CALCUTTA ELECTRIC SUPPLY

CORPORATION
(CESC LIMITED)

BUDGE BUDGE GENERATING STATION

NAME: - SOUMYADEEP NASKAR

ADDRESS: - 21, DHARMATALA ROAD, KASBA,KOLKATA- 700042
COLLEGE: - KALINGA INSTITUTE OF INDUSTRIAL TECHNOLOGY,
BHUBANESWAR- 751024
BRANCH-ELECTRICAL
YEAR-3RD
DURATION OF TRAINING: - 07/05/2018 TO 19/05/2018
 ACKNOWLEDGEMENT

This project report is a collective effort of many people who

helped me a lot to successfully accomplish this project report
and without the support of whom this report would not have
been implemented. This acknowledgement is a way to show my
deep sense of gratitude to all the people of BBGS for their inspiration
& guidance during the training period whose co-operation and
suggestions helped me a lot to complete this project. I would like to the
following people for giving me the golden opportunity to do the training;
1. MR. D. MAITRA GENERAL MANAGER, HR
2. MR. S. SAMADDAR GENERAL MANAGER, BBGS
3. MR. S. ROY DY. GENERAL MANAGER, BBGS
4. MR. S. BANERJEE DY. GENERAL MANAGER, BBGS
I am also highly indebted to the following people under whose guidance
I have successfully completed my training in various departments;
• MR. SANJOY ROY SR. ASST. ENGR, HRD
• MR. PIJUSH KANTI LAHIRI CONSULTANT, HRD
• MR. ANANDAMOY PAL MANAGER, FAO
• MR. RAJDEEP JANA MANAGER, FAO
• MR. MANISH CHAMAN MANAGER, MMD
• MR. KAMAL DUTTA ASST. MANAGER, MMD
• MR. KAUSHIK CHOUDHIRY SR. MANAGER, PLG
• MR. RATNARGHYA CHAKRABORTY ENGINEER
• MR. SUMAN SENGUPTA MANAGER, OPS
• MR. DEBASHIS CHATTERJEE DY. MANAGER, OPS
• MR. SUSOVAN NARANYAN CHOUDHURY MANAGER, E & I
• MR. ANIMESH DAN ASST. MANAGER, E & I
 CESC LIMITED
BUDGE BUDGE GENERATING STATION

NAME: ARNAB DAS

BRANCH: ELECTRICAL ENGINEERING
INSTITUTE: KALINGA INSTITUTE OF INDUSTRIAL TECHNOLOGY
DURATION OF TRAINING: 07/05/2018 TO 19/05/2018

SIGNATURE: -
DEPARTMENT: - OPS
Name: - …………………………………………. Signature: - ………………………………………….
DEPARTMENT: - F & A
Name: - …………………………………………. Signature: - ………………………………………….
DEPARTMENT: - MMD
Name: - …………………………………………. Signature: - ………………………………………….
DEPARTMENT: - E & I
Name: - …………………………………………. Signature: - ………………………………………….
DEPARTMENT: - PLG
Name: - …………………………………………. Signature: - ………………………………………….
DEPARTMENT: - PTC
Name: - …………………………………………. Signature: - ………………………………………….
 ABOUT CESC
CESC is India’s first fully integrated electrical utility company and
we’ve been on an epic ride ever since 1899 in generating and
distributing power in Kolkata and Howrah.
We have private participation in generation, transmission and
distribution of electrical power. We are the sole distributor of
electricity within an area of 567sq km of Kolkata & Howrah and
serve 2.9 million consumers which include domestic, industrial
and commercial users. We own & operate three thermal power
plants generating 1125 MW of power. These are Budge Budge
Generating Station (750 MW), Southern Generating Station (135
MW), & Titagarh Generating Station (240 MW). From our three
generating stations, we accomplish 88% of our customer’s
electricity requirement and remaining 12% is achieved by
purchase of electricity from third parties. More than 50% of coal
is sourced from captive mines for generation of electricity in our
generating stations.

We own & operate the Transmission & Distribution System

through which we supply electricity to consumers. This system
comprises of 474 km circuit of transmission lines linking the
company’s generating & receiving stations with 105 distribution
stations, 8,211 circuit km of HT lines further linking distribution
stations with LT substations, large industrial consumers and
12,269 circuit km of LT lines connecting the LT substations to LT
consumers.

In diurnal course, we have verged upon renewable sources. We

have brought forth three projects in three different areas of
renewable sources. These are Gujarat Solar, which is a solar
plant in Gujarat’s Kutch generating 9MW solar energy, Hydro
Power Venture (Papu Hydropower Projects Limited & Pachi
Hydropower Projects) in Arunachal Pradesh, generating 146
MW energy and Wind Power Operation, a 24 MW project at
Dangi in Rajasthan.

We also installed two thermal power plants to meet the

requirement of our electricity. These are Chandrapur Thermal
Plant which is 600 MW project at Chandrapur, Maharastra and
Haldia Thermal Plant which is 600 MW project at Haldia, West
Bengal.

