Power Transformer 2

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Power Transformer

ByDr. Tarek Saad Abdel-Salam

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• Transformers can be constructed so that they are designed to perform a specific function. A basic understanding of the various types of transformers is necessary to understand the role transformers play in today’s facilities

TRANSFORMER TYPES

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• a. Power • b. Control • c. Auto • d. Isolation• e. Instrument current • f. Instrument potential

TRANSFORMER TYPES

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Power Transformer• Power transformers are generally used in electrical power d

stribution and transmission systems. This class of transformer has the highest power, or volt-ampere ratings, and the highest continuous voltage rating. The power rating is normally determined by the type of cooling methods the transformer may use. Some commonly-used methods of cooling are by using oil or some other heat-conducting material. Ampere rating is increased in a distribution transformer by increasing the size ofthe primary and secondary windings; voltage ratings are increased by increasing the voltage rating of the insulation used in making the transformer.

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Control Transformer• Control transformers are generally used

in electronic circuits that require constant voltage or constant current with a low power or volt-amp rating.

• Various filtering devices, such as capacitors, are used to minimize the variations in the output. This results in a more constant voltage or current.

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Auto Transformer• The auto transformer is generally used in low

power applications where a variable voltage is required. The auto transformer is a special type of power transformer. It consists of only one winding. By tapping or connecting at certain points along the winding, different voltages can be obtained

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Auto Transformer

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Isolation Transformer

• Isolation transformers are normally low power transformers used to isolate noise from or to ground electronic circuits.

• Since a transformer cannot pass DC voltage from primary to secondary, any DC voltage (such as noise) cannot be passed, and the transformer acts to isolate this noise.

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Instrument Potential Transformer

• The instrument potential transformer (PT) steps down voltage of a circuit to a low value that can be effectively and safely used for operation of instruments such as voltmeters, watt meters, and relays used for various protective purposes.

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Instrument Current Transformer

• The instrument current transformer (CT) steps down the current of a circuit to a lower value and is used in the same types of equipment as a potential transformer. This is done by constructing the secondary coil consisting of many turns of wire, around the primary coil, which contains only a few turns of wire. In this manner, measurements of high values of current can be obtained

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Summary

• Power transformers are generally used in power distribution and transmission systems.

• Control transformers are generally used in circuits that require constant voltage or constant current with a low power or volt-amp rating.

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• Auto transformers are generally used in low power applications where a variable voltage is required.

• Isolation transformers are normally low power transformers used to isolate noise from or to ground electronic circuits.

• Instrument potential and instrument current transformers are used for operation of instruments such as ammeters, voltmeters,watt meters, and relays used for various

protective purposes.

Summary

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Types of power transformer

• (A) Oil Immersed Power Transformers

• (B) Dry type Power Transformers

• (C) Special Power Transformers

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• Double Wounded, Three Phase Power Transformers with On Load Tap

Changerrated 12 ► 63 MVA

• Double Wounded, Three Phase Power Transformers with On Load Voltage

Control• rated 2.5 ► 10 MVA

Oil Immersed Power Transformers

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• Electrical Network Interconnecting Transformers and Autotransformers

• Three Phase Power Transformers and Autotransformers having 3 Windings,

with On Load Voltage Control• rated 25 ► 200 MVA


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• Three Phase Power Transformers and Autotransformers without Voltage Control or with No Load Voltage

Control• rated 67 ► 160 MVA

• Three Phase Power Transformers for Drilling Plants


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• Three Phase Power Transformers for the Internal Services of the Nuclear

Power Plant

• Three Phase Power Transformers for the Internal Services of the Power Plant


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• Three Phase Power Transformers with Fixed Ratio

rated 170 ► 440 MVA

• Three Phase Power Transformers with No Load Tap Changing

rated 1000 ► 1600 kVA, in special construction


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• Transformers used to supply the Static Power Converter


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• Conditions of operation• The transformers are meant to operate in power

transport networks at the ambient temperatures of max. + 40°C and min. - 35°C.

• The altitude of the installation site is max. 1000 m above the sea level.

