gtgt stgt specification vemagiri ii r0

2X382 MW CCPP at Vemagiri

L&T - S&L LIMITED

LARSEN & TOUBRO LIMITED SPECIFICATION FOR GENERATOR STEP-UP

TRANSFORMER FOR GTG AND STG

Rev : R0 Date : 16/9/2009

E&C POWER BUSINESS UNIT Page: 53

LARSEN & TOUBRO LIMITED E&C POWER BUSINESS UNIT

TECHNICAL SPECIFICATION FOR GENERATOR STEP UP TRANSFORMER FOR GTG AND STG

PROJECT: 2X382 MW CCPP at Vemagiri (Phase 2)

L&T’s CONSULTANT:

L&T-SARGENT & LUNDY LIMITED, BARODA PROJ. NO. Total No. of Pages: 54 No. of drawings:

REVISION CERTIFICATION

REVISION NO.

R0 R1 R2

NAME SIGN DATE NAME SIGN DATE NAME SIGN DATE PREPARED

REVIEWED

APPROVED


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REVISION SUMMARY SHEET

REV. DETAILS / DESCRIPTION DATE R0 For Procurement 16/9/2009


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INDEX

SL. NO.

CONTENT DESCRIPTION REVISION NO. OF PAGES

1. SECTION I TECHNICAL SPECIFICATION R0 41

2. SECTION II TECHNICAL DATASHEET R0 11

3. SECTION III TECHNICAL DATASHEET FOR COOLING SYSTEM

R0 1


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SECTION-I

TECHNICAL SPECIFICATION


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CONTENTS 1.0 INTENT OF SPECIFICATION...................................................................................................................6

2.0 PROJECT INFORMATION........................................................................................................................6

3.0 SYSTEM DESCRIPTION............................................................................................................................7

4.0 SCOPE OF WORK ......................................................................................................................................8

5.0 CODES AND STANDARDS ......................................................................................................................11

6.0 OPERATION AND CONTROL PHILOSOPHY......................................................................................12

7.0 DESIGN AND CONSTRUCTION REQUIREMENTS.............................................................................13

8.0 INSPECTION AND TESTING..................................................................................................................32

9.0 DRAWINGS / DATA / DOCUMENTS TO BE SUBMITTED BY BIDDER ALONGWITH THE BID .34

10.0 TRANSPORTATION AND HANDLING OF MATERIAL AND EQUIPMENT ……...………………...37

11.0 FITTING AND ACCESSORIES.………………………………………………….. ……...………………...40


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1.0 INTENT OF SPECIFICATION

1.1 This specification is intended to cover the design, engineering, manufacture,

inspection and testing at manufacturer’s works, packing, supply on FOR basis, supervision of erection, testing and commissioning at site of two (2) nos. of Generator step up transformers for GTG and two (2) Nos. of generator step up transformers for STG, inclusive of all fittings, accessories and spares for efficient and trouble-free operation.

1.2 It is not the intent to completely specify all details of design and construction

herein. Nevertheless, the equipment and installation shall conform to high standards of engineering design and workmanship in all respects and shall be capable of performing continuous operation in a manner acceptable to the Purchaser.

2.0 PROJECT INFORMATION

Owner GMR Energy Limited

Project 2X382 MW CCPP at Vemagiri

Owner’s Engineer / Consultant

TCE Consulting Engineers Limited

Purchaser

Larsen and Toubro Ltd.

Purchaser’s Engineer Max Site Temperature Min Site Temperature Elevation above Mean Sea Level

L&T-Sargent & Lundy Ltd. 50 Deg C 13 Deg C FGL: 24.5 M


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3.0 SYSTEM DESCRIPTION

A 2X382 MW CCPP is being set up at Vemagiri, Andhra Pradesh. The CCPP will have two (2) nos. Gas Turbine Generators, two (2) nos. Heat Recovery Steam Generators and two (2) nos. Steam Turbine Generator as main equipments.

The Gas Turbine Generator (GTG) and Steam Turbine Generator (STG) Transformers will be used for connecting the Gas Turbine and Steam turbine Generators to the 400kV system.

The Gas Turbine Generator transformer LV terminals will be connected to the 15.75 kV generator terminals by isolated phase bus-duct via the generator circuit breaker. The Steam Turbine Generator transformer LV terminals will be connected to the 15.75 kV generator terminals by isolated phase bus-duct. GTG/STG transformer HV terminals will be connected to the 400 kV switchyard by overhead stringing connection.

3.1 POWER SUPPLY CONDITIONS

Supply Description Variation Application

Generation System

15.75 kV, 3-, 3 wire, 50Hz, Non effectively earthed, Fault level: 83 kA for 1 sec at generator terminal (subjected to change)

15.75kV () 5% 50Hz (+)4%, (-)5% Combined volt. And freq.: 10% abs.

Generator, Isolated phase busduct, Generator Circuit Breaker, etc.

Power Evacuation

400 kV, 3-, 3 wire, 50Hz, Effectively earthed, 1550kV BIL Fault level: 40kA (rms) for 1 sec

400kV () 10% 50Hz () 5% Combined volt. And freq.: 10% abs.

Switchyard Equipment

L.T. Supply 415 V, 3-, 4 wire, 50Hz solidly earthed Fault level: 50 kA (rms) for 1 sec

Volt. : () 10% Freq.: () 5% Combined volt. And freq.: 10% abs.

Motors rated below 200 KW

DC Supply 220V DC, 2 wire, Ungrounded system,

Volt. : () 10%

DC alarm, control, indication and for DC lighting, DC motors.


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4.0 SCOPE OF WORK The scope of work under this package will include design, engineering, manufacturing, inspection and testing at manufacturer’s works, packing, supply on FOR site basis, and supervision of erection, testing and commissioning at site of GTG and STG Transformers as described hereunder. Items though not specifically mentioned but are required to make the system complete will be treated as included in the scope of Supplier unless otherwise specifically excluded. The total system design and engineering will be sole responsibility of Supplier.

4.1 SCOPE OF SUPPLY

4.1.1 The scope of supply shall cover the following:

a) Gas Turbine Generator Transformer: - Two (2) number. 275 MVA

b) Steam Turbine Generator Transformer: - Two (2) number. 170 MVA

c) Remote Tap Changing Cabinet (RTCC) with communication interface

4.1.2 The scope of supply for each of the above transformers shall include but not limited to the following: a) Fittings and accessories such as sampling Valve, Conservator drain valve,

Roller, Dial Thermometer, Oil and Winding Temperature indicator with high and very high indication contacts, Buchholz Relay, Top Oil Filter Valve, Inspection cover, Bus duct flange, Magnetic oil level gauge, inspection manholes / hand holes, lifting lugs, jacking pads, bi-directional flanged rollers, haulage lugs, skids, earth ads, neutral earthing down comers (2 nos.) supported on pin insulators, terminal marking, rating and diagram plates, marshalling boxes, conservators with breathers (flexible oil resistant air bag), valves for various purposes including draining, filtering, filling, magnetic (150 mm dia) and prismatic oil level gauges, anti-earthquake clamping arrangement, tank mounted radiators with accessories, and pressure relief valve etc. shall be provided.

b) Air release plug and 2 nos. Plugged pipe outlets for vacuum pulling to be

provided.

c) Pipe to soak pit with valve for quick oil drainage in case of fire to be provided.


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d) Cable, trays, supports and conduits between the Supplier’s devices and marshalling

box / cooler control cabinet except those specifically excluded. e) Structure for supporting conservator, radiator, control cabinet and any other

structure if required for supporting any parts of transformer. f) First fill of oil (as per IS 335) till the level generally required in the conservator

including with 10% extra quantity in non-returnable sealed containers. g) Touch-up paint as required at site.

h) Aluminium paint for GSU. i) All relevant drawings, data, routine & type test reports, erection & commissioning

instructions and operation & maintenance manuals. j) Start-up and commissioning spares.

k) Bidder shall indicate the list of recommended spares. l) Bidder shall supply special tools, tackles & materials as required for erection,

commissioning & maintenance and shall include in the bid separately.

4.2 SCOPE OF SERVICES Bidder shall provide the following services under the scope of this specification:

a) Design and engineering in accordance with specification requirements, manufacturing and arranging inspection.

b) Packing, loading, for transportation and delivery of all the materials by rail/road

to site. c) Supervision of erection, testing and commissioning. Bidder shall arrange their

representatives/commissioning engineers for supervision of erection/installation, testing, start-up/charging and commissioning of the supplied equipment at site. The responsibility of commissioning engineers shall be to commission the transformers & associated systems supplied by the bidder to the satisfaction of owner/ owner’s engineer and hand over the unit to the


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Owner. In addition to that, Commissioning Engineers shall be available at site during grid synchronisation.

