SRLPN Power Plant Measurement and Instrumentation

Thermal Power PlantInstrumentation, Measurement and Control

Rajneesh VachaspatiRoll No.:-ERPD 1301

IIT-MANDI

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INSTRUMENTATION & CONTROLS

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Instrumentation & Control deals with various measurement, indication, transmission and control in different technical fields.

Instrumentation is for measurement of various parameters.

And control is used for controlling various parameters from a remote control room.

Instruments

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Instruments for measuring various physical quantities likePressureTemperatureLevelFlowTurbo supervisory

Vibration Speed etc.

AnalyticalPHConductivity Silica etc

Instruments

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Measuring Electrical parameters such as LoadMVARFrequencyVoltageCurrent etc.

IndicatorsLocalRemote

RecordersSingle PointMultipointContinuousDotted

Measurement: PressurePressure Measuring devices

Manometers using water ,mercury and other liquids of known density For measuring low pressures.

Mechanical/Elastic Pressure Sensors Electrical Pressure Transducers

For measuring pressure of all ranges for tele metering purposes.Manometer: A simple pressure measurement technique. May be used for gauge, differential, and absolute measurements with a suita

ble reference. Useful mainly for lower pressure work because the height of the column of m

ercury will otherwise become very high. The difference in column heights gives the pressure reading

Measurement: Pressure

Elastic Pressure SensorsThe basic pressure sensing elements: -

A: C-shaped Bourdon tube , B: Helical Bourdon tube , C: flat diaph

ragm

D: Convoluted diaphragm, E: Capsule , F: Set of bellows

Measurement: PressureElectrical Pressure Sensors

1. Potentiometer Sensor2. Inductive3. Capacitive 4. Piezoelectric5. Strain Gauge

Usually 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 4-20

mA dc


Pressure SwitchesApplications

Alarm (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.

Sensing Element

ConditioningCircuit

Bourdon TubeBellows

DiaphragmStrain Gauge

Mechanical SwitchTransistor

Set Point


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 Seal

Siphon


Pressure Snubbers To filter out pressure spikes, or to average out pressure pulses, snubbers are

installed between the process and the instrument Instrument indicates avg pr.

Snubber Before use After use when 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.


Chemical Seal or diaphragm Protector Chemical seals are used when media can falsify the

pressure measurements due to high temperature, high viscosity or their property to crystallise


Siphon A 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.

Measurement: Flow

Types of flow meters:1. Orifice Flow meter 2. Rota meter3. Venturi Tubes4. Pitot Tube5. Target flow meter6. Ultrasonics flow meter7. Coriolis Mass Flow meter

Several sensors rely on the pressure drop or head occurring as a fluid flows by a resistance. The relationship between flow

rate and pressure difference is determined by the Bernoulli equation.

Orifice Flow-meters

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.

Orifice Plates

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Venturi Tubes

A venturi tube also measures flow rates by constricting fluids and measuring a differential pressure drop.

Venturi tubes allow for flow measurement with lower head losses than orifice plates.

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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

Rotameters

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Rather than using a constant restriction area and a variable pressure differential, rotometers use a variable restriction and a constant pressure differential to measure flow.

Typically, rotometers are used to measure smaller flows and the reading is usually done locally, although transmission of the readings is possible.

Rotameters

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Rotameters

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The rotometer consists of a float that moves vertically through a slightly tapered tube.

As fluid enters the bottom of the rotometer, the float is forced upward until the force is balanced by gravitational forces.

Most rotometers are made of glass with markings on the outside so that flow readings can be taken visually.

The advantage to rotometers is the simplicity of the device and a constant pressure drop.

Also, rotometers do not require straight pipe runs for installation so they can be installed just about anywhere.

Target Meters

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A target flow meter operates just as the name implies.A small "bulls eye" is placed inside the pipe and is

connected to a pneumatic transmitter.Typical applications include flow measurement of

steam and outdoor liquids. In a target flow meter, the square of the force exerted

on the target is proportional to the volume or mass flow through the pipe.

Target Meters

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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.

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.

Measurement: FlowPitot 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.

Measurement: Flow

Ultrasonic fUltrasonic flow-meterslow-meters

Ultrasonic flow measurement is based on elementary transit time difference between emitted & received signal.

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.

Measurement: Flow

Ultrasonic flow-meters This 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

http://en.wikipedia.org/wiki/Ultrasonic_flow_meter

Measurement: FlowUltrasonic flow-metersUltrasonic flow-meters

Advantages: With homogeneous fluids, the principle is independent of pressure,

temperature, conductivity and viscosity .

