01) Transformer Lecture_140305

8/6/2019 01) Transformer Lecture_140305

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C.C.JENSEN A/S - Kim Kjr March 2005 1

Transformer Lecture

The Transformer and its Maintenance

CJC V30 Transformer

Oil Vacuum FiltrationUnit

&

Ion Exchange

Filtration Units


2/50


Transformer Lecture

The V30 Vacuum FilterInstalled at Rathkeale Power Station, Ireland


3/50


Transformer Lecture

V30 Mo I Rana, Norway


4/50C.C.JENSEN A/S - Kim Kjr March 2005 4

Transformer Lecture

V30 ProductionC.C.JENSEN A/S Svendborg


5/50


Transformer Lecture

Hypothesis

Oil

O2

Acids

H O2

Paper ageing:

Water & acids

acceleratesageing.

Water is

formed

H O2

Oil reclaiming

Transformerrefurbishment

Acids are formedby oxidation

Source: L. Lundgaard, SINTEF Energiforskning AS


6/50


Transformer Lecture

Ageing Factors

Catalysts:

Water.

Copper.

Oxygen.

Accelerators:

Heat.

Ageing products.

Dirt.

Vibrations / overload.

Electrical stress /voltage waves.


7/50


Transformer Lecture

Ageing Processes

Pyrolysis(heat)

Hydrolysis(reactions with water)

Oxidation(reactions with O2)


8/50


Transformer Lecture

The Transformer and its MaintenanceWhen oil (CxHy) and O2 react chemically the oil starts to deteriorate (oxidize, age).

Sludge: Reduces the break-down voltage. Reduces the cooling effect.

Deteriorates the cellulose. Acts as catalyst for further

oxidation.

Acids: Create corrosion

Acts as catalyst for further oxidation

Water:

Deteriorates the cellulose.

Reduces the break-down voltage.

Acts as catalyst for furtheroxidation.

Gasses: Among others CO, CO2, O2, H2,

CH4 , C2H4, C4H6, C6H8.

During this reaction the following compounds are formed:

The aging process dramatically increases the higherthe oil temperature is and if catalysts are present

(sludge, water, acids, cupper).


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Transformer Lecture

Development in Transformer Design

Source: Grestad Diag. & Rehab. AS - SDMyers.

0,501979

0,651977

0,751975

1,501960

2,251945

4,501930

9,001915Ltrs of oil / kVaYear


10/50


Transformer Lecture

Causes of Failure

70 % of all failures happens on

transformers older than 30 years.

50 % of the failures originates in OLTC andlead-in bushings.

15-20 % are due to reduced stability; waterand particles in the isolation.

3-5 % due to far progressed ageing.

10-15 % due to core mechanically

weakened by twisting.

Old constructions may have gas problemsdue to induction loss.

Source: Grestad Diag. & Rehab. AS Doble og ZTZ


11/50


Transformer Lecture

Lowering the Oxygen Concentrationslows Down Oxidation

Depolymerisation of Cellulose. Accelerated Ageing (130 C)With/ Without P resence of Oxygen

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

0 20 40 60 80 100 120 140 160 180 200

Time [days]

DP-value

No OxygenOxygen


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Transformer Lecture

Ageing of Cellulose No Oxygen Present

Ageing under a Nitrogen blanket. These curves are interesting because they showthe effect of no oxygen (same as having an efficient Nitrogen blanket). Pleasenote the relative speed of the ageing btw. 0% and 1% moisture. This change in

reduction of DP is much more severe than from 1-2% moisture.Source: Roland Agnemo


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Transformer Lecture

Oxygen- affecting Transformer Life Length

0,01

0,10

0,30

1,00

3,00

10,00

30,00

100,00

0,03

Y

ear

90 110 130 150 170 190

O C

LowOcontent

2HighOcontent

2

Source: Grestad Diag. & Rehab. AS . / SDMyers.


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Transformer Lecture

The Oxygen-Free TransformerDEOX - ASEA 1977 (today ABB)

In the years 1976 & 1977 ASEA published articles about the oxygen-free transformer. It was tested

on a transformer with rubber membrane and continuous degassed including filtration.

Specification:

Oxygen: < 300 l/l.

Water: < 0,5 %.

Particles: < 5 m.

Gas-free oil: 200 N/m2,


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Transformer Lecture

Life Expectancy can be Calculated

from Water Content and Temperature.

yeare***A

DPLifeExpected TEnd 273

13350

36524

1000

11



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Transformer Lecture

The Model Facilitiates Analyses of Impactfrom Temperature and Water.

