power and transformer and its usage all important topics covered all you need to know about power transformer

1. TATA POWER
PROJECT REPORT ON
AND OVERVIEW OF POWER
PLANT
And
TRANSFORMERS
SUBMITTED BY
NAME BRANCH INSTITUTE
SOMNATH CHATTERJEE EE M.I.T,BISHNUPUR , WB
Page No.1

2. ACKNOWLEDGEMENT:
Our report will remain incomplete if we do not mention the
efforts of those people who helped us in completing this
project.
Firstly we want to thank Mr. Binay Khalkho Manager-H.R.
and Mr. Deepu Minz H.R. Dept TATA POWER Jamshedpur
and the electrical department for letting us use the
department data and carry out the necessary field work.
We would like to express our gratitude to Mr.G.P.Shastry,
Department Head, EMD, for his support, encouragement
and all the technical help without which the completion of
this project would have been impossible.
We are also deeply indebted to Mr. Soumendra Mandal,
EMD Project coordinator, whose technical input, stimulating
suggestions and encouragement helped us in completion of
report and provided us with practical on field knowledge of
the I
We also want to thank my co-trainees from various colleges
who supported us in work. Their presence made our stay at
TATA POWER a pleasant and learning experience in all
aspects of life.
Page No.2

3. CERTIFICATE
This is to certify that Mr, Somnath Chatterjee ,student of bachelor of technology
in E.E of 6th sem from MALLABHUM INSTITUTE OF TECHNOLOGY ,
BISHNUPUR , WEST BENGAL has successfully done his vocational training at
TATA POWER CO. LTD. , JOJOBERA power plant , JAMSHEDPUR under my
guidance and successfully completed project on “OVERVIEW OF POWER
PLANT AND TRANSFORMER”.
MR. BINAY KHALKO MR. G.P SASTRI
Manager (HR) HOD (EMU DEPARTMENT)
MR. DEEPU MINZ MR. SOUMENDRA MANDAL
HR DEPARTMENT PROJECT CO-ORDINATOR
Page No.3

4. CONTENTS
Topic Page
* Introduction 6-7
1. Types of Transformer 8-9
2. Parts of Transformer 9
3. Overview of Buchholtz Relay 10-11
4. Characteristics Of Transformer 12-13
5. Test for checkup of Transformer 13-14
6. Test for maintenance of Transformer 14-15
7. Layout of Transformer 15-20
8. Layout of plant 20-21
9. Switchyard 21-24
10. De-mineralizing Plant 24-26
11. Boiler and Turbine Area 26-31
12. Generator Producing Alternating current 31-32
13. Mini Project on Power Transformer 33-34
14. Coal Handling Plant 34-36
15. Conclusion 37
Page No.4

5. The Basic layout of Jojobera Plant and the main area of
operation
RAW MATERIAL
(COAL) CHP
BOILER AND
TURBINE
ELECTROSTATIC
PRECIPITATOR
FLY ASH
AS SIDE
PRODUCT
TRANSFORMER
YARD
SWITCHYARD
TO DIFFERENT
PLACESBY
TRANSMISSION
LINES
Page No.5

6. • Tata Power is an Indian electric utility company based in Mumbai; and is part
of the Tata Group.
• The firm started in 1911 with its first hydroelectric project in 1915.
• The overall installed electricity generating capacity is 8500 MW.
• The major power plants are
• Mundra Ultra Mega Power Plant. (It’s a super critical power plant. With
overall capacity of 4000 MW {#5* 800 MW Units} )
• Trombay Thermal Power Station
• Maithon Power Plant
Jojobera Power plant
• The Core Business operations of the firm are
1) Holding Fuel Assets
2) Logistics related operation
3) Power generation
4) Transmission distribution & trading
The new technologies/methods used by Tata Power in its power plants
Introduction of “Pumped Storage Unit” (used in hydro power plants, to cater the
demands @ Peak hours)
Page No.6

7. Use of Gas insulated Switchgear and plants having “Fly Ash Aggregate”
Technology using ESP [Electrostatic precipitator]
JOJOBERA Plant
• The Plant is a JV (Joint Venture) of Tata Power + Tata Steel.
• The Electricity Generating Capacity of the plant is 547.5 MW.
• It operates with a total of 5units
Unit Generating Capacity G.P.V (Generating Point
Voltage)
Unit#1 67.5MW 10.5KV
Unit#2 120MW 11KV
Unit#3 120MW 11KV
Unit#4 120MW 11KV
Unit#5 120MW 11KV
About the plant
Main customer- Tata Steel
Secondary customers: TELCO, Tata Cummins, Lafarge cement, JSEB
Plant Load Factor (PLF) : The Jojobera plant has a PLF of 96-98%
Bus sectionalizers: 4
Bus couplers: 3
Total bus sections: 6
Page No.7

8. Major types of transformer used @ JOJOBERA Plant
1.Generating Transformer (G.T’s)
2. Station Transformer (S.T’s)
3. Unit Auxiliary Transformer apart from some other form of
transformers
G.T
Outdoor type
Employed for stepping up the voltage for transmission of power.
@ Our plant it was
11kV/132kV
Rating of the G.T
is almost equal
to the rating of
the transformer
S.T
1) For supplying
power to plant
auxiliary loads @
the event of
startup.
2) It also
provides power
to the devices @
the event of any
external fault or
failure which
might occur for few minutes.
3) This design parameter is ‘Universal’ in nature & all the plants need to
have this design.
4) It is connected to the switchyard bus
Page No.8

