Ind. Training Report- NTPC DADRI

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JUNE - JULY

2010 Industrial Training Report

SUBMITTED BY: ABHINAV SRIVASTAV ELECTRICAL (FINAL YEAR)

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INDUSTRIAL TRAINING ACKOWLEDGEMET REPORT ON ‘ NTPC DADRI’ THERMAL POWER PLANT

National Thermal Power Corporation Limited National Capital Power Station - Dadri P.O. Vidyut Nagar, District Gautam Budh Nagar - 201 008 (UP)

“NTPC was set up in the central sector in the 1975.Only PSU to achieve excellent rating in respect of MOU targets signed with Govt. of India each year. NTPC Dadri station has also bagged ISO 14001 certification. Today NTPC contributes more than 3 / 5th INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV of total power generation in India.” Emailthe Id- [email protected]

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I am highly grateful to the Mr. Sunil Kumar, HOD EE, IEC College of Engineering & Technology Gr. Noida, for providing this opportunity to carry out the four weeks industrial training at NATIONAL THERMAL POWER CORPORATION, DADRI I express my sincere gratitude towards NATIONAL THERMAL POWER CORPORATION, DADRI for giving me an opportunity to undergo my summer training for 4 weeks. I also thanks to all the technicians, staffs for explaining all the practical aspects involved during my training. As I completed my training want to thanks my faculties, Mr. Dinesh Dayal Sir, Mr. Mashood Hasan Sir, who were directly and indirectly involved in imparting me the various practical knowledge of the instruments installed at various locations in industries. Abh inav Srivastav INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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Overview of NTPC

NTPC was set up in the central sector in the 1975 in response to widening demand & supply gap with the main objective of planning, promoting & organizing an integrated development to thermal power in India. Ever since its inception, NTPC has never looked back and the corporation is treading steps of success one after the other. The only PSU to have achieved

INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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excellent rating in respect of MOU targets signed with Govt. of India each year. NTPC is poised to become a 40,000 MW gint corporation by the end of XI plan i.e. 2012 AD. Lighting up one fourth of the nation, NTPC has an installed capacity of 19,291 MW from its commitment to provide quality power; all the operating stations of NTPC located in the National Capital Region & western have acquired ISO 9002 certification. The service groups like Engineering, Contracts, materials and operation Services have also bagged

the

Vindhyachal

ISO and

9001 Korba

certification. station

have

NTPC also

Dadri, bagged

Ramagundam, ISO

14001

certification.Today NTPC contributes more than 3 / 5th of the total power generation in India.

NTPC Limited is the largest thermal power generating company of India. 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. NTPC ranked 317th in the ‘2009, Forbes Global 2000’ ranking of the world’s biggest companies. 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. With a current generating Capacity of 30,644 MW, NTPC has embarked on plans to become a 75,000 MW company by 2017. Apart from power generation from coal and gas, it has also diversified into hydro power, coal mining, power equipment manufacturing, oil and gas exploration, consultancy in the area of power plant constructions and power generation, power trading and distribution in the form of joint ventures with various other entities in India and abroad.

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Fig.1 Major thermal power plants of India

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ROJECT PROFILE OF NTPC Coal based power stations Coal based

State

1

Singraulli

Uttar pradesh

2,000

2

Korba

chattisgarh

2,100

3

Ramagundam

Andhra pradesh

2,600

4

Farakka

West bengal

1,600

5

Vindhyachal

Madhya pradesh

3,260

6

Rihand

Uttar pradesh

2,000

7

Kahalgaon

Bihar

1,840

8

Ntcpp

Uttar pradesh

9

Talcher kaniha

Orissa

3,000

10 Unchahar

Uttar pradesh

1,050

11 Talcher thermal

Orissa

12 Simhadri

Andhra pradesh

13 Tanda

Uttar pradesh

440

14 Badarpur

Delhi

705

15 Sipat

chattisgarh

500

Total(coal)

INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

Commissioned Capacity (MW)

840

460 1,000

23,395

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Gas / liquid fuel based power station -

16 17 18 19 20 21

Gas based

State

Anta Auraiya Kawas Dadri Jhanor-gandhar Rajiv Gandhi ccpp kayamkulam

rajasthan Uttar pradesh Gujarat Uttar pradesh Gujarat Kerala

22 Faridabad Total (gas)

Commissioned Capacity(MW)

haryana

413 652 645 817 648 350 430 3,955

Power plant with joint venturesState

Fuel

Commissioned Capacity(MW)

23 Durgapur

West Bengal

Coal

120

24 Rourkela

Orissa

Coal

120

25 Bhilia

Chhittisgarh

Coal

324

26 rgppl

Maharasta

Naptha /lng

Coal

Total (jv) Grand total

(Coal +gas +jv)

Project under implementationINDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

1480 2044 29,394

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Coal /hydro

State

fuel

Additional cap.under implementation(MW)

1

Kahalgaon

Bihar

Coal

500

2

Sipat

Chattisgarh

Coal

1,980 500

3

Barh

Bihar

Coal

1980

4

Bhilia

Chattisgarh

Coal

500

5

Korba

Chattisgarh

Coal

500

6

Farakka

West Bengal

Coal

500

7

Nctpp

Uttar pradesh

Coal

980

8

Simhadri

Andra Pradesh

Coal

1,000

9

i.g(tneb)

Hrayana

Coal

1,500

10 Vallur

Tamilnadu

Coal

1,000

11 Nabinagar

Bihar

Coal

1,000

12 Bongaigaon

Assam

Coal

750

13 Koldam

Himachal Pradesh

hydro

800

14 Hepp

uttarakhand

hydro

600

15 Hepp

uttarakhand

hydro

520

Total (coal+hydro)

