2. Report prepared by:
• Yagnik Utsav P.
• College Enrollment no. 100170109053
• Guided by :
• Shri M. L. Upadhyay (Ex. C.E., GSECL, Gandhinagar)
• Shri M. B. Patel (S.E., efficiency department, GSECL,
Gandhinagar)
• Shri R. R. Valand (Switchyard, GSECL, Gandhinagar)
• Shri N. L. Patel (GSECL, Gandhinagar)
3. General Information about TPS
• A TPS(Thermal Power Plant) is a electricity
generating station which uses coal as the fuel to
generate heat. The heat produced is then given to
the boiler which produces steam. This steam is then
given to the HP turbines and utilized to run the shaft.
The shaft of turbine is mechanically coupled to the
alternator which converts mechanical energy to the
electrical energy. The diagram about a TPS is as
below. All TPS work on the Rankine cycle. Normally,
such TPS have efficiency of the range 30-35%.
5. About GSECL, Gandhinagar
• GSECL, Gandhinagar (The Gandhinagar Thermal
Power Station) is a Coal Based Power Station. It is on
the bank of Sabarmati River. There are two units of
120 MW each (Unit no. 1 & 2), three units of 210
MW each (Unit no. 3, 4 & 5) with a total installed
capacity of 870 MW.
• All the above units are of BHEL make. Commissioning
dates of unit no. 1 to 5 are 13.03.1977, 10.04.1977,
20.03.1990, 20.07.1991 and 17.03.1998 respectively.
7. Switchyard
For Transmission and Controlling
• Generator
• Transformers
• G.T.(Generating Transformer)
• S.T.(Station Transformer)
• Auxiliary Transformer
• Current Transformer
• Wave teff
• Isolator
• Terminal box for selection of isolator
For Protection and Measurement
• Post insulator
• SF6 circuit breaker
• Potential transformers
• Surge / Lightening arrester
• Earth wire
• Earth electrodes
• Current Voltage transformer
8. About Switchyard
• We can consider switchyard as the electrically starting
end or finishing end of the power station. If the power is
generated in the station and it is transmitted to the
outer stations than it can be referred as end point. After
generation , the voltages are stepped up using GTs and
then given to the bus no 1 and transmitted to the
selected line using isolators.
• If the power is received then it can be referred as
starting end. The high voltage received from buses is
stepped down by STs and then utilized for running
auxiliaries
9. For Transmission and Controlling
Generator
• At GSECL, Gandhinagr, the total installed capacity is
870MW.
• There are total 5 generators in the plant. Generator
1 and 2 are 120MW and 2,3 and 4 are 210 MW
generators.
• All generators are BHEL make.
11. GT(Generating transformer)
• GSECL, Gandhinagar has 5 GTs of 140 MVA capacity.
They provide 220 kV by stepping up 13.8 kV/15.75 kV
which is received from generator.
• When power is generated in the generator,
respective GTs are used to step up the 13.8 kV to 220
kV. The GT is then connected to the current
transformer
12. ST(Station transformer)
• GSECL, Gandhinagar has 5 STs of 22.5 MVA capacity.
They provide 7 kV by stepping down 220 kV which is
received from bus bars.
• When generator is in off position and the power is
not generated, the respective STs are operated to
run the auxiliaries.
13. Unit Auxiliary Transformers
• When synchronization goes above 70%, the power
plant uses its own power to run auxiliaries.
• GSECL, Gandhinagar has auxiliary transformers of 15
MVA.
• They step down voltage from 15.75 kV to 7 kV or 6
kV. All UATs are tap changer transformers.
14. Current transformers
• CTs are useful to reduce the
current so that it remains below a
certain limit to reduce the copper
and corona losses.
• Here, switchyard has 1000:1
ratio CTs.
• Specifications :
Parameter Rating
Highest system voltage 245kV
Rated primary current 1500kA
Frequency 50Hz
Insulation level 480/1050kV
S.T. current 20kA/3sec
15. Wave teff
• Wave teff is an instrument which controls the frequency of
power transmission so that it doesn’t give disturbance to the
neighboring communication lines.