9. UAT
1) Brings down the voltage level from 11kV/6.6kV
2) Main purpose is to feed the generator auxiliaries
3) Rating of the UAT is generally 15% of the generator rating.
Connected/Situated near the
G.T
Parts of a Transformer
1) CONSERVATOR
2) TANK
3) BUCHHOLZ RELAY
4) BREATHER
5) SILICA JEL
6) OIL LEVEL SCALE
7) PRIMARY WINDING
8) SECONDARY WINDING
9) DRAIN VALVE
10) PORCELIN BUSH
11) RADIATOR
12) FANS
Apart from this there are two additional parts used solely for the purpose to check
the Oil level namely i) MOG (Magnetic Oil Gauge) ii)Glass Gauge. These gauges are
placed on the either side of the conservator where oil is placed, the glass gauge is
used for checking the oil level by simply seeing the oil through the glass screen (A
rough indicator of oil Left). The MOG is a more accurate indicator of the oil level as it
indicates the oil left and the temperature condition.
Conservator
It is a type of tank, used to
help oil filling this is situated upper portion of the
power transformer. Mainly these are cylindrically
shaped.
Page No.9

10. Tank: It is a container used to keep
windings (both) and cooling oil.
BUCHHOLZ Relay
It is a gas-actuated relay installed in oil immersed transformers for protection against
all kinds of faults. It is a protecting device used to
protect our transformer windings. This is a double ended
device one end is connected to conservator other is
connected to tank. It has a two cup arrangement. In general it is a Slow Acting
Device.
Working
1. In case of incipient faults within the
transformer, the heat due to fault causes the
decomposition of some transformer oil in the
main tank. The products of decomposition
contain more than 70% of hydrogen gas.
The hydrogen gas being light tries to go into
the conservator.
Due to its two cup arrangement when the
fault level is low the 1st
cup arrangement is activated & the ‘Alarm circuit is switched
on’.
2. When the fault level is high the 2nd
Cup
Arrangement is activated & the ‘Trip circuit’
is switched ON. The oil in the main tank
rushes towards the conservator via the
Buchholz relay and in doing so tilts the flap
to close the contacts of mercury switch.
This completes the trip circuit. Another
important point regarding the Buchholz relay
is that it should be placed at a small tilt
between the two tanks @ an angle of (5-7)
degree. The
BREATHER-Breather is a device used for
absorbs the
moisture content of an oil and sucked air
SILICA GEL- It is a chemical material Namely ‘Silica
Gel’ (Si02)
it is situated inside the Conservator. The main
Page No.10

11. function is to absorb the moisture. There is a physical color change during the
process form Blue to Pink.
It can be regenerated by re-heating @ 200 degree Celsius for 5-6 hours. By using
this process it can be regenerated a maximum of 3 times.
OIL LEVEL SCALE - this is an ordinary part situated on
the side of the conservator for proper oil checking oil
tank wants a specific amount of oil
PRIMARY WINDING - in the case of power
transmission
primary windings are the main element external
connection
from the power is connected to this winding
SECONDARY WINDING - this is a another winding for
reducing power (in the case of step down purpose)
DRAIN VALVE - this valve is used for taking damaged
oil from the oil tank for the proper oil collection this
valve is situated under the oil tank.
PORCELIN BUSH - This is an outer unit, this is used to
prevent unwanted leakage of electricity
RADIATOR - This device is used to cooling oil
There is also a use of another protective device called as ‘ON-Load TAP Changer’
(OLTC ). The OLTC is always connected towards the High-voltage side because the
current is low in that side and is more easy to control through a lesser value of
current.
It is mainly used for changing the voltage level of the Secondary side of the
transformer.
In our Jojobera plant the OLTC has rated value of 7873A.
*For Small transformers we can also use Off-Load Tap Changer is used.
Apart from these safety devices the “TRANSFORMER OIL” is also a very important
component of the transformer.
“LIKE Blood is for Humans; Oil is for Transformer”
The important functions of the Transformer Oil is
Page No.11

12. 1. Acts an electrical insulation
2. Acts as a coolant to dissipate Heat Losses
Transformer Oil will be obtained by fractional distillation and subsequent treatment
of crude oil. Transformer Oil consists of organic compounds namely paraffin,
naphthenes, aromatics and olefins. All these compounds are hydrocarbons, so
Transformer Oil is a pure hydrocarbon mineral oil.
Transformer Oil has following Characteristics:
 Colorless
 Low Density
 Low Viscosity
The various Physical & Electrical properties of the transformer are
Physical Properties
Moisture Content expressed in (ppm by wt. or mg/kg).For a good transformer oil the
moisture content should be low.
Interfacial Tension (is the measure of molecular attractive force between the oil and
water molecules at their interfacial level.) By testing for Interfacial tension we can
determine the soluble polar contaminants present in the oil
Flash Point (temperature at which oil gives so much vapour that this vapour which
mixes with the air forms an ignitable mixture and gives momentary flash) good
Transformer Oil Flash Point should be higher (145 Centigrade).
Viscosity It should be very low for good quality of transformer Oil.
Pour Point( The temperature at which transformer oil will just flow under the
prescribed conditions) Pour Point should be low for good transformer oil.
Electrical Properties
Electrical Breakdown Voltage Strength (is the Voltage at which breakdown occurs
between the two electrodes when the oil is subjected to an electrical field under
prescribed condition). It is a basic parameter for insulating design of the transformer
system. Transformer Oil should have higher breakdown Voltage strength
Resistivity good Transformer Oil resistivity should be high. Lower Resistivity of
Transformer Oil indicates the presence of moisture and conductive contaminating
agents.
Page No.12