Station At Glance

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14,610

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NTPC dadri is model project of NTPC . also it tit the best project of NTPC also known as NCPS ( National capital power station ). Situated 60 kms away from Delhi in the District of gautam budh Nagar, Uttar Pradesh. The station has an installed capacity of 1669 MW of power – 840 MW from Coal based units and 829 MW Gas Based Station . the station is excelling in performance ever since it’s

commercial operation . consistently

in

receipts of meritorious projectivity awards, the coal based units of the station stood first in the country in terms of PLF

for the financial year

1999 – 2000 by generating an all time national high PLF of 96.12 % with the most

modern

O & M Practices. NTPC – Dadri is committed to

generated clean and green Power. The Station also houses the first HVDC station of the country (GEP project) in association with centre for power efficiency and Environment protection (CENEEP) – NTPC & USAUID. The station has bagged ISO 14001 & ISO 9002 certification during the financial year 1999 – 2000, certified by Agency of International repute M/s DNV Netherlands M/s DNV Germany respectively

DADRI THERMAL POWER STATION The National Capital Power Station [NCPS] has the distinction of being the country's only three in one project ; consisting of Stage-I 840 MW; Stage-II 490MW ( and 490 MW under construction) of coal based units , 829 MW gas based modules , and a 1,500 MW H.V.D.C. converter station {under the operational control of P.G.C.I.L. since October '93}. The stage-II (490MW*2) coal based units are scheduled in 2010 to meet the common wealth games power requirement. The commercial operation of Stage-II Unit-V 490 MW has been declared w.e.f 31.01.2010. Also work for Stage-II UNIT-VI 490MW is under full swings. Besides the station has the largest switchyard in the country with a power handling capacity of 4,500 MW INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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The station has the unique distinction of having Asia's first 100 percent dry ash extraction with transit ash storage silos and final storage place converted to an green ash mound . An Ash Technology park has also been set up to demonstrate the uses of ash which has become the point of attraction for the visitors.

Plant sizeStage -1 Unit 1

210mw

Unit 2

210mw

Unit 3

210mw

Unit4

210mw

Stage-2 Unit 5

490mw

Unit 6 (under construction)

490mw

LOCATIONThe station's capacity allocation is mainly concentrated in northern region of India . Spread over 2,465 acres , the station is situated on the Dadri -Dhaulana road [10 kms. off Dadri G.T. road , and 12 kms. off the National Highway # 24] . The route from New Delhi to NCPS is 60 kms. long and is about 25 kms. from Ghaziabad

NTPC DADRI INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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National Capital Power Station - Coal

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The coal-based station mainly meets power requirements of the National Capital Region [NCR] , and the northern grid . With the World Bank funding component , the capital cost of the units is Rs. 16.69 billion . There are four 210 MW coal based units. The units have a coal-fired boiler and a steam turbine each . The boiler design is also suitable for 100% operations with heavy furnace oil firing . For this , three storage tanks , each of capacity 15,000 kL , enough for 10 days continuous oil firing requirements have been provided for the boilers . Coal Source: The coal is transported from the Piparwar block of mines of the North Karanpura Coalfields of Bihar , over a distance of about 1,200 kms. , by the Indian Railways bottom discharge , and Box 'N' type of wagons . The coal requirements for the four units is 15,000 M.T. each day , 3.67 million tonnes annually . The station has its' own 14 kms. Long rail track from the Dadri Railway Station , to the site , and a 6 km in-plant track , on electric traction.

National Capital Power Station - Gas INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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The gas-based station at N.C.P.S. is the country's largest . It has two modules; each module consists of two gas turbines of 130.19 MW each with one waste heat recovery boiler and one steam turbine of 154.51 MW capacity . The power from this plant is allocated to Uttar Pradesh , and also to Delhi , Punjab , Jammu and Kashmir , Haryana , Himachal Pradesh and Rajasthan . The cost of gas based modules is Rs. 9.75 billion , which includes a German K.f. W. funding . The modules are fully commissioned . Gas turbines generate power at an efficiency of about 32% only , and to utilize the rest of this energy , a combined cycle system is adopted . The waste heat from the gas turbine exhaust is routed through the waste heat recovery boiler , and the steam thus generated is utilized in a conventional steam turbine to generate additional power . By this , the overall efficiency of fuel heat utilization reaches to about 48% .

Gas Source: The source of fuel for this plant is the reserves of South Bassein fields in South Tapi and mid Tapi delta in the Arabian Sea . The natural gas from South Bassein off shore fields is transported through a submarine pipeline to Hazira onshore terminal and then through the 1,700 kms. Long HaziraBijapur pipeline via Shahjanpur and Babrala , to the project . For the 829 MW project , the requirement is 3.00 million cubic meters per day (yearly average). It would be worthwhile to note that within a short span of less than 7 years , both the coal and gas based power cycle units/modules have been commissioned in a project . Both the projects have diverse modern technologies , with the latest process controls .

HVDC

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This is a technological accomplishment in power by NTPC . Commissioned in December '90 , the system is the first commercial long distance HVDC link in India , and also the largest in Asia . The basic objective of the HVDC link is to transmit the power generated at the RhSTPP efficiently to the northern region , with significant reduction in transmission losses . It consists of two converter stations - one located at Rihand (RhSTPP) acting as a rectifier , and the other at Vidyutnagar (NCPP) as an inverter , involving a distance of about 900 kms. . These stations are connected by a +/- 500 kV HVDC line for transmission of 1,500 MW power from Rihand to Vidyutnagar .

DETAILS OF 220KV AND 400KV FEEDERS SOURCES INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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Sl.No.

Line Name

Capacity

1.

Generator - 1

210 MW

Remarks

Thermal Plant 2.