• It is a cylindrical caged instrument.
• Specification :
Parameter Rating
Inductance 0.5 mH
Frequency band 150-500 kHz
Ir 1250 A
Short circuit current 3.5 kA
16. Isolator
• Isolator is a switch which connects bus bar to outer
transmission line. It is an “off load” device.
• We can select required isolator to conduct by using a
terminal box which works by a bidirectional motor.
• Isolator is made open when line requires maintenance
and servicing.
• Isolator is also called as “disconnector” or “disconnect
switch”.
18. For protection and measurement
Post insulator
• It is used to give required ground clearance to the
conductor so that hazardous effect is avoided due to
high voltage being carried by the conductor.
• The length and size of disc depends upon our
required voltage rating and conductor parameters.
20. SF6 circuit breaker
• At GSECL, Gandhinagar, all circuit breakers are SF6
circuit breakers.
• They are connected after CTs to provide protection
to the grid and buses A and B.
• As the name suggests, in these circuit breakers the
quenching medium is SF6 air which is pumped in the
airtight cabinets so that their pressure remains 20.5
bar.
21. Specifications of SF6 circuit breaker
Parameter Rating
Voltage 245 kV
Normal current 2000 A
Lightening impulse voltage
withstand
1050 kV
Short time withstand current
and duration
40 kA & 3 sec
First pole to clear factor 1.3
Closing and opening device
supply voltage
220 V dc
Gas pressure SF6 / 20⁰ C 7.0 bar
23. Potential transformer
• PTs are useful for measuring bus voltages by
reducing the values of high voltages to the meter
range.
• In this way PTs protect the measuring devices from
high voltages.
• We can use PT of the required range to step down
the high voltage and bring it to the measuring range.
• At GSECL, Gandhinagar, PT steps down voltage from
220 kV to 110 V for measurement
24. Surge arrester
• The purpose of surge arrester is to divert damaging
lightening-induced transients safely to ground
through property changes to its varistor in parallel
arrangement to the conductor inside the unit.
• Also called a surge protection device (SPD) or
transient voltage surge suppressor (TVSS), they are
only designed to protect against electrical transients
resulting from the lightning flash
26. Earth wire
• An earth wire is run along transmission line at the
top of the tower so that an earth fault doesn’t
damage the transmission tower.
Earth electrodes
• Earth electrodes are given to the outer surface of the
apparatus to make human safe from fatal current
due to earth faults.
27. Current Voltage transformer
• The CVT are used to measure current and voltages
on the line.
• Ratings of CVT at GSECL, Gandhinagar :
Parameter Rating
Rated voltage 220/1.73 kV
Total burden 100 VA
Highest system voltage 245 kV
Nominal capacitance 400 pF
Frequency 50 Hz
29. CPEM
• CPEM is the short form of Coal Plant Electrical
Maintenance
30. Path of Coal in storage yard
• The coal extracted from the mines is brought to the
TPS through train or any other transport.
• At GSECL, the coal from Bihar, Jharkhand and other
eastern states is brought in train.
• The train is emptied in the big conveyer belt by
tipplertippler.
31. About Tippler
• Tippler is a motor driven assembly which empties
train wagon by rotating it 180 degrees.
• Its motors are 6.6 kV motors and are operated by
operator when four arms of tippler holds the vagon.
• At GSECL, it can empty a wagon within 10 seconds
after motors are operated. GSECL, Gandhinaagr has 3
tippler units.
33. Path of Coal in storage yard
• After coal has been emptied from wagon, it falls on
apron feeder.
• Apron feeder is a mechanism moving on the shafts
and return roller. The whole structure is kept on a
main frame.
• It can manage flow of stones or powder materials
like coal.
35. Roller magnetic separator
• It is a mechanism in which metal parts are removed
from coal so that crusher inlet has only coal content.
• If metal parts are not removed from coal than
crusher might get mechanically locked or even
damaged while operating.
• It is called as IMS(inductive magnetic separator) as it
uses induction motors in rollers. Motors are 415 V
motors.