13. Due to the presence of Moisture there is a chance of 1. Insulator being damaged 2.
Spark might occur
Dielectric Dissipation Factor (Loss angle is an important property of dielectric oil. In
ideal dielectric material the phase angle between the voltage and current is 90.)
However due to certain impurities, leakage current the Phase angle is less than 90.
It’s the sine of the loss angle. Dielectric Dissipation value should be low for good
Transformer Oil.
For checking these Properties and regular checkup of transformer oil. The plant
authorities use two major tests for this:
1. DGA test (Dissolved Gas Analysis Test)
Insulating materials within transformers & electrical equipment break down to
release/liberate gases within the unit. The distribution of these gases can be
related to the type of electrical fault & the rate of gas generation relates to the
severity of the fault.
DGA usually consists of Sampling the oil & sending the oil sample to
laboratory for analysis. Jojobera Plant sends the oil sample for testing at
Durgapur for DGA analysis.
It is a new & efficient oil testing method & is only possible at few places; this
gives a detailed comment on the fault. Ex : Methane level is high (Core
Problem)
2. BDV Test (Break down voltage test)
It tests the dielectric strength of the transformer. It is desired to have a higher
value of BDV for a good transformer. For a 150 MVA of Transformer the
desired value of BDV is 70KV.
Transformer Rating of the G.T’s used in the plant is 150 MVA; only G.T#1 has
a rating of 90 MVA.
Page No.13

14. General Rating of the transformer : 90MVA|120MVA|150MVA
TEST
The major tests employed for the maintenance/Repair of the Transformer in
the plant is
1. Megger Test (Insulation Resistance Test)
The IR test or Megger test is a spot insulation test used to check the
‘Insulation Level of the windings of Motor’. The IR test is done ON-SITE as a
final test for the equipment insulation & to confirm the reliability of the circuit.
The advantage of the IR test is it’s non-destructive nature since it uses DC
voltage.
Three different types of DC voltage levels are used for the test.
i)250 V ii)500V iii)1000V
It is connected between the Body & Winding. The measured resistance is
generally expressed in terms of Mega-ohms.
 Thumb Rule For Megger Test
Minimum rating of Megger value [kV (Value) + 1 ]
Ex: for a 6.6 kV Motor the Required value of Megger should be 7.6 Mega-
ohms.
To improve the low value of megger test we use heating in Halogen
technique.
LT motor Name-Plate Analysis
Ex:
KW-15
Ampere-27
Rpm-1430
Frame Size : 160 L
Duty : S1
IP: 55
As we know, KW is the rated Power of the device & Ampere is the rated
current of the device. * Thumb Rule for Ac-Motors [KW rating x 1.7=Ampere
Rating]
The Frame size is the size of the metal frame used; it comes in 3 variants.1.
S-short 2. L- large 3. M-medium
Duty refers to the mode of operation of the motor, in what way is it operated.
There are 4 types of duty available for Motors.
Page No.14

15. S1- where it is used continuously & non-stop. Very less time is available for
the device to heat up & cool.
S2 & S3- where the device has a Start-Stop operation, not in continuous use.
S4- Long period of Start-Stop Operation. HOIST operation.
IP-(Ingress Protection) This rating is used as a protection measure for the
motors used in plant. It depends on the requirement as whether the device in
Indoor conditions or Outdoor conditions
(LIQUID) 1 2 3 4 5 6 7
.
It tells us how resistant it is to dust & water. It specifies the environmental
protection of the device to the surrounding enclosure on a scale of (1-7).
Apart from this we use certain other tests also for the transformer.
Tan-Delta Test ( Improved version of Megger test)
The average life of a transformer is (25-30 yrs)
Important components/Devices used in
the layout of Transformer line @ the
Switchyard
1. Circuit Breaker: A circuit breaker is a device that detects the fault
condition or trip & interrupts the current flow.
Method of Control & Operation
S 1
O 2
L 3
I 4
D 5
Page No.15

16. A circuit breaker incorporates manual (or remote control) as well as automatic
control for switching functions. The manual control is employs relays and
operates only under external fault conditions.
A circuit breaker essentially consists of fixed and moving contacts, called
electrodes. Under normal operating conditions, these contacts remain closed
and will not open automatically until and unless the system becomes faulty.
When a fault occurs on any part of the system, the trip coils of the circuit
breaker get energized and the moving contacts are pulled apart by some
mechanism, thus Opening the circuit.
Types of Circuit Breaker:
1. Oil based C.B: uses insulating oil for arc extinction.
2. Air-Blast C.B: high pressure air-blast is used for arc extinction.
3. Sulfur Hexafluoride C.B: SF6 gas is used for arc extinction.
4. Vacuum based C.B: Vacuum is used for arc extinction.
Oil Based C.B: The insulating oil (e.g., transformer oil) is used as an arc
quenching medium. The contacts are opened under oil and an arc is
struck between them. The heat of the arc evaporates the surrounding oil &
dissociates it into a substantial volume of gaseous hydrogen gas @ high
pressure.
Advantages:
1. It absorbs the arc energy to decompose the oil into gases which have
excellent cooling properties.
2. It acts as an insulator and permits
smaller clearance between live
conductors and earthed
components.
3. The surrounding oil presents
cooling surface in close proximity
to the arc.
Disadvantages:
1. It is inflammable and there is a
risk of a fire.
2. It may form an explosive mixture
with air
3. The arcing products (e.g.,
carbon) remain in the oil and its
quality deteriorates with successive operations. This necessitates
periodic checking and replacement of oil.
Page No.16

