INSTRUMENTATION SCHEME OF THERMAL POWER PLANTBY:ANKUR MAHAJAN( 112505)
CONTENTS INTRODUCTION OF POWER PLANT OBJECTIVE OF INSTRUMENTATION & CONTROL CLASSIFICATION OF POWER PLANTS THERMAL POWER PLANT SUB CYCLES OF THERMAL POWER PLANT QUANTITIES TO BE MEASURED MEASUREMENT POINT & VARIABLES MEASUREMENT PROCESS REFERENCES
INTRODUCTION Power plant is assembly of systems or sub-systems to generate electricity. Power plant must be useful economically & environmental friendly to the society. Design of power plant incorporate two important aspects:(1)Selection of power generating equipments should be such so that maximum of return will result from minimum expenditure over the working life of the plant.(2)Operation should be such so as to provide cheap, reliable & continuous service.
INTRODUCTION This entire task is often taken up by control & instrumentation or simply instrumentation system which has following functions:a) Measurementb) Controlc) Operationd) Monitoringe) Protection
INTRODUCTION For a plant Measurement system needs to be: Very accurate Reliable Delays should be as small as possible Should be switched on manually when a overall control system fails
OBJECTIVE OF INSTRUMENTATION & CONTROL Efficient Operation of the plant Economic Operation of the plant Safe operation of the plant Pollution control GURUNANAK THERMAL POWER PLANT, BATHINDA(PUNJAB)
THERMAL POWER PLANT A Generating station which convert heat energy into electrical energy The Steam Power Plant, Diesel Power Plant, Gas Turbine Power Plant& Nuclear Power Plant are called THERMAL POWER PLANT. Works on RANKINE Cycle.
SUB CYCLES OF THERMAL POWER PLANT WATER CYCLE -------- CONDENSATION, FEEDPUMP, ECONOMIZER COMBUSTION CYCLE ---------- ECONOMIZER, BOILER, SUPER HEATER STEAM CYCLE ------------------ BOILER, SUPER HEATER, TURBINE
QUANTITIES TO BE MEASURED Pressure Temperature Flow Level Expansion/ Contraction Analysis of (1) Water (2) Steam (3) Flue Gases And Others
MEASUREMENT POINTS & VARIABLESVariables/ Measuring Points Types Of Sensors/ Approx. numberParameters Instruments in the plant(1) Pressure (a) Boiler Bourdon Tube, (b) Turbine Diaphragm, (c) Turbine Throttle Bellows 375-400 (d) Furnace Bell Gauges(2) Tempera (a Steam at superheater Thermocouple ture inlet & outlet (b Feed Water at economiser inlet (c Water at condenser RTD 700-750 inlet (d Air Preheater (e Flue Gases Thermocouple
(e Bearing of turbine & Thermocouple generator (f feed pump, condensate RTD pump(3) Flow (a High Pressure Steam Orifice, Venturi, 75-100 (b Feed water inlet Flow Nozzle,etc. (c Condensate(4) Level (a Boiler Drum (b condensate tank Differential 75-100 (c Water line pressure methods(5) Expansion (a Turbine Shaft Relative 6-8 (b Turbine casing Displacement(6) Vibration (a turbine & generator Mass spring with shafts & bearing shells potentiometric Capacitive, eddy 30-50 current, piezo electric & optical types are used
(7) Analysis(i) WATER (a feed water at econ- -omiser inlet (b Boiler inlet Conductive cell 8-12 (c Condenser with meter (d Condensate pump discharge(ii) STEAM (a Saturated steam Conductive cell 4-6 (b Main line steam with meter (c Super heater inlet Na Analyser 1-2(iii) FLUE GASES (a O2 – economiser to air Zirconia cell 2-4 heater (b CO2 – Air heater inlet CO2 analyser 2-4 & outlet (c CO – stack CO analyser 2-4 (d SO2 - Stack SO2 analyser 1-2 (e Nitrogen Oxide- stack N- Oxide Analysesr 1-2 (f Dust concn.- stack Optical method 2-3
MEASUREMENT OF PRESSURE Varies from vacuum as in furnace to 200 Mpa at the main steamline. Pressure measuring devices are divided into two groups: (1) Liquid Columns (2) Expansion Elements Liquid columns: Manometric type instruments Low range pressure measurement P =0 h Patm WELL TYPE MANOMETER
MEASUREMENT OF PRESSURE These are not favoured in modern power plant but are still used in older power plants. Expansion elements: Used in modern power plants Usually metallic & its movement indicates the pressure Either directly coupled with mechanical linkages or indirectly by an electrical transducer connected to a read out device
MEASUREMENT OF PRESSURE Expansion elements Diaphragms Bellows Bourdon tube Diaphragms: Commonly corrugated diaphragms are used because large deflection can be produced without nonlinearity compared with flat type. In order to increase the deflection capabilities two or more corrugated diaphragms are welded at the circumferences--- Capsule element.
