technical specification for oil-immersed distribution ... 08-… · 5 vector group 4 6 rated power...

Ministry Of Electricity and Renewable Energy وزارة الكهرباء والطاقة المتجددة

Egyptian Electricity Holding Company الشركة القابضة لكهرباء مصر

EDMS 08- 200- 2 EEHC DISTRIBUTION MATERIALS SPECIFICATION

Date: 22-12-2020

0

EDMS 08-200-2

TECHNICAL SPECIFICATION

FOR OIL-IMMERSED DISTRIBUTION TRANSFORMERS

(CONVENTIONAL & HERMETICALLY SEALED)

25 KVA up to 5000 KVA 22 / 0.4 KV




Date: 22-12-2020

1

EDMS 08-200-2

TECHNICAL SPECIFICATION

FOR

OIL-IMMERSED DISTRIBUTION TRANSFORMERS

(CONVENTIONAL & HERMETICALLY SEALED)

25 KVA up to 5000 KVA, 22 / 0.4 KV

Issue: Dec.-2020 / Rev- 2

1/7/0201سيتم العمل بالمواصفة في

( توجد بنود اختياريةOptional items .يجب تحديدها بواسطة شركة التوزيع قبل الطرح )




Date: 22-12-2020

2

CONTENTS

1 Scope 4

2 Applicable standards 4

3

IEC 60076 for power transformer

Part 1 General

Part 2 Temperature rise

Part 3 Insulation levels and dielectric tests

Part 4 Lightning impulse and switching impulse testing

Part 5 Ability to withstand short circuit

Part 7 Loading guide for oil-immersed power transformers

Part 20 Energy Efficiency

IEC 60214 Tap Changer

IEC 60437 Radio interference test on high-voltage insulators.

IEC 605507 Artificial pollution tests on high-voltage ceramic and glass

insulators to be used on a.c. systems

IEC 60137 Bushings for alternating voltages above 1KV.

IEC 60296 For new insulating oil transformer

EN 50464-4 Endurance test (tank test for hermetical sealed TR.).

Environmental conditions

4

4 Voltage ratio 5

5 Vector group 5

6 Rated power 5

7 Tapping range 5

8 Overload capacity 5

9 The Capability of withstanding short circuits 6

10 Limits of temperature rise 6

11 Cooling 6

12 Insulation level 6

13 Impedance voltage 6

14

Bushings 6




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15 Core 7

16 Windings 8

17 Transformer oil 8

18 Oil expansion conservator 8

19 Tank 8

20 Accessories 8

21 Wheels 9

22 Name plate 9

23 Transformer losses 10

24 Penalty and rejection 10

25 Transformer testing 11

26 Instruction manuals 12

27 Drawings 13

28 Spare parts 13

29 Warranty 13

30 Max. permitted power losses of transformers (at 95ºc) 14

31 Guarantee tables 14




Date: 22-12-2020

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1. Scope

This specification covers the supply of three (3) phase conventional or hermetically sealed, two-

winding oil immersed distribution transformers (22/0.4KV). The transformer should be designed,

for indoor installation/outdoor with high voltage and low voltage porcelain bushings provided with

screwed stems and nuts with washers.

2. Applicable Standards

The transformers should comply with the latest edition of IEC publications Unless otherwise

specified in this specification, should comply with the latest edition of IEC standards as follows:

IEC 60076 for power transformer

Part 1 General

Part 2 Temperature rise

Part 3 Insulation levels and dielectric tests

Part 4 Lightning impulse and switching impulse testing

Part 5 Ability to withstand short circuit

Part 7 Loading guide for oil-immersed power transformers

Part 20 Energy Efficiency

IEC 60214 Tap Changer

IEC 60437 Radio interference test on high-voltage insulators.

IEC 605507 Artificial pollution tests on high-voltage ceramic and glass insulators to be

used on a.c. systems

IEC 60137 Bushings for alternating voltages above 1KV.

IEC 60296 For new insulating oil transformer

EN 50464-4 Endurance test (tank test for hermetical sealed TR.).

3. Environmental conditions

The transformers should be manufactured for the local service conditions as: -

Altitude less than : 1000 meters

Ambient temperature : -5°C to +45°C (50°C as an option)

(35°C monthly average of the hottest month, 25°C yearly average)

Maximum Relative humidity : 95 %




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4. Voltage ratio

The ratio of the transformers should be (22000)/400v, + 0.5% as a tolerance, 50Hz at no-load.

