AMRITSAR COLLEGE OF ENGINEERING & TECHNOLOGYTRAINING REPORT

Submitted in partial fulfillment of the requirement for the award of Degree in

ELECTRICAL AND ELECTRONICS ENGINEERINGBY

Punjab Technical UniversityJallandhar

Submitted to:- Submitted by:- Er. Ajaypal Singh Atinder Pal Singh Virk

Om Prakash Narinder Sharma Neeraj

ASUMMER TRAINING

REPORT ONPUNJAB STATE POWER CORPORATION LTD.

TRANSFORMER REPAIR WORKSHOPAMRITSAR

ASummer training Report Submitted

In Partial Fulfillment of the Requirementsfor the award of Degree ofBachelor of Technology

InElectrical & Electronics Engineering

ByAtinder Pal Singh Virk

Om PrakashNarinder Sharma

Neeraj

Punjab State Power Corporation Limited Workshop Organization Headed by Chief Engg. Of Workshop = Iqbal Singh Aim – To repair damaged Transformer at cheap rates instead of paying high amounts to privates sectors 2 major circles = Amritsar [4] , Patiala [8] Working = Monthly target to repair 120 units 25 KVA = 1 unit 63 KVA = 1.5 unit 100 KVA = 2 unit 200 KVA = 4 unit

Introduction to Organisation

Hierarchy in Transformer Repair Workshop

Additional Superintendin

g Engineer

Junior Engineer Fore Man

FitterHelper

Working sequence in TRW

TRW Yard

Washing Section

TRW Store

Tank

Repaiing Section

Core Ovening Section

Box-Up Section

Dehyration Filling

Section

Pre Testing

Painting

Final Testing

TRW Store

A transformer is a Static device, which transfers electric power from one circuit to another. Does so without change of frequency. Has voltage at the recei- -ving end lower or higher from the supply circuit.

What is Transformer

Working Principle

Working Principle:- The main principle of operation of

a transformer Faraday’s law of electromagnetic induction

According to Faraday’s law, “Rate of change of flux linkage with respect to time is directly proportional to the induced EMF in a conductor or coil".

A transformer consists of a rectangular core of soft iron in the form of sheets (.35mm to .5mm for 50Hz to 25Hz frequency).

Two separate coils of insulated wires, a primary coil and a secondary coil are wound on the core. These coils are well insulated from one another.

Construction

Core Type In this type of T/F the winding

surround the major part of core.

Shell TypeIn this the core surround the major part of the winding

Constructionally ,the transformers are classified as:-

Types of transformer

There are generally two types of transformer

Step up transformer Step down transformer

Some important types are given as: Auto-transformer Poly-phase transformer Leakage transformer Resonant transformer Instrument transformers

Types

A step up transformer is a device that converts low alternatic voltage to high alternating voltage.

In another word, a transformer in which Ns>Np that is called step up transformer.

Step up transformer

A step down transformer is a device that converts high alternatic voltage to low alternatic voltage.

In another word, a transformer in which Np>Ns that is called step down transformer.

Step down transformer

An autotransformer with a sliding brush contact

An autotransformer has only a single winding with two end terminals, plus a third at an intermediate tap point.

AUTO-TRANSFORMERS

For three-phase supplies, A bank of three

individual single-phase transformers can be used,

OR all three phases can be made as a single three-phase transformer.

POLY-PHASE TRANSFORMER

INSTRUMENT TRANSFORMERS Current transformers,

designed to be looped around conductor.

A current transformer is a measurement device

provide a current in its secondary coil proportional to the current flowing in its primary.

Main parts of a transformer

BUCHHOLZ RELAY: It is a very sensitive gas and oil operated instrument which safely detect the formation of gas or sudden

pressure inside the oil transformer.

CONSERVATOR:- It is used to provide adequate space for the expansion of oil when transformer is loaded or when ambient temperature changes

Parts of Transformer

TANK:- Basically this is a container used to keep windings and insulation oil. The tank is Made up of Mild Steel.

SILICA GEL BREATHER:It absorb the moisture from the air. it is a chemical material these are the only one main component inside the breather basically silica gel is a brown colored one after the absorption silica gel become pink

OIL LEVEL INDICATOR: It is used to show the oil level in the transfor- -mer. this is a ordinary part situated on the side of the conservator for proper oil checking oil tank wants a specific amount of oil.

RADIATORS:- These are used for the purpose for the cooling of the transformer oil. The oil circulates all the time from these radiator

parts

Winding temprature indicator: used to show the temperature of transformer winding.

TEMPERATURE METER (O.T/W.T): These are used for taking the readings of O.T.I - Oil Temperature Indicator and W.T.I - Winding Temperature Indicator

Tap-changer: This is used for the tapping of the Transformer at different levels.

WINDINGS PRIMARY WINDING - In the case of power

transmission primary windings are the main element external connection from the power is connected to the winding.

