11kv 33kv 200kVA Pole Mounted Distribution Three Phase Transformers

• Customization: Available
• Application: Power, Instrument
• Phase: Three
• Model NO.: S11
• Core: Amorphous Alloy Transformer
• Cooling Method: Oil-immersed Type Transformer
• Winding Type: Two-winding Transformer
• Certification: ISO9001
• Usage: Single-phase Transformer, Power Transformer, Distribution Transformer
• Frequency Characteristics: Power Frequency
• Shape of Core: Ring
• Brand: Oei
• Transport Package: Wooden Box
• Origin: Suizhou
• HS Code: 85043190
• Production Capacity: 3000
• Package Size: 180.00cm * 180.00cm * 180.00cm
• Package Gross Weight: 200.000kg

Product Description

TECHNICAL SPECIFICATION
POLE MOUNTED DISTRIBUTION TRANSFORMERS
 

1. INTRODUCTION

This specification provides for the design, manufacture, testing in factory, supply, delivery and off-loading on site for Pole Mounted Distribution Transformers.

It shall be the responsibility of the Contractor to furnish equipment, which shall meet in all respects the performance specification and will have satisfactory durability for the prevailing site conditions.

The Contractor shall furnish all material and labour not herein specifically mentioned or included, but which may be necessary to complete any part of the work or work as whole, in compliance with the requirements of this specification.

The detailed design arrangement of the equipment shall be the responsibility of the Contractor subject to the approval of the Engineer. The design and workmanship shall be in accordance with the best engineering practices to ensure satisfactory performance throughout the service life.

The Pole Mounted Distribution Transformers supplied shall also fully comply with the General Service and System Conditions

 

1. 1. Standards and Codes

Except where modified, all equipment and materials shall be in full accordance with IEC (International Electrotechnical Commission) and ISO (International Standards Organisation) standards and recommendations. If relevant IEC or ISO standards and recommendations are not available in any case or cases then relevant British Standards or National Standards shall apply if available.

When IEC, ISO, BSI or National Standards are referred  to  the  edition  used  shall  be  that current at the date of Tender, together with any amendment issued to that date.

Further to that above additional standards order of preference is listed below: IEC International Electrotechnical Commission
ISO International Standards Organisation BSI British Standards
NS National Standards (where available) ANSI American National Standards Institute

Where the use of a standard other than IEC, ISO or BSI is agreed then this standard shall be used, where applicable. Where other standards are proposed in place of IEC, ISO or BSI Standards, confirmation shall be provided that the provisions of the standards are equivalent to or exceed those of the equivalent IEC, ISO or BSI standards.
Copies of any standards proposed in substitution for  IEC,  ISO  or BSI standards  must be submitted with  the Tender accompanied where necessary by English translations of the appropriate sections.

 

Notwithstanding any descriptions, drawings or illustrations which may have been submitted with the Tender, all details other than those shown in the 'Deviation from the Technical Specification Schedule' and approved by the Engineer shall be deemed to be in accordance with the Specification and the standard specifications and codes referred to therein.

No departures from the specification except those shown in the 'Deviation from the Technical Specification Schedule' and approved by the Engineer are to be made without the written approval of the Engineer.

The Pole Mounted Distribution Transformers shall comply with the latest editions of and amendments to, the standards/specifications listed below:
 

S.No.	STANDARD	TITLE
1.	IEC 60137	Insulated bushings for AC Voltages above 1 kV
2.	IEC 60076-1	Power Transformers - General
3.	IEC 60076-2	Temperature rise
4.	IEC 60076 - 3	Insulation levels, dielectric tests and external clearances in air
5.	IEC 60076 -5	Ability to withstand short
6.	IEC 60076 - 7	Loading guide for oil immersed transformers
7.	IEC 60296	Specification for unused mineral insulating oils for transformers and switchgear
8.	IEC 60076 - 10	Determination of transformer and reactor sound levels
9.	IEC 60437	Radio Interference Test on High Voltage Insulators
10.	IEC 296-1969, IEC 76	Specification for power transformers
11.	IEC 296-1969	Bushing for alternating voltage above 1000V
12.	DIN 42531 to 33	Specification for Outdoor Bushings.
13.	ASTM D-1275	Specification for fittings and accessories for power transformers
14.	IEC 76	Guide for loading of oil immersed Transformers
15.	BS 159:1957 BS 3288 (Part-1):1960	Electrical power connector
16.	IEC 554	Specification for Insulating Kraft Paper
17.	IEC 641	Specification for Insulating Press Board
18.	ASTM B-233	Specification for Al Wire rods
19.	ASTM D-1275	Manual on Transformer
20.	ASTM D-202	Testing of Insulation Papers
21.	ISO 2063	Metallic Coatings - Protection of Iron and Steel against Corrosion

