8/8/2019 voc trg2-02.10.09

1/45

CONTROL & INSTRUMENTATION

AT

NTPC SINGRAULI

(A VOCATIONAL TRAINING REPORT)

UNDER GUIDENCE OF:-

MR A.R.MAITI

DGM (C&I)

SUBMITTED BY:-

MANISH KUMAR SINGH

A.I.E.T LUCKNOW

1

8/8/2019 voc trg2-02.10.09

2/45

SINGRUALI SUPER THERMAL POWER STATION, NTPC

Shaktinagar, Sonbhadra (distt.) U.P.

2

8/8/2019 voc trg2-02.10.09

3/45

PREFACEPREFACE

In todays world, electricity has an important role to play. People,

today, rely on electricity for the fulfillment of even his basic needs for

comfortable living.

Electricity contributes the largest share to a countrys economic

growth. It is the most powerful resource and has brought industrial

revolution worldwide. It has resulted in social changes too and raised the

standard of living.

In India, several organizations like NHPC, UPSEB, and other state

electricity boards etc. are engaged in electricity generation. NTPC is the

largest among these with an honourable contribution of 28.6 % of Indias

total generated power.

3

8/8/2019 voc trg2-02.10.09

4/45

ACKNOWLEDGEMENTACKNOWLEDGEMENT

I oblige to acknowledge my heartiest gratitude to all honourable peoplewho helped me during my vocational training at NTPC Singrauli, Shaktinagar. .

I would like to thank Mr.N.N.SINHA, Sr. Manager, Training Centre, for

granting me the permission for doing my summer vocational training at this

project.

I am also thankful to Mr.NISHITH AGARWAL, Supdt.(C&I) and

Mr.A.K.ANAND, Dy.Supdt.(C&I) for providing the necessary guidance and

training about the Turbine area. I would like to thanks Miss.SADHAVI

SRIVASTAVA, Assistant Engineer (C&I) for giving their valuable guidance

during my training period in the lab area of the control and instrumentation

department.

I would like to thank Mr.ARVIND BHARTI, Dy. Supdt.(C&I) for

providing me the knowledge about the work in the DAS(Data Acquisition

System). I would also thank Mr.J.GHOSH, Dy.Supdt.(C&I) for encouraging and

providing the necessary details in the boiler maintenance. I am also grateful to all

SSTPS staff that helped me directly or indirectly.

I would co-heartedly thank ABU HINA SIDDAQUI, Placement Officer, T& P Cell, and Mr.S.K MISHRA, HOD(Electronics & Communication Engg.),

A.I.E.T Lucknow for allowing me to do my training at this place.

MANISH KUMAR SINGH

B. Tech. (2007 Batch)

Roll No.-0705330038

Electronics & Communication Engg.

A.I.E.T LUCKNOW.

4

8/8/2019 voc trg2-02.10.09

5/45

TABLE OF CONTENTSTABLE OF CONTENTS

1. INTRODUCTION

NTPC

NTPC SINGRAULI

THERMAL POWER PLANT

2. PRINCIPLE OF OPERATION

3. BOILER & AUXILLIARIES

4. TURBINE & AUXILLIARIES

5. GENERATOR & AUXILLIARIES6. DATA ACQUISITION SYSTEM

7. ELECTROSTATIC PRECIPITATOR

8. AN OVRVIEW OF S.S.T.P.S.

11.. INTRODUCTIONINTRODUCTION

5

8/8/2019 voc trg2-02.10.09

6/45

NTPC LIMITED.NTPC LIMITED.

NTPC LTD.(A Govt. of India Enterprise)NTPC LTD.(A Govt. of India Enterprise ) has been the power behind

Indias sustainable power development since November 1975. It is an ISO

9001:2000 certified company.

NTPC was ranked number ONE in the category the Best Workplace for

large organization and number EIGHT overall for the year 2008 by Great Places

to Work Institutes India chapter in collaboration with Economics Times.

The total installed capacity of NTPC, as on 31st Mar2009, is 30,144 MW

(including 2294 MW from Joint Ventures).

With ambitious growth plan to become a 50,000 MW plus company by

2012 and 75,000 MW plus company by 2017, NTPC the largest power utilityhas already diversified into Hydro (Power) Sector, Coal Mines development and

Exploration & Production of Petroleum.

The Vision of NTPC is:

A world class integrated power major, powering Indias growth with

increasing global presence.

And the Core Values of NTPC are:

Business Ethics Customer Focus

Organizational & Professional Pride

Mutual Respect and Trust

Innovation & Speed

Total Quality for Excellence

The above figure shows how NTPC contributed in the vital power requirements of

the country.

Share of NTPC in Indias TotalInstalled capacity as on 31.03.2009

NTPC27850 MW, 18.79%

ALL INDIA148215 MW

NTPC

ALL INDIA

NTPC's contribution in India's

Total Power Generation

NTPC,

28.60%

ALLINDIA,71.40%

NTPC

ALL INDIA

6

8/8/2019 voc trg2-02.10.09

7/45

NTPC SINGRAULI

(SINGRAULI SUPER THERMAL POWER STATION)

NTPC Singrauli is a coal based Thermal Power Station. It is situated in district of

at. It is a mother plant and hence a flagship Power Station of NTPC.