Usable for a wide range of nominal diameters, the meter can directly installed on existing pipes.

Non-invasive measurement.

No pipe constrictions, no pressure losses .

No moving parts. Minimum outlay for maintenance and upkeep

Measurement: Flow

Major issues for selecting flow-meters

Accuracy RepeatabilityLinearityReliabilityRange/SpanDynamics(Response time)SafetyMaintenanceCost

Measurement: TemperatureMeasurement Devices

Thermocouples

Resistance Thermometers

Thermistors

Bimetallic Thermometers

Acoustic Pyrometers

Local Instruments i.e. Temp. Gauges

Measurement: Temperature

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Expansion of Solids Thermostats

Expansion of Liquids Temperature Gauges

Expansion of gases Temperature Gauges

Thermal Electricity Thermocouples Type K Chromel Alumel etc.

Change of Electric Resistance (RTD)Pt100Cu53

Intensity of total radiation Optical Pyrometer Radiation Pyrometer


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Expansion of Liquids and gases are used for local gauges.

Thermocouples and RTDs are used for most of the remote temperature measurements and controls.

RTDs are used for low temperature applications.

Pyrometers are used for high temperature measurements. (NON Contact type).


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(a) Type of Thermocouple:-16 AWG wire of chromel-Alumel (Type K) or 24 AWG wire Pt-Rhodium Pt (Type R); ungrounded type depending on operating temperature range.

(b)Type of RTD:-3/4 wire - Pt RTD 100 ohm (as per DIN-43760)


Thermocouple 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 JUNCTION

T/C Connection

Measurement: Temperature.

ThermocoupleTypes of T/C:E,J,K,T,R,S,B

K (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 & corrosion

Advantages: - 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

Measurement: TemperatureDATA ACQUISITION SYSYTEM

TYPES OF DATA (Input): Analog & Digital

Analog 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 Bearing Temp. measurement. Cu-53 RTD : For HT motor & Generator Stator winding temp.

measurement.

Measurement: TemperatureRESISTANCE THRTDRT

(RTD) The Resistance Of a Conductor Changes When It's Temperature is Changed. This Property is utilized 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-heating • Accuracy RTD types:• Stability 1. Platinum (Range -200 °C to 600 °C )• Repeatability 2. Copper (Range -100 °C to 100 °C ) • Response time 3. Nickel (Range -60 °C to 180 °C )


THERMISTORSThermistors are semiconductor materials having negative coefficient of

thermal expansion. Making use of Negative Temperature Coefficient characteristics, thermistor can be applied in temperature compensation, inrush current limit, precision temp. control (temp. coefficient very large compared to RTC & T/C) etc.

BIMETALLIC THERMOMETERS All metals expand or contract with temperature The temperature coefficient of expansion is not the same for all metals

and so their rates of expansion and contraction are different USAGE: In process industries for local temperature measurements overload cutout switch in electrical apparatus

Measurement: TemperatureACOUSTIC PYROMETER

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 INDICATION Liquid in Glass Thermometer Mercury in Steel Thermometer Bimetallic Thermometer

BOILER RELATED CONTROL & INSTRUMENTATION SYSTEM/EQUIPMENTS

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FLAME MONITORING SYSTEM

COAL FEEDERS CONTROL AND INSTRUMENTATION

ELECTROMATIC SAFETY VALVES

FURNACE TEMPERATURE PROBES

ACCOUSTIC PYROMETERS

BOILER FLAME ANALYSING SYSTEM (IN LATEST ADVANCE BOILER )

BOILER RELATED CONTROL & INSTRUMENTATION SYSTEM/EQUIPMENTS

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COAL BUNKER LEVEL MONITORING SYSTEM

ELECTRONIC REMOTE DRUM LEVEL MONITORING SYSTEM (Hydra step)

CONDUCTIVITY TYPE LEVEL SWITCHING SYSTEM

ASLD SYSTEM

APH FIRE SENSING

Level Measurement

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Floats and liquid displacersHead pressure measurementDP typeUltrasonicDirect ViewingStrain gauge

Level Measurement

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In closed pressurised vessels, Differential pressure measurement is used to measure the level.

One side condensate pot is used where constant level is maintained.

Other side is connected to the bottom of the vessel.

Difference between these two heads gives the level.

