The document outlines the construction and design considerations for transformers, focusing on core materials like crgo, winding types, insulation methods, and cooling systems. It details components such as bushings, conservators, and relays that ensure operational efficiency and safety of transformers. Additionally, it discusses the manufacturing processes and testing protocols essential for transformer quality assurance.

1. Prepared by:
Jimit Dhruv
Elect.Engg,Dept.
Valiya Institute Of Technology-Valiya

2. Introduction
 Core material:
 Basic material are Alloy Steel having main
content Silicon & carbon
 Which increases permeability & reduces losses

3.  HRS:
 HRS not used now a days
 As it has random direction &hard to measure
Magnetic properties
 CRGOS:
 CRGOS shows excellent Magnetic properties
 So CRGOS is more used

4. Core construction
 Due to Pulsating flux, core should be
laminated
 Transformer of larger size may forms in
cut “C” or cut “E” type.
 Types of Interleaving:
I. Simple Interleaving
II. Meter core Interleaving:
1)45 ˙
2) 33 ˙ /55 ˙ overlapping
 In 3-Ø Shell type transformer middle
winding is reversed
 If not then 73% more core is used
which leads in increase in over all cost

5. Transformer winding

6. Concentric
Sandwich
 Spiral: It is used 100
A& for low Voltage
Winding
 Mechanically very
strong  Sandwich: mostly used
 Helical :Intermediate for shell type transformer
range of current  Control leakage
 Suitable for LV winding
reactance
of large transformer  HV & LV are near so
leakage flux is reduced
 Cross-over: suitable of
 mmf of each section is
current not exceeding 20
same.
A
 Use for HV winding of
small transformer
 Continuous disc: no of
turns wound radially over
one another
 separated by spacers
 HV winding
 Mechanically strong

7. Insulations
Two main kinds of Insulations:
1. Major Insulation:
 Insulating cylinder between LV & core
 Also between HV & LV
 Insulating barriers between limbs, coils & core
yoke
 Oil impregnated paper used as it has high
dielectric strength
2. Minor Insulation:
 Insulation between
individual turns & between layers
 Conductor Insulation: paper&cotton
 Air insulated Transformer
insulation used is glass tap

8. Bushing
 Up to 66kv non-condenser bushing are used is
porcelain & oil filled
 Above 66kv condenser bushing are used for
economic reasons.
 Condenser type bushing: It is formed by
inserting Aluminum foiled layers into a paper
winding at predetermined radius.
 “Partial capacitance”
 In outdoor substation the
bushing are covered by a
porcelain rain shade

9. Tapping
 Main two location:
1. Inside Tank
2. Outside Tank
 Considered as integral part of transformer
Tapping operation
(1)On load (2)Off load
tap changer tap changer
 Tapping is terminated just bellow oil level
 External handle
 Taping is done on HV winding
 Provided in middle (axial & radial force)

10. Transformer Tank
 Plain sheet steel
Tank
 Tube Tank
 Corrugated Tank
 Radiator Tank
 Tank with separate
coolers

11. Conservator
 What is Conservator ?
 The expansion of oil from Transformer
tank takes up in Conservator
 When oil contracts, air from
atmosphere enters in Conservator .
 Risk of contamination of oil in transformer
 Breather valve is mounted to avoide
moisture
 Breather contain silica in it

12. Buchholz Relay
 Operation:
 Gas operated relay
 AT the time of fault to maintain the continuity
of the supply
 Fault detected particularly in incipient stage ,
major fault can be avoided
 Which is placed between conservator
and transformer tank

13. Transformer oil
 Double purpose :
 ie cooling & Insulating
 Permittivity is 2.5
 As per I.A.S breakdown strength of oil
used must be 50kv RMS
 Major disadvantage is sluging
 To overcome this, synthetic oil is prefered
 One of the e.g is Chlorinated dephenyl is a
synthetic oil its permittivity is 4.5

14. WORKSHOP(TPT DEPT.)
WINDING SHOP
CORE & ACTIVE PART
FINAL ASSEMBLY
QUALITY TEST
FINAL TESTING

15. WINDING SHOP
 TYPES OF WINDING
i. NORMAL WINDING
ii. INTERLEAVE WINDING
iii. TERITARY WINDING
ROTARY
HORIZONTAL HELICAL
K-
MACHINES TRANSPOSITION
TYPE
CONTINUOUS
VERTICAL
DISC
• End Rings & shielding for prevention purpose

