15-12-2012, 12:02 PM
THE KOTA THERMAL POWER STATION IS LOCATED
Thermal Report.doc (Size: 3.3 MB / Downloads: 26)
INTRODUCTION
For the power generation with 2x110 MW and 3x210 MW of K.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 in -comers, 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 JYOTI MAKE or Air Circuit Breakers.
The 6.6 KV power supply to various draining g 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.
LOCATION
The Kota Thermal Power Station is ideally on the left bank of Chambal River at Up Stream of Kota Barrage . The large expanse of water reached by the barrage provides an efficient direct circulation of cooling system for the power station. The 220 KV GSS is within ½ Kms. from the power station.
LAND
Land measuring approx. 250 hectares was required for the project in 1976, For disposal of ash tank very near to power station is acquired which the ash in slurry form is disposed off through ash and slurry disposal plants.
COAL
Coal India limited owns and operates all the major coal fields in India through its coal producing subsidiary companies viz. Eastern Coal Fields Limited, Western Coal Fields Limited/
Coal India limited is supply coal from its coal mines of coal producing subsidiaries BCCL, SECL & ECL to Kota Thermal Power Station through railway wagons. The average distances of SECL, ECL & BCCL are 800, 950 and 1350 Kms. respectively.
WATER :
The source of water for power station is reservoir formed by Kota Barrage on the Chambal River. In case of large capacity plants huge quantities of coal and water is required. The cost of transporting coal and water is particularly high. Therefore, as far as possible, the plant must be located near the pit rather than at load centre for load above 200 MW and 375 MW . The transportation of electrical energy is more economical as compared to the transportation of coal.
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.
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.
Feed Water and Steam Circuit :
The condensate leaving the condenser is first heated in low pressure (LP) heaters through extracted steam from the lower pressure extraction of the turbine. Then its goes to dearator where extra air and non-condensable gases are removed from the hot water to avoid pitting / oxidation. From deaerator it goes to boiler feed pump which increases the pressure of the water. From the BFP it passes through the high pressure heaters. A small part of water and steam is lost while passing through different components therefore water is added in hot well. This water is called the make up water. Thereafter, feed water enters into the boiler drum through economizer. In boiler tubes water circulates because of density difference in lower and higher temperature section of the boiler. The wet steam passes through superheated. From superheated it goes into the HP turbine after expanding in the HP turbine. The low pressure steam called the cold reheat steam (CRH) goes to the reheater( boiler). From reheater it goes to IP turbine and then to the LP turbine and then exhausted through the condenser into hotwell.
Cooling Water Circuit :
A large quantity of cooling water is required to condense the steam in condenser and marinating low pressure in it. The water is drawn from reservoir and after use it is drained into the river.
ELECTRICITY GENERATOR AT K.T.P.S.
Thermal power station burns the fuel and use the resultant heat to raise the steam which drives the turbo-generator. The fuel may be “Fossil” ( Coal , Oil and Natural Gas) whichever fuel is used the object is same to convert the heat into mechanical energy to electrical energy by rotating a magnet inside the set of winding. In a coal fired thermal power station other raw materials are air and water. The coal is brought to station by train or other means travels from the coal handling system.
i) By conveyer belts to coal bunkers from where it is fed to pulverizing mills.
ii) Mills grind it fine as face powder.
iii) Then this powdered coal mixed with preheated air is blow into boiler by a fan known as primary air fan (PA fan).
iv) When it burns more like a gas as solid in conventional domestic or industrial grate with additional amount of air called secondary air supplied by “Forced Draft Fan”.
SWITCH YARD
220 KV System :
Two 220 KV bus bars have been provided in switch yard and are inter-connected through a bus coupler. Each of the two 110 MW generator is connected to this system through a step up of 125 MVA 240/ 11 KV yard generator transformer. There are two step down transformer each feeding 6.6 KV system ( Station Switchyard ) viz. BS-IS & SB-IB. Each station transformer has two windings one secondary side and is rated for 50/25/25 mva , 270/7/7.2 kva four feeder take off from 220 switch yard, two to SKATPURA ,GSS and other to HEERAPURA , Jaipur GSS. Each of four feeder are provided with bypass isolators which is connected across line breaker and breaker isolator. By closing bus coupler between 220 KV buses and putting line feeders whose breaker required maintenance of any one bus through by pass isolators and all other line feeders whose breaker is by passed is then transformed to bus coupler breaker. A brief description of equipments of 220 KV system is as follows.
CIRCUIT BREAKERS :
Each of generator transformer, station transformer, line feeder and bus coupler is provided with minimum oil circuit breaker of BHEL make. It is rated for 245 KW, 2500 A and 13400 MVA circuit breaker is used to break the circuit either in load condition or in no load condition.
POTENTIAL TRANSFORMER :
each of 220 KV buses is provided with three P.T.’S are core for each phase of BHEL make. There are single phase , oil filled outdoor. N2 sealed , elicitor magnetic type P.T. has two secondary windings on secondary side and selected for 220/53 KV, 10/53 KV.
One secondary winding has O/P of 500 mva accuracy class .5 and is used for metering other secondary winding has O/) of 200 mva accuracy class 3 and used for protection.
LIGHTENING ARRESTOR :
For protection against lightening each of line feeder, generator transformer , station transformer has been provided with three L.A. (one for each phase). All the L.A. are 2 Ø outdoor type and are rated for 198 KV these are manufactured by W.S. insulator. The L.A. of generator transformer and station transformer are located near them.
It has larger value of capacitance and will change upto line voltage. If we have to do some work on line, first earth line through earthing isolator for discharging the line capacitance and then work.