1. PRODUCT

 

1. 1. Design

 

1. 1. 1. Types of transformers

The transformers shall be three phase or single phase units of the sealed tank type with oil immersed copper windings and shall be naturally cooled (ONAN). They shall be suitable for operation in outdoor exposed locations.

1. 1. 1. Performance characteristics

 

1. Rating
   1. The following ratings are covered by this Specification: THREE PHASE:

33/0.400/0.230kV - 25kVA, 50 kVA, 100 kVA and 200 kVA

SINGLE PHASE: The single phase transformers shall be connected on the primary side between two phases of 3-phase lines

33kV/230 V-0-230 V - 10 kVA, 15 kVA, 25 kVA and 50 kVA
 

1. 1. Transformer rated kVA shall be calculated on the following assumptions:

 

1. 1. 1. Constant flux regulation
      2. Continuous steady load
      3. Continuous ambient temperature of 30°C.
      4. 55 K average winding temperature rise and 50 K top oil temperature rise.
      5. Maximum winding Hot Spot temperature rise of 68 K.

 

1. 1. After thermal equilibrium has been reached at 75% of rated load the transformer shall be capable of sustaining the overload conditions listed in Table 1 without the transformer winding hot spot temperature exceeding 140°C.

TABLE 1

Load	Minimum Duration in Minutes
Percentage of Rating	Ambient Temperature 30°C	Ambient Temperature 40°C
133	240	115
150	98	65

The Supplier shall include calculations demonstrating that these requirements are met. These calculations shall disregard the effect of winding thermal capacity.
 

1. Voltage ratio and tapping range

 

1. The voltage ratio shall be

 

THREE PHASE: 33000/400/230 V SINGLE PHASE: 33000/230-0-230 V

1. For all transformers, a 5-position externally  operated  tap  changer  shall  be provided on the MV winding

 

1. Tapping shall be for a no-load, primary voltage variation of +/-2.5% and

+/-5%
 

1. Impedance

The guaranteed value of percentage impedance measured at 75°C and tap no. 3 (subject to tolerance specified in IEC 60076) shall not exceed

• 4.5% for units above 50kVA
• 4.25% for units up to 50kVA

 

1. Short Circuit Ratings

 

1. System short - circuit levels:
   • 33kV system 1800 MVA

When calculations of winding mechanical stress are offered in place of a test, they shall be in accordance with latest CIGRE guidelines (e.g. Publication 209) and show appropriate safety margins.
 

1. Duration of short circuit shall be 2 seconds

 

1. Initial average winding temperature shall be 105oC
2. Final average winding temperature shall be:

 

1. • 250oC. for copper conductors
   • 200oC for aluminium conductors
2. Winding Connections

 

• The three phase transformer shall be connected delta-star, in accordance with vector group reference

Dyn11 of IEC 60076.
 

• The single phase transformers shall be connected on the Primary side between two phases of the 3-phase line

The LV neutral shall be brought out and fully rated in all cases.

 

1. Losses

The maximum losses at rated voltage and rated frequency permitted at 75 °C. for the transformers are indicated below

Three phase transformers Table 2

 

Voltage Ratio	kVA Rating	Maximum No-Load Losses in Watts	Maximum Load Losses in Watts
33kV/400/230V	25	85	1210
	50	160	1440
	100	310	1900
	200	540	2810

Single phase transformers Table 3
 

Voltage Ratio	kVA Rating	Maximum No-Load Losses in Watts	Maximum Load Losses in Watts
33kV/250V-0-250V	10	25	614
	15	40	652
	25	52	780
	50	100	1008

