A Report on Practical Training

Undertaken At

NATIONAL THERMAL POWER CORPORATION

(Period: From 15/05/2005 to 14/06/2005)

SUBMITTED TO: SUBMITTED BY: R. K. ASH PUNEET SHARMA

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DGM 2nd year Electrical Engg. NTPC, KAWAS SVNIT, SURAT

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ACKNOWLEDGEMENT

It gives us great pleasure to present this training report to the learning

centre, NTPC (National Thermal Power Corporation) Limited, Kawas,

combined cycle power project, Hazira, Surat. This training program was

immense support to our theoretical knowledge. This formed a bridge

between theoretical and practical knowledge. We are thankful to

management of NTPC Kawas who gave us this golden opportunity to

undergo our vocational training at their plant. I would like to thank Mr. S.

K. JHA (Chief Manager, HRD) to give us this opportunity. I would like to

express our extreme gratitude towards Mr. R. K. Ash (DGM), Mr.

Dhirendra. P. Jajoria (senior engg.), R.G. Patel.

Everyone extended their full co-operation and concern towards our

training. They overlooked all disturbance and inconvenience caused by us

in their work.

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CONTENTS

S.No. TOPIC Page No.

1. Introduction to NTPC 04

2. Introduction to KGPP 08

3. Combined Cycle Gas Turbine 10

4. Gas Turbine 13

5. Waste Heat Recovery Boiler 26

6. Steam Turbine 29

7. Generator 31

8. Transformers 40

9. Switchyard 43

10. Electrical Protections 49

11. SWAS 52

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INTRODUCTION TO NATIONAL THERMAL POWER

CORPORATION LIMITED

NTPC, the largest power generating company of the country, presently has an

installed capacity of over 31000 MW. NTPC presently operates over 27 power

stations. NTPC ranked 317th in ‘2009, Forbes Global 2000’ ranking of the

world’s biggest companies. Currently over 17,000 MW capacity is under

construction at 19 projects in 12 states and NTPC plans to become a 75 GW by

2017.

Government of India, Deptt. of Public Enterprises, Ministry of Heavy Industries &

Public Enterprises vide Office Memorandum dated 19th May, 2010 has conveyed

grant of Maharatna status to NTPC apart from three other Central Public Sector

Enterprises (CPSEs). Since, presently NTPC has requisite number of non-official

Directors on its Board, therefore, only NTPC is eligible to exercise delegated

Maharatna powers.

Installed Capacity

NO. OF PLANTS CAPACITY (MW)

NTPC Owned

Coal 15 24,885

Gas/Liquid Fuel 7 3,955

Total 22 28,840

Owned By JVs

Coal & Gas 5 2,864

Total 27 31,704

Section I.01 Regional Spread of Generating Facilities

REGION COAL GAS TOTAL

Northern 7,525 2,312 9,837

Western 6,360 1,293 7,653

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Southern 3,600 350 3,950

Eastern 7,400 - 7,400

JVs 924 1,940 2,864

Total 25,809 5,895 31,704

Coal Based Power Stations

With 15 coal based power stations, NTPC is the largest thermal power generating

company in the country. The company has a coal based installed capacity of

24,885 MW

COAL

BASED(Owned by

NTPC)

STATE

COMMISSION

ED

CAPACITY(M

W)

1. Singrauli Uttar Pradesh 2,000

2. Korba Chhattisgarh 2,100

3. RamagundamAndhra

Pradesh2,600

4. Farakka West Bengal 1,600

5. VindhyachalMadhya

Pradesh3,260

6. Rihand Uttar Pradesh 2,000

7. Kahalgaon Bihar 2,340

8. NCTPP, Dadri Uttar Pradesh 1,330

9. Talcher Kaniha Orissa 3,000

10

.

Feroze Gandhi,

UnchaharUttar Pradesh 1,050

11

.Talcher Thermal Orissa 460

12

.Simhadri

Andhra

Pradesh1,000

13 Tanda Uttar Pradesh 4406 | P a g e

.

14

.Badarpur Delhi 705

15

.Sipat-II Chhattisgarh 1,000

Total 24,885Coal Based Joint Ventures:

COAL BASED

(Owned by

JVs)

STATE COMMISSION

ED CAPACITY

1. Durgapur West Bengal 120

2. Rourkela Orissa 120

3. Bhilai Chhattisgarh 574

4. Kanti Bihar 110

Total 924

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Gas/Liquid Fuel Based Power Stations

GAS BASED

(Owned by NTPC)STATE

COMMISSION

ED

CAPACITY(M

W)

1. Anta Rajasthan 413

2. Auraiya Uttar Pradesh 652

3. Kawas Gujarat 656

4. Dadri Uttar Pradesh 817

5. Jhanor-Gandhar Gujarat 648

6.Rajiv Gandhi CCPP

KayamkulamKerala 350

7. Faridabad Haryana 430

Total 3,966

Gas Based Joint Ventures:

COAL BASED

(Owned by JVs) STATE

COMMISSIONE

D CAPACITY

1. RGPPL Maharashtra 1940

Total 1940 

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Hydro Based Power Projects (Under Implementation)

NTPC has increased thrust on hydro development for a balanced portfolio for long

term sustainability. The first step in this direction was taken by initiating

investment in Koldam Hydro Electric Power Project located on Satluj river in

Bilaspur district of Himachal Pradesh. Two other hydro projects under

construction are Tapovan Vishnugad and Loharinag Pala. On all these projects

construction activities are in full swing.

 

HYDRO BASED STATEAPPROVED

CAPACITY(MW)

Koldam (HEPP)Himachal

Pradesh800

Loharinag Pala (HEPP) Uttarakhand 600

Tapovan Vishnugad (HEPP) Uttarakhand 520

Total

1920

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INTRODUCTION TO KAWAS GAS POWER PLANT

ABOUT GAS POWER PLANTS

In olden days the Power Stations were constructed to run either on coal or with

water (that is getting collected in the catchment area) which are called thermal or

hydro power stations respectively. In the recent past say for 15 to 20 years in

India the Gas based power stations have come into existence with the exploration

of the gas by ONGC and transportation of the same by GAIL. These power

stations are operated on gas either in open cycle or in combined cycle mode. As

the operation in open cycle is costly, the power producers prefer running the gas

power station only in combined cycle mode rather than in simple cycle mode

because of the cost consideration.

As you are all aware in general the Gas Turbines can produce about 55 - 58%

extra energy thru’ the Steam Turbine from out of the steam generated in HRSGs

with the heat exchange that is taking place between flue gases and the water

inside the HRSGs. These power stations have become much more popular

because of the following considerations:

1. Starting of the units and bringing them on to the bar is easier/faster when

compared to

the thermal units.

