TRAININGTAKEN AT

N.T.P.C.

VINDHYACHALSUBMITED IN PARTIAL FULFILLMENT OF B. TECH DEGREE

IN

ELECTRONICS AND COMMUNICATION

SESSION :- (2009-2010)

SUBMITTED TO SUBMITTED BY

Mr. J. N. Mathur UTPAL KUMAR PAL

H. O. D. VIITH SEMESTER

Electrical branch Electronics & communication

NTPC LIMITED

INTRODUCTION

NTPC Limited or National Thermal Power Corporation Ltd is the largest thermal power generating company of India. NTPC is the sixth largest thermal power generator in the world and the second most efficient utility in terms of capacity utilization based on data of 1998. NTPC Limited is a 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. Within a span of 34 years, NTPC has emerged as a truly national power company, with power generating facilities in all the major regions of the country. POWER GENERATION IN INDIA NTPC’s core business is engineering, construction and operation of power generating plants. Presently, Government of India holds 89.5% equity in the company and the balance 10.5% is held by FIIs, Domestic Banks, Public and others. It also provides consultancy in the area of power plant constructions and power generation to companies in India and abroad. NTPC was among the first Public Sector Enterprises to enter into a Memorandum of Understanding (MOU) with the Government in 1987-88. Since then, every year, NTPC has been placed under the 'Excellent category' (the best category). In recognition of its excellent performance and tremendous potential NTPC has been given the status of "NAVRATNA" by the Government of India.

2. As on date, NTPC's total installed capacity is 30,644 MW through its 15 coal based (24,709 MW), 7 gas based (5,935 MW) and 4 Joint Venture Projects (1,054 MW). NTPC acquired 50% equity of the SAIL Power Supply Corporation Ltd. (SPSCL). This JV Company operates the captive power plants of Durgapur (120 MW), Rourkela (120 MW) and Bhilai (74 MW). NTPC also has 28.33% stake in Ratnagiri Gas & Power Private Limited (RGPPL) a joint venture company between NTPC, GAIL, Indian Financial Institutions and Maharashtra SEB Co Ltd. NTPC's coal based power stations are at: Singrauli (Uttar Pradesh), Korba (Chattisgarh), Ramagundam (Andhra Pradesh), Farakka (West Bengal), Vindhyachal (Madhya Pradesh), Rihand (Uttar Pradesh), Kahalgaon (Bihar), NTCPP (Uttar Pradesh), Talcher (Orissa), Unchahar (Uttar Pradesh), Simhadri (Andhra Pradesh), Tanda (Uttar Pradesh), Badarpur (Delhi), and Sipat

(Chattisgarh). NTPC's Gas/Liquid based power stations are located at: Anta (Rajasthan), Auraiya (Uttar Pradesh), Kawas (Gujarat), Dadri (Uttar Pradesh),

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Jhanor-Gandhar (Gujarat), Rajiv Gandhi CCPP Kayamkulam (Kerala), and Faridabad (Haryana). NTPC's Power Plants with Joint Ventures are located at Durgapur (West Bengal), Rourkela (Orissa), Bhilai (Chhattisgarh), and RGPPL (Maharashtra).

3. NTPC has emerged as a diversified power major with presence in the entire value chain of the power generation business. Apart from power generation, which is the mainstay of the company, NTPC has already ventured into consultancy, power trading, ash utilization and coal mining. NTPC is the 4th largest power generating company in Asia in terms of million units of power sold. It has been ranked 411th in the year 2007 and ranked 317th in the year 2009, in the Forbes Global 2000 ranking of the World’s biggest companies. Its size is matched by its profitability. In a recent study, leading industry analysts have placed NTPC among the five 'Top Buys' in Asia in the utility segment covering power generation, power equipment and gas.