The detailed description ofNTPC Singrauli is as follows:

Capacity : 2000 MW (5*200 + 2*500)

Location : Shaktinagar, Sonbhadra, Uttar Pradesh.

Energy Source : Jayant & Bina Coal Mines of NCL

Water Source : Rehand Dam Reservoir (also known as Govind

Ballabh Pant Sagar)

Beneficiaries : U.P., Uttaranchal, J&K, H.P., Chandigarh,

Rajasthan, Haryana, Punjab, Delhi

THERMAL POWER STATION

Everybody must be having a thought that a thermal power plant is a place

where electricity is produced. But do you know how it is produced?

The chemical energy stored is converted to heat energy which forms the

input of power plant and electrical energy produced by the generator is the output.

Power is the single most important necessity for the common people and

industrial development of a nation. In a convectional power plant the energy is

first converted to a mechanical work and then is converted to electrical energy.

Thus the energy conversions involved are:

The first energy conversion takes in what is called a Boiler or Steam

Generator, the second in a Turbine and the last conversion takes place in the

Generator.

PRINCIPLEPRINCIPLE OF OPERATIONOF OPERATION

7

8/8/2019 voc trg2-02.10.09

8/45

For each process in a vapour power cycle, it is possible to assume a hypothetical

or ideal process which represents the basic intended operation and do not produce

any extraneous effect like heat loss.

1. For steam boiler, this would be a reversible constant pressure heating

process of water to form steam.

2. For turbine, the ideal process would be a reversible adiabatic expansion of

steam.3. For condenser, it would be a reversible constant pressure heat rejection as

the steam condenser till it becomes saturated liquid.

4. For pump, the ideal process would be the reversible adiabatic compression

of liquid ending at the initial pressure.

When all the above four cycles are combined, the cycle achieved is called

RANKINE CYCLE. Hence the working of a thermal power plant is based upon

Rankine cycle with some modification.

A PULVERIZED COAL FUELED POWERA PULVERIZED COAL FUELED POWER

PLANTPLANT8

8/8/2019 voc trg2-02.10.09

9/45

A typical pulverized coal fueled power plant is based on Rankine Thermodynamic

cycle. A Rankine cycle is a vapour cycle that relies on the isentropic expansion

of high pressure gas to produce work. Let us see a superheat Rankine cycle:

Fig: Super Heat Rankine cycle

9

8/8/2019 voc trg2-02.10.09

10/45

Fig: Energy conversion flow diagram.

The basic understanding of the modern thermal power station in terms of major

systems involved can be done under three basic heads viz. generating steam from

coal, conversion of thermal energy to mechanical power and generation & load

dispatch of electric power.

1. Coal to Steam:

The coal is burnt at the rate up to 282 tonnes per hour (500 MW Unit).

From track hopper,coal is carried on conveyor belts to bunkers. It then falls in to coal pulverizing mill, where it is grounded into

powder as fine as flour.

Primary air Air is drawn in to the pulverizing mill where it is mixed

with powdered coal.

The mixture is then carried to the furnace where it mixes with rest of

the air and burns to great heat.

This heats circulating water and produces steam, which passes to steam

drum at very high pressure.

The steam is then heated further in the Superheater and fed to highpressure cylinder of steam turbine.

The steam is then passed to other cylinders of turbine through reheater.

The spent steam is sent to condenser, where it turns back to water called

condensate.

Condensate is sent to lower part of steam drum through feed heater and

economizer.

The flue gases leaving boiler are used for heating purpose in feed

heater, economizer, and air Preheater.

The flue gases are then passed to electro-static precipitator and then,through draught fan, to chimney.

2. Steam to Mechanical Power:

Steam first enters the high pressure cylinder of turbine where it passes

over a ring of stationary/fixed blades which acts as nozzle and directs

steam onto a ring of moving blades.

10

8/8/2019 voc trg2-02.10.09

11/45

Steam passes to the other cylinders through reheater and the process is

repeated again and again.

This rotates the turbine shaft up to 3000 rpm.

At each stage, steam expands, pressure decreases and velocity

increases.

3. Mechanical to Electrical Power:

The shaft is connected to an alternators armature.

Thus the armature is rotated and electric current is produced in the

stators windings.

The generated electricity is of order 25,000 volts.

4. Switching and Transmission:

Electricity generated is fed to one side of generators transformer and

stepped up to 132000, 220000, or 400000 volts. It is then passed to a series of three switches an isolator, a circuit

breaker, and another isolator.

From circuit breaker, current is taken to bus bars and then to another

circuit breaker with its associated isolator before being fed to the main

Grid.

Each generator has its own switching and transmission arrangement.

Three-phase system is used for power transmission.

5. Control and instrumentation

Control and Instrumentation (C & I) systems are provided to enable the

power station to be operated in a safe and efficient manner while responding to

the demands of the national grid system. These demands have to be met without

violating the safety or operational constraints of the plants. For example,

metallurgical limitations are important as they set limits on the maximum

permissible boiler metal temperature and the chemical constituents of the Feed

water.

