SUMMER TRAINING REPORT15 th June to 25 th July
Submitted By:-Shivani Chhabra7225ECE-2(5th sem)
ABOUT THE COMPANY
CORPORATE VISION :“A world class integrated power major, powering India's growth with increasing global presence.”
CORE VALUES :B- Business ethicsC-Customer focusO-Organisational & professional prideM-Mutual respect & trustI-Innovation & speedT-Total quality for excellence
NTPC Limited is the largest thermal power generating company of India, public sector company. It was incorporated in the year 1975 to accelerate power development in the country as a wholly owned company of the Government of India. At present, Government of India holds 89.5% of the total equity shares of the company and the balance 10.5% is held by FIIs, Domestic Banks, Public and others. Within a span of 31 years, NTPC has emerged as a truly national power company, with power generating facilities in all the major regions of the country.
NTPC LimiteD
Type Public
Founded 1975
Headquarters Delhi, India
Key peopleR S Sharma, Chairman & Managing
Director
Industry Electricity generation
Products Electricity
RevenueINR 416.37 billion (2008) or USD
18.15 billion
Net incomeINR 70.47 billion (2008) or USD
1.89 billion
Employees 23867 (2006)
Website http://www.ntpc.co.in
EVOLUTION OF NTPC
NTPC was set up in 1975 with 100% ownership by the Government of India. In the last 30 years, NTPC has grown into the largest power utility in India.
In 1997, Government of India granted NTPC status of “Navratna’ being one of the nine jewels of India, enhancing the powers to the Board of Directors.
NTPC became a listed company with majority Government ownership of 89.5%.NTPC becomes third largest by Market Capitalisation of listed companies
The company rechristened as NTPC Limited in line with its changing business portfolio and transform itself from a thermal power utility to an integrated power utility.
NTPC is the largest power utility in India, accounting for about 20% of India’s installed capacity.
THERMAL POWER PLANT
1975 1975
1997 1997
2005 2005
20042004
A thermal power station consists of all the equipments and a subsystem required to produce electricity by using a steam generating boiler fired with fossil fuels or befouls to drive an electric generator. Some prefer to use the term ENERGY CENTER because such facilities convert form of energy like nuclear energy, gravitational potential energy or heat energy (derived from the combustion of fuel) into electrical energy. Typical diagram of a coal power thermal power station-
1. Cooling water pump2. Three phase transmission line3. Step up transformer 4. Electrical generator5. Low pressure steam6. Boiler feed water pump7. Surface condenser8. Intermediate pressure steam turbine9. Steam control valve10. High pressure steam turbine11. Deaerator feed water heater12. Coal conveyer13. Coal hopper14. Coal pulverizer15. Boiler steam drum16. Boiler ash hopper17. Super heater18. Force draught (draft) fan19. Reheater20. Combustion air intake21. Economiser22. Airpreheater23. Precipitator24. Induced draught(draft) fan25. Fuel gas stack
The description of some of the components above is as follows:1. Cooling towers-
Cooling towers are eveporative coolers used for cooling water. Cooling tower use evaporation of water to reject heat from processes such as cooling the circulaing water used in oil refineries, chemical plants, power plants, etc. The tower vary in size from small roof – top units to very large hyperboloid structures that can be upto 200 meters tall and 100 meters in diameter, or rectangular structure that can be over 40 meters tall and 80 meters long. Smaller towers are normally factory built while larger ones are constructed on site. The primary use of large, industrial cooling tower system is to remove the heat absorbed in the circulating water system used in power plants, petroleum refineries, petrochemical and chemical plants, natural gas processing plants and other industrial facilities.
The absorbed heat is rejected to the atmosphere by the evaporation of some of the cooling water in mechanical forced – draft or induced draft towers or in natural draft hyperbolic shaped cooling towers as seen at most nuclear power plants.
2. Three phase transmission line- Three phase electric power is a common method of electric power transmission. It is a type of polyphase system mainly used for power motors and many other devices. In a three phase system, three circuits reach their instantaneous peak values at different times. Taking one conductor as reference, the other two conductor are delayed in time by one-third and two-third of cycle of the electrical current. This delay between phases has the effect of giving constant power over each cycle of the current and also makes it impossible to produce a rotating magnetic field in an electric motor. At the power station, an electric generator converts mechanical power into a set of electric currents one from each electromagnetic coil or winding of the generator. The currents are sinusoidal functions of time, all at the same frequency but offset in time to give different phases. In a three phase system, the phases are spaced equally giving a phase separation of one-third of one cycle. Generators output at a voltage that ranges from hundreds of volts to 30,000 volts. At the power station. Transformers step-up this voltage for suitable transmission. After numerous further conversions in the transmission and distribution network, the power is finally transformed to standard mains voltage i.e. the household voltage. The power may already have been split into single phase at this point or it may be still three phase. Where the step-down is three phase. The output of the transformer is usually star connected with the standard mains voltage being the phase neutral voltage.
3. Electrical generator- An electrical generator is a device that coverts mechanical energy to electrical energy, using electromagnetic induction whereas electrical energy is converted to mechanical energy with the help of electric motor. The source of mechanical energy may be a reciprocating turbine steam engine. Turbines are made in variety of sizes ranging from small 1 hp(0.75 kW) used as mechanical drives for pumps, compressors and other shaft driven equipment to 2,000,000 hp(1,500,000 kW) turbines used to generate electricity.
