02 power transformer#

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POWER TRANSFORMERInternational standardsIEC 76- Power transformerIEC 354- Loading guide for oil-immersed transformerIEC 542- Application guide for on load tap changers.IEC 185- Current transformers.IEC 186- Voltage transformerIEC 551 - Determination of tresformer and reactor sound levels.IEC 722- Guide to the lihtning impulse ans switching impulse testing of power transformer andreactors.Type of transformer mengikut insulation sistemImmersed transformerSahagian aktif diletak dalam tangki dan diisi bahan dielektrik:

Mineral oils - product petrolium yang murah tetapi rendah flash point dengan itumembataskan penggunakannya dalam sesuatu kes.Silicone oils - cecair dielektrik paling sukar terbakar.

Sealed transformerUntuk alatubah kuasa kurang dari 16MVA dimana kuantiti dielektriknya rendah dan perlu dielakterdedah pada udara. Memerlukan ruang antara dielektrik dan permukaan atas tangki kerana ianyamengembang.Dry type transformersAlatubah dengan dry insulation penyejukan udara luar tampa cecair:

1. Class H impregnatedImpregnated dan polymerised bersam varnish digunakan untuk insulation winding. Insulatordan varnis digunakan untuk mencegah kebakaran, keluar asap dan wap toksik.2. Cast-resin (encapsulated)

Winding alatubah di dalam epoxy resin, diperkuatkan dengan fiber glass dan ianya dibuatkhas untuk mengelakkan api melarat.

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Part of Power Transformer

Sistem PenyejukJenis penyejukanMineral OilAir (water)Udara (air)Jenis pengedaran penyejukNaturalForced

Jenis penyejukan biasa digunakanNatural circulation of oil and air

Simbol0wASimbolNF

Natural circulation of oil and forced circulation of airForced circulation of oil and airForced circulation of oil and waterDry type transformer with natural cooling in airDry type transformer with forced air ventilation

02 Power Transformer

Bahagian-bahagian aklatuba Flange of mounting.2 Teras (Core)3 Penyejuk (Cooler- Radiator)4 LV bushing.5 Terminal sambungan.6 Teras- bolts.7 Thermometer.8 Tangki dan penutup9 Conservator10 Lilitan pada teras (winding)11 HV bushing12 Pembawa (carriage)13 Header14 Buchholtz relay

SimbolONANONAFOFAFOFWFANAN

2

01. Flange for mounting.02. Tank, Tank cover.03. Core04. Conservator05. Cooler (Radiator)06. Windings on 3

07. LV bushing08. HV bushing09. Terminals connections10. Carriage11. Core-bolts12. Header13. Thermometer

14. Buchholtz relay


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Transformer Protection Melindungi alatubah dari gangguan dalaman, litar pintas, lebihan voltan dan beban lampau. Melindungi sistem yang bersambung dengan alatubah dan persekitaran dari kegagalan yangdatang dari alatubah. Menjaga operasi alatubah, memberi amaran dari bahaya yang akan terjadi dan menghadkankerosakan jika berlaku kegagalan.Safety valveFunctionThis sensitive to a presure rise in the transformer tank due to its rapid opening ( a few mili-second) thepresure is released. It is usualy placed on the cover of the transformer it is protecting.

C o n t a c ~(opttOMl.Lateralgasket

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( 3 c1::1 4c:- t :Contacts

Operation

IFrame

MobilediSC

AdJUStable spnngType 1 : 0.2 to 0.4 barType 2 : 0.5 to. 0.7 bar

If an incident occurs, the release pressure, 0.2 or 0. 7 bar is reached. The valve opens.The dielectric escapes as long as the valve is open, and avoid a damaged to the tank.Protection relay (Buchholz)FunctionTrip out the transformer if there is a release of gas arising from the decomposition of the solid andliquid insulating material due to the action of heat or electric arcing.In the event of a fault two contacts can operate:a) alarmb) trip of the circuit breaker in the supply.Operation

A vilent discharge of gas causes a movement of the transformer oil towards the conservator.This closes a contact and causes the circuit breaker on the supply side to open. When the incident is only a minor one, the discharge of gas bubbles acts on a second contactwhich sets off an alarm. If there is a serious leak, the successive tilting of two contacts gives the same protection.

Tap canger protection relayProtects the tap changer and trasformer from any damage if a defect arises in the tap changer. Theprotective relay operates to put the transformer off circuit.Automatic non-return valveIf a break occurs in a pipe, a joint or even a terminal, this valve avoids the liquid dielectric in theexpansion tank being lost.This devise is only used with very large expansion tank.

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F'tg. ,Normalstate

Air dryer (silica gel)This has two function:

Ftg. 2After sudden flowol cooling medtum

to absorb the moisture in the air drawn in during contraction( sejuk dan susut).to stop air entering into the transformer during small variations of load to avoid permanent contactbetween the drying product and atmospheric air.OIL OILEXPANSION COOLING DOWN

atrentersbreatherDiaphragm expansion tank

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no contact betweenatr tnStde transformerand atmosphere

The diaphragm in the expansion tank avoids any contact between the oil and air. Hence the oil cannotoxidise and become polluted.The elasticity of the diaphragm (rubber sheet) allows variations of volume in the dielectric dependingon temperature.vent Upper flange Hangtng clamps Vent

IIIilliIlI. Atr dryero ~

6ork valve


VentFlexibleseparator

Conservator dram.ng4


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Nitrogen fillingTransformers can be shipped or stored without oil. In this case, to avoid moisture entering the tank isfilled with nitrogen under a pressure higher than atmospheric.If the temperatture rises, the increase in pressure is released by the opening of a safety valve.