The control and Instrumentation system provides the means of the manual

and automatic control of plant operating conditions to:

Maintain an adequate margin from the safety and operational

constraints.

Monitor these margins and the plant conditions, and provide immediate

indications and permanent records.

Draw the attention of the operator by an alarm system to any

unacceptable reduction in the margins.

Shut down the plant if the operating constraints are violated.

11

8/8/2019 voc trg2-02.10.09

12/45

TYPESOF INSTRUMENTS :

The different types of instruments normally used are given below:

Indicators These are of two categories, namely local and remote.

Local indicators are self-contained and self-operative and are mounted on

the site. The Remote indicators are used for telemeter purposes and

mounted in the centralized control room or control panel. The indicators

are sometimes provided with signaling contacts wherever required. The

Remote indicators depend on electricity, electronics and pneumatic or

hydraulic system for their operation and accordingly they are named. The

indicator can be classified as analogue or digital on the basis of final

display of the reading.

Recorders These are necessary wherever the operating history is

required for analyzing the trends and for any future case studies orefficiency purposes. Recorders can be of single point measuring a single

parameter or multipoint measuring a number of parameters by single

instruments. Multipoint recorders are again categorized as multipoint

continuous or multipoint dot recorders. The multipoint dot recorders select

the point one after the other in a sequence where as the continuous

recorders measure simultaneously all the points.

12

8/8/2019 voc trg2-02.10.09

13/45

BOILERBOILER

DEFINITION:

Boiler is defined as a device that is used to transfer heat energy being

produced by burning of fuel to liquid, generally water, contended in it to cause its

vaporization. Boiler is called Steam Generator.

The following are factors essential for the efficient combustion usually

referred as The three Ts.

a) Time It will take a definite time to heat the fuel to its ignitiontemperature and having ignited, it will also take time to burn.

b) Temperature A fuel will not burn until it reaches its ignition

temperature.c) Turbulence Turbulence is introduced to achieve a rapid relative

motion between the air and fuel particles.SPECIFICATIONS:

Following are the specifications of the main boiler used at Singrauli Super

Thermal Power Station for 500 MW Unit:

1. Main Boiler

Type: Forced circulation, Dry bottom,

Tangentially fired, balanced draft, Radiant

Reheat type with direct fired pulverized

coal system.

Manufacturer: BHEL

Designed fuel: Indian Bituminous coal

Furnace type: Fusion welded

Drum:

Material ~~ Carbon Steel SA299

Overall length ~~ 22.07 mtrs.

Designed pressure ~~ 205 Kg/cm2

13

8/8/2019 voc trg2-02.10.09

14/45

WATER & STEAM CIRCULATION

fig. Flow diagram of water & steam circulation

14

8/8/2019 voc trg2-02.10.09

15/45

STEAM TURBINESTEAM TURBINE

At Singrauli Station, 500 MW capacity turbines are of Kraft Werk Union

(KWU - Germany) design and supplied by BHEL. The turbine is condensing,

tandem compounded, horizontal, reheat type, single shaft machine. It has got

separate high pressure, intermediate and low pressure parts. The HP part is acylinder and IP & LP parts are double flow cylinders. The turbine rotor is rigidly

coupled with each other and with generator rotor.

In the 500 MW KWU turbines, single oil is used for lubrication of

bearings, control oil for governing and hydraulic turbine turning gear. During

start-ups, auxiliary oil pump (2 Nos.) supplies the control oil. Once the speed of

the turbine crosses 90% of the rated speed, the main oil pump takes over.

SPECIFICATIONS

Type: The cylindrical reheat condensing turbine having:

Single flow HP turbine with 18 stages.

Double flow IP turbine with 14 stages per flow.

Double flow LP turbine with 6 stages per flow.

Rated Parameters

Nominal rating : 500 MW

Peak loading (without HP heaters): : 536.7 MW

Rated speed : 3000 rpm

Main steam flow at full load

(with HP heater in service) : 1530 tons per hour

Main steam pressure /temperature

at full load ~~ : 170 kg/cm2 ,537 C.

Condenser pressure ~~ : 76 mm Hg

CW inlet temperature : 28 C.

15

8/8/2019 voc trg2-02.10.09

16/45

TURBINE GOVERING SYSTEM

In order to maintain the synchronous speed under changing load/grid orsteam conditions, it is equipped with electro-hydraulic governor; fully backed-up

by a hydraulic governor. The measuring and processing of electrical signal offer

the advantages such as flexibility, dynamic stability and simple representation of

complicated functional systems. The integration of electrical and hydraulic system

is an excellent combination with following advantages:

Exact load frequency drop with high sensitivity.

Avoids over speeding of turbine during load throw offs.

Adjustments of drop in fine steps, even during on load operation.

TURBINE PROTECTION SYSTEM

Turbine protection system performs to cover the following functions:-

a. Protection of turbine from inadmissible operating conditions.

b. In case of plant failure, protection against subsequent damages.

c. It restricts occurring failures to minimum.

