1. Power System Electric power systems are real-time energy delivery systems. Real time means that power is generated, transported, and supplied the moment you turn on the light switch. The power plants transform other sources of energy in the process of producing electrical energy. For example, heat, mechanical, hydraulic, solar, wind, geothermal, nuclear, and other energy sources are used in the production of electrical energy. 1

2. Power System High-voltage (HV) power lines in the transmission portion of the electric power system efficiently transport electrical energy over long distances to the consumption locations. Finally, substations transform this HV electrical energy into lower-voltage energy that is transmitted over distribution power lines that are more suitable for the distribution of electrical energy to its destination, where it is again transformed for residential, commercial, and industrial consumption. 2

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4. Faraday’s Law an Electricity Generation Faraday`s Law: A voltage is produced on any conductor in a changing magnetic field. If one takes a coil of wire and puts it next to a moving or rotating magnet, a measurable voltage will be produced in that coil. Generators use a spinning magnet (i.e. rotor) next to a coil of wire to produce voltage. This voltage is then distributed throughout the electric power system 4

5. how a generator works? coils of wire mounted on stationary housings, called stators, where voltage is produced due to the magnetic field provided on the spinning rotor. The rotor is sometimes called the field because it is responsible for the magnetic field portion of the generator. The rotor’s strong magnetic field passes the stator windings (coils), thus producing or generating an alternating voltage (ac). The amplitude of the generator’s output voltage can be changed by changing the strength of rotor’s magnetic field. 5

6. how a generator works? 6

7. Three Phase Generator Three coils are placed in the presence of a changing magnetic field, three voltages are produced. When the coils are spaced 120 degrees apart in a 360 degree circle, three-phase ac voltage is produced. Three-phase generation can be viewed as three separate single-phase generators, each of which are displaced by 120 degrees. 7

8. Three Phase Generator 8

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10. Lenz’s Law A current flowing in a wire produces a magnetic field around the wire. This law describes the relationship between the production of magnetic fields and electric current flowing in a wire. Increasing the voltage or the number of turns in the winding increases the strength of magnetic field 10

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13. Three Phase Generator Components 13

14. Rotor Poles Increasing the number of magnetic poles on the rotor enables rotor speeds to be slower and still maintain the same electrical output frequency. Generators that require slower rotor speeds to operate properly use multiple-pole rotors. For example, hydropower plants use generators with multiple-pole rotors because the prime mover (i.e., water) is very dense and harder to control than light-weight steam. 14

15. Rotor Poles 15

16. Generator Connections There are two ways to connect three windings that have a total of six leads (the ends of the winding wires) symmetrically 1)Delta 2)Wye The generator nameplate specifies which winding configuration is used on the stator. 16

17. Generator Connections Delta: Delta configurations have all three windings connected in series. The phase leads are connected to the three common points where windings are joined. 17

18. Generator Connections Delta connected generator 18

19. Generator Connections Wye connected generator 19

20. Types of Generating Stations/Power Plants Depending on the form of energy converted in electrical energy, the generating stations are classified as: 1)Steam power stations 2)Hydroelectric power stations 3)Diesel power stations 4)Nuclear power stations 20

21. Steam Power Station A generating station which converts heat energy of the coal combustion into electrical energy is known as steam power station. - Steam is produced in the boiler by utilizing the heat of coal combustion. - The steam is then expanded into the prime mover(i.e., Steam turbine) and is condensed into condenser to be fed back to the boiler again. - The steam turbine drives the alternator/generator which converts mechanical energy of the turbine into electrical energy. 21

22. Schematic arrangement of Steam Power Plant 22

23. Steam Power Station The arrangement of the steam power station can be divided into six stages: 1)Coal and ash handling arrangement 2)Steam generating plant 3)Steam turbine 4)Alternator/AC Generator 5)Feed water 6)Cooling arrangement 23

