Presentation on theme: "Theme: Power plant C&I (IPC) systems & Tending to Zero Forced Outage"— Presentation transcript:
1 Theme: Power plant C&I (IPC) systems & Tending to Zero Forced Outage byInternalization of Best Practices
2 Presentation Outline: 1.Some definitions & basics of Pressure, Flow & Temp. measurement2. Categorization of C&I systems based on location of application3. Division of power plant C&I systems based on functionality & type of application4.Evolution of C&I systems and latest trend in technology5.NTPC at a glance and maintenance practices of C&I systems6. Some case studies
4 Measurement: Pressure TerminologyAccuracy : Closeness with which an instrument reading approaches the true value of the variable being measured.Precision : A measure of reproducibility of the measurements; i.e. given a fixed value of a variable, precision is a measure of the degree which successive measurements differ from one another.Sensitivity : The ratio of output signal or response of the instrument to a change of input or measured variable.Resolution : The smallest change in measured value to which the instrument will respond.Error : Deviation from the true value of the measured variable.
5 Measurement: Pressure Repeatability refers to the ability of a pressure sensor to provide the same output with successive applications of the same pressure.Hysteresis is a sensor's ability to give the same output at a given pressure while increasing and decreasing the pressure.
6 Measurement: Pressure Pressure : DefinitionsDefinition: Force per unit areaAbsolute pressureAtmospheric pressureDifferential pressureGauge pressureImportance : Pressure measurement is critical for safe and optimum operation of processes such as steam generation, hydraulic equipment operation, air compression, vacuum processing etc.
7 Measurement: Pressure Zero Reference , Gauge, Absolute, Atmospheric PressureAny pressure above atmosphere is called gauge pressureAny pressure below atmosphere is a vacuum (negative gauge pressure)Absolute pressure (psia) is measured from a perfect vacuumDifferential Pressure has no reference to either absolute vacuum or atmospheric pressure
8 Measurement: Pressure UnitsThe SI unit for pressure is the Pascal (Pa);1Pa= 1 N·m-2Non-SI unit pound (Lb) per square inch (psi) and bar are commonly usedPressure is sometimes expressed in grams-force/cm2or as kgf/cm2 (KSC)1 atm=1.03 ksc= psi=760mmHg=10000 mmWC= PaStandard pressure:Pressure of normal (standard) atmosphere is defined as standard pressure
9 Measurement: Pressure Pressure Measuring devicesManometersusing water ,mercury and other liquids of known densityFor measuring low pressures.Mechanical/Elastic Pressure SensorsElectrical Pressure TransducersFor measuring pressure of all ranges for telemetering purposes.Manometer:A simple pressure standardMay be used for gauge, differential, and absolute measurements with a suitable reference.Useful mainly for lower pressure work because the height of the column of mercury will otherwise become very high.The difference in column heights gives the pressure reading
11 Measurement: Pressure Electrical Pressure SensorsPotentiometer SensorInductiveCapacitivePiezoelectricStrain GaugeUsually generate output signals in the mV range (spans of 100 mV to 250 mV).In transmitters, these are amplified to the voltage level (1to 5 V) and converted to current loops, usually mA dc
12 Measurement: Pressure Pressure SwitchesApplicationsAlarm (Status)Shutdown (Hi/Lo Limits)Control (ON/OFF)A “switch” is an instrument that automatically senses some process variable (such as pressure) and provides an on/off signal relative to some reference point.SensingElementConditioningCircuitBourdon TubeBellowsDiaphragmStrain GaugeMechanical SwitchTransistorSet Point
13 Measurement: Pressure High Pressure In High Temperature* When high process temperatures are present, various methods of isolating the pressure instrument from the process are used.* These include siphons, chemical seals with capillary tubing for remote mounting, and purging.Snubbers & its useChemical SealSiphon
14 Measurement: Pressure Pressure SnubbersTo filter out pressure spikes, or to average out pressure pulses, snubbers are installed between the process and the instrumentInstrument indicates avg pr.Snubber Before use After usewhen one is interested in the measurement of fast, transient pressures (such as to initiate safety interlocks on rising pressures), snubbers must not be used, as they delay the response of the safety system.
15 Measurement: Pressure Chemical Seal or diaphragm ProtectorChemical seals are used when media can falsify the pressure measurements due to high temperature, high viscosity or their property to crystallise
16 Measurement: Pressure SiphonA siphon is a coiled tube. This coil provides a large cooling surface and the trap created prevents the condensate from draining away.A siphon is required for hot condensing. fluids, such as steam, to assure a liquid trap.It is used to prevent live steam from entering and damaging the device.It is used to protect the instrument from hydraulic or thermal shocks.The two most common forms of siphon tube are the 'U' and Pigtail types.
17 by the Bernoulli equation. Measurement: FlowTypes of flow meters:Orifice Flow meterVortex flow meterUltrasonics flow meterCoriolis Mass Flow meterMajor issues for selecting flow metersOrifice Flow-metersSeveral sensors rely on the pressure drop or head occurring as a fluid flows by aresistance. The relationship between flowrate and pressure difference is determinedby the Bernoulli equation.
18 Measurement: Flow Orifice Flow-meters An orifice plate is a restriction with an opening smaller than the pipe diameter which is inserted in the pipe; the typical orifice plate has a concentric, sharp edged opening.Because of the smaller area the fluid velocity increases, causing a corresponding decrease in pressure.The flow rate can be calculated from the measured pressure drop across the orifice plate, P1-P3. The orifice plate is the most commonly used flow sensor, but it creates a rather large non-recoverable pressure due to the turbulence around the plate, leading to high energy consumption.
19 Measurement: Flow Venturi Tube The change in cross-sectional area in the venturi tube causes a pressure change between the convergent section and the throat, and the flow rate can be determined from this pressure drop. Although more expensive that an orifice plate; the venturi tube introduces substantially lower non-recoverable pressure drops
20 Measurement: Flow Pitot Tubes Pitot tubes were invented by Henri Pitot in 1732 to measure the flowing velocity of fluids. Basically a differential pressure (dp) flow meter, a pitot tube measures two pressures: the static and the total impact pressure.Pitot tubes are used to measure air flow in pipes, ducts, stacks, and liquid flow in pipes, open channels.While accuracy and rangeability are relatively low, pitot tubes are simple, reliable, inexpensive, and suited for a variety of environmental conditions, including extremely high temperatures and a wide range of pressures.