4. Boiler Feed Pump- A Boiler Feed Pump is a specific type of pump used to pump water into steam boiler. The water may be freshly supplied or retuning condensation of steam produced by the boiler. These pumps are normally high pressure units that use suction from a condensate return system and can be of centrifugal pump type or positive displacement type. Construction and Operation feed water pumps range in size upto many horsepower and the electric motor is usually separated from the pump body by some form of mechanical coupling. Large industrial condensate pumps may also serve as the feed water pump. In either case, to force water into the boiler, the pump must generate sufficient pressure to overcome the steam pressure developed by the boiler. This is usually accomplished through the use of centrifugal pump. Feed water pumps usually run intermittently and are controlled by a float switch or other similar level-sensing device energizing the pump when it detect a lowered liquid level in the boiler substantially increased. Some pumps contain a two stage switch. As liquid lowers to the trigger point of the first stage, the pump is activated.
If the liquid continues to drop (perhaps because the pump has failed, its supply has been cut-off or exhausted, or its discharge is blocked),the second stage will be triggered. This stage may switch off the boiler equipment (preventing the boiler from running dry and overheating), trigger an alarm or both.
5. Control valves- Control Valves are the valves used within industrial plants and elsewhere to control operating conditions such as temperature, pressure, flow and liquid level by fully or partially opening or closing in response to signals received from controllers that compares a “set point” to a “process variable” whose value is provided by sensors that monitor changes in such conditions. The opening or closing of control valves is done by means of electrical, hydraulic or pneumatic systems.
6. Deaerator- A Deaerator is a device for air removal and used to remove dissolved gases from boiler feed water to make it non-corrosive. A deaerator typically includes a vertical domed deaeration section as the deaeration feed water tank. A steam generating boiler requires that the circulating steam, condensate and feed water should be devoid of dissolved gases, particularly corrosive ones and dissolved or suspended solids. The gases will give rise to corrosion of the metal. The solids will deposit on heating surfaces giving rise to localized heating and tube ruptures due to overheating. Deaerator level and pressure must be controlled by adjusting control valves-the level by regulating condensate flow and pressure by regulating steam flow. Most deaerators guarantee that if operated properly, oxygen in deaerated water will not exceed 7ppb by weight.
7. Feed Water Heater- A feed water heater is a power plant component used to pre heat water delivered to a steam generating boiler. Feed water heater improves the efficiency of the system. This reduces plant operating costs and also helps to avoid thermal shock to boiler metal when the feed water is introduced back into the steam cycle. Feed water heaters allow the feed water to be brought upto the saturation temperature very gradually. This minimizes the inevitable irreversibility associated with heat transfer to the working fluid(water). A belt conveyer consists of two pulleys, with a continuous loop of material- the conveyer belt that rotates around them. The pulleys are powered, moving the belt and the material on the belt forward. Conveyer belts are extensively used to transport industrial and agricultural material, such as grain, coal, ores, etc.
8. Pulverizer- A pulverizer is a device for grinding coal for combustion in a furnace in a fossil fuel power plant.
9. Boiler Steam Drum-
Steam Drums are a regular feature of water tube boilers. It is reservoir of water/steam at the top end of the water tubes in the water-tube boiler. They store the steam generated in the water tubes and act as a phase separator for the steam/water mixture. The difference in densities between hot and cold water helps in the accumulation of the “hotter”-water/and saturated –steam into steam drum. Made from high-grade steel (probably stainless) and its working involves temperatures 390’C and pressure well above 350psi (2.4MPa). The separated steam is drawn out from the top section of the drum. Saturated steam is drawn off the top of the drum. The steam will re-enter the furnace in through a super heater, while the saturated water at the bottom of steam drum flows down to the mud- drum /feed water drum by down comer tubes accessories include a safety valve, water level indicator and fuse plug. A steam drum is used in the company of a mud-drum/feed water drum which is located at a lower level. So that it acts as a sump for the sludge or sediments which have a tendency to the bottom.
10.Super Heater- A Super heater is a device in a steam engine that heats the steam generated by the boiler again increasing its thermal energy and decreasing the likelihood that it will condense inside the engine. Super heaters increase the efficiency of the steam engine, and were widely adopted. Steam which has been superheated is logically known as superheated steam; non-superheated steam is called saturated steam or wet steam; Super heaters were applied to steam locomotives in quantity from the early 20th century, to most steam vehicles, and so stationary steam engines including power stations.
11.Economizers- Economizer, or in the UK economizer, are mechanical devices intended to reduce energy consumption, or to perform another useful function like preheating a fluid. The term economizer is used for other purposes as well. Boiler, power plant, and heating, ventilating and air conditioning. In boilers, economizer are heat exchange devices that heat fluids , usually water, up to but not normally beyond the boiling point of the fluid. Economizers are so named because they can make use of the enthalpy and improving the boiler’s efficiency. They are a device fitted to a boiler which saves energy by using the exhaust gases from the boiler to preheat the cold water used the fill it (the feed water). Modern day boilers, such as those in cold fired power stations, are still fitted with economizer which is decedents of Green’s original design. In this context they are turbines before it is pumped to the boilers. A common application of economizer is steam power plants is to capture the waste hit from boiler stack gases (flue gas) and transfer thus it to the boiler feed water thus lowering the needed energy input , in turn reducing the firing rates to accomplish the rated boiler output . Economizer lower stack temperatures which may cause condensation of acidic combustion gases and serious equipment corrosion damage if care is not taken in their design and material selection.
12.Air Preheater- Air preheater is a general term to describe any device designed to heat air before another process (for example, combustion in a boiler). The purpose of the air preheater is to recover the heat from the boiler flue gas which increases the thermal efficiency of the boiler by reducing the useful heat lost in the fuel gas. As a consequence, the flue gases
are also sent to the flue gas stack (or chimney) at a lower temperature allowing simplified design of the ducting and the flue gas stack. It also allows control over the temperature of gases leaving the stack.