Generator - 2

210 MW

3.

Generator - 3

210 MW

4.

Generator - 4

210 MW

5.

Generator - 1

131 MW Gas Plant

6.

Generator - 2

131 MW

7.

Generator - 3

131 MW

8.

Generator - 4

131 MW

9.

Generator – 5 (Steam)

146.5 MW

10.

Generator – 6 (Steam)

146.5 MW

11.

HVDC Feeder

1500 MW

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HVDC

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TRANSMISSION LINES Sl.No.

Line Name

Capacity

States

1.

Panipat - 1

500MW

Haryana

2.

Panipat - 2

600MW

3.

Murad Nagar

500MW

Utter Pradesh

4.

Maler Kotla

500MW

Puniab

5.

Mandola - 1

750MW

Delhi

6.

Mandola - 2

750MW

7.

Greator Noida

750MW

Utter Pradesh Delhi

8.

Maharani Bagh

750MW

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THERMAL POWER PLANT 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 station1. Cooling water pump 2. Three phase transmission line 3. Step up transformer 4. Electrical generator 5. Low pressure steam 6. Boiler feed water pump 7. Surface condenser 8. Intermediate pressure steam turbine 9. Steam control valve 10. High pressure steam turbine 11. Deaerator feed water heater 12. Coal conveyer 13. Coal hopper 14. Coal pulverizer 15. Boiler steam drum 16. Boiler ash hopper 17. Super heater 18. Force draught (draft) fan 19. Reheater 20. Combustion air intake 21. Economiser 22. Airpreheater 23. Precipitator 24. Induced draught(draft) fan 25. Fuel gas stack

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The description of some of the components above is as follows:

1.Cooling towersCooling 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 lineThree 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 INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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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 generatorAn 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 PumpA Boiler Feed Pump is a specific type of pump used to pump water into steam boiler. These pumps are normally high pressure units that use suction from a condensate return system and can be of INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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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.

5.Control valvesControl 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.DeaeratorA Deaerator is a device for air removal and used to remove dissolved gases from boiler feed water to make it non-corrosive.

7.Feed Water HeaterA 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 INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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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.PulverizerA pulverizer is a device for grinding coal for combustion in a furnace in a fossil fuel power plant.

9.Super HeaterA 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; nonsuperheated 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.

10.EconomizersEconomizer, 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 INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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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.

10.Air PreheaterAir 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.

11.PrecipitatorAn 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 INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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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.

13.Fuel gas stackA 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 INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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levels required by governmental environmental policies and regulations.

COAL HANDLING PLANT(CHP) This departments training starts on June 16,2010 under Sir A. K.Chakrabrati(DGM- EM). The fuel used in the Dadri thermal power station is coal. Therefore it is necessary to handle this fuel carefully and deliver it safely to the site of power plant. A railway siding line is taken into the power station and coal is delivered in the storage yard.

Major Components: 1. Wagon Tippler Wagons from the coal yard come to the tippler and are emptied here. The process is performed by a slip –ring motor of rating: 55 KW, 415V, 1480 RPM. This motor turns the wagon by 135 degrees and coal falls directly on the conveyor through vibrators. Tippler has raised lower system which enables is to switch off motor when required till is wagon back to its original position. It is titled by weight balancing principle. The motor lowers the hanging balancing weights, which in turn tilts the conveyor. Estimate of the weight of the conveyor is made through hydraulic weighing machine

2. Conveyor Conveyors are made of rubber and more with a speed of 250-300m/min. Motors employed for conveyors has a capacity of 150 HP. Conveyors have a capacity of carrying coal at the rate of 400 tons per hour. Few conveyors are double belt, this is done for imp. Conveyors so that if a belt develops any problem the process is not stalled. The conveyor belt has a switch after every 25-30 m on both sides so stop the belt in case of emergency. The conveyors are 1m wide, 3 cm thick and made of chemically treated vulcanized rubber. The INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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max angular elevation of conveyor is designed such as never to exceed half of the angle of response and comes out to be around 20 degrees. Crust coal from raw coal bunker to mill. The quantity of raw coal fed in mill can be controlled by speed control of aviator drive controlling damper and aviator change. 3. Bowl Mill: - The ball mill crushes the raw coal to a certain height and then allows Zero Speed Switch:-It is safety device for motors, i.e., if belt is not moving and the motor is on the motor may burn. So to protect this switch checks the speed of the belt and switches off the motor when speed is zero. 3. Metal Separators As the belt takes coal to the crusher, No metal pieces should go along with coal. To achieve this objective, we use metal separators. When coal is dropped to the crusher hoots, the separator drops metal pieces ahead of coal. It has a magnet and a belt and the belt is moving, the pieces are thrown away. The capacity of this device is around 50 kg. The CHP is supposed to transfer 600 tons of coal/hr, but practically only 300-400 tons coal is transfer 4. Crusher Both the plants use TATA crushers powered by BHEL. Motors. The crusher is of ring type and motor ratings are 400 HP, 606 KV. Crusher is designed to crush the pieces to 20 mm size i.e. practically considered as the optimum size of transfer via conveyor

