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Total No of Pages: 8

Technical & General Specifications

1.Introdiction:

1.1 Nuclear Fuel Complex(NFC) has requirement of one no of 1600kVA, 11kV /0.433kV, oil immersed distribution transformers. NFC would like to invite offers from qualified suppliers having a strong R&D and state-of-the art production facilities with adequate experience in supplying distribution transformers in India or comparable emerging countries.

1.2 It is not the intent to specify completely herein all the details of the design and construction of material. However the product shall conform in all respects to high standards of engineering, design and workmanship and shall be performing in continuous commercial operations in manner acceptable to the purchaser. The offered material shall be complete with all components necessary for their intended purpose. The offered material shall be complete with all components necessary for their intended purpose. The design and components shall be deemed to be within the scope of vendor's supply irrespective of whether those are specially brought in this specification and/or commercial order or not.

2. Code & Standards: 2.1 All the equipments and material shall be designed, manufactured and tested in accordance with

the latest applicable Indian standards IS 2026 & IS 1180(Part-I)-2014, IEC standard and CBIP manuals.

2.2 The transformer offered shall in general comply with the latest issues including amendments of

the following Indian standards but not to restricted to it.

Title IS code IEC standard

Outdoor type oil immersed Distribution Transformers upto and including 2500kVA, 33kV-specifiactions

IS 1180(Part-1):2014

Distribution Transformer Method of Construction

IS:2026 IEC: 60076 IEC: 60616

Thermal evaluation & Classification of electrical insulation

IS:1271 ....

Fittings and accessories for Distribution Transformer

IS: 3639 ....

Bushing for alternating voltage IS: 2029 ....

Dimension of porcelain transformer bushing IS: 2029/3347 ....

New insulating oil for transformer & switchgear

IS: 335 ....

Guide for loading of oil immersed transformer

IS:6600 ....

Current Transformers IS:2705 ....

Gas operated relays IS: 3637 ....

Application Guide for CTs IS:4201 ....

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3. Site Conditions:

3.1 Maximum ambient temp 550C

3.2 Minimum ambient temp 50C

3.3 Design ambient temp 450C

3.4 Altitude/RH 1000m above MSL / 100% RH

3.5 Derating The Transformer shall be suitably derated for satisfactory operation for specified altitude, ambient temperature, relative humidity, voltage and frequency variations, derating for special requirements stated above.

4.Electrical & General Data:

4.1 Primary Voltage/ System: 11kV +/-10%, Three wire system

4.2 Secondary Voltage 433V +/-10%, Four wire system, Solidly grounded system

4.3 Rated kVA 1600KVA

4.4 Phases Three(3)

4.5 Frequency 50HZ +/- 5%

4.6 No of windings Two

4.7 % Impedance 6.25

4.8 Vector Group Dyn11

4.9 Operation Duty Continuous

4.10 Type of Cooling ONAN

4.11 Location Outdoor

4.12 Tap Changer Off-load tapping shall be provided on HT side with +5% to -10% variation in steps of 2.5% . All tapping's are full power tappings. The terminal markings ,tappings and connections shall be in accordance with IS:2026( Part IV)

4.12.1 Number of tap positions 7

Application guide for Power Transformer IS:10561 ....

Testing of Transformer oil IS: 1866 ....

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4.13 Typical temperature rise values

4.13.1 a) Winding temperature 450C( Measured by resistance method)

4.13.2 b) Top oil temperature 400C (Measured by thermometer)

4.14 Hot spot temperature As per IS 6600

4.15 Earth fault CT Cast resin type to be provided on the neutral terminal-burden minimum 15VA and protection class 5P10

4.16 No load current As per IS1180(Part-1):2014

4.17 Losses and Efficiency As per IS 1180(Part-1):2014 and Energy Efficiency level is 1.

4.18 Voltage regulation The regulation at 750C at full load and 0.8 power factor subject to the usual tolerance as per IS:2026

4.19 Over load requirements As per IS 2026

4.20 Fitting and accessories for transformer

All valves shall have cast steel body with gunmetal moving parts

4.21 HV side terminal arrangement

Suitable for Bus duct

4.22 LV side terminal arrangement

Suitable for Bus duct

5. Constructional Details

5.1 Core

5.1.1 Material Shock resistant and robust construction made of high quality, low loss, non-aging, CRGO silicon steel insulated laminations securely clamped to provide a vibration and noise free performance and it shall be as per IS 3024.