The above losses are maximum allowable and there would not be any positive tolerance. Bids with higher losses than the above specified values would be treated as Non-responsive.
The losses shall be measured during the routine tests. if it is found that the actual measured losses are more than the values quoted by the bidder, the purchaser shall reject the transformer and he shall also have the right to reject the complete lot.
In the event of either the no-load or load loss exceeding its guaranteed values as stated by the contractor in his bid and it is detected upon receipt of the transformers, the contractor shall make such changes, modifications and/or additions to the transformer or any part thereof that are necessary to attain the Functional Guarantees at its cost and expense, and shall request the Employer to repeat the Guarantee Test for any transformer that has losses higher than those specified above
 

1. Flux Density

The flux density at any point of the magnetic circuit when the transformer is connected on tap 3 and operating at normal voltage and frequency shall be stated and shall not exceed 1.65 Tesla.
Over flux in the transformer core shall be limited to 12.5% to ensure that in the event of over-voltage to the extent of 12.5%, the core does not get saturated. The maximum flux density in any part of the core under such condition shall not exceed 1.9 Tesla.
 

1. Insulation

 

Bushings and terminals shall be adequate for the winding tests and shall flash over externally before puncture or internal failure.
Insulation levels are defined in IEC 60076 and shall be as follows:
 

	WINDING
	33kV	LV
Basic Impulse Level, kV	170	-
Power Frequency, kV	70	3

 

1. Noise

The average noise level of the transformers shall not exceed 48 dB when tested as per IEC 60076-10
 

1. Radio influence voltage

The maximum Radio Influence Voltage shall be 250 micro volts, measured as specified in IEC 60437.



 

1. 1. 1. Tap change methods

 

1. Tap changing shall be carried out by means of an externally operated self-position switch and when the transformer is in de-energised condition. Switch position No.1 shall correspond to the maximum plus tapping. Each tap changes hall result in variation of 2.5% in voltage.
2. Provision shall be made for locking of the tap switch handle by using a padlock with 6 mm diameter  hasp to be furnished by Purchaser.
3. Tap change switches shall be fitted with gasketed covers, so that sealing of the transformer under normal conditions is independent of the switch shaft gland.

 

1. 1. 1. Bushings and Terminals

 

1. Bushings

The HV & LV bushings shall be as per the latest version of IEC 60137. The bushings shall be fixed to  the transformers on side with straight pockets and in the same plane or the top cover for transformers above 100 kVA. For transformers of 100 kVA and below the bushing can be mounted on pipes. The tests as per latest version of IEC 60137 shall be conducted on the transformer bushings.

MV and LV Bushings shall be:
 

1. 1. Easily replaceable. Cemented bushings are not acceptable.
   2. Sufficiently robust to withstand normal transport hazards.
   3. Fitted with heavily tinned plated terminals and galvanized hardware to take tin plated aluminium compression lugs.

 

 

1. Creepage distance

The standard specific creepage distance shall be IEC class IV, very heavy pollution/costal areas; 31 mm/kV.

1. Arcing Horns

Adjustable spark-gaps shall be provided on the MV bushings, with gap adjustment as follows:
- 33 kV - 130 to 210 mm
 

1. Bushing labels

The MV bushings shall be labeled A, B, C and the LV bushing a, b, c, n. The labelling of the phases shall be by permanent raised lettering on the transformer tank or cover. Phase identification by adhesive stickers is not acceptable.
 

1. 1. 1. 1. Connections

 

• • • • • Solid aluminum cables up to 185 mm2 or stranded conductors up to 70 mm2 Cu or 265 mm2. Al will be used for connecting to the LV side of the transformers.
        • For connecting to the MV terminals of the transformers 16 mm2 to 70 mm2 Cu or 25 mm2 to 120 mm2  Al stranded conductors will be used.
        • All connections shall be prepared to prevent electrolytic action between the connection components.

 

1. 1. 1. Grounding terminals

All transformers shall be provided with a grounding terminal with a 10 mm diameter hole. The material shall be galvanized steel.

