transformer pc test

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Part I

Power Transformer


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Contents

Section I GENERAL

1. Basic working principle of Transformer

2. Selection of transformer

3. Major Parts and accessories

4. Major Supplier

5. aw Material used

!. ele"ant B#S

$. %ompliance wit& #ndian electricit' rules(. #nspection and testing at manufacturer works

Section II TRANSPORTATION AND STORAGE

1. Transportation

2. )*ternal #nspection +Before unloading,

3. -nloading at site

4. ssem/l' of 0&eels

5. Storage

Section III ERECTION

1. eneral

2. #nternal inspection

3. ssem/ling of accessories

4. Preparation of insulating oil +ualit' and treatment,

5. il filling

!. Pressure testing of transformer

$. ot il %irculation

Section IV COMMISSIONING

1. Pre commissioning c&ecks

2. Pre commissioning test3. inal # c&eck

4. inal c&eck prior to commissioning

5. )nergi6ing


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!. %&eck immediatel' after commissioning


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Section I

GENERAL

1. Basic working principle of Transformer

A transformer is a static piece of apparatus used for transferring power from one circuitto another without change in frequency. It can raise or lower the voltage with acorresponding decrease or increase in current. In its simplest form, a transformerconsists of two conducting coils having a mutual inductance. The primary is thewinding which receives electric power, and the secondary is the one which may deliverit. The coils are wound on a laminated core of magnetic material.

The physical basis of a transformer is mutual inductance between two circuits linkedby a common magnetic flux through a path of low reluctance.

The two coils possess high mutual inductance. If one coil is connected to a source ofalternating voltage, an alternating flux is set up in the laminated core, most of which islinked up with other coil in which it produces mutually induced emf ( electromotiveforce according to

!araday"s laws electromagnetic induction, i.e. #$ % (di&dt

'here, e $ induced emf % $ mutual inductance

If the second circuit is closed, a current flows in it and so electric energy is transferred(entirely magnetically from the first coil (primary winding to the second coil(secondary winding.

2. Selection of transformer

epending upon the system design, T) has adopted power transformer as perfollowing specification in its various substations

*oltage +atio apacity 'inding&onnection *oltage+egulation

--& k* / %*A Two winding 0n load

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//& k*

334&//5--& k*

334&//5--& k*644&334&-- k*

34 %*A34 %*A

-724&- %*A

44 %*A-2 %*A

Two winding

Three winding

Three windingAuto onnection

0n load

0n load

0n load0n load

T) has adopted policy to procure the new power transformer with built in 8itrogenin9ection fire extinguishing system and similarly existing transformer of T) substationwill also be fitted with same extinguishing system.

3. a!or "arts an# accessories

%ain tank, ore, 'inding, Tap changer, riving mechanism, :ushing, +adiator,;eader, %ain onservator, Air ell, Tap changer, conservator, Turret with T,:reather, 1+*, relay, 0il


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I< 343/ (1art 6 BCC 1ower transformers 1art 6 Terminal %arking,tapping and connection (!irst revision

I< 343/(1art 2 BB2 1ower transformers 1art 2 Terminal& +eactor bushingsminimum external clearance in air specification

I< 443D (1art BD2 ode of practice for selection, installation andmaintenance of transformers 1art selection

I< 443D (1art 3BD ode of practice for selection, installation andmaintenance of transformers 1art 3 Installation(superseding I


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transformer. The excess oil should be laid through two or more hume &concrete pipes(minimum 24 mm diameter from bottom of pit to a central remote burnt oil pit.

ontrol cables emanating from transformer shall be passed through hume pipes laid inthe soak pit. The marshalling kiosk of the transformer shall be installed outside the pit

Barrier etween transformer

:arriers & fire wall of brick or reinforced cement concrete shall be provided forseparation of transformer whenever adequate place is not available. The barrier shallextend at least -44 mm above highest transformer bushing and pressure release vent andlengthwise /44 mm beyond the transformer including any radiator and tap changer

enclosure

A summary of fire protection and fighting system for indoor and outdoor transformersrecommended by :I1 and being adopted by various power utilities is given below

e (each 8umber Transformer protection

(a under 4 %*A

(b 4 to 44 %*A

(c Above 44 %*A

0ne or more

0ne only

%ore than one

0ne only

%ore than one

;ydrant protection

;ydrant protection with water spray

equipment

. 1rovide a C.2 m clearance betweenunits and /4 mm hose with portablespray no>>les or3. %asonry barrier between units with/4 mm hose with portable sprayno>>les

or

-. !ixed automatic water spray withseparate piping for each unit

;ydrant protection with water sprayequipment

. !ixed automatic water spray(emulsifier with separate piping foreach unit

and

3. 1rovide a C.2 m clearanceor

masonry barrier between units

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(d Above 344 %*A 0ne only

%ore than one

;ydrant protection with water spray

equipment

. !ixed automatic water spray withseparate piping for each unit

and3. 1rovide 2 m clearance

or masonry barrier between units

4. Inspection an# testing at man%fact%rer works

uring process of manufacturing, inspection F testing are carried out at various stagesand final routine test at works before dispatch for ensuring quality product.

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Section II

TRANS"/RTATI/N AN5 ST/RAGE

1.6 Transportation

epending upon the weight&height restrictions and&or other considerations, 1owerTransformers are transported either filled with oil or nitrogen.

)arge 0il filled Transformers are transported filled with dry 8itrogen, due to weightlimitations, at a positive pressure of 4.C2 kg&cmG to protect the active parts againstmoisture .The internal gas pressure at the time of shipment is painted on the tank.

e Transformers are transported filled with oil such that about 4H of the tankvolume is left clear for oil expansion to limit the excess internal air pressure to 4.-2 kg&cmG.All openings resulting from the removal of fittings for shipment are sealed with suitablegasketted blanking plates during transport. !ittings dismantled before transports are

packed in separate packing cases in line with shipping list.

2. E7ternal Inspection Before %nloa#ing

In connection with receiving and unloading at site, and at the final storing place before

assembling, the transformers shall be inspected carefully. #xternal visible damages asdents, paint etc. may imply that the transformer has been sub9ected to careless handlingduring transport and&or loadings, and a careful investigation is therefore 9ustified.

After the arrival of the material at receiving points, the condition of packing and of thevisible parts should be checked before unloading. rums containing oil, which have

been dispatched separately, should be examined carefully for leaks or any sign oftampering. In case of possible damage&loss of any component, the necessary claimsshould be registered with the concerned agency as per purchase order.

In order to protect the active part against moisture, the transformer tank is filled with8itrogen during transport at an over pressure of 4.C2 kg& sq. cm (3.2 psiapproximately at room temperature.

heck immediately the gas pressure at the arrival. A positive pressure indicates that thetank and the transformer components respectively are tight, and that the active partincluding the insulation materials is dry.

If there is no positive gas5pressure, transformer should be immediately filled with dry8itrogen gas at a pressure of 4.C2 kg&cmG without loss of time as per the following

procedure.

(i 1ull 244 mm mercury vacuum after blanking off all openings.

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(ii :reak the vacuum by admitting dry nitrogen through a convenient valve at thetop of the tank and drain the oil completely.

(iii ontinue to supply nitrogen until it maintains a steady pressure of 4.C2 4.43kg&cmG above the atmosphere.(iv 1ressure of nitrogen gas shall be maintained at 4.C2 4.43 kg&cmG at same

reference temperature.(v 1ressure would be monitored by taking three readings within 36 hours to ensure

that there is no leakage of gas.(vi


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%ounting of wheels under transformer is to be done as per roller arrangement drawingsupplied by 0#%. It should be ensured that wheel shafts are well greased and rotate

freely. 'hile fixing the roller, flange should come on inner side of rails after placing thetransformer in the correct position. Transformer wheels must be locked for arresting themovement of transformer

&. Storage

&.1.1 ain Tank*

If the storage time is expected to exceed - months, the transformer should be providedwith oil conservator including oil5level indicator and breather and to be filled with oil as

per procedure laid down in the installation.

'herever possible it would be most desirable to keep the transformer energi>ed even ata low voltage so that its temperature is higher than the ambient temperature. The lowvoltage may be applied under open circuit or short circuit conditions. It may beascertained whether partial cooling is required in such a case. The oil quality should also

be periodically monitored. If for some reason, oil filling cannot be carried out after astorage period longer than - months, the nitrogen pressure shall be maintained andsupervised carefully. If the storage time without oil exceeds D months 0#% should beconsulted about measures to be taken. If required ew point of nitrogen to be measured.