2. When used on gas these units are quite cost effective.

3. When the right equipment is selected, these are good work horses, which

can be continued in service after synchronization without much trouble.

There are minimum numbers of controls when compared with the thermal

unit of the same capacity.

4. The efficiency of the combined cycle unit is about 48% when compared to

about 35% of thermal units. Of-course the efficiency of Trent Engines is

about 56%.

5. The personnel required to operate combined cycle plant of the same

capacity is much less than that of a thermal plant.

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6. These are short gestation projects which take less time for installation &

commissioning. The Gas units are fully automatic and of single button

operating units and they can be started & loaded sequentially.

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INTRODUCTION TO KGPP

Kawas gas power project (KGPP) is one of the important power project of NTPC.

It was established in 1991. KGPP is situated at Kawas village near Surat

(Gujarat).

KGPP is gas based combined cycle power project which has 2 blocks. The capital

cost is about 1600 crore. KGPP is a France technology power project. The plant

has 2 blocks. Total capacity of plant is: 2x328.1 MW. Each block consists of 2 gas

turbine generators and one steam turbine generators.

Combined Cycle:

Combine cycle power plant integrates 2 power conversion cycles. Brayton cycle

(GT) and Rankine cycle(ST) with the principle objective of increasing overall plant

efficiency. The overall combine cycle efficiency comes to 45%.

KGPP gets auxiliary supply for plant from 2 station transformers. Plant generates

11.5 KV and this voltage is step up at 220 KV then transmitted. The plant have

diesel generator of capacity 5 MVA. It is used when power fails from both station

transformers.

The outgoing lines from plant are:

Kawas-Haldarva I

Kawas-Haldarva II

Kawas-vav II

Kawas–Navsari I

Kawas–Navsari II

Kawas-Ichchhapore I

Kawas-Ichchhapore II

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WORKING OF KAWAS GAS POWER PLANT

The gas plant at Kawas consists of two blocks. Each block contains two gas

turbine, two boilers and one steam turbine. One boiler for each gas turbine and a

by pass chimney.

The working of the gas turbine starts with the starting of the turn gear and then

the cranking motor (1MW) which rotates the shaft of the compressor which is

coupled through a torque converter. The compressor compresses the inlet

atmospheric air to 10 bars which is then fed to the combustion chamber for

combustion of fuel (can be naphtha, gas, or high speed diesel) which produces

flue gas. Now the gas turbine which performs the major function of using the flue

gas energy and movement of generator rotor and winding. The rotation of turbine

rotor at 3000 rpm gives 50 Hz A.C. The power output of generator is 106 MW at

11 KV. This power can be transmitted to 11 kilometers so now it is being step up

to 220 KV by a step up transformer which is then given to the switch yard and

then to the western grid .

The gas plant can run in both forms either in open cycle or combined cycle. In

open cycle the exhaust of the gases is passed to the atmosphere through a by pass

chimney where as in combined cycle the exhaust gases are used to heat up water

to steam to run steam turbine.

When working in combined cycle the exhaust gases (5400 C) are passed through

boiler. The boiler has a typical arrangement of different layers of economizer,

evaporator, superheater and preheater with two drums HP and LP.

The water from feed water tank is pumped to HP as well as LP economizer which

increases the temperature of the water. This water then reaches HP and LP drum

respectively. From these drums, pumps are used to pump the water to evaporator

which converts water to steam. This steam is passed through superheater, which

further increases temperature of steam. The HP steam from both the boilers is

then fed to HP turbine. At the exhaust of HP turbine both HP and LP steam are

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mixed and then feed to LP turbine. The generator connected to the turbine

produces 116.6 MW which is again supplied to step up transformer. Water is

passed through condenser which converts steam to water and now this cooling

water goes to cooling tower. Thus produced water is collected in hotwell which is

further pumped into the feed water tank through a preheater which increases the

temperature of water.

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EFFICIENCY TREND COMBINED CYCLE

Air Fuel

Exhaust gas

Steam Turbine

Steam

G

G

Combined Cycle Power PlantWHRB

15%

100%

33%

16%

36%

Gas Turbine

Input

Condensor

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GAS TURBINE

The gas turbine is a common form of heat engine working with a series of

processes consisting of compression of air taken from atmosphere, increase of

working medium temperature by constant pressure ignition of fuel in combustion

chamber, expansion of SI and IC engines in working medium and combustion but

it is like steam turbine in its aspect of the steady flow of the working medium.

At Kawas, the GE-Alsthom made Gas Turbine (Model 9E) has an operating

efficiency of 31% and 49% in open cycle and combined cycle mode respectively

when natural gas is used as fuel. Today gas turbine unit sizes with output above

250 MW at ISO conditions are being designed and developed.

The modern gas turbine plants are commonly available in package form with few

functional sub assemblies.

The 9E model GEC-Alsthom package consists of

• Control compartment

• Accessory compartment

• Turbine compartment

• Inlet exhaust system

• Load package

• Generator excitation compartment

• CO2 fire protection unit

The basic functional sub assemblies of Kawas GT package plant

are:

• Control compartment

The control compartment contains the equipment needed to provide control

indication and protection functions. Arrangement can be made for manual

operation or for remote unattended operation. The

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control compartment is located at local control room and includes the turbine

control panel, generator control panel, batteries and battery charger.

• Accessory compartment

The accessory compartment, contains the mechanical and control elements

necessary to allow the gas turbine to be a self, contained operational station. The

major components located in the accessory compartment are the lubricating oil

system and reservoir, lube oil cooler, starting means, accessory gear fuel system,

turbine gauge panel, hydraulic system and atomising air system, water system,

cranking motor exhaust frame blowers (88TK-1, 88 TK-2.)

• Turbine compartment

The gas turbine has a 17 stage axial compressor. The compressor rotor consists of

individual discs for each stage, and is connected by through bolts to the forward

and aft stub shafts. The turbine rotor consists of three stages, with one wheel for

each bucket stage. The turbine rotor wheels are assembled by through bolts

similar to the compressor, and with two spacers, one between the first and second

stage wheels, and the other between the second and the third stage wheels.

The entire stator stages utilize precision cast, segmented nozzles, with the 2nd

and 3rd stage segments supported from the stationary shrouds. This arrangement

removes the hot gas path from direct contact with the turbine shell.