21 Measurement: Flow Pitot Tubes A single-port pitot tube can measure the flow velocity at only a single point in the cross-section of a flowing stream.The probe must be inserted to a point in the flowing stream where the flow velocity is the average of the velocities across the cross-section, and its impact port must face directly into the fluid flow.
22 Measurement: Flow Pitot Tubes The point velocity of approach (VP) can be calculated by taking the square root of the difference between the total impact pressure (PT) and the static pressure (P) and multiplying that by the C/D ratio, where C is a dimensional constant and D is density:The pitot tube measures the static and dynamic (or impact) pressures of the fluid at one point in the pipe. The flow rate can be determined from the difference between the static and dynamic pressures which is the velocity head of the fluid flow.
23 Measurement: Flow Vortex Flow-meters This measuring principle is based on the fact that vortices are formed downstream of an obstacle in a fluid flow, e.g. behind a bridge pillar.This phenomenon is commonly known as the Kármán vortex street.
24 Measurement: Flow Vortex Flow-meters This is detected by a sensor, such as capacitive sensor and fed to the electronic processor as a primary, digitized, linear signal.Capacitive sensors with integrated temperature measurement can directly register the mass flow of saturated steam as well.Universally suitable for measuring liquids, gases and steamLargely unaffected by changes in pressure, temperature and viscosityHigh long-term stability (lifetime K factor), no zero-point driftNo moving partsMarginal pressure loss
25 Ultrasonic flow-meters Measurement: FlowUltrasonic flow-metersSwimming against the flow requires more power and more time than swimming with the flow. Ultrasonic flow measurement is based on this elementary transit time difference effect.Two sensors mounted on the pipe simultaneously send and receive ultrasonic pulses.At zero flow, both sensors receive the transmitted ultrasonic wave at the same time, i.e. without transit time delay.When the fluid is in motion, the waves of ultrasonic sound do not reach the two sensors at the same time.
26 Ultrasonic flow-meters Measurement: FlowUltrasonic flow-metersThis measured "transit time difference" is directly proportional to the flow velocity and therefore to flow volume.By using the absolute transit times both the averaged fluid velocity and the speed of sound can be calculated.Ultrasonic flow meters measure the difference of the propagation time (transit time) of ultrasonic pulses propagating in (normally an inclination angle around 30 to 45° is used) flow direction and against the flow direction.This time difference is a measure for the averaged velocity of the fluid along the path of the ultrasonic beam
27 Ultrasonic flow-meters Measurement: FlowUltrasonic flow-metersAdvantages:With homogeneous fluids, the principle is independent of pressure, temperature, conductivity and viscosityUsable for a wide range of nominal diameters Direct meter installation on existing pipesNon-invasive measurementNo pipe constrictions, no pressure lossesNo moving parts. Minimum outlay for maintenance and upkeep
28 Coriolis Mass Flow-meters Measurement: FlowCoriolis Mass Flow-metersIf a moving mass is subjected to an oscillation perpendicular to its direction of movement, Coriolis forces occur depending on the mass flow.A Coriolis mass flow meter has oscillation measuring tubes to precisely achieve this effect.Coriolis forces are generated when a fluid (= mass) flows through these oscillating tubes. Sensors at the inlet and outlet ends register the resultant phase shift in the tube's oscillation geometry.
29 Coriolis Mass Flow-meters Measurement: FlowCoriolis Mass Flow-metersThe processor analyzes this information and uses it to compute the rate of mass flow.AdvantageThis principle is used in a huge range of industry sectors, including pharmaceuticals, chemicals and petrochemicals, oil and gas, food etc.
30 Major issues for selecting flow-meters Measurement: FlowMajor issues for selecting flow-metersAccuracyRepeatabilityLinearityReliabilityRange/SpanDynamics(Response time)SafetyMaintenanceCost
32 Measurement: Temp. Thermocouple T/C Connection IT IS BASED ON ‘SEEBECK’ EFFECT WHICH SAYS THAT WHEN HEAT IS APPLIED TO A JUNCTION OF TWO DISSIMILAR METALS AN ‘EMF’ IS GENERATED WHICH CAN BE MEASURED AT THE OTHER JUNCTIONT/C ConnectionCOMPENSATING CABLEHOT JUNCTIONTO DDC CARDSTERMINAL END CJC BOX
33 Measurement: Temp. Thermocouple Types of T/C:E,J,K,T,R,S,BK (Chromel & Alumel; Ni-Cr &Ni-Al) Type: mostly used in power plant for low temp. application )R (Platinum & Platinum-Rhodium) Type: Used for high temp. application. Highly resistant to oxidation & corrosionAdvantages: Disadvantages: -- Low Cost Sensitivity low & low voltage output- No moving parts, less likely to be broken susceptible to noise-Wide temperature range. Accuracy not better than 0.5 °C-Reasonably short response time. Requires a known temperature- Reasonable repeatability and accuracy reference
34 RESISTANCE THERMOMETER (RTD) Measurement: Temp.RESISTANCE THERMOMETER (RTD)THE RESISTANCE OF A CONDUCTOR CHANGES WHEN ITS TEMPERATURE IS CHANGED .THIS PROPERTY IS UTILISED TO MEASURE THE TEMPERATURE.Rt = Ro (1+βdT)WHERE β = TEMP CO- EFFICIENT OF RESISTANCE ; dT = TEMPERATURE DIFFERENCEWhen discussing RTDs, following must be considered:Wiring configuration (2, 3 or 4-wire)Self-heatingAccuracy RTD types:Stability Platinum (Range -200 °C to 600 °C )Repeatability Copper (Range -100 °C to 100 °C )Response time Nickel (Range -60 °C to 180 °C )
35 BIMETALLIC THERMOMETERS Measurement: Temp.THERMISTORSTHERMISTORS ARE GENERALLY COMPOSED OF SEMICONDUCTOR MATERIALS.THEY HAVE A NEGATIVE COEFFICIENT OF TEMPERATURE SO RESISTANCE DECREASES WITH INCREASE IN TEMP.Making use of Negative Temperature Coefficient characteristics, thermistor and can be applied in temperature compensation, inrush current limit, precision temp. control (temp. coefficient very large compared to RTC & T/C) etc.BIMETALLIC THERMOMETERSALL METALS EXPAND OR CONTRACT WITH TEMPERATURETHE TEMPERATURE COEFFICIENT OF EXPANSION IS NOT THE SAME FOR ALL METALS AND SO THEIR RATES OF EXPANSION AND CONTRACTION ARE DIFFERENTUSAGE: IN PROCESS INDUSTRIES FOR LOCAL TEMPERATURE MEASUREMENTSOVERLOAD CUTOUT SWITCH IN ELECTRICAL APPARATUS
36 Measurement: Temp. ACOUSTIC PYROMETER LOCAL INDICATION Acoustic Pyrometer is a non-contact measurement device that obtains highly accurate instantaneous gas temperature data in any area of the boiler, helping improve combustion efficiency.For measurement of temperatures across large spaces of known distance in a noisy, dirty and corrosive environment such as a coal-fired utility boiler, or a chemical recovery boiler.The Velocity of Sound in a medium is proportional to the Temperature.LOCAL INDICATIONLIQUID IN GLASS THERMOMETERMERCURY IN STEEL THERMOMETERBIMETALLIC THERMOMETER
37 Power Plant C&I systems 1.Field instruments/ input & output instrumentsVarious measuring instruments like Transmitters, RTD, Thermocouples, Pr. & temp. gauges, speed & vibration pick ups etc. (Analog inputs)Various Pr., Temp. & limit switches, for Interlock , protections & feedback of control element (Binary inputs)Output devices like solenoids, EP converters, Positioners etc. for controlling final control elementFinal control elements like Power cylinder, Pneumatic/ motorized actuators etc.
