For the power generation with 2x110 MW, 3x210 MW and 2X195 MW of K.S.T.P.S. authorities are required to be operative to active full operation. The auxiliaries are basically operation either on L.T. System i.e. 415 V 3-Ø power supply is made available to the system after providing the station transformer of 3x50 MVA capacity with voltage 220 KV/ 7.2/7.2 KV & different service transformers of capacity 1.0 MVA, 1.5 MVA, 2.0 MVA, which are located near the load centre as the transformer having the voltage of 6.6 KV /415 V. The 6.6 KV power is distributed through 6.6 KV interconnected Bus System for all the five units with a control through DC of 220 V. The 415 V power supply is done through a L.T. SWGR (Switchgear) which are located nearby the distribution transformer as well as the load centers. The all incomers, which are breaker controlled , are having the control the L.T. SWGR are having the control system on 110/ 220 V AC. The 6.6 KV power supply which are either MOCB (Minimum Oil Circuit Breaker) of or Air Circuit Breakers.
The 6.6 KV power supply to various draining equipment’s i.e. more is made through breakers which are either MOCB of Jyoti make air circuit breaker which are either of voltage makers as well as SF 6 of NGEF make. The LT supply is also controlled through air break circuit breaker which are either L&T make or English Electric Company of
India. The various H.T. motors are switched on
started through on direct ON line (DOL) in order to inverse the availability of
equipment at full efficiency without time gap.
GENERAL LAYOUT & BASIC IDEA
A control system of station basically works on Rankin Cycle. Steam is produced in Boiler is exported in prime mover and is condensed in condenser to be fed into the boiler again. In practice of good number of modifications are affected so as to have heat economy and to increase the thermal efficiency of plant\
The Kota Thermal Power Station is divided into four main circuits :
The Kota Thermal Power Station is divided into four main circuits :
Ø Fuel and Ash Circuit
Ø Air and Gas Circuit
Ø Feed water and Steam Circuit
Ø Cooling Water Circuit
2.1 FUEL & ASH CIRCUIT:-
Fuel from the storage is fed to the boiler through fuel handling device. The fuel used in KSTPS is coal, which on combustion in the boiler produced the ash. The quantity of ash produced is approximately 35-40% of coal used. This ash is collected at the back of the boiler and removed to ash storage tank through ash disposal equipment.
2.2 AIR AND GAS CIRCUIT:-
Air from the atmosphere is supplied to the combustion chamber of Boiler through the action of forced draft fan and induced draft fan. The flue gas gases are first pass around the boiler tubes and super heated tubes in the furnace, next through dust collector (ESP) & then economizer. Finally, they are exhausted to the atmosphere through fans.
COAL HANDLING PLANT
It can be called the heart of thermal power plant because it provided the fuel for combustion in boiler. The coal is brought to the KSTPS through rails there are fourteen tracks in all for transportation of coal through rails. The main coal sources for KSTPS are SECL (South Eastern Coalfields Limited), NCL (Northern Coalfield Limited). Everyday 6 to 7 trains of coal are unloaded at KSTPS. Each train consists of 58 wagons and each wagon consists of 50 tones of coal. The approximate per day consumption at KSTPS is about 18000 metric tones. It costs approximate 4.5 crores of rupees per day including transportation expenses. The coal is firstly unloaded from wagon by wagon triplers then crushed by crushers and magnetic pulley and pulverized to be transformed to the boiler. The whole transportation of coal is through conveyor belt operated by 3-Ø Induction motor.
Main parts of granulator like break plates, cages crushing rings and other internal parts are made of tough manganese (Mn) steel. The rotor consists of four rows of crushing rings each set having 20 Nos. of toothed rings and 18 Nos. of plain rings. In CHP Stage 1 & 2 having 64 Nos. of ring hammers. These rows are hung on a pair of suspension shaft mounted on rotor discs. Crushers of this type employ the centrifugal force of swinging rings stroking the coal to produce the crushing action. The coal is admitted at the top and the rings stroke the coal downward. The coal discharges through grating at the bottom.
