This document discusses instrumentation and control in power plants. It begins by introducing power plants and their objectives of being economically and environmentally friendly. It then discusses the classification and types of power plants, focusing on thermal power plants. It describes the key sub-cycles and quantities that must be measured in thermal power plants, including pressure, temperature, flow, and emissions. It outlines the measurement process and locations. Finally, it provides references on power plant engineering.

4.  INTRODUCTION OF POWER PLANT
 OBJECTIVE OF INSTRUMENTATION & CONTROL
 CLASSIFICATION OF POWER PLANTS
 THERMAL POWER PLANT
 SUB CYCLES OF THERMAL POWER PLANT
 QUANTITIES TO BE MEASURED
 MEASUREMENT POINT & VARIABLES
 MEASUREMENT PROCESS
 REFERENCES

5.  Power plant is assembly of systems or sub-
systems to generate electricity.
 Power plant must be useful economically &
environmental friendly to the society.
 Design of power plant incorporate two
important aspects:
(1)Selection of power generating equipments
should be such so that maximum of return will
result from minimum expenditure over the
working life of the plant.
(2)Operation should be such so as to provide
cheap, reliable & continuous service.

6.  This entire task is often taken up by control & instrumentation
or simply instrumentation system which has following
functions:
a) Measurement
b) Control
c) Operation
d) Monitoring
e) Protection

7.  For a plant Measurement system needs to be:
 Very accurate
 Reliable
 Delays should be as small as possible
 Should be switched on manually when a
overall control system fails

8.  Efficient Operation of the plant
 Economic Operation of the plant
 Safe operation of the plant
 Pollution control
GURUNANAK THERMAL POWER PLANT, BATHINDA(PUNJAB)

10.  A Generating station
which convert heat
energy into electrical
energy
 The Steam Power
Plant, Diesel Power
Plant, Gas Turbine
Power Plant& Nuclear
Power Plant are called
THERMAL POWER
PLANT.  Works on RANKINE
Cycle.

14.  WATER CYCLE -------- CONDENSATION, FEEDPUMP,
ECONOMIZER
 COMBUSTION CYCLE ---------- ECONOMIZER, BOILER, SUPER
HEATER
 STEAM CYCLE ------------------ BOILER, SUPER HEATER, TURBINE

15.  Pressure
 Temperature
 Flow
 Level
 Expansion/ Contraction
 Analysis of (1) Water (2) Steam (3) Flue
Gases
 And Others

16. Variables/ Measuring Points Types Of Sensors/ Approx. number
Parameters Instruments in the plant
(1) Pressure (a) Boiler Bourdon Tube,
(b) Turbine Diaphragm,
(c) Turbine Throttle Bellows 375-400
(d) Furnace Bell Gauges
(2) Tempera (a Steam at superheater Thermocouple
ture inlet & outlet
(b Feed Water at
economiser inlet
(c Water at condenser RTD 700-750
inlet
(d Air Preheater
(e Flue Gases Thermocouple

17.  Varies from vacuum as in furnace to 200 Mpa at the
main steamline.
 Pressure measuring devices are divided into two groups: (1) Liquid
Columns (2) Expansion Elements
 Liquid columns:
 Manometric type instruments
 Low range pressure measurement P =0
h
Patm
WELL TYPE MANOMETER

18.  These are not favoured in modern power plant
but are still used in older power plants.
 Expansion elements:
 Used in modern power plants
 Usually metallic & its movement indicates the
pressure
 Either directly coupled with mechanical linkages
or indirectly by an electrical transducer
connected to a read out device

19.  Expansion elements
Diaphragms Bellows Bourdon tube
 Diaphragms:
 Commonly corrugated diaphragms are used because
large deflection can be produced without nonlinearity
compared with flat type.
 In order to increase the deflection capabilities two or more
corrugated diaphragms are welded at the circumferences--
- Capsule element.

21.  Bellows
Manufactured from
Brass, Brass alloys,
Stainless steel.
Used for low pressure
measurement.
For high pressure
measurement bellows
are connected with
spring.

22.  Bourdon Tube
C shaped & made into an arc of
about 270
0
Material from which it made
depends upon the pressure
range of the device
Bourdon tubes are also used in
forms other than C type
 Spiral element: large
movement than C tube.
Helical element: produce
more or less circular movement
which is useful for driving a
recorder pen directly.