36. Path of Coal in storage yard
• After metal parts have been removed from coal, if
coal is in form of big stones than it is given to the
crusher unit.
• Crushers are 6.6 kV motors having hammer on their
surfaces so that they can break stones of coal in to
small parts.
• GSECL, Gandhinagar has 4 crusher units.
38. Path of Coal in storage yard
Concept of Pulverization of coal
• The concept of burning coal that has been pulverized
into a fine powder stems from the belief that if the
coal is made fine enough, it will burn almost as easily
and efficiently as a gas.
• The feeding rate of coal according to the boiler
demand and the amount of air available for drying
and transporting the pulverized coal fuel is
controlled by computers. Pieces of coal are crushed
between balls or cylindrical rollers that move
between two tracks or "races."
39. Pulverization of coal
• The raw coal is then fed into the pulverizer along
with air heated to about 650 degrees F from the
boiler. As the coal gets crushed by the rolling action,
the hot air dries it and blows the usable fine coal
powder out to be used as fuel.
• The powdered coal from the pulverizer is directly
blown to a burner in the boiler. The burner mixes the
powdered coal in the air suspension with additional
pre-heated combustion air and forces it out of a
nozzle similar in action to fuel being atomized by a
fuel injector in modern cars. Under operating
conditions, there is enough heat in the combustion
zone to ignite all the incoming fuel.
42. EMD
• EMD is the short form of Electrical Maintenance Department.
• This department deals with replacement and repairing of
electrical equipments used in different departments of power
plant.
43. Care to be taken
• Performing maintenance on electrical equipment
can be hazardous. Electrical and mechanical
energy can cause injury and death if not
managed properly.
• Complete, accurate, and current documentation
is essential to an effective maintenance program.
Whether performing preventive, predictive,
condition-based, or reliability-centered
maintenance, keeping track of equipment
condition and maintenance—performed and
planned—is critical.
44. Critical equipment as any system, asset,
or component whose failure could cause:
• Loss of transmission capability or reduction in
capacity
• Serious personnel injury or violation of a
safety regulation
• An environmental hazard resulting in harm to
the public, environment, or damage to public
property
45. Frequencies of maintenance
• Weekly: Calendar week (Sunday to Saturday)
• Monthly: Calendar month (first day through the last day of
the month)
• Quarterly: A calendar quarter consisting of 3 calendar
months
• Semi-annually: Six calendar months
• Annually: A calendar year (January 1 through December
31)
• Multiyear: Multiple calendar years (e.g., 5-year – January 1,
2011, through December 31, 2015)
• It is up to the individual office to document the tolerances
associated with these stated frequencies.
• Many offices use the concept of a maintenance season to
describe the timeframe. A maintenance season will be
considered the period of time from October 1 of the
current year through May 31 of the following year.
46. Electrical Equipment Maintenance
Annunciators and Alarms
• Annunciators and alarms provide essential plant
condition status information to O&M personnel. Two
aspects must be considered:
1. Correct operation of annunciator and alarm devices
2. Integrity of the annunciator and alarm circuits
Maintenance or Test Recommended Interval
Operational test Weekly
Functional test 2 years
47. lightening Arresters
• Lightning or surge arresters provide protection for important
equipment from high energy surges. These arresters are static
devices that require fairly infrequent maintenance.
• Most maintenance must take place while the associated
circuit is de-energized.
• However, crucial visual inspections and infrared (IR) scans can
take place while energized.
Maintenance or Test Recommended Interval
Visual inspection Semi-annually
Clean insulator and check
integrity of connections
6 years
Insulation test (Double test –
power frequency dielectric
loss, direct current [dc]
insulation resistance,
power factor
6 years
48. Batteries, Battery Chargers, and Battery Monitoring
Systems
• Battery systems provide “last resort” power for performing
communication, alarm, control, and protective functions
(relaying and breaker tripping) when other sources of power
fail.
• Battery system maintenance should have highest priority.
• Computerized, online battery monitoring systems can be
installed to supplement a maintenance program and reduce
costs.
• Battery chargers require regular maintenance as well.