4. NTPC has been operating its plants at high efficiency levels. Although the company has 18.79% of the total national capacity it contributes 28.60% of total power generation due to its focus on high efficiency. Further, the power capacity also increased by 495 mega watts which is the largest increase in five quarters. There has been a sharp rise in Plant Load Factor (PLF) of its gas-based generation stations which went up from 67 per cent from the year ago quarter to 80 per cent in the latest one. Among the many positive catalysts driving the company's robust future are:

a) Capacity Addition Targets of becoming 50 GW Company by 2012 and 75 GW by 2017 and maintaining sector leadership.

b) Strategic Integration along the value-chain through entry into coal mining, power equipment manufacturing, power trading, power distribution and lateral diversification into hydro, renewable and nuclear (in line with the Government policies).

c) Leading market share (about 29 per cent) and strategies to sustain and increase the market share.

5. Hydro power development NTPC is imparting special thrust on hydro power development to achieve environmental, operational and commercial synergy. Hydro plants are free of emissions, are excellent for meeting peak demand and have sound long-term economics. That is why Hydro power development is a major component

of NTPC's lateral diversification in its fuel portfolio. By the year 2017, i.e., the end of the Twelfth Plan, NTPC plans to have about 9,000 MW of hydel power capacity.

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In addition to the 800 MW Koldam Hydroelectric Project, the company’s on-going hydro projects include Loharinag- Pala (600 MW) and Tapovan Vishnugad (520 MW). The benefits in terms of fuel security and clean power generation to be obtained through nuclear power generation make it an attractive option. Resumption of India's civil nuclear cooperation with the rest of the world in the wake of the decision of the Nuclear Suppliers Group (NSG) in September 2008 enables NTPC to explore the possibility of increasing the size of its planned nuclear portfolio of 2000 mw by 2017.

ABT NTPC VINDHYACHAL

6. NTPC Vindhyachal Super Thermal Power Project is one of the most prestigious flagships of NTPC striving ahead to bridge the country generation gap especially in the western region. It was incorporated in the October 1987. The Station is located in Singrauli district in MP in the North-Western side of the country. It has secured ISO 14001 and ISO 9002 certificate in the field of environment and power generation but also in various other fields. On September 2002 it made glorious achievement by ensuring production up to 2260 MW. In 2007 total production of Vindhyachal becomes 3260MW by adding 2 units of each 500MW. And now new 2 units of 500 MW are in under process for the fourth unit of station and are likely to be completed till 2010-11. Now Vindhyachal becomes largest power plant of India. And the team of NTPC’s efficient and experienced engineers and associate is carrying out the final testing, calibration, commissioning and synchronizations of various instrument and systems. It has won number of awards from Government of India for proper utilization and consumption and has bagged the safety awards presented by U.S.A. and British safety council.

i. COAL SOURCE

The coal source of NTPC VINDHYACHAL is from Northern coalfields limited (NCL) mines at Dudhichua (7Km) and Nigahi (10Km) and Jayant (5Km). These coal mines are located in Singrauli district in MP.

ii. FUEL OIL SOURCE

Indian Oil Corporation (IOC), COLD (Customer Operated Lubricant and Oil Deposit) at Jayant (5Km).

iii. WATER SOURCE

Discharge canal of Singrauli Super Thermal Power Station (SSTPS).

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iv. BENEFICIARY STATES

Madhya Pradesh, Chattisgarh, Maharastra, Gujarat, Goa, Daman & Diu and Dadar & Nagerhaveli.

7. Vindhyachal Station belongs to the western region and feeds power to states and union territories of: Madhya Pradesh (24.4%), Chhattisgarh (4.7%), Maharashtra (32.3%), Gujarat (20.8%), Goa, Daman & Diu (2.4%), Dadar& nagerhaveli (0.4%), Unallocated (15 %).

The power flows out from Vindhyachal through 400KV power transmission system.