With our continuous effort to accomplish the requirement of

our consumers and make them easily avail all our services from
their premises, we have employed value added online services.
By online services, work can be done from consumer’s premises
and they don’t have to visit offices for any work. All our services
can now be accessed online. Our zeal lies to stay true and
deliver exceptional service to our consumers who are with us on
this relentless journey with a hope that they will continue to be
part of our journey.
 FUEL AND ASH OPERATION

The primary fuel for these units is bituminous coal which is been futher
pulverized for consumption.The coal handling plant has been designed
for 250mm of coal in the mesh of the grinder , further to 100mm and
further to 20mm . It is then taken for operation and coal stack. Coal is
unloaded in the yard either by wagon tipplers or in the track hopper
through bottom discharge wagons. Coal is being transported from the
coal mines to the facility by railway wagons of either by Bogie Open type
wagons (BOXN) or by Bogie Open Bottom Rapid discharge wagons
(BOBRN). The BOXN wagons are taken to the tippling unit with the help of
a side arm charger to the tippling unit where the coal is being unloaded.
The BOBRN wagons are unloaded 18 wagons at a time in the track
hopper. The coal is crushed into two stages before it is being fed into the
boiler bunkers. In the first stage the coal is being crushed to 100mm size
by primary crushers and finally into 20mm by secondary crushers. Parallel
chains of conveyors are being provided to carry coal from the coal stack
yard to the boiler bunkers.
The FUEL AND ASH DEPARTMENT can be broadly divided into two plants:
(i) Coal handling plant
(ii) Ash handling plant
 COAL HANDLING PLANT
Capacity:
Design: 960 T/Hr Rated: 800T/Hr
No. Of wagon Tippler: 2 No. Of Track: 1

Primary Crusher:
Quantity: 2 Nos. Type: Rotary Breaker

Secondary Crusher:
Quantity: 2 Type: Ring Granulator

Stacker-Cum-Reclaimer:
Type: Slewing and Luffing Boom Stacker with Bucket Wheel Reclaimer , Rail
mounted, suitable for Reversible Yard Conveyer.
Nos: 2 Height of pile: 10.5m
Total Travel (m): 308m Material: Semi Crushed Coal
Lump Size: 100mm Lump Size: 100mm
 ASH HANDLING SYSTEM

Fly Ash Handling System: Fly Ash Evacuation Rate-80 Mt/Hr.

Capacities of Tank/Vessel:
Air Heater: 57 Liters ESP 3: 145 Liters
ESP 1&2: 485 Liters ESP 4 to 7: 85 Liters

Bottom Ash System:

Bottom Ash Cleaning Rate- 60 Mt/Hr.
Effective Storage Capacity:
Bottom Ash Hopper: 150MT(Approx.); Surge Tank:1670CUM
De Watering Bin: 432MT(Approx.); Overflow Transfer Tank:21CUM
Settling Tank: 1240CUM(Approx.); Decant Water Transfer:35CUM
 (ESP)

The Complete Ash Handling system is divided as Bottom Ash Removal system and
Fly Ash removal system. The fly ash removal system is continuous, whereas Bottom
Ash Removal system is intermittent and carried out at once per shift.
Bottom Ash Removal is a wet system. The bottom ash of each unit is crushed by a
convergent nozzle which is used to achieve high speed and hydraulically conveyed
in the form of slurry by divergent nozzle which is used to increase the pressure of
the water from bottom ash hopper to Dewatering bins. Collected bottom ash at
the bins is removed by the trucks, this method is called Zero Discharge System.
Fly ash collected in ESP & Air heater hoppers is removed in dry form by dense
phase pneumatic conveying system in two stages. In the first stage, the flue gas
enters the ESP which consists of both negative & positive plates which are charged
with 75Kv DC supply. The dust from the flue gases get negatively charged and
attaches with the positively charged plates. The ash settles in the form of mounds
over which suitably identified plantation will take place to convert the entire place
into an eco-friendly zone.
The majority of the fly ash is being sent to the river ganga to be sent to the barge
which carries this ash to various cement industries in Bangladesh.
 MECHANICAL MAINTENANCE DEPARTMENT
Maintenance is a set of organized activities that are carried out in order
to keep equipment in its best operational condition with minimum cost
acquired. It includes performing routine actions which keep the device
in working order or prevent trouble from arising.

MAINTENANCE TYPES: -

Broadly speaking, there are three types of maintenance in use:

Preventive Maintenance: Preventive maintenance is the maintenance

performed

in an attempt to avoid failures, unnecessary production loss and safety

violations. It includes scheduled maintenance (daily and routine) of the

equipment and includes activities like regularly monitoring the

temperature and

pressure of the bearing, grease, windings, oil, air and gases, the flow of
air,

water and oil, the rotation of bearing lubricating rings, moisture content
in the

gases, etc. It is the maintenance before the breakdown occurs.

Corrective Maintenance: It is the maintenance where equipment is

maintained

after break down. This maintenance is often most expensive because

worn
equipment can damage other parts and cause multiple damage. The
corrective

maintenance is carried out to bring it back the equipment in the working

order.

Predictive Maintenance: This kind of maintenance includes activities to

foresee

events in the future that could lead to damage of the equipment or

cause a

failure in the system. It implies vibration monitoring, Ultrasound tests,

Breaker

timing test, Thermograph etc.

The major divisions in this department include:

Maintenance of Boiler & its auxiliaries:

1. Boiler
2. ID Fan
3. FD Fan
4. PA Fan
5. Coal Mill
6. Various Pumps, etc.

Maintenance of Turbine & its auxiliaries:

1. Turbine
2. CEP
3. BFP
4. NASH Pump
 5. HP_LP Bypass System
6. Condensate Transfer Pump
7. Circulating Cooling Water (CW) Pumps
8. Service Cooling Water Pumps, etc.