Standard turbine protection system comprises the following:-

Mechanical / hydraulic turbine protection.

Electrical turbine protections.

H.P. - L.P. BY- PASS SYSTEM

The HP By-pass system in coordination with LP By-pass enables boiler

operation and loading independent of the turbine. For matching the live steam and

metal temperature for a quick startup, by-pass stations have been provided, which

dumps the steam to the condenser through pressure reducing station and

desuperheaters, during the period the steam parameters at the boiler are being

raised. This allows quick rising of parameters to a level acceptable to the turbinefor rolling during startup. It helps in quick start of turbine and low noise level,

also economizes the consumption of DM water. Losses of steam into the

atmosphere are cut down to the barest minimum. By-pass system enables to

shorten the start-up time.

16

8/8/2019 voc trg2-02.10.09

17/45

TURBINE STRESS EVALUATOR

IntroductionDuring start up, load changes and shut down, the internals of the turbine are

subjected to temperature fluctuations, resulting in thermal stresses.These stresses

cause material fatigue on the turbine components. The main task of the TSE isOn-line monitoring and evaluation of turbine components in respect of their

material fatigue and life expectancy.

Functions of the TSE

It compares thermal stresses in monitored components with reference

variables.

TSE influences set point of the turbine speed and load controller.

Provides three mode- fast, normal and slow.

On line fatigue rate calculation. Long term storage of parameters.

Determination of optimum load change.

Influences operation of warm up controller.

TSC derives start up criteria for ATRS.

TURBOVISORY INSTRUMENT

TURBOVISORY PARAMETERS ARE:

VIBRATIONS- SHAFT VIBRATION / ECCENTRICITY

- BEARING VIBRATION

TURBINE EXPANSION

- OVERALL EXPANSION

- DIFFERENTIAL EXPANSION

- AXIAL SHIFT

SPEED / OVERSPEED

LOAD

TURBINE METAL TEMPERATURE VACUUM

LUB OIL PRESSURE / TEMPERATURE

HP / LP EXHAUST TEMPERATURE

VIBRATION MEASURING INSTRUMENTATION

SHAFT VIBRATION / ECCENTRICITY

- PROXIMITY PROBE

BEARING VIBRATION

- VELOCITY PICK UP

17

8/8/2019 voc trg2-02.10.09

18/45

Why do we analyse Vibration?

We can understand the machine

We can find the weakness

Thereby we can predict, plan, maintain and improve

Improve availability and reduce costs

What are the different ways?

Overall

Time domain

Frequency domain

Envelope analysis

Cepstrum analysis

Wavelet analysis

Etc

BasicSim

18

8/8/2019 voc trg2-02.10.09

19/45

W

VIBRATION MONITORING

Modes of Amplitudes :

DISPLACEMENT

VELOCITY

ACCELERATION

SPIKE ENERGY

Physical Significance Of Vibration Amplitude :

Displacement : Strain Indicator

Velocity : Fatigue Indicator

Acceleration : Force Indicator

The significance

Displacement gives the strain energy

Velocity gives the kinetic energy

Acceleration gives the force

Spike energy/HFD/gE are special ways to measure acceleration only.

UNITS OF MEASUREMENT:

DISPLACEMENT - MICRONS

VELOCITY - MM / SEC.

ACCELERATION - MM / SEC2 , G

AMPLITUDE DESCRIPTORS:

RMS - (Displacement ,Velocity)

PEAK - 1.414 RMS (Displacement, Velocity, Acceleration)

PEAK-TO-PEAK - 2 * PEAK (Displacement)

19

8/8/2019 voc trg2-02.10.09

20/45

SIM

20

8/8/2019 voc trg2-02.10.09

21/45

RE

Accelerometer :

Uses piezoelectric crystal

Normally uses internal amplifier for boosting signal

It will have low temp application up to 150 degree C

For high temperature application amplifier is not given inside

This causes low signal strength and we use gold plated contacts and small

cable lengths (output rated in pc per g). The amplification is done outside

Normal accelerometer (amplifier inside) will have strong signal output andcan sustain cable lengths of 300 meter

Available in several design, can go from DC to 10k Hz freq (600,000 CPM)

Can measure Acceleration, velocity and displacement

It is advised to involve suppliers or persons knowledgeable in this area to

choose accelerometers for on line monitoring applications

VelocityOutput=B*l*V B & l ar

21

8/8/2019 voc trg2-02.10.09

22/45

Velocity sensor :

This is self generating (764 mv per mm/sec)

Can sustain cable length of 1000 feet easily

For longer length intermediate amplification is needed

The temperature rating is higher up to 250 degree C (no electronics inside)

Sensitive to 60,000 CPM

Can check velocity and displacement only

CONDUCTIVE

PRO

22

8/8/2019 voc trg2-02.10.09

23/45

CONDUCTIVE

MATERIAL

THE

PROXIMI

The matching unit co

proportional to the dis

23

8/8/2019 voc trg2-02.10.09

24/45

CONDENSATE EXTRACTION PUMP (CEP)

The condensate extraction

pump (CEP) is a centrifugal

type vertical pump,

consisting of pump body,

can, distributor housing and

the driven lantern.

