Summer Training Report on

Power Transformer

Presented by : Dheeraj Upadhyay Electrical & Electronics Engineering

POWER TRANSFORMER

They have rating above 200 Kva and used in generating station and

substation used for power transmission line for stepping up and stepping down the voltage.

Stages of Power Transformers manufacturing are :

Design & DrawingWinding ManufacturingCore BuildingUnlacing of Core Fitting Bottom

insulationCore Coil AssemblyFitting of Top insulation

Relacing of core Terminal Gear

MountingFinal Tanking TestingDespatch

Design & Drawing : 1 Φ

Phase 3 Φ MVARating KVA

66 kvVoltage Class

11 kv

50 HzFrequency

60 Hz Δ Connection

Y Generating

Purpose Substation Distribution

Winding Used :

R-S Coil : reverse section winding.

Helical coil : winded in shape of spring.

Spiral coil : simply wounded on the base.

Interleaved coil : winding current rotates in same conductor

Composite winding : more than one conductor winded with each other.

Helical winding

Interleaved

Core of Transformer :Material Used :

CRGO : Cold rolled grain oriented silicon steel is used to build the core.

Purpose of using CRGO is to reduce the Hysteresis losses. Laminations of these sheets minimizes eddy current loss.

Unlacing of core :

This is basically the phenomena of

removal of top end frame of the core assembly so that the coils can be mounted on the core.

Core – Coil Assembly :

Core coil assembly consists of assembling the windings to the core assembly. Core assembly is placed on a suitable leveled platform.Tighten the three limbs with webbing tape. Top channels and top yoke laminations are removed and placed on a table in the same sequence. Bottom insulation items like pressboard rings, petals; perma wood rings are placed on bottom yoke on each core limb. Core wraps as specified in the design details are covered to the core limbs and tightened with cotton tape.

L.V Coil : primary coil for step down transformer, made in order to allow the flow of large current through it .

H.V Coil : Secondary coil for step down transformer, made in order to allow high voltage and hence small current through it.

T.V Coil : this is known as the tertiary voltage coil.

Relacing Of Core :The top yoke is again attached toThe Rest of the Core, the sheets Are attached one by one or inPackets (generally 2 to 4 innumbers) to the core limb in erect position. Then the job is dipped in oil and then heated toremove any kind of moisture in it. After that the job iscompressed i.e. pressure is applied from the top to compress the coil and achieve the required CD of the coil as specified in design.

Processing and DRY OUT :

The presence of the moisture brings about thereduction in the electric strength of material andalso increases its volume.

Dry out is necessary in this condition.The final drying out is commenced either when the core and winding are placed or when they are fitted in to there tank, all main connectionsmade and the tank placed in an oven andconnected to the drying system

Final Tanking :Tanking means…..assembling the core coilassembling job intotransformer tank withall necessary accessoriesaccording to bill of material and design diagram.

Testing of Power Transformer

Tests during manufacture : Core plate checksCore frame insulation

resistanceCore loss measurementWinding copper checksTank tests

Final Testing :Routine TestsVoltage ratio and polarity. winding resistance. impedance voltage, short-circuit

impedence and load loss dielectric tests. (a) separate source AC voltage. (b) Induced voltage.no-load losses and current.on-load tap changers, where appropriate.

TYPE Tests :Temperature rise test.noise level test.lightning impulse tests.

EQIPMENTS USED FOR THE PROTECTION OF POWER TRANSFORMER

• Lightning Arrester.• Over Current Relay.• Buccholz relay.• Earth fault relay.• Oil level indicator.• Over fluxing relay.

THANK

YOU