Maintenance of Fuel and Ash:

1. Conveyor System
2. Rotary Breakers
3. Crusher
4. Wagon Tipplers
5. Track Hoppers
6. Bottom & Fly Ash

While performing maintenance activities, it is important we maintain a

schedule for the same, take in to safety considerations, keep all
necessary tools and equipment in the vicinity of the equipment,
ensuring only skilled man power to handle the machine.

Also, the various maintenance activities should be practiced in a

sequential manner and proper note be taken. Given below are checklists
for HP-LP Bypass Maintenance and for Cooling Tower Fan Maintenance.

LUBRICATION SYSTEM: -

Lubrication is an essential activity for the healthy working of equipment.

It is the process or technique employed to reduce wear off one or both
surfaces in close proximity and moving relative to each other, by
interposing a lubricant by interposing a lubricant between the surfaces
to carry or to help carry the load between the opposing surfaces.
Lubrication purposes to:

Lubricate: Reduces Friction by creating a thin film(Clearance) between

moving parts (Bearings and journals)

Cool: Picks up heat when moving through the engine and then drops
into the cooler oil pan, giving up some of this heat.

Seal: The oil helps form a gastight seal between piston rings and cylinder
walls

Clean: As it circulates through the engine, the oil picks up metal particles
and carbon, and brings them back down to the pan

Absorb Shock: When heavy loads are imposed on the bearings, the oil
helps to cushion the load.

Absorb Contaminants: The additives in oil helps in absorbing the

contaminants that enter the lubrication system.
 PLANNING & ENVIRONMENT DEPARTMENT

The planning department of BBGS CESC Ltd. is the department which

controls every aspect of the progress of the company and supervises on
the work of every department. This kind of management is maintained
by the data which is provided by the respective departments.

OBJECTIVES: -

1) Minimizing the downtime of critical equipment’s to reduce loss

of generation through proper outage planning of equipment’s
and condition monitoring.
2) Monitoring SPM, Sox and NOx in gaseous emission.
3) Restricting SPM and RPM of ambient air and work zone within
statutory limits.
4) Ensuring 100% recycling of plant effluents.
5) Development of green belt in and around plant premises.
6) Monitoring compliance of all applicable legal and other
requirements.
7) Minimizing number of incidents.
8) Creating awareness among employees about our management
systems and various intra-portals of BBGS.
9) Creating a safe working condition by routine checking of all
tools and tackles.
10) Monitoring and up-keeping of Emergency handling
equipment.
11) Ensuring a high standard of house-keeping within the plant
by organizing 2 nos of house-keeping audit in each FY to ensure
safe and healthy working condition.
12) Monthly review of actual expenses of all departments vis-à-
vis the budget.
 13) Maintaining a high standard of communication system
throughout the plant.
14) Organizing quarterly performance review meeting

PROCESS DETAILS:
• Preparation of MIS reports, as per requirements of Station
Management or Corporate.
• Development of software modules as per business requirements.
• Improving safety standards for restricting accidents.
• Efficient management of environment.
• Complying with statutory requirements related to safety and
environment.
• Sustenance of QMS and EMS through periodic audits and review
meetings.
• Reduction of forced outages of critical equipment’s through
condition monitoring.
• Maintenance planning to reduce down-time of critical
equipment’s.
• Collection of various samples of coal, ash, water and oil.
• Up-keeping of LAN, computers and printers.
SOFTWARE DEVELOPMENT:
An internal website of BBGS has been launched which provides single
window access to various forms and reports required for better control,
monitoring and analysis of safety, health, environment and quality
related parameters. Some of the major modules available in this website
include:
a) Defect Management System
b) Orders and bill Entry System
c) Training management system
d) Leave management system
e) Double/due off/overtime for non-covenanted employees
f) Shift/Chummery Rota
g) Fuel and Ash related reports
h) Budget monitoring reports
i) Reports related to safety and environment
j) Departmental logs
k) PID drawings of all major systems and equipment’s
l) Reports for monitoring outages and generation losses
m) Telephone numbers/blood groups/birthdays of all employees

TARGETS OF BBGS:

