Thermal power stations require extensive instrumentation to monitor complex processes and ensure stable power generation. Instrumentation provides critical information to operators for starting up and shutting down processes safely. It also helps maintain the balance between heat input and electricity output by measuring deviations and enabling automatic controls and protections. The cost of instrumentation is high, around 7-12% of total costs, due to larger unit sizes, modernized equipment, and improved operator awareness of instrumentation benefits.

1. CONCEPT OF INSTRUMENTATION
IN
THERMAL POWER STATION
Prepared by :- Unknown

2. *Instruments should be independent for
their working
*The total instrumentation should be
interdependent to each other in assessing
the process conditions.
*Instrumentation should be sufficient to
provide adequate information to the
operators for

3. *Cold start of the unit
*Warm/hot start of the unit
*Shut down, both planned and
emergency shut down

4. Thermal Power Stations employ a
great number of equipment
performing number of complex
processes, the ultimate aim being the
conversion of chemical energy into
Electricity. In order to have stable
generating conditions, always a
balance is maintained that Heat input
= Electricity output + losses

5. But this balance is frequently
disturbed due to
*grid troubles external to the process
and machines,
* the troubles in the process itself
* the troubles in the equipment’s.
When the balance is disturbed, all
the process variables deviate from
their normal values.

6. Which calls for the following:
*Instruments: To measure and indicate the
amount of deviations.
*Automatic Control: To correct the deviation
and bring back to normalcy.
*Annunciation : To warn about the excessive
deviations if any.
*Protection: To isolate the equipment’s or
process from dangerous operating conditions
caused due to such excessive deviations.

7. The proportionate cost of instrumentation
during seventies was about 2.3 to 2.5% of the
total cost of boiler, turbine and their
Auxiliaries for the unit sizes up to 60/100
M.W.
This has become about 7% for 210 M.W.
and is reaching about 10-12% may even
higher in the near future for the same capacity
units.

8. increase in instrumentation cost is due to
*Increase in unit capacity, operating the unit at
higher parameter for economic reasons.
*New inventions, improvements, modernization
of instruments and equipment’s.
*Expected change in the duty cycles of the boiler
and turbine facilitating two-shift operation, quick
run up etc.
*Improved awareness among the personnel about
the utility of the instruments.

9. INDICATORS
*Local: indicators are self-contained and
self-operative and are mounted on the site.
*Remote: used for telemetering purposes
and mounted in the centralised control room
or control penal.
**The indicators both local and remote are
sometimes provided with signaling contacts
wherever required.

10. The remote indicators may be electrical,
electronics, and pneumatic or hydraulic based
for their operation and accordingly they are
named.
The indicators can be classified as analogue
or digital on the basis of final reading.
Indicators are available for single & multi point
measuring systems.

11. RECORDERS
*Recorders are necessary wherever the
operating history is required for analysing the
trends and for any future case studies or
efficiency purposes.
*single point or multipoint
Multipoint :multipoint continuous recorders
or multipoint dot recorders.
(dot recorders select the point one after the
other in sequence)

12. PRESENTATION OF INFORMATIONS
information measured and received from the
various parts of the plant/process are presented in
three categories.
*Vital information's
*becomes vital whenever some sections of the
plant start malfunctioning.
*information required occasionally to efficiency
engineers, which is given by recorders mounted on
back panels or local panels.

13. Vital informations
which is required by operators at all times
for the safe operation of the plant.
The information is presented through single
point indicators/recorders, placed on the front
panels.
Main steam pressure, temperature, condenser
level, vacuum, drum level, furnace pressure etc.
are some such parameters.

14. The second group of information is
generally not vital of the plant. But becomes
vital whenever some sections of the plant
start malfunctioning.
Such needs are met through multipoint
indicators/recorders placed in the front
panels.
Eg: Temperature and draft across the
flue gas path, bearing temperatures of the
motors fans etc.

15. The last group of information is not
required by the operators but for the
occasional need of the efficiency engineers.
These information’s are given by
recorders mounted on back panels or local
panels.
Eg: D.M. make up quantity, fuel oil
flow quantities etc.