• At the customer's request, the transformers may be manufactured to operate in tropical environment with ambient temp. 45-55°C and protected by encapsulation for polluted areas.

Double Wounded, Three Phase Power Transformers with On Load Tap Changer

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• Construction features• The magnetic circuit is made of carlyte insulated,

grain oriented, cold rolled silicous steel sheet with low specific losses

• The windings are made of paper insulated copper wire.

• They are helical type or flat coils on the LV side and continuous in the flat coils on the HV side.

• The tank is bell or cover type, made of welded steel plate, stiffened with ribs.


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Rating (MVA)

Voltage (kV)

Uk (%)

Po (kW)

Pk (kW)

Connection group

Wdg. Material

Overall Weight

(kg)

Overall Dimensions

(LxWxH)(mm)

12 33/11 8 10.5 65 Dyn5 Cu 33400 5340x3825x3890

15/20 132/15/3.3 9/19/8 21 100 Ynyn0d Cu 56700 6415x4150x4430

16 110/22 11 18 94 YND11 Al 34800 5980x3084x4278

25 110/22 17 24 139 YNd11 Al 50200 6480x3715x4755

25 154/6.3 11 25 110 YNyn0 Cu 62800 7634x4730x4820

25 110/22 11 21 143 YNd11 Al 42400 3970x3215x4175

25 116/6.3 14 25 143 YNd11 Cu 40300 5866x3890x4476

25 154/34.5 10 24 115 YNyn0 Cu 62500 7505x4630x5635

25 110/22 11 21 143 Ynd11 Al 29650 5490x3774x4660

17.5/35 66/11 15.5 18.5 36/145 YNd11 Cu 54000 6150x4450x4435

40 110/22 1212 31 165 YNd11 Cu 59250 6305x4066x4520

40 110/6.6 18.5 34 220 YNd11 Al 62300 7380x3525x5045

50 150/15.75 21 42 190 Dyn1 Cu 110500 7375x5620x6220

63 110/22 12 55 265 YNd11 Al 80800 7070x5165x6170

63 150/10.5 12 55 300 Ynd11 Al 88150 7715x4105x6010

6.3/31.5/31.5 110/6.3/6.3 1.114-13 65 110 Dyn1yn1 Cu 121500 8250x3725x6470

63 110/38.5 13 45 260 YNd11 Cu 76000 6515x4350x5210

16 110/6.6 11 18 94 YNd11 Al 34800 5900x3084x4278

15/20 66/11 10 16 90 Dyn11 Cu 33000 4550x4630x4519

15/20 66/6.6 10 16 90 Dyn11 Cu 33000 4550x4630x4510

25 110/6.3 11 21 143 YNd11 Al 43030 5940x3772x4660

25 66/11/6.3 11 22 140 YNyn0d1 Cu 55800 6770x4230x4600

25/30 150/15/6.6 10 28 160 YNyn0d1 Cu 76000 7850x4650x5900

30/50 115/22 16.66 26 200 YNd11 Cu 79000 7000x5000x5330

40/50 161.25/6.6-6,6 10 33 159 YNy2y2 Cu 103000 7350x4600x6100

40/50 150/21 >19 25 161 YNyn0 Cu 105000 7875x5060x5900

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1. HV bushings

2. HV neutral bushing

3. LV bushings

4. Oil conservator

5. On load tap changer

6. Motor drive for OLTC

7. Pressure relief device

8. Dehydrating breather

9. Radiator

10. Jacking supports

11. Oil draining and filtering valve

12. Control cabinet

13. Wheels

14. Fans

15. Winding temperature indicator

16. Oil temperature indicator

17. Buchholz relay

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• Double Wounded, Three Phase Power Transformers with On Load Voltage

Controlrated 2.5 ► 10 MVA


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Double Wounded, Three Phase Power Transformers with On Load Voltage Control

• Conditions of operation• The transformers are destined to operate in

electric power carrying networks at the ambient temperatures of max. + 40º C and min. - 40º C. The altitude of the installation site is max 1000 m above the sea level. At the user's request, transformers being able to operate at tropical temperatures can be manufactured.