13.Precipitator- An Electrostatic precipitator (ESP) or electrostatic air cleaner is a particulate device that removes particles from a flowing gas (such As air) using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices, and can easily remove fine particulate matter such as dust and smoke from the air steam. ESP’s continue to be excellent devices for control of many industrial particulate emissions, including smoke from electricity-generating utilities (coal and oil fired), salt cake collection from black liquor boilers in pump mills, and catalyst collection from fluidized bed catalytic crackers from several hundred thousand ACFM in the largest coal-fired boiler application. The original parallel plate-Weighted wire design (described above) has evolved as more efficient ( and robust) discharge electrode designs were developed, today focusing on rigid discharge electrodes to which many sharpened spikes are attached , maximizing corona production. Transformer –rectifier systems apply voltages of 50-100 Kilovolts at relatively high current densities. Modern controls minimize sparking and prevent arcing, avoiding damage to the components. Automatic rapping systems and hopper evacuation systems remove the collected particulate matter while on line allowing ESP’s to stay in operation for years at a time.
14.Fuel gas stack- A Fuel gas stack is a type of chimney, a vertical pipe, channel or similar structure through which combustion product gases called fuel gases are exhausted to the outside air. Fuel gases are produced when coal, oil, natural gas, wood or any other large combustion device. Fuel gas is usually composed of carbon dioxide (CO2) and water vapor as well as nitrogen and excess oxygen remaining from the intake combustion air. It also contains a small percentage of pollutants such as particulates matter, carbon mono oxide, nitrogen oxides and sulfur oxides. The flue gas stacks are often quite tall, up to 400 meters (1300 feet) or more, so as to disperse the exhaust pollutants over a greater aria and thereby reduce the concentration of the pollutants to the levels required by governmental environmental policies and regulations.
ELECTRICITY GENERATION PROCESS
(A BASIC OVERVIEW)At NTPC the man two paths are the flue gas or air cycle and steam or condensate paths.
CAPITAL OVERHAUL
NTPC has been in news due to extensive load sheds in many areas in delhi and the main cause behind these load sheds was the capital overhaul of one of 210 MW units. Unit IV was under an extensive check , which has caused shut down of the plant and the plant, was dismantled completely to change the old parts and cleaning up the whole unit. But capital overhaul has no meaning because such a deep checking of the plant happens once in five to seven years.
HOW ELECTRICITY IS GENERATED?
Thermal power station burns fuel and uses the resultant heat to raise steam which drives the TURBO GENERATOR. The fuel may be ‘fossil’(coal,oil,natural gas) or it may be fissionable, whichever fuel is used, the objective is same to convert the mechanical energy into electricity by rotating a magnet inside a set of winding.
COAL TO STAEM
Its other raw materials are air and water. The coal brought to the station by trains or by other means, travels handling plant by conveyer belts, travels from pulverizing mills, which grind it as fine as the face powder of size upto 20 microns. The finely produced coal mixed with preheated air is then blown into the boiler by a fan called primary air fan where it burns more like a gas than as a solid, in the conventional domestic or industrial grate, with additional amount of air, called secondary air supply, by forced draft fan.
As coal is ground so finally the resultant ash is also a fine powder. Some of it binds together to form pumps, which falls into ash pits at the bottom of the furnace. The water-quenched ash from the bottom is conveyed to pits for subsequent disposal or sale. Most of ash, still in fine partical form is carried out of boilers to the precipitator as dust, where electrodes charged with high voltage electricity trap it. The dust is then conveyed to water to disposal area or to bunker for sale while the clean flue gases are passed on through IP fans to be discharged through chimneys.
The heat released from the coal has been absorbed by the many kilometers tubing which line the boiler walls. Inside the tubes the boiler feed water, which is transformed by heat into staemat high temperature and pressure.. The steam superheated in further tubes (superheaters) passes to turbine where it is discharged through the nozzle on the turbine blades. Just as the energy of wind turns the sail of the windmill, the energy of steam striking the blade makes the turbine rotate.
Coupled to the end of the turbine is the rotor of the generator. The rotor is housed inside the stator having heavy coils of the bars in which electricity is produced through the
movement of magnetic field created by the rotor. Electricity passes from stator windings to step-up transformer which increases its voltage so that it can be transmited efficiently over lines of grid.
The staem which has given up its heat energy is cahnged back into water in a condenser so that it is ready for re-use. The condenser contains many kilometers of tubing through which cold water is constantly pumped. The staem passing around the tubes looses heat.Thus it is rapidly changed back into water.
But, the two lots of water, that is, the boiler feed and cooling water must never mix. Cooling water is drawn from river- bed, but the boiler feed water must be absolutely pure, far purer than the water we drink (de-mineralized water), otherwise it may damage the boiler tubes.
TABLES OF CYCLES COAL CYCLE
CONDENSATE CYCLE
FEED WATER CYCLE
STEAM CYCLE
CONTROL AND INSTRUMENTATION
This division basically calibrates various instruments and takes care of any faults occur in any of the auxiliaries in the plant.
This department is the brain of the plant because from the relays to transmitters followed by the electronic computation chipsets and recorders and lastly the controlling circuitry, all fall under this.
Instrumentation can be well defined as a technology of using instruments to measure and
control the physical and chemical properties of a material.