MEASUREMENT OF PRESSURE Bellows Manufactured from Brass, Brass alloys, Stainless steel. Used for low pressure measurement. For high pressure measurement bellows are connected with spring.
MEASUREMENT OF PRESSURE Bourdon Tube C shaped & made into an arc of 0 about 270 Material from which it made depends upon the pressure range of the device Bourdon tubes are also used in forms other than C type Spiral element: large movement than C tube. Helical element: produce more or less circular movement which is useful for driving a recorder pen directly.
MEASUREMENT OF TEMPERATURE Since power generation is a Thermodynamic process so up to date knowledge of temperature of the plant is most important. The efficiency of generation also depend on the temperature measurement T2 1 T1T2 = Temp. inside the condenserT1= Superheater temperature Temp. can be measured only by using indirect methods.
MEASUREMENT OF TEMPERATURE THERMOELECTRIC THERMOMETRY The actual value depend upon the material used & on temperature difference between the junctions.
MEASUREMENT OF TEMPERATURETYPE METAL A METAL B TEMPERAT POINT TO URE KNOW RANGE 0 RESISTANT TO T COPPER COPPER- 400 C CORROSION IN NICKEL MOST (CONSTANTAN) ATMOSPHERE 0 NOT COMMONLY J IRON COPPER- 850 C USED BECAUSE NICKEL OF RUSTING & (CONSTANTAN) EMBRITTLEMENT 0 SUITABLE FOR E NICKEL- COPPER- 700 C OXIDISING & CHROMIUM( NICKEL INERT CHROME) (CONSTANTAN) ATMOSPHERE 0 MOST K NICKEL- NICKEL- 1100 C COMMONLY CHROMIUM( ALUMINIUM USED CHROME) (ALUMEL)
MEASUREMENT OF TEMPERATURETYPE METAL A METAL B TEMPERAT POINT TO URE KNOW RANGE 0 R PLATINUM1 PLATINUM 1400 C SUITABLE FOR OXIDISING & 3%RHODIUM INERT ATMOSPHERE 0 S PLATINUM1 PLATINUM 1400 C SUITABLE FOR OXIDISING & 0%RHODIUM INERT ATMOSPHERE, CAN BE USED IN VACUUM FOR SHORT PERIOD THERMISTOR ARE NOT USED IN THERMAL POWER PLANTS 0 0 BECAUSE ITS RANGE IS -60 TO 15
MEASUREMENT OF TEMPERATURE RESISTANCE THERMOMETRY Suggested by Siemens in 1871- but not satisfactory used for high temperature Today RTD is given by H.L.Calender in 1891 PROPERTY-The resistance of the conductor changes when its temperature is changed. Copper is occasionally used Platinum, nickel or nickel alloys are commonly used Tungsten is used for high temperature applications
MEASUREMENT OF TEMPERATUREMETAL MIN. TEMP. MAX.TEMP. MELTING POINT 0 0 0PLATINUM -260 C 110 C 1773 C 0 0 0COPPER 0C 180 C 1083 C 0 0 0NICKEL -220 C 300 C 1435 C 0 0 0TUNGSTEN -200 C 1000 C 3370 C
MEASUREMENT OF FLOW A universal flow meter for all applications in power station is not available. Infact there are more ways of measuring flow than measuring pressure & temperature. Dual function meters usually measure flow rate with linear output & minimum error. Vortex & Ultrasonic meters have become available in recent years (1986) & their full potential is not still fully developed.
ANALYSIS pH, DO,TURBIDITY & HYDRAZINE: Need to be checked for acidity (pH), Dissolved oxygen(DO) Turbidity arising out of contamination by suspended particles . Hydrazine which is added from outside to the feed water but the excess should be monitored. Oxygen reacts with thallium to form thallium oxide which in aqueous solution show good conductivity.
ANALYSIS Turbidity is measured at the outlet of the condenser. Hydrazine is added to decrease dissolved oxygen Hydrazine nitrogen + water Its also makes water alkaline & prevent acidic corrosion. Its is also toxic so its overuse can effect the aquatic life.
REFERENCES British Electricity International,Modern Power station practice, control & instrumentation, vol F. A.K. Sawhney, “A course in Electrical & Electronic measurements & instrumentation”, Danpat Rai & CO.,seventeenth edition. D Patranabis, “Principles of Industrial Instrumentation”,TMH, second edition. Frederick T. Morse, “ Power Plant Engineering”. “Power Plant Engineering”, http://en.wikipedia.org/wiki/power plant engineering A.K. Raja, “Power plant Engineering”,New Age International Publishers.
REFERENCES Educational Technology Service Centre- IIT KHARAGPUR; S. BANERJEE; EE Deptt., Energy resource & technology. V.K. Mehta, “Principles Of Power System”, S Chand.