&.1.2 5ew point meas%rement

ew point is the temperature at witch water vapors present in the gas begin to condense.If gas pressure of nitrogen was not possible to maintain during storage period there isevery possibility to absorb the moisture in transformer active part&insulation. In suchcases, to check the dryness of insulation, dew point measurement is carried out at site inconsultation with 0#% before starting the erection.

!or transformer of gas pressure of 4.- psi, the acceptable limit of dew point asrecommended by :I1 shall be as under

Temperature ofinsulation in J!

%aximumpermissible dewpoint in J!

Temperature ofinsulation in J

%aximumpermissible dewpoint in J

4 5CD 5C.CC 5/.

2 5C6 52.44 52D.DD

4 5C4 53.33 52/.//

2 5// 5B.66 526.66

34 5/3 5/.// 523.3332 52D 5-.-- 56B.BB

-4 52- 5. 56C.33

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-2 56D K.// 566.66

64 566 K6.66 563.33

62 564 KC.66 5-B.-B24 5-2 KB.BB 5-C.33

22 5- K3.CC 5-6.BB

/4 53C K2.22 5-3.CC

/2 533 KD.-- 53B.BB

C4 5D K3-. 53C.CC

C2 56 K3-.DD 532.22

D4 54 K3/.// 53-.--

D2 5/ K3B.66 53.

B4 5 K-3.33 5D.--

B2 K- K-6.BB 5/.44 KC K-C.C2 5-.DD

4 K/ K6-.-- 5D.DD

34 K32 K6D.DD 5-.DD

-4 K-- K26.66 K4.22

64 K66 K2B.BB K2.22

&.2 Accessories*

Accessories are packed to protect against normal handling and transport stresses. Theinstructions for lifting given on the packages must be complied to avoid damages.

2.3.


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(iii ontal position.

Section III 1age 4 of 2/


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ERE,TI/N

1. General

#rection of transformer is divided in following section

(i =eneral(ii Internal inspection(iii Assembling of accessories(iv 1reparation of insulating oil(v 0il filling(vi 1ressure testing

(vii ;ot oil circulation in the transformer

As transformer tank is filled with nitrogen to protect from possibility of absorbtion ofmoisture in the active parts during transportation and storage,. minimum possible timeshould be taken between opening of the inspection plate and filling of oil to avoid theabsorption of moisture. To achieve this, erection work of radiator and conservator shall

be completed before opening the main tank. 1reparation of oil should be taken inadvance so that transformer oil is ready by the time assembly of accessories arecompleted.

:efore taking up assembling of accessories, following items should be available at site

(i rane of suitable capacity(ii ;igh5vacuum two5stage oil filtration plant provided with thermostat controlled

oil heaters and vacuum5proof hoses with independent vacuum pumping systemfor tank evacuation. apacity /444 lph.

(iii 0il5storage tanks provided with silica5gel breathers and inlet&outlet valves for oilcirculation. +ecommended capacity 34 k) 5-4 k)

(iv *acuum gauges provided in filtration plant.(v #quipment for measurement of electric strength (:* of oil5 44 k* set.

(vi #quipment for measurement of moisture content of oil.(vii #quipment for measurement of resistivity and Tan delta at B4J .(viii 0il5sampling bottles.(ix Transparent vacuum5proof tubes for checking of oil5level during oil filling.(x *alves, fittings, gaskets etc.(xi ry nitrogen cylinders.

2. Internal inspection

:efore starting assembling of accessories on tank, the transformer must be internally

inspected. :efore opening the inspection plate the following precaution are to be taken

(i heck that there is no over pressure in the transformer when blanking plates orconnection lids are to be opened.

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(ii All loose ob9ects, tools, screws, nuts etc. shall be removed from the transformercover before opening the connection and blanking lids.

(iii All loose ob9ects (tools, pencils, spectacles etc., shall be removed from theboiler5suit (dangri pockets etc. before starting the work through manholes.(iv Tools to be used inside the transformer 5e.g. for tightening of screw59oints5 shall

be fastened to the wrist or another fixed point by means of cotton tape or string.(v Tools with loose sleeves and tools with catches must not be used at work inside

the transformer.(vi =reatest possible cleanliness shall be observed at work inside the

transformer&reactor, and at handling of parts to be mounted inside thetransformer.

(vii !ibrous cleaning material should not be used as it can detoreate oil when mixed

with it.(viii The active part (core and winding should be exposed to the surrounding air foras short time as possible. Therefore, only one blanking plate or connection lidshall be opened at a time for remounting of bushings, valves etc.

(ix


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#arthing onnections from core and top yoke clamp.(fig.3

8ote(i 'hile disconnecting&earthing connection between core&yoke clamp F tank,

remove the link.(ii 'hile putting in service place links in position.

3. Assemling of accessories

To avoid any confusion and repetition of work assembling of accessories must be

carried out by referring the part list and transformer 0=A supplied by manufactureralong with 0#% manual. Identify each accessories referring part list number given in0=A with number marked on each accessories.

3.1 5%ring process of assemling following preca%tion are to e taken

(i !ire5fighting equipment shall be available at the oil5treatment equipment as wellas at work on and ad9acent to the transformer .

(ii 'elding work on or ad9acent to the transformer shall be avoided.(iii


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3.3 T%rrets

Turrets are cylindrical shaped metallic part mounted on top plate of the transformerused as housing of the ;* and )* condenser bushings. P phase turret of ;* and )*are internally mounted with T, used for measuring for winding temperature. %ountthe respective turrets in correct position by aligning the punching mark given in turretand transformer tank

3.$ B%s-ings

!or // k* and above voltage level, oil impregnated paper (0I1 condenser bushings are

generally used

3.$.1 5esign an# ,onstr%ction

The general constructional details of 334 k* 0I1 condenser bushing are shown in figure

The active part of the bushing consists of an 0il Impregnated 1aper (0I1 condensercore (3 manufactured from superior grade ?raft 1aper wound on a metal tube. The

bushing is voltage graded by suitably interposed aluminum foils forming condenserlayers. Thus, the electrical stresses are controlled through out the thickness and along

the surface avoiding any highly concentrated >ones.

The ondenser core (3 is assembled with a central mounting flange (/ and porcelaininsulator ( -,3- at both outdoor and oil immersed. #nd 9oints are made leak proof bymeans of gaskets and the complete assembly is held tight by means of a powerful spring

pack located in the top cap (33. This top cap also serves as an in built oil conservatorto cater for oil expansion and has an oil level indicator (.

The bushing is vacuum dried and impregnated with high grade degassed and dehydratedtransformer oil under a carefully controlled and monitored process .

relay.

(iii +ating plate (36 giving the rating and identification details of the bushing.(iv


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last condenser foil within the bushing during normal service This taping iselectrically connected to the mounting flange (/ through a self grounding

arrangement. The test tap must always be kept protected with its cover screwedproperly.

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The conservator, which may be with or without air cell is assembled either on thetransformer, or on a separate frame.

3.(.1 ,onstr%ctional feat%re of conser)ator wit- air cell

In all transformers especially in high voltage class, maintenance of insulating oil notablyits dielectric property forms one of the determining factors of reliability of equipment inservice. 0xidation and contamination of transformers oil can be avoided in a simple andeffective way by use of above oil preservation system. The complete system is known asQonservator with Air ellQ.

In this oil preservation system a flexible air cell made of oil resistant nitrile rubber is

placed inside the conservator and floats on the oil surface. The air cell inflates ordeflates as the oil level in the conservator falls or rises depending on the ambienttemperature and load on the transformerRR. The inside of the rubber bag (Air ell is putinto communication with atmosphere by means of a silica gel breather which ensuresdry atmosphere inside the air cell. In addition to the above this system providesfollowing advantages.

(i It avoids saturation of absorbed gases.(ii As no gas is used in this system, which operates at constant pressure, this

formation of gas bubbles at low ambient temperature and load is eliminated. The

system thus preserves the oil quality particularly its dielectric properties.