16. CODING OF INSTRUMENTS
In order to distinguish the parameters
required from the other instantly, a shape
coding of instrument face is being adopted.
A general approach could be as below:
Level instruments - Horizontal edgewise
Temperature inst - Horizontal edgewise
Pressure inst - Circular

17. ARRANGEMENT OF INSTRUMENTS
*Master Panel’ arrangement: In this
arrangement, instruments measuring important
parameters are provided in one panel.
*All instruments in this panel will be of circular
shape with normal rated value marked at 12o’clock
position.
* This will help the operators to quickly notice
any deviation from the rated values.

18. SELECTION OF INSTRUMENTS
*Instrument engineers are required to work in
close association with the system design as well as
equipment design engineers in selecting
instruments and sensing systems.
*The instrument and system design engineers
decide the location for the measurement of various
parameters such as level, pressure, flow,
differential pressure, temperature etc. based on
the system design and layout conditions.

19. factors influences to select the appropriate
instruments:
*Range of measurement
*Required accuracy of measurement
*The form of final data display required
*Process media
*Cost
*Calibration & repair facilities available
*Layout restrictions
*Maintenance requirements/availability
*availability of skill persons.

20. TEMPERATURE MEASURIINSTRUMENTS
* Accurate measurement of temperature is required to
assess the material fatigue, heat balance, heat transfer etc.
* The measurement ranges from ambient
temperature viz. air at inlet of FD fan to 1300oC to
1400oC inside the furnace zone.
* Temperature measurement is to be made for
water /steam, oil (fuel oil and lubricating oil), air,
flue gases, hydrogen gas, bearing babbit metal,
turbine casing, generator winding and cores, S.H.
tube metal etc.

21. *Filled system thermometry such as mercury in glass,
mercury in steel, vapour filled, or bimetallic thermometers
used for local indication of temperature.
*The selection of thermometer depends upon the range of
the temperature to be measured.
*These instruments are available with electrical contacts
for setting up annunciation and protection system wherever
required.
*Resistance thermometers made up of platinum, copper
resistance type, secondary instruments used in conjunction
are cross coil indicators or electronic bridges.

22. *Resistance thermometers are generally used up to 250oC.
*Above 250oC, thermocouples are used as primary
sensors.
*The secondary instruments for thermocouple sensors are
pyrometric millivolt meters or electronic potentiometers.
*Null balance electronic bridges are used for the very
accurate measurement of millivolts from thermocouples ,
either as indicators, or indicator cum recorders with
alarm /protection contacts and with remote transmission
facilities.

23. PRESSURE MEASURING INSTRUMENTS
*The pressure measurement in Thermal Power
Station ranges from less than atmospheric at
condenser to hydraulic test pressure of boiler.
*Pressure of steam/water, lubricating oil, fuel oil,
air flue gases, hydrogen etc are measured.
*For local indication of pressure and differential
pressure, bourdon tube and diaphragm type gauges
or liquid manometers & for remote measurement
transmitter, either/electric/electronic or pneumatic
coupled with a secondary instrument are used.

24. Transmitters
*mechanical movement of sensing elements such
as bourdon, bellows, diaphragm etc. are employed.
*pressure causes an displacement/movement in the
sensor which causes pneumatic or electrical out put
.
*which is measured by the secondary
instruments,such as indicators or recorders. Some
may incorporate signaling contacts.

25. LEVEL MEASUREMENT
*is generally carried out as differential pressure
measurement.
*level measurement in open tanks such as
D.M.water storage and fuel oil and lube oil tanks
and in closed tanks such as deaerator, condenser
hot well, boiler drum, L.P. & H.P. heaters etc.are
made.
*Gauge glasses and floats are used for local
indication and the transmitters with the secondary
instruments for remote level measurements.

26. *boiler drum poses many problems because of varying
pressures and temperatures, which continuously change
the density of media calls for corrections to be made in
order to get correct levels.
* ‘Hydrastep’ improves the accuracy and reliability of the
drum level measurement.
* The nucleonic level gauges or the capacitance and
resistance type sensors serve for continuous level
measurement of the raw/pulverised coalbunkers and dust
collectors’ hoppers.

27. FLOW MEASUREMENT
*Flow measurements of solids, liquids and gases
are required in Thermal Power Stations for
carrying out safe and optimum operation.
*liquid flow measurements can be made within
reasonable accuracy.
*steam flow measurement requires density
correction under varying pressures.
*The air and flue gas flow measurements suffer
accuracy and reliability due to variation in
pressure, temperature, duct leakage, dust
accumulation etc.