1.2 MILLING SYSTEM : 1.2.1 RC Bunker: Raw coal is fed directly to these bunkers. These are 3 in no. per boiler. 4 & ½ tons of coal are fed in 1 hr. the depth of bunkers is 10m. 1.2.2 RC Feeder: It transports pre it to fall down. Due to impact of ball on coal and attraction as per the particles move over each other as well as over the Armor lines, the coal gets crushed. Large particles are broken by impact and full grinding is done by attraction. The Drying and grinding option takes place simultaneously inside the mill. 1.2.3 Classifier:INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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It is an equipment which serves separation of fine pulverized coal particles medium from coarse medium. The pulverized coal along with the carrying medium strikes the impact plate through the lower part. Large particles are then transferred to the ball mill. 1.2.4. Cyclone Separators: It separates the pulverized coal from carrying medium. The mixture of pulverized coal vapour caters the cyclone separators. 1.2.5. Mills Fans: It is of 3 types: Six in all and are running condition all the time. (a) ID Fans: - Located between electrostatic precipitator and chimney. Type-radical Speed-1490 rpm Rating-300 KW Voltage-6.6 KV Lubrication-by oil (b) FD Fans: - Designed to handle secondary air for boiler. 2 in number and provide ignition of coal. Type-axial Speed-990 rpm Rating-440 KW Voltage-6.6 KV (c)Primary Air Fans: - Designed for handling the atmospheric air up to 50 degrees Celsius, 2 in number And they transfer the powered coal to burners to firing. Type-Double suction radial Rating-300 KW Voltage-6.6 KV Lubrication-by oil Type of operation-continuous 1.2.8 Bowl Mill: One of the most advanced designs of coal pulverizes presently manufactured. Motor specification –squirrel cage induction motor Rating-340 KW Voltage-6600KV Current-41.7A Speed-980 rpm Frequency-50 Hz No-load current-15-16 A a) Wagon Tippler:INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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Motor Specification (i) H.P 75 HP (ii) Voltage 415, 3 phase (iii) Speed 1480 rpm (iv) Frequency 50 Hz (v) Current rating 102 A b) Coal feed to plant:Feeder motor specification (i) Horse power 15 HP (ii) Voltage 415V,3 phase (iii) Speed 1480 rpm (iv) Frequency 50 H

4. LT MOTORS :This departments training is dne under guidance of Sir K P Singh. The low tension motors are different from the HT motors in terms of operating voltage. They generally operate at 415V, the most popular type of motor used for above applications is the DOL started squirrel cage induction motor.

4.1. Insulation: Since the operating voltage for LT motors is less than that of HT motors hence insulation of class B is used in case of LT motors. Normally paper insulation and insulation tape is employed for insulation purposes.

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Fig 4.1 LT INDUCTION MOTOR

4.2 Heat treatment: The stator after being wounded is given heat treatment. It kept in an electrical furnance for about hours. The metal stator expands and heating effect absorbs all the moisture content in the stator. The stator is then immersed in a varnish solution so as to fill all the gaps with this insulating material. The varnish used is Elfmothran 1450. 4.3 Ac contactor: AC contactor are 3 pole suitable for DOL starting of motors and protecting the connected motors. The contactor of the following motors are equipped with INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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special arrangements to provide immediate reclosing of the contactor when voltage fails and reappears with 1.5 - 3 sec. 4.4 Fuse switches: Upto 25 A are rotary switches with fuses; for 63A and 100A are quick make, quick break ,double break switch fuses and for 250A,400A and 630A are fuse switches

5. HT MOTORS

HT AC motors are normally designed for operation on 3 phase,AC supply with normal frequency of 50Hz. Standard nominal voltage for which motors are designed are: VOLTAGE

CAPACITY

3.3 kV

160-200 kW

6.6 kV

160-800 kW

11 kV

1000 kW and above

5.1 Insulating Materials :1. Sunmica 2. Effolux: it is an oil and waterproof materials. 3. Nylon Chord: It is used to cover the stator coil to provide necessary insulation. 4. Silver bridging: it employs the soldering of joint of the series coil. Silver is used instead of solder material due to its high melting point. 5. Piping ship: It is made of fiberglass. It is used to fill gap between the stator coils to prevent vibrations and prevents the cutting of slot base. It also helps in even cooling of the stator. INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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6. Epoxy red gel coat: It is an insulation varnish used with thinner of no. 221 for dilution and hardener of no. 758. 7. Bectal Grey/red: It is general type insulation varnish of B class used with thinner no. 205. 5.2 HT AC MOTOR FOR THERMAL POWER APPLICATION:5.2.1 Boiler auxiliary :a) ID (induced draft) fan b) FD (forced draft) fan c) GR fan d) PA (primary air) e) Mills 5.2.2 Cooling water system :a) CW pumps (circulating water) 5.2.3 Turbine auxiliaries :-

b) Boiler feed pump c) Condensate extraction pump d) Starting oil pump 5.2.4 Ash handling system :a) Pumps 5.2.5 Coal handling plant :a) Crushers b) Conveyors

5.3 SPECIFIC PERFORMANCE REQUIREMENTS OF MOTORS ARE :INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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• • • • • • • • •

High ambient temperature 50oC. Voltage and frequency variation should be ± 10% High starting/pull out torque Low starting current Voltage dip conditions/minimum permissible voltage at start Bus transfer condition Suitability to stand transients Long bearing life Low noise level Low vibration level

The most popular type of motor above applications is the DOL started squirrel cage induction motors.

Fig.5.1 HT-MOTOR ROTOR

Fig.5.2 HT-MOTOR STATOR

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CIRCUIT BREAKER- Types of breakers operational at NTPC Dadri Switchyard (1) 400kV Air blast circuit breaker (2) 220kV SF6 filled circuit breaker. SPECIFICATION OF AIR BLAST CIRCUIT BREAKER Type

DLYF420 nc4

Normal Voltage

420KV

Normal Current

2000A

Trip coil voltage

220V dc

Close coil voltage

220V dc

Frequency

50HZ

Short time Current

40KA 3Sec.

Breaking Current

Sym. 40KA Asym. 48 KA

R I L at 50HZ Voltage switching impulse

630KV 1050

Operating pressure

27-31 Kg

Mass

3850 Kg

Make

Hindustan Brown Boveri

SPECIFICATION OF SF6 GAS CIRCUIT BREAKER INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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SR. NO

CIRCUIT BREAKER

1.