1. 1. 1. Tank fabrication

 

• • • • Transformer tanks shall not leak. The criterion of leakage shall be discoloration by oil of white wash applied externally to the suspected parts at an oil temperature of 90°C or other method approved by the Purchaser.
      • The internal clearance of tank shall be such that it shall facilitate easy lifting of core with coils from the tank without dismantling LV bushings & all joints of tank and fittings shall be oil tight and no bulging should occur during service.
      • The tank plate and the lifting lugs shall be of such strength that the complete transformer filled with oil may be lifted by means of lifting shackle.
      • The minimum thickness of steel used shall be 3mm.
      • The tank shall be of hermitically sealed construction. Top cover shall be bolted type and fitted with neoprene bonded cork gasket suitable for temperatures as specified in this specification.
      • The tank shall be of rigid construction.
        • The internal pressure shall be one atmosphere at an internal temperature of 10°C.

 

• • • • • The tank shall be  designed for an  internal  pressure of100  kNm-2  at 40°C  ambient conditions.  It shall be capable of withstanding an unlimited number of 24 hours cyclic variations of internal pressure from atmospheric to this value. The Supplier shall include evidence demonstrating compliance with this requirement.
        • The Supplier shall state the  top oil temperature  at  which the  tank internal pressure is 100kNm-  2 and the value of steady load which will result in this top oil temperature at an ambient of 40°C .

 

• • • • The maximum transformer dimension in width should not exceed 1200mm. The transformers will normally be mounted on single pole structures.
      • A standard mounting bore plate on which to mount the transformers shall be supplied with the transformer. Detailed drawings of these bore plates shall be sent to the Purchaser for approval.

 

1. 1. 1. Finish of tank
2. The transformer tank and its accessories shall be adequately protected against corrosion and the bidder shall include a statement of the method of protection proposed.
3. Hot dip galvanizing is preferred, where  this  is  not  practicable  the  tanks  shall  be shot-blasted  and then immediately zinc sprayed to an average weight deposit of not less than 550gm/m2 followed by a zinc chromate based primary paint, and two coats of durable oil and weather resisting paint. Finish colour shall be Admiralty Grey.
4. The inside of tanks along with other M.S. fittings shall be cleaned, scrapped and suitably shall be coated with oil resisting varnish or antioxidant paint of high quality i.e. Zinc Chromate capable of withstanding 120°C temperature, so that the oil cannot come into contact with the tank metal at any time. The MS fittings may preferably be electro-galvanized.

 

1. 1. 1. Core

 

1. The cores shall be constructed from high grade cold rolled non-aging grain oriented silicon steel laminations. The design of the magnetic circuit shall be such as to avoid static discharges, development of short-circuit paths within itself or to the earthed clamping structure and the production of flux components at right angles to the plane of laminations which may cause local heating. The core laminations shall be held rigidly by a steel framework which shall clamp them together to prevent any vibration. The core shall be provided with lifting lugs suitable for lifting the complete core and coil assembly of the transformer without transmitting the stresses to the laminations.
2. The transformer shall be suitable for over fluxing due to combined effect of system voltage and frequency upto 12.5% without injurious heating. These laminations shall be as thin as possible consistent with mechanically strong constructions. At least one side of each lamination shall be coated with a hot oil proof insulating material. In case the manufacturer's standard method is different from this, it should be clearly described. The laminations should be free from rust and colour spots. The laminations shall be grade M4 or better grade.
3. For the bolts used for clamping, the core shall be so insulated that there is no possibility of contact between edges and the core bolts. The bolts shall be tested at 2500 volts to earth. The core shall be securely fastened to tanks with minimum 4 fixing bolts so as to prevent any possibility of movement in transit.

 

1. 1. 1. Windings

 