28. *flow measurements are based on inferential
principles carried out by placing suitable throttling
devices in the flow path of the fluids ie
pipes/ducts..
*The throttling devices are suitably selected
depending upon the media, flow quantity etc.
among orifice, venturi, flow nozzle, dall tube etc.
*The differential pressure developed across such
sensing devices is proportional to the square of the
flow quantity.

29. ANALYTICAL INSTRUMENTS
Feed water quality assessed by conductivity,
pH, dissolved oxygen, and sodium parameters,
steam quality by conductivity, silica and pH
analysers.
The combustion quality is assessed by the percentage
of oxygen, carbon monoxide or carbon dioxide in the flue
gases.
The purity of hydrogen inside the generator housing is
measured by utilising the thermal conducting capacity of
the hydrogen gas.

30. *The water and steam purity is measured as the
electrolytic conductivity by electronic bridge
method & conductivity cell dipped into the
medium.
*The percentage volume of oxygen in combustion
gases is measured by utilising the paramagnetic
properties of oxygen,& the carbon monoxide
percentage by the ‘Absorption of Electromagnetic
radiation’ principle
*Recent developments are on line ‘in situ’
instruments for these two parameters where the
problem of sampling is dispensed with.

31. TURBOVISORY INSTRUMENTS
The turbovisory instruments have become very
important for modern day turbines where the materials
have been stressed nearer to the yield points and the
internal clearances have become minimum.
Shaft eccentricity, vibration (both shaft and bearing
pedestal), differential expansion of shaft and cylinders,
over all thermalexpansion of the cylinder, speed, & axial
shift etc. are some of the turbovisory measurements. all
These measurements are interrelated and interdependent.

32. Temperature measurement locations
*Steam temperature at boiler outlet, super heater stages,
steam legs before ESVS, IVs, and -H.P. cylinder outlet,
hot reheat and exhaust hood temperatures.
*Temperature of condensate/feed water along the flow
path from condenser
* Metal temperature of turbine casing ,super-heaters and
reheaters .
*indicators/indicator-cum-recorders with alarm and
protection facilities in control room&with multi-point
selection as per requirement.

33. *Flue gas temperature in various zones of boiler-indicator
and indicator cum recorder in control
room.
*Air temperature at inlet and outlet of air
preheater.
*Turbine bearing oil drain temperature-indicator
cum recorder in U.C.B.
*Generator winding and core temperature-indicator
cum recorders in control room.
*Temperature of auxiliary equipment bearings such as
mill ID, FD and PA fans etc. indicator cum recorder in
U.C.B.

34. PRESSURE MEASURING LOCATIONS
Condensate pressure after condensate pumps and before
the ejectors, - indicator in U.C.B.
Deaerator pressure - indicator cum recorder in U.C.B.
with electrical contacts for interlocking facilities.
Feed water pressure after feed pumps – individual
indicators for each pump.
Feed water pressure before and after feed regulating
stations-indicators in U.C.B.
Drum pressure-indicator cum recorders in U.C.B. with
alarm signaling

35. *Super-heater steam pressure at boiler outlet 2 Nos.
indicators one for each side in U.C.B. and at local with
alarm protection facilities. Measurement is done at the
outlet of superheater and before stop valves.
*Steam pressure-1 No. indicator cum recorder in one
of the lines before turbine stop valve in U.C.B.
*Steam pressure at emergency stop valves and IVs.
*Steam pressure after control valves indicators in
local panel for each valve.
*Steam pressure at Curtis wheel-indicator cum
recorder in U.C.B. with alarm contacts.

36. *Steam pressure of H.P. turbine exhaust indicator in
U.C.B. for cold reheat steam.
*Vacuum in condenser indicator cum recorder in
U.C.B. with alarm facilities and separate vacuum relay for
protection.
*Hot reheat pressure indicator in U.C.B with signaling
contacts.
*Steam pressure at the exhaust of I.P. cylinder-indicators
in local panel.
*Heavy oil pressure-indicators in U.C.B. with
signaling contacts. Measurement is made before and after
pressure regulating valves.