CIRCUIT BREAKER TYPE

ELF SL 4-1

2.

SR. NUMBER

20000070

3.

Month and year of Mfg.

JANUARY - 2001

4.

Voltage

245 KV

5.

Normal current

1600/2500 AMP.

6.

Lightning impulse with stand voltage

1050 KV

7.

Switching impulse with stand voltage

- KV

8.

Short circuit breaking current

40 KA

9.

Short time with stand current & duration

40 LA

10.

Line charging breaking current

125 AMP.

11.

Operating sequence

0-0 3S - CO – 3Min- CO

12.

First - pole - to - clear factor

1.3

13.

Gas pressure SF6 at 200C (abs)

7.0 bar

14.

Closing & opening device supply voltage

220 V DC

15.

Auxiliary circuit supply voltage

240 V AC

16.

Air pressure

20.5 bar

17.

Frequency

50 Hz

18.

Mass (approx) for 3 poles

4000 kg

GENERATORS

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1 Sec.

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Generator Fundamentals: The transformation of mechanical energy into electrical energy is carried out by the Generator.

Working Principle:The A.C. Generator or alternator is based upon the principle of electromagnetic induction and consists generally of a stationary part called stator and a rotating part called rotor. The stator housed the armature windings. The rotor houses the field windings. D.C. voltage is applied to the field windings through slip rings. When the rotor is rotated, the lines of magnetic flux (viz magnetic field) cut through the stator windings. This induces an electromagnetic force (e.m.f.) in the stator windings. The magnitude of this e.m.f. is given by the following expression. E = 4.44ØFN volts Ø = Strength of magnetic field in Weber’s. F = Frequency in cycles per second or Hertz. N = Number of turns in a coil of stator winding F = Frequency = Pn/120 Where P = Number of poles,n = revolutions per second of rotor. From the expression it is clear that for the same frequency, number of poles increases with decrease in speed and vice versa. Therefore, low speed hydro turbine drives generators have 14 to 20 poles where as high speed steam turbine driven generators have generally 2 poles. Pole rotors are used in low speed generators, because the cost advantage as well as easier construction. Development The first A.C. Generator concept was enunciated by Michael Faraday in 1831. In 1889 Sir Charles A. Parsons developed the first AC turbogenerator. Although slow speed AC generators have been built for some time, INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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it was not long before that the high-speed generators made its impact. Development contained until, in 1922, the increased use of solid forgings and improved techniques permitted an increase in generator rating to 20MW at 300rpm. Up to the out break of second world war, in 1939, most large generator;- were of the order of 30 to 50 MW at 3000 rpm. During the war, the development and installation of power plants was delayed and in order to catch up with the delay in plant installation, a large number of 30 MW and 60 MW at 3000 rpm units were constructed during the years immediately following the war. The changes in design in this period were relatively small. In any development programme the Costs of material and labour involved in manufacturing and erection must be a basic consideration. Coupled very closely with these considerations is the restriction is size and weight imposed by transport limitations.

Generator component:This deals with the two main components of the Generator viz. Rotor (winding & balancing) and Stator (its frame, core & windings).

Fig. GENERATOR’S ROTOR

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The electrical rotor is the most difficult part of the generator to design. It revolves in most modern generators at a speed of 3,000 revolutions per minute. The problem of guaranteeing the dynamic strength and operating stability of such a rotor is complicated by the fact that a massive non-uniform shaft subjected to a multiplicity of differential stresses must operate in oil lubricated sleeve bearings supported by a structure mounted on foundations all of which possess complex dynamic be behavior peculiar to themselves. It is also an electromagnet and to give it the necessary magnetic strength the windings must carry a fairly high current. The passage of the current through the windings generates heat but the temperature must not be allowed to become so high, otherwise difficulties will be experienced with insulation. To keep the temperature down, the cross section of the conductor could not be increased but this would introduce another problems. In order to make room for the large conductors, body and this would cause mechanical weakness. The problem is really to get the maximum amount of copper into the windings without reducing the mechanical strength. With good design and great care in construction this can be achieved. The rotor is a cast steel ingot, and it is further forged and machined. Very often a hole is bored through the centre of the rotor axially from one end of the other for inspection. Slots are then machined for windings and ventilation.

Rotor winding:- Silver bearing copper is used for the winding with mica as the insulation between conductors. A mechanically strong insulator such as micanite is used for lining the slots. Later designs of windings for large rotor incorporate combination of hollow conductors with slots or holes arranged to provide for circulation of the cooling gas through the actual conductors. When rotating at high speed. Centrifugal force tries to lift the windings out of the slots and they are contained by wedges. The end rings are secured to a turned recess in the rotor body, by shrinking or screwing and supported at the other end by fittings carried by the rotor body. The two ends of windings are connected to slip rings, usually made of forged steel, and mounted on insulated sleeves. When completed the rotor must be tested for mechanical INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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balance, which means that a check is made to see if it will run up to normal speed without vibration. To do this it would have to be uniform about its central axis and it is most unlikely that this will be so to the degree necessary for perfect balance. Arrangements are therefore made in aldesigns to fix adjustable balance weights around the circumference at each end.