The coal handling plant can broadly be divided into three sections:-
1) Wagon Unloading System.
2) Crushing System.
3) Conveying System.
A boiler (or steam generator) is a closed vessel in which water, under pressure is converted into steam. It is one of the major components of a thermal power plant. A boiler is always designed to absorb maximum amount of heat released in process of combustion. This is transferred to the boiler by all the three modes of heat transfer i.e. conduction, convection and radiation.
3.1 BOILERS ARE CLASSIFIED AS:-
3.1.1Firetubeboiler:- In this type the products of combustion pass through the tubes which are surrounded by water. These are economical for low pressure only.
3.1.2 Water tube boiler:-
In this type of boiler water flows inside the tubes and hot gases flow outside the tubes. These tubes are interconnected to common water channels and to steam outlet.
Ø The water tube boilers have many advantages over the fire tube boilers
Ø High evaporation capacity due to availability of large heating surface.
Ø Better heat transfer to the mass of water.
Ø Better efficiency of plant owing to rapid and uniform circulation of water in tubes.
Ø Better overall control.
Ø Easy removal of scale from inside the tubes.
In KSTPS, Natural circulation, tangentially fired, over hanged type, Water tube boilers are used. Oil burners are provided between coal burners for initial start up and flame stabilization. Firstly, light oil (diesel oil) is sprayed for initialization then heavy oil (high speed diesel oil) is used for stabilization of flame. Pulverized coal is directly fed from the coal mills to the burners at the four corners of the furnace through coal pipes with the help of heated air coming from PA fan. Four nos. of ball mills of 34MT/hr. capacity each have been installed for each boiler. The pressure inside boiler is -ive so as to minimized the pollution and looses & to prevent the accidents outside the boiler.
For ensuring safe operation of boilers, furnace safe guard supervisory system (FSSS) of combustion engineering USA designed has been installed. This equipment systematically feed fuel to furnace as per load requirement. The UV flame scanners installed in each of the four corners of the furnace, scan the flame conditions and in case of unsafe working conditions trip the boiler and consequently the turbine. Turbine - boiler interlocks safe guarding the boiler against possibility furnace explosion owing to flame failure.
CHAPTER – 4
Turbine is a machine in which a shaft is rotated steadily by impact or reaction of current or stream of working substance (steam, air, water, gases etc) upon blades of a wheel. It converts the potential or kinetic energy of the working substance into mechanical power by virtue of dynamic action of working substance. When the working substance is steam it is called the steam turbine.
4.1 PRINCIPAL OF OPERATION OF STEAM TURBINE:-
Ø 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
CHAPTER – 5
The electric power Generators requires direct current excited magnets for its field system. The excitation system must be reliable, stable in operation and must response quickly to excitation current requirements. When excitation system response is controlled by fast acting regulators, it is chiefly dependent on exciter. Exciter supply is given from transformer and then rectified.
5.1 STATIC EXCITATION SYSTEM:-
In KSTPS static excitation system is provided it mainly consists of the following:-
Ø Rectifier transformer
Ø Nos. of thyristor converters
Ø An automatic voltage regulator (AVR)
Ø Field suppression equipment
Ø Field flashing equipment
Ø Field Protection
Ø Pole Slipping
Ø Plane Overload Protection
Ø Inter-turn Fault
Ø Negative Phase Sequence Protection
Ø Reverse Power Protection
Ø Forward Power Protection
Ø Under Frequency & Over Frequency Protection
Ø Generator Voltage Protection
Ø Rotor Earth Fault Protection
7.1 GENERAL PROTECTION:
It is most important electrical equipment of many generating station. Tripping of even a generating unit may cause overloading of associated machines and even to system un-stability. The basis function of protection applied to generator is to reduce voltage to minimum by rapid discrimination clearance of faults. Unlike other apparatus the opening of C.B. to isolate faulty generator is not sufficient to prevent future damage.