38 Power Plant C&I systems 2. Control SystemsVarious control cabinets for acquiring field signal (both analog & binary inputs), processing the signals as per control logic and issuing output command to output devices (Binary & analog).Various control desk devices like command consoles, Push button modules, indicators, recorders, CRTs, PC based Operator Work Stations (OWS) etc. for human machine interface for monitoring & control of the plantPower supply system(UPS)/ chargers with battery backups to ensure uninterrupted power supply of desired quality for the control system
39 Power Plant C&I systems 3. AnalyzersThe availability, reliability & efficiency of boiler unit hinge around the close control of chemical regimes of working fluid i.e. water/steam as well as combustion in the boiler. The instruments monitoring the chemical regimes and combustion are generally called analytical instruments. These instruments fall under three categoryWater/ Steam AnalyzersGas analyzersSmoke monitorsHIGH PURITY WATER IS ESSENTIAL TO MINIMISESCALINGCORROSIONCARRY OVEREMBRITTLEMENT
40 Power Plant C&I systems ANALYZERS AND MEASURMENT LOCATIONON LINE gas analyzers for measurement of flue gas oxygen, carbon mono-oxides, carbon di-oxides, oxides of sulpher & nitrogen at various location of boiler.ON LINE analyzers for measurement of conductivity, pH, silica, dissolved oxygen, phosphate, hydrazine, chloride, sodium etc. at various points in the water & steam cycle of boiler & turbine area (SWAS-steam & water analysis system).ON-LINE opacity monitors for measurement of dust concentration in flue gasON LINE analyzers for measurement of conductivity, pH, silica, dissolved oxygen etc. at various ION exchangers of DM plant .
41 Power Plant C&I systems TYPICAL VALUES OF CHEMICAL PARAMETERS BEING MEASURED (SWAS)SAMPLEPARAMETERUNITLIMITDM WATERa) Conductivityb) Cation ConductivityµS/cm<0.3Condensate pump discharge (CEP)<5c) pHd) Na+ppb<5ppbe) Dissolve oxygen (DO)<10Economizer Inletc) Hydrazine10-20Boiler water100b) pHc) SilicaSat & Main steam
42 Power Plant C&I systems 4. Laboratory Instruments & SetupActivities of C&I LabCALIBRATIONREPAIRTESTING with proper documentation & recordsCALIBRATION:Pressure switch , Transmitter , GaugeTemperature switch , Transmitter , GaugeFlow TransmitterLevel Switch
43 Power Plant C&I systems 4. Laboratory Instruments & SetupREPAIR:1. ELECTRONIC CARDS3. POWER SUPPLY MODULESTESTING:1. ELECTRONIC MODULES2. RELAYS3. POWER SUPPLY MODULES
44 Power Plant C&I systems 4. Laboratory Instruments & SetupDifferent standard instruments with traceability up to national standard . These insts. include Standard Gauges, Multimeters, Resistance boxes, mA sources, oscilloscope, signal generator etc. for calibration of measuring instruments.Dead Weight tester, Comparator, Temperature bath, Vacuum pump, manometer, soldering stations etc.Test benches with standard power supply sockets (e.g. 24VDC, 48VDC, 220VDC, 110VAC, 230VAC etc.) in each bench depending on requirement.Laboratory should be air-conditioned with monitoring of temp., humidity and barometric pressure. Also, proper provision for handling electronic cards (floor mats, ESD protective bags/ anti static bags etc.)