5.1.2 Cooling ducts To be provided judiciously anticipating max. hot spot temperature in the core

5.1.3 Lifting eyes To be provided

5.1.4 Core earthing Core assembly to be electrically connected to the transformer tank.

5.2 Winding

5.2.1 Material 99.9% pure, electrolytic copper as per IS 1180(Part-I):2014

5.2.2 Insulation Class A

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5.2.3 Type of Insulation Full voltage insulation to be provided; graded insulation not acceptable. Uniform distribution of dielectric stress is to be ensured.

5.2.4 Basic insulation level As per IS 2026

5.3 Tank

5.3.1 Material Low carbon steel plate - welding seams stress relieved

5.3.2 Tank walls Reinforced with adequate stiffeners

5.3.3 Tank cover Bolted to flanged rims of the body through hot-oil resistant, weather proof gasket arrangement.

5.3.4 Accessories Lifting, Jacking and Pulling lugs of adequate capacity of haulage of complete unit with oil filling shall be provided

5.3.5 Conservator Conservator shall be designed such that under conditions of lowest oil level, the bushings remain under the head of liquid. Conservator volume shall be sufficient to maintain oil seal from ambient temperature to oil temperature of 90 deg.C.

5.3.6 Pressure withstanding capacity

As per IS 1180 (Part-1):2014

5.4 Insulating Oil To include sufficient quantity for the first filling of the transformer, circulating equipment and chamber housing the tap changing equipment. In addition 10% additional oil to be supplied in non returnable drums.

5.5 Tap changer The tap changer contacts shall be silver plated and adequately rated for repeated operation and to withstand short circuit forces and shall have strong contact pressure to avoid pitting of contacts.

5.5.1 Off circuit tap changing switch

5.5.1.1 Operating handle The switch shall be linked to an external operating handle through oil-tight gland in the tank side

5.5.1.2 Register Plate A clearly marked register plate shall be provided for easy identification of the current position of the switch

5.5.1.3 Padlocking Facility for padlocking shall be provided.

5.6 Cooling

5.6.1 Type Tank mounted detachable type radiators with suitable valves at the top and bottom for removing the radiator without complete draining of the oil from the transformer tank.

5.6.2 Radiators/Cooling tubes

Low carbon steel with clean, bright internal surface with good support arrangement to withstand mechanical shock.

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5.6.3 Pressure withstanding capacity

Same pressure withstand capacity as that of the main tank

5.7 Marshalling box Quantity as required

5.7.1 Design Weather proof and dust proof with enclosure protection IP 55 to accommodate all the auxiliary electrical devices such as relays, starters, switches, indication and local control equipment required for tap changing system, temperature measuring system etc. Canopy to protect against rains to be additionally provided.

5.7.2 Doors Hinged and padlocked type with suitable glazed openings to view the temperature indicators etc., which are mounted inside.

5.7.3 Accessories Internal lighting, space heater with thermostat control etc., with their controls on the outside of the box.

5.7.4 Wiring within the marshalling box

To be provided through single core heavy duty PVC wires with copper conductor of size not less than 1.5 sqmm.. Terminal blocks shall be screw type terminals and shall have 20% spare capacity. CT wiring shall be done with core size not less than 2.5 sqmm copper.

5.8 Terminal arrangement

5.8.1 Design features Terminals and fittings shall be rated to carry full rated transformer currents on a continuous basis

Housing for bushing current transformers with accessible CT terminals and weather proof TB

Bushing insulators shall be manufactured by the wet process, single piece glazed porcelain and high puncture strength; creep age distances for outdoor type insulators shall be 31 mm per kV of the highest system voltage and shall remain unaffected by atmospheric conditions due to contamination by fumes, acids, dust or rapid change of temperature likely to be met at site.

Neutral bushing shall be provided for earthing of neutral at LV side

Provision of approved resilient material to be interposed between porcelain and metal interfaces to be ensured

5.9 Gaskets Gaskets shall be made of Synthetic rubber or Synthetic rubberized cork resistant to hot transformer oil and shall be conform to Type III as per IS 11149/ Type C as per IS 4253 (Part2).