Each and every department starting from coal unloading to generation of

electricity has its own monthly and yearly targets. This target is set by the
planning department in BBGS and the end of the respective month or
year it is seen that the target is being achieved or not and the required
regulation is taken according to it. This determination is very valuable
because it is important to determine the position of the power plant
among the others in India. Apart from this planning department also
makes a record of unit trips, leaks of tube, heat rate, total generation
loss, and environment related failures. Examples of such spreadsheets
are respectively given: -
 OPERATIONS DEPARTMENT
RANKINE CYCLE:
The Rankine cycle is a thermodynamic cycle which converts heat into
work. The heat is supplied externally to a closed loop, which usually uses
water as the working fluid. This cycle generates about 80% of all electric
power used in America and throughout the world including virtually all
solar thermal, biomass, coal and nuclear power plants. It is named after
William John Macquorn Rankine, a Scottish polymath.
A Rankine cycle describes a model of the operation of steam heat
engines most commonly found in power generation plants. Common
heat sources for power plants using the Rankine cycle are coal, natural
gas, oil, and nuclear.
The efficiency of a Rankine cycle is usually limited by the working fluid.
Without the pressure going super critical the temperature range the
cycle can operate over is quite small, turbine entry temperatures are
typically 565°C (the creep limit of stainless steel) and condenser
temperatures are around 30°C. This gives a theoretical Carnot efficiency
of around63% compared with an actual efficiency of 42% for a modern
coal-fired power station. This low turbine entry temperature (compared
with a gas turbine) is why the Rankine cycle is often used as a bottoming
cycle in combined cycle gas turbine power stations.
One of the principal advantages it holds over other cycles is that during
the compression stage relatively little work is required to drive the
pump, due to the working fluid being in its liquid phase at this point. By
condensing the fluid to liquid, the work required by the pump will only
consume approximately 1% to 3% of the turbine power and so give a
much higher efficiency for a real cycle. The benefit of this is lost
somewhat due to the lower heat addition temperature. Gas turbines, for
instance, have turbine entry temperatures approaching
1500°C.Nonetheless, the efficiencies of steam cycles and gas turbines
are fairly well matched.
There are four processes in the Rankine cycle. These states are identified
by numbers (in brown) in the above Ts diagram.
Process 1-2: The working fluid is pumped from low to high pressure. As
the fluid is a liquid at this stage the pump requires little input energy.
Process 2-3: The high-pressure liquid enters a boiler where it is heated at
constant pressure by an external heat source to become a dry saturated
vapor. The input energy required can be easily calculated using Mollier
diagram or h-s chart or enthalpy-entropy chart also known as steam
tables.
Process 3-4: The dry saturated vapor expands through a turbine,
generating power. This decreases the temperature and pressure of the
vapor, and some condensation may occur. The output in this process
can be easily calculated using the Enthalpy-entropy chart or the steam
tables.
Process 4-1: The wet vapor then enters a condenser where it is
condensed at a constant temperature to become a saturated liquid. In
an ideal Rankine cycle the pump and turbine would be isentropic, i.e.,
the pump and turbine would generate no entropy and hence maximize
the net-work output. Processes1-2 and 3-4 would be represented by
vertical lines on the T-S diagram and more closely resemble that of the
Carnot cycle. The Rankine cycle shown here prevents the vapor ending
up in the superheat region after the expansion in the turbine, which
reduces the energy removed by the condenser.
 BOILER
Boiler is a steam raising unit of single radiant furnace type with
auxiliaries, designated to generate steam at 184 kg/cm2 g pressure. The
unit burns pulverized low grade bituminous coal and is equipped with oil
burners. This plant is designed to operate at a 475m above sea level the
ambient temperature is 40o C with a humidity of 70%. The furnace
consists of walls of tangent bare water tubes. Rear water tubes from a
cavity for the pendant super-heater.
There are many advantages of using water tube boiler:
• Water tube boilers are small in size,
• the volume of the boiler is comparatively small in comparison to
the same size fire tube boiler,
• better circulation of water in the boiler is possible.

MANUFACTURER: - Unit 1 & Unit 2: M/S ABB ABL Limited, Durgapur

Unit 3: M/S BHEL
TYPE: - Horizontal single drum, natural circulation, water wall tube.
Each boiler has been provided with two forced draft fans (F.D), three
induced draft fans(I.D) for unit 1&2 & two induced draft fans (I.D) for
unit 3, two primary air fans (P.A),one primary tubular air heater, two
secondary tubular air heaters for unit 1 & 2 and two rotary air heater for
unit 3, six Ball & Race type pulverizes, six Volumetric coal feeders for
unit 1 & 2 and five Bowl type pulverizes, five Gravimetric coal feeders for
unit 3, etc. Soot blowing is done by steam. Main and reheat steam
temperature is maintained from full load to 60% load. The boiler is
capable of sustained stable operation down to 2 Mills at 30% capacity
without oil support for flame stabilisation.25% BMCR requirement can
be achieved by burning LDO alone.
BOILER
 BOILER DRUM
The steam drum is made up of high carbon as its thermal stress is very
high. There is a safety valve in the drum, which may explode if the
temperature and the pressure of the steam are beyond a set value. A
safety is a valve mechanism for the automatic release of a gas from a
boiler, pressure vessel or other system when the pressure or
temperature exceeds preset limits. It is a part of a bigger set named
Pressure Safety Valve (PSV) or Pressure Relief Valve(PRV). The other
parts of the set are named relief valves.
The boiler drum has the following purpose:
1.It stores and supplies water to the furnace wall headers and the
generating tubes.
2.It acts as the collecting space for the steam produced.
3.The separation of water and steam tube place here.
4.Any necessary blow down for reduction of boiler water concentration
is done from the drum.

RISER AND DOWN COMERS

Boiler is a closed vessel in which water is converted into the steam by
the application of the thermal energy. Several tubes coming out from
the boiler drum surrounding the furnace. Outside the water wall there is
a thermal insulation such that the heat is not lost in the surroundings.
Some of the tubes of the water wall known as the down comer, which
carries the cold water to the furnace and some of other known as the
riser comer, which take the steam in the upward direction. At the
different load riser and the down comers may change their property.
There is a natural circulation of water in the riser and the down comers
due to different densities of the water and the steam water mixture. As
the heat is supplied, the steam is generated in the risers. Lower density
of the steam water mixture in the riser than water in the down comer
causes natural circulation of water. Down comer connected to the mud
drum, which accumulates the mud and the water.