45 Power Plant C&I systems 4. Laboratory Instruments & SetupEssential Tools/ Infrastructure for Repairing & testingIN-CITCUIT IC TESTERESD WORK STATIONULTRASONIC CARD CLEANERSTORRAGE OSCILLOSCOPELOGIC ANALYSERTHERMOCOUPLE SIMULATORVIDEO PATTERN GENERATOREPROM PROGRAMMER
46 Power Plant C&I systems C&I systems of BoilerFSSS (Furnace safeguard supervisory system)Open loop control system (interlock & protections) of boiler auxiliariesSecondary Air Damper control system (SADC)Hydrastep for drum level measurementMeasurements, Protection & Control of Coal Feeders
47 Power Plant C&I systems FSSSFUNCTIONS OF F.S.S.SFURNACE PURGE SUPERVISIONOIL GUNS ON/OFF CONTROLPULVERISERS/FEEDERS ON/OFF CONTROLSECONDARY AIR DAMPERS CONTROLFLAME SCANNER INTELLIGENCEBOILER TRIP PROTECTIONS
48 Power Plant C&I systems FSSSWHY AT ALL A PROTECTIVE SYSTEM IS REQUIRED FOR THE BOILER?THE BOILER’S FURNACE IS CONTINUOUSLY FED WITH HIGH CALORIFIC VALUE ATOMISED FUEL WHICH IS IN THE PROCESS OF CONTINUOUS BUT CONTROLLED COMBUSTION.COMBUSTION-THE PROCESSCOMBUSTION IS A RAPID BURNING OF OXYGEN WITH FUEL RESULTING IN RELEASE OF HEAT. AIR IS ABOUT 21% OXYGEN AND 78% NITROGEN BY VOLUME. MOST FUELS CONTAIN CARBON, HYDROGEN AND SULPHUR. A SIMPLIFIED COMBUSTION PROCESS COULD BECARBON+OXYGEN=CARBONDIOXIDE+ HEATHYDROGEN+DO =WATER VAPOUR + HEATSULPHUR +DO =SULPHURDIOXIDE+ HEATWHICH MEANS THAT THE FINAL DESIRED PRODUCT OF THE PROCESS IS HEAT WHICH WE REQUIRE TO BOIL THE WATER
49 Power Plant C&I systems FSSSCOMBUSTION-THE PROBLEM : WHEN THIS CONTROLLED BURNING GOES OUT OF CONTROL DUE TO AN IMBALANCE IN THE FUEL/AIR RATIO, THERE IS EITHER A FUEL RICH MIXTURE OR A FUEL LEAN MIXTURE. IN BOTH CASES THE FLAME QUALITY BECOMES POOR. THERE IS A CHANCE OF FUEL ACCUMULATION WHICH CAN LATER ON IGNITE SUDDENLY AND CAUSE EXPLOSIONS.SO FSSS IS USED FOR SAFE AND ORDERLY STARTUP AND SHUTDOWN OF BOILER THROUGH VARIOUS INTERLOCKS AND PROTECTIONSTHE PROTECTIVE SYSTEM IN THE BOILER IS DESIGNED BASICALLY TO PREVENT OCCURRENCE OF SUCH SITUATIONS BY TAKING ADVANCE ACTIONS.
50 Power Plant C&I systems N.F.P.A Guide line & Boiler ProtectionN.F.P.A- National Furnace Protection Association, USADeals with protection for various types of furnaceProtection of Pulverized fuel fired boiler is governed by Section-85cDifferent categories of protection:a) Mandatory, b)Mandatory & automatically generated, c) Optional but alarm has to be there
51 Power Plant C&I systems BOILER FLAME & FLAME SCANNERSIt looks rather static, but in reality the fire energy fluctuates rapidly. The Fuel and Oxygen in the uncontrolled fire constantly burn as in small explosions and then sucks new Fuel & Oxygen to the flames. This process causes the flame flicker.Flicker frequency for oilflame is more than that of coal flame.
52 Power Plant C&I systems INTENSITY RELATIVE TO WAVELENGTH
53 Power Plant C&I systems FLAME SCANNERS-UV Scanners-Visible Range Scanners (Safe scan-1&2)-Used for both Oil & Coal Flame-IR Scanners (UR600 of ABB)SAFE FLAME SCANNER
54 Power Plant C&I systems C&I systems of TurbineATRS (Automatic Turbine Runup system)Turbine Governing SystemTurbovisory Instruments & turbine protectionsInterlock, Protection & Control of HPBP systemOpen loop control system (interlock & protections) of turbine auxiliariesInterlock & protections of Seal Oil & Stator water system
55 Power Plant C&I systems C&I systems for control & MIS-Automatic Control System (ACS)-DATA Acquisition system(DAS)-Distributed Digital Control Monitoringand Information System
56 Power Plant C&I systems AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPPROCESS: Process refers to the method of changing or refining raw materials to create the desired end product. The raw materials may undergo physical, chemical, or thermal state changes during the Process.Process is of Two Types :A) Continuous and B) BatchContinuous Process is one where the change of state of Input into Output occurs continuously.Ex.: Power Plant Process, Petroleum Industry etc.Batch Process is one where a Batch of the Product is produced and the Process stops till production of next Batch is started.Ex.: Automobile Production
57 Power Plant C&I systems AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPPROCESS CONTROL: Process control techniques are developed over the years to haveQuality of the end productEconomy of productionAbility to cater to emergencies and bring the process to safe shutdown.CONTROLLED CONDITION: The physical quantity or condition of a process or machine which is to be controlledCONTROL SYSTEM: An arrangement of elements interconnected and interacting in such a way that it can maintain some condition of a process or machine in a prescribed manner
58 Power Plant C&I systems AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPOPEN AND CLOSED LOOP CONTROL:A Closed Loop Control (CLCS) is one where a Process Variable is measured, compared to a Set Value and action is taken to correct any Deviation or Error from Set Value. The continuous Measurement of PV and its’ comparison to Set Point closes the Loop.An Open Loop Control(OLCS) is one where the PV is not compared with Set Value and action taken, but action is taken without regard to conditions of PV.
59 Power Plant C&I systems AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPOPEN LOOP CONTROL:Open Loop Control is accomplished by the following means:Group ControlSub-Group ControlSub-Loop ControlDrive Level ControlProgrammable Logic Control(PLC)Group Control : Start and Stoppage of a Group of equipment is accomplished by Group Control(GC).Ex. :CEP GC, Equipment Cooling GC etc.
60 Power Plant C&I systems AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPOPEN LOOP CONTROL:Sub-Group Control : Start and Stoppage of an equipment with its’ associated auxiliaries in Step-Sequence manner is done by Sub-Group Control. Operator intervention is not required in Sub-Group Control(SGC).Sub-Loop Control: Start and Stoppage of auxiliaries of an equipment is carried out by Sub-Loop Control(SLC)Drive Level Control : Start and Stop or Opening and Closure of a Drive is carried out by Drive Control. The Drive logic shall have Protection, release ,auto and manual commands and these are executed as per pre-determined logic.