The turbine rotor stages also have precision cast, long shank buckets (air foils on

the compressor wheels are called blades, those on turbine wheels are called

buckets) and this feature effectively shields the wheel rims and bucket dovetails

from the high temperature of the main gas steam. The gas turbine unit and shells

are split and flanged horizontally for convenience of disassembly. Compressor

discharge air is contained by the discharge casing, combustion wrapper, and

turbine shell. The 14 combustion liners are mounted completely inside the

combustion wrapper, which eliminates the need for combustion cans.

• Inlet and exhaust system

The inlet arrangement includes inlet air filters, silencing, ducting and trash

screens to protect the compressor from debris. The inlet arrangements generally

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comes out from the back of the inlet air house, over the control and accessory

compartments, and down to the inlet plenum, which is mounted on the turbine

base. The exhaust arrangement includes the ducting, silencing, and necessary

expansion joints. The exhaust gases exit from the side to exhaust plenum, which is

mounted separately on its own base, and are directed straight out to the exhaust

arrangement.

• Load package

The load package consists of an air-cooled, synchronous generator and associated

equipment. The generator also has roof-mounted terminals for out going leads. An

air-cooled open ventilation of generator and associated equipments can be used in

the load compartment.

• Fire protection unit

The fire protection system consisting of on base piping, detectors etc. capable of

distributing a fire extinguishing agent (CO2, or Halon) in all the compartments of

the gas turbine and local control room. The bulk of fire extinguishing agent stage

unit is located near gas turbine with one main CO2 skid.

OPERATION

The package plant has been designed to provide maximum operational flexibility

and simplicity. The actual operating sequence can be best understood by

considering the four basic operating modes: Stand By, Start, Run and Shutdown.

• Stand by

During stand by, each component must be maintained in a state, which allows for

immediate start up

operation if needed.

All the station components that are affected by low temperature or moisture are

fully protected during

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stand by. The lubricating oil and the control compartment are maintained at a

minimum temperature. The batteries are kept fully charged and heated. Turbine

compartment is also maintained hot.

• Starting the unit

Start-up can be ordered either remote or from the control compartment. (LCR)

The starting sequence is given below:

1. The starting system consists of an induction motor and torque converter

coupled to the accessory gear.

2. The staring system is energized and connected to the turbine up to the value

from which Turbine

becomes self-sustaining.

3. At about 12% normal speed, fuel is injected and ignited.

4. To avoid thermal shocks in hot parts of turbine, the unit is accelerated under

acceleration mode after a

Short warm-up period.

5. When the turbine becomes self-sustaining, the gas turbine speeding up

continues, but the starting

system (Cranking motor) is automatically made off at 60% speed.

• Running

The operator at either the local or remote station has the option of holding the

station at spinning reserve, or loading to a point, or running under maximum load

exhaust temperature control. The load can be varied manually over the entire

load range.

• Shut down

Upon initiation of a normal shut down signal, either locally or remotely, the

following events occur:

1. The generator load is gradually reduced to zero.

2. The generator breaker is opened.

3. The fuel supply is reduced & then is shut off.

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4. The gas turbine coasting down to rest.

The starting system components also provide slow speed rotation of the turbine

for cool down

purposes after shut down. A crank and restart can be initiated at any time below

10% speed & can also

be started above 95% speed.

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ACCESSORIES COMPARTMENT

Starting of gas turbine takes place from this compartment. All the motors

required for turbine startup till the cooling of the turbine are placed here. Below

all the motors there is lube oil tank through which lube oil for cooling purpose is

taken. The main motors in this compartment include:

1. Turn Gear Motor.

2. Cranking Motor.

3. Pumps for water cooling

4. Three lube oil pumps

Main pump

Auxiliary pump (AC)

Emergency pump(DC)

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COMPRESSOR

The axial-flow compressor section consists of the compressor rotor and the

casing. Included within the compressor casing are inlet guide vanes, the 17

stages of rotor and stator blading, and the exit guide vanes. In the compressor,

air is confined to the space between the rotor and stator blading where it is

compressed in stages by a series of alternate rotating (rotor) and stationary

(stator) airfoil-shaped blades.

The rotor blades supply the force needed to compress the air in each stage and

the stator blades guide the air so that it enters in the following rotor stage at the

proper angle. The compressed air exits through the compressor-discharge casing

to the combustion chambers. Air is extracted from the compressor for turbine

bearing cooling sealing, and for pulsation control during start-up (to avoid

surging). Since minimum clearance between rotor and stator provides best

performance in a compressor, parts have to be assembled very accurately.

Compressor is used to increase the pressure of air and that pressurized air is

injected into the combustion chamber, so that proper combustion of fuel takes

place. For starting the compressor rotor cranking motor is used and when the

speed reaches to 60% of the operating speed the cranking motor is cut off and

now the compressor rotor rotates with the rotation of turbine rotor as both of

them are coupled together. This is known as self -sustaining stage.

The amount of air entering the compressor depends on the working condition of

the gas turbine i.e. either it is running on full load or on no load or is in start up

or shutdown sequence. Inlet Guide Vane (IGV) is used to control the amount of

inlet air to the compressor. It is operated by servo valve mechanism by which its

blade moves from 34 to 84 degrees which controls the amount of inlet air

according to the load.

COMPRESSOR AIR EXTRACTION

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During operation of the gas turbine, air is extracted from various stages of the

axial flow compressor to:

1. Cool the turbine parts subject to high operating temperature.

2. Seal the turbine bearings.

3. Provide an operating air supply for air operated valves.

4. Air bleeds off to avoid pulsation.

5. For pulse Jet-cleaning system.

6. Fuel nozzle atomizing air.

5th stage air

Air is extracted from the compressor 5th stage and is externally piped from

connections in the upper and lower half of the casing for cooling and sealing of all

rotor bearings.

11th stage Air

Air from the compressor 11th stage is bled only during unit start-up and shut

down for pulsation control. The compressor bleed valves are closed during unit

operation.

17th stage Air

Air extracted from the compressor 17th stage flows radially inward between the

stage 16 and 17 wheels, to the rotor bore, and then aft to the turbine where it is

used for cooling the turbine 1st and 2nd stage buckets and rotor wheel spaces.

Compressor discharge air

Air extracted from compressor discharge is used for liquid fuel atomising air,

stage 1 nozzle vane and

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retaining ring cooling, stage 2 nozzle cooling, pulse & for Pulse Jet cleaning

system.

Variable inlet guide vanes

Variable inlet guide vanes are located at the aft end of the inlet casing.

The position of these vanes has an effect on the quantity of compressor airflow.