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5.10 Painting Inside of tank shall be painted with varnish or oil resistant paint. For external surfaces one coat of thermo setting powder paint or one coat of epoxy primer followed by two coats of polyurethane base paint shall be painted . Paint thickness shall be as per Table 12 of IS 1180(Part-I)-2014. Color Dark Grey shade 632 of IS-5

6. Transformer fittings:

6.1 Transformer Fittings Inspection Covers (HT & LT side)

Rating, Diagram and Tap connection Plates

Valve Schedule plate

Terminal Marking Plate

Two earthing terminals

Lifting lugs, Jacking Pads and haulage lugs

Dehydrating silica gel breather with oil seal at about 1400 mm from rail level

Magnetic type oil level indicator with "low oil level" signaling contact on conservator and having maximum, minimum and normal filling level marks

Thermometer pocket (for additional thermometer)

Bulb type thermometer

Conservator with oil filing hole, cap and drain valve with plug

Air release devices

Buchholz relay with testing and sampling cocks, alarm and trip contacts and shut off valves on either side of the relay for transformer and having provision for collecting gas by means of bleeder pipe at about 1,250 mm from rail level.

Oil temperature indicator with maximum temperature reading pointer and alarm and trip contacts. The required arrangements shall be provided for remote monitoring of oil temperature value.

Winding temperature indicator with maximum temperature reading pointer and requisite sets of signaling contacts for alarming and tripping operation. The required arrangements shall be provided for remote monitoring of winding temperature value.

Drain valves with cover plates

Oil sampling valves

Filter valves with plugs

Pressure relief device with alarm and trip contacts

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7. Tests:

7.1 Routine tests: As per IS:2026 and IS 1180(Part-I):2014.

7.2 Type tests: Temperature rise test on each transformer.

7.4 Site Tests: Magnetic Balance, IR measurement Test , Voltage Ratio test.

Note: Contractor shall include cost of the above tests while quoting.

8. The following documents shall be submitted for Department approval before manufacturing of

Transformers .

a). G.A drawings of transformers having the information like dimension of transformer & all

accessories .

b). Flux density calculation sheet.

c) . Details of CRGO make, Grade and Thickness of each lamination.

e). No load losses calculation sheet.

f). Conductor details for each winding with cross section area.

g) . I2R losses calculation Sheet.

h). Load losses calculation Sheet.

i). Winding internal sketch & layout.

j). Core weight & Copper weight calculations.

k). CRGO Watt/Kg Curve.

9. Safety Features:

9.1: Earthing: Transformer body shall be provided with two separate earthing terminals for earthling

in compliance with latest I.E. rules.

Undercarriage with flat bi-directional wheels with locking and bolting devices.

Marshaling box complete with all instruments, accessories and fittings as required for the transformer. Proper rain hoods shall be provided over the marshalling box.

Danger boards

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9.2 Pressure Relief Valve with alarm and trip contacts.

10. Inspection:

10.1 Four weeks advance notice shall be given to witness the final routine test and Type test as per

IS:2026.These tests shall be performed on the complete assembly at manufacturer's works. Test

certificate duly signed by owner's representative shall be issued as part of final document.

10.2 In respect of raw material such as core stampings, winding conductors, insulating paper, Fittings

and oil, you shall use these materials manufactured/supplied by standard manufacturers and

furnish the manufacture's test certificate as well as the proof purchase from these manufacturers

for information of the company at the time of inspection.

10.3 To ascertain the quality of the transformer oil the original manufacturer's test report should be

submitted at the time of inspection.

10.4 If the transformer fails to meet the requirement at routine and type test and specifications at the

time of inspection , the quantity of transformer ordered will be forthwith rejected.

10.5 After sending the transformer to our store , if any of the technical particulars are seen to be at

variance than the guaranteed particulars , the transformer will be rejected .

10.6 If the transformer fails to meet the requirement at site tests , the quantity of transformer

ordered will be forthwith rejected.

11. Transportation and Delivery of all the type and routine tested transformers to the site shall be in

the scope of bidder only.

11.Guarantee For the Transformers:

Guarantee period shall be 12 months from the date of commissioning or 18 months from the

date of supply whichever is earlier . If any transformer fails during this guarantee period, the

supplier shall repair the same at his coat at his works.

12. Guaranteed Technical Particulars (Attached as Annexure-I) of transformers shall be

submitted along with offer.

13. The rates shall be inclusive of all taxes , duties as applicable, charges towards routine, type,

special & site tests and charges towards transportation of transformer .