THERMAL POWER PLANT OVERVIEW

8. A modern boiler has capacity of burning pulverized coal at rates up to 400 tones an hour (50,000 metric ton per day). From the coal store, fuel is carried on a conveyor belt and discharged by means of a coal tipper into the bunker. It then falls perhaps through a weigher into the coal pulverizing mill where it is grounded to a powder as fine as flour. The mill usually consists of a round metal table on which large steel rollers or balls are positioned. The table revolves, forcing the coal under the rollers or balls which crush it. Air is drawn from the top of the boiler house by the Forced Draught (FD) Fan and passed through the air pre-heaters, to the hot air duct. From here some of the air passes directly to the burners and the remainder is taken through the Primary Air (PA) Fan to pulverizing mill, where it is mixed with powdered coal, blowing it along pipes to burners of the furnace. Here, it mixes with the rest of the air and burns with great heat.

9. The boiler consists of a large number of tubes extending the full height of the structure and the heat produced raises the temperature of the water circulating in them to create stem which passes to the steam drum at very high pressure. The steam is then heated further in the super heater and fed through the outlet valve to the high pressure cylinder of the steam turbine. It may be hot enough to make the steam pipe glow a dull red (around 540°C). When the steam has been through the first cylinder (High Pressure) of the turbine, it is returned to the boiler and reheated before being passed through the other cylinder (Intermediate and Low Pressure) of the turbine. From the turbine the steam passes into a condenser to be turned back into water called ‘condensate’. This is pumped through feed heaters (where it may be heated to about 250°C) to the economizer where the temperature is raised sufficiently for the condensate to be returned to the lower half of the steam drum of the boiler.

10. The flue gases leaving the boiler are used to reheat the condensate in the economizer and then pass through the air pre-heater, to the Electrostatic

Precipitor (ESP). Finally, they are drawn by the Induced Draught (ID) Fan into the main flue and to the chimney. The ash is either sold for use in road and building constructions or piped as slurry of ash and water to a settling lagoon, where the

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Water drains off. Once this lagoon (which may originally have been a worked out gravel pit) has been filled, it can be returned to agricultural use, or the ash removed for other purposes.

11. The electrostatic precipitator consists of metal plates which are electrically charged .Dust and Grit in the flue gases are attracted on to these plates, so that they do not pass up the chimney to pollute the atmosphere. Regular mechanical hammer blows cause the accumulations of ash, dust and grit to fall to the bottom of the precipitator, where they collect in a hopper for disposal. Additional accumulations of ash also collect in the hoppers beneath the furnace.

CONVERSION OF STEAM TO MECHANICAL POWER

12. From the boiler, a steam pipe conveys steam to the turbine through a stop valve (which can be used to shut off steam in an emergency) and through control valves that automatically regulate the supply of the steam to the turbine. Stop valve and control valves are located in a steam chest and a governor, driven from the main turbine shaft, operates the control valves to regulate the amount of steam used. (This depends upon the speed of the turbine and the amount of electricity required from the generator). Steam from the control valves enters the high pressure cylinder of the turbine, where it passes through a ring of stationary blades fixed to the cylinder wall. These act as nozzles and direct the steam onto a second ring of moving blades mounted on a disc secured to the turbine shaft .This second ring turns the shafts as a result of the force of the steam. The stationary and moving blades together constitute a ‘stage’ of the turbine and in practice many stages are necessary, so that the cylinder contains a number of rings of stationary blades with rings of moving blades arranged between them. The steam passes through each stage in turn until it reaches the end of the high pressure cylinder and in its passage some of its heat energy is changed into mechanical energy.

13. The steam leaving the high pressure cylinder goes back to the boiler for reheating and returns by further pipe to the intermediate pressure cylinder. Here it passes through another series of stationary and moving blades. Finally ,the steam is taken to the low pressure cylinders, each of which it enters at the centre flowing outwards in opposite directions through the rows of turbine blades – an arrangement known as double flow – to the extremities of the cylinder. As the steam gives up its heat energy to dive the turbine, its temperature and pressure fall and it expands .Because of this expansion and blades are much larger and longer towards the low pressure ends of the turbine.