Movement of these guide vans is accomplished by the inlet guide vane control

ring that turns individual pinion gears attached to the end of each vane. The

control ring is positioned by a hydraulic actuator and linkage arm assembly.

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COMBUSTION SECTION

The combustion system is of the reverse flow type with 14 combustion chambers

arranged around the periphery of the compressor discharge casing. This system

also includes fuel nozzles, spark plug ignition system, flame detectors, and

crossfire tubes. Hot gases, generated from burning in combustion chambers, are

used to drive the turbine.

High-pressure air from the compressor discharge is directed around the

transition pieces and into the combustion chambers inlets. This air enters the

combustion zone through metering holes for proper fuel combustion and through

slots to cool the combustion liner. Fuel is supplied to each combustion chamber

through a nozzle designed to disperse and mix the fuel with the proper amount of

combustion air.

Orientation of the combustion around the periphery of the compressor is shown

on figure CS-1.Combustion chambers are numbered counter-clockwise when

viewed looking down-stream and starting from the top of the machine. Spark plug

and flame detectors locations are also shown.

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Flame Detectors:

During the start up sequence, it is quite essential that an indication of flame or

no-flame to be transmitted to the control system. For this reason, a flame

monitoring system is used consisting of four sensors which are installed on four

combustion chambers No.4, 5 and 10, 11 and an electronic amplifier which is

mounted in the turbine control panel.

Spark plug:

Combustion is initiated by means of the discharge from two high-voltage,

retractable-electrode spark plugs installed in adjacent combustion chambers

(No.12 and 13) These spring-injected and pressure retractable plugs receive their

energy from ignition transformers. At the time of firing, spark at one or both

plugs ignites the gases in a chamber. The remaining chambers are ignited by

crossfire through the tubes that interconnect the reaction zones of the remaining

chambers. As rotor speed increases, chamber pressure causes the spark plugs to

retract and the electrodes are removed from the combustion zone.

TURBINE SECTION

The three-stage turbine section is the area in which the energy in the hot

pressurized gas produced by compressor and combustion sections is converted

into mechanical energy. The MS 9E major turbine section components include:

the turbine rotor, turbine shell, exhaust frame, exhaust diffuser, nozzles and

diaphragms, buckets & shrouds, and No.3 (aft) bearing assembly, spacers.

Turbine is just opposite to the compressor here the gases expand. The

temperature at the inlet of turbine is around 1100 and at the exhaust is 540. The

first stage of turbine rotor blade consists of 96 blades. Air cooling arrangements

are provided for turbine 1st and 2nd stage. Stator or the stationary part is so

designed that it passes the flue gasses from one stage to another stage,

tangentially to the next stage so that maximum torque can be applied to the

blades of the turbine and maximum rotation occurs

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Turbine is only of 1 or 3/2 meter. Now flue gases passes through rotor blades

(buckets) of the turbine and rotates the turbine. These flue gases from the turbine

come out and pass through the damper. If damper is closed then all the flue gases

moves to the atmosphere through by pass stack which is a vertical cylinder like

structure of metal with a height of 30 m. This is called as open cycle operation. If

damper is open, then all the flue gases pass through the boiler which is called

combined cycle operation.

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1st and 2nd stage of Turbine Rotor

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WASTE HEAT RECOVERY BOILER (WHRB)

Waste heat is heat, which is generated in a process by way of fuel combustion or

chemical reaction, and then “dumped” into the environment even though it could still be

reused for some useful and economic purpose. The essential quality of heat is not the

amount but rather its “value”. The strategy of how to recover this heat depends in part

on the temperature of the waste heat gases and the economics involved.

Waste heat recovery boiler is an essential part of the whole system of gas power plants.

Using WHRB the overall efficiency of the system is increased. Water from feed water

tank is pumped using feed water pumps to the HP and LP lines. We have two 100% and

one 30% line, water is supplied according to the load condition.

The WHRB includes the following:

1. Preheater

2. L.P economizer

3. H.P economizer

4. L.P evaporator

5. H.P evaporator

6. L.P superheater

7. Two H.P superheater

8. L.P & H.P drum

9. L.P & H.P circulating pumps

10. Diverter damper

11. Weather protection damper

12. Bypass stack

13. Chimney

PREHEATER

It is used to raise the temperature of the water which is pumped by the condensate

extraction pumps (CEX) to the deaerater using the high temperature of the flue gases

and it is the last stage where the heat is extracted from the flue gases. Now the flue

gases are escaped to atmosphere.

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ECONOMIZER

Economizer is used to increase the temperature of water by absorbing heat from the flue

gases. Economizer used is of the welded fine tube type. For every 220 C reduction in flue

gas temperature by passing through an economiser or a pre-heater, there is 1% saving of

fuel in the boiler. In other words, for every 60 C rise in feed water temperature through

an economiser, or 200C rise in combustion air temperature through an air pre-heater.

ECONOMISER:-

DRUM

Water from economizer enters here as well as steam from evaporator enters here, so

drum contains both water and steam. Steam floats over water which is then taken out to

the superheater.

SUPERHEATER

Superheaters are meant to raise the steam temp. above the saturation temp. by

absorbing heat from the gas by increasing the temp. of the medium the useful energy

that can be recovered increasing thus the efficiency of cycle also increases.

DESUPERHEATERS

These are commonly used to reduce the superheated steam temp. as a means controlling

final superheated steam temp.

WEATHER DAMPER

It is used to protect the tubes of the exchanger from bad weather during the stoppages of

the boiler. Another effect of this damper is to keep a relative high temp. during short

drive stoppage of the boiler. It is between weather & the chimney.

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DIVERTER DAMPER

The diverter damper separates the gas turbine section with the boiler section. The

damper consists of a single flap which rotates about its horizontal axis. When the damper

is in closed condition the boiler portion is cut off and the plant runs in open condition.

When the damper is in open condition the plant runs in combined cycle since boiler

comes into play. The weight of the damper is 32 tons and is hydraulically operated.

Normal opening time : 70 sec

Normal closing time : 70sec

Emergency closing time: 20 sec

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STEAM TURBINE

The Steam Turbine is yet another important part of Kawas gas power plant. With the use

of boiler and then Steam Turbine makes the plant efficiency better.

At Kawas the Steam Turbine comprises of one High Pressure Turbine and one Low

Pressure Turbine. The HP turbine is single flow horizontal split type with 13 stages

whereas the LP turbine is double flow horizontal split type with 5 blades at each side.

There are 6 bearing although from High Pressure Turbine to generator. The output

megawatt of Steam Turbine is 116.6Mw at 11KV.