61 Power Plant C&I systems AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPCLCS TERMINOLOGY:Desired Value or Set Point : The value of the variable/parameter which needs to be controlled at the required condition.Process Variable(PV) : The present value of the Parameter of Process at that particular instant. This is sometimes referred as Measured Value.Error/Deviation : It is the Difference between Set Point and Process Variable, and can be +ve or –ve. It has three components: a) Magnitude b) Duration and c) Rate of change.Controller : A Controller is a device that receives data from a Measurement Instrument, compares the data with the Set Point and if necessary, signals a Control element to take Corrective action. This Corrective action ensures that the PV shall always be maintained at the Set Value.The Controller can be a) Electronic, b) Pneumatic and c) Hydraulic type.
62 Power Plant C&I systems AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPController types: Functionally, Controllers can bea) Continuous and b) Step Controllers.Depending on the control loop; controller action can be adjusted as (i) Direct acting:-Increase of process value increases controller output(ii) Reverse acting:- Increase of process value decreases controller outputControl Element : The Control or Correcting Element is the part of the Control System that acts to physically change the Manipulated Variable.Ex. : Control Valves, Louvers or Dampers, Solenoids, Pump Motors etc.
63 Power Plant C&I systems AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPBump less Transfer : The arrangement where the transfer from auto to manual mode does not affect the process.Proportional Control : The Proportional (P) action responds only to a change in the magnitude of Error(e) i.e. controller output changes by an amount which is proportional to error.Output change of Controller in % = (Error change in %)(Gain), where Gain is called the Controller gain. The reciprocal of Gain is termed as Proportional Band(PB) and is expressed in %.Proportional Band(PB): The change in deviation required to cause the output of the controller to change from one extreme to the other.Integral Control : In Integral Control, the Controller output is a function of the Duration of Error(e).
64 Power Plant C&I systems AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPHence, the Controller output is the time Integral of Error and the time set is Integral Action Time(IAT) i.e. IAT can be defined as time taken for the integral action to change output by the same amount as the proportion action .Usually, both P and I Controls are combined and the Controllers are tuned to minimize Error(e) and controller is termed as PI controller.Derivative Control : Derivative or Rate Controller’s output is Proportional to the rate of change of Error(e). The Control action is termed as D. The action is to apply an immediate response that is equal to the P+I action that would have occurred some time in the future.
65 Power Plant C&I systems AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPImportant Closed Loop Controls in a Thermal Power Plant:a) Furnace Draft Controlb) Boiler Drum Level Controlc) HOT well & D/A level controld) Main Steam Temperature Controle) Air and Fuel Flow to Boiler Controlf) SH & RH spray controlg) Coordinated Master Control(CMC)h) Turbine Speed, Pressure and Load Control
66 Power Plant C&I systems AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPCoordinated Master ControlThis is an integrated automatic control of unit operation. There is a continuous co ordination between boiler and turbine control to maintain a balance between steam generation and steam consumption.Boiler Follow Mode (BFM)Turbine Follow Mode (TFM)Co-ordinated Master Control (CMC)Runback Mode
67 Power Plant C&I systems AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPBoiler Follow Mode (BFM)Unit load control from turbine local load set pointChange in turbine load set point will modulate turbine CVsBoiler master output gets corrected to maintain throttle pr dev.Boiler control will follow turbine controlBLI signal as feed forward signal for boiler firing rate controlResult - Boiler acts as throttle pr controller where turbine is in load controller mode
68 Power Plant C&I systems AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPTurbine Follow Mode (TFM)Unit target load set point goes to boiler masterChange in BLI will modulate turbine CVsBoiler master output gets corrected to maintain Unit load dev.Turbine control will follow boiler controlLoad deviation as feed orward signal for boiler firing rate controlResult - Boiler acts as load controller where turbine is in pressure controller mode
69 Power Plant C&I systems AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPCoordinated Master ControlUnit load is set from unit master.Unit master demand is limited by unit capability , TSE margins and unit max/min load set points.Unit target load is derived from unit master after the limitations.Unit target load is used as feed forward signal to the boiler firing rate control.Turbine control utilises the unit load as turbine load set point after adapting the same by steam generation delay.In TG throttle pressure is maintained by correcting the BMD output depending on the throttle pr dev.Result: Balance is achieved between steam generation and steam consumption PROPER COORDINATION BETWEEN BOILER CONTROL AND TURBINE CONTROL
70 Power Plant C&I systems DATA ACQUISITION SYSYTEM-DASWHY DAS IS REQUIRED IN THERMAL POWER PLANTS ?SAFE & RELIABLE OPERATION OF THE UNIT OR EQUIPMENTSASSIST CONTROL ROOM OPERATORS BY PROVIDING TIMELY ANNUNCIATION OF ALL ABNORMAL CONDITIONSPROVIDE DETAILED INFORMATION ON THE PLANT PERFORMANCEPROVIDE MANAGEMENT WITH ACCURATE RECORDS ON THE PAST PLANT PERFORMANCE FOR ANALYSIS
71 Power Plant C&I systems DATA ACQUISITION SYSYTEM3 MAJOR FUNCTIONS OF DAS:DATA ACQUISITIONDATA PROCESSINGDATA REPRESENTATIONThe Major PartsProcess Control Units ( PCU )Computer Interface Unit ( CIU )Termination Units ( TU )Buffer Terminal Cabinets ( BTC )
72 Power Plant C&I systems DATA ACQUISITION SYSYTEMTYPES OF DATA (Input): Analog & DigitalAnalog inputs:1. Thermocouple Input ( mV )K-Type T/C ( Cr-Al ) : For temp < 600 Deg C& used in Flue Gas path after FSH outlet.R-Type T/C ( Pt-Pt-Rh ) : For temp > 600 Deg C used in PSH & FSH region of FG path.2. RTD Input ( Resistance )Pt-100 RTD : For Brg. Temp measurement.Cu-53 RTD : For HT motor & Generator Stator winding temp. measurement.
73 Power Plant C&I systems DATA ACQUISITION SYSYTEMAnalog inputs:– 20 Ma InputComing from Pr. / Flow Transmitters.Coming from Signal Distribution Cards of automatic control system4. 0 – 10 Volt InputComing from ATRS cabinetsUsed for Turbine Brg. Temp. /Vibration measurement.DIGITAL INPUTSThese are coming directly from switches or relay contacts of other systems (FSSS, ATRS, ACS etc.)
