Basics of Electrical Engineering 4th Module Generation of Power
- 1. Module 4 Generating stations, transmission and distribution of electric power
- 2. Generating stations • Electric energy is considered superior to all other forms of energy • Cheaper, economical for all purpose of uses • Very convenient form of energy- can be converted into other forms • A generating station generates electricity • A generating station essentialy employs a prime mover coupled to an alternator. • Prime mover converts some form of energy into mechanical energy. • Alernator converts mechanical energy to electrical energy
- 3. • Generating stations are classified as mainly, Hydro-electric power stations Thermal stations Nuclear power stations Diesel power stations
- 4. Hydro-electric power stations • Is a power plant utilizing the potential energy of water at a high level for the electricity generation. • The main requirement is a dam with a high head water content. Schematic arrangement of a hydro –electric plant
- 8. Advantage of Hydro-electric power stations • No fuel is required by such plants as water is the source of energy. Hence operating costs are low. • The plant is highly reliable and it is cheapest in operations and maintenance. • It is very neat and clean plant because no smoke or ash is produced • Such plant are robust and have got longer life. • Highly skilled engineers are required only at the time of construction but later on only a few experienced person will be required. • Such plants in addition to generation of electric power also serve other purpose such as irrigation and flood control.
- 9. Disadvantages • It requires large area • Its construction cost is very high and takes long time for erection. • Long transmission lines are required as the plants are located in hilly areas which are quite away from the load centre. • There is uncertainty about the availability of huge amount of water due to dependence of weather conditions.
- 10. Thermal stations( steam power plants) • The heat of combustion of fuels (coal, oil, or gas ) is utilized by the boilers to raise steam at high pressure and temperature. • Steam produced used in driving the steam turbines coupled to generators. Schematic arrangement the plant can be divided into four main circuits. 1. Fuel and ash circuits 2. Air and fuel gas circuits 3. Feed water and steam circuit 4. Cooling water circuit
- 13. • Fuel and ash circuit o Fuel from the storage fed to boiler through fuel feeding device o Ash produced by combustion collects and removed to ash storage through ash handling equipment. • Air and fuel gas circuit o Forced draught fan draws atmospheric air through air- pre heater o It heated by flue gsses passing to chimney. Then pass to furnaces. o Flue gases after passing boiler and super heater drawn by induced draught fan through economizer and air pre heater finally to chimney.
- 14. • feed water and steam circuit o Condensed water is extracted from the condenser by condensate pump then forced to HP feed water heater where its temperature raised by bled steam. o It is then pumped to boiler through economizer in which it is further heated by flue gasses. o In boiler water is converted into high pressure steam, which is wet o Wet steam is passed through super heater, where it dried then supplied to steam turbine o In condensor heat extracted from steam and converted to feed water • Cooling water circuit o circulate through the condensor to condense the steam and discharges at the source it self.
- 15. Advantages of steam power plant • Fuel used is cheaper • Less space is required in comparison with that of hydroelectric plants • Cheaper in initial cost in comparison with other types of power plants of same capacity • Cheaper in production cost in comparison with that of diesel power plant • Such plants can be installed at any place irrespective of the existence of fuels, while hydro-electric plants can be developed only at the source of water power
- 16. disadvantages • High maintenance and operating costs • Pollution of atmosphere due to fumes and residues from pulverized fuels • Requirement of water in large quantity • Handling of coal and disposal of ash is quite difficult • Requires long time for erection and put into action
- 17. Nuclear power plants • Nuclear energy is converted to electrical energy. • Main fuels are uranium and thorium. • Fuel subjected to nuclear fission releases large amount of energy.
- 21. Advantages of nuclear power plants • The amount of fuel required is very small, therefore , there is no problem of transportation, storage etc. • These plants require less area as compared to any other type • These can be located near the load centers, therefore primary distribution cost is reduced • These plants are most economical in large capacity • There are large deposits of nuclear fuels available all over the world. Therefore such plants can ensure continued supply of electrical energy for thousands of years
- 22. disadvantages • The initial capital cost is very high as compared to other types of power plants • The erection and commissioning of the plant requires greater technical knowledge • The fission by products are generally radio-active and may cause a dangerous amount of radio active pollution • Fuel is expensive • The disposal of products, which are radio-active, is a big problem. They have either to be disposed off in a deep trench or in a sea away from sea-shore
- 23. Non conventional energy sources • The non conventional energy sources are Sun Wind Tidal geothermal
- 24. Solar power generation • Sun is the prime source of energy • The solar electrical energy is of special importance in India that I. There is a need for conservation of fossil fuel resources, such as gas, oil, coal etc II. There is a need for reducing atmospheric and thermal pollution which are having serious detrimental effects on our environment. III. There is a need for supply of electrical energy in remote areas.