5. Vector group

The winding connection group of the transformers should be delta on the primary side and star on the

secondary side in accordance with the vector group Dyn11 as specified in IEC60076.

6. Rated power

The transformer should be able to deliver for an unlimited period of time at the main tapping of the

tap changer, the maximum continuous power rating of (25-50-63-100-160-200-300-400-500-630-

800-1000-1250-1500-1600-2000-2500-3000-3500-4000-5000kVA) without exceeding the

allowable temperature rise limit, if the applied voltage is equal to the rated voltage and the supply is

equal to its rated frequency.

7. Tapping range

The transformers should be equipped with 3 phase, 3 wires, and lockable manual off load tap

changer, on the high voltage winding. The tap changer switch is mounted on the tank cover.

The voltage regulation should be affected in seven steps having the following sequences (referred

to input voltage):

Tap No 1 (+5 %)

Tap No 2 (+2.5 %)

Tap No 3 (0 %)

Tap No 4 (-2.5 %)

Tap No 5 (-5 %)

Tap No 6 (-7.5 %)

Tap No 7 (-10 %)

8. Overload capacity

Permissible overload capacity according to IEC 60076-7.




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9. The Capability of withstanding short circuits

Transformers should be capable of withstanding, without damage, the thermal and mechanical effects

of short circuits at the terminals for 3 sec. duration (S.C. level of 22KV network is 500 M.V.A).

10. Limits of temperature rise

The transformer should be able to deliver its max. continuous ratings, without exceeding the

permissible temperature rise limits:

Top oil level temperature rise 45K

Winding temperature rise measured by resistance method 55K

Hot spot 60 ºC

11. Cooling

Cooling is by natural circulation of oil internal to the transformer and by external air i.e.

ONAN/ONAF (option as per ..EDC requirements).

12. Insulation level

The following test voltages should be applicable to the transformers:

a. High voltage impulse withstand voltages: 125KV for indoor and 145KV for outdoor.

b. Power frequency withstand voltage : 50 KV/ 1 minute

c. Low voltage Power frequency withstand voltage: 3 KV /1 minute

13. Impedance voltage

The impedance at mid-tap should be as follow: at 95 ºC

4 % for transformers (25-50-63- 100-160-200-300-400-500-630 KVA)

5 % for transformers (800-1000-1250 KVA)

6 % for transformers (1500-1600-2000-2500 KVA)

7 % for transformers (3000- 3500-4000-5000 KVA)

14. Bushings

Bushings are of porcelain and generally comply with the requirement of IEC60137.

The minimum creepage distance should not be less than 2 cm/ KV for indoor, 4 cm/KV for outdoor .

The high voltage bushings should be fitted with duplex arc gap set at 65 mm.




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For transformers with a rating from 500 KVA and higher, the low voltage bushing should be provided

with copper flags and for transformers with ratings starting from 300 KVA, the low voltage bushing

should be provided with suitable copper bars or copper flag.

MV bushings should be labeled U, V, W by using indelible black color paint on the tank cover (rivet

metal). Phase identification by adhesive stickers is not acceptable.

L.V bushings should be labeled u, v, w by using indelible black color paint on the tank cover (rivet metal).

Phase identification by adhesive stickers is not acceptable.

For outdoor transformer (Option as per ...EDC requirements) the surge arrestor (gap less than metal

oxide) 10KA, 24KV max. continuous operating voltage 20KV ± 5% (leakage pass 4cm/Kv at least)

should be installed with medium voltage bushing.

15. Core

The core should be made of low loss steel lamination which are made of cold rolled grain oriented,

annealed, high permeability, non-ageing, silicon steel type .

The lamination should be insulated with suitable varnish or paint, solid insulation is not

acceptable.

The core, framework, clamping arrangement & general structure should be mechanically robust to

withstand any shocks to which they may be subjected during transport, installation, service &

faults.

The core construction should provide efficient cooling of its internal parts.

The core joints should be properly interleaved, precautions should be taken to keep the noise a level

as shown at table -1, according to rated capacity and at measured distance of 1(one)meter, at mid

tap & no-load & eliminate vibration in the core when loaded & to diminish harmonic voltage as far

as possible especially the third harmonics.