24. Stem Power Station Coal and ash handling plant: Coal is crushed into small pieces in order to increase its surface exposure, which helps the rapid combustion of coal without using large quantity of excess air. The pulverized/crushed coal is fed to the boiler by belt conveyers. Coal is burnt in the boiler and the ash produced after the complete combustion of the coal is removed to the ash handling plant and then delivered to the ash storage plant for disposal. The removal of the ash from the boiler furnace is necessary for the proper combustion of the coal. 24

25. Steam Power Station Steam generating plant: It consists of the boiler for the production of steam and other auxiliary equipment for the utilization of flue gases. a) Boiler: The heat of the combustion of coal in the boiler is utilized to convert water into steam at high temperature and pressure. The flue gases from the boiler make their journey through super heater, economiser, air pre-heater and are finally exhausted to atmosphere through the chimney. b) Super heater: The steam produced in the boiler is wet and is passed through a super heater where it is dried and superheated by the flue gases on their way to chimney. c) Economiser: An economiser is a feed water heater (the water being fed to the boiler) which derives heat from the flue gases to increase the feed water temperature. 25

26. Steam Power Station d) Air Preheater: It increases the temperature of the air supplied for coal burning by deriving heat from the flue gases. The advantages of the air preheater are the increased thermal efficiency and the increased steam capacity of the boiler. Steam Turbine: The dry and superheated steam from the super heater is fed to the steam turbine through the main valve. The heat energy of the steam when passing over the blades of the steam turbine is converted into the mechanical energy. After giving heat energy to the turbine, the steam is exhausted to the condenser which condenses the exhausted steam with the help of cold water circulation. 26

27. Steam Power Station Alternator/Generator: The turbine is coupled with the alternator which converts the mechanical energy of the turbine into electrical energy. Feed water: The condensate from the condenser is used as feed water to the boiler. Some water is lost in the cycle which is made up from the external source. The feed water on its way to the boiler is heated by water heater and economizer. This will help in raising the overall efficiency of the plant. Cooling arrangement: Water is drawn from the natural source of supply such as river, canal or lake and is circulated through the condenser. In case the availability of the water from the source of supply is not assured, cooling towers are used. When hot water from the condenser is passed on to the cooling tower it is cooled. 27

28. Steam Power Station Advantages:  The fuel (coal) used is cheap.  Less initial cost as compared to other generating stations.  It requires less space as compared to the hydroelectric power station.  The cost of generation lesser than that of diesel station. Disadvantages:  It pollutes the atmosphere due to the production of large amount of smoke and fumes  The cost of generation is higher than hydroelectric station. 28

29. Efficiency of Steam Power Station 29

30. Efficiency of Steam Power Station 30

31. Hydro-electric Power Station A power station which utilizes which utilizes the potential energy of water at high level for the generation of electrical energy is known as hydroelectric power station. 31

32. Schematic Arrangement of Hydroelectric Power Station 32

33. Hydro-electric Power Station The dam is constructed across a river or lake and water is stored at the back of the dam to form a reservoir. A pressure tunnel is taken off from the reservoir and the water is brought to the valve house at the start of the penstock. The water is taken from the valve house to the turbine through a huge steel pipe known as penstock. The water turbine converts hydraulic energy of water into mechanical energy. The turbine derives the alternator which converts mechanical energy of turbine into electrical energy. 33

34. Hydro-electric Power Station A surge tank (open from the top) is built just before the valve house and protects the penstock from bursting in case the turbine gates are suddenly close due to electrical load being thrown off. The governor opens or close the turbine gates in accordance with the changes in the electrical load. If the electrical load increases the governor opens the turbine gates to allow more water and vice versa. When the turbine gates close, there is a sudden stoppage of water at the lower end of penstock and as a result the penstock may burst. The surge tank absorb this pressure by increase in its water level. 34