23.  Since power generation is a Thermodynamic
process so up to date knowledge of temperature of
the plant is most important.
 The efficiency of generation also depend on the
temperature measurement
T2 = Temp. inside the condenser
T1= Superheater temperature
 Temp. can be measured only by using indirect
methods.
1
2
1
T
T


24.  THERMOELECTRIC THERMOMETRY
 The actual value depend upon the material
used & on temperature difference between
the junctions.

25. TYPE METAL A METAL B TEMPERATU
RE RANGE
POINT TO
KNOW
T COPPER COPPER-
NICKEL
(CONSTANTAN)
400
0
C RESISTANT TO
CORROSION IN
MOST
ATMOSPHERE
J IRON COPPER-
NICKEL
(CONSTANTAN)
850
0
C NOT COMMONLY
USED BECAUSE
OF RUSTING &
EMBRITTLEMENT
E NICKEL-
CHROMIUM(C
HROME)
COPPER-
NICKEL
(CONSTANTAN)
700
0
C SUITABLE FOR
OXIDISING & INERT
ATMOSPHERE
K NICKEL-
CHROMIUM(C
HROME)
NICKEL-
ALUMINIUM
(ALUMEL)
1100
0
C MOST COMMONLY
USED

26. TYPE METAL A METAL B TEMPERATU
RE RANGE
POINT TO
KNOW
R PLATINUM13
%RHODIUM
PLATINUM 1400
0
C SUITABLE FOR
OXIDISING & INERT
ATMOSPHERE
S PLATINUM10
%RHODIUM
PLATINUM 1400
0
C SUITABLE FOR
OXIDISING & INERT
ATMOSPHERE,
CAN BE USED IN
VACUUM FOR
SHORT PERIOD
THERMISTOR ARE NOT USED IN THERMAL POWER PLANTS
BECAUSE ITS RANGE IS -60
0
TO 15
0

27.  RESISTANCE THERMOMETRY
 Suggested by Siemens in 1871- but not
satisfactory used for high temperature
 Today RTD is given by H.L.Calender in 1891
 PROPERTY-The resistance of the conductor
changes when its temperature is changed.
 Copper is occasionally used
 Platinum, nickel or nickel alloys are commonly
used
 Tungsten is used for high temperature
applications

28. METAL MIN. TEMP. MAX.TEMP. MELTING POINT
PLATINUM -260
0
C 110
0
C 1773
0
C
COPPER 0
0
C 180
0
C 1083
0
C
NICKEL -220
0
C 300
0
C 1435
0
C
TUNGSTEN -200
0
C 1000
0
C 3370
0
C

29.  A universal flow meter for all applications in
power station is not available.
 Infact there are more ways of measuring flow
than measuring pressure & temperature.
 Dual function meters usually measure flow rate
with linear output & minimum error.
 Vortex & Ultrasonic meters have become
available in recent years (1986) & their full
potential is not still fully developed.

31.  pH, DO,TURBIDITY & HYDRAZINE:
 Need to be checked for acidity (pH),
Dissolved oxygen(DO)
 Turbidity arising out of contamination by
suspended particles .
 Hydrazine which is added from outside to
the feed water but the excess should be
monitored.
 Oxygen reacts with thallium to form
thallium oxide which in aqueous solution
show good conductivity.

33.  Turbidity is measured at the outlet of the
condenser.
 Hydrazine is added to decrease dissolved
oxygen
Hydrazine nitrogen + water
 Its also makes water alkaline & prevent
acidic corrosion.
 Its is also toxic so its overuse can effect the
aquatic life.

34.  British Electricity International,Modern Power station
practice, control & instrumentation, vol F.
 A.K. Sawhney, “A course in Electrical & Electronic
measurements & instrumentation”, Danpat Rai &
CO.,seventeenth edition.
 D Patranabis, “Principles of Industrial
Instrumentation”,TMH, second edition.
 Frederick T. Morse, “ Power Plant Engineering”.
 “Power Plant Engineering”,
http://en.wikipedia.org/wiki/power plant engineering
 A.K. Raja, “Power plant Engineering”,New Age
International Publishers.

35.  Educational Technology Service Centre- IIT
KHARAGPUR; S. BANERJEE; EE Deptt.,
Energy resource & technology.
 V.K. Mehta, “Principles Of Power System”, S
Chand.