Level Measurement (Closed Vessel)

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Level Measurement (Closed Vessel)

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Level Measurement (Float)

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Power Plant C&I systems

Field instruments -input & output instruments

a) Various measuring instruments like Transmitters, RTD, Thermocouples, Pr. & temp. gauges, speed & vibration pick ups etc. (Analog inputs)

b) Various Pr., Temp. & limit switches, for Interlock , protections & feedback of control element (Binary inputs)

c) Output devices like solenoids, EP converters, Positioners etc. for controlling final control element

d) Final control elements like Power cylinder, Pneumatic/ motorized actuators etc.


Control Systemsa) Various 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).

b) 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 plant

c) Power supply system(UPS)/ chargers with battery backups to ensure uninterrupted power supply of desired quality for the control system

Power Plant C&I systems Analyzers

The 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 category

i) Water/ Steam Analyzers

ii) Gas analyzers

iii) Smoke monitors HIGH PURITY WATER IS ESSENTIAL TO MINIMISE SCALING CORROSION CARRY OVER EMBRITTLEMENT

Power Plant C&I systems MEASURMENT LOCATION

a) ON LINE gas analyzers for measurement of flue gas oxygen, carbon mono-oxides, carbon di-oxides, oxides of sulpher & nitrogen at various location of boiler.

b) 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).

c) ON-LINE opacity monitors for measurement of dust concentration in flue gas

d) ON LINE analyzers for measurement of conductivity, pH, silica, dissolved oxygen etc. at various ION exchangers of DM plant .


TYPICAL VALUES OF CHEMICAL PARAMETERS BEING TYPICAL VALUES OF CHEMICAL PARAMETERS BEING MEASURED (SWAS)MEASURED (SWAS)

SAMPLE PARAMETER UNIT LIMITDM WATER a) Conductivity

b) Cation Conductivity µS/cm

<0.3

Condensate pump

discharge (CEP)

a) Conductivityb) Cation Conductivity µS/cm <5

<0.3

c) pH 9.0-9.2

d) Na+ ppb <5ppb

e) Dissolve oxygen (DO) ppb <10

Economizer Inlet

a) Conductivityb) Cation Conductivity

µS/cm <5<0.3

c) Hydrazine ppb 10-20

Boiler water a) Conductivity µS/cm 100

b) pH 9.1-9.4

c) Silica ppb 100Sat & Main steam a) Conductivity

b) Cation Conductivity µS/cm <5<0.3

Power Plant C&I systems4. Laboratory Instruments & Setup

Activities of C&I Lab

CALIBRATION

REPAIR

TESTING with proper documentation & records

CALIBRATION: Pressure switch , Transmitter , Gauge

Temperature switch , Transmitter , Gauge

Flow Transmitter

Level Switch


4. Laboratory Instruments & Setup

REPAIR:1. ELECTRONIC CARDS

2. POWER SUPPLY MODULES

TESTING:1. ELECTRONIC MODULES

2. RELAYS

3. POWER SUPPLY MODULES

Power Plant C&I systemsLaboratory Instruments & Setup

a) Different 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.

b) Dead Weight tester, Comparator, Temperature bath, Vacuum pump, manometer, soldering stations etc.

c) Test benches with standard power supply sockets (e.g. 24VDC, 48VDC, 220VDC, 110VAC, 230VAC etc.) in each bench depending on requirement.

d) 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.)


C&I systems of Boiler - FSSS (Furnace safeguard supervisory system)

- Open loop control system (interlock & protections) of boiler auxiliaries

- Secondary Air Damper control system (SADC)

- Hydra step for drum level measurement

- Measurements, Protection & Control of Coal Feeders

Power Plant C&I systemsFSSS

FUNCTIONS OF F.S.S.S

1. FURNACE PURGE SUPERVISION

2. OIL GUNS ON/OFF CONTROL

3. PULVERISERS/FEEDERS ON/OFF CONTROL

4. SECONDARY AIR DAMPERS CONTROL

5. FLAME SCANNER INTELLIGENCE

6. BOILER TRIP PROTECTIONS

Power Plant C&I systems FSSS

The boiler’s furnace is continuously fed with high calorific value atomized fuel which is in the process of continuous but controlled combustion.