Purchaser reserves the right to call these engineers at a notice of 7 days.

d) Submission of all necessary data sheets, drawings, documents, and QAP for

Purchaser’s approval. Submission of test certificates and carry out all testing / inspection, inline with approved QAP. Vendor will also provide facilities for Purchaser’s / Owner’s representatives to witness various tests inline with approved QAP.

e) Submission of detailed civil/structural designs, including all equipment

foundation loading data. f) Submission of control schematics for cooler cabinet and marshalling box. m) The bidder shall give an optional price for training of Owner's engineers at the

manufacturing works and plant site. Bidder to indicate in his bid, the duration of training in man-days at each location and man-day rate considered. The same shall however be finalised before award of contract.

n) Submission of all drawings/manuals and as built.

4.3 TERMINAL POINTS

a) HV bushings (Suitable for overhead stringing connection) b) LV bushings (Suitable for Isolated phase bus connections)

c) Neutral grounding point

d) Ground pads for connection to purchasers earth Grid.

e) Marshalling box (All Purchaser’s external power (3Phse 415V AC and 220V

DC), control & instrument cables) 4.4 EXCLUSIONS

a) Civil foundations for transformer including rails. However, the foundation

details shall be submitted along with the offer.


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b) Fire protection system.

c) Erection and installation and commissioning except supervision.

d) Oil filtration / treatment at site. e) Cabling beyond transformer marshalling box.

f) 415 V, 3-phase, 3-wire, 50 Hz power supply and 220 V DC power supply (as

required). Bidder shall clearly indicate the auxiliary power supply requirements (Number of supplies, voltage level, current ratings etc.) in his bid.

g) Connections to the owner’s station earthing grid and lightning protection. h) Protective relays and control panel for transformer protection.

5.0 CODES AND STANDARDS

5.1 The equipment, systems and services furnished as per this specification will conform to the codes and standards mentioned here which are furnished for Supplier’s guidance.

5.2 In case of any conflict between this document and the Indian and Internationals

codes and standards, referred to herein, the stipulations of the more stringent one will prevail.

5.3 Standards as applicable from the following list, or other internationally accepted

equivalent standards should be used in the design, manufacture and testing:

Power transformer IS : 2026 Fittings and accessories IS : 3639 Loading of oil immersed

transformers IS : 6600

Oil IS : 335 Bushings IS : 2099


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Degree of protections IS : 2147 Tests IS : 2026 Tolerance on guaranteed particulars

IS : 2026

Buchholz relay IS : 3637 Electrical insulation classified by thermal stability.

IS : 1271

Application guide for power transformer.

IS: 10561, 1983

Current Transformers IS: 2705 Specifications for Three Phase Induction Motor

IS: 325

Fittings and accessories for Power Transformers.

IS: 3639

Specification for PVC insulated (heavy duty) electric cable

IS: 1554

Application Guide for OLTC IS-8478 Application Guide for CTs IS-4201

6.0 OPERATION AND CONTROL PHILOSOPHY

6.1 Generator transformers covered under this specification, shall be operated in parallel with the 400 kV grid (paralleling will be at the power plant 400 kV bus). The electrical power generated from the CCPP will be evacuated to the 400kV


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power grid. For this purpose the CCPP shall have its own 400 kV switchyard with a 1½-breaker arrangement.

6.2 The Generator Transformer shall be so sized as to be able to evacuate power from

the GTG / STG to which it is connected under all conditions of ambient temperature. Gas Turbine curve showing Power output w.r.t ambient temperature is attached with this specification. GTG Transformer rating should be higher than the Gas Turbine output throughout the ambient temperature range.

6.3 Cooler control: Two (2) 100% capacity separately mounted radiator banks shall be

provided. Each bank shall be provided with adequate number of fans and pumps and one oil pump and one fan spare. Each radiator bank shall be provided with uni-directional bypass valve to permit oil to bypass the pump in the event of pump failure. It shall be possible to completely isolate any one of the radiator banks for maintenance, while the transformer is in service. Flexible expansion joints, one each, on top and bottom pipe connections for each radiator shall be provided. Each radiator bank shall have at least two (2) extra radiators to facilitate usage of the same in case of leakage in the other radiators If radiators are arranged in groups, each group of radiator shall have upper and lower shut-off valves with blanking at either ends. The cooling fans for AF and cooling pumps for OF shall have provision for local and remote operation. The controls shall also consist of an auto / manual selection. Fan running indication from auxiliary contact of fan power contactor and an oil flow indicator along with an electrical contact for alarm / interlock shall be provided for the confirmation of the oil pump operating in a normal state.

Tap changer control: Generator transformers shall be equipped with On-Load tap changer (OLTC) of range +7.5% to -15% in steps of 1.25% on the HV side and suitable for bi-directional power flow. OLTC shall be operated from local OLTC panel as well as from RTCC & remote. Tap position indication shall be provided in local OLTC panel, RTCC and remote. Suitable interlocks shall be provided to prevent inadvertent / mal operation of the tap changer.

7.0 DESIGN AND CONSTRUCTION REQUIREMENTS 7.1 GENERAL

a) The transformers shall be of the latest design, mineral oil immersed type. Transformers shall be suitable for outdoor installation.


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b) The transformer shall be capable of remaining in operation without injurious heating at full load for at least 10 minutes when complete forced cooling equipment has failed.

c) Transformers shall be capable of withstanding the mechanical and thermal

effects of short circuit resulting from different forms of system faults including transfer surges, which could be reflected through capacitor coupling between windings. The dynamic ability to withstand short circuit shall be demonstrated by calculations.

d) The type of cooling shall be Oil Natural Air Natural, Oil Natural Air Forced and

Oil Forced Air Forced, as specified, and the corresponding ratings of transformer shall be as indicated in the specific requirements.

e) The transformer shall be designed to deliver rated MVA continuously on all

tapings without exceeding the applicable temperature rise limits for the power supply conditions.

f) The transformer shall be capable of withstanding shock loading / unloading

during parallel operation. There shall be no limitation imposed by bushings, CTs and other accessories.

g) The transformer and all accessories including bushings, CTs, etc shall be

capable of withstanding the short circuit stresses due to terminal fault on one winding with full voltage maintained on the other winding for minimum period of one (1) seconds without damaging effect as well as any external short circuit at bushing terminal.

h) The Transformers shall operate without injurious heating at the rated MVA

continuously at any voltage within + 10% of the rated voltage of the Tap. i) The transformer shall be free from annoying hum or vibration. The design shall

be such as not to cause any undesirable interference with radio or communication circuits.

j) The transformer and the associated accessories shall be suitable for bi-

directional flow of power. The transformer will be back-charged from the EHV system to charge the unit auxiliary transformers.


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k) Core clamping arrangement shall be equipped with core and coil lifting eyes. Anti-earthquake clamping arrangement shall be provided.

l) Jacking, lifting, pulling, rolling, and skidding provisions must be provided to

allow for installer’s choice of installation methods. Transformer cover shall be equipped with lifting eyes duly painted with zebra of the colour combination based on the weight of the assembly to be lifted as per the relevant standard.

m) Transformers shall be so designed that the average sound level will not exceed

the value 85dB at the distance of 1 meter from the equipment, as measured at factory and site.

n) The transformer shall be mounted on bi-directional flanged wheels and shall be

provided with boltable & lockable wheels. The locking arrangement shall be furnished by the Bidder for review.

o) All hardware used in the transformer and accessories shall be zinc plated &

chrome passivated / stainless steel to suit the site environment.

7.2 TRANSFORMER TANK

a) The generator transformer shall be outdoor type, of welded mild steel plate construction fabricated from good commercial grade low carbon steel of adequate thickness and provided with gaskets steel cover plates. Base shall be suitably reinforced to prevent any distortion during lifting. Base channels shall be provided with skids and pulling eyes to facilitate handling. Bell type design shall be adopted for transformer tank.

b) The tank of the transformer along with radiators, conservators, bushings and

other fittings shall withstand full vacuum of 760 mm of Hg while filling the oil under vacuum and also an excess internal pressure of 0.35 kg/sq. cm.

c) All seams and those joints not required to be opened at site shall be welded and

wherever possible they shall be double welded in factory itself for absolute oil tightness. After completion of tank and before painting, dye penetration test shall be carried out on welded parts of jacking bosses, lifting lugs and all load bearing members. Grinding shall clean all welds. Any tack welding deposits shall be removed.


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d) The tank covers shall be fitted with thermometer pockets (in locations expecting maximum operating oil temperature) for bulbs of oil and winding temperature indicators. The thermometer pockets shall be filled with a captive screwed top to prevent ingress oil water. It shall be possible to remove these bulbs without lowering the oil in tank.

e) Tank shields and two (2) inspection openings to be provided in transformer tank.