17. SulphurHexafluoride C.B : It is one of the most widely used C.B. In such circuit
breakers, sulphur hexafluoride (SF6) gas is used as the arc quenching medium. The
SF6 is an electro-negative gas and has a strong tendency to absorb free electrons.
The contacts of the breaker are opened in a high pressure flow of SF6 gas and an
arc is struck between them.
Construction :
It consists of fixed and moving contacts enclosed in a chamber (called arc
interruption chamber) containing SF6 gas. This chamber is connected to SF6 gas
reservoir. When the contacts of breaker are opened, the valve mechanism permits a
high pressure SF6 gas from the reservoir to flow towards the arc interruption
chamber.
Advantages : Due to the superior arc quenching properties of SF6 gas, the SF6
circuit breakers have many advantages over oil or air circuit breakers.
1. Due to the superior arc quenching property of SF6, such circuit breakers have
very short arcing time.
2. The SF6 circuit breaker gives noiseless operation due to its closed gas circuit
and no exhaust to atmosphere
3. There is no risk of fire in such breakers because SF6 gas is non-inflammable.
Disadvantages
1. SF6 breakers are costly due to the high cost of SF6.
2. Since SF6 gas has to be reconditioned after every operation of the
breaker, additional equipment is required for this purpose
For an ideal C.B the time for the action should be in the order of 50
msec’s & the tripping coil should have a less value of voltage as tripping is
more important to us. The tripping coil’s action should be done in very less
time.
Isolator : Isolator is a mechanical switch which isolates a part of circuit
from system as when required. Electrical isolators separate a part of the
system from rest for safe maintenance works.
Electrical isolators are classified into two categories i) Based on system
requirement ii) Based on the position in power system
On system requirement
1. Double Break Isolator
2. Single Break Isolator
3. Pantograph Isolator
Page No.17

18. Out of these three, the double break isolator is widely used in the plant
Operation Of Isolators :
Isolator must be operated when there is no chance current flowing
through the circuit. No live circuit should be closed or open by isolator
operation.
A complete live closed circuit must not be opened by isolator operation
and also a live circuit must not be closed and completed by isolator
operation to avoid huge arcing in between isolator contacts.
Isolators must be open after circuit breaker is open and these must be
closed before circuit breaker is closed.
Some special purpose Isolators are used which are provided with an
‘Earth Switch’.(89)
Earthing switches are mounted on the base of mainly line side isolator.
The earthling arms are so interlocked with main
isolator moving contacts that it can be closed only
when the main contacts of isolator are in open
position. Similarly the main isolator contacts can be
closed only when the earthling arms are in open
position.
It is mainly used for additional safety purpose.
Bus Coupler : It is a device which is used to couple one bus to the other
without any interruption in power supply & without creating hazardous arcs.
It is achieved by the use of circuit breaker & isolators.
Page No.18

19. The simple purpose of the Bus Coupler is ‘Load Sharing’. As there are two
buses used so in-case we transfer a load from Bus-A to Bus B.
At
Jojobera Plant a total of 3 Bus coupler is used.
Bus sectionalizer : The sectionalizer is a self-contained, circuit-opening device
used in conjunction with source-side protective devices, such as re closers or circuit
breakers, to automatically isolate faulted sections of electrical distribution systems It
is used in switchgear to divide the bus into two sections. It generally comes into play
during repairing process, where to maintain the continuity of service;1 section is off
using Bus sectionalizer while the other continues to operate.
At Jojobera plant a total of 4 Bus Sectionalizer is used.
It also is a combination of Circuit Breaker & Isolator.
CURRENT TRANSFORMER (CT)
Current transformer is used to measure current at reduced current as well as for the
protection of the system. It is mainly a step down current to known ratio. The primary
of this transformer consists of one or more turns of thick wire connected in series
with the line. The secondary consists of large number of turns of fine wire.
It reduces heavy current flowing in the element of a power system to low values that
are suitable for relay operation
Page No.19

20. Nickel iron is used for the construction of CT because it gives a good accuracy up to
5 times the rated current.
POTENTIAL TRANSFER (PT)
Potential transformer is mainly a step down transformer which steps down the
voltage to known ratio. It is used for protection as well as measurement of voltage in
the system. The primary of this transformer consists of a large number of turns which
provides measuring instruments and relays, a voltage which is known fraction of line
voltage.
With the help of these devices and their Sequential arrangement the Layout of the
plant is designed with different types of Feeder.
There is also significant use of Gravel for flooring in both the Switchyard &
Transformer yard .It is used to reduce the contact between the Human body
& the earth Surface. (As there is alarge static charge difference between the
earth surface & the Transmission Line wires )
Layout of the Plant
2 Buses are used (Bus A, Bus B).Bus A Is the Sale line (Operated by the
Unit#3).Bus B is the Non-sale Line. For the transmission a total of 9 lines
have been used
Each Line can carry up to 132 kV.
Line – 1: Golmuri
Line – 2: Golmuri
Line – 3: Golmuri
Line – 4: Main Ring Substation (MRSS – 4)
Line – 5: Blower House (TATA STEEL)
Line – 6: Bara, Sonari
Line – 7: Main Ring Substation (MRSS – 2)
Line – 8: Main Ring Substation (MRSS – 2)
Line – 9: Tata Growth Shop
There is a fixed network of Connection followed in the Switchyard, which is
Page No.20