The steam after

condensing in the condensing in the condenser known as condensate is extracted

out of the condenser hot well by condensate pump and taken to the Deaerator

through ejectors, gland steam cooler and series of LP heaters. The function of

these pumps is to pump out the condensate. These pumps have four stages and

since the suction is at a negative pressure, special arrangements have been made

for providing sealing.

BOILER FEED PUMP (BFP)

24

8/8/2019 voc trg2-02.10.09

25/45

The Weir type

FK8D30 pressure

stage pump is an 8

stage horizontal

centrifugal

pump.This system

plays an important

role in supply of feedwater to the boiler at

requisite pressure

and steam/water

ratio.

This pump is

horizontal and of

barrel design driven

by an electric motor

through a hydrauliccoupling.

The water

with the given

operating

temperature should

flow continuously to the pump under a certain minimum pressure. It passes

through the suction branch into the intake spiral. After leaving first impeller it

passes through the distributing passages of the diffuser and thereby gets a certain

pressure rise. Thus the feed water reaching into discharge space develops the

necessary operating pressure.

Each BFP is provided with a Booster pump in its suction line, which is

driven by the main motor of the boiler feed pump. One of the major damages that

may occur to a BFP is from Cavitation or vapor bounding at the pump suction due

to suction failure. Cavitation will occur when the suction pressure of the pump at

the pump suction is equal or very near to the vapor pressure.

Deaerator25

8/8/2019 voc trg2-02.10.09

26/45

A steam generating boiler requires that the boiler feed water should be devoid of

air and other dissolved gases, particularly corrosive ones, in order to avoid

corrosion of the metal.

Generally, power stations use a deaerator to provide for the removal of air and

other dissolved gases from the boiler feedwater. A deaerator typically includes a

vertical, domed deaeration section mounted on top of a horizontal cylindrical

vessel which serves as the deaerated boiler feedwater storage tank.

GENERATOR AND ITS AUXILIARIESGENERATOR AND ITS AUXILIARIES

GENERATOR:

The 500 MW generator is a 3-phase, horizontallymounted 2-pole cylindrical rotor type, synchronous

machine driven by steam turbine. The stator

windings are cooled by de-mineralized water

26

http://en.wikipedia.org/wiki/Corrosionhttp://en.wikipedia.org/wiki/Deaeratorhttp://en.wikipedia.org/wiki/Corrosionhttp://en.wikipedia.org/wiki/Deaerator

8/8/2019 voc trg2-02.10.09

27/45

flowing through the hollow conductor while the rotor winding is cooled by

hydrogen gas. Fans mounted on the generator rotor facilitate the circulation of the

H2 inside the machine requiring cooling. 4 coolers mounted inside the machine

cool the H2 gas.

SPECIFICATIONS

Rated Parameters:

Maximum Continuous MVA rating : 588 MVA

Maximum Continuous MW rating : 500 KW

Rated Terminal Voltage : 21 KV

Rated Stator Current : 16200 Amps.

Rated Power Factor : 0.85 lag

GENERATOR PROTECTION:

The core of an electrical power system is generator. During operating conditionscertain components of the generator are subjected to increase stress and therefore,

could fail, referred to as faults. It can be internal fault or external fault depending

upon whether they are inside or outside of the machine. The machine with fault

must be tripped immediately. The corrective measures against generators

abnormal operation are taken care by stubborn system.

Task of the protective system:

Detect abnormal condition or defect.

Limit its scope by switching to isolate the defect.

Alarm the operating staff. Unload and/or trip the machine immediately.

Requirement of protective devices:

Selectivity: Only that part of the installation containing fault

should is disconnected.

Safety against faulty tripping: There should be no trip when

there is no fault.

Reliability: The device must act within the required time.

Sensitivity: Lowest signal input value at which the device must

act.

Primary sensing elements

Contents:Need for measurement:

What is measurement

To know value of a parameter with respect to a reference.

Need for measurement

Safety of man & machine

Increasing efficiency Better control of process parameters

Selection of instruments:

27

8/8/2019 voc trg2-02.10.09

28/45

Required accuracy of measurement Range of Measurement The form of final data display required Process media Cost Calibration and repair facilities required/available Layout restriction Maintenance requirement/availability

Pressure Measurement:

Defination-pressure is defined as force per unit area

Range almost vacuum to very high. Common measuring devices

Manometers:

Use Water, mercury and other liquids of known density etc.

Used For low pressure . Serves the Laboratory purpose for calibration use.

Diaphragm, capsule bellows are also used.

Bourdon tube gauges

Different types of transducers- e.g. strain gauge Pressure at the

bottom of a fluid column of height (h) is generated by the weight of

the column of fluid divided by the area: P = F/A = W/A. Weight (W)

is a function of volume (V) and density (d). Volume V = h A.