14. The turbine shaft usually rotates at 3000 revolutions per minute. This speed is determines by the frequency of the electricity system used in this country and is the speed at which a 2- pole generator must be driven to generate alternating current

at a frequency of 50 cycles per second. When as much energy as possible has been taken from the steam it is exhausted directly to the condenser. This runs the length of the low pressure part of the turbine and may be beneath or on either side of it.

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The condenser consists of a large vessel containing some 20,000 tubes, each about 25 mm in diameter. Cold water from river, estuary, sea or cooling tower is circulated through these tubes and as the steam from the turbine passes round them it is rapidly condensed into water – condensate .Because water has a much smaller comparative volume than steam, a vacuum is created in the condenser. This allows the steam to be used down to pressures below that of the normal atmosphere and more energy can be utilized.

15. From the condenser, the condensate is pumped through low pressure feed heaters by the extraction pump, after which its pressure is raised to boiler pressure by the boiler feed pump. It is passed through further feed heaters to the economizer and the boiler for reconversion into steam. Where the cooling water for power station s is drawn from large rivers, estuaries or the coast, it can be returned directly to the source after use. Power stations situated on smaller rivers and inland do not have such vast water resources available, so the cooling water is passed through cooling towers (where its heat is removed by evaporation) and re- used.A power station generating 2000000kw of electricity required about 227,500 cubic meters water an hour for cooling purposes. Where cooling towers are used, about one hundredth part of its source to carry away any impurities that collect. Most of it, however, is recalculated.

SWITCHING AND TRANSMISSION

16. The electricity is usually produced in the stator windings of large modern generators at about 25000 volts and is fed through terminal connections to one side of a generator transformer that step up the voltage to 132 KV or 400KV. From here conductors carry it to a series of three switches comprising an isolator, a circuit –breaker (CB) and another isolator. The circuit- breaker, which is heavy – duty switch capable of operating in a fraction of a second, is used to switch off the current flowing to the transmission lines. Once the current has been interrupted the isolators can be opened. These isolate the CB from all outside electrical sources, so that there is no chance of any high voltages being applied to its terminal s. maintenance or repair work can then be carried out in safety. From the CB the current is taken to the bus bars – conductors which run the length of the switching compound- and then to another CB with its associated isolators, before being fed to the grid .Each generator in a power station has its own transformer, CB and associated isolators but the electricity generated is fed on to a common set of bus bars.17. CB’s work like combined switches and fuses but they have certain special features and are very different from the domestic switch and fuse. When electrical current is switched off by separating two contacts, an arc is created between them. At the voltage used in the home, this arc is very small and only lasts for a fraction of a second but at very high voltage s used for transmission ,the size and power of the

arc is considerable and it must be quickly quenched to prevent damage. One type of CB has its contact immersed in insulating oil so that when the switch is opened , either by powerful electrical coils or mechanically by springs the arc is quickly

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Extinguished by the oil. Another type works by compressed air which operates the switch and at the same time ‘blows out’ the arc.Three wires are used in a three phase system for large power transmission as it is cheaper than two wire ‘single phase’ system that supplies the home. The centre of the power station is control room .Here engineer monitor the output of the electricity, supervising and controlling the operation of generating plant and high voltage switch- gear and directing power to the grid system as required .Instruments on the control panels show the output and conditions which exist on all the main plant and a miniature diagram indicates the precise state of the electrical system.

COAL HANDLING PLANT

18. As we all know, the coal and water are the main inputs for power generation. The thermal energy of coal is processed and converted to electricity. For 3,260 MW VSTPP stage-I, II & III, we need on an average 50,000 MT of coal a day; which means we are entrusts the tandem task of handling, processing and feeding approx. 20 million MT of coal in a year.

19. In CHP, coal is received at track hopper from mines through BOBR Wagons. The unloaded coal is scooped into conveyor & subjected to further process of removal of extraneous material & crushing to -20 mm size. After crushing, the coal again screened for elimination of extraneous materials, weighed and sent to boiler bunkers. Excess coal, if any, is sent to coal yard for stacking. During this process, the coal is passed through suspended magnet, magnetic separators, metal detectors, belt weighers to ensure that sized coal, free of foreign material is supplied to the power station.