20oC givesacceleration ofe2 = 7.4.

Dry to wet givesacceleration ofe3 = 20.

Wet and 20oC givesacceleration ofe2+3 = 7.4 x 20 = 148.



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Transformer Lecture

Acid generation accelerates when water and oxygen arepresent. Acid in turn causes acid-hydrolysis.

f


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Transformer Lecture

Gases

generatedduring a

FaultCombustible GasGeneration vs.approximate Oil

DecompositionTemperature.

T f L


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Transformer Lecture


Decomposition of celluloseCarbon dioxideCO2

CarbonmonoxideCO

ArcingAcethyleneC2H2

Partial dischargesHydrogenH2

EthyleneC2H4

High oil temp.EthaneC2H6

MethaneCH4

Carbon dioxideCO2

CarbonmonoxideCO

Normal ageingMethaneCH4

HydrogenH2

ReasonGas

Gas Analysis

T f L


20/50


Transformer Lecture

CO and CO2is produced through paper Ageing

8% vann 0,5% vann

CO / CO2:

1/10 = normal oilageing

1/1 = very hot

2/1 = very veryhot

1/5 = normalageingof paper

water water

CO2: More than 2,000 ppm is alarming!

T f L t


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Transformer Lecture

CO / CO2 RatioCO/CO2 Ratio

0

0.5

1

1.5

2

2.5

0 5 10 15 20 25

Probability of failure [% ]

CO/CO2ratio

CO/CO2 Ratio

CO/CO2 Ratio curve for

recorded failures inCanada on conservatortype transformerswithout tap changerscommunicating with themain body.

Acceptable dissolvedgas-in-oil concentrationlevels in power andinstrument transformersas function of age.

2,500 transformers.

Source: Lars Arvidsson.M.Duval, F.Langdeau,P.Gervais,G.Belanger.

T f L t


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Transformer Lecture

Oil Regeneration & Reclaiming

Will remove some moisture from paper.But with oil in the transformer themoisture transport takes time.

Will remove some acids from paper.Oil acidity is reported to be stable and lowafter fluidex treatment (how many passes).

Source: L. Lundgaard, SINTEF Energiforskning AS.

T f L t


23/50


Transformer Lecture

TransformerFeatures:

Working at 20C 1 ton of paper 10 tons of oil 10 ppm water measured

in oil

Calculation:

10 ppm of water 10 mg/kg 10 g/ton in 10 tons of oil:100 g of water.

4,6% of 1 ton of paper 46 kg of water.

100 g of water in oil and 46 kg ofwater in paper 99,8% of water incellulose.

DegasserFeatures:

Flow 1000 l/h Removal efficiency 100%

Calculation:

We can clean 24 tons in per 24

hours - we have 10 g per ton, sowe can remove 240 g per 24hours.

We have totally 46,100 g of waterin the transformer 46,100 g / 240

g = it takes 192 days to remove allwater in this transformer.

Transformer Lecture


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Transformer Lecture

Water in Oil Water in Cellulose Relation

Log(Water ppm) = A B/TWhere A=7.09-7.42; B=1567-1670

855777880100

64859666390

48445049180

35533435870

25524325560

18017417950

12412212240

84838230

55565320

35363310

2223200

ShellGriffinCommenT (C)

Transformer Lecture


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Transformer Lecture


20 CO

30 CO

50 CO

70 CO

90 C O

Water in oil (ppm)

Waterincellulose(W%)

10

8

6

4

2

00 20 40 60 80

Oil/Cellulose Humidity Correlation- at different oil temperatures

Transformer Lecture


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Transformer Lecture

Summarizing

End-of-life of transformer =

End-of-life of cellulose isolation.

Heat, water, oxygen and ageingproducts are severely contributing

to transformer ageing.

The possibilities of reconditioningtransformers on site are good:

drying,

continuous degassing and

regeneration.

Transformer Lecture


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Transformer Lecture

Conclusion

By lowering the Oxygenconcentration in the oil, theoxidation (degradation) of thecellulose is reduced.

By removing water from the

transformer the remaining lifetime is increased.

By removing particles the breakdown voltage is increased.

By reducing acidity levels thetransformer cellulose is betterprotected against ageingacceleration.

Transformer Lecture


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Transformer Lecture

Highly efficientDeaeration

&

Drying of

Power Transformer Oils.