74 Power Plant C&I systems DATA ACQUISITION SYSYTEMDIGITAL INPUTS (TYPES)LOW RESOLUTION : The scanning time of inputs is second.HIGH RESOLUTION : The scanning time is millisecond. These are called Sequence Of Events ( SOE ) Inputs.PULSE INPUT : For calculation of Total Coal Flow, Total Air Flow etc.
75 Power Plant C&I systems DATA ACQUISITION SYSYTEMFUNCTIONS OF DAS:Alarm Management.Production of hardcopy print outs in different printers.Operator Guidance Messages.Graphic Displays of plant sub-systems.Trending of analog variables on recorders.Sequence Of Events ( SOE ) recording following unit / equipment trip conditions.Efficiency calculations
76 Power Plant C&I systems DATA ACQUISITION SYSYTEMDATA PROCESSING: It has the following partsCOMPUTER PROCESSING UNIT ( CPU )BULK ( SOLID STATE ) MEMORY WITH BATTERY BACKUPMAGTAPE UNITCOMMUNICATION CABINET & MODEMMOVING HEAD DISC DRIVEVIDEO HARD COPIERTREND RECORDERUNIT CONTROL DESK & PROG. ROOM CRTPRINTERS
77 Power Plant C&I systems DATA ACQUISITION SYSYTEMFeatures:REAL TIME VARIABLE CALCULATIONSumming, Subtraction, Maximum , Minimum, Averaging, Hourly & Daily integration, rate of changes & comparison of limits etc.ON-LINE DATABASE EDITION1. Assign points to any process parameter2. Scan, Off-scan , Delete , Activate , inactivate a process parameters , calculated points when reqd.3. Change the Engg. Unit4. Change the range , alarm limits & dead bands5. Change the scan frequency6. Review total analog and digital points depending on its quality flag like alarm , channel failure , off-scan etc.
78 Power Plant C&I systems DATA ACQUISITION SYSYTEMALARM MANAGEMENT:All the analog points which cross their normal limits or all the digital points which go into their alarm state come on the alarm CRT with associated time & blink as long as the alarms remain unacknowledged.Alarm will come in RED colourIf all the pages are full (normally no. of alarm pages & alarm per page is predefined) and any new alarm comes , then oldest alarm will disappear from the alarm page as FIFO basisAlarm print out will be available in alarm printer
79 Power Plant C&I systems DATA ACQUISITION SYSYTEMDATA REPRESENTATION:Printed outputs of displays /collection of data in different formats like :1. Copy Screen2 Alarm Print out3. Log Print outCRT Displays1. Alarm CRT display2. Utility CRT display
80 Power Plant C&I systems DATA ACQUISITION SYSYTEMDATA REPRESENTATION:TYPES OF TREND LOG PRINOUTSTIME ACTIVATEDEVENT ACTIVATEDDEMAND LOGSSOE PRINTOUTTIME ACTIVATED LOG:Automatic Triggered LogsSample frequency is 1 Hour.(Normally)Time of trigger can be specified
81 Power Plant C&I systems DATA ACQUISITION SYSYTEMTIME ACTIVATED LOG:Max. 15 nos. of points can be assignedNormally printed in the logging printer in UCBExamples :1. Shift Log2. Efficiency Log3. Boiler Drum / Tube Metal Temp. Log4. FSH / RH Metal temp. excursion LogEVENT ACTIVATED LOG:Automatic Triggered LogsUsed for Unit or Equipment Outage AnalysisMinimum Sample frequency is 10 seconds.
82 Power Plant C&I systems DATA ACQUISITION SYSYTEMEVENT ACTIVATED LOG:Max. 36 points can be assigned in a logLogs are triggered by a Trip flagNormally printed on Logging Printer in UCBPre & Post triggered points can be specifiedExamples :1. Post Trip Analysis Log ( PTL )2. TG. Shutdown Analysis Log3. Boiler Startup Log.4. Turbine / Generator Diagnostic Logs
83 Power Plant C&I systems DATA ACQUISITION SYSYTEMDEMAND LOG:Not Automatic Triggered LogsLogs can be printed on operator’s demandSample frequency is generally 1 Hour.Logs are printed in Logging Printer in UCB
84 Power Plant C&I systems DATA ACQUISITION SYSYTEMSEQUENCE OF EVENTS ( SOE )THE MAIN FEATURES ARE:Determines First Cause Of TripDetermines sequence of events or alarmsScanning Time is 1 millisecond.It is a Stand Alone SystemMax. 256 nos. of Protection related digital points can be assignedAutomatic Triggered when any point in alarm
85 Power Plant C&I systems DDCMISWHAT IS DDCMIS ?DISTRIBUTED DIGITAL CONTROL MONITORING & INFORMATION SYSTEMDistributed means there is no centralized control and control is spread across multiple unitsDigital means processing of process information is done in digital form using micro-processor based hardwareMIS interfaces the human with process using computers
