INDUSTRIAL TRAINING SEMINAR

ON

“TRANSFORMER CONSTRUCTION”

AT

BHEL BHOPAL

DURATION: 29TH MAY – 25TH JUNE,

2014

HEAD OF DEPARTMENT

Dr. Deepak Nagaria

PRESENTED BY

Mandeep Singh

EE Final Yr

B.I.E.T Jhansi

Roll No: 1104320020

UNDER GUIDENCE OF

Shri Shailendra Kumar Somi

Sr. Er. TRM Div BHEL Bhopal

1. INTRODUCTION

2. TRANSFORMER CORE BUILDING

3. WINDING

4. COIL ASSEMBLY

5. POWER ASSEMBLY

6. CASE FITTING

7. INSULATION SHOP

8. TESTING

9. DISPATCH

10. REFERENCES

CONTENTS

BHEL, Bhopal established in 1964, is an integrated power plant

equipment manufacturer and one of the largest engineering and

manufacturing companies in India in terms of turnover.

It has 15 manufacturing divisions, two repair units, four regional

offices, eight service centers and 15 regional centers.

It has been acquiring and adapting some of the best technologies

from leading companies in the world including General Electric

Company, Alstom SA, Siemens AG and Mitsubishi Heavy

Industries Ltd.

INTRODUCTION TO BHEL BHOPAL

a) Block 1A :- Fabrication

b) Block 1B :- Hydro Turbine, Tanks

c) Block 2 :- Electrical Machine

d) Block 3 :- Transformer Manufacturing, Capacitor & Bushing

e) Block 4 :- Switchgear, Control gear

f) Block 5 :- Foundry Division

g) Block 6 :- Steam Turbine

h) Block 7 :- Factory Store

i) Block 8 :- Coils & Insulation

j) Block 9 :- Traction motor block

k) Block 10 :- Lamination Cutting

BLOCK DISCRIPTION

POWER TRANSFORMER CONSTRUCTION

Fig: Block Diagram representation of Transformer Construction

TRANSFORMER CORE BUILDING

Following steps are involved in power transformer core

construction:

1) Cutting & punching of CRGO

2) Stacking of CRGO

3) Fiber Glass End Frame insulation

4) Insulated Bolting of End Frame.

Fig: Cutting & punching of CRGO Fig: Stacking of CRGO

Fig: End Frame insulation & End Frame bolted Fig: Erecting of Core

WINDING

TYPES OF WINDING MACHINESWinding Machines are of two types:

1) Horizontal Winding machines

2) Vertical Winding machines

Fig: Horizontal Winding machines Fig: Vertical Winding machines

TYPES OF WINDINGS:1) Spiral Winding (L.V.L.C.)

2) Helical Winding (L.V.H.C.)

3) Disc Winding

4) Interleaved Disc Winding

Fig: Helical Winding

Fig: Interleaved Disc WindingFig: Disc Winding

The various types of conductors used in coil winding are

1) CTC (Continuously Transposed Conductor)

2) PICC (Paper Insulated Copper Conductor)

3) BPICC (Bunch Paper Insulated Copper Conductor)

TYPES OF WINDING CONDUCTORS

Fig: CTCFig: PICC Fig: BPICC

COIL ASSEMBLEY

Coil Sequence

L.V. Coil is placed adjacent to the CRGO steel core and

H.V coil outside, in order to minimize the amount of

insulation required.

While assembling the different coils (i.e. Tap coil, L.V. Coil

& H.V. Coil) tap coil can be placed in either of three positions

depending upon the length of tap coil i.e. if tap coil is small it

is placed inside of LV coil, if it is medium then between LV &

HV coil, and if large then outside of HV coil.

The coils are specified in the design may be of following types

on the basis of operating voltage:

1) L.V. Coil Winding

2) H.V. Coil Winding

3) Tap Coil Winding

Fig: Vertical Winding (HV)Fig: Horizontal Winding (LV & Tap)

Fig: Coil Assembly

Fig: Oven Baking

Fig: Hydraulic Press

POWER ASSEMBLEY

Core - Coil Assembly 1a) Unlatching of core

b) Fitting of bottom insulation

c) Core coil assembly as per drawing/electrical specification

Core - Coil Assembly 2a) Fitting of top insulation

b) Relacing of core

Terminal Gear Mounting 1a) Crimping & Brazzing

b) Insulation Wrapping

c) OLTC Connection

d) Electrical Circuit manufacturing

Terminal Gear Mounting 2a) Vapour Phase Drying

b) Servicing.

Steps involved in Power Assembly are :

Fig: Unlatching of core

Fig: Core coil assembly as per drawing

Fig: Relacing of core

CORE COIL ASSEMBLY 1 & 2

Fig: Electrical Circuit manufacturing

Fig:Vapour Phase Drying of core & winding alone

Fig: Vapour Phase Drying of Transformer

CASE FITTING

1) CT connections & Feed positions

2) Conservator

3) Bushing Connections

4) Magnetic Oil Gauge

5) Oil Temperature Indicator

6) Buchholz Relay

7) Radiator

8) Breather

9) Control panel

Case Fitting involves connecting accessories of transformer, these

accessories include following :

1. Transformer tank

2. High voltage bushing

3. Low voltage bushing

4. Cooling fins radiator

5. Cooling fans

6. Conservator tank

7. System ground terminal

8. Drain valve

9. Breather

10. Oil temperature gauge

11. Current xmer terminals

12. Control panel

Fig: Parts of Transformer

INSULATION MATERIALS

Fig: Press Board Material

Fig: Udel Wood

Fig: Bushing Insulation

Fig: Fiber Glass Material Fig: Oil InsulationFig: Bakellite

Items made up of PBM:-

1) Former Base Cylinder

2) DOF Separator

3) T-Block

4) Static Ring

Items made up of Udel Wood:-

1) T-Spacers

2) Full ring segment

3) Half ring segment

4) Shunts

Fig: Items made up of Udel Wood

Fig: Items made up of PBM

1) TESTING TO THE BRITISH STANDARDS

2) ROUTINE TEST FOR TRANSFORMER AS

PER IS 2026

TYPES OF TESTS

Routine tests:1) Voltage ratio and polarity.

2) Winding resistance.

3) Short-circuit impedance and load loss.

4) Dielectric test.

5) No-load losses and current.

6) On-load tap-changer.

Type tests:1) Temperature rise test.

2) Lightning impulse test.

TESTING TO THE BRITISH STANDARDS

1) Dimensional Check

2) Winding Resistance Test

3) Short Circuit Test

4) Open Circuit Test

5) Induced Over Voltage Test

6) Separate Source Voltage

7) Insulation Resistance Test

8) B.D.V of Oil

9) Turns Ratio Test

ROUTINE TEST FOR TRANSFORMER AS PER

IS 2026

DISPATCH

After successful completion of testing, transformer is handed over

to dispatch sections. At this stage after checking oil leakage,

dismantling of all bushings, turrets etc. and covered with the

blanking plates and the tank is fitted with nitrogen gas and then

the transformer is dispatched to the concerned site.

There are generally three separate shipments made:

1) The main tank c/w core and coils,

2) The accessories that have been removed and packaged, and

3) The insulating oil.

Fig: Dispatch of power transformer

[1] Dr. P. S. Bhimbra, “Electrical Machines”, Khanna

Publications, New Delhi.

[2] D. P. Kothari and I. J. Nagrath, “Electrical Machines” , 3rd

Edition, TMH, New Delhi.

[3] BHEL , “Transformers” 2nd Edition ,Tata Mcgraw Hill

Education Private Limited.

REFERENCES

THANK YOU