Date: 22-12-2020

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16. Windings

The winding conductors should be made of the best quality, high conductivity electrolytic copper,

complying with the requirements of the IEC publication max. flux density in the yoke should not be

more than 1.6 tesla.

The windings should be clamped effectively so that they withstand shocks and vibrations during

transport and forces produced by the most severe short circuit currents as indicated in item “9” of

this specification.

17. Transformer oil

The oil should be as per latest revision of specification EDMS 25-401-1

18. Oil expansion conservator

It should be made of sheet steel with an adequate capacity to allow for the extreme changes in the

oil level e.g. when the transformer is off circuited at 0ºC and when the transformer is full loaded at

45ºC ambient. The quantity of oil should be plainly marked on the conservator. The conservator

should be provided with oil level indicator (sight glass at low voltage side), dehydrate breather with

orange silica-gel, oil filling and drain plugs and a connection pipe for connecting the oil to the

transformer.

19. Tank

The transformer tank should be made of best quality plate steel with bolted cover fitted with

neoprene cork seals suitable for temperatures as specified in this specification. The tank should

be rigid enough to withstand the mechanical stresses due those occurring during transformer

lifting and transport, without deformation and also due to effects of S.C. inside the transformer.

Radiators should be welded to the tank.

If the transformer is hermetically sealed (option as per …EDC requirements)

The tank should have sufficient expansion for oil breath, and should withstand an internal

presser of 30 KN/m2

The transformer tank can be hermetically sealed by means of a nitrogen cushion.

20. Accessories

1- Drain plug complete with control tap

2- Welded lifting shackles




Date: 22-12-2020

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3- Tank earthing, two M 10 stud with nut washers should be used.

4- Dial thermometer for oil temperature indication reading with a range 0-120°C (with two

contacts)

5- Buchholz relay with alarm and trip contacts. (for ratings ≥ 500 KVA)

In the case of hermetically sealed transformers, the following should be installed:

Pressure Relief valve (PVR).

A vent should be provided to prevent rupturing of the transformer. This should be capable of

withstanding the variations of pressure in normal service.

DGPT2 device.

21. Wheels

The enclosure base should be fitted with 4 wheels (bi-directional) to facilitate moving of the

transformers during installation in two perpendicular directions. Wheels should have a locking

facility to secure the transformer in its position.

22. Name plate

Transformer serial No. and rated power should be engraved on tank cover at LV side. Each

transformer should be fitted with a name plate of weather proof materials fitted in a visible

position, showing the information listed below. Entries on the plate should be indelibly marked by

etching or engraving:

a) Manufacturers serial number

b) Year of manufacture

c) IEC Codes.

d) Customer (...EDC) P.O No.

e) Cooling type.

f) Type: Conventional /Hermetically Sealed.

g) Number of phases

h) Rated power

i) Rated frequency

j) Rated voltages




Date: 22-12-2020

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k) Rated currents

l) Vector group

m) Impedance voltage

n) Type of oil

o) Total weight / Weight of oil

p) Connection diagram

q) Short circuit duration

r) A table giving tapping voltages of the positions

23. Transformer losses

The transformer should be designed for minimum losses, when comparing between different

tenders, the present worth value of the annual capitalized cost of guaranteed losses in the

transformers should be added according to the following formula: -

P. w = K x 8760 x C [Wi + (LS.F)( P2 )Wcu ]

Where

K = Present worth factor (L.E)

K = ((1+i)N -1) / i (i+1)

N )

i: latest interest rate from Central Bank of Egypt.

N: number of years. (20 years)

C = Cost of KWH. (According to the max commercial cost of KWH and can be adjusted as

per EEHC latest update)

LS.F = Loss factor for the load = 0.4.

Wi = Iron losses in KW at rated voltage and main tapping

Wload = Load losses in KW at full load and 95ºC.

P = Peak load (P.U.) = 0.8.

The values of the required losses are attached in table (1)




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24. Penalty and rejection

24-1 Rejection of Material:

If during inspection tests at the works attended by the customer representative engineer any

material is found to be defective or not manufactured according to the specifications agreed upon

the customer representative engineer have the right to reject such material if he is not convinced

that it can satisfactorily be repaired. In such case the contractor should be obliged to replace the

defective material without being entitled to any extra payment whatsoever or to any extension of

time of completion of contract.