Stator :Stator frame:The stator is the heaviest load to be transported. The major part of this load is the stator core. This comprises an inner frame and outer frame. The outer frame is a rigid fabricated structure of welded steel plates, within this shell is a fixed cage of girder built circular and axial ribs. The ribs divide the yoke in the compartments through which hydrogen flows into radial ducts in the stator core and circulate through the gas coolers housed in the frame. The inner cage is usually fixed in to the yoke by an arrangement of springs to dampen the double frequency vibrations inherent in 2 pole generators. The end shields of hydrogen cooled generators must be strong enough to carry shaft seals. In large generators the frame is constructed as two separate parts. The fabricated inner cage is inserted in the outer frame after the stator core has been constructed and the winding completed. Stator core: The stator core is built up from a large number of 'punching" or sections of thin steel plates. The use of cold rolled grain-oriented steel can contribute to reduction in the weight of stator core for two main reasons: a) There is an increase in core stacking factor with improvement in lamination cold Rolling and in cold buildings techniques. b) The advantage can be taken of the high magnetic permeance of grainoriented steels of work the stator core at comparatively high magnetic saturation without fear or excessive iron loss of two heavy a demand for excitation INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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ampere from the generator rotor.

turns

Stator Windings :Each stator conductor must be capable of carrying the rated current without overheating. The insulation must be sufficient to prevent leakage currents flowing between the phases to earth. Windings for the stator are made up from copper strips wound with insulated tape which is impregnated with varnish, dried under vacuum and hot pressed to form a solid insulation bar. These bars are then place in the stator slots and held in with wedges to form the complete winding which is connected together at each end of the core forming the end turns. These end turns are rigidly braced and packed with blocks of insulation material to withstand the heavy forces which might result from a short circuit or other fault conditions. The generator terminals are usually arranged below the stator. On recent generators (210 MW) the windings are made up from copper tubes instead of strips through which water is circulated for cooling purposes. The water is fed to the windings through plastic tubes.

Generator Cooling System:The 200/210 MW Generator is provided with an efficient cooling system to avoid excessive heating and consequent wear and tear of its main components during operation. This Chapter deals with the rotor-hydrogen cooling system and stator water cooling system along with the shaft sealing and bearing cooling systems. Rotor Cooling System The rotor is cooled by means of gap pick-up cooling, wherein the hydrogen gas in the air gap is sucked through the scoops on the rotor wedges and is directed to flow along the ventilating canals milled on the sides of the rotor coil, to the bottom of the slot where it takes a turn and comes out on the similar canal milled on the other side of the rotor coil to the hot zone of the rotor. Due to the rotation of the rotor, a positive INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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suction as well as discharge is created due to which a certain quantity of gas flows and cools the rotor. This method of cooling gives uniform distribution of temperature. Also, this method has an inherent advantage of eliminating the deformation of copper due to varying temperatures.

Hydrogen Cooling System:Hydrogen is used as a cooling medium in large capacity generator in view of its high heat carrying capacity and low density. But in view of its forming an explosive mixture with oxygen, proper arrangement for filling, purging and maintaining its purity inside the generator have to be made. Also, in order to prevent escape of hydrogen from the generator casing, shaft sealing system is used to provide oil sealing. The hydrogen cooling system mainly comprises of a gas control stand, a drier, an liquid level indicator, hydrogen control panel, gas purity measuring and indicating instruments. The system is capable of performing the following functions : 1) Filling in and purying of hydrogen safely without bringing in contact with air. Maintaining the gas pressure inside the machine at the desired value at all the times. 2)

Provide indication to the operator about the condition of the gas inside the machine i.e. its pressure, temperature and purity.

3)

Continuous circulation of gas inside the machine through a drier in order to remove any water vapour that may be present in it. Indication of liquid level in the generator and alarm in case of high level.

Stator Cooling System :- The stator winding is cooled by distillate. Which is fed from one end of the machine by Teflon tube and flows through the upper bar and returns back through the lower bar of another slot? Turbo generators require water cooling arrangement over and above the usual hydrogen cooling arrangement. The stator winding is cooled in this system by INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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circulating demineralised water (DM water) through hollow conductors. The cooling water used for cooling stator winding calls for the use of very high quality of cooling water. For this purpose DM water of proper specific resistance is selected. Generator is to be loaded within a very short period if the specific resistance of the cooling DM water goes beyond certain preset values. The system is designed to maintain a constant rate of cooling water flow to the stator winding at a nominal inlet water temperature of 40 degC.

Rating of 210 MW Generator:Manufacture by Bharat heavy electrical Limited (BHEL) Capacity - 247000 KVA Voltage (stator) - 15750 V Current (stator) - 9050 A Voltage (rotor) - 310 V Current (rotor) - 2600 V Speed - 3000 rpm Power factor - 0.85 Frequency - 50 Hz Hydrogen - 3.5 Kg/cm2 Stator wdg connection - 3 phase star connection Insulation class - B

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TRANFORMERS A transformer is a device that transfers electrical energy from one circuit to another by magnetic coupling with out requiring relative motion between its parts. It usually comprises two or more coupled windings, and in most cases, a core to concentrate magnetic flux. An alternating voltage applied to one winding creates a time-varying magnetic flux in the core, which includes a voltage in the other windings. Varying the relative number of turns between primary and secondary windings determines the ratio of the input and output voltages, thus transforming the voltage by stepping it up or down between circuits. By transforming electrical power to a high-voltage,_low-current form and back again, the transformer greatly reduces energy losses and so enables the economic transmission of power over long distances. It has thus shape the electricity supply industry, permitting generation to be located remotely from point of demand.