- 27. • Advantages 1. Renewable source: no fuel required 2. There is no pollution • Disadvantage 1. Main disadvantage is sun energy available for only part of the day, and cloudy and hazy atmospheric conditions effects most 2. Cost is large 3. Solar tracking system required for sun angle tracking
- 28. Solar photo voltaic systems (SPV)
- 29. • Advantage 1. renewable source 2. No pollution 3. No moving parts, so maintenance cost low 4. Long life • Disadvantages 1. High cost 2. Generation possible for 6 hours during day time only 3. Output is in DC. So DC-AC converter is requires
- 30. Tidal energy • Tides will rise and fall due to change in gravitational force. • The rised tide stored in some area, it may increase upto meters • And this head used to rotate a turbine.
- 31. Wave energy
- 32. Wind energy
- 33. • Advantages 1. Renewable energy source 2. No pollution 3. Installation can made fast 4. Round the clock availability • Disadvantages 1. Weather dependent 2. Most of the time plant may operate at a lower output compared to capacity 3. May create noise pollution 4. May damage in extreme wind speed conditions 5. Large area required
- 34. Geothermal energy • Using heat from interior of the earth energy is converted to electrical energy. • Two main techniques o To use hydrothermal sources o To extract heat from hot dry rocks.
- 35. Transmission & distribution of electric power
- 36. Various systems of power transmission • DC systems i. DC two wire ii. DC two wire with mid point earthed iii. DC three wire system • Single phase AC systems i. Single phase two wire ii. Single phase two wire with mid point earthed iii. Single phase three wire • Two phase AC systems I. Two phase four wire II. Two phase three wire • Three phase AC systems i. Three phase three wire ii. Three phase four wire
- 37. Comparison of dc and ac transmission • DC • Advantages of dc transmission i. Requires two conductor ii. no inductance, capacitance and phase difference iii. No skin effect iv. Free from most of the losses • Disadvantages of dc transmission i. Cannot step up or step down ii. Generation is difficult
- 38. • AC • Advantages of AC transmission i. Possible to generate high voltage ii. Can step up or step down iii. Maintenance of ac substation is easy and cheap • Dis advantages of AC transmission i. Require more conductor than dc ii. L, C affects regulation iii. Due to skin effect effective resistance increases iv. Construction of ac transmission line is more complex
- 39. Advantage of high transmission voltage • Volume of conductor is reduced and hence the cost is less • Voltage drop in the lines is reduced • Efficiency of transmission line is increased
- 41. • Primary transmission Transmission line network connects generating stations with main substations. Main voltage levels are 66, 110, 132, 220, 400kV. • Secondary transmission link between main receiving end substation to secondary substations. voltage levels 66, 33kV • Primary distribution Line supply power from substation to distribution transformer. mainly 11kV. Consumers with load more than 50kW supplies 11 kV • Secondary distribution Three phase 4 wire n/w. low tension low power consumers. Normalyv415/240 V
- 44. • Feeders • Distributors • Service mains
- 45. substation • Classification of substations 1. According to service requirement a) Transformer substations b) Switching sub stations c) Frequency changer sub stations d) Converting substations 2. According to constructional features a) Indoor substations b) Outdoor substations c) Underground substations
- 47. Substation equipments 1. Bus bars 2. Insulators 3. Isolators 4. Circuit breaker 5. Power transformer 6. Current transformer 7. Potential transformer 8. Protective relays 9. Lightning arresters 10.Carrier current equipment
- 48. Advantage of underground system over overhead system of power distribution 1. More safe 2. Low maintenance cost 3. Very few chances of fault 4. Few chances of accident 5. Good appearance 6. Free from lightning effects 7. No interference with communication systems
- 49. Disadvantage of underground system over overhead system of power distribution 1. More expensive 2. Difficult to locate the fault 3. Cannot be worked above 66kV due to insulation difficulties