The conservator with air cell is provided with a magnetic oil gauge having one electricalcontact. The indication shown on the dial physically corresponds to the oil level in theconservator which is due to balance of static pressure between the oil of the conservatorand the atmospheric air inside the air cell. This system is also provided sometimes witha set of pressure and vacuum valves. These valves operate to pass either oil or air in theevent of over filling or under filling the conservator during installation.

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3.(.2 /peration of conser)ator air cell

The oil connection between conservator and transformer tank is made through :uchhol>relay and valves are provided in between.

The flexible air cell is connected to the top of the conservator through gasketted 9oint.@nder normal condition air cell is completely surrounded by oil and floats in theconservator. The air cell inflates&deflates as the oil volume changes. The float of the%0= which is always in contact with bottom side of the air cell, moves up and downand indicates the oil level. The air cell will sink in the remote event if it is damaged and%0= alarm will operate. The conservator then functions as a conventional conservator

without effecting the performance of the transformers.

3.(.3 Installation of oil conser)ator

=enerally oil conservator of transformer 44 %*A and above are supplied with air cellassembled. %ount and check the function of %agnetic oil gauge. ;ealthiness of air cellfor any leakage must be checked and inflate the air cell as per procedure laid down by0#% instruction manual before mounting on transformer. onservator should becleaned thoroughly inside.

3.+ Breat-er "ipe

%ount breather pipe as per 0=A drawing. Soint of pipe must be tighten properly toavoid any air leakage which may cause moisture entering into transformer. :reather

pipe must be supported firmly.

3.4 E0%ali>ing "ipe

All equali>ing 1ipes of turrets should be mounted according to 0=A F part list. Thepipes shall always incline - to C degrees upwards from the transformer

3.? B%c--ol> Rela

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3.?.1 "rinciple of /peration of gas operate# rela

+elay serves main protection for any minor or ma9or faults that may develop in side thetransformer, such fault allowed result in generation of the gas which causes operation ofthe mercury switch giving signal of audible alarm and isolate the transformer from thenetwork

3.?.2 ,onstr%ction

It comprises of cast housing which contained pivoted bucket, each bucket being counterbalanced by a weight. #ach assembly carries mercury switch, the leads from which aretaken to a terminal block.

3.?.3 /peration

In a healthy condition of the transformer relay is full of oil and the both the mercuryswitches are open. In the event of a minor fault like damage to the core bolt insulation,local overheating, etc, the arcing causes slow generation of gas in the oil, which passesin the pipe and gets trapped in the relay housing. As gas accumulates, oil level in therelay falls, leaving the buckets full of oil.

'hen a sufficient volume of gas is collected in the relay, the top bucket tilts because of

its extra weight due to contained oil, overcoming the balance weight which closes themercury switch and initiates an audible alarm.

'ith a ma9or fault like short circuits between turns, coils or between phases, generationof gases is rapid and gas displaced oil surges to the relay and impinges on the bafflecausing the lower assembly to tilt and close the mercury switches. This provides thesignal for tripping the circuit breaker, which disconnect the transformer from the bus

bar.

3.?.$ Installation

:efore installing functional test of the relay is to be carried out as per procedure given in0#% manual. The relay must be mounted in the pipe at an inclination of - to C degreeand arrow (shown in bucholt> towards conservator, test cock and air vent are at the topand entry of connecting lead should from bottom of the relay. :efore commissioningensure that test key of buchhol> relay remains in the


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3.16 "ress%re Relie)e ;al)e "R;

3.16.1 Application

This is a mechanical protective device used on transformer. 'hen pressure in the tankrises above predetermined set limit this valve operates and performs the followingfunctions

(i Allows the pressure to drop by instantaneously opening a port of about 24 mmdia.

(ii =ives visual indication of valve operation by rising a flag.(iii 0perates a micro switch. ;ence switch can be effectively used in control circuit.

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3.16.2 Installation

#ach valve should be cleaned from inside ( tank side with compressed air 9et. Allparticles should be removed from tank side 'hile cleaning, care should be taken that the9et does not attack the switch and the flag mechanism. The 1+* should be installedconsidering the following aspects. The indicating flag is easily seen from distance, Thevalve is accessible for manual resetting and for routine manual checking. 'hileinstalling remove dirt and clean the mounting surface, remove all traces of oil, grease.

The rubber gasket supplied with the valve should be property cleaned F re locatedproperly in the recess carefully. All the bolts should be tightened evenly so that equalpressure is exerted on basket and base. onnect control circuits to terminal plateprovided in the switch box through cable gland. As per wiring diagram check theoperation of flag and switch by lifting operating rod and confirm that both controlsoperate as required.

3.11 S%##en "ress%re Rela S"R

3.11.1 General #escription an# working

The


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equali>ing orifice, all enclosed in a sealed case and mounted on the outside of thetransformer at the gas space.

'hen an arcing internal fault in the transformer produces an abnormal rise in gaspressure, the bellows will expand, operate the %icros witch and signal the occurrence ofthe fault. The equali>ing orifice is a non corrosive plug with a very small hole, whichwill equali>e the pressures in the +elay and gas space during the slow pressurevariations associated with transformer load changes. It will throttle an abnormal increasein transformer pressure, however, and cause a signal.

3.11.2 /peration

It will operate on a sudden increase of gas pressure regardless of the operating pressure

on the transformer.

(i A pressure rise of 2.2 psi per second will operate the +elay in three to four cycleson a 24 ;ert> circuit.

(ii At high rates of rise -4 to 64 psi per second, it will operate in a half cycle.(iii It will not operate on changes in pressure due to normal transformer operation.(iv It will detect abnormal disturbances which are sufficient to operate the

conventional pressure relief device.

!igure given below shows the operating characteristics of the +elay.

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3.11.3 Installation

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3.1$ ars-alling @iosk

All temperature indicators, switches, contactors for controlling pumps and fans are fittedin marshalling kiosk. All cable from transformer accessories and +T are terminatedin marshalling kiosk. This should be installed as per lay out drawings near totransformer so that length of the capillary of 'TI F 0TI do not fall short and also tokeep sufficient space for opening of the front and rear door.

3.1& 9TI /TI temperat%re %l

These are the sensing device connected with a expansion bellow housing in 'TI atother end through capillary filled with liquid and sealed. The bulbs along with

capillaries are coiled and kept in side marshalling kiosk along with mounted 'TI.

3.1&.1 Installation

The bulbs are to be installed in the respective pocket provided on the top of transformertank after filling oil in the pocket are must be taken for not to stretch hard ,twist or

bend the capillary to a radius less then C2mm. ontinuously support the capillary bysuitable clips at intervals of -44 to 624 mm. Allow necessary slack at the bulb end formounting and removing the bulb without sharp bend at the 9oint.

3.1( T-ermo sip-on

All the transformer 44 %*A and above in T) are fitted with Thermo


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(i +egenerate the Alumina before putting into trays. Trays should be filled up todepth of -4 mm

(ii omplete the assembly as shown in 0=A drg. of the transformer.

3.1(.3 "roce#%re for regeneration of Al%mina

Alumina should be thoroughly washed in clean transformer oil and heated in a oven.It should be reactivated separately in a container and not in trays provided in the filter.The adsorbent should be fried at 64U for 3 hours or at 34U for D hours. The driedalumina must be stored in a sealed container.

It is important that transformer oil should not be poured immediately after regeneration

of Alumina which will cause charring of oil. Alumina should be allowed to cool at /4U.!ill the trays with adsorbent and (complete the tray assembly and lower this assembly incontainer immediately and commission the filter.

3.1+ Ne%tral ,T

#rect the )* and ;* neutral T and connect the bus bar to the respective ;* F )*neutral bushing as per 0=A. !lexible copper bus bar connection should be provided

between )* neutral bushing and solid earthing bus to have sufficient flexibility so thatexcessive force is not applied to bushing

3.14 ,ontrol' rela an# tap c-anger panel

Install the transformer control, relay and remote tap changer panel in control room.#nsure that all the protective relays required for transformer are provided in the panel

3.1? ,aling

omplete the cabling connecting all accessories of the transformer (%0=, 1+*, relay, oil surge relay, cooling fan, cooling pump, oil flow indicator,

riving mechanism, %arshalling kiosk with relay panel and +T panel as perschematic cable schedule.