Therefore P = (d h A)/A or P = d h. Pressure can be expressed

as head pressure in terms of the depth (h) of the fluid

28

8/8/2019 voc trg2-02.10.09

29/45

Gauge pressure is measured relative to the local ambient pressure. It's thedifference between the measured pressure and atmospheric pressure, unless

the ambient pressure surrounding the sensor is different from the

atmospheric pressure

Vacuum is pressure measured below atmospheric pressure, referenced to

atmospheric pressure. Vacuum is negative gauge pressure.

Bourdon tube

Operating principle-

The process pressure causes tube to deflect. Deflection is

proportional to the pressure difference between inside and outside the

tube pressures since the outside pressure is atmospheric

Range Helical bourdon - 0-0.5 Kg/cm2 up to 0-6000 kg/cm2

C Type bourdon - up to 700 kg/cm2 Flat spiral bourdon - low ranges 0-70 kg/cm2

29

8/8/2019 voc trg2-02.10.09

30/45

30

8/8/2019 voc trg2-02.10.09

31/45

Errors in Bourdon Tube gauge measurement

Transmitters

A transmitter has a process signal such as pressure, flow, level ortemperature as its input and an electric or pneumatic signal as its output. Function -Proportionally modulate an electric / pneumatic signal in

response to the process parameters.

Electronic transmitters- These transmitters sense the change in processvariable within a certain range and produce an output current within a

range.

Standard range- 4 to 20mA DP transmitters transmit the difference between pressure applied to its two

input.

Transmitter connection

Level measurement

31

8/8/2019 voc trg2-02.10.09

32/45

Level-the height of a liquid or solid above a reference line. Various media

Open vessels

DM storage Tank Fuel Oil Lube Oil tanks

Closed vessels

HP-LP heaters Dearator Condenser hot well

Solid materials

Coal bunker level Hopper level

Methods

Basic principles

Floats and liquid displacers

Head pressure measurement

Electrical / electronic Advanced principles

Capacitance

Conductance

Radar

Ultrasonic

Floats & Liquid displacers

Floats can be made of a hollow metal, a plastic material or molded rubber.

Floats can be used for

1.Continuous level measurement

2.Float operated switches

3.Liquid displacer systems

32

8/8/2019 voc trg2-02.10.09

33/45

Flow measurement

Flow is rate of crossing of a fluid at a cross sectional area. Measurement methods

Differential pressure flow meters

Variable area flow meters

Displacement and interferential flow meters

Electromagnetic flow meters

Ultrasonic flow meters

Other flow measuring techniques

Turbine Flow meter

If a fluid moves through a pipe and acts on the vanes of a turbine, the

turbine will start to spin and rotate. The rate of spin is measured to

calculate the flow.

Ultrasonic Doppler flow meter

The frequency of the reflected signal is modified by the velocity and

direction of the fluid flow.

If a fluid is moving towards a transducer, the frequency of the

returning signal will increase. As fluid moves away from a

transducer, the frequency of the returning signal decreases.

The frequency difference is equal to the reflected frequency minus

the originating frequency and can be use to calculate the fluid flow

speed

Application in plant

Level measurement

Drum level-hydra step

Bunker level-strain gauge

CFT,MOT level-ultrasonic

Pressure measurement

Drum pressure-PT

HFO pressure-PT

33

8/8/2019 voc trg2-02.10.09

34/45

TEMPERATURE MEASURING INSTRUMENTS

WHY TEMPERATURE?

ASSESS THE MATERIAL FATIGUE,HEAT BALANCE,HEAT

TRANSFER etc.

ASSESSING THE PROCESS CONDITION

EFFICIENT AND ECONOMIC OPERATION AT DETERMINED

LOAD.

VITAL INFORMATION DISPLAY FOR SAFE OPERATION OF THE

PLANT.

ANALYSIS

SELECTION OF INSTRUMENT:

PRIMARY INSTRUMENTS

Thermocouple

Resistance thermometer (Pt100,Cu53)

SECONDARY INSTRUMENTS : Uses electronic bridges (for alarm &

protection)

SELECTION OF INSTRUMENT ALSO DEPENDS ON :

The accuracy required

The range of temperature

Process media on sensing element

The layout conditions and restrictions

Facilities available for calibration of the instrument

34

8/8/2019 voc trg2-02.10.09

35/45

Basic ideaBasic idea

Basic ideBasic ide

35

8/8/2019 voc trg2-02.10.09

36/45

Basic ideBasic ide

THERMOCOUPLE

THEY MUST PHYSICALLY WITHSTAND TEMPERATURE FOR

WHICH THEY ARE SELECTED

COMPOSITION/CHARACTERISTICS SHOULD NOT CHANGE FOR

THESE TEMPERATURE RANGE

THEY SHOULD POSSESS REASONABLY LINEAR TEMPERATUREEMF RELATIONSHIP

THEY SHUOLD DEVELOP AN EMF PER DEG CHANGE OF

TEMPERATURE.