HP steam from superheater of both the two boilers of a block mixes and then some part

of the steam is passed to the deaerator, rest steam which is at 5230C and 170 bar

pressure is supplied to the HP Turbine. At the inlet of the HP turbine two stop valves as

well as two control valves are placed. The stop valve works just like a switch, fully

opened or fully closed, mainly used during emergency trip conditions. The control valve

is used to control the amount of steam entering the turbine and works on conventional

servo valve mechanism.

Various sensors are mounted on bearing number 1 i.e. before the HP turbine such as

vibration sensors to measure rotor and stator (casing) expansion, sensors for measuring

axial movement. Measurement of these parameters is very critical since the spacing

between rotor and stator is about 6mm.

At the 13 stage of the HP turbine the LP steam of both boilers is introduced. Now

because of same temperature and pressure both the steam mixes here and then passed

to LP turbine. The steam entering the LP turbine then flows in both the directions. This

steam after working in LP turbine is thus condensed in a condenser placed at the bottom

of LP turbine.

EMERGENCY TRIP CONDITION

Vacuum is maintained in the condenser using a vacuum pump. Special diaphragms and

vacuum breaker valves are provided to meet an emergency trip condition.

Under normal running conditions, the pressure inside the turbine is less than that of the

outside so the diaphragms well at required conditions. Whenever an emergency trip is

required the vacuum pump stops and pressure inside the turbine increases as compared

to the outside so the diaphragm moves upward and with the action of cutting blades all

the steam will move to the atmosphere. So, the Steam Turbine does not damage. Same

work is done by vacuum breakers.

HP AND LP BYPASS SYSTEM

After a trip when the system is again started then it is not possible to instantaneously get

a steam of 5230C and 170 bar. During the initial startup the temperature and pressure

remains low, so this steam cannot be feed to HP or LP turbine and therefore a by pass

system is used. Also whenever a trip in the system occurs then the stop valves remain

fully closed and the steam in the boiler is passed through this by pass system.

All the steam through this by pass system is send to the condenser but this high

temperature and pressure steam will damage the condenser vacuum, so this steam is

further cooled by water before entering the condenser. The control valve for HP and LP

by pass system works on actuator.

CONDENSOR AND HOTWELL

Condenser is the portion where the steam is condensed to water. Water from cooling

tower is pumped from Cooling Water (CW) pumps which are circulated through pipe in

condenser. When steam comes in contact with water it cools down and gets collected in

the hotwell. This circulating water is again pumped to cooling tower.

Water from hotwell is again pumped through condensate extraction pumps to preheater

and then deaerator.

KAWAS ELECTRICAL SYSTEMS

• Total station load is dependent on Station transformers 220 kV/6.6 kV, 24 MVA

each

• There are no UATs on generator terminals

• Power generated at 11.5 kV is stepped up directly to 220 kV

• Six 220 kV transmission lines connect Kawas to four grid substations of GEB

OPERATING VOLTAGES

TRANSMISSION VOLTAGE 220 KV

GENERATING VOLTAGE 11.5 KV

MEDIUM VOLTAGE 6.6KV

LOW VOLTAGE 415 V & 230 V

EMERGENCY LIGHTING 220 V DC

CONTROL & DC DRIVE 125 DC

CONTROL VOLTAGE 48 V DC

TURBO GENERATORS

A turbo generator is a turbine directly connected to an electric generator for the

generation of electric power.

GENERATOR DETAILS AT KAWAS

GENERATOR:

At KGPP there are 4 Nos. 134 MVA (for GT) and 2 nos. 145 MVA (for ST)

Synchronous Generators. These generators are 2 pole machines with a generating

frequency of 50 Hz. Generators are directly coupled with turbines. Major components of

the generators are:

Housing/Frame:

The frame is a single block. It holds by clamping the magnetic core along with

stator bars, their wedge and connections. The frame forms the outer casing of the turbo

generator.

Stator Magnetic Core:

The magnetic core is made up of a stack of special grain oriented magnetic steel

segments, or laminations. These laminations are characterised by their method of

manufacturing - cold rolling their low loss and high permeability, and their carlite

coating. Each segment is further insulated, with a thin coat of oil varnish containing

coiloidal slica.

Rotor Shaft:

The generator shaft is made of a single forging, whose ingot is made in an electric

furnace and then vacuum cast.

The steel used is a high fracture resistant alloy. The longitudinal slots which house the

fields coils are milled into the shaft body and are arranged so as to generate an magneto

motive force wave approaching a sine wave.

Stator Winding:

It is composed of conductors wedged into the magnetic core. It is in the winding that the

electrical energy is generated. There are two distinct parts of winding.

a) The straight part which is within the magnetic core.

b) The end windings which are outside the core and which serve to connect bars of

different slots, together, thereby completing the winding

Rotor winding:

The rotor winding which is unevenly arranged around the body, thus produces a dis

symmetry of inertia with respect to both of the main planes of the rotor. Slots milled

perpendicular to the axis of rotation restores this equilibrium. The rotor winding has two

distinct parts.

a) The part contained in the shaft body - the slot portion.

b) The part outside the shaft body - the end winding.

The rotor winding comprises a number of turns stacked inside the rotor slots and

which constitute the field coils which make up the poles of the rotor.

IMPORTANT POINTS:

• Gas turbine generator : 134 MVA - 4 No’s

• Steam turbine generator : 140 MVA - 2 No’s

• Air cooled, 3000 RPM, 2 pole, double star.

• Alsthom, France make.

• 11.5 kV generator terminal voltage.

• Four coolers in the generator for cooling the air.

RATED VOLTAGE 11.5 KV

RATED CURRENT 6740 AMPS

POWER FACTOR 0.8

EXCITATION VOLTAGE. 209 V DC

EXCITATION CURRENT. 1500 amps

GENERATOR COOLING AIR COOLED.

SUB-SYSTEM OF GENERATORS:

Prime mover

Excitation system/AVR

Generator transformer

Cooling system

Bearing

Prime mover:

The initial agent that transforms energy from thermal or pressure form to mechanical

form; typically an engine or turbine. The alternator based on the type of prime movers to

which they are mechanically coupled, may be classified as turbo generators, hydro-

generators, & engine driven generators. Turbo generators are driven by steam or gas

turbines. The efficiency of steam turbines is high at large speeds, and therefore,

synchronous machines driven by steam turbines (i.e. turbo generators) are high speed

machines.

The maximum speed of turbo-generators is 3000 rpm corresponding to 2 poles and 50 Hz

and it is widely used. These have small diameters (about 1.2m). Cylindrical rotor

construction is used as the salient pole construction is impractical owing to large

mechanical forces. The 4 pole construction with a speed of 1500 rpm is now obsolete.