8ote all cable should be properly ferruled, and glanded with tag identification tags

3.26 Eart-ing

(i transformer tank, marshaling box, 0)T, motor drive, radiator, supportingstructure etc should be earthed and connected to main earth mesh

(ii )* and ;* neutral T should be earthed to separate bored earthed pit and also to

be connected to main mesh. In case of -- k* neutral double earth strip must beprovided

(iii ontrol, relay and tap changer panel to be connected to earthed

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(iv Tertiary winding As per T) practice in 334&//5--& k* transformer, any onephase of tertiary winding that is k* winding is externally earthed and

connected with substation mesh. ation value (Total acidity, (%ax mg&?0;&g 4.4-

D. orrosive sulphur 8on5 corrosive

B. #lectric strength (breakdown voltage(min

(a 8ew @ntreated 0il, ?* (rms -4(If the above value isnot obtained the the oil shall befiltered in laboratory.

(b After filtration ?* (rms /4

4. ielectric dissipation !actor (tanF at

B4U (%ax

4.443

. 'ater ontent ( %ax ppm 24

3.


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at B4Uat 3C U

0hm5cm0hm5cm

-2 x 4WG244 x 4WG

-. 0xidation stabilitya 8eutrali>ation value ( %axb Total sludge after oxidation(max

mg&?0;&g 4.64.4H

6. Ageing characteristics after acceleratedageing ( open beaker method with coppercatalyst

a +esistivity ( %in at B4U at 3C X

0hm5cm0hm5cm

4.374WG3.274GG

b Tan delta at B4 Y %ax 4.3c Total acidity(%ax mg&?0;&g 4.42

d


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0il treatment shall be terminated when the following parameters are attained.

Table

k* lass of transformer +ecommended 1ermissible limit

#lectric ing pipe between main tank and diverter switch assembly should bemounted and the valve if any must be kept open

(iii *alve between the ratio chamber and main tank must be kept open.(iv 8o electrical test on the Transformer is permitted during the evacuation.

&.1 E)ac%ation

The vacuum pump may be connected to the top valve of transformer. Transformer tank(#xcluding cooler bank and conservator shall be evacuated to a pressure of .44 Torrmax, and vacuum to be maintained for the time given in table below

TABLE


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wall thickness of 25D mm, may be connected to a top and a bottom valve on thetransformer.

0il5filling in the tank is done through valve at a low level on the transformer and at amaximum rate of 652 k)&hour. 'hen the oil5level has reached about 24 mm below thecover&the vacuum pump is stopped. ontinue the oil filling level up to buchol> relay

&.3 /il :illing in #i)erter switc- asseml

0il will be automatically filled in diverter switch assemblywhen oil level in transformermain tank reach up to 0)T equali>ing pipe. ismantle equali>ing pipe and blank withelbow pipe and blanking plates supplied loose.

&.$ /il filling in cooling ank

ooling bank to be filled separately with purified and degassed oil. The oil is thencirculated through the vacuum filter at least twice via drain valves as near as possible tothe transformer. 'hen the oil circulation has been completed the valves between coolersand main tank shall be opened.

are should be taken to keep all air release plugs and valves open to allow escape oftrapped air during oil filling operation. These valves&plugs should be closed after

completion of oil filling.

&.& /il filling in conser)ator tank

The following procedure is recommended.

(i 0pen the valve between conservator and main tank after removing blanking andconnecting pipe

(ii +emove the inspection cover provided on the side of the conservator and checkthe air cell assuring that it is inflated. The air cell must remain in fully inflated

condition during oil filling operation. If the air cell is found deflated fit theinspection cover and inflate the air cell with dry air&nitrogen gas to 4.4-2 kg&cmGmax. through connection. A gauge may be put by removing plug. After fillingclose these connections.

(iii +emove air release plugs and provided on top of the conservator.(iv


36/87

(viii The system is now properly filled. Air release plugs are fitted in normaloperation.

&.&.1 "reca%tions

(i 0il filling in the conservator and also draining whenever required must be donevery slowly. uring oil filling, pressure in the air cell should not exceed 4. kg&sq.cm (.2 psi.

(ii If a pressure or vacuum is ever applied to the main tank the conservator must bedisconnected and a blanking plate fitted on shut off valve.

(iii o not weld on conservator to avoid damage to the air cell.(iv 0nce all the air has been driven out during oil filling in the conservator do not

remove air release plugs. 0therwise air will be sucked inside the conservator.

&.( /il filling in T-ermo sip-on

0il can be filled in thermo siphon taking oil from main tank by opening bottom shut offvalve and releasing the air provided on top of the thermo siphon tank. 0pen the top shutoff valve. :oth the top and bottom thermo siphon valve should kept open to keep thethermo siphon in service.

(.6 "ress%re testing of transformer

(i After completion of oil filling, lock 1+* and pressuri>e the air cell by fillingnitrogen& dry air to 2.4 p.s.i. (4.-2 ?g& cmG.(ii %aintain above pressure for at least 3 hours.(iii Inspect all 9oints for leakage, if any.(iv +ecord pressure testing as given below.(v After pressure testing unlock 1+* and release the nitrogen& dry air pressure of air

cell.

80T# In case of conventional oil preservation system (without air cell pressuri>econservator by filling nitrogen&dry air in conservator .

+ecord of pressure testing at site

ate Time of testing Initial1ressure

1ressureafter 3hours

+emarks


37/87

+.6


38/87

It will be observed that in the beginning I+ values drop down as the temperature goesup. I+ values will be low till moisture coming out of the insulation and start rising

before steadying. Typical dry out curve is shown below.

aution The temperature during oil circulation should not increase beyond C4 X

otherwise this may cause oxidation of oil.

The oil will be circulated through a vacuum filtration machine till the parameters areattained as per table below.

k* lass ofTransformer

#lectric


39/87

Section I;

,/ISSI/NING

1. "re commissioning c-ecks

The following checks to be done at site after transformer has been installed and driedout.

(i :reather , oil level indicator, pressure release valve, thermometer, temp.

indicators etc. for operation.

(x #arthing of main tank, %. :ox, T& driving gear, diverter, 1ump !an motor etc. .(xi 8eutral earthing.(xii #arth +esistance of #lectrodes.(xiii #arthing of bushing test tap.(xiv heck oil leakage for 36 hrs.(xv heck Auxiliary circuit voltage (62 *.(xvi alibration of 0TI&'TI with hot oil.(xvii heck 'orking of 'TI&+T repeaters at control room.(xviii All valve open to transformer blanked.

2. "re commissioning test

The following test to be done at site after transformer has been installed and dried out.

(i Insulation +esistance test(ii Test on tap changer.(iii Test on turret T.(iv ontinuity test(v *oltage ratio test.(vi magneti>ation current

(vii %agnetic balance test(viii %easurement of winding resistance(ix *erification of vector group and polarity(x %easurement of apacitance and issipation !actor. 1age -/ of 2/


40/87

(xi ation index (1I is useful parameters for logistic interpretation of I+ test results.This ratio is independent of temperature and gives more reliable data for large powertransformers. "I of more t-an 1.3 an# #ielectric asorption factor of more t-an 1.2&are consi#ere# satisfactor for a transformer w-en t-e res%lts of ot-er low )oltage

tests are fo%n# in or#er. "I of less t-an 1 calls for imme#iate correcti)e action.

The I+ value of transformer is dependent on various factors such as configuration ofwinding insulation structures, transformer oil, atmosphere condition etc. therefore,

present trend is to monitor oil characteristics for 9udging the condition of dryness of thetransformer and not to rely solely on absolute values of I+. It ma e note# t-at nonationalCinternational stan#ar#s specif minim%m ins%lation resistance )al%es of

transformers. T-e )al%e of IR ma e )er low %n#er -ea) fog or -%mi#con#itions.

uring I+ measurement, we must ensure following conditions

Transformer is disconnected from other associated equipment.

:ushings are cleaned and free of moisture

Transformer tank and core are properly grounded. :oth ends of windings under test are short circuited.

1age -C of 2/


41/87

2.1.1 IR = Temperat%re relation ,on)ersion of IR )al%e at #ifferent

temperat%reA curve for guidance of the field staff is given below. This curve can not be taken forabsolute value but will serve as a good guide for conversion of I+ values at differenttemperatures. A simple example is given as to how to calculate the value at differenttemperature.


42/87


43/87

2.2 /n Loa# Tap ,-anger

Sl.N/. 5escription 5ate /ser)ation Remarks

. *isual Inspection ofequipment

3. ;and 0peration on all taps.