24-2 Penalty and Rejection for Decreased Efficiency

The contractor should keep the No load losses and load losses and to be within the guaranteed values,

should the loss values, measured from the works tests, exceed the allowable tolerances in the IEC

or approved equal standards, then the customer representative should have the right to reject the

transformer with such losses.

However, the measured losses deviate from the guaranteed figures, but lie within the allowable

tolerances (10 % total losses), then the excess losses should be evaluated as per the following

formula and the contractor should be penalized accordingly.

P. W = K x 8760 x C [dwi+ (LS.F) (P2) dwcu] LE

Where

K = Present worth factor (L.E)

K = ((1+i)N -1) / i (i+1)

N )

i: latest interest rate from Central Bank of Egypt.

N: number of years. (20 years)

C = Cost of KWH. (According to the max commercial cost of KWH and can be adjusted as

EEHC update)

LS.F = Loss factor for the load = 0.4.

Wi = Iron losses in KW at rated voltage and main tapping

Wload = Load losses in KW at full load and 95ºC.

P = Peak load (P.U.) = 0.8.




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No credit should be given for any decrease in the value of loss(es) below the guaranteed.

24-3 Replacement of Rejected Material and Equipment

If according to the above articles, any material or equipment is rejected, the contractor should be

obliged to replace it without extra payment.

25. Transformer testing

Customer representative has the right to send its representative to attend any or all of these tests.

Testing dates should be advised by the contractor to permit witnessing by Customer representative

(s). test certificates should be sent to customer representative.

A. Type tests:

These tests should be carried out on one transformer for each type in accordance with the

requirements of IEC standards for transformers, these should include the following:

1- Full wave lightning impulse voltage withstand test. IEC 60076

2- Temperature rise test. IEC 60076

3- Noise level measurement IEC 60551

4- Radio influence voltage measurement IEC 60437

5- Winding insulation requirement ASTM-D-202

6- Tests on bushings IEC 60507

B. Routine Tests:

These tests should be applied on each transformer in accordance with the requirements of IEC

standards for transformers, these should include the following routine tests:

1- Measurement of d.c. winding resistance. (the allowable deviation in the dc resistance value

between phases should be less than 5% at high voltage side and should be less than 10% at

low voltage side)

2- Turns ratio and polarity check or vector-group symbol at all tap positions. Bushing positions

must have permanent markings at this stage of production.

3- Measurement of impedance voltage

4- Measurement of load losses.




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5- Measurement of No-load losses.

6- Induced over voltage withstand test.

7- Separate – source power frequency voltage withstand test.

8- Electrical oil tests.

9- Insulation tests between windings and earth and between winding each other (absorption

factor (R60/R15 > 1.3)).

R60: insulation resistance at 60 second.

R15: insulation resistance at 15 second.

C. Special Tests:

Special tests should be made in accordance with the requirements of IEC and EN standards for types

of transformers those have not yet supplied or for transformers those have delivered but their

design is modified, these should include and not limited to the following:

1- Short circuit test

26. Instruction manuals

The bidder should be supply with shipment of the transformer complete installation, operation and

maintenance instruction/manuals suitable for the specific item(s) being supplied, including

information from the manufacturer of each purchased accessory.

It should include interconnected diagrams, drawings and instructions describing procedures for items

that will be shipped to be assembled and interconnected for operation when installed.

These should contain strict instructions as required for carrying, moving by skidding or rolling, and

lifting the transformer and accessories.

The manual should include the instructions for tap changing, enclosure assembly, disassembly,

temperature indicator reading, setting procedures and other information designed to assist in proper

operation and periodic maintenance of the equipment being supplied.

Key interlocking should be identified, and serial number should be supplied.

All manuals, instructions and supporting drawings and parts lists supplied by the manufacturer and

supplemental instruction and data supplied by accessory manufacturers should be in English,

clearly readable and arranged in such format to make the subject items easily identifiable.




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27. Drawings

Bidder should supply a complete set of “as manufactured” drawings and wiring diagrams

including interconnection diagrams of all components and assemblies of the equipment which

assist in operation and maintenance of the equipment.

All drawings should be compatible with current industrial standards and good industrial practice.

All information should be in English language, clearly readable, with IEC standard symbols,

device model, numbers and other requirements.

All Dimensions should be in centimeters.