Control and instrumentation has following labs:
1. Manometry lab
2. Protection and interlocks lab
3. Automation lab
4. Electronics lab
5. Water treatment plant
6. Furnaces Safety Supervisory System Lab
1. Manometry lab
Transmitters- Transmitter is used for pressure measurements of gases and liquids,
its working principle is that the input pressure is converted into electrostatic
capacitance and from there it is conditioned and amplified. It gives an output of 4-
20 ma DC. It can be mounted on a pipe or a wall. For liquid or steam
measurement transmitters is mounted below main process piping and for gas
measurement transmitter is placed above pipe.
Manometer- It’s a tube which is bent, in U shape. It is filled with a liquid. This
device corresponds to a difference in pressure across the two limbs.
Bourden Pressure Gauge- It’s an oval section tube. Its one end is fixed. It is
provided with a pointer to indicate the pressure on a calibrated scale. It is of two
types : (a) Spiral type : for low pressure measurement and (b) Helical type : for
high pressure measurement
2. Protection and Interlock Lab
Interlocking- It is basically interconnecting two or more equipments so that if one
equipments fails other one can perform the tasks. This type of interdependence is
also created so that equipments connected together are started and shut down in
the specific sequence to avoid damage. For protection of equipments tripping are
provided for all the equipments. Tripping can be considered as the series of
instructions connected through OR GATE. When The main equipments of this lab
are relay and circuit breakers. Some of the instrument uses for protection are: 1.
RELAY It is a protective device. It can detect wrong condition in electrical
circuits by constantly measuring the electrical quantities flowing under normal
and faulty conditions. Some of the electrical quantities are voltage, current, phase
angle and velocity. 2. FUSES It is a short piece of metal inserted in the circuit,
which melts when heavy current flows through it and thus breaks the circuit.
Usually silver is used as a fuse material because: a) The coefficient of expansion
of silver is very small. As a result no critical fatigue occurs and thus the
continuous full capacity normal current ratings are assured for the long time. b)
The conductivity of the silver is unimpaired by the surges of the current that
produces temperatures just near the melting point. c) Silver fusible elements can
be raised from normal operating temperature to vaporization quicker than any
other material because of its comparatively low specific heat.
Miniature Circuit Breaker- They are used with combination of the control circuits
to. a) Enable the staring of plant and distributors. b) Protect the circuit in case of a
fault. In consists of current carrying contacts, one movable and other fixed. When
a fault occurs the contacts separate and are is stuck between them. There are three
types of -MANUAL TRIP - THERMAL TRIP - SHORT CIRCUIT TRIP.
Protection and Interlock System- 1. HIGH TENSION CONTROL CIRCUIT For
high tension system the control system are excited by separate D.C supply. For
starting the circuit conditions should be in series with the starting coil of the
equipment to energize it. Because if even a single condition is not true then
system will not start. 2. LOW TENSION CONTROL CIRCUIT For low tension
system the control circuits are directly excited from the 0.415 KV A.C supply.
The same circuit achieves both excitation and tripping. Hence the tripping coil is
provided for emergency tripping if the interconnection fails.
3. Automation Lab
This lab deals in automating the existing equipment and feeding routes. Earlier,
the old technology dealt with only (DAS) Data Acquisition System and came to be
known as primary systems. The modern technology or the secondary systems are coupled
with (MIS) Management Information System. But this lab universally applies the
pressure measuring instruments as the controlling force. However, the relays are also
provided but they are used only for protection and interlocks.
4. Pyrometry Lab
Liquid in glass thermometer - Mercury in the glass thermometer boils at 340
degree Celsius which limits the range of temperature that can be measured. It is L
shaped thermometer which is designed to reach all inaccessible places.
Ultra violet censor- This device is used in furnace and it measures the intensity of
ultra violet rays there and according to the wave generated which directly
indicates the temperature in the furnace.
Thermocouples - This device is based on SEEBACK and PELTIER effect. It
comprises of two junctions at different temperature. Then the emf is induced in
the circuit due to the flow of electrons. This is an important part in the plant.
RTD(Resistance temperature detector) - It performs the function of thermocouple
basically but the difference is of a resistance. In this due to the change in the
resistance the temperature difference is measured. In this lab, also the measuring
devices can be calibrated in the oil bath or just boiling water (for low range
devices) and in small furnace (for high range devices).
5. Furnace Safety and Supervisory System Lab
This lab has the responsibility of starting fire in the furnace to enable the burning of coal.
For first stage coal burners are in the front and rear of the furnace and for the second and
third stage corner firing is employed. Unburnt coal is removed using forced draft or
induced draft fan. The temperature inside the boiler is 1100 degree Celsius and its height
is 18 to 40 m. It is made up of mild steel. An ultra violet sensor is employed in furnace to
measure the intensity of ultra violet rays inside the furnace and according to it a signal in
the same order of same mV is generated which directly indicates the temperature of the
furnace. For firing the furnace a 10 KV spark plug is operated for ten seconds over a
spray of diesel fuel and pre-heater air along each of the feeder-mills. The furnace has six
feeder mills each separated by warm air pipes fed from forced draft fans. In first stage
indirect firing is employed that is feeder mills are not fed directly from coal but are fed
from three feeders but are fed from pulverized coalbunkers. The furnace can operate on
the minimum feed from three feeders but under not circumstances should any one be left
out under operation, to prevent creation of pressure different with in the furnace, which
threatens to blast it.
6. Electronics Lab
This lab undertakes the calibration and testing of various cards. It houses various types of
analytical instruments like oscilloscopes, integrated circuits, cards auto analyzers
etc.Various processes undertaken in this lab are: 1. Transmitter converts mV to mA. 2.
Auto analyzer purifies the sample before it is sent to electrodes. It extracts the magnetic
portion.