Tank shields shall be such that no magnetic field shall exist outside the tank. They shall be of magnetically impermeable material. If required impermeable shields shall be provided in the tank for positioning the core and coil assembly. The inspection covers shall be suitably designed to prevent ingress of rainwater and shall have suitable lifting arrangements. Bushings, turrets, inspection covers, thermometer pockets etc. shall be designed to prevent ingress of water into, and leakage of oil from the tank.

f) Tanks shall not resonate when excited at the natural frequency of the equipment. g) The tank, radiator banks and marshalling box shall have at least two (2) distinct

stainless steel earth pads terminals, capable of carrying maximum system earth fault current for a duration of one (1) sec, for connection to Purchaser’s earth grid by 75 x 10 mm GI Flat.

h) Flanged bi-directional wheels are to be provided at the base with locking

arrangements. Jacking steps shall be provided. It shall be possible to change the direction of the wheels through 90 Degrees, when Transformer is lifted on Jacks to permit movement of the Transformers both in longitudinal and transverse directions.

i) Tank, tank cover and other associated components on the transformers shall have

electrical continuity for earthing. j) All the bolted connections shall be fitted with weatherproof hot oil resistant

SRBP gasket / nitrile rubber gasket in between for complete oil tightness. If gasket is compressible, metallic stops shall be provided for avoiding over compression. Necessary bridging with copper strips shall be provided for the electrical continuity across a gasket joint.

k) Suitable guides shall be provided for positioning the various parts including core

and coil during assembly or dismantling. Adequate space shall be provided


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between the cores and windings and the bottom of the tank for collection of any sediment

l) Each tank shall be equipped with the following valves with the standard flange

connection for external piping.

i) One drain and lower filter valve located on the low voltage side of the transformer and so placed to completely drain the tank. The valve shall be equipped with a small sampling cock.

ii) One filter valve located at the top of the tank on the high-voltage side. The opening of this valve shall be baffled to prevent aeration of the oil.

iii) One filter valve, located diagonally opposite to (ii) slightly above the bottom of the tank.

iv) Spring loaded pressure relief device, as required, to operate at a pressure below the test pressure for the tank.

v) All valves excepting radiator valves shall be of gunmetal. Radiator valves shall be of cast iron with stainless steel / gunmetal moving parts. All valves shall be provided with stopper.

vi) Suitable pad locking arrangements should be provided for drain & bottom sampling valves, to lock them in close / open position. All valves should be provided with clear open/close position indications. Wherever rising spindle type valves are provided the valves should be clockwise rotating for closing operations.

m) In addition to the valves mentioned above, each transformer shall be provided

with a suitable nozzle along with the valve for oil spray during filtering for degasification and other benefits like extraction of residual moisture from winding. All points terminating in a flanged connection exposed to atmosphere shall be supplied with blank flanges, bolts, nuts and gaskets.

7.3 TRANSFORMER CORE AND WINDINGS

7.3.1 CORE

a) Core shall be constructed of high grade, low loss, high permeable CRGO silicon

steel laminations. Maximum flux density in any part of the Core and Yoke at rated MVA, voltage and frequency shall be such that under 10% continuous over voltage condition it should not exceed 1.9 Wb/m2. Bidder shall submit the over fluxing curve along with the offer.


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The transformer shall be suitable for following over fluxing duties: 110% - continuous 125% - 1 minute 140% - 5 seconds

b) The framework, clamping arrangement and general structure of the cores of

each transformer shall be of robust construction and shall be capable of withstanding any shock to which they may be subjected during transport, installation and service. Anti-earthquake clamping arrangement shall be provided.

c) The Transformer shall be subjected to Load rejection conditions and shall be

able to withstand 1.4 times the rated voltage for 5 seconds. d) The transformer shall be subjected to load rejection conditions and shall be able

to withstand 1.4 times the rated voltage for 5 seconds as per IS: 2026. e) The framework and the core bolts shall be efficiently insulated from the core so

as to reduce the eddy-currents to a minimum.

f) The limbs and the yokes of the core shall have similar sections to minimise heating and noise arising from transverse flux. The joints in the laminated magnetic circuit shall be interleaved. Necessary cooling ducts shall be provided for heat dissipation from the core so that the anticipated maximum hot spot temperature in the core shall not be injurious to any material used in the core assembly.

g) The frame, clamps and core-bolts shall be electrically insulated from the core.

Such insulation shall be capable of withstanding maximum temperature existing in the core. For this purpose, Class-A or better insulation shall be used. Core clamps shall be electrically connected to the tank.

h) Core shall be grounded with removable test connection accessible from

manhole. All metal parts of the transformer with the exception of the individual core laminations, core bolts and associated individual clamping plats shall be earthed. The magnetic circuit shall be earthed to the clamping structure at one point only through a bushing brought out separately on the tank cover and then grounded to the transformer tank.


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i) Earthing of Coil Clamping Rings – Where coil-clamping rings are of metal at earth potential, each ring shall be connected to the adjacent core clamping structure on the same side of the transformer as the main earth connection.

j) Size of Earthing Connections – Main-earthing connections shall be designed for

the maximum fault rating in magnitude and duration. k) The insulation of core to bolts and core to clamp plates shall be able to

withstand a voltage of 2 kV RMS for one (1) minute. l) The completed core shall be provided with the lifting eyes and lugs to facilitate

its removal from the transformer tank and shall be adequately braced & supported to prevent movement during transit or service. All steel sections used for supporting the core shall be thoroughly sand blasted after cutting, drilling and welding.

7.3.2 WINDINGS

a) The windings shall be made of enamelled copper conductors of high

conductivity and 99.9% purity. Windings shall be designed to withstand the thermal and dynamic short-circuit stresses to meet requirement of the Standards.

b) Insulation material shall be of proven design. Coils shall be so designed that impulse and power frequency voltage stresses are minimum. Losses will be considered during evaluation. The loss figures quoted by the bidder shall not have any positive tolerance and shall be inclusive of power consumption of associated auxiliaries like fans, coolers, marshalling box etc.

c) All windings shall be fully insulated for the highest system voltage of 420 kV

systems. The 420 kV star connected windings shall have graded insulation while 15.75 kV winding shall be uniformly insulated, as defined in IS: 2026. The insulation shall be as specified in Vol III, Section II, Annexure-1. Coils shall be so insulated that impulse and power frequency voltage stresses are minimum. All neutral points shall be insulated to withstand applied voltage test as defined in the relevant standard.

d) The transformer winding shall be suitably clamped by mechanical means at the

top and bottom to prevent shifting which may occur through rough handling and vibration during transport, switching & other transient conditions like short


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circuit. Anti-earthquake clamping arrangement shall be provided. End connection of winding to be properly insulated. The winding structure and major insulation shall be designed to permit unobstructed flow of cooling oil through core cooling ducts to ensure efficient core cooling.

e) The windings shall be duly sectionalised. Accessible joints brazed or welded and finished smooth shall connect similar sections. No corona discharge shall result on the winding upon testing the transformer for induced voltage test as specified in IS.

f) The windings also be thoroughly seasoned during manufacture by the

application of axial pressure at a high temperature for such length of time which shall ensure that further shrinkage is unlikely to occur in service. Provision shall however be made for taking up any further contraction by means of spring loaded and adjustable clamps or other similar devices.

g) In the post-order stage, drawings shall be submitted showing type of winding,

methods of bracing and clamping details of electrical connection within windings and details of oil cooling ducts and precautions taken to prevent shrinkage of insulating material in service.

h) The end turns of the high voltage windings shall have reinforced insulation to

take care of the voltage surges likely to occur during any abnormal condition.

i) The transformer winding shall be connected in proper vector-groups. All termination and tapping marked shall be in accordance with IS 2026.

j) The windings shall be located in a manner, which shall ensure that they remain electrostatically balanced and that their magnetic centres remain coincident under all conditions of operation.

k) The windings shall be so designed that all coil assemblies of identical voltage

ratings shall be interchangeable, and field repairs to the windings can be made readily, without special equipment. Insulating spacers and the barriers/bracing shall support the coils and other insulation used in the assembly of the windings shall be arranged to ensure a free circulation of the oil and to reduce hot spots in the windings. Windings shall be suitably designed so as to conduct tan delta test for winding/bushings at site or at factory.