Fig. Power Transformer. INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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Basic principles:The principles of the transformer are illustrated by consideration of a hypothetical ideal transformer consisting of two windings of zero resistance around a core of negligible reluctance. A voltage applied to the primary winding causes a current, which develops a magneto motive force (MMF) in the core. The current required to create the MMF is termed the magnetizing current; in the ideal transformer it is considered to be negligible, although its presence is still required to drive flux around the magnetic circuit of the core. An electromotive force (MMF) is induced across each winding, an effect known as mutual inductance. In accordance with faraday’s law of induction, the EMFs are proportional to the rate of change of flux. The primary EMF, acting as it does in opposition to the primary voltage, is sometimes termed the back EMF”. Energy losses An ideal transformer would have no energy losses and would have no energy losses, and would therefore be 100% efficient. Despite the transformer being amongst the most efficient of electrical machines with ex the most efficient of electrical machines with experimental models using superconducting windings achieving efficiency of 99.85%, energy is dissipated in the windings, core, and surrounding structures. Larger transformers are generally more efficient, and those rated for electricity distribution usually perform better than 95%. A small transformer such as plug-in “power brick” used for low-power consumer electronics may be less than 85% efficient.

Losses:Transformer losses are attributable to several causes and may be differentiated between those originated in the windings, some times termed copper loss, and those arising from the magnetic circuit, sometimes termed iron loss. The losses vary with load current, and may furthermore be expressed as “no load” or “full load” loss, or at an intermediate loading. Winding resistance dominates load losses contribute to over 99% of the noload loss can be significant, meaning that even an idle transformer constitutes a drain on an electrical supply, and lending impetus to development of lowloss transformers. Losses in the transformer arise from: Winding resistance INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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Current flowing trough the windings causes resistive heating of the conductors. At higher frequencies, skin effect and proximity effect create additional winding resistance and losses. Hysteresis losses Each time the magnetic field is reversed, a small amount of energy is lost due to hysteresis within the core. For a given core material, the loss is proportional to the frequency, and is a function of the peak flux density to which it is subjected. Eddy current Ferromagnetic materials are also good conductors, and a solid core made from such a material also constitutes a single short-circuited turn trough out its entire length. Eddy currents therefore circulate with in a core in a plane normal to the flux, and are responsible for resistive heating of the core material. The eddy current loss is a complex function of the square of supply frequency and inverse square of the material thickness. Magnetostriction Magnetic flux in a ferromagnetic material, such as the core, causes it to physically expand and contract slightly with each cycle of the magnetic field, an effect known as magnetostriction. This produces the buzzing sound commonly associated with transformers, and in turn causes losses due to frictional heating in susceptible cores. Mechanical losses In addition to magnetostriction, the alternating magnetic field causes fluctuating electromagnetic field between primary and secondary windings. These incite vibration with in near by metal work, adding to the buzzing noise, and consuming a small amount of power. Stray losses Leakage inductance is by itself loss less, since energy supplied to its magnetic fields is returned to the supply with the next half-cycle. However, any leakage flux that intercepts nearby conductive material such as the transformers support structure will give rise to eddy currents and be converted to heat. Cooling system Large power transformers may be equipped with cooling fans, oil pumps or water-cooler heat exchangers design to remove heat. Power used to operate the cooling system is typically considered part of the losses of the transformer

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INTERCONNECTING TRANSFORMER (ICT) Power transformers are the backbone of the large grid. The power is generated at the low voltage level and has to be carried to far away load centers. Typically the power is generated at the Pit heads i.e power source like coal, water. It is uneconomical carry the bulk power at low voltage levels. Depending upon the requirement the voltage level is stepped upto the transmission level i.e 220 or 400kV. At higher voltages the transmission losses are less. Similarly at the remote end the voltage is stepped down the distribution level. To accomplish the task Power transformers are installed and act as bi-directional element in the system. At NTPC Dadri this task is carried out by bank of Single Phase 400/220kV Interconnecting

transformers.

Autotransformers

are

used

when

transformation ratio is between 1 and 2 and above 315MVA, due to size and weight constraints all the transformers are single phases. Three such single phase transformers are installed three phases to make One bank of transformer. Three banks of transformers are installed to evacuate power from the 220kV switchyard generated by 4X 210MW thermal Units. All these transformers are star- star connected transformers with neutral solidly grounded. A third winding called tertiary winding at much lower voltage i.e 33kV, is also provide and is connected in delta to facilitate the flow of third harmonic current to reduce the distortion in the output voltage.

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To reduce the overall size of the transformer, the transformer is provided with Oil forced and Air forced type cooling at its 100% rating. However, to save the energy, the cooling system is controlled by the temperature of the winding. The transformers are also equipped with On Load Tap Changer to meet the change in voltage variation. Typically the Tap changer provides variation between ± 10% of the nominal voltage i.e. 400kV with a variation of 0.5% at each tap. SPECIFICATIONS Make

CROMPTON GREAVES Ltd.

No.

3

Rating

167*3 = 500 MVA

Tap

17

No load Voltage KV (HV side)

400/√3

No load Voltage KV (IV side)

220/√3

No load Voltage KV (LV side)

33 KV

Line current Amp. (HV side)

289.25 , 433.88 , 723.13

Line current Amp. (IV side)

525.91, 788.87, 1314.78

Line current Amp. (LV side)

1688.48

Connection symbol

YNaOd11 for 3 phase bank

Type of cooling

ONAN / ONAF / OFAF

Frequency

50 Hz

Insulation level (HV)

1450kV

Insulation level (IV)

630kV

Insulation level (LV)