AUTOMATION AND CONTROL SYSTEM
AUTOMATION: THE DEFINITION
The word automation is widely used today in relation to various types of applications,
such as office automation, plant or process automation.
This subsection presents the application of a control system for the automation of a
process / plant, such as a power station. In this last application, the automation actively
controls the plant during the three main phases of operation: plant start-up, power
generation in stable or put During plant start-up and shut-down, sequence controllers as
well as long range modulating controllers in or out of operation every piece of the plant,
at the correct time and in coordinated modes, taking into account safety as well as
overstressing limits.
During stable generation of power, the modulating portion of the automation system
keeps the actual generated power value within the limits of the desired load demand.
During major load changes, the automation system automatically redefines new set points
and switches ON or OFF process pieces, to automatically bring the individual processes
in an optimally coordinated way to the new desired load demand. This load transfer is
executed according to pre- programmed adaptively controlled load gradients and in a safe
way.
AUTOMATION: THE BENEFITS
The main benefits of plant automation are to increase overall plant availability and efficiency. The increase of these two factors is achieved through a series of features summarized as follows:
Optimisation of house load consumption during plant start- up, shut-down and operation, via:
Faster plant start-up through elimination of control errors creating delays. Faster sequence of control actions compared to manual ones. Figures 1 shows
the sequence of a rapid restart using automation for a typical coal-fired station. Even a well- trained operator crew would probably not be able to bring the plant to full load in the same time without considerable risks.
Co-ordination of house load to the generated power output.
Ensure and maintain plant operation, even in case of disturbances in the control system, via:
Coordinated ON / OFF and modulating control switchover capability from a sub process to a redundant one.
Prevent sub-process and process tripping chain reaction following a process component trip.
Reduce plant / process shutdown time for repair and maintenance as well as repair costs, via:
Protection of individual process components against overstress (in a stable or unstable plant operation).
Bringing processes in a safe stage of operation, where process components are protected against overstress
PROCESS STRUCTURE
Analysis of processes in Power Stations and Industry advocates the advisability of
dividing the complex overall process into individual sub-processes having distinctly
defined functions. This division of the process in clearly defined groups, termed as
FUNCTIONAL GROUPS, results in a hierarchical process structure. While the
hierarchical structure is governed in the horizontal direction by the number of drives
(motorised valves, fans, dampers, pumps, etc.) in other words the size of the process; in
the vertical direction, there is a distinction made between three fundamental levels, these
being the: -
Drive Level
Function Group Level
Unit Level.
To the Drive Level, the lowest level, belong the individual process equipment and
associated electrical drives.
The Function Group is that part of the process that fulfils a particular defined task e.g.,
Induced Draft Control, Feed Water Control, Blooming Mill Control, etc. Thus at the time
of planning it is necessary to identify each function group in a clear manner by assigning
it to a particular process activity. Each function group contains a combination of its
associated individual equipment drives. The drive levels are subordinate to this level. The
function groups are combined to obtain the overall process control function at the Unit
Level.
The above three levels are defined with regard to the process and not from the control
point of view.
CONTROL SYSTEM STRUCTURE
The primary requirement to be fulfilled by any control system architecture is that it be
capable of being organized and implemented on true process-oriented lines. In other
words, the control system structure should map on to the hierarchy process structure.
BHEL’s PROCONTROL P®, a microprocessor based intelligent remote multiplexing
system, meets this requirement completely.
SYSTEM OVERVIEW
The control and automation system used here is a micro based intelligent multiplexing
system This system, designed on a modular basis, allows to tighten the scope of control
hardware to the particular control strategy and operating requirements of the process
Regardless of the type and extent of process to control provides system uniformity and
integrity for:
Signal conditioning and transmission
Modulating controls
CONTROL AND MONITORING MECHANISMS
There are basically two types of Problems faced in a Power Plant
Metallurgical
Mechanical
Mechanical Problemcan be related to Turbines that is the max speed permissible for a
turbine is 3000 rpm , so speed should be monitored and maintained at that level
Metallurgical Problem can be view as the max Inlet Temperature for Turbile is 1060 oC
so temperature should be below the limit.
Monitoring of all the parameters is necessary for the safety of both:
Employees
Machines
So the Parameters to be monitored are :
Speed
Temperature
Current
Voltage
Pressure
Eccentricity
Flow of Gases
Vaccum Pressure
Valves
Level
Vibration
PRESSURE MONITORING
Pressure can be monitored by three types of basic mechanisms
Switches
Gauges
Transmitter type
For gauges we use Bourden tubes : The Bourdon Tube is a non liquid pressure
measurement device. It is widely used in applications where inexpensive static pressure
measurements are needed.
A typical Bourdon tube contains a curved tube that is open to external pressure input on
one end and is coupled mechanically to an indicating needle on the other end, as shown
schematically below.
Typical Bourdon Tube Pressure Gages
For Switches pressure swithes are used and they can be used for digital means of
monitoring as swith being ON is referred as high and being OFF is as low.
All the monitored data is converted to either Current or Voltage parameter.
The Plant standard for current and voltage are as under
Voltage : 0 – 10 Volts range
Current : 4 – 20 milliAmperes
We use 4mA as the lower value so as to check for disturbances and wire breaks.
Accuracy of such systems is very high .
ACCURACY : + - 0.1 %
The whole system used is SCADA baseD.Programmable Logic Circuits ( PLCs) are used in the process as they are the heardt of Instrumentation .
