A thermal power station uses energy conversion in 3 sequential steps. At first, the chemical energy of a combustible is converted into heat. Secondly, the heat is converted into mechanical energy that is finally converted into electricity. The heat is generated during burning processes in a boiler, burning chamber or fuell cell, the mechanical energy is convereted from heat during gas expansion in some type of rotating machine, which finally operates an electrical generator to produce the electricity. The rotating machine can be a steam turbine, a gas turbine or a piston engine.
A combustible (coal) is burned with air supply in a boiler, the chemical energy of the combustible is converted into a heat and transferred into a working media (water). Preasurized feedwater is warmed at constant pressure upto boiling temperature, converted into to a saturated steam and superheated. Flue gas and solid noncombustible wastes are generated. Flue gas is drained away via flueduct through separators into a chimney, while ashmatter is deposited onto dumping ground.
Principal Of Operation Of Steam Turbine:-
Working of the steam turbine depends wholly upon the dynamic action of Steam. The steam is caused to fall in pressure in a passage of nozzle: doe to this fall in pressure a certain amount of heat energy is converted into mechanical kinetic energy and the steam is set moving with a greater velocity. The rapidly moving particles of steam, enter the moving part of the turbine and here suffer a change in direction of motion which gives rose to change of momentum and therefore to a force. This constitutes the driving force of the machine. The processor of expansion and direction changing may occur once or a number of times in succession and may be carried out with difference of detail. The passage of steam through moving part of the commonly called the blade, may take place in such a manner that the pressure at the outlet side of the blade is equal to that at the inlet inside. Such a turbine is broadly termed as impulse turbine. On the other hand the pressure of the steam at outlet from the moving blade may be less than that at the inlet side of the blades; the drop in pressure suffered by the steam during its flow through the moving causes a further generation of kinetic energy within the blades and adds to the propelling force which is applied to the turbine rotor. Such a turbine is broadly termed as impulse reaction turbine .
TURBO GENERATOR manufactured by B.H.E.L. and incorporated with most modern design concepts and constructional features, which ensures reliability, with constructional & operational economy.
The generator stator is a tight construction, supporting & enclosing the stator windings, core and hydrogen coolers. Cooling medium hydrogen is contained within frame & circulated by fans mounted at either ends of rotor. The generator is driven by directly coupled steam turbine at a speed of 3000 r.p.m. the Generator is designed for continuous operation at the rated output. Temperature detectors and other devices installed or connected within then machine, permit the windings, teeth core & hydrogen temperature, pressure & purity in machine under the conditions. The source of excitation of rotor windings is thyristor controlled D.C. supply. The auxiliary equipment’s supplied with the machine suppresses and enables the control of hydrogen pressure and purity, shaft sealing lubricating oils. There is a provision for cooling water in order to maintain a constant temperature of coolant (hydrogen) which controls the temperature of windings.