86 Power Plant C&I systems DDCMISTECHNOLOGICAL BACKGROUNDPROGRESS OF INSTRUMENTATION USED TO IMPLEMENT AUTOMATIC PROCESS CONTROLLOCAL PNEUMATIC CONTROLLERSMINIATURIZED AND CENTRALIZED PNEUMATIC CONTROLLERS AT CONTROL PANELS AND CONSOLESSOLID-STATE CONTROLLERSCOMPUTERISED CONTROLSDISTRIBUTED MICROPROCESSOR BASED CONTROL
87 Power Plant C&I systems DDCMISComponentsMAN MACHINE INTERFACE & PROCESS INFORMATION SYSTEMDATA COMMUNICATION SYSTEM (DATA HIGH WAY)CONTROL SYSTEM
88 Power Plant C&I systems DDCMISMAN-MACHINE INTERFACE AND PLANT INFORMATION SYSTEM (MMIPS)LATEST STATE-OF-THE-ART WORKSTATIONS AND SERVERS BASED ON OPEN-ARCHITECTURE AND INDUSTRY STANDARD HARDWARE AND SOFTWARE TO ENSURE BETTER CONNECTIVITY.e.g. HARDWARE FROM COMPAQ/DIGITAL, HP, SUN MICRO-SYSTEM OR OTHER MAJOR SUPPLIERS (LESS DEPENDENCE ON THE C&I SYSTEM SUPPLIER IN THE LONG RUN)OPERATING SYSTEM WINDOWS-NT, OPEN-VMS OR UNIX.PROVISION OF LVSCONNECTION TO OTHER SYSTEM THROUGH STATIONWIDE WAN
89 Power Plant C&I systems DDCMISMMIPIS FUNCTIONALITIESVARIOUS PLANT EQUIPMENT OPERATIONOPERATOR INFORMATIONS THROUGH VARIOUS DISPLAYSALARMS, LOGS, HISTORICAL AND LONG TERM STORAGE.PERFORMANCE AND OTHER CALCULATIONS
90 Power Plant C&I systems DDCMISDATA COMMUNICATION SYSTEMLOCAL SYSTEM BUS – It is just lines on the backplane of control panel to which all the modules are connected directly. It serves as communication medium between the modules.INTRAPLANT BUS(IPB) – It is a coaxial cable which runs through all the panels of control system and interconnects them.LOCAL AREA NETWORK(LAN) – It is a network of computers which are connected to a single point (HUB).FOR ALL BUSES REDUNDANCY IS PRESENT
91 Power Plant C&I systems DDCMISCONTROL SYSTEMFUNCTIONAL DIVISIONSG-C&I SYSTEMTG-C&I SYSTEMBOP-C&I SYSTEMHARDWARE COMPONENTSPOWER SUPPLYCONTROL PANELELECTRONIC MODULES
93 Power Plant C&I systems DDCMISSG-C&I SYSTEMBURNER MANAGEMENT SYSTEM (BMS)SOOT BLOWER CONTROL SYSTEM (SBC)SECONDARY AIR DAMPER CONTROL SYSTEM (SADC)AUXILIARY PRDS CONTROLS (APRDS)TG-C&I SYSTEMELECTRONIC TURBINE PROTECTION (ETP)AUTOMATIC TURBINE RUN-UP SYSTEM (ATRS)AUTOMATIC TURBINE TESTING SYSTEM (ATT)ELECTRO- HYDRAULIC TURBINE CONTROL SYSTEM (EHTC)TURBINE STRESS CONTROL SYSTEM (TSC)LP BYPASS SYSTEM (LPBP)HP BYPASS SYSTEM(HPBP)GLAND STEAM PRESSURE CONTROLGENERATOR AUXILIARY MONITORING PANEL (GAMP)
94 Power Plant C&I systems DDCMISBOP-C&I SYSTEMCONSISTS OF OPEN LOOP CONTROL SYSTEM (OLCS) AND CLOSED LOOP CONTROL SYSTEM (CLCS)OLCS - THE SEQUENCE CONTROL, INTERLOCK OF ALL THE PLANT SYSTEMS WHICH ARE NOT COVERED IN THE SG-C&I AND TG-C&I. THIS INCLUDES MAJOR AUXILIARIES LIKE FD/ID/PA FANS, AIR-PREHEATER, BFP/CEP/CWP/ BCWP , DMCWP/CLCWP AND ELECTRICAL BREAKERS.CLCS - THE MODULATING CONTROL FOR VARIOUS IMPORTANT PLANT PARAMETERS, LIKE FW FLOW (DRUM LEVEL), FURNACE DRAFT, COMBUSTION CONTROL (FUEL FLOW AND AIR FLOW), PA HDR PRESSURE CONTROL, DEAERATOR/HOTWELL/HEATER LEVEL CONTROLS ETC.
95 Power Plant C&I systems DDCMISWHY DDCMIS ?VERY HIGH FLEXIBILITY FOR MODIFICATION IN CONTROL STRATEGYVERY HIGH SELF-DIAGNOSTICVERY LOW DRIFT (ONLY IN I/O CARDS) , HENCE NO NEED OF FREQUENT RE-CALIBRATIONMUCH HIGHER RELIABILITY (BASED ON MTBF)BETTER LONG TERM SUPPORT DUE TO CHANGING TECHNOLOGYMUCH BETTER OPERATOR INTERFACE
96 Power Plant C&I systems DDCMISSALIENT FEATURES OF DDCMISINTEGRATED PLANT CONTROL FOR SG, TG AND BALANCE OF PLANT CONTROLIT MAY BE REMEMBERED THAT HISTORICALLY THE TERM DDCMIS USED REFER TO THE SO-CALLED “BOP-C&I” . THE SG-C&I, i.e. FSSS etc. TG-C&I i.e. ATRS, TURBINE PROTECTION etc. ORIGINALLY WERE NOT CONSIDERED UNDER DDCMIS OR DCS AS PER MANY SUPPLIERS. ONLY RECENTLY THE TYPE OF SYSTEMS FOR ALL THE SYSTEMS HAVE BECOME SIMILAR (WITH SOME DIFFERENCE WHICH WILL BE DISCUSSED LATER), WE TEND TO CONSIDER THESE SYSTEMS UNDER DDCMIS.
97 Power Plant C&I systems DDCMISSALIENT FEATURES OF DDCMISINTEGRATED PLANT OPERATION THROUGH FULLY INTERCHANGEABLE OPERTAOR WORK STATIONS (OWS) FOR SG, TG AND BALANCE OF PLANTPROVISION OF EXTENSIVE SELF-DIAGNOSTICSUSE OF LARGE VIDEO SCREENS FOR PROJECTIONS OF VARIOUS PLANT MIMICS ETC.PROVISION OF FAULT ALARM ANALYSIS TO GUIDE THE OPERATOR TO THE MOST LIKELY EVENTPROVISION OF ADEQUATE RELIABILITY AND AVAILABILITY WITH PROPER REDUNDANCY IN SENSOR, I/O AND CONTROLLER LEVELS.