Pressure
Electricity StartLevel low Pressure in line Level High
High level pumpElectricity Stop
Pressure
Electricity
BASIC PRESSURE CONTROL MECHANISM
TEMPERATURE MONITORING
HL switch
LL switch
AND
OR
We can use Thernocouples or RTDs for temperature monitoring
Normally RTDs are used for low temperatures.
Thermocoupkle selection depends upon two factors:
Temperature Range
Accuracy Required
Normally used Thermocouple is K Type Thermocouple:
Chromel (Nickel-Chromium Alloy) / Alumel (Nickel-Aluminium Alloy)
This is the most commonly used general purpose thermocouple. It is inexpensive and,
owing to its popularity, available in a wide variety of probes. They are available in the
−200 °C to +1200 °C range. Sensitivity is approximately 41 µV/°C.
RTDs are also used but not in protection systems due to vibrational errors.
We pass a constant curre t through the RTD. So that if R changes then the Voltage also
changes
RTDs used in Industries are Pt100 and Pt1000
Pt100 : 0 0C – 100 Ω ( 1 Ω = 2.5 0C )
Pt1000 : 0 0C - 1000Ω
Pt1000 is used for higher accuracy
The gauges used for Temperature measurements are mercury filled Temperature gauges.
For Analog medium thermocouples are used
And for Digital medium Switches are used which are basically mercury switches.
FLOW MEASUREMENT
Flow measurement does not signify much and is measured just for metering purposes and
for monitoring the processes
ROTAMETERS:
A Rotameter is a device that measures the flow rate of liquid or gas in a closed tube. It is
occasionally misspelled as 'rotometer'.
It belongs to a class of meters called variable area meters, which measure flow rate by
allowing the cross sectional area the fluid travels through to vary, causing some
measurable effect.
A rotameter consists of a tapered tube, typically made of glass, with a float inside that is
pushed up by flow and pulled down by gravity. At a higher flow rate more area (between
the float and the tube) is needed to accommodate the flow, so the float rises. Floats are
made in many different shapes, with spheres and spherical ellipses being the most
common. The float is shaped so that it rotates axially as the fluid passes. This allows you
to tell if the float is stuck since it will only rotate if it is not.
For Digital measurements Flap system is used.
For Analog measurements we can use the following methods :
Flowmeters
Venurimeters / Orifice meters
Turbines
Massflow meters ( oil level )
Ultrasonic Flow meters
Magnetic Flowmeter ( water level )
Selection of flow meter depends upon the purpose , accuracy and liquid to be measured
so different types of meters used.
Turbine type are the simplest of all.
They work on the principle that on each rotation of the turbine a pulse is generated and
that pulse is counted to get the flow rate.
VENTURIMETERS :
Referring to the diagram, using Bernoulli's equation in the special case of incompressible
fluids (such as the approximation of a water jet), the theoretical pressure drop at the
constriction would be given by (ρ/2)(v22 - v1
2).
And we know that rate of flow is given by:
Flow = k √ (D.P)
Where DP is Differential Presure or the Pressure Drop.
CONTROL VALVES
A valve is a device that regulates the flow of substances (either gases, fluidized solids,
slurries, or liquids) by opening, closing, or partially obstructing various passageways.
Valves are technically pipe fittings, but usually are discussed separately.
Valves are used in a variety of applications including industrial, military, commercial,
residential, transportation. Plumbing valves are the most obvious in everyday life, but
many more are used.
Some valves are driven by pressure only, they are mainly used for safety purposes in
steam engines and domestic heating or cooking appliances. Others are used in a
controlled way, like in Otto cycle engines driven by a camshaft, where they play a major
role in engine cycle control.
Many valves are controlled manually with a handle attached to the valve stem. If the
handle is turned a quarter of a full turn (90°) between operating positions, the valve is
called a quarter-turn valve. Butterfly valves, ball valves, and plug valves are often
quarter-turn valves. Valves can also be controlled by devices called actuators attached to
the stem. They can be electromechanical actuators such as an electric motor or solenoid,
pneumatic actuators which are controlled by air pressure, or hydraulic actuators which
are controlled by the pressure of a liquid such as oil or water.
So there are basically three types of valves that are used in power industries besides the
handle valves. They are :
Pneumatic Valves – they are air or gas controlled which is compressed to
turn or move them
Hydraulic valves – they utilize oil in place of Air as oil has better
compression
Motorised valves – these valves are controlled by electric motors
FURNACE SAFEGUARD SUPERVISORY SYSTEM
FSSS is also called as Burner Management System (BMS). It is a microprocessor based programmable logic controller of proven design incorporating all protection facilities required for such system. Main objective of FSSS is to ensure safety of the boiler.
The 95 MW boilers are indirect type boilers. Fire takes place in front and in rear side. That’s why its called front and rear type boiler.
The 210 MW boilers are direct type boilers (which means that HSD is in direct contact with coal) firing takes place from the corner. Thus it is also known as corner type boiler.
IGNITER SYSTEM
Igniter system is an automatic system, it takes the charge from 110kv and this spark is brought in front of the oil guns, which spray aerated HSD on the coal for coal combustion. There is a 5 minute delay cycle before igniting, this is to evacuate or burn the HSD. This method is known as PURGING.
PRESSURE SWITCH
Pressure switches are the devices that make or break a circuit. When pressure is applied , the switch under the switch gets pressed which is attached to a relay that makes or break the circuit.Time delay can also be included in sensing the pressure with the help of pressure valves.Examples of pressure valves:
1. Manual valves (tap)
2. Motorized valves (actuator) – works on motor action
3. Pneumatic valve (actuator) _ works due to pressure of compressed air
4. Hydraulic valve
NTPC OVERALL LAYOUT
Coal is handled and processed. It is then sent to the units 1,2,3,4.