Vacuum Filtration Unit

Transformer Lecture


29/50


Transformer Lecture

V30 Vacuum Filter - Principle of Operation

= Oil Inlet= Oil Outlet

= Gas Outlet

= Oil Drain

AB

C

D

A

B

C

D

Transformer Lecture


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Transformer Lecture

Transformer Lecture


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Transformer Lecture

V30 Efficiency of Water RemovalExample: 20 ppm in >> 6 ppm out

The V30 will remove moisture down to 4 ppm given timeenough. The curve above shows the efficiency of full flowand minimum pressure of 2 mBar.

Transformer Lecture


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Transformer Lecture

Water Removalon a very dry Transformer, Stubbekbing

0

1

2

3

4

5

6

06-06-03

07-06-03

08-06-03

09-06-03

10-06-03

11-06-03

12-06-03

13-06-03

time

watercontent

in/out[ppm]

ppm in

ppm out

Transformer Lecture


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Transformer Lecture

Oxygen RemovalV30 StubbekbingO2 Concentration vs time.

Stubbekbing, Denmark. 8000L oil in transformer.

1307

5870

1940

200580720

20910

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

02-03-2003

22-03-2003

11-04-2003

01-05-2003

21-05-2003

10-06-2003

30-06-2003

20-07-2003

09-08-2003

Time

Oxygenconcentration

inoil[ppm]

V30 Stopped

V30 Started

V30 Started

Transformer Lecture


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Transformer Lecture

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

24-0

7-1998

01-1

1-1998

09-0

2-1999

20-0

5-1999

28-0

8-1999

06-1

2-1999

15-0

3-2000

23-0

6-2000

01-1

0-2000

09-0

1-2001

19-0

4-2001

28-0

7-2001

05-1

1-2001

13-0

2-2002

24-0

5-2002

01-0

9-2002

10-1

2-2002

20-0

3-2003

28-0

6-2003

06-1

0-2003

14-0

1-2004

Time

Gasinoilconcentration[ppm]

O2 Concentration INLET

CO2 Concentration INLET

V30Degasser

Started

Oxygen Removalwith V30, Ljusdal

Transformer Lecture


35/50


Transformer Lecture

0

2

4

6

8

10

12

0

1-12-1996

3

0-05-1997

2

6-11-1997

2

5-05-1998

2

1-11-1998

2

0-05-1999

1

6-11-1999

1

4-05-2000

1

0-11-2000

0

9-05-2001

0

5-11-2001

0

4-05-2002

3

1-10-2002

2

9-04-2003

2

6-10-2003

Tid

Koncentrationsforhold[O2ppm/CO2ppm

]

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

KoncentrationO2[ppm]

O2/CO2

O2 Concentration IND

V30 Started

Oxygen Content & Carbon Monoxide Generationi.e. Rate of Paper Degradation

Transformer Lecture


36/50


Transformer Lecture

V30 Advantages

Removes OXYGEN from the transformer oil.Down to 200 ppm.

Removes WATER from the transformer oil.

Down to 4 ppm.

Removes PARTICLES from the oil.Down to 0.4 micron.

With an ion exchange filter ACID is removed.Down to 0.01 mg KOH/g.

Transformer Lecture


37/50


Results using a V30 / Ion Exchange Filter

months0.00500.0500 - 0.1500Tan delta@ 90

C

weeks170C95CBubble FormationTemp

weeks200 2,000 ppm20,000 25,000 ppmOxygen

months0.01 - 0.02 mg KOH/g0.10 - 0.25 mg KOH/gAcid

days>75 kV35 - 60 KvBreakdown

Voltage/2.5mm

years4 ppm20 - 40 ppmWater in oil

years0.6 - 1.1%2-7%Water in cellulose

days11/814/10 - 16/13Particles, ISO

Timeframe

After filtrationTypical value for

aged system

ISO-standard. The old 5 my and 15 my standard.Source: EFFECT OF PARTICLES ON TRANSFORMER

DIELECTRIC STRENGTH Working Group 12.17 - CIGRE

Transformer Lecture


38/50


CJC V30 Safety Features

High pressure alarm. In case the vacuum pump fails to keep the pressure below a preset value.

In case the transformer starts gassing and the gas content of the oilincreases rapidly. Adjustable from 2-250 mBar (down to 500 ppm gas in oilincrease. A Buchholz relay can only detect free gas >70,000ppm H2 ).

Low level alarm. In case the oil level inside the vacuum chamber falls below a preset value.

Medium level stops the oil pump, low level stops the system.

Vacuum pump low vacuum oil level alarm.