-. omplete wiring of the

circuits6. )imit


44/87


45/87

This test is carried out to confirm the continuity of winding from line and neutral or lineto line with multimeter on all taps and phases

2.& ;oltage ratio test.

To determine the turns ratio of transformers during commissioning the procedure shallbe following

?eep the terminals of I* and )* open.

Apply - phase or single5phase supply according to the transformer type on ;*terminals.

%easure the voltage ratio of ;* and I* as well as ;* and )*.

+epeat the steps for each tap position separately.

The Test shall be conducted with three phase supply and voltmeters. The voltage ratioshall be measured between all pairs of windings of a transformer with externallyavailable terminals.

+esults of the transformation turns&voltage ratio are absolute, and may be comparedwith the specified values measured during factory testing. The acceptance criteriashould be that the measured values are within 4.2H of the specified values for allwindings. 0ne should also consider the trend of voltage ratio values with reference to

values measured during the commissioning tests.

The voltage should be applied only in the high voltage winding in order to avoid unsafevoltage.

Apply -5ph, 6 wire, 62v ac on ;* terminals and keep I*open

RATI/ *


46/87

10


47/87

the measured exciting current value is 24 times higher than factory tests, then it is likelyto have a fault in the winding which needs further analysis.

The residual magnetism results of higher value than normal exciting current. areshould be taken during exciting current measurement to avoid the effect of residualmagnetism in the transformer core.

a. Apply -5phase, 62 * A on ;.* terminals and keep I.* and )* open.

Tap 1osition *oltage applied

:etween (*

urrent measured(mA +emarks

)owest

+5P +

P5: P

+5: :

8ormal

+5P +

P5: P

+5: :

;ighest

+5P +

P5: P

+5: :

b. Apply -5phase, 62 * A on I.* terminals and keep ;.* and )* open.

Tap 1osition *oltage applied(* urrent measured(mA +emarks)owest

8ormal

;ighest

3+53P +

3P53: P

3+53: :

2.+ agnetic alance test

This test is conducted only on three5phase transformer to check the imbalance in the

magnetic circuit.

The procedure for conducting test is as follows

?eep the tap in normal tap position.

isconnect the transformer neutral from ground.

Apply single phase 3-4 * across one of the ;* winding terminal and neutralthen measure voltage in other two ;* terminals across neutral. +epeat the testfor each of the three phases.

+epeat the above test for I* winding also.

The test shall be conducted with 3-4 * single phase supply and voltmeter. The voltageinduced in the center phase may be 24H to B4H of the applied voltage. ;owever, when

1age 66 of 2/


48/87

the center phase is excited then the voltage induced in the outer phases may be -4H toC4H of the applied voltage.

[ero voltage or very negligible voltage induced in the other two windings should beinvestigated.

isconnect transformer neutral from ground and no winding terminal should begrounded, otherwise results would be erratic and confusing.

A11)P 51; 3-4*A *0)TA=# %#A


49/87

The winding resistance shall preferably be measured when the different in the top andbottom temperature of the oil (temperature of oil in steady5state condition is equal to or

less than 2 degree .

'inding resistance measurement shall be done only after measurement of magneticbalance and magneti>ation (excitation current. The polarity of the core magneti>ationshall be kept constant during all resistance measurement. A reversal in magneti>ation ofthe core can change the time constant and results in erroneous readings.

9in#ing Temperat%re at t-e time of testing

TA1 'I8I8= +#


50/87

(c apply 62 volt, - phase supply to )* terminals

!or example y5 transformer winding measured as follows

'53* 5555555555, '53'5555555555,*53*55555555,*53'5555555,@53'55555555,

*oltage relation

@5'$@53'K3'5'*53'O *53''53*$'53'

!or example of transformer of *ector group Pna od 1rocedure for the test is as follows and varies with the type of vector group

onnect neutral point and )* 1hase with earthSoin + and -: terminalsApply 62 volt, -5phase supply to ;* terminal

TERMINALSVOLTAGEMEASURED REMARKS

1R1 - 1Y1

1Y1 - 1B1

1B1 - 1R1

3Y1 - 1B1

3Y1 - 1Y1

3R1 - N

3Y1 - N

1R1- N

2R1 - N

2Y1 - N

2B1 - N

The following reading combination should be confirmed

1age 6C of 2/


51/87

3+58 $ 3P58 $3:58$onstantAs -+58N-P58 and -P5:N-P5P

2.16 eas%rement of ,apacitance an# 5issipation :actor.

The insulation dissipation factor (tan delta is the ratio of the resistive current to thecapacitive current flowing through the insulation on application of sinusoidal voltageunder prescribed condition. The capacitance values are relatively independent oftemperature and prevailing atmospheric conditions.

The larger component is the capacitive current whose magnitudes is determined by thetest voltage, the dimensions of the capacitor and by the dielectric constant of theinsulating material. The smaller component is the resistive current whose magnitude isdetermined by the test voltage and the resistive losses of the insulating material.

The capacitive component of the current leads the voltage by B4X. . The resistivecomponent of the current is in phase with the test voltage #. The resultant total currentleads the test voltage by an angle defined as \. And it is always less than B4X. osine \is known as power factor and for our purpose cos \ will be known as the power5factor of the insulation (or insulation power5factor.

The voltage to be applied shall not exceed half of the power frequency test voltage or 4?* whichever is lowerThe test is conducted with high voltage supply and


52/87

factor at periodic interval when compared with previous references. !or bushings, thetan delta value shall not exceed 4.CH.

The main capacitance of the bushing i.e. the capacitance between high voltage terminaland test tap is not affected by the surrounding conditions and the accepted deviationfrom the values measured at factory tests should be less than 4H. The capacitance

between bushing test tap and ground is largely influence by the stray capacitance toground parts in the transformer and hence large deviation in the measured value shall beaccepted when compared with the factory test value.

#nvironmental factors like variation in temperature, relative humidity, surroundingcharged ob9ects etc. have great influence on measurement of dissipation factor. are

shall be taken to control the above factory during measurements.

Tan delta and capacitance measurement of bushing


53/87

Low ;oltage %s-ing

capacitance (measured value

voltage + phase Pphase : phase remark

site factory site factory site factory

3 k*

4 k*

Tan elta (%#A


54/87

The measurement is performed in single phase mode. This test is performed for thecombination of two windings. The one of the winding is shorts circuited and voltage is

applied to other winding. The voltage and current reading are noted.

The test shall be conducted with variac of 453D4 *, 4 A, precision +%< voltmeter andammeter.

The acceptable criteria should be the measured impedance voltage having agreement towithin -H of impedance specified in rating and diagram nameplate of the transformer.*ariation in impedance voltage of more than -H should be considered significant andfurther investigated.

The conductors used for short5circuiting of the transformer windings should have lowimpedance (less than m5ohm and short length. The contracts should be clean andtight. 1ercentage impedance can be calculated from test result as under.

D impe#ance ;oltage applie# F rate# c%rrent F 166 C rate# )oltage F

c%rrent meas%re#

2.12 :re0%enc Response Analsis

ielectric faults in transformers may be caused by mechanical displacement

occurring during transportation, short circuit forces or inadequate clampingpossibly caused by shrinkage of windings due to ageing.


55/87

The voltage transfer function TI&+I is measured for each winding for fourstandard frequency scans from 2 ;[ to 3 %;> and amplitude and phase shift

results are recorded on floppies for subsequent analysis

Analysis of %easured !requency +esponses.

!requency responses recorded as above are analy>ed in any of the following manner

, If there is core problem. Thetraces will be distorted and change shape in higher frequencies(above 4 k;>, if thereis winding problem. hanges of less than - decibels d: ( or more in followingfrequency range may indicate following faults.

Table 1robable faults detectable by !+A

!requency+ange

1robable fault

2 ;> to 3 k;> to 34k;>

:ulk movement of windings relative to each other

244 ;> to 3%;>

eformation within a winding

32 ;> to 4%;>

1roblems with winding leads and& or test lead placement

It is normally sufficient to consider only amplitude responses, although phaseresponses are being recorded too. In practical situation, !+A has confirmed of nowinding movement and has enabled transformer to be returned to service quicklyafter incident such as tap changer faults thus avoiding a costly internalinspection. This test is sensitive, immune to electromagnetic interference andrepeatable being insensitive to the disposition of test leads and not influenced

by weather. A typical !+A curve with Amplitude and phase angle is It should be borne in mind that although !+A technique is very powerful and

effective tool and capable of detecting a range of transformer faults, it is

1age 23 of 2/


56/87

nevertheless primarily a mechanical condition assessment test and must be usedin con9unction with other diagnostic tests if a complete picture of the condition of

the transformer is to be obtained.