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l) All materials used in the insulation and assembly of the winding shall be

insoluble, non-catalytic, and chemically inactive in the hot transformer oil, and shall not soften or otherwise be adversely affected under the operating conditions.

m) All threaded connections shall be provided with locking facilities. All leads

from the winding to the terminal board and bushings shall be rigidly supported to prevent injury from vibration. Guide tubes shall be used where practicable.

n) The winding shall be brought out through bushing and provided with suitable

terminal connectors. o) The assembled core and windings shall be vacuum-dried and suitably

impregnated before removal from the treating tank. The copper conductors used in the coil structure shall be best suited to the requirements and all permanent current carrying joints in the windings and the leads shall be welded or brazed.

p) Sharp bends should be avoided in the windings as far as possible, where

unavoidable such bends should be reinforced with extra insulation tapes.

q) The tolerance for the winding resistance measurement for different phases but at same taps shall be limited to 1%.

r) The design of the magnetic circuit shall be such as to avoid static discharges due

to development of short circuit paths within itself or to the earthed clamping. s) Loss Capitalisation: For comparison of tenders, the losses will be capitalised by

adding to the transformer price as given below:

Copper Loss – Rs. 0.85 Lacs per kW Iron Loss – Rs. 1.6 Lacs per kW

7.4 CONSERVATOR a) The conservators shall have adequate capacity to accommodate oil preservation

system and volumetric expansion of the total cold oil volume in the transformer and cooling equipment for a change in oil temperature from minimum to maximum oil temperature with specified maximum temperature rise.


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b) The conservators shall be bolted into position so that it can be removed for cleaning purposes.

c) The conservators shall be fitted with magnetic type oil level gauge (MOG) with two independent low level electrically insulated potential free alarm contacts wired up to the MOG’s terminal box, further wired up to the control cabinet terminal strip. The oil level at 30C shall be marked on the gauge; however, the range of the MOG shall be from minimum to maximum oil level. The dial size shall be 150 mm. The conservator shall also have a prismatic oil level gauge. Both the gauges shall be placed on the opposite sides of the conservator.

d) In the conservator, flexible oil resistant air cell nitrogen fill (rubber diaphragm) breathing through silica gel breather shall be provided. The air cell shall be made up of nitrile rubber reinforced with nylon rubber and with nylon cloth. As such air cell used shall be suitable for operating continuously at the temperature rise limits. Air cell of conservator should be able to withstand the vacuum during installation / maintenance periods. Otherwise provision shall be kept to isolate the conservator from the main tank when the later is under vacuum by providing a vacuum sealing valve or other suitable means in the pipe connecting main tank with the conservator. The connection of air cell to the top of the conservator shall be by air proof seal preventing entrance of air into the conservator. The air cell material should not get decomposed under the severe most operating conditions and should also not react with oil / oil vapour. Necessary fittings (valves) with pressure gauge shall be supplied for commissioning the air cell.

7.5 TRANSFORMER COOLING SYSTEM 7.5.1 GENERAL

a) The cooling of transformer shall be ONAN/ONAF/OFAF. The ONAN rating

shall be at least 60% of the OFAF rating and ONAF rating shall be at least 80 % of the OFAF rating.

b) Total cooling system shall be so designed that the transformer be capable of operating at full load for 10 minutes after failure of the oil circulating pumps without injurious heating and calculated hot spot temperature not exceeding 150 Deg C.

c) The cooler units shall be so arranged such that the transformer tank, bus-ducts /

cabling chamber, etc do not fall in the direct path of hot air coming out of the


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unit coolers. Each cooler unit shall have its own cooling fan and pump, oil flow indicator with shut-off valves, oil filtering valves at top and bottom, a drain valve, air release plugs, etc. An oil flow indicator along with an electrical contact for confirmation of each oil pump operating in a normal state will be included.

d) Cooler units shall be connected to the tank by machined steel flanged joints

provided with suitable quality gaskets for sealing purpose. The flanges shall be welded to the both cooler units and the tank. At each cooler unit connection on the tank an indicating shut off valve shall be provided which can be fastened in either open or closed position. A separate oil tight blank flange shall be provided for each tank connection for use when the cooler unit is detached. Each cooler unit shall have a lifting eye, an oil drain at the bottom, and a vent at the top. The vent and drain plugs of coolers should be provided with Teflon gaskets. Flexible Expansion Joint, one each on top and bottom pipe connection for each radiator bank shall be provided.

e) Radiators need to be properly and freely supported from the ground such that the transformer can be taken out for maintenance without disturbing the radiators.

f) Each cooler unit shall be provided with the following:

i) A valve at each point of connection to the transformer tank. ii) A valve in the main oil connection at the bottom of each cooler in addition

to those mounted on the transformer tank. iii) Loose blanking plates to permit the blanking off of the main oil

connection to the top. iv) A 50mm filter valve at the top of each cooler. v) A 50mm-drain valve at lowest point of interconnecting oil pipes. vi) A thermometer pocket fitted with captive screw cap, in the inlet and in the

outlet oil pipes. vii) Flanged air release plugs. viii) Lifting eye ix) Flexible Expansion Joints

7.5.2 TRANSFORMER COOLER CONTROL a) The cooler control shall be redundant with two independent power supplies.

Two 415V, 3 phases, 3-wire, 50 Hz. Power supplies will be provided by the Purchaser for feeding to the auxiliaries of the transformer. The marshalling box shall have provision to accept these power supplies and shall have provision of


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auto changeover. The cooler control shall be suitable for both remote and local indication.

b) Control equipment for pump and fan motors shall be mounted in a marshalling box to be installed adjacent to the transformer and shall include the necessary connections with automatic control and annunciation equipment with provision for auto / manual control for each group of fans and oil pumps.

c) 240V, 1 ph, AC supply shall be derived by the Bidder from the 415V supplies provided by the Purchaser to facilitate 240V AC supply to lights and heaters in marshalling box.

d) The auto-changeover scheme shall be designed based on under-voltage relay logic, to take care voltage dips on 415V supplies.

e) The main and starter control circuit for each fan and pumps feeder shall be provided with fuses at both ends so that in case of fault on any contactor coil only that particular fan shall be cut out and other fans can remain in service. Each feeder shall also be provided with double pole switches to enable isolation of the corresponding contactor in case replacement of the same is necessitated.

f) A single metal-enclosed main isolating switch, with HRC fuses, shall be provided for the cooling plant contactor group.

g) The contactors, starters and relays provided in the marshalling box shall be of reputed make. Bidder shall furnish the list of sub-vendors for purchaser’s approval.

h) The switching in or out of the cooling equipment shall be controlled by winding and oil temperature and there shall be provision for automatic switching in or out at predetermined temperature levels which should be capable of adjustment and setting at will.

i) A local mechanical indication scheme for all annunciations shall be provided in the marshalling box with mechanical target relays/contactors.

j) Anodised aluminium plate showing details of all terminal nos. shall be provided along with marshalling box.

7.6 BUSHINGS

a) All bushings shall conform to the requirements of IS:2099 - 1973 for the

respective application voltage. Bushings of identical ratings shall be


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interchangeable. The high voltage bushings shall be of oil impregnated paper (OIP) type condenser bushings and without arcing horns. LV bushings shall be porcelain type and without arcing horns. All current carrying parts of the power transformer shall be copper or copper alloy material and surfaces shall be plated to inhibit deterioration. HV bushings shall be provided with terminal connectors suitable for termination of ACSR conductor. Where current transformers are specified, the bushings shall be removable without disturbing the current transformer. Bushing rated for 400A and above shall have non-ferrous flanges and hardware.

b) The neutral of the star-connected winding shall be brought out to a separate

bushing terminal. The neutral bushing shall be provided on the tank side and the lead of the two (2) earthing conductors from the neutral bushing shall be brought-down to the ground level for Purchaser’s grounding connection. Tank mounted pin type support insulators shall be provided for supporting the neutral earthing bar along its run from the neutral bushing to ground level.

c) The colour of the bushings shall be manufacturer’s standard. Bushings are

subject to tan delta test at site and shall meet the respective standard. d) WTI CT shall be provided on the transformer as per the design requirement.

e) All CT secondary terminals shall be wired up to the transformer-marshalling box

and terminated in terminal blocks. The terminals shall be stud type and dropping type CT shorting arrangement shall be provided. CT terminals shall be spring-loaded type and shall short the CT terminals on removing the connection. Knee point voltage, magnetising current and Rct for Class PS CTs shall be intimated to the bidder during detailed engineering.

7.6.1 BUSDUCT INTERFACE The LV bushings shall be cover mounted and have a flanged enclosure suitable for connection to an isolated phase busduct. Ample space and access shall be provided for the installation of the isolated phase bus duct. The busduct interface chamber will be air filled and all current carrying parts in it will be properly insulated, supported and braced. The low point of flanged enclosure will be provided with a screened drain.