20. The coal supply is from mines of Northern Coal Fields Ltd., coal industry being labour intensive and open cast mining is done, and the coal supply varies over a wide band through- out the year. During summer, under scorching sun and in rainy season due to water entry in mines and slippery road, the coal production goes down and remains highly unstable. Coal production is at peak normally during November-March. However, the coal requirement for the power station is more or less uniform. This makes the job of coal handling plant, challenging. The coal yard is open in peak time; the coal stock goes up to 8 lacks MT. The coal is known for spontaneous combustion. To prevent this, coal yard management has to be done properly. The coals heaps are sprayed with water and compacted by running Dozers. This prevents air pockets in coal heaps, helps in fire protection and preserve volatile materials to maintain calorific value of the fuel.

21. The coal conveyors work as a chain. The start & stop of conveyors are linked with preceding/succeeding conveyors. If a conveyor trips, all the preceding conveyors have to get tripped immediately. Any failure of protection or delayed

tripping will result in huge coal spillage. This makes the protections and interlocks more vital and important in CHP. It is worthwhile to mention that total conveyor

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length is above 10 KMs and manual surveillance everywhere is quiet difficult and cumbersome job and heights.

CONTROL & INSTRUMENTATION

22. Control and instrumentation in any process industry, can be compared to the nerve system in the human being. The way the nerve system controlling the operation of various limbs of human being, C & I in the same way controlling and operating various motors, pumps, dampers, valves etc. and helping us to achieve our targets. Control and instrumentation, as the name indicates, is a branch in engineering which deals with various measurement, indication, transmission and control in different technical fields. The latest development made in the area of instrumentation is so wide that it has become humanly impossible to master over all the system individually. Even in instrumentation there are further sub groups now. The term instrument means “A device or combination of devices used directly or indirectly to measure and display a variable.”

23. For safe & efficient operation of power plant, it is of paramount importance to monitor all power plant parameter such as: temperature, pressure, flow, level, etc. In a power plant control & instrumentation is synonymous to the nerves & brain of human being. All the parameters is measured and communicated to control room. The processing is done in control room and commands were given to field control drives to attain the desire plant conditions.

SELECTION OF INSTRUMENTS

24. Instruments engineers are required to work in close association with the system design as well as the equipment design engineers in selecting instruments and sensing system. After deciding the capacity of Thermal Power Station the designs of Boiler turbine and auxiliary equipments such as mills, pumps, fans, de-aerator, feed heaters etc. are taken up. Based on the design of the main and the auxiliary equipments, the parameter values for efficient and economic operation determined load are specified. The instrument and system design engineers decide the location for the measurement of various parameters such as level, pressure, flow, differential pressure, temperature and other parameters based on the system design and layout conditions. Then the instrument engineers select the appropriate instruments influenced by following factors:

a) Required accuracy of measurement

b) Range of Measurement

c) The form of final data display required

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d) Process media

e) Cost

f) Calibration and repair facilities required/ available

g) Layout restriction

h) Maintenance requirement/ availability

POWER STATION INSTRUMENTION

25. The process conditions and the equipment conditions are to be assessed by the operators from the information received from the various instruments. The instruments and range vary very widely as per the process media. The following section deals with these instruments. The inter dependence and inter relation of these instrument readings play very significant role in the stability and the efficiency of the heat balance.

MEASURING INSTRUMENT

26. All primary measuring instruments are installed include: temperature sensing element/ wells/ cold junction compensation boxes, Flow sensing elements (orifice plates, flow nozzles & annular), electronic transmitter, flue gas analysis instruments, Vibration Monitoring System, local indicators, process actuator switches, electro/ pneumatic converters, coal bunker level indicating system. The secondary instruments like recorders. Indicators, analyzer monitors, integrators and electrical meters etc. are mounted on control panels to provide maximum accessibility, optimum operability. The instruments are arranged such that, failure of any device will not cause any malfunction towards process/ operation.