SECONDARY WINDING - This is a another winding for reducing power (in the case of step down purpose) .

M

Primary Wining Secondary Wining

This is a outer unit, this is used to prevent unwanted leakage of electricity.

PORCELIN BRUSH

Working sequence in TRW

TRW Yard

Washing Section

TRW Store

Tank

Repairing Section

Core Ovening Section

Box-Up Section

Dehydration Filling

Section

Pre Testing

Painting

Final Testing

TRW Store

Transformer Workshop Yard (TWY):- The damage transformers are received here. All types of transformer of 25KV, 63kv, 100kv and 200kv rating received in damage condition.

Transformer Repair Workshop Store (TRWS), Tank & Washing:- In this section the power oil & windings taken out from the Tank and blank tank is send for washing in washing section

Repairing Section: In this section damage windings are repaired if all windings are burnt then whole windings were replaced with new windings.

The core shown in fig. is made of Silicon steel with thickness 0.35 to0.5mm. These laminated core legsare tighten with white tape. So,that the flux in the coils will linked properly with the other coil.

The channel's shown in IInd fig. are also use tighten the core andAlso fix the whole set of core andWindings in the tank. The main difference required between thechannel and windings should atleast 16-20mm which can beincreased or decreased accordingto the requirement.

It is noted that for 25KV, 63KV, 100KV, 200KV or any Rating Transformer the turn ratio will not less than 43780 and not more than 44220.

Connections:- The distribution transformer connection always in star- delta connections means the connections of Primary are in Delta connections and the connection of Secondary in Star Connections.

Core Ovening Section:- Core ovening section is the most important part of repairing transformer.

This is used to remove the moisture from the core and windings of the transformer. In this the core is placed inside the oven at 40-60C temp in Summer season and 100-120C in Winter season.

BOXUP Section:- This is the section where the core is placed inside the Tank and core is fixed inside the core and all outer connections were made the

LT and HT were first fixed with the Brass made rods and then that rods were fixed with Porc- -elain Brushes .

Dehydration Filling Section:- The oil used in the transformer are Power oil or Mineral oil. It provides cooling to the transformer. Before filling the oil in the transformer it is heated at 60KV/minute means 60KV is applied to the oil for one minute in oil testing machine. If the oil is withstand with this voltage then it is further used for filling.

Pre Testing:- In this everything is tested like IR value, the oil Temp like after filling the oil in tank it is again tested with 40KV/min. The requirement is 25KV/min but for overload safety purpose it is tested at 40KV/min.

Final Testing :- The final testing is divided into four parts

(a) HVHP (High Voltage & High Pressure) (b) DVDF (Double Voltage Double Frequency) (c) No Load Losses (d) Full Load Losses

Maximum Transformer Efficiency

The efficiency varies as with respect to 2 independent quantitiesnamely, current and power factor

Thus at any particular power factor, the efficiency is maximum if core loss = Iron loss .This can be obtained by differentiating the expression of efficiency with respect to I2 assuming power factor, and all the voltages constant.

At any particular I2 maximum efficiency happens at unity power factor. This can be obtained by differentiating the expression of efficiency with respect to power factor, and assuming I2 and all the voltages constant.

Maximum efficiency happens when both these conditions are satisfied.

Losses Iron or core losses – caused by alternating flux in core Hysteresis losses – During each A.C. cycle current

flows which magnetize and demagnetize the core. As a result of which energy is lost in each cycle

Eddy Current losses – Due to consequent heating of material it results in loss of power

Copper losses or ohmic losses - Due to ohmic resistance in transformer winding

Small losses which are mostly neglected Stray load losses – leakage field induces Eddy

currents in tank walls , bolts etc. Dielectric losses - occurs in insulation material

basically in oil and solid insulation

Open circuit Test It is used to determine Lm1 (Xm1)and Rc1

Usually performed on the low voltage side

The test is performed at rated voltage and frequency under no load

Short circuit Test It is used to determine Llp (Xeq) and Rp(Req)

Usually performed on the high voltage side

This test is performed at reduced voltage and rated frequency with the output of the low voltage winding short circuited such that rated current flows on the high voltage side.

Applications of Transformer

For Voltage Step Up For Voltage Step Down Amplifying Systems Loud Speakers

Conclusion

I would like to thank my college for providing us such an opportunity to be a part of great organisation i.e. PSPCL . Sir, it was really fruitfull that we got a chance to learn practically about which we are taught in college . I would like to request whole young generation to work hard , achieve your goal and prove who you are and make your individual identity because some said that “Say aim is meant to achieve !! instead later to say , it was just a nightmare { कहते� ह� किक लक्ष्य प्रा�प्ते करने� क� लिलए ह�! बजा�य ब�द में� कहने� क� लिलए, यह बस एक ब�र� सपने� था� } ” . The whole thing matters in preception . So just dream and have courage to achieve because even a needle was first dreamt and later invented .

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