BASICS OF ELECTRICAL ENGINEERING GENERATING STATIONS BASICS OF ELECTRICAL ENGINEERING 1

INTRODUCTION Electrical Energy 2 Electrical Energy Considered as the supplier of all other forms of energy Cheaper than other forms Economical to use this for domestic, commercial, industrial and agricultural purposes Easily converted into other forms of energy Hence, bulk electric power is required. 23/10/17

GENERATING STATIONS Employs a Prime-mover coupled to an alternator 3 Employs a Prime-mover coupled to an alternator Prime-mover converts energy from some other form into mechanical energy Alternator converts mechanical energy into electrical energy Electrical energy is transmitted and distributed with the help of conductors to various consumers Classification of generating stations Hydro-electric power station Thermal power station Nuclear power stations Diesel power stations 23/10/17

POWER SCENARIO IN INDIA 4 Total installed capacity 150,000MW Hydropower 50,000 MW Nuclear 10,000MW Thermal (fossil fuels) 80,000MW Other methods 10,000MW 23/10/17

SCHEMATIC ARRANGEMENT 5 23/10/17

SCHEMATIC ARRANGEMENT 6 Artificial storage reservoir formed by constructing a dam across a river and a pressure tunnel is taken off from the reservoir to the valve house at the start of the penstock Valve house contains main sluice valves for cutting off water flow to the power station and isolating valves for cutting off water supply in case of penstock bursts (automatic) Surge tank for better regulation of water pressure in the system (provided just before the valve house) 23/10/17

SCHEMATIC ARRANGEMENT 7 Explanation Reservoir – water – valve house – through – pressure tunnel and from valve house to the water turbine – through pipes of large diameter made of steel or reinforced concrete, called penstock Water turbine – converts – hydraulic energy into mechanical energy Alternator coupled to water turbine – converts – mechanical energy to electrical energy Water – after useful work – discharged to tailrace 23/10/17

ADVANTAGES No fuel is required. Hence operating costs are low 8 No fuel is required. Hence operating costs are low Highly reliable and cheap in operation and maintenance Very neat and clean plant – no smoke or ash is produced Robust and have got longer life Highly skilled engineers are required for construction, but, few experienced persons are required later on Useful for irrigation and flood control 23/10/17

DISADVANTAGES It requires large area 9 It requires large area Construction cost is high, requires long time for erection Long transmission lines are required – since plants are located in hilly areas Uncertainty about availability of water – depends on weather condition 23/10/17

THERMAL STATIONS [STEAM POWER PLANT] 10 Heat of combustion of fuels (Coal, Oil or Gas) is utilized by boilers to raise the steam at high pressure and temperature Steam produced is used in driving the steam turbines coupled to generators and thus in generating electrical energy Steam generated is also used for industrial purposes such as in paper mills, textile mills, sugar mills and refineries, chemical works, breweries, plastic manufacture, food manufacture 23/10/17

SCHEMATIC ARRANGEMENT 11 23/10/17

SCHEMATIC ARRANGEMENT 12 FUEL AND ASH CIRCUIT Fuel from storage is fed to the boiler through fuel feeding device. Ash – due to combustion of coal collects at the back of the boiler and is removed to ash storage through ash handling equipment AIR AND FUEL GAS CIRCUIT Air drawn from atmosphere – forced draught fan through air pre-heater – heated by heat of flue gases passing to chimney – admitted to the furnaces. Flue-gases – passing through the boiler tubes and super heater tubes – drawn by the induced draught fan through dust collector economizer and air pre-heater – finally – exhausted to the atmosphere through chimney 23/10/17

SCHEMATIC ARRANGEMENT 13 FEED WATER AND STEAM CIRCUIT Condensed water – extracted from the condenser by the condenser pump – forced to the I.P. feed water heater, where its temperature is raised by the heat from bled steam. Feed water – now pumped to high pressure water heater – gets heated by the heat from bled steam extracted at suitable point of steam turbine – then pumped into boiler through economizer – further heated by the heat of flue gases. Boiler – water is converted to high pressure wet steam. Wet steam – through super heater – dried and superheated – supplied to the steam turbine through main valve – then – exhausted to the condenser and converted to feed water 23/10/17

SCHEMATIC ARRANGEMENT 14 COOLING WATER CIRCUIT Cooling water – supplied from a natural source of supply – river, canal, sea or cooling towers – circulated through the condenser for condensing the steam and finally discharged to the suitable position near the source of supply Circulation of cooling water – helps – maintaining a low pressure in the condenser 23/10/17

ADVANTAGES Fuel used is cheaper 15 Fuel used is cheaper Less space is required in comparison with that of hydro-electric 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 Can be installed in any place 23/10/17

DISADVANTAGES High maintenance and operating costs 16 High maintenance and operating costs Pollution of atmosphere due to fumes and residues from pulverized fuels Requirement of water in huge quantity Handling of coal and disposal of ash is quite difficult Requires long time for erection and put into action 23/10/17

NUCLEAR POWER PLANTS Peaceful application of atomic energy 17 Peaceful application of atomic energy First atomic power plant – commissioned in U.S.S.R on June 27, 1954 and after that a number of atomic power plants have been commissioned in many countries like U.S.A., Canada, Great Britain, Japan and France First Atomic power plant in India – located in Tarapore Nuclear energy is converted into electrical energy Main atomic fuels – Uranium and Thorium In reactor heat energy released from reactor is utilized in raising steam at high temperature and pressure – which drives the steam turbine and convents steam energy into mechanical energy and then alternator converts it into electrical energy. 23/10/17

SCHEMATIC ARRANGEMENT 18 23/10/17

SCHEMATIC ARRANGEMENT 19 EXPLANATION Nuclear power plant consists of Nuclear reactor – for heat generation Heat exchanger – for converting water into steam Steam turbine Alternator Condenser Reactor and cooling circuit have to heavily shielded to eliminate radiation hazards Heat energy produced – breaking of atoms of Uranium by fission process – atomic reactor – extracted by – pumping fluid or molten metal like liquid sodium or gas through the pile 23/10/17

SCHEMATIC ARRANGEMENT 20 Heated metal/gas – allowed to exchange its heat to the heat exchanger by circulation Steam produced in the heat exchanger is utilized to drive the turbine Turbine – drives the alternator – which converts mechanical energy into electrical energy Output from alternator – delivered to the bus bars through transformer, circuit breakers and isolators 23/10/17

ADVANTAGES 21 The amount of fuel required is quite small, therefore, there is no problem of transportation, storage etc. These plants need less area as compared to any other type These plants can be located near the load centers, therefore, primary distribution cost is reduced These plants are most economical in large quantity There are large deposits of nuclear fuels available all over the world. Such plants can ensure continued supply of electrical energy for thousands of years 23/10/17

DISADVANTAGES 22 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 The fuel used is expensive The disposal of the products (radio-active) – either to be disposed off in a deep trench or in a sea away from sea-shore 23/10/17