2.13 9TI /TI Setting


57/87

- #xcessive'inding

Temp6 #xcessive0il Temp

2 0il level

/ 1+*

C


58/87

(c standing time as per manual before final air release operation Pes&8o(d :ushing test cap tight ness ensured Pes&8o

(e :ushing oil level ensured Pes&8o(f Tank cover & bell tank earthing strips connected Pes&8o(g 8eutral grounding ensured Pes&8o(h All 1re commissioning results satisfactory Pes&8o

$.2 Energi>ing

T#


59/87

T) +epresentative 0#% +epresentative

1age 2/ of 2/


60/87

Site Inspection Record (SFQP)

Equipment: Transformer Doc No : SFQP/TRF/IR/0

Site: !a": Equipment Sr No#:

$a%e: Ratin&: 'ota&e ee: Pa&e of *+

# RE,EIPT

a. Receiving inspection

All items are received with respect to the following

delivery challans: __________________.

Delivery Challan Nos. __________________.

b) Visal chec!

"hortages and damages chec!ed w.r.t pac!ing list: __________________.

shortages and damages: #es$No __________________.

c)%roper "torage of &$' and oil drm

a)All items are stored properly ( the costly items !ept in loc!

and!ey __________________.

b)All items shall be stored on pacca floor $metallic road __________________.

c)&he site shall be visited by civil engineer fore ensring the same

before storage __________________.

d)&he site of nloading of transformer tan! shall be visited by

civil and constrction Deptt ointly __________________.

e)"pecial instrction from manfactrer regarding

storage followed: __________________.f) Dring storage both lids shold be hori*ontal position __________________.

d. +nspection of main transformer tan!:

,-ternal Damages if any #es $No ___________________.

Nitrogen pressre in the main tan! as per / 0 1 manal:

_____________!g$s2cm.

Ambient &emp.: vale for the above +R is 3 1 ohms.

R,1AR4":____________________________________________________________________

______________________________________________________________________________

e) Rating plate details

&ype of cooling: ______________ %hase: ____________

Rating 5V 0 +.V (1VA): ______________ 're2ency: ____________

Rating 6V (1VA): ______________ Connection "ymbol: ____________

No 6oad Volts 5V (!V): ______________

No 6oad Volts +.V (!V): ______________

INSULATION LEVEL


61/87




$a%e: Ratin&: 'ota&e ee: Pa&e * of *+

+mpedance 5V %osition 7$+.V 5.V: _____________

Voltage at 8ase 5V %osition 7$6V +.V:

_____________

1VA:____________ +.V$ 6V 6V:

_____________

No 6oad volts (!V): ______________

6ine Crrent 5V (Amps): ______________

6ine Crrent +.V (Amps): ______________

6ine Crrent 6V (Amps): ______________

/il temperatre rise above ambient temperatre: 9 Deg. C ________________.

inding temperatre rise above ambient temperatre: 9 Deg. C ________________.

1a!ers and serial No. ______________

#ear /f 1anfactre: ______________

Core and winding weight in !g: ______________

eight of oil in !g: ______________

&otal weight in !g: ______________

/il 2antity in !6 ______________

&ransport weight: ______________

;ntan!ing weight: ______________

%./. No.


62/87




$a%e: Ratin&: 'ota&e ee: Pa&e - of *+

*# ST.RE

a. 1ain transformer tan! Nitrogen pressre:

Chec! Nitrogen pressre is maintained at min .? !g$s2.cm and record in the register

every @3 days.

b. /6&C: +n case /6&C is separately monted Nitrogen pressre is to be maintained in

the same manner as that of main transformer tan!: _____!g$s2.cm as per / 0

1 manal.

c. 1arshalling 8o-es$control bo-es:

Chec! that these bo-es contain silica gel or heater is switched on: __________

d. "pecial instrction from manfactrer regarding storage followed:

_______________

Remar!s:_______________________________________________________________________

______________________________________________________________________________

_____________________________________________________________________________.

Date %ressre Date %ressre

Nitrogen 'illing Record

Date %ressre

8efore After


63/87




$a%e: Ratin&: 'ota&e ee: Pa&e + of *+

-# Pre Instaation ,1ec%s

a# Chec!ed availability of drawings manals 0 inspection report ________________

2# Chec!ed availability of materials as per 8/1$pac!ing list ________________

c# Availability of rating plate of e2ipment: _______________.

d. %ower transformer fondation is chec!ed that they are

properly leveled as per fondation drawings( ointly chec!ed

by civil0 const Deptt _________________.

e# Chec!ed that tools tac!les and manpower are available at site: _________________.

f# Contract for ,&C has been awarded _________________.

g. ,nsre dragging is done properly with all precation _________________.

R,1AR4":____________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________


64/87




$a%e: Ratin&: 'ota&e ee: Pa&e 3 of *+

+# Instaation ,1ec%s

( in the presence of /riginal ,2ipment 1anfactrer ,ngineers #," $ N/

a. Chec!ed proper placement of transformer on plinth:

_______________.

2# +nternal inspection of tan! ( +n the presence of /,1 engineer)

_______________.

c# Chec! +R vale of core( +n the presence of /.,.1. ,ngineer)

+R of Core:

;se @


65/87





e. 8shings are clean and free from physical damage and are clean with

C&C$ cloth. Chec! for any hairline crac! megger +R vale of bshing

before erection. (5V test tap &t>, 5V>,).

_______________.

f. 8shing is lifted properly as per instrctions. ,nsre proper se of

sling and ensre proper angle of bshing:

_______________.

Visal inspection of installed bshing to chec! that this is sealed

properly. Chec! for oil level indicator orientation and oil level

h. Chec! line lead connections for tightness. ,nsre se of proper

tor2e wrench:

_______________.

i. ,nsre trret and bshing flanges are gronded (Copper mper)

between two flanges:

_______________.

II. TAP CHANGER ASSEMBLY

(+n the presence of /.,.1. ,ngineer)

a. Visal inspection of damages if any:

_______________.

b. Chec! that /6&C driving mechanism and drive shaft are aligned

properly. &he selector and driving gear taps are synchroni*ed before

connecting copling shaft:

_______________.

c. 5andle for manal operation is properly placed:

_______________.

d. "rge relay is monted in correct direction as per arrow mar!:

_______________.

e. &ap>changer is gronded

_______________.

f. Chec! the manal operation

III. MARSHALLING BOXESa. No damage to components inside the bo-:

_______________.


66/87





b. 8o- is rigidly fi-ed and sfficient clearance is available for opening

of the door:

_______________.

c. Door gas!ets are /4:

_______________.

d. Cable glands are fitted properly. land plates are earthed and e-tra

holes on gland plate are sealed:

_______________.

e. iring is complete and &.8 are tight:

_______________.

f. 1arshalling bo- is gronded:

_______________.

5eaters are connected

h. %rovision of door light to be chec!ed

i. All wiring from the tan! to marshalling bo- shall be throgh cable

tray

_______________.

IV. CONSERVATOR ASSEMBLY

a. 6oc!ing device for mechanism of oil gage is removed after latter

erection in position:

_______________.

b. as!ets for monting accessories are new and of proper si*e:

_______________.

c# Vacm release valve is wor!ing properly:

_______________.

d# Chec! the healthiness of air cell by ptting


67/87





2# 'ans and pmps are correctly installed w.r.t. direction of rotation

mar!ed on them:

_______________.

VI.OIL PREPARATION AND FILLING

a# /il filtration in the closed separate tan!er and oil properties are tested

as per re2irement:

_______________.

i)BDV:

_______________.

ii)Mois!"# $o%#%:

_______________.

b. &ransformer is pt nder vacm as per / 0 1 instrctions:

_______________.

i)V&$!!' '#&s!"#'#%

_______________.

ii)Ti'# o( &*i$&io% o( +&$!!'