Drip pan oil sensor. In the unlikely case of leakage. The system shuts itself off.

Foam sensor that shuts vacuum off. Oil in (as foam) cannot leave the system.

One way valve on vacuum pump. Air/fluids cannot enter only leave the system.

All alarms on potential free relay.

Transformer Lecture


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Shut off valvesoperated bydifferential oil

pressure monitoringsystem on inlet.

Non return valve on

outlet.

Optional

CJC V30Safety Features

Transformer Lecture


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V30 Vacuum FilterEarly Warning Systems

1. Gassing alarm on V30 indication of a high thermal fault inthe transformer.

2. Increased water in oil detection indication of a low thermalfault.

3. Specific gasses produced high thermal fault moresensitive than gassing level. Direct online gasmeasurement. Hydrogen, Methane, Carbon Monoxide.

4. Abnormal rise in oil temperature detects large scale

heating.

5. ComPosIT GSM datalogger. Alarm via sms. Data on WWW.

Especially the gas sensor will yield important information and

a very early warning for a possible fault.

The CJC V30 Vacuum Filtration Unit equipped with standard as well as optional sensors will operate as an earlywarning system for the transformer. This includes:

Transformer Lecture


41/50


Results obtained running a CJC V30

for 5.5 Months on a Power Transformer.

Data for the transformer:Distribution transformer

40 MVA110/10.5 kV

Oil: TR 25 A

Oil weight: 20,000 kg

Cooling system: OFAF

Conservator: Open/Shared, no tap changer

Produced by: Electroputere Craiova, 1970

Filaret T3 Filaret, Bukarest, Romania

The CJC V30 Vacuum Filter was startedup on 26/2-2004.

Transformer Lecture


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MoistureThis curve shows the saturation of the oil with terms of water.

A curve which corresponds to the relative humidity in air.

Water activity in oil [absolute water saturation of the oil]

0.0000.020

0.040

0.060

0.080

0.100

0.120

0.140

0.160

0.180

0.200

0.220

0.240

0.260

0.280

0.300

0.320

0.340

2004-02-13

2004-02-23

2004-03-04

2004-03-14

2004-03-24

2004-04-03

2004-04-13

2004-04-23

2004-05-03

2004-05-13

2004-05-23

2004-06-02

2004-06-12

2004-06-22

2004-07-02

2004-07-12

2004-07-22

2004-08-01

2004-08-11

2004-08-21

Time

Wateractivity

[%/100]

aw [%/100]

25 per. Mov. Avg. (aw [%/100])

When the CJC V30 was first installed (26/2-2004) the saturation ofwater in oil was about 18%, now it has been lowered to below 6%.

Transformer Lecture


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Water Content in ppm

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

2004-02-

23

2004-03-

04

2004-03-

14

2004-03-

24

2004-04-

03

2004-04-

13

2004-04-

23

2004-05-

03

2004-05-

13

2004-05-

23

2004-06-

02

2004-06-

12

2004-06-

22

2004-07-

02

2004-07-

12

2004-07-

22

2004-08-

01

2004-08-

11

Time

Waterinoil[ppm]

ppm calculated

20 per. Mov. Avg. (ppm calculated)

From startup values of about 14-18 ppm we have now reached values down to 6ppm. When the unit was started the transformer had been shut down for a few

days and the temperature was only 4 C. Hence the initial rise in water content.

This curve shows when the saturation values have been converted into ppm.

Transformer Lecture


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Water ConcentrationWater content in oil [ppm] and oil temperature [C]

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

2004-07-09

2004-07-11

2004-07-13

2004-07-15

2004-07-17

2004-07-19

2004-07-21

2004-07-23

2004-07-25

2004-07-27

2004-07-29

2004-07-31

2004-08-02

2004-08-04

2004-08-06

2004-08-08

2004-08-10

Time

OilTemperature[C]

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

Watercontent[PPM]

Oil temperature [C]

ppm calculated

30 per. Mov. Avg. (ppm calculated)

30 per. Mov. Avg. (Oil temperature [C])

Water concentration during the latest month. As can be seen fromthe curve the water content is still falling, but since the values are verylow the water removal rate has somewhat slowed. Note the daily

fluctuations in oil temperature.