They have greetings up to 1000 MVA.

Excitation system:

• Static & brushless excitation with rotating diodes on rotor.

• Shunt excitation with 11.5 kV excitation transformer.

• Excitation transformer is directly connected on generator busbars.

• Voltage regulation is done using thyristors.

• 125 Volts DC is for field flashing and boosting.

• The main exciter is directly mounted on the generator shaft.

• The exciter has field coils on the stator and armature on the rotor.

• Insulation - class –F, speed: 3000 rpm, I/P voltage – 45V, I/P current – 86A, O/P

voltage – 220V, O/P current – 1630A.

Generator Sectional Drawing

GENERATOR ROTOR

AVR (Automatic voltage regulation)

Output voltage is given to AVR which is connected to exciter. AVR gives command to

exciter which varies the excitation level to maintain output voltage constant (11.5kv).

There are various cards which are used to limit the parameters which can lead to

damage in generator.

Sr.n

o.

CARD APPLICATION

1. LUF2(+B4

6)

Flux limitation in generator and its auxiliaries (transformer & motor)

2. LSES(+B3

9)

Under excitation limitation which prevents loss of synchronization.

3. RCOSI(+B

51)

cosΦ regulation in generator.

4. RSI(+B58) Stator voltage regulator.

5. RPS(+B70

)

Regulation channel tracking.

6. SP1(+B77) Power stabilization. It dampers rotor oscillations.

7. LCSI(+B3

2)

Stator current limitation.

8. CMS(+C1

7)

Manual reference card. Stator voltage manual reference controls a

Current loop & regulates the excitation current.

9. RIEX(+C1

0)

Excitation current regulation.

10. CAS(+B27

)

Automatic set point.

11. COM1(+C

22)

Channel switching i.e. switching from automatic to manual channel

12. FITS(+C2

7)

Pulse generator

13. GITS(+C3

2)

Pulse generator. Generates the thyristor firing pulses so that the

rectified

Voltage is proportional to control voltage.

14. ASEX(+B1

0)

Excitation assistance. Firing pulses of the thyristors in the excitation

circuit which allows the generator to be excited by means of the

battery when the stator voltage

Exceeds its lower limit.

Generator transformer

The output generated by generator at 11.5kv is given to the transformer of capacity 140

MVA. Voltage is stepped up to 220kv by the transformer and is given to the main bus

through generator bay.

Important features are: -

1. Welded tank construction

2. Oil forced air forced cooling.

3. NVTC for voltage control (off load).

4. Yd11 configuration.

GT and Generator cooling system

• Fin fan coolers are available.

• 15 fans are for Generator and 15 are for GT.

• Normally 9 fans are in service.

• Other fans come in service automatically depending on temperature.

• Each fan is having 11 kW motor.

The generator is cooled using air cooling through water. Generator is cooled by air

through a fan. Water circulates at the ends of generator and when this air comes in

contact with water pipes, it becomes cool. Trip signal is given when water level is greater

than permissive level in generator. The water which becomes hot is then pumped to fin

fan coolers for cooling. Fresh Water is added to it for making up the water lost by

evaporation in this process.

Bearings

A bearing is a device to allow constrained relative motion between two or more parts,

typically rotation or linear movement.

There are 5 bearings for GT and 7 for ST.

There are three types of bearings

– Axial

– sliding

– Rolling.

Sliding bearing is further classified into journal and thrust bearings.

Turbine bearing is grounded because there is possibility of electrostatic charge to

develop as ions are present. Otherwise it will damage the whole bearing.

Generator bearing are grounded from end shield.

In accessories compartment journal cum thrust bearings.

In turbine we have elliptical journal and tilting pad journal bearing.

In generator we have journal bearing.

BLACK SET DIESEL GENERATOR

A diesel generator is the combination of a diesel engine with an electrical generator

(often called an alternator) to generate electric energy. Diesel generating sets are used

in places without connection to the power grid or as emergency power-supply if the grid

fails. Its capacity is 3MW, speed 1500 rpm and shell type core.

WRLDC has issued guidelines for grid restoration after a black out and identified stations

with black start facility:

Kawas, Jhanor, Uran, GIPCL, Ukai Hydro, Koyna Hydro Trombay Gas etc. are some of

these.

Events in a blackout:

• Gas Turbines get normal shutdown (fired s/d) on turbine under speed : setting 47.5

hz

• Electrical relays of generators (GT and ST) are set to 47.2 Hz and 1.2 Sec.

• Station transformer HV and MV breakers open on under voltage

• The liquid fuel forwarding pumps trip and all liquid fuel units will trip on loss of

flame

• The DC lube oil pumps will take start to prevent oil starvation to the bearings

• 220 kV transmission lines do not trip as they have no under frequency tripping.

They have to be hand tripped.

The restoration:

• The black start DG set (2.7 MW rating) starts on 6.6 kV under voltage and connects

automatically to both the 6.6 kV bus bars within 40 sec.

• The important Gas turbine and Steam turbine auxiliaries (Load : 1.5 MW) get

automatically restored as these transformers breakers do not trip.

• Unimportant loads like colony, simulator feeders etc., are cut off through load

shedding relay.

• Ensure that the essential auxiliaries of gas turbine and steam turbine are running.

• Give a start command to the GT running on gas after resetting primary and

secondary master trip relays of switchyard and LCR before the speed goes below

95%.

• In case the above is not possible, one gas turbine is started up on Gas fuel. The

load on the DG set at this time will include the cranking motor which is of 1MW

rating.

• The GT generator is connected to the 220 kV Bus in the Dead Bus charging mode.

• The Station transformers are charged and then further synchronized with the

BSDG at the 6.6 kV Busbars.

• The station load is taken on the station transformers by opening the BSDG incomer

breakers and DG is kept on FSNL.

• The CW pumps and the boiler feed pumps can be taken into service.

• Keep the frequency of the running unit at 50.5 Hz.

• Generator is again synchronized with grid in steps after rectification.

Kawas Electrical Schematic

220 kV 220 kV

Stn. Trf. 1 Stn. Trf. 2

Load

Bus coupler

Load

BSDG

6.6 kV Bus I 6.6 kV Bus II

Plant Auxiliaries

TRANSFORMERS

We have 4 types of transformers in NTPC

Generator transformer

• Three Phase, 140 MVA, Fuji make.

• Delta Star, neutral solidly grounded.

• Welded tank construction.

• Oil forced air forced cooling.

• NVTC for voltage control (off load).