PROTECTION OF OVERHEAD LINES AND CABLE CIRCUITS

27. Overhead lines are amongst the most fault susceptible items in plant in a modern power system. It is therefore essential that the protection associated with them provides secure and reliable operation for distribution systems, continuity of supply is of paramount importance. The majority of faults on overhead lines are transient or semi-permanent in nature; multi-shot auto reclose cycles are commonly used in conjunction with instantaneous tripping elements to increase system availability. Thus, high speed fault clearance is often a fundamental requirement of any protection scheme on a distribution network. The protection requirements for

sub-transmission and higher voltage system s must also take into account system stability .Where systems are not auto reclosure is commonly used. This in turn dictates the need for high speed protection to reduce overall fault clearance times.

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Underground cables are vulnerable to mechanical damage, such as disturbance by construction work or ground subsidence. Also, faults can be caused by ingress of ground moisture into the cable insulation .or its buried joints. Fast fault clearance is essential to limit extensive damage and avoid the risk of fire, etc.Many power systems use ear thing arrangements designed to limit the passage of earth fault current. Methods such as resistance earthing make the detection of earth faults difficult. Special protection elements are often used to meet such onerous protection requirements.

28. Physical distance must also be taken in to account. over head lines can be hundreds of kilometers in length .If high speed, discriminative protection is to be applied it will be necessary to transfer information between the line ends .this not only puts the event of loss so this signal. Thus, back up protection is an important feature of any protection scheme. In the event of equipment failure, may be of signaling equipment or switch gear, it is necessary to provide alternative forms of fault clearance. It is desirable to provide backup protection which can operate with minimum time delay and yet discriminate with the main protection and protection elsewhere on the system.

CONCLUSION

29. Identifying potentials and anticipating the challenges to our future progress in different sectors of the NTPC VINDHYACHAL constitute a vision of the country’s future. These disparate threads need to be woven together to reflect the integrated nature of our national life. Then, there still remains the question of whether to be preoccupied by the negative possibilities or to throw our full weight behind efforts to fully realize the positive potentials revealed by this analysis. That will determine whether we regard the following statement as a promising glimpse of what India can become in 2020, or as mere fantasy and wishful thinking.

30. The training season was very educational and informative. Being a BHARAT

NAVARATNA, this NTPC have good harmonic relationship and co-ordination between the staff members. As the vocational training seem laborious job to get in touch with the activities. It was nobility of people to provide the information and required theoretical background at their continuous job hour. Most of the equipments were technically strong for huge production. Doing training in NTPC, I hope it would be useful in my future not only in academic but also in professional carrier. Electricity is much more than just another commodity. It is the life-blood of the economy and our quality of life. Failure to meet the expectations of society for

universally available low-cost power is simply not an option. As the world moves into the digital age, our dependency on power quality will grow accordingly. The infrastructure of our power delivery system and the strategies and policies of our insurers must keep pace with escalating demand. Unfortunately, with the regulators

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driving toward retail competition, the utility business priority is competitiveness (and related cost-cutting) and not reliability.

31. There is a natural temptation to attempt to reduce two decades of future progress to a concise formula and prepare a manifesto of policies or strategies that will enable the country to realize its full potential during that period. But a list of such policies or strategies will always remain unsatisfactory unless it is made comprehensive, and a comprehensive list needs to include hundreds of necessary and desirable initiatives. However, in addition to these policy and strategy prescriptions, or rather underlying and supporting them, there are some nodal points of action which, when touched, can release the enormous pent-up energy of the society and throw it into constructive action. It is well that we conclude our summary by identifying those nodal points which will be most powerful for propelling forward the development of NTPC over the next two decades.

32. Thus I learnt many more useful things; it has improved my theoretical concept of electrical power generation, transmission, and distribution. Protection of various apparatus was a great thing. I had a chance to see operation of PLC, SCADA CONTROL, and coal furnace’s internal scene. So the training was more than hope to me and helped me to understand about system more.