Units 1 and 2 are linked with chimney 1 which consists of 2 chimneys internally.
Similarly units 3 and 4 are linked with chimney 2.
Each unit is linked with cooling towers in order to cool the steam. Sea water
pump house links with cooling towers in order to supply Sea water as a coolant.
DM plant links all the units in order to supply DM water.
Yeleru Reservoir Canal is linked with DM plant to supply water.
Every unit is linked with power handling and transmission station where power is
transmitted to the power grid.
Also, each unit is linked with Ash pond through Ash dispenser.
GENERAL THERMAL POWER PLANT LAYOUT
1. Cooling Tower 10. Steam Control Valve 19. Superheated
2. Cooling Water Pump11. High Pressure Steam
Turbine
20. Forced Draught
(Draft) Fan
3. Transmission Line (3-Phase) 12. Deaerator 21. Reheater
4. Step-Up Transformer (3-
Phase)13. Feedwater Heater 22. Combustion Air Intake
5. Electrical Generator (3-
Phase)14. Coal Conveyor 23. Economizer
6. Low Pressure Steam Turbine 15. Coal Hopper 24. Air Preheater
7. Condensate Pump 16. Coal Pulverizer 25. Precipitator
8. Surface Condenser 17. Boiler Steam Drum26. Induced Draught
(Draft) Fan
9.Intermediate Pressure Steam
Turbine18. Bottom Ash Hopper 27. Flue Gas Stack
COAL PROCESS LAYOUT
a Coal is imported from Talcher and Australia which is transported to the plant
through rail.
a Coal wagons are handling at the Coal handling station.
a From the coal handling station, coal is either stored in Stock Yard or directly sent
to Coal Crushing mill, which crushes coal to 20mm size.
a Through Conveyor belts, coal is sent to bunkers.
a From bunkers it is sent to Coal mill where coal is milled to powdered state.
a The powdered coal is mixed with air and sent to Coal Gun.
a From Coal Gun, it is sent to the Coal Furnace.
UNIT LAYOUT 1(IN ORDER TO KNOW THE INTERNAL
OPERATION OF COAL FURNACE)
The coal furnace is surrounded by water walls which consist of DM water.
DM water is supplied from Boiler Drum to Coal Furnace which is more than 165
meters high from Coal Furnace.
Coal is supplied through coal gun.
Initially, the coal is burnt with the help of Diesel. Two kinds of Diesel are used:
HSD (High Speed Diesel) and LSD (Low Speed Diesel). First LSD is used and
then HSD is used. Later, Oil supply is stopped and coal is left for burning.
In order to ignite the furnace, DC supply is given by the DC inverters.
The heat generated by the coal furnace is more than 1200 degrees centigrade.
When water comes through the water walls, it gets heated upto 540 degrees and
turns into steam.
This steam flows to turbines at various pressures.
These turbines are linked with generators which generate power and these
generators supply power to power stations from where it is sent to power grid.
UNIT LAYOUT 2(IN ORDER TO KNOW THE INTERNAL
OPERATION OF TURBINE)
Steam generated in the coal furnace is supplied to the Economizer.
From there, it is sent to the Super heater which has an elaborate setup of tubing
where the steam vapour picks up more energy from Hot Flue gases outside the
tubing and its temperature is now super heated above the saturation temperature.
The super heater steam is then piped through the main steam lines to the walls
before the high pressure turbines. From High Pressure turbines (HP) steam is
transferred to Super Heater again and then to IP (Intermediate pressure) turbine.
The turbines are connected to generators where power is generated and sent to
power grid.
After this, the steam loses its pressure and hence is sent to low pressure turbine
(LP). Then, steam has very low pressure which cannot be used for the turbines.
Hence, it is sent to condenser which is in Vaccum.
The condenser is a shell and tube heat exchanger in which cooling water is
circulated through the tubes. The exhaust steam from the LP turbines enters the
shell where it is cooled and converted to condensate (water) by falling over the
tubes. Such condensers use steam ejectors for continuous removal of air and gases
from the steam side to maintain vaccum. This condensated steam is converted to
water by the cooling towers in which coolant is sea water.
The water from the cooling tower is sent to hot well.
From hot well, the water will go through condenser pumps through low pressure
temperature heater, then through High pressure temperature heaters. This is called
Re-heating or Re-cycling system (Deaerator system) to Boiler speed pump. Each
boiler speed pump consumes 10MW in 500MW generated power.
Deaerators to boil speed pumps and to HP heaters and to FRS (Feed Regulating
Station) to Boiler Drum.
Hence whatever DM water was vaporized is again De-vaporized to DM water
again. This comes back to Boiler Drum again.
In cyclic process, this water goes down from Boiler drum to Furnace.
In between the process of vaporizing and de-vaporizing of water, 10% of water is
lost. This lost water is made up by make up pumps which are connected to the
DM plant.
DE-MINERALIZATION PLANT LAYOUT
Water is supplied from Yeleru Canal to the reservoir. From here, this
water is pumped to DM plant.
This water is purified with the help of Aulum and Chlorine in the first
stage. This water is called Filter water.
Filter water is sent through gravity filters by which we get pure drinking
water.
This pure water is sent to Cat-ion vessel and then to Cat-ion exchanges
from here to the Degasser and then to An-ion exchanger and to mixed bed.
The water coming out of the mixer bed is 100% pure Dematerialized water
(DM).
DM water is stored in DM water tank.
The DM water tank is linked with DM water make up pump which is
again linked to boiler drum.