1. The conductor used for winding shall consist of high conductivity, non-oxidising solid drawn EC Grade copper. The primary winding shall be connected in delta and the secondary winding in star (Vector symbol Dyn-11), so as to produce a positive displacement of 30° from the primary to the secondary vector of the same phase. The neutral of secondary winding shall be brought out to a separate insulated terminal. The winding shall be designed to reduce to a minimum the out-of- balance forces in the transformer at all voltage ratios.
2. The coils shall be circular in shape and their construction shall be such that there is no possibility of distortion under any likely conditions of service. The high and low voltage windings shall be concentric, with the low-tension windings nearest the transformers core and high tension windings outside. The two windings shall be so placed that they remain electro magnetically balanced under all conditions of service. The axial lengths of the coils must be kept down to a minimum so as to strengthen the winding against axial stresses under short circuit conditions.
3. In oil immersed winding, an adequate provision shall be made for the circulation of oil, so that a  very low temperature gradient between copper and oil is assured and any danger of excessive local heating is eliminated.
4. All HV & LV coils ends shall be provided with crimped lugs. The star point on the LV side shall preferably be properly sleeved and crimped.  However, the manufacturer may make  the star point  by fixing a neutral bus bar of copper with the help of bolts, nuts and spring washers etc. All fixations/joint should be such that there is no scope for loose contacts, local heating, breakage of conductor, loosening due to vibrations etc.
5. Copper strip/foil used for earthing the core should be tinned. The tinned foil should be properly connected to the channel with bolts and nuts after removing the paint from the channel underneath the copper foil.
6. All transformers shall be designed and constructed to withstand without damage, thermal & dynamic effects of an external short circuit. The manufacturer/ supplier shall furnish the relevant design data and calculations in support of having fulfilled this requirement as stipulated in IEC 60076-1.
7. LV winding shall be such that neutral formation will be at top and the winding construction of single HV coil wound over LV coil is preferable.
8. Current density for HV and LV winding should not be more than 2.8 Ampere per sq mm for copper Conductor.
9. Joints in the winding shall be avoided. However, if jointing is necessary the joints shall be properly brazed and the resistance of the joints shall be less than that of parent conductor.
10. The core/coil assembly shall be securely held in position to avoid any movement under short circuit condition.

 

1. 1. 1. Winding Insulation

Thermally stabilized paper or convention class 'A' paper shall be used.
Double paper covering shall be used for winding insulation both for HV & LV windings. Electrical Grade epoxy insulation paper shall be used for interlayer insulation of the HV & LV coils. Corrugated

 

cylinders made of pre-compressed board shall be provided between HV & LV windings. Angle shaped end rings made from pre-compressed board shall be used between end coils and the core.
Percentage retention of bursting strength when tested as per ASTM D202 in oil at 150oC shall be as follows:

Table 4

Days in oil	Minimum percentage retention of bursting strength of original value
10	90
30	75
50	60
180	32

 

1. 1. 1. Transformer oil

 

1. The Transformer shall be supplied with initial filling of Class 1 transformer oil conforming to IEC 60296.
2. The oil shall have high electrical strength, good impulse strength and good arc quenching properties. It shall be clear, bright but non-toxic. It shall be free from objectionable quantities of elemental and thermally unstable sulphur bearing compounds. If present, these compounds shall not cause corrosion of certain metals used in transformer. There should be no significant quantity of furanic compounds detected in new oil. The oil shall have ability to resist transient voltage stresses caused by lightning strokes and high voltage switching surges.
3. Good oxidation stability is principal requirement for longer service life of oil. It shall not contain detectable amounts of polychlorinated biphenyls. Use of recycled oil is not acceptable. The specific resistance of the oil shall not be less than 2.5 X1012 ohm cm at 27°C when tested as per relevant international standard.
4. The transformers oil shall be of low viscosity and shall offer the minimum resistance and maximum convective assistance to the flow. The oil shall be thin enough to penetrate into narrow ducts and assist in the circulation through transformer winding to prevent local over healing. It must have low pour point. The viscosity of oil shall be such that the flow is not significantly impeded.
5. The transformer oil used shall comply with the provisions in the IEC 60296. Oil sample will also be taken out from fresh stock of T/F oil to be tested as per relevant international standard. Oil shall be filtered and tested for break down voltage (BDV) and moisture content before filling in the transformer. The transformer and all associated oil filled equipment shall normally be supplied along with the first filling of oil and 10% excess quantity of oil shall be supplied in non-returnable drums.

 

1. 1. 1. Sealing Gaskets

All sealing washers/ gaskets shall be made of oil and heat resistant nitrile/ neoprene rubber / synthetic rubber bonded cork type RC-70-G Gaskets. Gaskets made of natural rubber or cork sheet are not permissible.
 