49. • Maintenance Schedule – Flooded, Wet Cell, Lead Acid etc
Batteries
Maintenance or Test Recommended Interval
Battery float voltage (charger meter) Weekly
Visual inspection Monthly
Check accuracy of charger meter Monthly
Cell float voltage pilot cells with meter Monthly
Cell float voltage all cells Quarterly
Specific gravity pilot cells Monthly
Specific gravity (10 percent [%] of all cells) Quarterly
Specific gravity all cells Annually
Temperature (pilot cell) Monthly
Temperature (10% of all cells) Quarterly
Connection resistance (this may be checked by IR
scan while loaded)
Annually
Capacity testing 5 years
Safety equipment inspection Monthly
50. Bushings
• Bushings are critical components of medium and
high voltage circuit breakers and transformers.
• Bushing maintenance usually is conducted at the
same time maintenance is performed on the circuit
breaker or transformer, or at least during an outage
on that equipment.
51. Buswork, Enclosures, and Insulators
• Buswork conducts current from one part of the powerplant or switchyard
to another. Buswork usually is constructed of flat or round copper or
aluminum busbar and can be either isolated-phase or nonsegregated.
• Except for infrared scanning, bus maintenance must be conducted de-
energized. Standoff buswork insulators provide isolation of “live” power
circuits from ground and other circuits. Failure of insulators will cause a
power system fault and a forced outage.
Maintenance or Test Recommended Interval
Check integrity of connections 6 yrs
Check and clean enclosures 6 yrs
Insulation test 6 yrs
52. Power Cables – Energized at 2 kV and Above
• Periodic maintenance tests are needed during the life of the cable to
determine whether or not there has been significant insulation
deterioration due to operational or environmental conditions.
• High potential tests (hipot) effectively reduce inservice failures from faults
of the cable or its accessories. When done properly, maintenance tests
can detect problems in cables that are approaching failure without
accelerating the deterioration process.
• Except for infrared scanning, de-energize the cable circuit before
maintenance.
Maintenance or Test Recommended Interval
Insulation test 5 yrs
Insulating oil – dissolved gas
analysis (DGA), physical, and
chemical tests
Annually
53. Circuit Breakers
• Circuit breakers interrupt electrical current to stop power flow both for switching
operations and during fault conditions.
• Molded case circuit breakers located in low voltage distribution panels are
typically 125 to 250 volts direct current (Vdc); 120, 208, 240, 277, and 480 volts
alternating current (Vac); or used for control, protection, and auxiliary power.
These molded case breakers should not be loaded more than 80% of the rated
value unless the breaker is specified as a continuous type capable of being loaded
to 100%.
• Medium voltage circuit breakers generally are located in station-service metal clad
switchgear or in separate enclosures as unit breakers. Examples are 4,160-Vac
station service and 11.95- and 13.8-kV unit breakers. These breakers may be air,
air blast, vacuum, or SF6 .
• High voltage circuit breakers are located in separate breaker enclosures, either
indoors or outdoors. These are oil, air-blast, or SF6 breakers. Examples are 115-
and 230-kV breakers located in the switchyard.
54. Medium and High Voltage SF6 Breaker
Maintenance Schedule
Maintenance or Test Recommended Interval
Preventive maintenance
(external inspection)
Annually
Record gas pressure and
temperature; compare with
tolerances and prior readings
Monthly
Record operations counter Monthly
Visual inspection Monthly
Check contact wear 6 years
Check foundation, grounds,
paint
6 years
Check external screws, bolts,
electrical terminals tight
Annually
55. Coupling Capacitors
• Coupling capacitor/voltage transformers (CCVTs) are
instrument transformers that provide a path for
communications, metering, control, and relaying equipment
without allowing power system frequency energy to pass.
• These are static devices requiring relatively little
maintenance. Except for infrared scanning, maintenance must
be conducted with equipment de-energized.
• This equipment normally is oil-filled and must be checked for
oil leaks.
56. • Thus, EMD department looks after all needs of maintenance
and replacements.
• Figure of Thermal imaging camera