21. [ Isolator-- Circuit Breaker –Isolator (29)—Current Transformer]
S.C rating for the transmission line network @ Jojobera plant is 40KA for 3 seconds.
All the lines are connected to a lightning arrester for safety purpose. C.T is
connected in parallel and P.T is connected in series.
All the control in the switchyard is also done through a digitalized system, where all
the action is controlled through a ‘Remote Controlled Panel’. The plant also uses
Micro-Controller based ‘CONTROL’ of the Transformers in the Switchyard.
SWITCHYARD
Switchyard is protected area
where all the switchgears and its
equipment are installed power
transmission. Switchgear is used
for switching, controlling and
protecting device. Switchgear
equipment is essentially
concerned with switching and
interrupting currents either under
normal or abnormal operating
conditions. Switchyard is hub for
electrical power sources,
Page No.21

22. transformers, remotely controlled arc snuffing breakers, metering devices etc.
Switchyard forms the integral part of any power plant. These power plants have their
main plant equipment integral controls as well as Plant
The G.T has 3 Bus Ducts coming from the boiler Side each for (R Y B) phase
connected into the Transformer.
S.T has Bushings at the top which is placed on a Turret C.T (Winding which is
spiral), also there is a network of pipes in which Hot Oil enters from the top & Cool
Oil is through the Bottom.
Apart from this to maintain an Emergency Cooling System, the plant uses a
‘DELUGE System’ through which water is transferred through a network of pipes
which is controlled by a Quartz Bulb.
When the Transformer is heated up suddenly or there is a fire , due to the sudden
increase in temperature the quartz bulb breaks and the water sprinkler circuit is
started. Due to the water flow the pressure changes & the main deluge Valve opens
and more water flows through the sprinklers.
For the control of action of FAN’s
GT#2, GT#3, and GT#4,GT#5
Make
Rating
Voltage 11/132KV
Cooling
HV
LV
ONAF ONAN
30MVA 55MVA
90MVA 55MVA
No Load Voltage
HV
LV
ONAF ONAN
133V 139V
10.5V 10.5V
Line Current
HV
LV
ONAF ONAN
373.8A 228.4A
4943.7A 3024.5A
Phase 3
Connection Y
Frequency 50Hz
Insulation level
HV
LV
ONAF ONAN
660KV 275KV
75KV 25KV
Weight (of oil)
(total)
30500Kg
116000Kg
Page No.22

23. Make BHEL
Rating 90/120/150 MVA
Voltage 11/132KV
Cooling
HV
LV
ONAF ONAN
30MVA 55MVA
90MVA 55MVA
No Load Voltage
HV
LV
ONAF ONAN
133V 139V
10.5V 10.5V
Line Current
HV
LV
ONAF ONAN
373.8A 228.4A
4943.7A 3024.5A
Phase 3
Connection Y
Frequency 50Hz
Insulation level
HV
LV
ONAF ONAN
275KV 650KV
28KV 75KV
Weight (of oil)
(total)
30500Kg
116000Kg
Specifications Of the UAT :
Make BHEL
Rating 11/6.6KV
No Load Voltage
HV
LV
11000V
6600V
Line Current
HV
LV
656.1/787.3A
1045.9/1255.1A
Phase 3
Vector group DdO
Cooling ONAF/ONAN
Impedance at normal temperature 8.76%
Impedance at extreme temperature 8.05%
Weight (of oil )
(total)
6265Kg
16500Kg
ST#1, ST#2, ST#3
Make BHEL
Rating 75MVA
Page No.23

24. Voltage 132/33/6.6KV
Oil quantity 32250 Lts
Cooling ONAF/ONAN
Connection HV – Star, MV – Star, LV – Delta
Vector group HV – MV: YNyno
HV – LV: YNd1
Insulation level
1.) Impulse withstand voltage
2.) 1 min. Power frequency
withstand voltage
HV MV LV
550 75 60
230 28 20
No load losses at rated voltage and
frequency
42 KW
Load losses at principal tap and rated
output
268 KW
Auxiliary losses 5.2KW (Max.)
Weight (of oil )
(total)
30500Kg
116000Kg
TRANSFORMERS AT JOJOBERA PLANT AND THEIR USES:
 UST’s are located in power plant to step down the voltage level from 6.6KV to
415V. The rating for this transformer corresponds to the rating of the auxiliary
load to be borne. Generally, these are stationed indoor and are dry type
transformers.
 Power at Jojobera plant of Tata Power is evacuated at 132KV
 33KV system supplies power to Lafarge cement plant, Tata Cummins and
TELCO. For each of the aforesaid units, there are two feeders of 33KV each.
To facilitate this is a 33 kV bus with two incomers and one bus couplers. Each
incomer is capable of bearing the full load.
 There are six 6.6 kV buses. All the HT motors, 6.6kV/440V transformers are
connected to the 6.6kV buses employ SF6 breakers. If the unit trips then all
the load gets transferred to the station transformer automatically.
 There are 14 415 V buses, all the 415V motors like ACW pumps, CCW
pumps, valves, blowers, AC’s are connected to the 415V bus system.
De-Mineralizing plant
Page No.24