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grain oriented, cold rolled silicous steel sheet with low specific losses.

• The transformers windings are made of paper insulated copper wire and their type is: helical or continuous in flat coils on the HV side and continuous in flat coils on the LV side.

• The tank is bell or cover type, made of steel plate, welded construction, stiffened by ribs.


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Rating (MVA)

Voltage (kV)

Uk (%)

Po (kW)

Pk (kW) Connection group Bob.

Overall Weight (kg)

Overall Dimensions (LxWxH)(mm)

2.55 66/11.5 9 4.1 21 Dyn11 Cu 22325 4800x2800x4265

5 66/11.5 9 7.25 28.8 Dyn11 Cu 27200 4780x2970x4470

6.3 132/34.5 8 8.6 32 YnZn11 Cu 33300 5600x2875x4765

7.5 33/1 7.5 6.3 41 Ynd11 Cu 22900 5115x3810x3410

10 110/22 11 16 68 Ynd11 Al 32390 5505x3120x3470

10/13 132/11.5 12 10 73 Dyn1 Cu 34900 5410x5010x4600


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1. HV bushings

2. HV neutral bushing

3. LV bushings

4. Oil conservator

5. On load tap changer

6. Motor drive for OLTC

7. Pressure relief device

8. Dehydrating breather

9. Radiator

10. Jacking supports

11. Oil draining and filtering valve

12. Control cabinet

13. Wheels

14. Fans

15. Winding temperature indicator

16. Oil temperature indicator

17. Buchholz relay

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Dry type Power Transformers

• Dry type Power Transformersrated 10kVA ► 1600 kVA

• Dry type Power Transformers for Rectifier Plants and for Convertersrated 430; 550; 630; 720; 900 kVA

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Dry type Power Transformersrated 10kVA ► 1600 kVA

• Conditions of operation• The transformers are meant to supply the inner

auxiliaries of the power stations within the underground train stations and residential districts. The transformers are rated to operate in suitably ventilated closed rooms and are supplied from electrical grids free from the atmospheric surge voltages.

• The ambient temperatures are: • max. ambient temperature: +40° C • max. air daily average temperature +30° C • min. air temperature -15° C • max. altitude: 1000 m above the sea level • Protection degree: IP00 or IP20

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grain oriented, cold rolled silicous steel sheet • The windings are manufactured of glass-fiber

and enamel insulated cooper wire, impregnated in electro-insulating varnish.

• The winding types used are: cylindrical or helical on the LV side and layered or continuous, in flat coils on the HV side.

• The voltage control on the HV side is achieved at a terminal plate, by means of ringlets (bars).


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• Construction features• The HV and LV connections are manufactured of glass

fiber strip insulated copper buses. • The outlets are taken out on the transformer small side

or top, on the HV side through bushings and on the LV one through buses. Function of the customer's request and with the manufacturer's agreement, the outlets may be located otherwise too: by performing the required changes of the overall dimensions.

• The protection housing is made of steel sheet placed on a metal frame. At the top it is provided with louvers enabling air free flow. The transformer may be lifted by means of lugs provided on its structure.


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Rating (kVA)

Voltage (kV)

Uk (%)

Po (kW)

Pk (kW) Connection group

Overall Weight (kg)