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7.7 ON LOAD TAP CHANGER

a) On Load Tap Changer shall be provided on the HV winding of the transformer. The OLTC gear shall be designed to complete successfully tap changes at 150% of rated current. Devices shall be incorporated to prevent tap change when the through current is in excess of the safe current that the tap changer can handle. The OLTC gear shall withstand through fault current without injury.

b) The OLTC’s tap changing gear shall comply with IEC: 60214, IS:8478 and CBIP

manual on transformer - 1987. The tap changer shall be mounted in a separate tank or compartment in accessible position on the transformer tank. The operation of the transformer at any of the taps shall not produce phase displacement. All the tap changing switches shall be rated for full bi-directional power flow.

c) The OLTC gear shall have diverter resistance or reactance and current diverting

contacts. The contacts shall be accessible for inspection and their tips shall be replaceable. OLTC oil chamber shall have oil filling, drain and sampling facility. It shall be provided with oil level indicator and alarm contacts. On load oil filter connection orifices, valves and silica gel breather shall be provided.

d) OLTC shall be provided with separate conservator and oil temperature indicator

with contacts and oil surge relay.

e) OLTC devise shall be such that the oil in the compartment containing making and breaking contacts does not mix with oil in other compartment of OLTC or transformer tank.

f) All contacts shall be silver plated and held in position under strong contact

pressure to ensure low contact drop and avoid pitting.

g) OLTC shall be provided with the following modes of operation. - Local - manual - Local - electrical

- Remote – electrical

h) Mechanical Control

The cranking device for operation of the OLTC gear shall be removable and located at a height not exceeding 1500mm above ground level for easy operation.


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The mechanism shall be complete with normal accessories including at least the following

- Tap position indicator - Mechanical operation counter

- Mechanical stops to prevent over cranking the mechanism beyond extreme tap positions

- Cut off of power supply when manual handle is inserted

i) Electrical Control

Control circuit shall incorporate the following:

- Local-electrical operation - Remote-electrical operation from RTCC/DCS - Device to ensure a positive and full completion of tap change once it is Initiated even if the control supply or any relay fails - Protective devices to put the transformer out of service in case of abnormal Tap changer performance and to initiate an alarm. - Each operation of either the raise or lower control switch shall cause one tap

Movement only. The control switch shall be returned to the off position for each successive operation.

- All electrical control switches and local operation gear shall be clearly labelled to indicate the direction of the tap changing.

- Provision shall be made to cut out electrical control to prevent OLTC operation during over-loaded operation of the drive mechanism motor.

j) Local Tap Changing Cubicle:

A local tap changer cubicle shall be provided for housing motor drive mechanism for on load tap changing at transformer. The tap changing cubicle shall be fabricated with 2.5 mm CRCA sheet steel complete with all wiring, fuses, links, cubicle illumination lamps, anti-condensation heater with thermostatic control switch, gland plate, etc. The cubicle shall be suitable for outdoor installation. The tap changer shall contain the following: - Inside tag with control scheme indelibly marked.

- Motor drive mechanism - Thermostatically controlled space heater - Tap position indicator


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- MCB with magnetic and thermal overload devices for controlling incoming supply to OLTC.

- Limiting devices - Padlocking arrangement for hinged cabinet door - Operation counter

- Cubicle lighting - Oil Temp. Indicator - Removable cable gland plate

k) The driving motor and electrical control of the motor drive mechanism shall be

designed to operate satisfactorily within the limits of 80% to 110% of the rated AC voltage of 415V 10%, 3 phase, 50Hz 5%.

l) Remote Tap Changing Cubicle (RTCC)

The RTCC shall be indoor simplex type, free standing, totally enclosed, floor

mounting type with rear access door. The panel shall be fabricated from structural steel framework enclosed on all sides and top by CRCA sheet steel of minimum 2.5mm thickness. The panel shall be complete with all wiring fuses, links, illumination lamps with door switch, anti-condensation heater with thermostatic control switch, gland plate, etc.

The RTCC shall comprise of the following.

- Local Remote selector switch individual/parallel selector switches. - Raise /lower control switch - Tap position indicator - Digital type - Tap changer in local position lamp - AC supply failure lamp and Bell - Timer to control OLTC hunting - Indicating lamp for tap changer in progress - Alarm, accept, reset, lamp test push buttons

m) Indicating lamp for Tap position maximum reached, Tap position minimum reached and Tap changer stuck to be provided in local panel and also contacts for remote indication to be provided.

OLTC devise shall be suitable for remote electrical parallel control with Master-Follower scheme.


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n) Automatic and manual operation facility including hardware, AVR as required shall be provided for the OLTC system. o) Provision shall be kept for complete remote operation of OLTC. p) Cut off of power supply when manual handle is inserted.

7.8 CONTROL CABINET AND WIRING

a) A sheet steel, weather proof, vermin and dust proof marshalling box suitable for out door application shall be furnished with each transformer to accommodate :

i) Temperature indicators. ii) Transducers for WTI/OTI iii) Terminal blocks for incoming and outgoing cables. iv) Interposing Relays / Amplifiers for the Proximity switches

b) The sheet steel used shall be at least 2.5 mm thick. The box shall be free standing

floor-mounted type and having a sloping roof canopy. The degree of protection shall be IP 55 for outdoor application

c) The temperature indicators shall be so mounted that the dials are not more than

1600 mm from ground level. The marshalling box door shall have a glazed window of suitable size for convenience of temperature indicators reading.

d) The marshalling box shall contain all control circuits, auxiliary relays, terminal

boards, etc., as required to provide a single interface location e) Following signals will be hooked up to the purchaser’s relay panel located at

Central Control Room. The transformer marshalling box shall have necessary dedicated potential-free contacts and 4-20mA signals for hooking up with Purchaser’s panels:

Equipment Signal Generator transformer control cabinet (Marshalling box)

Buchholz relay alarm Buchholz relay trip Winding temperature alarm Winding temperature trip Oil temperature alarm Oil temperature trip


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Equipment Signal Oil level low alarm Pressure relief device trip 4-20mA signal from WTI/OTI Oil flow indicator for each cooler bank Cooler bank failure Cooler bank in service AC control supply failure DC control supply failure

f) Wiring from the current transformers and other control and alarm equipment

shall be carried out in conduits or alternatively in concealed trays and terminated in the marshalling box.

g) All incoming cables shall enter the marshalling box from the bottom. The cable

glands shall be of brass and double compression type. A removable undrilled gland plate shall be provided at the bottom of the box for accommodating glands for Purchaser’s incoming and outgoing cables, which shall not be less than 450 mm from finished floor level. The gland plate shall be minimum 3.0 mm thick and shall be made into detachable halves, for facilitating the termination of incoming and outgoing cables separately. The gland plate and the associated compartment shall be sealed in a suitable manner to prevent the ingress of moisture, rodents, insect etc.

h) Terminal blocks shall be furnished in the marshalling box. All terminal blocks

shall be of disconnecting type. Terminal blocks for short circuiting the current transformer shall be provided separate from the terminal blocks accommodating the control and indicating circuits. The direct and alternating current terminals shall be isolated from each other.

i) All tapping of CTs shall be brought to terminals in the marshalling box and 10%

spare links shall be provided. The terminals for the current transformer leads shall be suitable for accommodating 6 sq.mm. cable leads while the terminals for the control and other circuits shall be suitable for accommodation 2.5 sq.mm. cable leads. Atleast 20% spare terminals for control wiring shall be provided.

j) CT terminal blocks shall be provided with test links and isolation facilities.

Neutral CT terminals shall be brought out to the terminal box for the connection. Terminal blocks for 415 V power cables shall be suitably sized to terminate the required size of cable.


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k) Suitably rated switches shall be provided to enable the control supply to the

transformer to be cut off from the marshalling box. l) Enough space shall be provided at the bottom of the operating marshalling box to

mount the Purchaser's control cables glands. The number and size of the cable glands shall be intimated later. All terminal blocks for control shall be rated for minimum 10 Amps.

m) Complete control cabling between the transformer and the marshalling box shall

be in the scope of the Bidder and it shall be supplied loose along with the marshalling box.

n) All wiring in the housing shall be stranded copper and the insulation shall be

1100V grade PVC and shall be of reputed make. Size of wires shall be not less than 4 sq.mm. for CT leads and not less than 2.5 sq mm for other connections. CT circuit wiring shall be done using colour coded wires for better identification.

o) Not more than two (2) wires shall be connected to one terminal.

p) Wire and cable bunching saddles PVC channels shall be provided on all terminal

blocks on either side. The wire terminals shall be engraved or otherwise indelibly marked ferrules and the wires shall be colour coded. All control wires shall have cross ferruling at both ends for identification.

q) All devices and terminal blocks inside the marshalling box shall be clearly

identified by symbols corresponding to those used on applicable schematic or wiring diagram. The terminal block shall be stud type. All terminal blocks should have terminal nos. on either side of terminals.

r) All major equipment, devices, panels, and cubicles shall be provided with

stainless steel nameplates fastened with self-tapping screws. Nameplates shall be provided on doors of cooler control cabinet, CT junction box and thermo junction box. They shall be located so that a person standing on the ground can read them without visual aids. Each current transformer shall be provided with a diagrammatic type nameplate located near the CT terminal blocks. Self-adhesive labels shall not be used.

s) Stud type fuse mounts shall be provided with an insulating cover as protection

against accidental contact with live terminals.