SUPER HEATER
The super heater rises the temperature of the steam above its
saturation point and there are two reasons for doing this:
FIRST- There is a thermodynamic gain in the efficiency.
SECOND- The super-heated steam has fewer tendencies to condense in
the last stages of the turbine.
It is composed of four sections, a platen section, pendant section, rear
horizontal section and steam cooled wall and roof radiant section. The
platen section is located directly above the furnace in front of the
furnace arch. It is composed of 29 assemblies spaced at 457.2mm
centers from across the width of the furnace. The pendant section is
located in the back of the screen wall tubes.
It is composed of 119 assemblies at 1114mm centers across the furnace
width. The horizontal section of the superheater is located in the rear
vertical gas pass above the economizer. It is composed of 134
assemblies spaced at 102 mm centers across the furnace width. The
steam cooled wall section from the side front and rear walls and the
roof of the vertical gas pass.no reheater is used.

SPRAY ATTEMPERATOR
In order to deliver a constant steam temperature over a range of load, a
steam generating unit(Boiler) may incorporate a spray attemperator. It
reduces the steam temperature by spraying controlled amount of water
into the super-heated steam. The steam is cooled by evaporating and
super heating the spray water. The spray nozzle is situated at the
entrance to a restricted venture sections and introduces water into the
steam. A thermal sleeve linear protects the steam line from sudden
temperature shock due to impingement of the spray droplets on the
pipe walls. The spray attemperator is located in between the primary
super heater outlet and the secondary super heater inlet. Except on
recommendation of the boiler manufacturer the spray water flow rate
must never exceed the flow specified for maximum designed boiler
rating. Excessive attemperator may cause over heating of the super
heater tubes preceding the attemperator, since the steam generated by
evaporation of spray water and it does not pass through the tubes. Care
must also be taken not to introduce so much that the un-evaporated
water enters the secondary stage of the super heaters.

AIR PRE-HEATER
The air heater is placed after the economizer in the path of the boiler
flue gases and preheats the air for combustion and further economy.
There are 3 types of air preheaters: Tubular type, rotary type and plate
type. Tubular type of air heater is used in TGS. Hot air makes the
combustion process more efficient making it more stable and reducing
the energy loss due to incomplete combustion and un burnt carbon. The
air is sent by FD fan heated by the flue gas leaving the economizer. The
preheated air is sent to coal mill as primary air where coal is pulverized.
The air sucked is heated to a temperature of 240-280oC. The primary air
transports the pulverized coal through three burners at TGS after drying
in the mill.

ECONOMIZER
The heat of the flue gas is utilized to heat the boiler feed water. During
the start up when no feed water goes inside the boiler water could
stagnate and over heat in the economizer. To avoid this, economizer re
circulation is provided from the boiler drum to the economizer inlet. The
feed water coming out from de-aerator passes through to special shape
of pipes inside the economizer. The special shapes of tubes provide
increase the contact surface area between the flue gas and the feed
water, so that maximum heat exchanging can take place.

ELECTROSTATIC PRECIPITATOR
It is a device that separates fly ash from outgoing flue gas before it
discharged to the stack. There are four steps in precipitation: -
1.Ionization of gases and charging of dust particles.
2.Migration of particle to the collector.
3.Deposition of charged particles on collecting surface.
4.Dislodging of particles from the collecting surface. By the electrostatic
discharge the ash particles are charged due to high voltage (56KV)
between two electrodes.
Generally maximum amount of ash particles is collected in the form of
dry ash, stored inside the SILO.
Rest amount of ash (minimum) are collected in the form of bottom ash
and stored under the water inside HYDROBIN.

ESP

SAFETY VALVE
A safety valve is a valve mechanism which automatically releases a
substance from a boiler, pressure vessel, or other system, when the
pressure or temperature exceeds preset limits. It is one of a set of
pressure safety valves (PSV) or pressure relief valves(PRV), which also
includes relief valves, safety relief valves, pilot-operated relief valves,
low pressure safety valves, and vacuum pressure safety valves. Vacuum
safety valves (or combined pressure/vacuum safety valves) are used to
prevent a tank from collapsing while it is being emptied, or when cold
rinse water is used after hot CIP (clean-in-place) or SIP (sterilization-in-
place) procedures. When sizing a vacuum safety valve, the calculation
method is not defined in any norm, particularly in the hot CIP / cold
water scenario, but some manufacturers have developed sizing
simulations.
No of Safety Valves Unit#1&2 Unit#3
At Drum 2 3
At Superheater 2 2
At CRH 4 1
At HRH 2 4
No of Air heater 3 2
No of F.D Fan 2 2
No of I.D Fan 3 2
No of P.A Fan 2 2
No of Coal Mills 6 5
TURBINE
Turbine is a rotating device which converts heat energy of steam into
mechanical energy. It is a two-cylinder machine of impulse reaction type
comprising a single flow high pressure turbine and a double flow low
pressure turbine. The H.P. turbine shaft and the generator are all rigidly
coupled together, the assembly being located axially by a thrust bearing
at the inlet end of H.P. turbine. The turbine receives high pressure steam
from the boiler via two steam chests. The H.P. turbine cylinder has its
steam inlets at the end adjacent to the no. one bearing block, the steam
flow towards the generator. Exhaust steam passes through twin over-
head pipes to the L.P. turbine inlet belt where the steam flows in both
directions through the L.P. turbine where it exhausts into under slung
condenser. Steam is extracted from both the H.P. & L.P. turbine at
various expansion stages & fed into four feed water heaters. Here
spherically seated Journal Bearing is used.