28. Spare parts (option as per ...EDC requirements)

Tender should contain a list of recommended needed spare parts.

29. Warranty

The manufacturer should warrant the oil distribution transformer to be free from defects in both

material and industry for period of 12 months from the time of operation or 18 months after

delivers to ……EDC

In case of supplying for the first time, the warranty should be 4 years starting from delivery date.




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30. Max. permitted power losses of transformers (at 95ºc)

Noise Level

dB

% Z

(Tolerance

±10%)

load losses (W)

at 95ºC

No load losses

(W)

at 400 V

Power

(KVA)

45 at 1m. 4 650 60 25

45 at 1 m. 4 875 90 50

46 at 1 m. 4 1260 113 63

46 at 1 m. 4 1505 145 100

47 at 1 m. 4 2170 210 160

48 at 1 m. 4 2520 262 200

48 at 1m. 4 3815 403 300

50 at 1 m. 4 4638 430 400

52 at 1m. 4 5460 510 500

52 at 1m. 4 6430 600 630

54 at 1m. 5 7700 650 800

54 at 1m. 5 9450 770 1000

56 at 1m. 5 11700 950 1250

56 at 1m. 6 13860 1140 1500

56 at 1m. 6 14900 1200 1600

52 at 3m. 6 15750 1450 2000

53 at 3m. 6 16300 1750 2500

54 at 3m. 7 19750 2100 3000

55 at 3m. 7 22850 2450 3500

56 at 3m. 7 25950 2800 4000

57 at 3m. 7 31500 3500 5000

N.B.

It is necessary to add a valve with a tap to each transformer to get an oil specimen for testing.

31. Guarantee table

The attached guarantee table should be duly completed, signed & submitted with the offer.




Date: 22-12-2020

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GUARANTEE TABLE DISTRIBUTION TRANSFORMER

22 / 0.4 KV

1- Manufacturer

2- Type

3- Standard specification

4- Rated output at 45ºC ambient (KVA)

5- Method of cooling

6- Oil type

7- System of connection

8- Material of insulation

HV winding ـ

LV winding ـ

Major insulation ـ

9- Material of core and its cross-section area (mm²)

10- Max. core flux density at full load (tesla)

11- Turns ratio

12- No load losses (watts)

13- load losses at full load current and 95ºC winding temperature (watts)

14- Resistance per phase at 95ºC For primary (ohms)

For secondary (ohms)

15- Cross-sectional area of cu windings For primary (mm²)

For secondary (mm²)

16- Permissible symmetrical S.C current at L.V side terminals for 3 sec (KA)

17- Primary voltage at normal tapping (volts)

18- Permissible overload duration without change of specified temp. rise

according to IEC 60076-7

yes [ ]

no [ ]

19- Full load current at LV side (Amps)

Full load current at HV side (Amps) ـ

No load current at LV side (Amps) ـ




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20- Impedance voltage ( % )

21- Temperature rise at rated output above 45°C ambient temperature

A- At oil top level (°C)

B- Winding temperature (°C)

C- Core temperature (°C)

22- Tapping switch (on H.V. Side)

No. of steps ـ

( % ) Value of the step ـ

23- Medium voltage insulators

Length of leakage (mm) ـ

Arc gap (mm) ـ

24- Means for firmly bracing of trans.Winding to avoid loosening them due to S.C

25- Transformers should be complete with all accessories in tendered specifications yes [ ]

no [ ]

26- Transformers should be manufactured according to standards mentioned in

tendered spec. and will satisfy all requirements in tender specifications

yes [ ]

no [ ]

27- Tender specifications are attached with our offer and each page is signed

by us

yes [ ]

no [ ]

28- Overall dimensions (Length x Width x Height) ( mm x mm x mm)

29- Total weight of trans. With oil (kgm)

Weight of oil (kgm)

30- Noise level (db.)

31- Color of silica gel

N / B:

1- No offers should be considered unless attached with both above guarantee table dully

completed and signed for each size of trans. and also our tendered specifications with

all pages signed by tenderer.

2- Tenderer should sign “√” in front of yes or no in the above guarantee table.

I/we guarantee the correctness of above data for transformers we are offering to Customer

Company for Distributing Electricity.

Signature of tenderer: …………….. Date: / /

technical specification for oil-immersed distribution ... 08-… · 5 vector group 4 6 rated power...

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