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t) Drawing pouch with cooler control scheme drawings covered in the polythene

paper shall be provided inside marshalling box on the door.

u) All alarm and control devices shall be ungrounded.

v) The marshalling box shall be supplied with space heater, cubicle lighting (Compact fluorescent lamp) and 240 V receptacle with ON-OFF switches and associated fuses. It shall be located in such a way that the same shall not face towards the transformer. Heaters shall be provided with suitable protective cover to avoid accidental contact with the element (i.e. wire mesh enclosure with asbestos sheet cover at the front).

w) Bidder shall furnish a list of the relays, control switches, timers, etc. indicating

the make, type, auxiliary supply requirements, contact rating etc. along with the quotation.

8.0 INSPECTION AND TESTING

a) Bidder shall furnish his standard Quality Assurance Plan along with the bids. Inspection and testing shall be as per approved QAP. Transformer oil (both test purpose as well as fresh oil) shall be as per relevant IS.

b) The bidder shall use his own transformer oil for testing purpose and the fresh oil

shall be supplied to site. In case of transformer are supplied oil filled than fresh oil shall be filled in presence of Purchaser. The insulating oil shall conform to the latest revision of IS-335.

c) The necessary topping up oil shall be supplied for the Transformer in non-

returnable container. 10% excess oil shall also be provided, in non-returnable containers suitable for outdoor storing for one GTG Transformer.

d) As a minimum, the following tests shall be carried out:

i. Type tests

Following type tests and special tests (excluding short circuit test) as per IS 2026 shall be conducted on one transformer of each rating.

Temperature rise test.


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Measurement of zero sequence impedance.

Measurement of acoustic noise level.

Measurement of the harmonics of the no-load current.

Measurement of the power taken by the fans and oil pumps

ii. Additional Type Tests

Additionally, the following tests shall be conducted as type tests on one transformer of each rating.

Impulse on all three legs of HV and LV windings including chopped wave

tests. Heat run test with dissolved gas analysis before and after.

Vacuum withstand and deflection measurement on tank.

Pressure test on tank with deflection measurement.

Determination of cooler losses.

Partial discharge test.

Radio interference voltage with 400 kV bushing.

iii. Routine Tests

The following routine tests as per IS : 2026 shall be conducted on each of the transformer. Measurement of winding resistance. Measurement of voltage ratio and checking of voltage vector relationship.

Measurement of impedance voltage/ short circuit impedance (principal

tapping) and load loss.

Measurement of no-load loss and current.


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Measurement of insulation resistance.

Dielectric tests.

Tests on OLTC as per IS: 2026.

Operation test after the tap changer is fully assembled on the transformer.

Auxiliary circuits insulation test – after the tap changer is assembled on the

transformer, a power frequency test shall be conducted on the auxiliary circuits.

iv. Additional Routine Tests

The following additional routine tests on each of the transformer shall be conducted. No load loss and excitation current at 415V from LV side and at 90% and

110% rated voltage.

Oil leakage test – 12 hours.

Magnetic balance test

Measurement of tan delta and capacitance of each winding.

Measurement of zero sequence impedance.

All Tests as mentioned above and any other tests as required by the relevant codes and standards and as deemed necessary is to be conducted by the bidder. Bidder shall furnish his proposed QAP along with his bid for Purchaser’s review.

9.0 DRAWINGS / DATA / DOCUMENTS TO BE SUBMITTED BY BIDDER

ALONGWITH THE BID

a) As a minimum, the bidder shall furnish the following relevant drawings, documents and catalogues of the transformers offered in requisite sets failing which the bids shall be rejected.


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i) Typical general arrangement drawing of the transformer showing disposition of radiator banks, marshalling boxes, HV & LV terminal arrangements and overall dimensions.

ii) Overall dimensional physical layout drawing of the transformer. iii) Equipment weight iv) Foundation plan and mounting information with loading and transformer

anchoring details.

v) Total tank and cooling equipment oil volume

vi) Shipping weight and dimensions

vii) Transformer cooling arrangement along with Control scheme for cooler control unit.

viii) Compensating CT / Bushing CT wiring diagram

ix) Quality assurance plan

x) Type test reports of identical transformers

xi) Catalogues for transformer and fittings & accessories (preferably in

electronic form)

xii) Experience certificates of supply of identical types of transformers.

xiii) Curve for Maximum Continuous Output vs. Ambient Temperature (13oC to 50oC)

xiv) Performance curves for auxiliary consumption (cooler consumption) with

respect to ambient temperature and MVA loading.

xv) Performance curves for total losses vs. ambient temperature and MVA loading at 0.85 pf.

xvi) GA drawing of the transformer indicating the scope of supplies and

dimensions.


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xvii) Terminal arrangement LV and HV side including termination arrangement

for Isolated Phase Bus Duct / segregated phase bus duct including flange details.

xviii) List of sub-vendors for purchaser’s approval.

xix) Confirmed transformer technical particulars data sheet

9.1 DRAWINGS / DATA / DOCUMENTS TO BE SUBMITTED BY

SUCCESSFUL BIDDER FOR APPROVAL AFTER AWARD OF CONTRACT

Following drawings / documents are required to be submitted after placement of LOI for Purchaser and Owner’s approval and distribution in requisite sets as stated in General Conditions of Contract:

Sl. No.

Drawings / Documents

1 GA drawing showing weight centres of gravity both empty and full of oil, physical dimensions, plan and elevation views, disposition of cooler banks, HV & LV terminal arrangements, marshalling boxes and various fittings.

Foundation plan with loading and transformer anchoring details 2 Transformer Cooling arrangement along with control scheme for cooler

control unit. 3 Bushing CT wiring diagram 4 Type Test reports of identical transformers 5 Catalogues for transformers accessories (preferably in electronic form) 6 Curve for Maximum Continuous Output v/s Ambient Temperature (13

Deg C to 50 Deg C) 7 Performance curves for auxiliary consumption (cooler consumption) with

respect to ambient temperature and MVA loading. 8 Confirmed performance curves for total losses V/s Ambient temperature

and MVA loading at 0.85 pf. 9 Terminal arrangement LV and HV side including termination

arrangement for isolated phase bus duct including flange details 10 Confirmed transformer technical particulars data sheet 11 Rating and terminal diagram plate drawing 12 Dimension drawings of HV & LV terminations


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Sl. No.

Drawings / Documents

13 Drawings of major components like bushings, CTs, radiator banks, Buchholz relay etc.

14 Drawings of HV bushings, LV bushings and Neutral bushings 15 Marshalling box connection diagram and layout of instruments 16 Control schematics and wiring diagrams for cooler control panel along with

Write-up on Controls and Interlocks provided 17 Valve location plate for the oil forced cooling circuit indicating clearly all

the details required for each components used for the purpose 18 Electronic copy of all the final drawings submitted, in a floppy disc / CD 19 Operation and Maintenance Manual 20 Erection and commissioning manual 23 Start-up and shutdown procedure 24 Instruction for pre-commissioning check up, operation, abnormal

conditions, maintenance, repair and protection 26 Recommended inspection points and period of inspection 27 Schedule of preventive maintenance 28 Replaceable parts list with ordering information 29 Recommendation for type of lubricants, lubrication points, frequency of

lubrication and lubrication changing schedule In addition, the supplier shall supply comprehensive part list, spares & tools list, supplemented by all drawings and catalogues of transformer and its fittings & accessories.

10.0 TRANSPORTATION AND HANDLING OF MATERIAL AND EQUIPMENT

The major components shall be delivered to site as a single piece and minor components removed for shipping. Where this is not possible, individual modules shall be delivered as to require only a minimum amount of site assembly. In the last case the Bidder shall include with his proposal detail of how unit will be broken down and estimates of the man-hours and equipment required at site. Project information shall be legibly punched on the components. Normally transformers will be delivered without oil, filled with inert gas and without bushings and externally mounted accessories as applicable.


