Welcome to My

Presentation

Prodip Kumar Das

ID#11105136

Program : BSEEE

Study on

Manufacturing of 11/.415kv Distribution

Transformer

at Navana Electronics Limited

1/2/20152

Contents…..

1/2/20153

Objective

Company Profile

Basic Theories

Working Principle of Transformer

Distribution Transformer

Oil immersed distribution Transformer

Manufacturing of 3-Phase Distribution Transformer

Recommendations

Objectives…..

1/2/20154

To apply theoretical knowledge in the practical field

To observe the manufacturing process of distribution transformer, testing

Collecting knowledge regarding distribution transformer

Developing skills and techniques relevant to our careers

Company Profile….

1/2/20155

Name: Navana Electronics Limited

Factory location: Bashtola, Shahazadpur, Gulshan -2,

Dhaka-1212

Ownership: Navana Group

Contd.

1/2/20156

Products:

PFI LT Switchgear HT Switchgear

Contd.

1/2/20157

Transformer

Products:

In NEL, the producing three phase transformers are oil

immersed distribution transformer and their cooling system

is ONAN type.

Basic Theories….

1/2/20158

1. Transformer is an electrical device that

transfer electric power from one circuit to

another

2. It does so without a change of frequency

3. It accomplishes this by electromagnetic

induction

4. Where the two electric circuits are in

mutual inductive influence of each other

Working Principle of Transformer….

1/2/20159

Distribution Transformer…..

1/2/201510

• Used for distribution of electrical energy

Generally, operates at low voltage as less than 33KV in industrial purpose

and 440v-220v in domestic purpose

Three phase distribution transformers ,widely used in 11kv distribution

line to step down the voltage level.

Oil immersed distribution Transformer….

1/2/201511

Manufacturing of 3-Phase Distribution

Transformer

1/2/201512

1/2/201513

1/2/201514

Active Part :

The ferromagnetic core

and windings

Transformer manufacturing procedures….

1/2/201515

Core material…. …

1/2/201516

The mostly used core material

is CRGO-Cold Rolled Grain

Oriented steel sheets of 3% of

Silicon

Thickness of the CRGO sheets

usually 0.27 mm

Oxide coating is provided for

CRGO laminations to reduce

eddy current losses

Core Cutting….

1/2/201517

Straight type core cutting

1/2/201518

Core Jointing on Channel….

This is the simplest form of joints

The flux leaves and enters at the joint in

perpendicular

1/2/201519

Placing laminated sheets by hand or

hammer manually

No air gap between the joints of two

consecutive sheets

The entire assembly is done on a frame

commonly known as core channel

These frames being used as a clamping

support of the core assembly

Covering copper wire with Insulating Tape…..

1/2/201520

The mostly used material for

winding wires or strips is

copper .

The copper wires or strips are

wrapped by insulating tape or

DPC paper.

Low Voltage Windings…..

1/2/201521

Vertical machine is used to

prepare the LV winding

The helical and double layers

Number of turns varies on

KVA rating

Low Voltage Windings…..

1/2/201522

Greater simplicity in fitting

cooling ducts

More even heat distribution

through the windings

Gape between two layers

Starting End

Finishing End

High Voltage Windings….

1/2/201523

Horizontal machine is used to prepare the

HV winding

HV windings are of layered construction

The conductors are made of more round

wires, either with an insulating paper

The insulation between the layers

consists of DPC paper

High Voltage Windings…..

1/2/201524

Contd.

1/2/201525

Insulation between two layers :

Insulation between

two layers of DPC

paper

Core-Coil Assembly…..

1/2/201526Opening the upper yoke

Insulating between core and LV winding

1/2/201527

Cotton tape

Press board

Contd.

Placement of LV Winding:

1/2/201528

The LV windings in the core

limb .

They are fitted tightly in all

three limb using pressed board.

Contd.

Contd.

1/2/201529

Press Board Cutting DPC Paper

Isolating HV from LV winding:

Contd.

1/2/201530

Before inserting the HV winding

Placement of HV Winding:

1/2/201531

This coil is placed on LV winding

as second layer of core

First LV coil then HV coil

The gap between the LV and HV

coil is filled with runner of pressed

board

Contd.

Contd.

1/2/201532

Inserting the Upper Yoke:

The active part before connection

Connections…..

1/2/201533HV Side ( Delta Connection) LV Side (Star Connection)

1/2/201534

Contd.

Vector grouping.....

1/2/201535

The vector grouping in NEL is Dyn 11:

Delta connected HV winding

Star connected LV winding

Neutral brought out

LV is leading HV with 30° (11

o’clock)

Tap Changer…..

1/2/201536

Tapping is terminated just

bellow oil level

External handle

Taping is done on HV winding

Used to regulate the output

voltage to required levels

Tap Changer

External Handle

1/2/201537

Taping Wires

Connected to HV

coilsChanger

How Tapping done:

pe

Moisture Control…..

1/2/201538

The whole active part of the transformer

in the heat chamber

Keeping it there for 72 to 96 houres with

a continuous heating temperature of

100° - 141° C to clean the moistures in it

Bringing it out after getting proper

insulation

The Tank…..

1/2/201539

Functions of Transformer Tank...

1/2/201540

A container for the cooling liquid

Providing shielding against

electromagnetic field leakage

Radiator….

1/2/201541

Made steel like tank

Attached with the tank

Radiate the heat from

insulating oil and makes the

oil cool

Inserting The Active Part Into The Tank…..

1/2/201542

Whole active part is covered by

press board

Crane is used to lift the active part

By handling a chain the active part

is put slowly in the tank

Bushings….

1/2/201543

Counteracting the electrical field

strength

Insulating the incoming or outgoing

conductor into or out of the transformer

tank

Conductor

Insulator

Conservator….

1/2/201544

Providing adequate space for

expansion of oil inside the tank

It also acts as a reservoir for the

insulating oil.

The oil level indicator indicates the

oil level

Oil level should not fall below

minimum limit

Filling Oil…..

1/2/201545

Function of Transformer Oil….

1/2/201546

Providing dielectric strength

to the insulation system

Providing efficient cooling

Protecting of the transformer

core and coil from chemical

attack

46

QC Tests….

1/2/201547

Testing of Distribution Transformer:

Insulation test

Ratio test

Open circuit test

Short circuit test

1/2/201548

1/2/201549

Rating Plate

1/2/201550

Ready to Delivery

Recommendation…..

1/2/201551

NEL should cut the core sheets as angular core cutting and arrange

the core sheets by mitered joint system to reduce core loss.

The transformer manufactured by NEL should always use Buchholz

Relay that protects the transformer all the time and increase its life

time.

Contd.

1/2/201552

Elaboration of My Recommendations:

In Mitered core joints the flux goes by an angle 450 .

That is very smooth path for the flux

Cross grain loss is minimum and core loss will be reduced

If any fault occurs in

transformer buchholz rely

gives alarm and can protect the

transformer

1/2/201553

1/2/201554