25. The water used for Steam production needs to have certain properties & certain
chemical composition. The water used for this purpose should be without any
dissolved gas, suspended matter, metal Ions (Cation/Anion).
So to achieve that we use De-Mineralizing Plant where various methods/techniques
are used to produce this water.
Water has Two types of treatment
1.Primary Treatment
2. Secondary Treatment
Under Primary treatment the water is free from Turbidity (Transparency levels of
water), suspended particles & dissolved gases are removed, gases such as carbon
di-oxide, sulphur di-oxide, carbon mono oxide are present.
All These are treated and removed to certain level under primary treatment. Water
from primary treatment is called as CLPH (Clarified water pH). With a pH of (7.5-8).
The layout of the DM-Plant is as follows.
1. Contact Tank (Where water is collected from the river and stored and
coagulated using certain chemical compounds for further treatment.) followed
by
2. Pressure Sand Filter (PSF) where water is passed through Sand & Gravel
chamber under high pressure, where odor, color & turbidity is removed. The
Filter is composed of Sand & Gravel & the pressure is maintained @ 2.5-3
kg/meter cube.
3. Strong Acid Cation Exchanger : It is a process where the cations are
absorbed from the (CLPH) using Resins of the type [R-H]. Cations such as
(Sodium, Potassium, Magnesium, Calcium) ion are absorbed. It is a very fast
reaction and takes place in the order of few minutes.
4. De-gasifier : After the treatment from the Cation exchanger, the water is then
sent to the De-gasifier where the weak gases are removed by passing/forcing
Steam onto the water through which gases such as CO, oxygen etc are
removed owing to their low density.
5. Strong Base Anion exchanger: It is a process where the anions are absorbed
from the treated water using resins of the type [R-OH]. Anions such as
(Sulphate , Carbonate, Chloride) ions are removed. It also is a very fast
process.
The Resins used in these processes are regenerated periodically after a
period of 1-1.5 years. The Re-generation process is carried out by using
chemical agents such as HCl & Caustic Soda (NaOH)
Page No.25

26. Reaction carried out is
R-H + NaCl  R-Na + HCl
Now,
R-Na + HCl ---> R-H +NaCl
The Resin used for the treatment process is made up from Steryne & DVB (Di
Vinyl Benzene).
6. Mixed Bed Treatment : This is the final stage of the treatment where, the
CLPH water is mixed with two types of Resins with the main purpose of
Polishing the treated water.
After the whole treatment Process under the DM plant, the DM Water has the
following chemical properties:
1. pH : 6.8-7.2
2. Conductivity : 0.2
3. Silica : 20 ppm
4. Turbidity:0
5. Colorless & Odorless
The Capacity of the DM plant is up to 25-30 cubic meter per cycle & so the plant is
generally operational for up to 10 hours with the total storage capacity of 300 tons,
through SDM tanks.
BOILER AND TURBINE AREA
A boiler is defined as a closed vessel in which steam is produced from water by
combustion of fuel. Also defined as “A combination of apparatus for producing,
furnishing, or recovering heat together with the apparatus for transporting the heat
so made available to the fluid being heated and vaporized.”
The boiler used at our plant is mainly of the water-tube type.
Boiler mainly works on the principle of Rankine cycle.
RANKINE CYCLE
Rankine cycle is thermodynamic cycle derived from Carnot vapour power cycle for
overcoming its limitations. Carnot cycle cannot be used in practice due to certain
limitations. Rankine cycle has the following thermodynamic processes.
1 – 2: Isobaric heat addition
Page No.26

27. 2 – 3: Adiabatic
expansion
3 – 4: Isobaric heat
release
4 – 1: Adiabatic pumping
T – S, H – S and P – V
representations are as
shown below
Practical arrangement in
a simple steam power
plant working on Rankine cycle is shown
ahead.
Page No.27

28. Rankine Cycle is used for steam generation in Unit 1; while for the other units
we use Modified Rankine Cycle(Reheat cycle).
We use Modified Rankine cycle because:
i) Compensate for the enthalpy loss
ii) Efficiency increases
iii) Dryness factor increases
Boiler mountings:
 Water level indicator
 Safety valve
 High steam and low pressure safety valves
 Fusible plugs
 Pressure gauge
 Stop valve
 Feed check valve
 Blow of cock
 Manhole and Mudbox
Boiler accessories:
 Super heater
 Economizer
 Air preheater
 Feed pump
 N.B :- Boiler mountings and accessories may vary for different types of
boilers. Some of the boiler accessories and mountings are described below.
 Super Heater: It’s purpose is to super heat steam and is a type of heat
exchanger in which steam flows inside tubes and hot gases surround it.
 Economizer: It is also a heat recovery device in which feed water is heated
from heat available with exhaust gases. Thus hot feed water available from
economizer lowers the fuel requirement in combustion economizer also helps
in removal of dissolved gases by preheating of water and thus minimizes
tendency of corrosion and pitting.
 Feed pump: Feed pump is used for sending water into boiler at the pressure
at which steam generation takes place. It is generally of three types i.e.
centrifugal pump, reciprocating pump and injectors.
 Safety valve: It’s function is to prevent the steam pressure from exceeding a
limiting maximum pressure value. Safety valve should operate automatically
by releasing excess steam and bring pressure down within safe limits.
Page No.28