1. 1. 1. Tank fittings and attachments

 

1. Transformers shall be provided with the following fittings and attachments.

 

Off-load Tap Changer LV Bushing Arrangement
MV Bushing Arrangement
2 No. Grounding Terminal with lugs Pressure Relief Device
Oil Level Gauge Lifting Lugs
Filling and Draining Valve Rating and Connection Plate
Pole Mounting Supports Cable Clamps
 

1. Pressure Relief Device

The pressure relief device shall have a flow rate of 16.5 litres/sec. at 100 kN/sq  m. Operating pressure shall be 40kN/sq m.
 

1. Oil Gauge

Plain prismatic type oil level gauge with markings shall be provided.
 

1. Lifting Lugs

Lifting lugs shall be designed so that the transformer can be lifted with a single hook without damage.
 

1. Filling and Draining Valves

Valves shall be equipped with non-detachable handles and protecting plugs.
 

1. Each transformer shall be provided with a rating plate of weather proof material showing containing the information specified in IEC 60076-7. The actual iron and load losses of the transformer should also be mentioned on the rating plate. :
   • Name of Client

 

• • Type of Transformers

 

• • Specification to which manufactured -IEC 60076

 

• • Manufacturer's name

 

• • Manufacturer's serial number

 

• • Year of manufacture
    • Number of phases - 3

 

• • • Rated power - kVA

 

• • • Rated frequency - Hz

 

• • • Rated voltages - kV

 

• • • Rated currents - Amps

 

• • • Vector group symbol - Dyn11

 

• • • Impedance voltage at rated current - per cent (measured value)

 

• • • • Type of cooling- ONAN

 

• • • • Continuous ambient temperature- 30°C

 

• • • • Top oil temperature rise at rated load - k

 

• • • • Total weight - kg

 

• • • • Volume of oil- Litre

 

• • • • Weight of core and windings - kg

 

• • • • Name of Purchaser

 

• • • • Table of primary voltages at five tapping positions.

 

• • • • Connection diagram

 

1. Mounting Supports

Pole mounting brackets/platforms shall be fitted to each transformer.

 

1. KVA Labelling

The transformers shall be conspicuously labelled with their respective KVA rating and number of phases. The characters shall not be less than 60mm X 40mm. Adhesive stickers are not acceptable.

 

1. 1. 1. RAW MATERIAL

The raw material used in the manufacture of transformers shall be brand new and of the best quality available  in the market.  The information regarding source of procurement, testing of transformer  oil etc. should be furnished.
 

1. 1. 1. MOUNTING

The under base of the transformer shall be provided with two channels of adequate size at suitable spacing for fixing transformer on Pole.
 

1. 1. 1. GUARANTEE

 

The manufacturers of the transformer shall provide a guarantee of 24 months from the date of receipt at the stores of the Utility or 18 months from the date of commissioning, whichever is later. In case the distribution transformer fails within the guarantee period the Client/Consultant will immediately inform the Contractor who shall take back the failed DT within 15 days from the date of the intimation at his own cost and replace/repair the transformer within forty-five days of date of intimation with a roll over guarantee.
The outage period i.e. period from the date of failure till unit is repaired/replaced shall not be counted for arriving at the guarantee period.
In the event of the supplier's/Contractor inability to adhere to the aforesaid provisions, suitable penal action will be taken against the supplier which may inter alia include blacklisting of the firm for future business with the purchaser for ascertain period.

1. TESTING AND INSPECTION
   1. Routine Tests

Routine tests shall be carried out on all transformers and shall be free of charge. The tests shall be carried out in accordance with IEC 60076 where this is applicable. The following routine tests shall be carried out:

1. Measurement of winding resistance at each tap
2. Voltage ratio measurement and check of polarity or vector group symbol - at all tap positions. Bushing positions shall have permanent markings at this stage of production
3. Measurement of impedance voltages/short circuit impedance.
4. Measurement of load loss at rated current and normal frequency
5. Neutral current test (The value of zero sequence current in the neutral of the star winding shall not be more than 2% of full load current).
6. Measurement of no-load loss and no-load current at rated frequency and 90%, 100% & 112.5% rated voltage.
7. Induced over voltage withstand test - 44kV and 66kV for 60 seconds on 33kV windings respectively.
8. Separate source voltage withstand test on MV and LV windings.

