This document summarizes a seminar presentation on different types of transformers used in a 210MW thermal power plant. It describes 7 main types of transformers used: generator transformer, station transformer, distribution transformer, unit auxiliary transformer, instrument transformer, rectifier transformer, and neutral ground transformer. For each type, it provides key specifications like voltage ratings, cooling type, and functions. The document also covers transformer components, working principle, cooling systems, and maintenance.

1. A SEMINAR ON
“Different Types Of Transformers Used For
210MW Unit Thermal Power Plant”
PRESENTED BY :
VAIBHAV BHOPE PRITAM BIJWAL
SUMIT VINCHURKAR SANTOSH
VIJEKAR
NIKHIL WANDHARE NIKHIL SHRIWAS
AKASH SHEGOKAR CHETAN ANGARWAR
VIKASH SINGH AKSHAY
SAHARE

2. Overview
 Introduction
 Single line diagram
 Classification of transformer
 Parts of transformer
 Cooling system
 Protection of Transformer

3. TRANSFORMER
 “Transformer is a static device which transform electric power of one circuit to
another circuit without changing its frequency.”
 Working Principle of transformer :
The working principle of transformer depends upon Faraday’s law of
electromagnetic induction. Actually mutual induction between two or more
winding is responsible for transformation action in an electrical transformer.
 Faraday’s laws 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".

4. Single line diagram

5. Types of Transformers used in
210MW unit
1) Generator Transformer 2) Station Transformer
3) Distribution Transformer 4) Unit auxiliary Transformer
5) Instrument Transformer 6) Rectifier Transformer
7) Neutral ground Transformer
8)Transformer used for general purposes and for different processes.
i ) Welding Transformer
ii ) Specially designed Transformer used for X ray, Radio,
Telecommunication, T.V., High frequency heating, and Industrial
heating for different processes.

7. Generator Transformer Rating
 MVA = 240 MVA
 Primary Side = 15.75 KV (d)
 Secondary Side = 400 KV (Y)
 Oil Qty = 43 KL
 Cooling = OFWF
 Vector Group = Yd11
 %Z = 11.90

8. Functions
 This is step up transformer of high voltage capacity.
 This is connected after the generator to step up voltage
from 15.75kv to 400kv.
 The main function of this transformer is to step up
voltage so as to reduce transmission losses, line drop
and increases Transmission efficiency .

10. Station Transformer Rating
 MVA = 40 MVA
 Primary Side = 220 KV (Y)
 Secondary Side = 6.6 KV (Y)
 Oil Qty = 30 KL
 Cooling = ONAF
 Vector Group = Yy0
 %Z = 11

11. Functions
 Transformer at the generating station is required for
starting of the generating units when they are either
newly constructed or taken of the bar for overhaul.
 These Power transformers are called station
transformer, which receives power from the grid and
feed power-to-power station distribution system.

13. Unit Auxiliary Transformer Rating
 MVA = 20 MVA
 Primary Side = 15.75KV (d)
 Secondary Side = 6.6 KV (Y)
 Oil Qty = 6.4 KL
 Cooling = ONAF
 Vector Group = Dy1
 %Z = 9.0

14. Functions
• The Purpose of Unit auxiliary Transformer is to feed power to generator
auxiliaries of that unit
• These transformers are connected to generators and are used as stepping
down transformers. The HV side transformer voltage corresponds to the
voltage of the generating unit and the LV side voltage is stepped down to
6.6KV
• Rated KVA of Unit Auxiliary Transformers is approximately 15% of the
generating rating
• Usually these transformers are outdoor transformers
• One Unit auxiliary transformer is present for every generating unit.

15. • A Rectiformer is a rectifier and
transformer designed and built as a
single entity for converting alternating
current into direct current.
• It is piece of power systems
equipment rather than an electronics
component.
• Rectiformers are used for supplying
power to different field of ESP
(electrostatic precipitator).

16.  For metering and protection to maintain instrument accuracy.
 For sensing H.T. side current at the secondary side
 Used in protection relay, trip coils and pilot wires.
 Used in current power measurement, temperature sensing etc.
Current Transformer (CT) Potential Transformer (PT)

20. Distribution transformer
 This is step down transformer connected according to
applications such as boiler ,turbine , station service
board.
 The main function of this transformer is to provide
convenient amount of power in the various boards.

22. NGT
 The subject of grounding covers the problems relating
to the conduction of electric current to the earth and
through the ground. The earth rarely serves as a part of
the return circuit, being used mainly for fixing the
potential of circuit neutrals.
 The ground connection improves service continuity
and protects lives and equipment.

23. (a) Arcing rounds are reduced or eliminated.
(b) The neutral grounding stabilises the neutral point.
(c) By employing resistance or reactance in earth connection, the earth fault current can
be controlled.
(d) The over voltage surge due to lightening are discharged to earth hence less damages
to the equipment. Useful amount of earth fault current is required to operate earth fault
relay.
(e) Improved service reliability due to limitation of arcing ground and prevention of
unnecessary tripping of circuit breakers.
(f) Life of eqipment, machines and installation is improved due to limitation of
voltages.
(g) Greater safety to personnel and equipment due to operation of fuses or relay on
earth fault and limitation of voltages. Hence it is economical to ground neutral point.
Advantages of Neutral Grounding
Transformer

24. Constructional Features
 Main Tank
 Laminated core
 Core winding
 Bushing
 Tap changer
 Conservator
 Breather
 Explosion vent / Pressure relief valve

34.  Cooling system is required for transformer to take away the heat generated in
transformer due to losses and maintaining insulation healthy.
 Cooling system of transformer is provided by considering design and KVA rating of
a transformer. Cooling system of transformer is as follows.
i. Air natural cooling system.
ii. Oil natural cooling system with or without radiator.
iii. Cooling of transformer improved by force airflow by blowers/Air blast by fans
iv. Oil forced natural cooling system (OFN): - circulation of oil by pump to radiator,
which has natural cooling.
v. OFB : Forced oil circulation of oil by pump to radiator, which has force, cooled by
air blower.
vi. OFW : Forced circulation of Oil through oil cooler and water-cooling is by water.
 Generally Oil temp is maintained in between 45 to 55 Dc. & Winding temp in
between 55to 80 °c.(depends upon insulation class)

35. Types of Cooling
ONAN ONAF

36. OFAF OFWF

37. Maintenance
 Transformer Oil Level Checking
 Breather condition monitoring
 Oil testing
 D. G. A.
 Oil Filtration
 Bushing Cleaning
 Drying Out (after 7 Yrs)