29.  Pressure gauge: It is used for pressure measurement. Pressure is
continuously monitored so as to avoid occurrence of over shooting of boiler
pressure, although safety devices to protect boiler against pressure rising
beyond a limit is provided but pressure gauges are also used for monitoring
pressure.
 Stop valve: It regulates the flow of steam from the boiler. The is generally
mounted on highest part of boiler shell and performs function of regulating the
flow of steam from boiler. Stop valve generally has main body of cast steel;
valve, valve seat and nut etc. are of brass.
 Manhole and Mudbox: Manhole provides opening for cleaning, inspection and
maintenance purpose. Mudbox is a collection chamber for collecting the mud.
 Water is added @ the lowest energy state i.e @ the Condenser state.
The chemical analysis of the water is obtained by the Chemical
treatment is Winding Temperature Indicator (WTI):
This device measures the LV and HV winding temperature. A winding
temperature indicator or WTI is also used as protection of transformer. The
basic operating principle of WTI is same as OTI. But only difference is that
the sensing bulb pocket on transformer top cover is heated by a heater coil
surrounded it. This heater coil is fed by secondary of current transformers
associated with transformer winding. Hence the current through the heater
coil is directly proportional to the electric current flowing through
transformer winding.
done By Dosing in Boiler & Pump Section.
High Pressure Dosing (HP dosing) : TSP +DSP (Tri sodium phosphate + Di sodium
phosphate)
Low Pressure Dosing(LP dosing) : Ammonia + Hydrazine.
The boiler is mainly used for Combustion process where fuel is used. Combustion
mainly requires Fuel & Air for burning.
The Fuel used for the combustion process is the main fuel which is Coal +
secondary fuel Light Diesel Oil (LDO).
Steam generation is done in a radiant reheat, wet circulation, single drum, direct
corner field fitting burners and top supported type boiler. Main auxiliaries are:
 Super heater section
 Re heater section
 Draught section
Page No.29

30.  Fuel firing section
The steam parameter of the formed steam is as follows :
For Unit#1
1. Pressure : 90 bar
2. Temperature : 510 Celsius
For Unit#2 & others
1. Pressure : 120 bar
2. Temperature : 535 Celsius
The Major Boiler Auxiliaries used along with the boiler are
1. PA Fan : The function of the PA fan is to transfer the Pulverized Coal
(Crushed Coal) from Coal Mill to the furnace to dry coal in coal mill &
also to attain the pulverized coal. It also maintains powdered coal.
2. ID Fan : To extract fuel gas from the furnace, mainly used for
extracting the remains from the ESP & to send out from the chimney.
3. FD Fan : Supplies secondary air to the furnace to assist in
Combustion.
TURBINE AUXILLARIES:
A steam turbine is a prime mover in which rotary motion is obtained by the gradual
change of momentum of the steam. In a steam turbine following are the main parts:
 The nozzle in which energy of high pressure is converted in to kinetic
energy, so that steam issues from nozzle at high velocity.
 The blade which change the direction of motion of steam issuing from the
nozzle that force acts on the blade to change momentum and propel them.
 The auxiliaries are:
 Condensate extraction pump
 Hot well make up pump
 Grand stream condenser
 Surface condenser
 Extraction steam system
 LP Heater: A heater located between the condensate pump and either the
boiler feed pump.
 HP Heater: A heater located downstream of the boiler feed pump.
 De – aerator: It is a device that is widely used for the removal of oxygen and
other dissolved gases from the feed water to steam- generating boilers
 The Steam flow to the turbine Blades is controlled by ‘Governor’
Page No.30

31. The Governor controls the steam flow & is used to maintain 10.5kV.
To maintain this 10.5kV we use Digital Voltage Regulation method. DVR
action is controlled through Thyristor Action. DVR uses a separate Excitation
Transformer.
Generator produces alternating current:
The generator is connected to the turbine drive shaft. It has a moving part – the rotor
and a fixed part – the stator. The rotor’s outer surface is covered with
electromagnets. The stator’s inner surface, or cylinder wall, is made up of copper
windings. When the rotor turns inside the stator, the electrons in the copper windings
‘vibrate’. Their movement
generates an electric
currents.
The major types of cycle
involved
1.Steam Cycle
2. Fixed Water Cycle
3. Primary & Secondary
Cycle
4. Cooling Water cycle
The Boiler has a total of 4 Elevations for it’s Combustion process, Conveyor#9 is
used for transferring coal from the Bunker to Boiler.
A separate device called the Coal Feeder is used for each boiler (2 coal
feeders for each Boiler). The Coal Feeder operates by giving coal supply on a
belt which moves on a speed(The speed depends on the amount of Coal supply
required.)
Page No.31

32. Another important device
used in the Boiler Plant is
‘ESP’ Electro Static
Precipitator
.An electrostatic
precipitator (ESP) is a
highly efficient filtration
device that removes fine
particles, like dust and
smoke, from a flowing gas
using the force of an
induced electrostatic
charge minimally impeding
the flow of gases through
the unit.
In contrast to wet scrubbers which apply energy directly to the flowing fluid
medium, an ESP applies energy only to the particulate matter being collected
and therefore is very efficient. Basically ESP collects ash from Burnt coal. The
ESP contains 2 major parts :
1. CERM (Collecting Electrode RapperMotor)
2. EERM (Emitting ElectrodeRapperMotor)
The electrode apply a DC voltage of 100kV (Generally maintained @
60kV), ash is energized (electrically) and this charged ash particle is
absorbed by the electrodes. The Absorbed ash is emitted from the EERM
through to the Hopper.
Page No.32

33. Mini Project on Power Transformer
A transformer is a static electromagnetic device designed for the transformation of
one alternating current system into another one of the same frequency but with other
characteristics voltage and current in particular.
What is Power Transformer
Power Transformers are used in transmission in network of higher voltages for step-
Up & step-Down operation.(Ex: 400kV,200kV,) & are generally rated above 2000A.
Transformer Size & Insulation Level :
Power Transformer is used for transmission at Heavy loads, High voltage greater
than 33kV & near about 100% efficiency. It also has a big size & operates @ High
insulation Levels & installation is little complex in nature.
as compared to the distribution transformer which operates @ 50-70% efficiency
levels, easy in installation.
Iron & Copper Losses :
Power transformers are used in transmission network so they are not connected to
the consumer directly as a result the Load Fluctuations are very less. These are
loaded fully during 24Hrs a day so the Cu & Fe losses occur through out the day.
 The average loads are nearer to full loads & are designed in such a way that
the maximum efficiency occurs at Full-Load condition. These are independent
of time so in calculating efficiency only power basis is enough.
Efficiency & Operational Principle:
Power transformer are used for transmission as a step up devices so that the
12r loss can be minimized for a given flow. These are designed in such a way
that to utilize the Core to maximum & will operate @ very much nearer to the
knee point of B-H curve. This brings down the mass of the core enormously
down. @ maximum efficiency condition the transformer has a matched Cu-
loss & Fe-loss.
Page No.33