Winding: 33kV LV Voltages: 70kV 3kV
 

1. Leakage Test: The criterion of leakage shall be discoloration by oil of whitewash applied externally to suspected parts at an oil temperature of 90°C or other method approved by the Purchaser

1. Measurement of insulation resistances to earth with calculation of the Polarization Index
2. Measurement of dielectric dissipation factor and capacitances

1. Oil sample test.

 

1. 1. Type tests
      1. The following type tests shall be conducted on the transformers in addition to the routine tests from (a) to (k) as indicated above:
         1. Air Pressure Test: The tank shall be fixed with a dummy cover with all fittings including bushings in position and shall be subjected to the following pressure created inside the tank:
            1. 0.8 Kg /cm2 above the atmospheric pressure for 30 minutes:
            2. A vacuum corresponding to (-) 0.7 Kg/cm2    for 10 minutes.

 

1. 1. 1. 1. Magnetic Balance Test.
         2. Noise-level measurement.
         3. Measurement of zero-phase sequence impedance.
         4. Measurement of Harmonics of no-load current
         5. Unbalanced Current Test: The value of unbalanced current shall not  be  more than 2% of the full load current.
         6. Temperature Rise Test for determining the max. Temp. Rise after continues full load run shall be carried out on one unit from each lot offered for inspection.
         7. Impulse voltage test.

Special test:

1. 1. 1. 1. Short Circuit Test: This test shall be made in accordance with the details specified in IEC 60076-7  and to be conducted in presence of Employer representative from some recognized testing Authorities. The dispatches shall be allowed only after successful conductance of this test, on one t/f.
      2. Permanent deflection of flat plate, after pressure has been released, shall not exceed the value given below:

 

Length of plate	Deflection
Upto 750 mm	5 mm
751 to 1250 mm	6 mm

1. 1. 1. Type tests /Special test will be carried out free of cost. Type test/Special test reports of these tests be submitted along with the tender if already carried out. The Employer  may waive  off  type test/special test if so desires in case the tests on an identical transformer has already been conducted during last 5 years at an Acceptable independent testing Authorities.

Acceptable independent testing Authorities include the following: KEMA - Holland, CESI - Italy, EDF
- France and IREQ, - Quebec, Canada. Approval of type tests certificates supplied by any other authority is subject to the written acceptance of the Employer.
The tests shall be carried out in accordance with the Standard specified in each case. The tests shall include any or all as specified in Table 5 at Purchaser's option.
TABLE 5
 

Type test	Standard
Test of temperature rise	IEC 60076 -2
Lightning Impulse, including Chopped-waves	IEC 60076-3
Noise Level Measurement	IEC 60076-10
Measurement Winding Insulation	ASTM D202 (Clause 12)

 

1. 1. Inspection

The inspection shall be carried out in presence of Employer/Consultant representatives. All tests and inspection shall be made at the place of manufacture unless otherwise specifically agreed upon by the manufacturer and Employer at the time of Employment. The manufacturer shall afford the inspectors representing the Employer all reasonable facilities, without charges, to satisfy that the material is being manufactured in accordance with this specification. All the type and routine tests, reports & certificates shall be submitted and got approved from the Employer before dispatch equipment. The Supplier shall provide the Purchaser of a schedule of manufacture and tests at least two weeks before the events are to occur.

 

1. PACKING

Transformers shall be delivered suitably packed. Although the method of packing is left to the discretion of the manufacturer it should be robust enough for rough handling that is occasioned during transportation by Road.
All accessories shall be dispatched in boxes or cases. They shall be securely bound with wire and shall have all descriptive marking stamped thereon.

 

1. DRAWINGS

A complete set of transformer drawings should be submitted along with the tender. Three prints of the General outline and assembly drawing for the transformer shall be submitted to this office within four weeks of placement of order for approval. The drawing should give dimensions, weight, accessories, plan, front and side elevation. The dimensions, weights mentioned in the above drawing should be same as guaranteed by you in your tender offer. Finally, the contractor shall submit six prints of approved drawing.
The work of manufacturing assembling of transformers shall strictly conform to the approved drawing.