The main turbine is a Tandem Compounded, Three Cylinder, Single

Reheat, Double Flow LP cylinder, Condensing Type with uncontrolled
Extraction.

The steam turbine drives a 250 MW, 3Ø Alternator with Hydrogen

Cooled Rotor and Stator Core and DM water cooled Stator Windings
(Unit 1&2) at a speed of 3,000 rpm. The turbine shafts & generator rotor
are rigidly coupled together. The generator- field is excited from a static
excitation system. Power is generated at 16.5 kV and is stepped up to a
voltage of 132 kV (unit 1&2) and 220 kV (unit 3) in a generator
transformer for onward transmission to the system and there is an inter
connection between 132 kV switchyard and 220 kV switchyard thru’ ICT
(Inter connecting transformer).
The turbine utilizes an electro-hydraulic governing system. The start-up,
shut-down and loading of the turbine can be achieved automatically.
The turbine throttle pressure is 146 Kg/Cm2(abs.), the main steam
temperature is 537°C and the reheat steam temperature is 535°C.The
turbine cycle includes two stages of feed-water pumping (boiler feed
pumps and condensate extraction pumps), consisting seven stages of
regenerative feed-water heating by turbine bled steam, viz, two high
pressure regenerative closed feed-water heaters at the boiler feed
pump discharge, four low pressure closed feed-wafer heaters at the
condensate extraction pump discharge and one direct contact heater
(DE-aerator)for unit 1&2 and two high pressure regenerative closed
feed-water heaters at the boiler feed pump discharge, three low
pressure closed feed-wafer heaters at the condensate extraction pump
discharge and one direct contact heater (de-aerator) for unit 3. All the
feed-water heaters are of horizontal type. The two (2) lowest pressure
heaters LPH-1 &2 (unit 1&2) and LPH-1 (unit 3) are located inside the
neck of the condenser and LPH-1is provided with an external drain
cooler.

CONDENSER
Condenser is a device used for converting a gas or vapor to liquid.
Condensers are employed in power plants to condense exhaust steam
from turbines. In doing so, the latent heat is given up by the substance
and it will be transferred to the condenser coolant.
A surface condenser is a shell and tube heat exchanger installed at the
outlet of every steam turbine in thermal power stations.
The cooling water flows through the tube side and the steam enters the
shell side where the condensation occurs on the outside of the heat
transfer tubes. The condensate drips down and collects at the bottom,
in a pan called hot well. Initial air extraction from the condenser and
steady vacuum inside the condenser is achieved by two nos. motor
driven, water sealed, air extraction pumps commonly called NASH
pump. During normal operation of the plant, vacuum is maintained by
the circulating water flowing inside the condenser and the non-
condensable gases are extracted by one of the NASH pumps. 2 nos.
separate condensate storage tanks, interconnected to each other, are
provided for the three units. Condensate storage tanks receive de-
mineralized water from DM Plant.
FEEDWATER HEATER
Feed water heaters are used in power plants to preheat water delivered
hot steam to the generating boiler. Preheating the feed water reduces
the irreversibility in steam generation and hence improves the efficiency
of the system. This method is economical and reduces thermal shock
when the feed water is introduced back in the cycle. In steam power
plants, there are two kinds of low pressure & high-pressure heater.
These heaters help to bring the feed water to saturation temperature
very gradually.
Feed water is taken from the De-aerator, a feed water storage tank, by
motor-driven feed water pumps, and discharged through two stages of
high pressure regenerative feed water heaters and flue gas heated
economizer into the boiler drum. Provision is kept for condensate
bypassing of LP Heaters in two groups in the event of heater flooding so
that the turbine is protected from water ingress viz. LP Heaters-2 &1 and
drain cooler as one group, and LP Heaters-3 & 4 as the other of unit 1&2
and LPHeaters-1 and drain cooler as one group, and LP Heaters-2 & 3 as
the individual of unit3. LP Heater-2 drain is cascaded to LP Heater-l via a
flash box, while LP Heater-l drain is cascaded to the condenser-drains
flash box via the drain cooler. LP Heater-4 drain is similarly cascaded to
LP Heater-3, while LP Heater-3 normal drain is pumped forward by a 1 x
100% drain pump via control valves to LP Heater-3 main condensate
outlet of unit 1&2. LP Heater-2 drain is cascaded to LP Heater-l and
alternate drain to LP Heater flash box, while LP Heater-l drain is
cascaded to the condenser-drains flash box via the drain cooler. LP
Heater-3 drain is similarly cascaded to LP Heater-2 and alternate drain to
LP Heater flash box.
 DEAREATOR
Deaerator is a device widely used for the removal of oxygen and other
dissolved gasses from the feed water. It mostly uses low pressure steam
obtained from an extraction point in their steam turbine system. They
use steam to heat the water to the full saturation temperature
corresponding to the steam pressure in the de-aerator and to scrub out
and carry away dissolved gases. Steam flow may be parallel, cross, or
counter to the water flow. The de-aerator consists of a de-aeration
section, a storage tank, and a vent. In the de-aeration section, steam
bubbles through the water, both heating and agitating it. Steam is
cooled by incoming water and condensed at the vent condenser. Non-
condensable gases and some steam are released through the vent.
Steam provided to the de-aerator provides physical stripping action and
heats the mixture of returned condensate and boiler feed water makeup
to saturation temperature. Most of the steam will condense, but a small
fraction must be vented to accommodate the stripping requirements.
Normal design practice is to calculate the steam required for heating
and then make sure that the flow is sufficient for stripping as well.