COMBINATIONS

IRON-CONSTANTAN, TYPE-J, RANGE: 0-760 DEG C

Constantan Cu 56-57 % Ni 43-44 %, bright and non magnetic

CHROMEL- ALUMEL , TYPE-K, RANGE: 0-1260 DEG CChromel:Ni 89 %,Cr 9.8%,Fe 1%,Cobalt 0.2%,Dull & Nonmagnetic

Alumel :Ni 94.5%,Al 2%,S 1.0% Mn 2.5%,Glossy & slightly magnetic

COPPER CONSTANTAN , TYPE-T, RANGE: -180 TO +370 DEG C

CHROMEL COPEL, TYPE-E, RANGE: 0-870 DEG C

PLATINUM-RHODIUM-PLATINU: TYPE-S, RANGE: 0-1480 DEG C

Compensation:

36

8/8/2019 voc trg2-02.10.09

37/45

Resistance

Thermometer

PROPERTIES :

Stable

temperature-resistance relationship

Change in resistance w.r.t. temp. should be large

Change in resistance due to strain or non temp method should be less.

Commercially available

They are Nickel, Copper and platinum

PHYSICAL PROPERTIES

37

8/8/2019 voc trg2-02.10.09

38/45

Ni : Non linear characteristic

Specific resistance 6.38 micro ohm-cm

Tempeature coefficient .0066 ohm

Cu : Linear characteristic

Specific resistance of Cu is very less(1.56 micro ohm-cm)

Temperature coefficient 53 ohm

Pt : Costly

More suitable than Cu,Ni

Specific Resistance 9.38 micro ohm-cm

Temperature coefficient 0.00385 ohm

COMPENSATION FOR LEAD WIRE RESISTANCE

RTD Vs THERMOCOUPLE

THERMOCOUPLE RTD

Require ref junction No ref junction

With constant temp. Absolute measurement

Sensitivity is less Greater sensitivity (the change in temp/deg C

is larger, micro change is measured more

easily)

No semiconductor Semiconductor material having resistance

values -100 to +450 deg C made of metal

oxides and their mix.

AUTOMATIC CONTROL

Automatic control is used in the power plants to ensure safe and efficient

operation of the plant. The type of the control system varies from the Simple

38

8/8/2019 voc trg2-02.10.09

39/45

Pneumatic control systems on auxilliary plants to Microprocessor based control

systems on main plant loops.

BASIC AUTOMATIC CONTROL TERMS

1.PROCESS : The act of physically or chemically changing, including

combining, matter or of converting energy.

2.PLANT : Installation in which process is carried out.

3.CONTROLLED CONDITION : The physical quantity or condition of the

controlled body, process or machine which is the purpose of the system to control.

4.CONTROL SYSTEM : An arrangement of the elements interconnected and

interacting in such a way so as to maintain or to effect in a prescribed

manner,some condition of a body or process or machine which forms part of the

system.

5.DESIRED VALUE : The value of the controlled condition which the operator

wishes to maintain.6.MEASURED VALUE : The actual value of the controlled condition.

7.DEVIATION : The difference between the measured value and the desired

value.

8.AUTOMATIC CONTROLLER : The item in a control system which compares

the desired and the measured value and operates in such a way so as to reduce the

deviation.

9.MEASURING UNIT : A unit which gives the signal corresponding to the

controlled condition.

10.CORRECTING UNIT : A unit which receives signal from the controller tochange the controlled condition.

11.OPEN LOOP CONTROL SYSTEM : A control system without the monitoring

feedback.

12.CLOSED LOOP CONTROL SYSTEM : A control system with monitoring

feedback,the deviation signal formed as a result of this feedback being used to

control the action of the correcting element in such a way so as to tend to reduce

the deviation of zero.

CLOSED LOOP CONTROL SYSTEMThe most common type of a control system used in a plant is a closed loop control

system. The controlled condition of the plant (pressure, level, flow, temperature)

is measured by the measuring unit and sends a signal to the controller of the

measured value(M.V.) .the controller receives a second signal which is the desired

signal(D.V.) for the controlled condition. The controller compares the measured

and the (Power cylinder, Control valve) to move it in such a direction so as to

reduce the deviation.

The amount the correcting unit moves and in what direction it travels depends on

the magnitude and the direction of the deviation.

M.V D.V. = DEVIATION (LARGE OR SMALL MAGNITUDE)

(POSITIVE OR NEGATIVE DIRECTION)

39

8/8/2019 voc trg2-02.10.09

40/45

For example, let us consider that a closed loop control system is used to control

the temperature of air in a building. the indoor temperature is measured and

compared with the desired value of temperature and any deviation will cause

more or less fuel OIL to be burnt. The controller will see the result of its action

and adjust the fuel flow until there is no deviation. If the temperature suddenly

falls outside the building no change in the temperature will occur inside the

building due to the wall insulation. Eventually the temperature inside the building

will fall and the indoor temperature detector will detect it. The closed loop control

system will adjust the fuel oil flow until no deviation shows.

OPEN LOOP CONTROL SYSTEM

Open loop control systems are seldom used but they are used in conjunction with

the closed loop control system to improve the quality of control.

The outside temperature is measured and compared with the desired value of

temperature, and any deviation will cause more or less fuel to be burnt. The

controller will not see the results of its actions but will supply more or less fuelaccording to the magnitude and direction of the deviation. If the temp. outside the

building suddenly falls, the outdoor temperature detector will detect this

immediately and the controller will immediately increase the fuel oil flow and

thus the inside temperature increases.