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Care shall be taken during handling of insulation oil to prevent ingress of moisture or foreign matter. In the testing, circulating, filtering or otherwise handling of oil, rubber hoses shall not be used. Circulation and filtering of oil, heating of oil by regulated short circuit current during drying runs and sampling and testing of oil shall be in accordance with the Manufacturer’s instructions and Code of Practice as per IS 10028 (i) Packing Bidder shall adequately prepare all the equipment for shipment. Where required by the nature of the equipment, Bidder shall furnish and install necessary covers to protect the equipment from rain, hail, wind, dust, etc. Equipment shall be adequately sealed and protected during shipment to prevent corrosion, entrance of foreign matter, and possible damage from rough handling during transit. Any articles or materials that might otherwise be lost in shipping shall be boxed or wired in bundles. Suitable weather protection (like PVC sheets) shall be provided to prevent wetting of components during transportation and outdoor storage at site. (ii) Protective Coatings and Preservatives Preservative coatings used on components shall be suitable for the conditions normally expected during transportation, storage and throughout the erection period. Each type of preservative used shall be identified as to quality, life expectancy and type. Toxic and hazardous - type preservatives will not be allowed. Complete information shall be submitted to the Purchaser (L&T)/Consultant covering step - by - step procedures, including Indian governing laws for handling and removal of each type of preservative. This information shall be submitted one (1) month prior to delivery. (iii) Marking

All loose components shall be identified with company material code, part no., weight and name for easy site identification. Bill of loading / shipping list shall be provided prior to equipment dispatch. Each truck / separately despatched items shall have a packing list giving details of the items supplied incloding number of containers. A comprehensive list of all items shipped shall also be submitted before despatch to purchaser. A shipping list should be sent along with each consignment with the despatch documents.


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10.1 Transportation

a) All equipment shall be adequately prepared for transportation and for a maximum period of outdoor storage of six months. At time of shipment, transformer shall be clean and properly protected against transit damages.

b) The equipment shall be prepared for transportation after testing has been

completed. Lifting points shall be clearly marked and all openings shall be tightly and effectively closed. Covers, screwed openings closed with steel plugs, shall protect flanges and weld ends shall have plastic covers.

c) Before the equipment is shipped, the original shipping stops, bolts, ties, etc.,

shall be reinstalled in all devices. d) Electrical and control panels shall be protected against corrosion, weather, and

mechanical damage during transit. Temporary structural bracing shall be installed as required to allow for normal field handling, skidding, and hoisting.

e) In addition to the foregoing, the Supplier shall provide internal and external

protection from the effects of corrosion for all parts not otherwise coated or painted. Where closure is incomplete, plastic material adequately supported, protected, and sealed shall be used to fabricate an effective barrier.

f) Equipment that is liquid leak tested in the shop by the Supplier shall be

completely drained prior to shipment. When such drainage requires the removal of plugs, drain valves, or other parts, supplier shall reinsert or reassemble these parts prior to shipment. The supplier shall despatch the transformer nitrogen filled with Automatic gas filling device & pressure monitoring device. Necessary arrangement shall be ensured by the supplier to take care of pressure drop of nitrogen during transit and storage till completion of oil filling during erection. A gas pressure-testing valve with necessary pressure gauge and adopter valve shall be provided.

g) The Bidder shall furnish all instructions for proper care and handling after

delivery, including outdoor storage procedures, before the equipment is shipped to the job site.


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11.0 FITTINGS AND ACCESSORIES Each transformer shall be equipped with fittings and accessories as listed below. The

accessories that are necessary for successful operation but not listed below shall also

be included in the scope of supply.

1. Oil conservator for the oil tank with filler cap, drain valve, magnetic oil gauge

and plain oil level gauge, conservator for oil tank with filler cap, drain valve;

magnetic oil gauge and plain oil level gauge (rubber bellows filled with air and

installed within the conservator).

2. Air release plugs for radiator banks and main tank.

3. Pressure relief devices as required - spring loaded with alarm & trip contacts

4. Double float Buchholz relay (with testing facility) with gas release cock, shut-off

valve on both sides and separate set of contacts for alarm and trip. The Buchholz

relay shall be provided with rain hood (canopy) to prevent ingress of rainwater in

its terminal box. The gas collection box and gas release cock shall be brought

down to around 1.2 m from ground level by providing copper tubing of suitable

diameter.

5. Neutral bushing for earthing with post insulator mounted on tank.

6. Bushing CTs.

7. Dial type winding temperature indicator with maximum reading pointer and four

sets of electrically separate contacts for alarm and trip.

8. Dial type oil temperature indicator with maximum reading pointer and two sets of

electrically separate contacts for alarm and trip.

9. Transducers for remote signalling of WTI/OTI (4-20mA output)

10. For oil tank conservator diaphragm type oil preservation and Silica gel breather

with oil seal.

11. Valves:

i) Drain valve with plug & pad locking arrangement


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ii) Sampling valves at top and bottom of main tank

iii) Radiator isolation valves

iv) Filter valve with threaded adopter at the top and bottom.

12. Weatherproof marshalling box for housing control equipment and terminal

connection.

13. Off circuit, hand-operated tap changer mechanism with proximity switches and

associated accessories for each tap position.

14. Cooling accessories: Requisite no. of radiators, cooling fans oil pump and oil

flow indicator with alarm contacts, shut-off valves, oil filtering valves at top and

bottom, drain valve, air release plugs etc.

15. Rating and terminal marking plate

16. Jacking pads (minimum 4 nos.), haulage & lifting lugs and lifting eyebolts.

17. Foundation bolts and nuts.

18. Inspection covers for various items e.g. bushings, current transformers, windings,

earth connections etc.

19. Rollers - Flanged bi-directional type with locking and bolting device.

20. Two (2) grounding pads each for main tank in opposite sides, transformer

marshalling box, cooler banks, etc.

21. Ladder for accessing the top of the transformer with a lockable hinged plate at the

bottom about 1.5 m from ground.

22. Danger board written in Hindi, Telugu & English.


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SECTION-II

TECHNICAL DATASHEET

Ratings and requirements for GTG and STG Transformer

Sr. No

Item GTG transformer

STG transformer

MVA Rating

a) With OFAF cooling 275 170

b) With ONAF cooling 220

136

1.

c) With ONAN cooling 165

102

2. GTG Transformer OFAF At 15 Deg C By Bidder At 29 Deg C By Bidder

At 43 Deg C By Bidder

3. Qty. Two (2) Two (2) 4. Applicable Standards IS 2026 IS 2026 5. Frequency 50 Hz 50 Hz 6. Voltage Ratio 15.75/420 kV 15.75/420 kV

7. System earthing

(I) HV side Solidly earthed Solidly earthed (ii) LV side Non-effectively earthed Non-effectively earthed 8. System fault level

(i ) HV side 40 kA (rms) / 1 sec 40 kA (rms) / 1 sec 9. (ii) LV side Later Later

10. Normal operating voltage

range on 400 kV side

(+) 10 % to (-) 10 % (+) 10 % to (-) 10 %


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Sr. No


STG transformer

11. Rated Current

a) HV Windings (A) By bidder By bidder b) LV Windings (A) By bidder By bidder

12. Service / Duty/ Type/Oil Outdoor / continuous / bi-

directional/ Mineral Oil

Outdoor / continuous /

bi-directional/ Mineral

Oil 13. Type of cooling ONAN/ONAF/OFAF ONAN/ONAF/OFAF 14. No. of cooler banks x

capacity 2 x 100 % 2 x 100 %

15. Each Cooling Unit is provided with

a) Make of Motor By bidder By bidder

b) No x kW rating of Fan Motor

By bidder By bidder

c) No x kW rating of Oil Pump

By bidder By bidder

d) d) Automatic operation of Cooling Fan / Pumps provided (Yes / No)

Yes Yes

16. Winding connection (i) HV Side

(ii) LV Side

Star

Delta

Star

Delta 17. Vector Group YNd1 YNd1 18. Termination

(i) HV side Aluminium ACSR

Aluminium ACSR

(ii) LV side Isolated phase busduct Isolated phase busduct


L&T - S&L LIMITED



Rev : R0 Date : 16/9/2009


Sr. No


STG transformer

(iii) HV Neutral Two (2) nos. tinned copper flats shall be provided upto the base of main tank supported on pin insulators.

Two (2) nos. tinned copper flats shall be provided up to the base of main tank supported on pin insulators.