COOLING TOWER
Cooling towers are heat removal devices used to transfer process waste
heat to the atmosphere. Cooling towers may either use the evaporation
of water to remove process heat and cool the working fluid or, in the
case of closed circuit dry cooling towers, rely solely on air to cool the
working fluid. The primary use of large, industrial cooling towers is to
remove the heat absorbed in the circulating cooling water systems used
in power plants. The circulation rate of cooling water in a typical 700
MW coal-fired power plant with a cooling tower amounts to about
71,600 cubic meters an hour and the circulating water requires a supply
water make up rate of perhaps 5 %. Facilities such as power plants, steel
processing plants use field erected type cooling towers due to their
greater capacity to reject heat.
With respect to the heat transfer mechanism employed, the main types
are:
•Dry cooling towers operate by heat transfer through a surface
that separates the working fluid from ambient air, such as in a tube
to air heat exchanger, utilizing convective heat transfer. They do
not use evaporation.
•Wet cooling towers or open circuit cooling towers operate on the
principle of evaporative cooling. The working fluid and the
evaporated fluid (usually water) are one and the same.
Fluid coolers or closed-circuit cooling towers are hybrids that pass the
working fluid through a tube bundle, upon which clean water is sprayed
and a fan-induced draft applied. The resulting heat transfer performance
is much closer to that of a wet cooling tower, with the advantage
provided by a dry cooler of protecting the working fluid from
environmental exposure and contamination the pumps are vertical
multi-stage bowl diffuser type, arranged inside a suction barrel. The
condensate pump is normally located adjacent to the main condenser
hot well often directly below it. The condensate water is drawn from the
condenser by the extraction pumps and sent to the low-pressure feed
heaters.
 BOILER FEED PUMP (BFP)
A boiler feed water pump is a specific type of pump used to pump feed
water into a steam boiler. The water may be freshly supplied or
returning condensate produced as a result of the condensation of the
steam produced by the boiler. It consists of two parts, first the booster
pump then the main pump. The water enters the booster pump at
7kg/cm sqr and it increases the pressure to about 20 kg/cm sqr. Then it
enters the main pump and by fluid coupling mechanism it increases the
pressure to 150 kg/cm sqr. It is achieved by increasing the speed to
about 5700 r.p.m. If the amount of oil is decreased in between the fluid
coupling then the speed will decrease. Thus, a gear box is not required,
instead a device called scoop is required that removes the oil and
control the speed of rotation. It consumes the highest amount of power
about 8.8 MW.

DEMINERLISING PLANT
Raw water is passed via two small polystyrene beads filled (ion exchange
resins) beds. While The cations get exchanged with hydrogen ions in first
bed, the anions are exchanged with hydroxyl ions, in the second one.
Demineralized water also known as deionized water, water that has had
its mineral ions removed. Deionization is a physical process which uses
specially manufactured ion exchange resins which provides ion exchange
site for the replacement of the mineral salts in water with water forming
H+ and OH- ions. Because the majority of water impurities are dissolved
salts, deionization produces a high purity water that is generally similar
to distilled water, and this process is quick and without scale buildup.
De-mineralization technology is the proven process for treatment of
water. A DM Water System produces mineral free water by operating on
the principles of ion exchange, degasification, and polishing. De-
mineralized Water System finds wide application in the field of steam,
power, process, and cooling.
 ELECTRICAL & INSTRUMENTATION DEPARTMENT
B.B.G.S. Generator

UNIT 1&2 UNIT 3

Maximum Continuous Rating 250MW 250MW

Maximum Continuous Rating 294MW 294MW

Rated Power Factor 0.85 0.85

Rated Terminated Voltage 16500V 16500V

Rated Current 10291A 10291A

Frequency 50HZ 50HZ

Number of phases 3 3

The generators at BBGS are hydrogen and DM water cooled type. The
outer part of the cylinder has hydrogen operated coolers white the inner
part has the core and the windings. DM water is circulated all along the
cylinder by two AC pumps. The stator core and the rotors are cooled by
hydrogen circulated by centrifugal pumps mounted on each side of the
generator.
The rotor is made with alloy forgings with steel at the exciter end. The
rotor windings are formed from copper strips. Each end of rotor shaft is
supported by journal bearings, lubricated from Turbine Lube Oil system.
Exciter end bearing pedestal is fully insulated to prevent eddy current
circulation through bearing and oil films.
The generator field current is supplied by a static excitation system. The
current is supplied by an excitation transformer and a thyristor-
controlled rectifier. The turning gear drive is coupled to the generator
rotor and when meshed, allows turbine and generator shafts to be
rotated slowly before run up and after shut down to prevent rotor
distortion due to uneven heating.
There are 3 types of transformers in the plant namely GT(Generator
Transformer),ST(Station Transformer),UT(Unit Transformer).The GT is
used to step up the voltage generated(16.5KV) to 132KV in case of unit#1
&2,16.5KV to 220KV as the voltage generated(16.5KV) to 132KV in case of
unit#1 &2,16.5KV to 220KV as mentioned earlier. The ST & UT are used
for in-plant power of BBGS for meeting the power requirements of the
auxiliaries such as FD Fan, PA Fan, ID Fan, coal mills, conveyors,
centrifugal pumps, CW Pump etc. as well as the lighting loads of the
various buildings of the plant. The startup power of the plant is provided
by the UT which steps down the voltage from 16.5KV to 6.6K whereas
the ST taps voltage from the Bus-Bars. The specifications of the various
generators of unit#1 &2 are as follows:

GT#1, GT#2(Generator Transformer):

315 MVA,138/16.5 KV

The GT is having vector notation Yd 11(30deg lag between prim. &

section side) which is used generally as a convention.
The alternators(3-phase) of the Turbine-Generator set is Wye-connected
so that during earth fault the fault current (the sum of the currents in
the 3 phases is not equal to zero during earth fault) flows into the
ground through the neutral wire without hampering the generator.
The LV side (16.5KV) of the GT is delta connected. This is because if
there is an earth fault on the LV side of the GT then using Wye
connection will cause the fault current to flow through the neutral wire.
This fault current may enter into the generator circuit through the
neutral wire of the Wye connected generator & hamper the generator.
To avoid such a situation LV side(16.5KV) of the GT is delta connected.
The HV side of the GT which is connected to the transmission line is Wy
connected.
The neutral wire for bypassing the fault current is connected tong
(Neutral Grounding Transformer) which steps down the current to a
smaller value that the fault current does not hamper any devices.

• Unit Transformer: (UT#1)

➢ HV/LV1/LV2
➢ 40/25/15MVA
➢ 16.5/6.5/6.5 KV
➢
• Station Transformer: (ST#1)

➢ HV/LV1/LV2
➢ 60/30/30MVA
➢ 132/6.9/6.9KV
The UT has two LV sides namely LV1 & LV2 having voltage rating of 6.
5KVeach.These two LV sides are used to charge the UB-1A & UB-1B (Unit
Board) through the incomers which are connected to UT-1. The UT is
used to charge the UB-1A & UB-1B.

The UB#1A & UB#1B are charged by UT- 1.The SB# 1A & SB#1B are
charged by the ST-1.Similar is the case for unit# 2.The UB caters to the
independent drives (coal mills, CW PP, FD FAN, ID FAN etc.) which are
different for each unit whereas the SBcaters to the dependent drives
(Intake PP, coal plant etc.) which are the same for all the units.
We observe that UB#1A caters to a number of auxiliaries such as PD FAN, IDFAN,
COAL MILL, CW PP, ACW PP etc. whereas the UB#1B caters to BFP only. This is
because the BFP is rated with high wattage consumption whereas the
other auxiliaries are of considerably lower power consumption. Thus, is
BFP & the other auxiliaries being present on the same UB then the total
power available on the UB will the consumed by the auxiliaries itself
leaving the BFP un-operated. Thus, the BFP is present in a separate UB.
Now if due to shut down or failure of the UT#1, the LV sides of the UT
are unable to charge the UB#1A & UB#1B, then the SB#1A (Station
Board 1A) & theSB#1B (Station Board 1B) are used to charge the UB#1A
& UB#1B respectively with the help of a tie between the SB & UB.
A large number of circuit breakers are used in the total electrical system like SF6
gas circuit breaker (6.6 KV), Air circuit breaker (415 V) as well as a number of
isolators, insulators, earth switches, CT (Current Transformer), PT (Potential
Transformer), overload protection, Bus Coupler Breakers are used.
The 3.5m level consists of all the boards which consists of a large
number of relays, circuit breakers etc. which delivers power to the
various auxiliaries. Some of the specifications are given as follows:

INCOMER FROM ST1-LV1:

➢ The relays are Comb Flex Relays, Trip Circuit Relay, Tripping Relay, O|C & EF
Prot.
➢ Indicators such as Auto trip circuit unhealthy, Gas pressure low,
Breaker on, Breaker off, spring charged.
 SWITCHYARD
Switchyard is a very important part of the electrical circuit. It generally
consists of three buses, which are the two-main bus & one transfer bus.
A portion of the transfer bus is connected with the generating
transformers which are at 132KV for unit 1&2 and220KV for unit 3. Due
to the inequality between the two voltages, they are connected with the
interconnected transformer (ICT) to form a common bridge between the
two transformers. The transfer bus is connected in series with the main
bus 1 or main bus2 or neither of them. The line first comes from the
generating transformer and then through a series of isolators and circuit
breakers main bus 1 or the main bus 2 disconnected.
Two main bus are used as one is kept in standby mode if a fault
occurs in anyone of them then the other one can be used. The 132KV &
220KV line are also connected to the transmission line. When in one
main bus bar a fault occurs and we need to transfer the bus, let in main
bus 1 a fault occurs & we need to transfer it to main bus 2 then we first
connect the transfer bus thus for a brief moment the feeder gets the
voltage from both main bus 1 & transfer bus, then we open the main
bus 1thus for that brief moment the feeder gets the voltage from the
transfer bus only. Then we connect the main bus 2 also, thus for a brief
moment the feeder gets the voltage from both main bus 2 & transfer
bus, then we open the open the transfer bus and the feeder gets power
from main bus 2 only. The main buses are connected with the station
transformer, it steps down the voltage to about 6.9KV which is used to
drive the plant during any plant failure. There are 3 station transformers
one for each unit. When the plant will fail to generate, then the station
transformer with the help of the switchyard gets the power from other
unit and keeps the necessary machineries.