37. *Light warm up oil pressure Measurement is made
before and after the flow control valves.indicators in U.C.B
with signaling contacts.
*Igniter oil pressure-indicator in U.C.B.
*Governing oil pressure-indicator in U.C.B. with
signaling contacts.
*Lubricating oil pressure Measurement is made after
oil coolers -indicator in U.C.B..
*Air pressure-indicators in U.C.B. for secondary air,
primary air measured before and after air heaters.
*Wind box pressure indicators in U.C.B.

38. *Furnace draft-indicators and recorders in
U.C.B. (Measurement is made averaging left
and right side drafts).
*Flue gas draft before and after economiser-indicators
in U.C.B.
*Draft after air-heaters indicators in U.C.B.
*ID fan suction-indicators in U.C..B

39. LEVEL MEASUREMENT
*Drum level-indicators and indicators cum
recorders (total 3 Nos. from different tapping) in
U.C.B. with alarm and protection facilities.
*Local gauge glass
*Remote indirect measurement
*Drip level in H.P. and LP heaters-indicators in
U.C.B. with alarm and protection facilities.

40. *Condensate level in condenser-indicator in
U.C.B with alarm facilities.
*Deaerator level-indicator in U.C.B. with
signaling contacts for alarm and protection.
*The various storage tank levels such as D.M.
water, fuel oil, lubricating oil etc. are measured by
local direct gauge glasses.

41. FLOW
*Condensate flow to deaerator-indicator/recorder in
U.C.B. with integrator unit for totalizing in two locations
(i) between air ejectors and L.P. heater
(ii) between the final L.P heater and deaerator.
*Feed water flow indicator/recorder in U.C.B. with
integrator unit. Measurement is made between final H.P.
heater and feed regulating valves.
*Super heated steam flow 2 Nos. indicators cum recorders
one for each pipe with integrator unit in U.C.B.
*Re-heater steam flow-2 Nos. indicators cum recorders
one for each side of the boiler. Measurement is made at
the inlet to reheater.

42. *Air flow-2 Nos. indicator cum recorders one for
each FD fan in U.C.B. Measurement is made at
the discharge of the FD fans.
*The fuel oil flow to the unit is given by two
indicators cum recorders in U.C.B. one measuring
the oil in the incoming line and the other in the
return line.
Normally the coal flow is measured for the whole
station by the belt conveyor weighers.

43. AUTOMATIC COTNROL
Boiler control loops :
*Steam pressure always called as Boiler Master
Control.
*Combustion control
*Furnace draft control
*Boiler feed regulation or drum level control
*Super heater/reheater steam temperature control
*Auxiliary steam pressure control
*Mill group control
*Feed pump speed control.

44. TURBINE AUTOMATICS
*Condenser hot well level regulation
*Drip level control in L.P. and H.P. heater
*AUTOMATIC TURBINE RUN UP

45. BURNER MANAGEMENT
*For higher capacity boilers, fuel-firing rate is also
higher. Explosion can occur within 1 to 2 sec’s of fuel
accumulation.
*AS human reflexes are slower. A complete
automatic burner management system called furnace
safeguard supervisory system (FSSS in short) has been
introduced to manage the present day boilers.
*This system takes care that every increment of fuel
input corresponds to the available ignition energy inside
the furnace.

46. The following are functions of automatic burner
management system.
*Furnace purge supervision
*Igniter control
*Warm up oil control
*Pulverizer control
*Secondary air damper control
*Boiler trip protection
*And also condition of the plant whether the cold
or hot start

47. A process can be defined as a series of
manufacturing stages. Which could be either
mechanical, electrical, physical or chemical or
combination of all these, that the feed material
would have to undergo to be transformed in to
desired products

48. Flow, pressure, level, temperature, and similar
quantities are called parameter of the process
variables.

49. The separation between the minimums
maximum values of measurement is called the
range and the difference between lower and
upper range values is the measurement span

50. A control loop in general comprises
a measuring device, a controller having the
desired value (set point) that can be set by the
process operator, and controlled devices.
However when the set point of one
controller is set by another controller or a
computer it is termed as remote set point, some
times also called the cascade set point, such a
combination is called a cascade loop

51. A controller must include; a measuring unit, a
set point and a comparator to determine the
difference between set point and measurement
to generate the error. A control unit that
operates on the error and produces an out put
and an out put unit to drive the correcting
device. A controller always responding with
an action that will tend to bring the
measurement and desired value to
coincidence

52. The controller has two operating modes, auto
and manual. In manual the controlled out put
is by passed and the control device is driven
directly by the operator

53. A mimic or process graphic is pictorial
representation of the process. It can be static
showing picture only or dynamic when
includes live process parameter data.