Transformer Lecture


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Accumulated Removed WaterAccumulated amount of water removed from the transformer insulation [Liters]

0.0

0.5

1.01.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

200

4-02-23

200

4-03-04

200

4-03-14

200

4-03-24

200

4-04-03

200

4-04-13

200

4-04-23

200

4-05-03

200

4-05-13

200

4-05-23

200

4-06-02

200

4-06-12

200

4-06-22

200

4-07-02

200

4-07-12

200

4-07-22

200

4-08-01

200

4-08-11

Time

Remove

dWater(accumulated)

[L]

Accumulated Removed Water [L]

This curve is calculated based on the known efficiency of the V30.

So far about 4.5 Liters of water have been removed.

Transformer Lecture


46/50


AcidOrganic acidity mg KOH/ g oil. The CJC V30 removes water from the oil. Since some acids

are w ater so luble som acid is also removed f rom the transfo rmer.

0.178

0.118

0.148

0.1880.178

0.2080.2040.21

0

0.05

0.1

0.15

0.2

0.25

24-07-1998 06-12-1999 19-04-2001 01-09-2002 14-01-2004 28-05-2005

Date

TAN

[mgKOH/g]

Organic acidity mg KOH/g oil

Startup of CJC V30

From the curve it can be seen that the TAN has beenlowered since startup of the CJC V30 vacuum filter.

Transformer Lecture


47/50


Water Removal on T3Water removal on T3, Filaret, Bucarest, Romania. 20000L oil. 40MVA.

Water Content in oil at T=36 C.

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

2004-02-22

2004-03-07

2004-03-21

2004-04-04

2004-04-18

2004-05-02

2004-05-16

2004-05-30

2004-06-13

2004-06-27

2004-07-11

2004-07-25

2004-08-08

2004-08-22

Time

WaterContent[ppm]

The water content of the oil is highly

temperature dependent due to the equilibrium

with the transformer cellulose. The graph showsthe water content at 36 C. I.e. measurements

taken each time the oil temperature was exactly

36 C.

As can easily be seen from the curve the V30

has lowered the water content in the oil to

roughly 6-7 ppm. Variations are caused by daily

temperature fluctuations. A moisture reading at36 C when the temperature is rising (positive

gradient, i.e. transformer heating up) tends to

yield lower moisture contents than a reading

when the temperature is falling (negative

gradient, i.e. transformer cooling down).

Measurements taken at a temperature of 36 C.

Transformer Lecture


48/50


Water Removal on T3Other parameters that have been improved though only slightly are:

Density: From 0.887 g/mL at startup to 0.884 g/mL on 2004-05-06(relative density at 20 C).

Color: From deep low red at startup to low red on 2004-05-06.

Inflammability: From 142 C at startup to 144 C on 2004-05-06.

Breakdownvoltage: From 232 kV/cm at startup to 250 kv/cm on 2004-05-06.

Dissipation factor(tan d) at 90 C [%]: From 16.9 at startup to 12.36 on 2004-05-06.

Index of refraction: From 1.4904 at startup to 1.4883 on 2004-05-06.

Transformer Lecture


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Water Removal on T3Calculated data from the transformer degassing and drying monitoring:

The average oil temperature is 36.4 C

The CJC V30 has so far removed 4.48 L of water from the cellulosicinsulation

That corresponds to 27.02 mL/day (7.2% of the total moisture)

The output water content of the V30 is 3 ppm at the current input of 6ppm

Based on estimations of the insulation mass, water measurements andwater in oil/water in cellulose equilibrium curves the total amount of water

at startup was 61.92 L.

Now 57.4 L remain. At the current rate of drying the CJC V30 will haveremoved 50% of the moisture in 3.1 years. 2.7 remaining.

Transformer Lecture


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Water Removal on T3The literature states that reducing the moisture by 50% will double the remaining life time ofa transformer.

If the remaining life time of the transformer at startup was 15 years then removing 7.2 % of

the moisture, assuming a linearity between water removal and life extension, will extend thelife time by:

50% reduction = > 15 years life extension7.2% reduction = > 2.25 years life extension (achieved in 166 days)

If we rate the price per MW at the Danish 1990 level (100,000 DKK per 1MW), then a new

transformer of 40MW would cost 4,000,000 DKK or roughly 0.5 mio. EUROS.

Interest levels in Europe are roughly 4%. Thus postponing an investment of 0.5 mio. EUROSby 2.25 years would mean a saving of 4% of 0.5 mio EUROS in 2.25 years.

This corresponds to 45,000 EUROS.

Thus by running only 166 days the V30 has savedthe transformer owner 45,000 EUROS.

Thus the payback time for a V30 is far lower than

166 days.

01) Transformer Lecture_140305

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Transcript of 01) Transformer Lecture_140305