COMBUSTION-THE PROCESS Combustion is a rapid burning of oxygen with fuel resulting in release of

heat. air is constituted of about 21% oxygen and 78% nitrogen by volume. most fuels contain carbon, hydrogen and sulphur. a simplified combustion process could be

C+O2=CO2+ HEAT H2+O2 =H2O+ HEAT S +O2 =SO2 + HEAT which means that the final desired product of the process is heat

which we require to boil the water


FSSS

COMBUSTION-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 protections

The protective system in the boiler is designed basically to prevent occurrence of such situations by taking advance actions.


FLAME SCANNERSE-UV Scanners-Visible Range Scanners (Safe scan-1&2)-Used for both Oil & Coal

Flame-IR Scanners (UR600 of ABB)

SAFE FLAME SCANNER


C&I systems of Turbine

- ATRS (Automatic Turbine Run up system)- Turbine Governing System

- Turbo supervisory Instruments & turbine protections

- Interlock, Protection & Control of HPBP system

- Open loop control system (interlock & protections) of turbine auxiliaries

- Interlock & protections of Seal Oil & Stator water system

Power Plant C&I systemsAUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP

PROCESS: 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) Batch Continuous 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


AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOP

PROCESS CONTROL: Process control techniques are developed over the years to have

Quality of the end product Economy of production Ability 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 controlled

CONTROL 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



OPEN 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.


OPEN LOOP CONTROL:Open Loop Control is accomplished by the following means:

Group Control Sub-Group Control Sub-Loop Control Drive Level Control Programmable 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.


OPEN 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.

Power Plant C&I systemsCONTROL SYSTEM & POWER PLANT CONTROL LOOP

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.



Important Closed Loop Controls in a Thermal Power Plant:

a) Furnace Draft Control

b) Boiler Drum Level Control

c) HOT well & D/A level control

d) Main Steam Temperature Control

e) Air and Fuel Flow to Boiler Control

f) SH & RH spray control

g) Coordinated Master Control(CMC)

h) Turbine Speed, Pressure and Load Control


Coordinated Master Control

This 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


AUTOMATIC CONTROL SYSTEM & POWER PLANT CONTROL LOOPBoiler Follow Mode (BFM)

• Unit load control from turbine local load set point

• Change in turbine load set point will modulate turbine CVs

• Boiler master output gets corrected to maintain throttle pr dev.

• Boiler control will follow turbine control

• BLI signal as feed forward signal for boiler firing rate control

• Result - Boiler acts as throttle pr controller where turbine is in load controller mode



Turbine Follow Mode (TFM)

• Unit target load set point goes to boiler master

• Change in BLI will modulate turbine CVs

• Boiler master output gets corrected to maintain Unit load dev.

• Turbine control will follow boiler control

• Load deviation as feed orward signal for boiler firing rate control

• Result - Boiler acts as load controller where turbine is in pressure controller mode


Coordinated Master Control• Unit 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

Power Plant C&I systemsDATA ACQUISITION SYSYTEM-DAS

WHY DAS IS REQUIRED IN THERMAL POWER PLANTS ?

Safe & reliable operation of the unit or equipments.

Assist control room operators by providing timely annunciation of all abnormal conditions

Provide detailed information on the plant performance

Provide management with accurate records on the past plant performance for analysis

Power Plant C&I systemsDATA ACQUISITION SYSYTEM

3 MAJOR FUNCTIONS OF DAS:

DATA ACQUISITION DATA PROCESSING DATA REPRESENTATIONThe Major Parts

Process Control Units ( PCU ) Computer Interface Unit ( CIU ) Termination Units ( TU ) Buffer Terminal Cabinets ( BTC )

Power Plant C&I systemsDATA ACQUISITION SYSYTEM

FUNCTIONS 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


DATA PROCESSING: It has the following parts

COMPUTER PROCESSING UNIT ( CPU )

BULK ( SOLID STATE ) MEMORY WITH BATTERY BACKUP

MAGTAPE UNIT

COMMUNICATION CABINET & MODEM

MOVING HEAD DISC DRIVE

VIDEO HARD COPIER

TREND RECORDER

UNIT CONTROL DESK & PROG. ROOM CRT

PRINTERS


ATA ACQUISITION SYSYTEM

ALARM 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 colour

If 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 basis

Alarm print out will be available in alarm printer

ReferencesBHEL operation manual for 210 MW Thermal power

Plant.NPTI C&I manual for Thermal power plant.CEGB Training ManualPower Plant Engineering – Black & Veatch1st EditionInstrument Engineer’s Handbook Volume 1& 2 – B.G

Liptak

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SRLPN Power Plant Measurement and Instrumentation

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