In this case the corrective action can be taken as soon as the outside temperature

falls. The disadvantage is that it cannot see the results of its actions and variations

in the inside temperature will occur due to boiler efficiency or amount of

ventilation.

COMBINED CLOSED AND OPEN LOOP SYSTEM

Closed loop control system is the main loop and will control the inside

temperature without any deviation. If the outside temperature suddenly falls the

open loop system will detect the fall in temperature and increase the fuel oil input

by using both types of control system together we can use the advantages of both

the systems and improve the quality of control.

DATA ACQUISITION SYSTEM:

INTRODUCTION:

Power plant is a very specialized field and requires close and simultaneous

monitoring of various plant equipments like boiler, turbine, generator, feed pump,etc. and associated auxiliaries to maintain the continuous availability of

the unit as well as to ensure the safe and efficient operation of these equipments.

For such monitoring purposes, a lot of plant data (analog inputs) in the form of

40

8/8/2019 voc trg2-02.10.09

41/45

physical measurements and status of equipment (digital inputs) are needed

(around 4500).

In earlier days, a central control room was used were all these measurements were

displayed in the form of indicators, recorders and some local panels in the field

were some specific monitoring was carried out.

But these indicators had the following limitations:

1. LIMITATION OF PHYSICAL SPACE.

2. LIMITATION OF SIMULTANEITY IN MONITORING

3. LIMITATION OF HISTORICAL STORAGE

4. LACK OF FLEXIBILITY

5. UNAVAILABILITY OF PROCESSED/CALCULATED

DATA

Hence, a need was felt for computerized intelligent system presenting data from

the entire plant to facilitate easy monitoring, recoding and to enable the operator

to take quick decisions regarding the operation.

COMPUTER BASED DAS

This system has the following features:

IN THE FORM OF DISPLAYS ON THE CRTS:

(with a facility of display and hard copy printout) through simple key

strokes/dedicated keys.

1.Variety of plant data in the form of analog measurements displayed on CRTs

(display units) in the form of group reviews(organized in plant functional groups).

2.GRAPHICS:

Graphics showing the replica of entire plant and its subsystems and individual

equipments embedded with live plant data-current values of temp., pressure, and

the status of different pumps through different colour codes (e.g. red for ON and

green for OFF).

3.BARS:

Bars(both vertical and horizontal) showing like analog measurements e.g. reheater

tube metal temperatures help the operator to compare the measurements to find

the hottest spot.

4.ALARM DISPLAYS:

These displays help in annunciation of a lot of abnormal conditions not covered in

the annunciation window.

These displays help in pinpointing the individual alarm,which led to a groupalarm in the annunciation window.Further exact measurements values and rate of

change there of can be seen on the CRTS.

41

8/8/2019 voc trg2-02.10.09

42/45

5.HISTORICAL STORAGE:

X-t plot shows plot of a physical variable like main steam pressure, generator load

with time nearing different intervals like 10 secs, 1 mts, 10 mts, 1 hour, 24 hours,

even 1 day etc. Group trend shows value of different inputs collected on different

intervals over a period of time.

6.PLANT STARTUP GUIDANCE MESSAGES (PSGM) AND OPERATOR

GUIDANCE MESSAGES (OGM):

PSGM shows the different criteria, steps to be taken before starting an equipment

in the form of flow charts with the current status of the step being completed or

not. An OGM shows the various steps to be taken by the operator in the event of a

fault.

These steps are particularly very useful in starting/shut down of the unit.

ELECTROSTATIC PRECIPITATORELECTROSTATIC PRECIPITATOR (ESP)

Indian coal contains about 30% of ash. The hourly consumption of coal of a

200 MW unit is about 110 tons. With this, the hourly production of ash will be 33

tons. If such large amount of ash is discharge in atmosphere, it will create heavy

air pollution thereby resulting health hazards. Hence it is necessary to precipitate

dust and ash of the flue gases.

Precipitation of ash has another advantage too. It protects the wear and

erosion of ID fan.

To achieve the above objectives, Electrostatic Precipitator (ESP) is used.

As they are efficient in precipitating particle form submicron to large size they are

preferred to mechanical precipitation.

An ESP has series of collecting and emitting electrons in a chamber

collecting electrodes are steal plates while emitting electrodes are thin wire of

2.5mm diameter and helical form. Entire ESP is a hanging structure hence the

electrodes are hung on shock bars in an alternative manner.

There are transformer and rectifiers located at the roof of chamber. Hopper

and flushing system form the base of chamber.

AN OVERVIEW OF

SSTPS, NTPC

42

8/8/2019 voc trg2-02.10.09

43/45

N.T.P.C.

S.S.T.P.S

SHAKTINAGAR

SONEBHADRA (U.P.)

43

8/8/2019 voc trg2-02.10.09

44/45

ROTOR OF L.P. TURBINE

ROTOR OF H.P. TURBINE

44

8/8/2019 voc trg2-02.10.09

45/45

COAL HANDLING PLANT (C.H.P.)