loading 50%

15-May-02 28

Example

• 1600 KVA, 50% load, oil-cooled:• (A = 5.4 euro / Watt; B = 1.3 euro / Watt)

– Efficiency AA’ CC’– Purchase 9,700 € 10,300 €– Load loss 22,100 € 18,200 €

(1.3 * 17,000) (1.3 * 14,000)– No load loss 14,040 € 9,180 €

(5.4 * 2,600) (5.4 * 1,700)– Total 45,840 € 37,680 €

15-May-02 29

A and B values for selected countries

Euro / Watt A (NLL) B (LL)Netherlands 4.0 1.2Germany (86) 4.0 1.0Germany (93) 11.3 4.0CH 7.5 1.9China 5.0 0.7Sweden 4.0 0.5

15-May-02 30

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

A-A' A-A' C-C' C-C' A-AMDT C-AMDT

Design

To

tal

ow

nin

g c

os

t

Total owning cost NL Total owning cost D 86 Total owning cost D 93

Total owning cost China Total owning cost CH Total running cost Sweden

Investment costs

Lifetime owning cost400 kVA oil-cooled

15-May-02 31

Beyond the magic of A & B

A factor

0,00

2,00

4,00

6,00

8,00

10,00

12,00

14,00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

jaren

A f

ac

tor

(eu

ro/W

) b

ij e

lek

tric

ite

its

tari

ef

= 1

00

Eu

ro/M

Wh

3% 4% 5% 6% 7% 8% 9% 10% 11% 12%

6,75

Rentepercentage

15-May-02 32

Example - revisited

• 1600 KVA, 50% load, oil-cooled:– Efficiency AA’ CC’– Purchase 9,700 € 10,300 €– Load loss 1,850 € / yr 1,533 € / yr– No load loss 1,140 € / yr 745 € / yr– Result

• Payback 10 months• IRR 119% @ 30 years

15-May-02 33

Ecological evaluation

• 1600 KVA, 50% load, oil-cooled:– Efficiency AA’ CC’– Energy 210 GWh 210 GWh

transformed– No load loss 684 MWh 447 MWh– Load loss 1,110 MWh 921 MWh– Emissions 718 tonnes 547 tonnes– Emission savings 171

tonnes

15-May-02 34

Soft benefits

• Save energy

• Save emissions

• Noise?

• Reduced heating

• Improved lifetime

• Reliability?

• More robust against harmonics

15-May-02 35

What’s the catch?

• Increased capital outlay

• Commercial policy of suppliers

• Small amounts

• Risk of being a pioneer

15-May-02 36

Energy & emission savings potentials related to transformers & standby power

Region Energy savingsTWh / yr

CO2 SavingsMillion tonne / yr

Source

EU 22 9 THERMIE

C&EE 5 5 ECI

US 45 34China 47 52 IIEC

Japan 24 Toprunner

Total 143 100

15-May-02 37

More information

• www.efficient-transformers.org– electronic library– calculation tools

• K-Factor & Factor K• Investment evaluation spreadsheet

• www.supertrafo.com– daily, on-line measurement of energy saving for 4

high efficiency transformers installed in Poland

15-May-02 38

15-May-02 39

15-May-02 40

Super-trafo demonstration

15-May-02 41

Conclusions

• Evaluate transformers for lifetime cost– oil-cooled

• Buy only CC’ or higher• Evaluate transformer with 15-20% less loss than CC´

– dry-type• if you need the advantages• evaluate transformer with 15% less loss than HD538

• Check harmonic culture

• Consider replacement of veteran transformers