16.  Conductor Insulation:
1. Precompressed press board insulation(CRIP
PAPER)
2. Craft paper
3. Also spacers as insulation
 Moisture Control
 Winding Auto Clave: Uses temp. of 110º
C to 130º C and Vacuum of about 0.4 to
0.5 mbar.
 Insulating Oven : Uses Heating Only
 Pressure Machine
 Brazing Machine with use of SILPHOS
ALLOY
 Post Insulation

17.  PROCEDURE:

18. CORE & ACTIVE
PART
 ACTIVE PART
 C.R.G.O. STRIPS
 1-STRIP HAS WIDTH OF 0.27 mm
 COIL OR WINDING ASSEMBLY
 PROCEDURE:
 Manufacturing of LIMB
 Core Insulation
 Removal of TOP FRAM for Coil assembly
 Winding insulation detail
 TOP YOKE FILLING
 VAPOUR PHASE OVEN
 HV & LV leads from top & bottom to the bushings
 REGULATING COILS to the tap changer

19. FINAL ASSEMBLY
 Installation of active part and assembly of
accessories
 TRANSFORMER TANK
• JOINED AT
BELL TYPE BOTTOM
SIDE
• JOINED AT
CONVECTIONAL
TYPE
UPPER
SIDE

20.  ACCESSORIES:
 Blanker : Leakage of oil & Radiators
adjointment
 Buchholz Relay: To trip the transformer
 OSR (oil serge relay): To indicate the level
and quality of oil
 MOLG(magnate oil gage): It indicates the
level of oil in the conservator
 Breather Valve: Provide dry air using silica
gel and have air seal of neoprene
 Cooling Equipment: Generally for cooling
of oil in a tank
1. Radiators
2. Thermosyphan

21.  Method of Cooling:
i. ONAN
ii. ONAF
iii. OFAF
iv. For very high temp using HEAT
EXCHANGER
 CT(Current Transformer):Two
purposes;
1. Winding temp indicator (WTI)
2. Oil temp indicator (OTI)
 BUSHINGS: The leads from top and
bottom of the winding are brought out to a
length of few cm only and the outdoor
terminal of the transformer are provided
by bushings

22.  PROCEDURE
 Vacuuming of Tank(up to 0.3 mbar) for about
24hrs to 36hrs
 The Leak Rate Test with the use of water & air
 Oil Test which includes BDV & PPM
 Oil Filling
 After the IMPREGNATION TIME the whole
accessories are to be attached.

23. QUALITY TEST
 ANALYSIS WITH “SIGMA CARD”
 Sigma card includes below required data
 Design
 Process Time
 M/C size specification
 Process of manufacturing
 Dimension specification
 Testing specification
 Information about control points

24. FINAL TESTING
ROUTINE TESTS TYPE TESTS
NO LOAD TETS
TEMPRETURE
TEST
LOAD LOSS
INSULATION IMPULSE TEST
TEST
CAPACITANCE & ZERO SEQUENCE
TAN δ IMPEDANCE
TEST
SEPARATE
SOURCE HARMONIC AND
NOISE LEVEL
TEST
INDUCED OVER
VOLTAGE
WINDING TEST
VOLTAGE RATIO

25. CT (CURRENT TRANSFORMER)
 Generally CT is use for the below four
purposes:
 Measurement of Current
 Measurement of Power
 Isolation between High voltage and Low Voltage
 Inputs to Relays & Protection Systems
 PROCEDURE OF CURRENT
TRANSFORMER:
 CO NDUCTORS USES :ALUMINIUM OR
COPPER(HIGH CURRENT RATING)
 In the manufacturing of the primary winding or
protection core there will be the creation of the
capacitance as below.
 GRADING & SUB GRADING.
 MAIN GRADING HAS WRAPPED
ALUMINIUM FOIL & CRIP PAPER
 AT 300MM DISTANCE PERFORATED ALU.
FOIL (400MM) AND CRIP PAPER.
 SIMULTANEOUSLY INSULATION MAKE
CAPACITANCE

27.  Quartz in CT
 Reduces the quantity of oil
 Provides mechanical strength for the
conductors
 Improves the quality of oil by absorbing
moisture
 Being a bad conductor of heat, it allows slow
heating /cooling of the CT.
 Finally expansion tank is attached and after
that evacuation of oil and gas filling will be
there .
 There is also one imp term is D3 point which
is also called the earth point.

28. Thank You