54. A distributed control system (DCs) is a
micro processor based control system with
centralized hard wired inputs and outputs that
are soft ware connected and configured to
provide control and computation.
To communicate with the system and the
process a DCs is always provided with visual
display (VDU) unit + a computer key board
and printer

55. Instrumentation
Instrument : a thing used in performing an
action
Instrumentation: provision of use of mechanical
instruments to perform different tasks in industry.
Such as :measurement,control,
protection,etc.

56. measurement: is a comparison
between known standard to un- known
magnitude.

57. EVOLUTION OF MEASUREMENT
TECHNOLOGY & AUTOMATION:

58. The ability of logical reasoning and quest to
understand the nature led to the development of
tools & techniques by the humans ,application of
them, analyzing the results ,paving the way for
constant development in all round the measurement
techniques.
Economic constraints coupled with product
improvement ,is calling for increased
sophistication in measurement &control
techniques.

59. A Process of Manufacturing Any Product Is
Comprises of Series of Manufacturing Stages
Which Could Be Either Mechanical,physical,
Chemical, Electrical or Combination of All
or Any of These.
Flow,pressure,level,temperature,ph Etc Are
Called Parameters of the Process Variables.

60. Energy can nether be created
nor destroyed
merely converted.
Energy available in fuel = 100%

61. During conversion:
90% is given to steam.
(10% is lost to stack, unburned fuel etc.)
from 90%:
50% is lost to condenser.
Conversion efficiency of a TPS=35.8%.
This or above conversion efficiency will be
possible only when assistance of proper
instrumentation is available.

62. Efficiency's of :
turbine :85% 15% loss
alternator :98.5% 1.5%loss
gen.transformer:95% 5% loss

63. Instrumentation in whole is used to
improve /increase:
* safety of plant and personnel.
* availability of plant
* efficiency of plant and equipment.
* efficient use of process variables.
* to alert the operator/engineer facilitating
them to take timely corrective actions.

64. the economic reasons forced the
developments in the technology
enabling the realization of larger
plant sizes.
But the larger plant increased the
complexity of control and this in
turn increased the need for better
and faster measurements,to
increase the availability & reliability
of the plant.

65. Indian thermal power plants
Unit capacity Pr kg/cm2 Temp 0c
30 Mw 59.8 482
50-62.5 90.0 510-535
80-100 90.0 535 mostly
non-reheat
110-140 130 535-535 rh typ
210 150 535-535 ,,
500 178 ,,

66. The evolution of Industrial Measurement
Technology seen from +1-2% accuracy
transmitter to +0.2% accuracy.
earlier transmitters are based on
dominant transducer technology.

67. There are two types of advances taking
place in the Instrumentation area.
* the traditional sensors like
thermocouples, RTDs etc are being
made more and more intelligent.
* new sensors with better accuracy and
noise immunity are being invented.

68. Development
1930s The discrete devices used for analog
control were governors and mechanical
controllers.
1940s direct connected pneumatic controllers
50s transmitter type of pneumatic controllers
50s. discrete devices used for digital control
were relays and stepping switches

69. Development
• Pneumatic
• Electrical
• Electro-pneumatic
• Electronics
• μp based
• Computer based (DDCs.)

71. Transmission lag

76. replacement of relays and pneumatic
controllers with their solid state equivalents,
resulted in the development PLCs & PID
controllers.
Realization of computer capabilities
first led to Data Acquisition, then to
Supervisory control and finally to Direct
Digital-Control.
With continued developments in technology,
these two streams have now merged into the
present day computer based control
systems(distributed digital control).

77. Signals
Pneumatic : 3 - 15 psi or 0.2 - 1.0 Kg/cm2
electrical : 4 - 20 ma (normally)
1 - 5 v
optical signals with fiber optic systems/when
a direct line of sight exists.