10 0.38/0.048 3 0.11 0.25 Dy11 140 700x300x440

25 0.38/0.052 4 0.17 0.4 Yyn0 240 850x355x530

40 0.38/0.122 4 0.24 0.68 Yy0 300 805x350x570

60 0.5/0.23 4 0.4 1 Yy0 450 950x510x780

100 10/0.4 3.5 0.86 1.05 Yy0 1045 1925x840x1060

160 6/0.47 8 0.55 2.8 Yyn0 746 1240x440x960

200 6.3/0.4 4 0.95 2.5 Yyn0 1085 1280x620x1258

250 20/0.4 6 1.3 3.2 Dyn5 1670 1640x676x1500

315 6/0.47 4 1.4 2.4 Yyn0 2125 2340x780x1725

400 6.3/0.4 6 1.5 3.8 Dyn5 1885 2200x1000x1350

630 6.3/0.66 6 1.75 6 Dy05 2600 2155x1030x1670

630 20/0.4 6 2.3 7.2 Dyn5 2485 1840x800x1620

750 13.8/0.4 8 1.9 6.5 Dyn11 3120 1750x850x1880

800 6/0.427 6 2.1 7 Dd6 2846 1630x790x1643

900 6/0.66 6.5 2.2 6.8 Dy11 3300 2150x800x1355

1000 6/0.4 6 2.5 8.5 Dyn5 3370 2200x1050x1840

1000 10/0.4 6 2.7 8.5 Dyn5 3640 2300x1100x1950

1600 6.3/0.4 6 3 11 Dyn-5 5655 2660x1050x2360

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1. LV buses

2. HV bushing

3. Lifting lug

4. Name plate

5. Warning name plate

6. Alarms name plate

7. Grounding terminal

8. Undercarriage

9. Temperature micro relay

10. Shutter

11. Lifting lugs for housing

12. Removable cover

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Dry type Power Transformers for Rectifier Plants and for Converters

• Conditions of operation• Temperate environment in properly

ventilated closed room: • the max. ambient temperature +40°C; the

min. ambient temperature -15°C; • the max. altitude 1000m. • IP00 or IP22 protection degree (with

housing for protection).

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• Construction features• The magnetic circuit is of carlyte insulated, grain

oriented, cold rolled silicous steel sheet with low specific losses.

• The windings are made of copper wire, insulated with enamel and glass fibber impregnated in electro-insulating varnish.

• The practical winding types are: cylindrical on the LV side and continuous on the HV side.

• The insulation of the winding is made of glass fibber fabric in layers.

• The control on the high voltage range is made at a terminal box.


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Construction featuresThe connections are made of copper buses, insulated with

a glass-fibber strip. • The terminals are brought out of the shorter housing

walls through bushings for high voltage side, and through copper buses for the low voltage side.

• The protection housing is made of steel sheet, fixed on a metallic structure.

• At the upper part, it is provided with louvers and holes for air exchange and at the lower side, the transformer has a skid and earthing pad.

• The transformer lifting is made by means of lifting eyes provided on the structures.


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Rating (kVA)

Voltage (kV)

Uk (%)

Po (kW)


Overall Weight (kg)


30 60/0.38 6.5 1.4 4 Dy11 1936 1960x800x1150

430 10/0.42 6.5 1.5 4 Dy11 2060 2270x1000x2000

550 6/0.44 6.5 1.5 5 Dy11 2135 1960x760x1270

630 6/0.44 5.5 1.75 5.5 Dy11 2490 1590x840x1490

720 6/0.36 6.5 2.05 6 Dd0 2950 2100x1000x1625

720 10/0.42 6.5 1.95 6 Dy11 2925 2280x1010x1565

900 6/0.825 6.5 2.2 6.6 Dy11 3360 2220x750x1480

900 6/0.43 6.5 2.2 6.6 Dy11 3490 2220x750x1480


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1. LV buses

2. HV bushing

3. HV protection box


5. Housing

6. Lifting lugs


8. Undercarriage

9. Removable cover

10. Name plat

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Special Power Transformers

• Fire Damp Transformers• rated 100 ► 500 kVA

• Transformers Supplying the Induction Electrical Furnaces

• rated 250 kVA ► 5000 kVA

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Fire Damp Transformers

• Conditions of operation• in explosive atmosphere, in the coal mines

and other industrial departments • max. ambient temperature +40° C; min.

ambient temperature -15° C • air relative humidity 95 ± 3%; max. altitude

1000m • protection degree of the housing and

terminal boxes IP-54

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• Construction parameters• The transformer is made of:• The transformer proper, with its components: the

magnetic circuit, which is made of carlyte insulated, cold rolled siliceous steel sheet ; the windings, which are made of glass-fibber and enamel insulated copper wire, impregnated in electro-insulating varnish. The winding types used are: cylindrical on the LV side and layer type on the HV side. The winding insulation is of glass-fiber fabric in layers. Voltage control on the HV side is performed by changing the connections to the bushings.