250kV

Temperature rise oil deg. c

350 above ambient

PROTECTION RELAYS

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Relay is a device that detects the fault mostly in the high voltage circuits and initiates the operation of the circuit breaker to isolate the defective section from the rest of the circuit. Whenever fault occurs on the power system, the relay detects that fault and closes the trip coil circuit. This results in the opening of the circuit breaker, which disconnects the faulty circuit. Thus the relay ensures the safety of the circuit equipment from damage, which the fault may cause. PURPOSE OF PROTECTIVE RELAYING The capital investment involved in a power system for the generation, transmission and distribution of electrical power is so great that the proper precautions must be taken to ensure that the equipment not only operates as nearly as possible to peak efficiency, but also that it is protected from accidents. The normal path of the electric current is from the power source through

copper

conductors

in

the

generators,

transformers

and

transmission lines to the load and it is confined to this path by insulation. The insulation however may be broken down, either by the effect of temperature and age or by a physical accident, so that the current then follows an abnormal path generally known as a short circuit or fault. Whenever this occur the destructive capabilities of the enormous energy in the power system may cause expensive damage to the equipment, severe drop in the voltage and loss of revenue due to interruption of service. Such faults may be made in frequent by good design of the power apparatus and lines and the provision of protective devices, such as surge diverters and ground fault neutralizers, but a certain number will occur inevitably due to lightening and unforeseen accidental conditions. INDUSTRIAL TRAINING REPORT BY ABHINAV SRIVASTAV Email Id- [email protected]

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The purpose of protective relays and relaying systems is to operate correct circuit breaker so as to disconnect only the faulty equipment from the system as quickly as possible, thus minimizing the trouble and damage caused by faults when they do occurs. With all other equipment it is only possible to mitigate the effects of short circuit by disconnecting the equipment as quickly as possible, so that the destructive effects of the energy into the fault may be minimized. UNDER VOLTAGE RELAY Under voltage protection is provide for AC circuits, busbar, transformer, motor, rectifier etc. Such protection is given by means of under voltage relay. The relay coil is energized by voltage to be measured either directly or via a voltage transformer. OVER CURRENT RELAY If a short circuit occurs the circuit impedance is reduced to a low value and therefore a fault is accompanied by a large current, Over current protection is that protection in which the relay pickup when the magnitude of current exceeds the pickup level. The basic element in over current protection is an over current relay. The over current relays are connected to the system normally by means of CTs.

EARTH FAULT RELAY

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Earth fault protection responds to single line to ground fault and double line to ground faults. The current coil of the earth fault relay is connected either in neutral to ground relay CT circuit. Core balance Cts are used for earth fault protection.

DIFFERENTIAL RELAY Differential protection responds to vector difference between two or more similar quantities. In circulating current differential protections CTs are connected on either side of the protected equipments. During the internal faults the difference of secondary current flow through the relay coil. Differential protection is used for protection of large transformer, generator, motors feeders and busbars

.

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DADRI SWITCHYARD:

Figure No. (5) flow

Single line diagram for power

Fig: single line diagram for power flow

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BUS BAR SCHEME FOR 220KV SWITCHYARD

Transfer Bus

Main Bus#1

Main Bus#2

Feeder

Bus Coupler

Transfer Bus Coupler

Figure: Double Main and transfer bus arrangement

BUS BAR SCHEME FOR 400KV SWITCHYARD

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ICT Feeder

Bus#1 Bus#2

Feeder#1

Feeder#2

Figure : 400kV switchyard single line diagram

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USES OF COAL ASH: DADRI ash have been successfully used in the following applications . • • • • • •

LAND FILLS ROAD EMBANKMENTS ROAD CONSTRUCTION PORTLAND POZZOLONA CEMENT BUILDING PRODUCTS CONCRETE

Use of Dadri ash in above applications have resulted in saving in terms of money , conservation of natural resources viz mother earth, lime stone, coal, sand, energy, land and water apart from reduction in CO2 emission and thus environment.

PRESENT SENARIO IN INDIA : • • • • • •

65% of the total installed power generation is coal based. 230 - 250 million MT coal is being used every year. High ash contents vrying from 30 to 50%. 95 million MT ash generated every year. Ash generation likely to reach 170 million MT by 2010. Presently 65000 Acres of Land occupied by Ash Ponds.

The NCPS Dadri project has the unique distinction of having Asia's first 100 percent dry ash extraction with transit ash storage silos and final storage place converted to an green ash mound.

Ash can be collected in following categories: -

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•

•

DRY FLY ASH:Dry ash is collected from different rows of electrostatic precipitators. It is available in two different grades of fineness in silos for use as resource material by different users BOTTOM ASH:Bottom ash collected from bottom of boiler and transported to hydro bins and then ash mound for use in Road Embankment. CONDITIONED FLY ASH: Conditioned fly ash is also available in Ash mound for use in Land fills and Ash Building prod

NTPC - A trend setter in the country has set up 100 % dry ash extraction cum disposal in the form os Ash Mound at NTPC Dadri . Ash mound has come out as the most viable alternative for ash disposal in an economic friendly way by minimum use of land and water.

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ADVANTAGES OF ASH MOUND : • • • • • • •

Less requirement of land only 1/3rd land requirement as compared to wet disposal system. 375 acres of land is required as compared to 1000 acres for installed capacity of 840 MW at Dadri. Only 1/50th water required in comparison to wet system Eliminates leaching effect. Separate storage of fly ash (PFA) and furnace bottom ash(FBA). Facilitates large scale utilization at later stage. The green ash mound can be used as a useful piece of land.

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FEATURES OF ASH MOUND • • • • • • • •

Ash mound covers area of 375 acres. Ultimate height 55 meters. Side slope 1:4 with haulage road at 15 m interval. Top most flat area 140 acres. Capacity of ash storage 53 million cum. Sufficient for running 840 MW for 40 years. Side slopes covered with green grass and plantations of trees . Beautiful green spot in the vicinity of power house.

AUTOMATION 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.

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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 coalfired 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.

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

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 

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CONCLUSION As I have been undergoing training , I was able to know the practical application of theory what I used to study from books. With trainings help understood that studies helps us to know things but practical helps to apply theories for betterment of Humankind . I would like to give special thanks to the NTPC DADRI staff for their cordial support for making the training a success.

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ABHINAV SRIVASTAV ELECTRICAL ENG. (4th YEAR)

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