78. Advantages of pneumatic system
• Simple ,hence less skilled person can be utilised for
servicing,Less expensive on initial cost.
• Reliable and more rugged components are available.
• Higher motive force actuator is readily available.
• Flame proof, suitable for hazardous surroundings.
• Operation is smooth,over load proof due to
compressibility.
• Requires large quantity of clean compressed
air(moisture&dirt free).
• Permits wider ambient temperature operations.

79. Advantages of electronic system
• High speed of signal transmission,hence less
time lag.
• Higher amplification is possible
• easily adaptable to complex & integrated control
• greater accuracy
• feed back from more number of variables
• cheaper if the system is adapted for large plants.

80. -First supplied range of instrumentation
• Technical collaboration of USSR
• instrumentation was mostly voltage based,&
controllers were electronic pulse type.
• Transmitters employed LVDT,1-0-1v AC signal
limitations of above
instrumentation
• they are bulky
• DPTs range above 6.3 kg/cm2 were not available
• range adjustment was not possible at site
• compensation for pressure & temp. was not
possible

81. Controllers suffered from
• Feed forward signals/actions not possible
• fuel-air ratio and lead-lag features could not
be provided in combustion control.
• Biasing facility not available
• auto run - back feature was not available.

82. transducers
• Voltage base - /four wire transducers.
(o/p:1-5,0-5,0-10 v)
• Current base - two wire transmitters
(o/p:4-20,0-20,0-50 ma)
• pneumatic - o/p: 0.2-1kg/cm2 /
0.2-1.0 bar/
3 - 15 psi/

83. Live zero
dead zero

84. Measurement cycle
sensing transmitting Indicating /&
Recording
/&controlling.

85. sensing
• Sensors:
Pr : diaphragm, level: manometers,
capsule, float mechanisms
bourdon tube, head pressure,
temp: thermometers resistance etc.
thermocouples,
flow : primary elements,
mechanical meters.

86. Transmitting stage
• Signal conditioning suitable to next stage,
• i.e.: amplifying,
• converting,
• attenuating, etc.

87. Final stage
• Indicating
• Indicating & annunciation,/ protection.
• Indicating & recording
• recording & annunciation,/protection.
• Indicating/& controlling.
• Controlling.

88. Variables in electrical technology
• Resis tance,
• capaci tance,
• induc tance,
• reluc tance,
• conduc tance,
• reac tance, &
• impedence in signal condition circuits.

89. Developments in Indicators & Recorders
• Gravity control replaced with controlling torque
techniques in indicators.
• Miniaturization to present more information to
operator in a reachable distance,for controlling a
system.(modular & panel arrangement).
• Edge wise indicators (to accommodate more no.of
instruments in a given place).
• Digital indicators for easy reading.
• Multi-pen recorders,(continuos & dot metric
recorders)
• multiple functions in rec. & indicators .

90. Primary measuring element
selection&characteristics.
• The intended use of the sensor.
• Range: normal range over which the controlled
variable might vary?.are there extremes to this.?
• Response time: time required for a sensor to
respond,to a change in its input.
• Accuracy: how close the sensor comes to
indicating the actual value of the measured value.
• Sensitivity: how small change in the controlled
variable the sensor can measure.

91. Precision: how consistent the sensor is in measuring the
same value under the same operating conditions over a
period of time.
Dead band: how much of a change to the process is
required before the sensor responds to the change?
Costs: what are the costs involved.
(i.e. Purchase cost,installation cost, operating cost,and
calibrating etc.)
installation problems: special installations
( i.e.corrosive fluids,explosive mixtures,size and shape
constraints,remote transmission requirements etc.)

92. Transducer requirements
• Should sense the desired input signal.
• Should be insensitive to other signals present
simultaneously in the measurand.
• Should be amenable to modifications with
appropriate processing and display devices.
• It should not alter the event to be measured.
• Should be able to with stand hostile environment
while maintaining the rated accuracy.
• Should be easily available and reasonably priced.

93. Accuracy
• 1. Percentage of true value: =
measured value-true value X 100
true value
• percentage of full scale deflection : =
measured value-true value X 100
maximum scale value
* F.S.D. is less accurate than % of true value.