_______________.

c# /il filled p in the main tan!

d# /il is completely filled in /6&C gear bo- nit cooling system and

conservator tan!

_______________.

e. Air is completely released from all air release plgs$valves$8chhol*

relays:

_______________.

f. /il level in breather cp is p to the mar! and free air is passing:

_______________.

g. ,2ali*ing pipe fitted on diverter switch top cover is removed after

oil filling in the main tan! and blan!ing of hole is done properly:

_______________.

h. Chec! no oil is lea!ing from any oint:

_______________. 8efore

Charging


68/87





i# /il is circlated as per instrction for E= hrs(min)

_______________.

. /il testing after circlation: _______________.

,lectric 8DV strength: __E3>F


69/87





Remar!s:_________________________________________________

_________________________________________________________

_________________________________________________________

4# Pre ,ommissionin& Test

(i) Insuation Resistance $easurement

(a) indin&

between

terminal

+R vale Ambient

&emp

HC

Dielectric

absorption

I


70/87




$a%e: Ratin&: 'ota&e ee: Pa&e of *+

1a!e 1odel

"l No. Voltage range

Description between terminal +R vale 1egger

Voltage

Remar!s

(c) ,ooin& fan and pump motor

Description "r. No. +R vale Remar!s

C>@ 'an 1otor

'an motor no. > @

'an motor no. > =

'an motor no. > J

'an motor no. > ?

'an motor no. > 3

'an motor no. > I

'an motor no. > E

'an motor no. > F

'an motor no. > 7

'an motor no. > @ @=

C>= %mp 1otor

%mp 1otor > @

%mp 1otor > =

%mp 1otor > J%mp 1otor > ?

%mp 1otor > 3

%mp 1otor B I

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

". No. _ _ _ _ _ _ _

Note: Acceptance vale is G@1 ohm

Remar!s:_________________________________________________

_________________________________________________________

(ii) .i Testin&


71/87





( "ample to be ta!en prior to charging of transformer and it shold flfill the

recommendations as per +" @FII)

oil sample 8DV moistre tan delta resistivity interfacial remar!s

(min) (ma-) (ma-) (min)tension at =Edeg.

(!V) (ppm) (7cm) (min) n$m for !V class

+">@FII I< @3


72/87




$a%e: Ratin&: 'ota&e ee: Pa&e - of *+

?. 6imit "witch

3. /ver rnning device.

I. Remote %anel wiring

E /ver load

Device of Driving 1otor

F. 6ocal /peration (,lectrical).

7. Remote /peration (,lectrical).

@


73/87




$a%e: Ratin&: 'ota&e ee: Pa&e + of *+

ohm

ohm

ohm

(d) Ratio test

5V C& %rimary crrent O # %hase

"@>"=

"@>"J

"@>"?

6V C& "@>"=

"@>"J

"@>"?6V C& "@>"=

"@>"J

"@>"?

(e) Poarit" test

5V C&

"@(Pve) and "= (>ve)

"@(Pve) and "J (>ve)

"@(Pve) and "? (>ve)

+V C& "@(Pve) and "= (>ve)



6V C& "@(Pve) and "= (>ve)



(f) $a&neti


74/87





Remar!s:_________________________________________________

_________________________________________________________

_________________________________________________________

(i) ,ontinuit" test

&his test is carried ot to confirm the continity of winding from line and netral or line to line

with mltimeter on all taps and phases

Continity test by mltimeter

8etween &erminal 5V +V 6V Remar!s

Continity Continity Continity

R>N #es$No #es$No #es$No#>N #es$No #es$No #es$No

8>N #es$No #es$No #es$No

R># #es$No #es$No #es$No

#>8 #es$No #es$No #es$No

8>R #es$No #es$No #es$No

(ii) 'ota&e ratio test#

Apply J>phase ?@3 V AC on 5V terminals and !eep open 6V. 1easre voltage on +.V

terminals.

Ratio : =' / I'

&A% V/6&A, A%%6+,D V/6&A, 1,A";R,D RA&+/

%/"+&+/N @R > N @#> N @8 > N =R > N =# > N =8 > N R # 8

@

=J

?

3

I

E

F


75/87





&he ratio measrement method depends on the type of instrment sed .Diverter ratio can

also be measred by modern e2ipment

R,1AR4":____________________________________________________________________

________________________________________________________________________

Ratio : =' / ;'

&A% V/6&A, A%%6+,D

V/6&A,

1,A";R,D RA&+/

%/"+&+/N @R > N

@#

> N

@8

> N

JR >

J#

J#

> J8

JR

>

J8 R # 8

6/,"&

N/R1A6

5+5,"&

R,1AR4":

_______________________________________

_______________________________________

Ratio : I' / ;'

tap voltage applied

voltage

measred ratio

position =R > N

=#

> N

=8

> N

JR >

J#

J#

> J8

JR>

J8 R # 8

normal

(iii) $a&netiphase ?@3 V AC on 5.V terminals and !eep +.V and 6V open.

&ap %osition Voltage applied

between (V)

Crrent measred(mA) Remar!s

6owest

R># R

#>8 #

R>8 8


76/87





Normal

R># R

#>8 #

R>8 8

5ighest

R># R

#>8 #

R>8 8

b. Apply J>phase ?@3 V AC on +.V terminals and !eep 5.V and 6V open.

&ap %osition Voltage applied(V) Crrent measred(mA) Remar!s

6owest

Normal

5ighest

=R>=# R

=#>=8 #

=R>=8 8

Remar!s:

___________________________________________________________________________

___________________________________________________________________________

(i9) $a&netic 2aance test

Apply @>%h =J N V @# > N V @8 > N V

@# > N V @R > N V @8 > N V

@8 > N

=R > N

=#> N

=8 > N

V @# > N V @R > N V

V

V

V

=8 > N

=8 > N

=R > N

V

V

V

=#>N

=R>N

=#>N

Remar!s:

___________________________________________________________________________

___________________________________________________________________________

(9) Foatin& neutra ota&e measurement

disconnect the transformer netral from the grond

apply J phase ?@3 volts to the high voltage winding and ma!e the measrement in the

iv winding with respect to netral and netral point to grond.

tap primary voltage +V voltage remar!s if any


77/87





position winding applied winding measred

normal ( ) @R > N =R > N

normal ( ) @# > N =# > N

normal ( ) @8 > N =8 > N

N > earth

Apply J phase ?@3 volts to the intermediate voltage winding and ma!e the measrement

in the tertiary winding with respect to netral and netral point to grond.

+V voltage +V voltage remar!s if any

winding applied winding measred

=R > N JR > N

=# > N J# > N

=8 > N J8 > N

N > earth

(9i) indin& Resistance $easurement

=i&1 'ota&e side

tap winding resistance

resistance at E3Kc

site vale

factory

vale

position

@R@ >

=R@

@#@ >

=#@

@8@ >

=8@ R # 8 R # 8

@

=

J

?

3

I

E

F

7

@ N


78/87





=#@ > N

=8@ > N

;o> ota&e side

between resistance res at E3 deg c in ohms remar!

winding site vale factory site

JR@ >

J8@

J#@ >

JR@

J8@ >

J#@

(9ii) 'erification of ector &roup and poarit"

'or e-ample of transformer of Vector grop #na od @@

%rocedre for the test is as follows which varies with the type of vector grop combination

Connect netral point and 6V %hase with earth

oin @R@ and J8@ terminals

Apply ?@3 volt J>phase spply to 5V terminal

terminals voltage measred remar!s@R@ > @#@

@#@ > @8@

@8@ > @R@

J#@ > @8@

J#@ > @#@

JR@ > N

J#@ > N

@R@> N

=R@ > N

=#@ > N=8@ > N

&he following reading combination shold be confirmed

=R@>N =#@>N =8@>NConstant

As JR@>NGJ#@>N and J#@>@8@GJ#@>@#@

Remar!s:

___________________________________________________________________________

___________________________________________________________________________

(9iii) $easurement of tan deta and ,apacitance

=i&1 ota&e 2us1in&


79/87




$a%e: Ratin&: 'ota&e ee: Pa&e *0 of *+

capacitance (measred vale)

voltage R phase # phase 8 phase remar!