Spark gapSpark gaps restrict the voltage that can appear at a terminal to a known value. When they flash overthey can cause the circuit breaker to trip through a fault to earth.

Surge arrestorNon linear resistance surge arresters are connected between phase conductors and earth to protectthe transformer against overvoltages arising from the opening and closing of circuits and fromatmospheric overvoltages.

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-,=t::~ . - . .....,...--..,.....,.,..,-----...;;..! 'Current transformerUsed for metering or protection, it is either interior type (in the oil) or exterior type (mounted on thetransformer cover) for medium and high voltage terminals.The current transformer can be used for tank-earth protection. In this case it supplies a maximumcurrent relay to indicate a winding fault to earth.Thermal imageUsed to indicate the winding temperature. It enables the highest temperature of the winding to bemeasured. It consists of themometric equipment combined with a heating resistance through which acurrent flows reflecting the current flowing in the winding whose temperature is being measured.


, . Oil fllleo pocket2. Flextble tube3 Heattn!; reststor4. Matr"1 curren1 transformer5. Adao!atiOii unit

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ThermometerThe thermometer can be provided with a probe inserted in an oil filled pocket, the probe beingconnected by a capillary tube to the control cabinet. This equipment is mounted directly on thetrasformer cover. In all cases it can be equipped with a maximum index or an alarm-trip contact.ThermostatMounted on the transformer are used for:starting up the radator ventilation or air cooler of power transformers.signaling alarm" and tripping out.These devices consist of a thermometric assembly with a probe which can be installed in a pocket.

Button for Butlon lord1f1erence a d J u S t m e n t ~ adjUSting temperatureEngraved plate ~n black .... 6 V opera110nbac.kground -......_o 0 ; 1: :.- -YJ_jDifference t ' 0 adjUStment ~ . .,.. 'l.Ji)i. +;index I 0 ~ ~ r ,Bulb

0 ;T e m p e r a t u r e ~ : : . - ~ . '(-:adjustment - 1 _ " " ; : ; : ~ -:::::=-J .; 'tndex - ;>Engraved plate on . ' o " " " ' V f ~red background ~ )? ..,../'Capillary tube "" - ' 22 0 connection

witrl 1 5 thread

Oil level indicators

Thermostatic probeThermostatic lozenges can be placed onthe low voltage windings of dry transformers for alarm and tripping out.

The magnetic level indicator indicates the oil level in the conservator of power transformers. It ismounted on one end of the conservator and is equipped with one or two contacts for remoteindication.A glass tube mounted on the conservator is also used for level indication. A pointer shows the level atthe filling temperature.

Oil circulation indicatorThis equipment is used on transformers with forced oil circulation using a pimp. An arrow indicates the"stop" and "operating" positions.Provision is made for remote indication.NO FLOWContact closed


FLOWContact open

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Water circulation indicatorWhen the cooling system includes water coolers this equipment indicates normal circulation of thewater.It is provided with reversing contacts.

-The pressure exened on the Kpaddle" by the flow leversthe roo fitted with the magnet.

Tank-earth protectionIn the case of systems with neutral connected to earth, an earth fault cause high currents to circulatein the transformer tank toward earth. It is possible to insulate the transformer from earth. This enablesa current transformer to be inserted between tank and earth which suppl ies a current relay giving thecommand to trip out the circu it breaker when a fault arises.

1 -differential relayA-tnp COt!H-b1as COli

Principle of differential protectionof transformersEarth terminalAll transformers are provided with an earth terminal. The connection to the earthing circuit is madedirectly or through a current transformer for the tank-earth protection. Surge arrestors and spark gapsare also provided with earth terminals.Other accessoriesStandard or optional

Valve withtappedconnection Valve with separate tapped connection


Groved hllngtor llekbte ru::>e i apoea ltl!ngfo" c ~ r v , e c t t o n totransformer or 011trea:-nc;r,: a;; paratus

Symetrlcal connection Gulllemln type

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Transformer Vektor

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Dyll

Ytl II

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Oelil

Yd S

D. d . delta - z ~ z : tg-zagY, y : s t a r ~ ~ N. n neutralCapital !etters: H1gh VoltageSmall letters : Low V o H a ~ t eAfter these letters the clock mdex is shown.The value of the phase di fference betweenthe terminals A and a rs obtamed bymultiplytng the clock index by 3Qu.The letters A, B, C reler to the Htgh Voltagewinding. and a. b, c the Low Vol!agewinding.The letters are shown on the transformer infront of the corresponding lerminars.The connection diagrams are drawnassuming that the windings have the samedirection relative lo the coil.

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02 power transformer#

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