98 Power Plant C&I systems Global & National Power ScenarioGlobal:Global electricity consumption 69% higher in than 200380% of energy provided from thermal sourcesEmerging trend from Thermal to Hydel and Renewable Energy sourcesIndian:Total installed capacity only MW in 1947Per Capita consumption 631 units ( ) only with installed capacity of 1,77,000 MWGDP growth of 8%, power growth required 10%To add 1,00,000MW capacity by 2017Liberalizations of the sector
99 Power Plant C&I systems NTPC at a glance:Installed Capacity MWTarget 75000MW by 2017Performance:Annual Availability 91.62%Annual PLF 88.29%11 stations among top 20 in the country
100 NTPC Practices to achieve goal KEY THRUST AREASZero Human ErrorImplementation of trip committee recommendations judiciously / rigorouslyIdentification of trip committee recommendations of other stationswhich are relevant and implement themImplementation of operation memorandum wherever applicableDissemination of information about best practices followed acrossNTPC and other Power StationsProviding proper environment for C&I equipment to reduce probability ofcard and equipment failure
103 INFERENCE : 2009-10 C&I OUTAGE ANALYSIS Major factors contributing to C&I outage in :Control System related failure2. Field Device Failure3. Soft ware/Card Failure4. Power Supply/Relay failure5. Human error
104 BEST PRACTICES COMPILED/ADOPTED IN NTPC C&I All ‘unit protections’ are provided with 2/3 logic and audio visual alarm is provided on 1/3 to operator on actuation of any one sensor wherever possible with proper approval.Use of headless RTD in tripping circuit of ID/PA/FD fans & BFPs.Resistance mapping of critical solenoids including cable during overhauls and monitoring trend to identify any defects.Marking of trip related devices and Junction Boxes marked in RED color.Regular calibration of all important instruments which have a bearing on unit safety, reliability and efficiency. Instruments are calibrated against standard instruments with traceability to NABL.
105 BEST PRACTICES COMPILED/ADOPTED IN NTPC C&I For handling of electrostatic sensitive electronic hardware, electrostatic bags, wrist straps and other ESD handling devices are employed in control panels and lab. All Laboratories are provided with ESD proof workstations.Disable removable drives of servers and workstations.Single source responsibility for software backup of DCS and storage in fire proof cabinets in two different locations.Detailed work instruction are prepared and followed for working on all trip related devices.
106 BEST PRACTICES COMPILED/ADOPTED IN NTPC C&I A single source responsibility is fixed for the generation and maintenance of system passwords so as to maintain system securityInternal quality inspection for critical checks during overhauls to ensure quality in overhaul worksNear miss situations are monitored and analyzed. The learning from this area used to formulate strategies to avoid spurious outages.All power supply voltages are monitored with a fixed periodicity and maintained within /- 10% of the rated value.
107 BEST PRACTICES COMPILED/ADOPTED IN NTPC C&I Fuses used in UPS and protection circuits are replaced with new fuses of same rating and type during every overhaulEarth voltages in control panels are monitored on a predetermined frequency and the values are recorded for trendingAll bus terminators are checked during every overhaul for ensuring integrity of bus communication in DDCMIS systemsLoad testing of power supplies for critical applications and replacement of power supply modules or electrolytic capacitor and power transistors used in power supply if found deteriorated.
108 Other important actions taken for forced outage reduction Other important actions taken for forced outage reductionRerouting of control & power cables in hot zonesPanel power supply monitoring in regular intervals.CER/UCB temperature and humidity monitoring online. Insisting for performance of the A/C systemChecking and tightening power supply cables during overhaulEnsuring healthiness of cabinet cooling fans.
109 Other important actions taken for forced outage reduction Panel cooling fans supply segregation from system supply with MCB / fuse.Cleaning of air filters on panels periodicallyServo valve replacement/ servicing in hydraulic drives.Individual fuse protection in 220VDC MFT for HOTV, LOTV, HORV, Scanner emergency air damper solenoids
110 Looking from WBPDCL Santaldih Perspective KEY THRUST AREASCommissioning of non commissioned systemsSoot blowing Steam Pr. Control valve:Status- Actuator damaged while commissioning. BHEL has placed PO on OEM M/s MIL for procurement of damaged partsb) Commissioning of SWAS analyzers:Status-Procurement of Reagents for reagent based measurement (i.e. Silica etc.) is in process.Suggested to take up with OEM (Forbes Marshall) through BHEL for commissioning of electrode based measurements (i.e. conductivity etc.)
111 Looking from WBPDCL Santaldih Perspective c) Electromatic Relief Valve (ERV):Status- Solenoid Installed and cabling doned) APH Rotor stop alarm:Status- Issue pending with BHEL for longtime. Alternative scheme through DDCMIS suggested by fixing proximity switch on APH rotor shaft at support brg. end.APH fire detection alarm:Status- Issue pending with BHEL for longtime. Alternative scheme by measuring APH metal temp. using thermocouples in Air & Gas path may be thought of.
112 Looking from WBPDCL Santaldih Perspective f) Commissioning/testing of Back up (Back up of MAX DNA system work stations)Push Button console for unit control:Suggested to test the operation of various push buttons at the time of Start up/ Shutdown of unit jointly with operation.2. Rectification of long pending problems:a) Problem of SADC systemsStatus: Operation of some of the dampers erratic and needed frequent adjustment due to unreliable performance of actuator/positionerSuggested to procure 04 nos. actuator with positioner of reputed manufacturer for replacement in one elevation on trial basis
113 Looking from WBPDCL Santaldih Perspective b) High PA flow to Mills:In auto PA flow of all mills are about 30% more than characteristic flow. PA flow curve for sliding set point may be set as per mill design.Also provision of manual set point may be explored to cater poor coal quality3. Setting up of C&I Lab with requisite facilities4.Enhancing reliability of Field InstrumentsProper glanding/ sealing of field instruments, control valves, routing & dressing of cables, ensuring cleanliness & closure of all LIEs etc.
114 Looking from WBPDCL Santaldih Perspective Replacement of unreliable instruments by quality instrumentsc) Marking of protection related JBs to avoid human errorRegular walk down check in various areas to ensure the healthiness of field instruments.5. Sealing & Cable dressing in MAX DNA panels during unit Shutdown6. Disabling various ports for removable drives of MAX DNA work stations for system reliability7. Installation of ON Line printers of MAX DNA system for daily LOGs. Daily LOGs are essential for analysis of different plant parameters by O&E dept.
115 Looking from WBPDCL Santaldih Perspective 8. Cleanliness of NETWORK ROOM & EWS room to be ensured. Monitoring of Temp. & Humidity of CER, UCB , NETWORK & EWS rooms.9.Implementation of regular cleaning schedule & preventive mtc. Schedule for Boiler, Turbine and common systems10.Prepartion of detail job list for unit overhauling11. Review of spares status and timely action for procurement for breakdown(corrective), preventive and overhauling maintenance.