= !V

@< !V

&an delta (measred vale)



= !V

@< !V

Intermediate ota&e 2us1in&




= !V

@< !V

tan delta (measred vale)



= !V

@< !V

;o> 'ota&e 2us1in&




= !V@< 4V

&an delta (measred vale)

voltage R phase #phase 8 phase remar!


= !V

@< !V

indin&

voltage between capacitance tan delta remar!

site factory site factory

= !V 5V P +V $ 6V P


80/87





&AN4 P ,

@< !V

= !V

5V P +V P 6V $

&AN4 P ,

@< !V

= !V

6V $ 5V P +V P

&AN4 P ,

@< !V

(9i) S1ort circuit test

apply J phase ?@3 volts to the high voltage

winding

tap voltage

+V winding

short

primary crrent

measred

position applied combination +R +# +8

@

normal ( ) J phase short

highest ( )

@

normal ( ) J phase short

highest ( ) and gronded

@

normal ( ) = phase short

highest ( )

@

normal ( ) = phase short

highest ( ) and gronded

@

normal ( )

@ phase

gronded

highest ( )

Remar!s:

___________________________________________________________________________

___________________________________________________________________________

(9) Frequenc" Response na"sis

Remar!s:

___________________________________________________________________________

___________________________________________________________________________

(9i) TI .TI Settin&

"etting to be carried as per /,1 manal


81/87




$a%e: Ratin&: 'ota&e ee: Pa&e ** of *+

(9ii) Protection and aarm c1ec%

"l No Device "et for %roved Remar!sAlarm &rip Alarm &rip

@ 1ain

bchhol*

= "rge

Relay

J ,-cessive

inding

&emp

? ,-cessive

/il &emp

3 /il levelI %RV

E "%R

F Differential

relay

7 5V R,'

Relay

@< 6V R,'

Relay

@@ /ver fl-

relay@= ,arth 'alt

Relay

@J /ver

crrent

Relay

@? +nter trip

@3

(9iii)Fina IR c1ec%

After sccessfl pre commissioning test transformer shold be connects with the system on the

final megger vale shold be chec!ed.

1ain inding

"ettings 5V +V 6V /il Remar!

"et

for

%roved "et

for

%roved "et

for

%roved "et

for

%roved

'an "tart

'an "top

%mp "tart

%mp "top

Alarm

&rip


82/87




$a%e: Ratin&: 'ota&e ee: Pa&e *- of *+

between

terminal

+R vale Ambient

&emp

HC

Dielectric

absorption

I


83/87




$a%e: Ratin&: 'ota&e ee: Pa&e *+ of *+

i) &emperatre at the time of charging

/. &.+ UC

.&.+ UC

Ambient UC) 1a-imm temperatre after =? hors UC

D&6 Representative /,1 Representative


84/87

DELHI TRANSCO LTD Standard Field Quality Plan

Name of Equipment: Transformer

Doc No: SFQP/TRF/01 Pae 1 of !

Sl

No

Characteristic /Item Reference

document

/acceptance norms

Remark

1

"

#

!

RE$E%PT

Receiin! Inspection

"isual inspection

#roper stora!e of transformer and Tr$ Oil drums

Inspection of main transformer tank

Ratin! #late details

ST&R'(E

%ain Transformer tank Nitro!en pressure

OLTC Nitro!en pressure& if applica'le %arshallin! 'o(

Stora!e instruction compliance

PRE) %NST'**'T%&N

Aaila'ilit) of Instruction %anual etc

Aaila'ilit) of all material

Aaila'ilit) of ratin! plate

Transformer foundation

Aaila'ilit) of tools& tackles and %an #o*er

A*ard of Contract for ETC

#roper dra!!in!

%NST'**'T%&N

#roper placement of transformer

Internal inspection of tank

IR "alue of the core

I$+,SHIN- ASSE%+L.

Tan delta and capacitance test

Test on turret CT

Cleanliness and dama!e of turret CT Healthiness and correctness of turret CT and their

terminal plates

Sealin! !asket

Nitro!en !as pressure

Cleanliness &free from ph)sical dama!e and IR

alue

+ushin! liftin!

+ushin! sealin!

Oil leel

Ti!htness of Line lead connection

-roundin! of turret +ushin! flan!es

II$ TA# CHAN-ER ASSE%+L.

+O%/#ackin!

list/manufactures

instruction manual

%anufactures

instruction manual

Approed dra*in!/

%anufactures

instruction

manual/Test report

Approed dra*in!/

%anufactures

instruction

manual/Test report


85/87



Doc No: SFQP/TRF/01 Pae " of !

Sl

No


document

/acceptance norms

Remark

+,

"isual inspection

OLTC driin! mechanism and drie shaft

Handle for manual operation

Sur!e Rela) mountin! direction

-roundin! of tape chan!er

Check of manual operation

III$ %ARSHALLIN- +O0

#h)sical inspection

%arshallin! 'o( fi(in! and clearance Door !askets

Ca'le !land fi(in! and !land plate

1irin! and terminals

-roundin! of %arshallin! +o(

Heater connection

#roision of door li!ht

1irin! throu!h ca'le tra)

I"$ CONSER"ATOR ASSE%+L.

Lockin! deices for mechanism

-asket

"acuum release ale

Healthiness of air cell

"$ COOLIN- S.STE% #I#E 1OR2

"isual inspection

Direction of rotation of fan and motors

"I$ OIL #RE#ARATION 3ILLIN-

Oil filtration and oil properties

"acuum as per O% instruction 3illin! of oil in the main tank

Oil fillin! in OLTC& !ear 'o(& coolin! s)stem etc

Air release

Oil leel in 'reather

E4uali5in! pipe on OLTC s*itch top coer

Oil leaka!e

Oil circulation

Oil testin! after circulation

Silica !el

Checkin! of isolation ale

PRE)$&--%SS%&N%N( $.E$Approed dra*in!/


86/87



Doc No: SFQP/TRF/01 Pae # of !

Sl

No


document

/acceptance norms

Remark

,

6i7 +reather Silica !el 6+lue colour *hen

dr)7

6ii7 Oil in the +reather housin! cup$

6iii7 All ales for their correct openin! and

closin! se4uence$6i7 Oil leel in conserator tank$

67 Oil leel in 'ushin!s$

6i7 Release air& *hereer necessar)$

6ii7 Coolin! accessories 6#ump motors& 3an

motors etc$7 for direction and O/L settin!$2iii3 Direction of +uchhol5 rela)

i43 +uchhol5 rela)& oil leel indicator&

pressure release ale& thermometer&

temp$ indicators etc$ for operation$

43 Earthin! of main tank& %$ +o(& T/C

driin! !ear& dierter& #ump 3an motor&ca'le !lands etc

6(i7 Neutral earthin!$

6(ii7 Earth Resistance of Electrodes$

6(iii7 Earthin! of 'ushin! test tap$6(i7 Check oil leaka!e for 89 hrs$

6(7 Check Au(iliar) circuit olta!e 69:; "7$

6(i7 Cali'ration of OTI/1TI *ith hot oil$

6(ii7 Check 1orkin! of 1TI/RTD repeaters at

control room$

6(iii7 All ale open to transformer 'lanked$6(i(7 Clearances as per O-A

443 Checkin! of terminal

$&--%SS%&N%N( TEST6i7 Insulation Resistance %easurement

6ii7 Oil Testin!

6iii7 D-A

6i7 On Load Tap Chan!er

67 Test on turret CT$

6i7 Continuit) test

6ii7 "olta!e ratio test$

6iii7 %a!neti5ation current

6i(7 %a!netic 'alance test

6(7 3loatin! neutral olta!e measurement

6(i7 1indin! Resistance %easurement6(ii7 "erification of ector !roup and polarit)

6(iii7 %easurement of tan delta and Capacitance

6(i7 Short circuit test

%anufactures

instruction

manual/Test report

Approed dra*in!/

%anufactures

instruction

manual/Test report


87/87



Doc No: SFQP/TRF/01 Pae ! of !

Sl

No


document

/acceptance norms

Remark

6(7 3re4uenc) Response Anal)sis

6(i7 1TI OTI Settin!

6(ii7 #rotection and alarm check

6(iii7 3inal IR check

6(i(7 3inal check prior to commissionin!

Note:

:7 DTL specification shall mean DTL Technical Specification& approed dra*in!s& LOA

proision for specific contracts$

87 Tests/Checks indicated at column No$8 of S3

transformer pc test

Documents