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• Construction parameters• The LV compartment affords achieving electrical

diagram of the LV wiring within the explosion-proof housing and has the following components:

– USOL automatic breaker provided with maximal and overload protection, with remote making and breaking tapping device, manually driven at remote making and breaking operations;

– insulation resistance permanent and warning control device, disconnecting the secondary circuit when the insulation resistance decreases below a certain value; measuring instruments : ammeter, voltmeter, current transformer; terminal box with removable bushings affording connection of the supply outlets of the users, signalling-control;


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• Construction parameters• The HV side duty is to energize and de-energize the

transformer unit. Components and instruments: load special separating switch for making and breaking the no load currents in the dry type transformer; it is manually operated, mechanically and electrically interlocked by means of the LV circuit breaker; device to visually check voltage availability at the load separating switch inlet terminals before penetrating into the HV compartment; mini-circuit breaker which automatically opens the dry type transformer supply circuit, before penetrating into the HV compartment; terminal box with removable bushings affording to connect the supply and control signaling incoming wires.


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• Construction parameters• The fire dump housing is made of steel sheet,

having different thickness for the 3 chambers. The LV and HV compartment housings are provided with doors ensuring safety, as per STAS 6877/2. The housing of transformer proper is provided with tubes for heat exchange/dissipation. Outside, the housing is provided with: 4 wheels-undercarriage with 375 mm diameter, having the gauge required by the customer, limit facility on the length, lifting lugs.


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Rating (kVA)

Voltage (kV)

Uk (%)

Po (kW)


Overall Weight (kg)


250 6/0.4 3.5 1.3 2.3 Yy0 3925 2970x930x1595

400 6/0.4 4 1.5 3.1 Yy0 4376 2970x930x1595

400 6/0.69 4 1.5 3.2 Yy0 4250 2970x930x1600

500 6/0.69 3 2.75 2.6 Yy0 4857 3125x930x1325

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. LV buses

2. HV bushing

3. Lifting lug

4. Name plate

5. Warning name plate

6. Alarms name plate


8. Undercarriage

9. Temperature microrelay

10. Shutter


12. Removable cover

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Transformers Supplying the Induction Electrical Furnaces

• Conditions of operationFurnace capacity t 0.5 1.1 2 3 6.3 12 20

Transformer rating KVA 250 400 630 1000 1600 2800 5000

6000 6000 6000 6000 6000 6000 6000

10000 10000 10000 10000 10000 10000 10000 Primary voltage V

20000 20000 20000 20000 20000 20000 20000

Secondary voltage

V 550-125 550-125 550-125 550-125 550-125 1000-222 2500-500

Steps number 10 10 10 10 10 10 10

Connection group vectors Dyn5 Dyn5 Dyn5 Dyn5 Dyn5 Dyn5 Dyn5

800 900 1750 2500 3000 4500 6500 No load losses W

850 1100 1950 7200

6800 7600 8000 12000 21000 26000 38000 Copper losses W

8500

No load current % 2.1 1.9 1.8 1.6 1.6 1.4 1.2

Impedance voltage % 6 6 6 6 7 6 7

2580 2750 3650 5200 6250 9350 15500 Overall weight Kg

2600 2900 4200 5300 9450 17000

930 960 1250 1600 1850 2850 4100 Oil Weight

1000 1410 1700 5000

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Transformers Supplying the Induction Electrical Furnaces

1. Oil conservator

2. Oil filling plug

3. Oil level indicator

4. Buchholz relay

5. Tap changer

6. Silicagel breather

7. Untanking part lifting lug

8. Lifting lug

9. Name plate

10. Dial type thermometer

11. Oil draining valve

12. Undercarriage

13. Earthing terminal

14. HV bushing

15. LV bushing

Power Transformer 2

Documents

induction

fire damp

load tap changer

low specific

low power

phase power

ground electronic

load voltage