35. Constituent of Hydroelectric Power Plant  Hydraulic structure  Water turbines  Electrical equipment 35

36. Hydraulic Structure Hydraulic structure includes dam, spillways, headworks, surge tank and penstock. Dam: A dam is a barrier which stores water and creates water head. Spillways: There are times when the river flow exceeds the capacity of the reservoir. Such a situation arise during heavy rain fall. In order to discharge the surplus water into the river on the down stream side of the dam, spillways are used. Headworks: The headworks consists of diverting structure at the head of an intake. They are used to divert debris and sediments for controlling the flow of water into the turbine. 36

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38. Hydraulic Structure Surge tank: It is a small reservoir or tank (open at the top) in which water level rises or falls to to reduce the pressure swing in the conduit.  When the load on the turbine decreases, the governor closes the gates of the turbine, reducing water supply to the turbine. The excess water at the lower end of the conduit rushes back to the surge tank and increases its water level and the conduit is protected from bursting.  On the other hand, when load on the turbine increases, additional water is drawn from the surge tank to meet the increases load requirement. Hence it overcomes the abnormal pressures in the conduit. 38

39. Hydraulic Structure Penstock: Penstocks are open or closed conduit which carry water to the turbine. They are generally made of reinforced concrete or steel. 39

40. Hydraulic Structure  Automatic butterfly valve shuts off water flow into the penstock if it ruptures.  Air valve maintains the air pressure inside the penstock equals to the out side atmospheric pressure. When the water runs out of penstock faster than it enters, a vacuum is created which may cause the penstock to collapse. Under such situations, air valve opens and admits air in the penstock to maintain the inside air pressure equals the outside air pressure. 40

41. Water Turbine Water turbines are used to convert the energy of falling water into mechanical energy. The principle types of the turbine are: 1)Impulse turbines 2)Reaction turbines 41

42. Electrical Equipment The electrical equipment od hydr0-electric power station includes alternators, transformers, circuit breakers and other switching and protective devices. 42

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44. Diesel Power Station A generating station in which diesel engine is used as prime mover for the generation of electrical energy is known as diesel power station. Advantages: (1) The design and layout of the plan is quite simple. (2) It occupies less space. (3) It can be located at any place. (4) It can be started quickly and can pick up load in a short time (5) There are no standby losses (6) It requires less quantity of water for cooling (7) The overall initial cost is much less than that of steam power station of the same size. (8) The thermal efficiency of the plant is higher than that of steam plant (9) It requires less operating staff. 44

45. Diesel Power Station Disadvantages: (1)The plant has high running cost as the fuel (diesel) used is costly. (2)The plant does not works satisfactory under overload conditions for a longer period. (3)The plant can only generate small power (4)The cost of lubrication is generally high (5)The maintenance charges are generally high 45

46. Schematic Arrangement of Diesel Power Station 46

47. Diesel Power Station Fuel Supply System: It consists of storage tank, strainer, fuel transfer pump and all day fuel tank. The oil is stored in the storage tank. From storage tank, oil is pumped to smaller all day tank at daily or short intervals. From this tank, fuel oil is passed through strainers to remove suspended impurities. The clean oil is injected into the engine by fuel injection pump. Air Intake System: This system supplies necessary air to the engine for fuel combustion. Filters are provided to remove dust particles from air. Exhaust System: This system leads the engine exhaust gas outside the building. A silencer is usually incorporated in the system to reduce the noise level. 47

48. Diesel Power Station Cooling System: The cooling system consists of a water source, pump and cooling towers. The pump circulates water cylinder and head jacket. The water takes away heat from the engine and itself becomes hot. The hot water is cooled by cooling towers and is recirculated for cooling. Lubricating System: This system consists of lubricating oil tank, pump, filter and oil cooler. The lubricating oil is drawn from the lubricating oil tank by the pump and is passed through the filters to remove impurities. The oil coolers keep the temperature of the oil low. 48

49. Diesel Power Station Engine Starting System: This is an arrangement to rotate the engine initially. For large units, compressed air is used for starting. Air at high pressure is admitted to few of the cylinders, making them act as reciprocating air motors to turn over the engine shaft. The fuel is admitted to the remaining cylinders which makes the engine starts under its own power. 49