• 9 cooling fans for each unit, 3 for each phase & 3 pumps for circulating oil.

Station transformer

• Three Phase, 24 MVA, Fuji make.

• Delta Star, neutral solidly grounded.

• Welded tank construction.

• Oil natural air natural cooling.

• OLTC for 6.6 kV Bus voltage control.

MV/LV transformers

• Alsthom make

• Oil filled hermetically sealed.

• Resin cast type.

Lighting transformers

• Resin cast dry type transformer.

• Delta star for providing neutral point to the lighting supplies.

• Also reduces the fault level on the lighting bus.

The various parts and protection systems of a transformer are:

1. Tank: - A suitable container for the assembled core and winding.

2. Transformer oil: - A suitable medium for insulating the core and winding

from its container.

3. Bushings: - (porcelain, oil filled, or condenser type) for insulating and

bringing out terminals of the windings

from the container.

4. Conservator tank: - to slow down deterioration of oil and keep the main tank

full of oil, emergency vent to relieve pressure inside the tank in case the

pressure inside the transformer rises to a danger point.

5. Breather: - the air entering the transformer is made moisture free by letting

it pass through breather. It consists of a small container connected to the vent

pipe and contains a dehydrating material like silica gel crystals impregnated

with cobalt chloride. It is blue when dry and whitish pink when damp.

6. Buchholz relay: - it is installed in the pipe joining the main tank of the

transformer & the conservator. It gives alarm to indicate the presence of gas

in case of some minor fault and take the transformer out of circuit in case of

serious fault. It is double float type with alarm and trip contacts, along with

suitable gas collecting device.

Below is its fig.

Buchholz relay -

OLTC Features

1. Local control, it has both manual and electrical control.

2. It can be operated by remote electrical control.

3. It has safety interlocks and protection.

DISSOLVED GAS ANALYSIS

It is for Preventive and Predictive Maintenance of transformers. It is done as follows:

• First sample immediately after charging

• Second sample after 15 days of charging

• Third sample after six month

• Every six month thereafter

These samples are tested and DGA level is determined. DGA committee takes

appropriate action on various transformers.

SWITCHYARD

Following are the main parts of switchyard in NTPC

• 2 Main Bus

• 1 Transfer bus

• 18 Bays :

– 6 Generator bays

– 8 Line bays ( 6 commissioned and 2 future)

– 2 Station transformer bays

– 1 Bus coupler bay

– 1 Bus transfer bay

There are two 220kv main bus each of capable of taking whole capacity of plant

(656.2MW).

Transfer bus is normally dead and is used in case any one of the bay is having fault.

It provides alternate path for the flow of power in case of fault. It can be used only if

one has to work on isolator and breaker of that bay.

A bay consists of 1 Circuit Breaker, 4 Isolator, 1 Current Transformer, 1 Capacitive

Voltage Transformer, 1 Lightning Arrestor, 2 earth switches.

Isolator

Isolator switch is used to make sure that an electrical circuit can be completely de-

energized for service or maintenance. It is 220KV isolator.

Circuit Breaker

The breakers have SF-6 as arc quenching medium and are hydraulically operated. The

SF-6 gas rated pressure

is 7.65 bar at 20°C and 1st stage low-pressure alarm is at 7.20 bar and 2nd stage low

pressure alarm is at 7.10

bar. Gas (SF6) circuit breakers sometimes stretch the arc using a magnetic field, and

then rely upon the

dielectric strength of the SF6 to quench the stretched arc.

SF6 is approximately 100 times more effective than air in quenching spurious arcing.

SF6 also has a high thermal

heat capacity that can absorb the energy of the arc without much of a temperature

rise.

Current Transformer

There are 3 types of CT:

• Hair Pin Design

• Eye Bolt Design

• Live tank Design

Core Material – The main aim is to give high accuracy with low saturation factor.

Core Material is made of

CRGO Silicon steel. For very low loss characteristics, µ material (Alloy of Ni-Fe) is

used.

Ratio:

Core 1: 1200-600/1 used for Main 1 protecion

Core 2 : 1200-600/1 used for Main 2 protection

Core 3: 1200-600/1 used for Metering.

Core 4: 1200/1 for Busbar protection Main zone.

Core 5: 1200/1 for Busbar protection Check zone.

Insulation levels - For Windings having Um(System Voltage) greater than 300kV, the

rated insulation level is determined by rated switching and lightning impulse

withstand voltage. For voltages < 300kV, insulation levels are decided by lightning

impulse and power-frequency withstand voltages.

Reasons of CT Failures - Moisture entry into solid insulation, Wrinkles in aluminum

grading, Opening of secondary winding, Opening of tan delta point, Dielectric failure

due to pre-mature ageing, Other dielectric failures due to improper wrapping of

paper, improper flux distribution etc.

Capacitive Voltage Transformer

Basic circuit is shown below:

Compensating Reactor is provided to compensate for the phase displacement in

Capacitor elements

ωL = 1/ω (C1+C2)

L = 1/ ω 2 (C1+C2)

Ferro resonance in CVTs is due to the Capacitance in Voltage Divider in series with

the inductance of the Transformer and series reactor. This circuit is brought to

resonance by various disturbances in the network that may saturate the iron core of

the transformer, over heat electro magnetic unit and lead to insulation breakdown.

Ferro resonance circuit is provided in CVT Secondary to suppress Ferro resonance

oscillations. There can be active or passive Ferro resonance circuits. It can be RLC

circuit (ABB make CVTs) or RL circuit (CGL, BHEL CVTs).

VA ratings for core-1, core-2 and core-3 are generally 200VA, 200VA and 100VA

respectively. CVT accuracies are guaranteed if connected burdens are within 25% to

100% of the rated burdens.

Change in Capacitance value above 6%, CVT need to be replaced. Tan delta values

more than 0.003 from pre-commissioning value needs replacement.

Reasons for Failure of CVTs – wrinkles on aluminum foils, Poor soldering qualities,

rusting of coupling bolts, shorting of transformer cores, entry of moisture in

capacitor stacks, looseness of core bolts, overheating of damping resistor etc.

Lightning Arrestor

LAs are available at 336kV, 360kV, 372kV and 390kV. Higher ratings are selected

taking into consideration of

ageing of LA elements.

During single phase to ground fault, voltage on healthy phase may go upto 1.4 to 1.5

times

230 x 1.4/1.5 = 323 – 346

Temporary O/V = 1.5 pu = 336kV

Discharge voltage: 945 kV

Hence surge arrestors are placed to ground the overvoltage. It also grounds the

current due to lightning.