19. Type of Insulation of

winding

Cellulose Based /Class A Cellulose Based /Class A

20. Tap changer (i) Type On Load Tap Changer On Load Tap Changer (ii) Voltage range

+7.5% to -15% in steps of

1.25%

+7.5% to -15% in steps

of 1.25% 21. Category of voltage

variation

CFVV CFVV

22. Guaranteed positive

sequence Impedance at 75

Deg C with 100% loading

a) principal tap

12.5% 12.5%

b) Maximum Tap By Bidder By Bidder

c) Minimum Tap By Bidder By Bidder

23. Zero Sequence Impedance

at 75 Deg C

By Bidder By Bidder

24. X/R ratio of Generator

Transformer

By Bidder By Bidder

25. Winding Resistance

a) HV Winding By Bidder By Bidder

b) LV Winding By Bidder By Bidder


L&T - S&L LIMITED



Rev : R0 Date : 16/9/2009


Sr. No


STG transformer

26. Maximum Flux Density at

any part of Core / Yoke at

rated MVA and 10% over

voltage condition Wb/m2

26. No Load HV Current as

%age of FLC

By bidder By Bidder

At 90% rated voltage By Bidder By Bidder



27.

Maximum temperature rise

of top oil at 100% of full

load (measured by

thermometer)

50C

50C

28. Maximum temperature rise of winding at 100% of full load for 24 hours (measured as per IS-2026)

55C 55C

29. Winding hot spot

temperature

By Bidder By Bidder

30. Rated power frequency withstand voltage for bushing

( i ) HV side 630 kV (rms) 630 kV (rms) ( ii ) LV side 50 kV (rms) 50 kV (rms) (iii) HV Neutral 38 kV (rms) 38 kV (rms)

31. Rated lightning withstand voltage for bushing (1.2 / 50 microsecond) Impulse


L&T - S&L LIMITED



Rev : R0 Date : 16/9/2009


Sr. No


STG transformer

( i ) HV side 1425 kV (Peak) 1425 kV (Peak) ( ii ) LV side 125 kV (Peak) 125 kV (Peak) (iii) LV Neutral 95 kV (rms) 95 kV (rms)

32. Rated power frequency withstand voltage for winding

( i ) HV side 630 kV (rms) 630 kV (rms) ( ii ) LV side 50 kV (rms) 50 kV (rms) (iii) HV Neutral 38 kV (Peak) 38 kV (Peak)

33. Rated lightning withstand voltage for winding

( i ) HV side 1425 kV (Peak) 1425 kV (Peak) ( ii ) LV side 125 kV (Peak) 125 kV (Peak) (iii) LV Neutral 95 kV (rms) 95 kV (rms)

34. Over fluxing withstand time

a) For over fluxing factor 1.10 Continuous Continuous

b) Over fluxing factor 1.25 60 s 60 s

c) For over fluxing factor 1.40 5 s 5 s

35. Minimum creepage distance

20 mm / kV for HV and LV bushings

20 mm / kV for HV and LV bushings

36. Minimum clearances in air

Phase to phase (mm)

Phase to earth (mm)

Phase to phase (mm)

Phase to earth (mm)

(i) HV Side / HV (n)

4000 3500/320 4000 3500/320

(ii) LV Side As per CBIP/IS


L&T - S&L LIMITED



Rev : R0 Date : 16/9/2009


Sr. No


STG transformer

37. Short circuit withstand time without injury due to terminal fault with rated voltage maintained on the other side. (i) With 3 phase dead short circuit (ii) With single phase short circuit

3 sec

3 sec

3 sec

3 sec

38. Noise level Average sound level value 85db at the distance of 1.0 meter

Average sound level value 85db at the distance of 1.0 meter

39. Finishing paint type Epoxy paint Epoxy paint

40. Paint shade RAL 7032

41. a) Rated voltage of Bushings (kV)

HV LV Neutral

420 24 36

b) Manufacturer By Bidder By Bidder

c) Bushing Type HV - OIP Condenser LV - Porcelain, Oil filled

HVN - Porcelain, Oil communicating

HV - OIP Condenser LV - Porcelain, Oil filled HVN - Porcelain, Oil communicating

Reference standard IS: 2099 IS: 2099

HV Neutral Bushing CT a) Core-1 : For Restricted earth fault protection (64GT)

5P20

5P20

42.

b) HV Neutral Bushing CT Core-2 : Standby earth fault protection (51NGT)

5P20 5P20


L&T - S&L LIMITED



Rev : R0 Date : 16/9/2009


Sr. No


STG transformer

43. HV bushing CT a) Core-1: Restricted earth fault protection (64GT) b) Core-2: For other transformer protections

Class PS,

Class PS

44. LV side CT for Differential protection (87)

Class PS Class PS

45. Guaranteed losses at rated voltage and frequency on principal tap at full load at 75 deg.C

Copper Losses (kW) By Bidder By Bidder

Iron Losses (kW) By Bidder By Bidder

Cooler Losses (kW) By Bidder By Bidder

Sub-Total (kW max) By Bidder By Bidder

46. Efficiency at 75 deg.C and 0.8 p.f. Lag

By Bidder By Bidder

a) At 100% load By Bidder By Bidder

b) At 75% load By Bidder By Bidder

c) Maximum efficiency By Bidder By Bidder

d) Load and p.f. at which it occurs

By Bidder By Bidder


L&T - S&L LIMITED



Rev : R0 Date : 16/9/2009


Sr. No


STG transformer

47. Voltage regulation at full load, at 75 deg. C

a) At 0.90 p.f. Lag By Bidder By Bidder

b) At 0.85 p.f. Lag By Bidder By Bidder

48. a) No load current at rated voltage and rated frequency (A)

By Bidder By Bidder

b) Magnetizing inrush current as percentage of full load current (A)

By Bidder By Bidder

49. Transformer oil preservation system

a) Main conservator Conservator with aircell and silica gel breather

Conservator with aircell and silica gel breather

b) Oil drain valve

Type By Bidder By Bidder

Size By Bidder By Bidder

c) Size of oil sampling valve By Bidder By Bidder

d) Size of gas sampling valve By Bidder By Bidder

e) Total volume of conservator By Bidder By Bidder

50. Gas Detection Device (Buchholz)

a) Manufacturer By Bidder By Bidder


L&T - S&L LIMITED



Rev : R0 Date : 16/9/2009


Sr. No


STG transformer

b) Type By Bidder By Bidder

51. Fault Pressure Device


b) Type By Bidder By Bidder

c) Numbers provided By Bidder By Bidder

d) Operating pressure By Bidder By Bidder

52. Winding

a) Type of winding By Bidder By Bidder

b) Current density at rated load for HV winding

By Bidder By Bidder

c) Current density at rated load for LV winding

By Bidder By Bidder

53. Winding Temperature Indicator


b) Model Number By Bidder By Bidder

c) Accuracy By Bidder By Bidder


L&T - S&L LIMITED



Rev : R0 Date : 16/9/2009


Sr. No


STG transformer

54. Oil Temperature Indicator


b) Model Number By Bidder By Bidder

c) Accuracy By Bidder By Bidder

55. Approximate weights: With oil filled up to transport level

a) Core and windings By Bidder By Bidder

b) Tank and fittings By Bidder By Bidder

c) Oil By Bidder By Bidder

d) Total weight By Bidder By Bidder

56. Transformer core details

a) Net core area By Bidder By Bidder

b) Core material and grade used

By Bidder By Bidder

c) Thickness of stamping By Bidder By Bidder

57. Approximate weights: Without oil and filled with nitrogen gas

a) Core and windings By Bidder By Bidder


L&T - S&L LIMITED



Rev : R0 Date : 16/9/2009


Sr. No


STG transformer

b) Tank and fittings By Bidder By Bidder

c) Total weight (with nitrogen filled)

By Bidder By Bidder

58. Shipping Data

a) Weight of the heaviest package

By Bidder By Bidder

b) Dimension of the largest package (LxBxH)

By Bidder By Bidder

59. Curve showing variation of Transformer MVA output vs. ambient temperature superimposed on GT curve furnished (Yes/No)

Yes Yes

Type test certificates furnished (Yes/No)

Yes Yes

GA drawing furnished (Yes/No)

Yes Yes


L&T - S&L LIMITED



Rev : R0 Date : 16/9/2009


SECTION-III

TECHNICAL DATASHEET FOR COOLING PUMP/FAN MOTORS

Sl. No.

Description Units Particulars

1. a) Degree of protection (service outdoor)

IP55

2. Method of Cooling TEFC

3. Method of starting DOL

4. Duty Cycle

5. Supply Voltage 415 V AC

6. Phase 3Ph

7. Frequency 50 Hz

8. Class of insulation Class F

9. Temperature rise Class B

10. % Voltage variation & % Frequency variation

+/-10% & +/-5%

11. Combined voltage and Frequency variation

10% (abs)

12. System earthing Effectively earthed

13. Starting current at rated voltage including IS tolerance

<600%

14. Fault withstand capacity of terminal box

50 kA for 0.25 Sec

15. Number of Grounding pads i) Motor body ii) Terminal boxes

By bidder

16. Paint type and shade RAL 7032