34.  All Day Efficiency = (Output in KW hr) / (Input in KW hr) in 24 hrs, it is always
less than power efficiency, whereas Power Transformer efficiency is
determined by Commercial Efficiency.
Power Transformers are installed @ the Sending or Receiving end of the
transmission line.
Connection & Windings:
A power transformer usually has one Primary & one secondary, & one
secondary & one input and output. The primary winding is generally
connected in Star connection & secondary winding is connected in Delta
winding.
CHP (coal handling plant)
Generally coal is used in any thermal power plant. So there must be a coal
department foe coal handling and its maintenance which is commonly called coal
handling plant. Here coal is brought from of different types with different
configuration of quality. In Tata power coal is imported from MCL (Mahanadi coal
limited) from Orissa and WEST BOKARO (middling coal) Jharkhand.
Comparison of MCL coal and middling coal is as follows : --------------------
MCL coal MIDDLING coal
Size=600mm including dust Size=25mm dust free
30% use in Tata power, Jojobera 70% use in Tata power, Jojobera
Carbon=(40-46)% Carbon= (45-48)%
Sulpher=(0.4-0.8)% Sulpher= (0.4-0.8)%
Moisture= (5-6)% Moisture= 5-6%
Volatile matter=(23-26)% Volatile matter=(19-21)%
Nitrogen=(0.2-0.6)% Nitrogen=(0.2-0.6)%
Page No.34

35. One rack is equal to 59 wagons which consist of
approximately 4000 tons coal. The layout of
working of CHP if as follows
There are three main process in coal handling plant
for coal feeding in boiler :-----
1. Wagon tripling
2. Crushing
3. Feeding
Wagon tippler:- it is done through a hydraulic system for coal feeding. This is
method of sending coal from a wagon to apron feeder through hopper. Each
hopper has two reclaim hopper. Reclaim hopper1 and reclaim hopper2. A wagon
is turned by using side alarm charger up to a 135degree to 160degree. Then coal
reached to conveyer belt. The capacity of SAC (side alarm charger) is to 25
wagons turning but here it is due to support and turn out up to 15wagond so that
the equipments will be well maintained. The equipment details of SAC(side alarm
charger) is
Manufacturer :- TRF Ltd.
Pulling capacity :- 24 wagons
Motor rating :- 45 KW, 1500rpm
Charging speed cap :-0.5
Type of traction :- chain & Sprocket
Side arm lifting angle : - Hydraulic cylinder
Length of runway :- 40m
Crushing:- it is a processes of breaking large size coal into small of a given range
size. Crusher is generally used for MCL coals which gives output of 150mm at
Page No.35

36. 600input coal, the above process is done in primary crusher and then sent to
secondary crusher. Secondary crusher filters small size coal, sends them to next
conveyer belt. besides the primary as well as secondary crusher, there is
magnetic separator of separating the magnetic impurities if any found. Rest of big
size coals are crushed in secondary up to a output of 25m which is the required
size of coal to be feeded in Tata power of Jojobera.
Hopper capacity=205 ton
Coal feeding: Here coal is stored in 3 stock yard one is uncrushed coal and
another is crushed yard A , consist of required coal to be used in boiler and
crushed yard B of different size for any other purpose or different use in plant.
Yard B is also used as back up yard for boiler coal. Coal is feed to hopper then
through RPG(Rack & pinion gate), RPG remains open 50%. it goes to variable BFD
(belt feeder) connected in parallel as conveyer belts. The speed of belt is 2.6m/s
for 1200m belt and 1.6m/s for 1600m belt. We cannot increase or decrease coal
size so screening is done while coal feeding using 75mm vibrator. There are 12
paths for coal feeding and supporting conveyer belts. path 11 and path 5 is
mainly used for coal feeding.
Here most of the motors used of 1500 rpm operated at two voltages v1=6.6kv
for high tension and v2=415v for low tension work done. There is a gear box for
changing or controlling speed of motor.
Problems may occurred in CHP :-----
 Choking due to heavy water logging in rainy season.
 Belt breaking in poor condition.
Page No.36

37. CONCLUSION
This vocational training helped us in knowing what it takes
to be in a corporate section. Working in an industry requires
soft – skills, patience and the power of making adjustments.
We got a good view of the working and use of different
electrical machines and other equipments, understood the
need of control rooms in every realm of the power plant and
above all learned that “SAFETY IS IN YOUR OWN
HAND”, without it we can suffer major consequences and it
can even risk one’s job and life. Also, we could relate my
theoretical knowledge with the practical field and got to
know that both practical as well as theoretical knowledge has
its own experience and they run in parallel tracks.
Undergoing this training helped us to develop our inner self
confidence and interactions with people in the plant premises
thus giving me an interest in understanding basic engineering
work. Through this training, we met people who shared their
views, thoughts and outlooks required for working in an
industry. Apart from the training, the culture Tata Power
inculcates in each and every employee and even their
trainees is really commendable.
Page No.37