These are made by mixing ZnO with small amount of additives such as Bi2O3, CoO,

Cr2O3, MnO and Sb2.O3

ZnO grains (about 10μm dia) have low resistivity and surrounded by a granular layer

which is a high resistive Oxide layer(0.1 μm thick). The two are strongly bonded.

For protecting generator unit it is placed after transformers and for protecting lines

it is placed after CVT.

Lightning Arrestor drives a small magnitude of leakage current under the continuous

operating voltage i.e. leakage current. It increases with time and results in ageing of

LA. It can also lead to thermal runaway.

Ageing of Surge Arresters -

1. Normal Operating Voltage causes ageing of ZnO Blocks

2. Temporary O/V, Switching O/V and Lightning O/V may cause overloading of all or

some of the ZnO blocks

3. External Pollution may cause non-linear voltage distribution. Accelerated ageing

caused by internal PDs

4. Moisture Entry through sealing gaskets, may lead to shorting of ZnO discs and

overstressing of healthy ZnO blocks.

5. The degree of ageing depends on the nature/ quality of the granular layer.

6. The increase in Resistive Leakage Current may bring the arrester to Thermal

instability and complete Arrester Breakdown.

Earth switch

For operating on a bay it is necessary that earth switch should be closed as there is

high induction due power flow in surrounding bays.

The figure shows the busbar schemes. Any bay can be connected to either bus1 or bus2

by isolator 1 & 2. There is a breaker in each bay which is hydraulically operated.

Isolator 4 allows the transmission of the power of any bay through transfer bus in case

there is fault in that bay. Only one bay can be switched to transfer bus at a time.

Transfer bay is used to charge the transfer bus from main bus for providing the

alternate path of power flow as described above. Bus coupler is used to couple the two

buses for maintaining both at constant voltage otherwise unnecessary circulating

current will be developed which will cause overheating.

Bus Switching Schemes

6 Generators

2 Stn.transformers

Bus Coupler

Transfer Bay

8 Transmission lines

Transfer Bus

Main Bus-1

Main Bus-2

Double main and Transfer bus scheme

These are the transmission lines from NTPC grid.

Kawas 220 kV transmission system

KawasHaldarva

Navsari

Vav

Ichhapore

Essar Reliance

Sachin

LINE DIAGRAM OF SWITCHYARD

Electrical Protections

• Generator and transformer protections

• 6.6 kV Protections

– Station transformer protections

– Motor protections

– Transformer protections

• 220 kV Protections

– Line protections

– Busbar protection

– Breaker failure protection

Zones of protectionGenerator Protn.

Transformer Protn.

Overall Gen. Trf. Protn.

Line Protn.

Busbar Protn.

Transformer Protn.

Generator Protections

• Generator Differential Protection

• Generator Stator earthfault protection 100%

• Generator Stator earthfault protection 95%

• Generator rotor earth fault protection

• Overall differential protection

• Transformer restricted earth fault protection

• Generator Transformer Over fluxing relay

• Generator reverse power relay

• Backup impedance relay

• Generator Loss of excitation protection

• Generator Negative phase sequence current protection

• Stator Over voltage protection

• Stator Under voltage protection

• Under frequency relay

• Voltage balance relay

• Too long field flashing protection.

• Protection against back energization

• Protection against DC failure

• The diode matrix

6.6kV Protections

• Station transformer protections

– Three phase Overcurrent protection.

– Earthfault protection.

– Restricted earth fault protection.

• Motor protection

– IDMT over current protection

– Earthfault protection

• Transformer protection

– IDMT over current protection

– Earthfault protection

220 kV protections

Line protections

• Main I Distance protection (21-1)

• Main II Distance protection (21-2)

• Breaker failure relay.

• Trip circuit supervision relay

• Trip coil supervision relay.

• Fault locator

• Disturbance recorder

220 kV Transformer protections

• Transformer Differential protection.(87)

• Three phase overcurrent protection. (51)

• Earth fault relay (Phase current balance)

• Breaker failure relay.

• Bucholz relay

• Winding temperature relay

• Oil temperature relay

• Pressure relief device

•

Busbar protection

• Differential protection

• To protect against fault on main bus bars and the transfer bus.

• Bus I zone differential relay

• Bus II zone differential relay

• Check zone relay

Breaker failure protection

• To protect against circuit breaker malfunctions

• Gives command to trip the 220 kV busbar on which the equipment is connected

when:

– Trip command is existing from any relay and

– Current has not died out even after 200 ms.

SWAS

In KGPP, the SWAS room located nearby the boiler contains all the type of the analyzers.

SWAS stands for Steam and Water Analysis System. SWAS is mainly used to check the

healthiness of steam turbine and boiler. As the name indicates, the water and steam

samples belonging to the boilers are tested here first for different composition of

chemicals for better and pollution free production. Analyzers like NOx analyzers, Na

analyzers, Hydrazine analyzer, Dissolved O2 analyzers, Water pH meters, silica analyzers,

Water conductivity meters etc. are mounted in the SWAS room, which are described

briefly below:

1. NOX ANALYZER:-

NOx analyzer is used for the detection of the nitrous components detection.

2. SILICA ANALYZER:-

The hetropoly blue method is used to measure molybdate-reactive silica.

3. O2 ANALYZER:-

The universal demand for oxygen analysis due to its essential role in oxidation,

combustion and industrial processing applications has led to a large number of varied

techniques applied to process analyzers. Among them, at KGPP, we use the dissolved

oxygen analyzer which is as under.

4. CONDUCTIVITY ANALYZER:-

Conductivity is the reciprocal of resistivity. Its unit is mho. Conductivity of water

depends upon the dissolved salts like CaSO4, MgSO4, etc. These salts result in scale

formation in pipes. Therefore we measure conductivity of water and try to reduce it.

5. SODIUM ANALYZER:-

In chlorination plant, chlorine is being used. If it is mixed with sodium, NaCl salt will

form which may deposit in the pipes and scale formation will take place. So we have

to remove it. Sodium analyzer cell contains Na electrode which is placed in NaCl

solution. One glass membrane is in direct contact with sample water and generates

mV which is proportional to the amount of Na present in the water sample. It is also

temperature dependent so temperature compensation is used.

6. pH METER:-

pH meter is used for measurement of pH of the water. How much hydroxyl ion does

the water contains is known by measuring pH. pH of normal water is 7, pH < 7 is

known as acidic liquid & pH > 7 is known as basic solution. For process acidic

solution is not proper so ph meter is necessary.

All these analyzers are manufactured by the ABB, KENT.