POWER STATION LAYOUT
The power generated through the generators is 18 Kv.
This 18 Kv power is stepped up by step-up generator to 400 Kv.
This is done in order to avoid heavy Cabling for transmission of power.
This is sent to power grid.
From Power grid, the power distributions are 400 Kv which is given to factories.
In the same way 33 Kv, 11 Kv are stepped onto 440v and again stepped onto
230v which is used to household purpose.
ORGANIZATION STRUCTURE:
CORPORATE OBJECTIVE
BUSINESS PORTFOLIO GROWTH
To further consolidate NTPCS position as the leading thermal power
generation company in India and establish a presence in hydro power
segment.
To broad base the generation mix by evaluating conventional sources of
energy to ensure long run competitiveness and mitigate fuel-risks.
To diversify across the power value chain in India by considering
backward and forward integration into areas such as power trading,
transmission, distribution, coal mining, coal beneficiation, etc.
To develop a portfolio of generation assets in international markets.
To establish a strong brand in the domestic & international market.
CUSTOMER FOCUS
To foster a collaborative style of working with customer growing to
be a preferred brand for supply of quality power.
To expand the relationship with existing customers by offering a
bouquet of services in addition to supply of power e.g. trading,
energy consulting, distribution consulting, management consulting,
management practices.
To expand the future customer portfolio through profitable
diversification into downstream business, inter alia retail
distribution and direct supply.
To ensure rapid commercial decision making, using customer
specific information with adequate concern for the interests of the
customer.
AGILE CORPORATION
To ensure effectiveness in business decisions and responsiveness to
change in the business environment by
Adopting a portfolio approach to new business development.
Continuous and coordinated assessment of the business environment to
identify and respond to opportunities and threats.
To develop a learning organization having knowledge based competitive
edge in current and future businesses.
To effectively leverage information technology to ensure speedy decision
making across the organization.
PERFORMANCE LEADERSHIP
To continuously improve on project execution time and cost in order to
sustain long run competitiveness in generation.
co operate & maintain NTPC stations at par with the best-run utilities in
the world with respect to availability, reliability, efficiencies.
To aim for performance excellence in the diversification businesses.
To embed quality in all systems and processes.
HUMAN RESORUCE DEVELOPMENT
To enhance organizational performance by institutionalizing an objective
and open performance management system.
To align individual and organizational needs and develop business leaders
by implementing a career development system.
To enhance commitment of employees by recognizing and rewarding high
performance.
To build and sustain a learning organization of competent world-class
professionals.
To institutionalize core values and create a culture of team building,
empowerment, equity, innovation and openness which would motivate
employees and enable achievement of strategic objectives.
FINANCIAL SOUNDNESS
To maintain and improve the financial soundness of NTPC by prudent
management of the financial resources.
To continuously strive to reduce the cost of capital through prudent
management of deployed funds, leveraging opportunities in domestic and
international financial markets.
To develop appropriate commercial policies and processes this would
ensure remunerative tariffs and minimize receivables.
To continuously strive for reduction in cost of power generation by
improving operating practices.
SUSTAINABLE DEVELOPMENT
To contribute to sustainable power development by discharging corporate
social responsibilities.
To lead the sector in the areas of resettlement and rehabilitation and
environment protection including effective ash-utilization, peripheral
development and energy conservation practices.
To lead developmental efforts in the Indian power sector through efforts
at policy advocacy, assisting customers in the operations and management
of power plants etc.
RESEARCH and DEVELOPMENTS
To pioneer the adoption of reliable, efficient and cost-effective
technologies by carrying out fundamental and applied research in alternate
funds and technologies.
To carry out research and development of breakthrough techniques in
power plant construction and operation that can lead to more efficient,
reliable and environment friendly operation of power plants in the country.
To disseminate the technologies to other players in the sector and in the
long-run generating revenue through proprietary technologies.
SUPPLY CHAIN MANAGEMENT
Coal is supplied from Talcher and Australia which is stored and maintained very
well at the Coal Stock yard.
There are no retailers or distributors. Everything is taken care by the government
since it is a State-owned company.
Supply of electric products are done by BHEL which is also a government owned
enterprise.
Chief water source is Yeleru canal.
Conclusion
On completion of my vocational training at NTPC Thermal Power Project, Jhajjar I have come to know about how the very necessity of our lives nowadays i.e., electricity is generated. What all processes are needed to generate and run the plant on a 24x7 basis.
NTPC Jhajjar is one of the plants in India to be under highest load factor for the maximum duration of time and that to operating at highest plant efficiencies. This plant is an example in terms of working efficiency and management of resources to all other thermal plants in our country. The operating plf of the NTPC as compared to the rest of country is the highest with 87.54% the highest since its inception. The training gave me an opportunity to clear my concepts from practical point of view with the availability of machinery of such large rating.
Acknowledgements
Everything that happens in the world is an out come of interaction of various factor, some of which are favourable while other not. Always for a desired result, the number of favourable factors is more. This work is NO exception to this fact. I acknowledge that
I’ve been fortunate enough to get the support, mentally and physically in everything that I do.
First of all I would like to thank Shri D.Mukherjee, Honourable DGM ,NTPC Jhajjar,who led the entire team of NTPC for functioning of each department in a modernized and techno-commercial atmosphere to make the project touch such peaking performance.
I greatly acknowledge the help and the mental strength provided by our entire family for encouraging me and providing me knowledge & guidance related with every deptt. of NTPC, JHAJJAR.
At last I conclude by thanking all the employees of NTPC, JHAJJAR (both executives & workers) who helped me in making our training a boon for me.
ADITYA AGARWAL