1

ABOUT NTPC

India‟s largest power company, NTPC was set up in 1975 to accelerate power

development in India. NTPC is emerging as a diversified power major with presence in

the entire value chain of the power generation business. Apart from power generation,

which is the mainstay of the company, NTPC has already ventured into consultancy,

power trading, ash utilization and coal mining. NTPC ranked 341st in the „2010, Forbes

Global 2000‟ ranking of the World‟s biggest companies. NTPC became a Maharatna

company in May, 2010, one of the only four companies to be awarded this status.

The total installed capacity of the company is 39,174 MW (including JVs) with 16 coal

based and 7 gas based stations, located across the country. In addition under JVs, 7

stations are coal based & another station uses naptha/LNG as fuel. The company has set

a target to have an installed power generating capacity of 1,28,000 MW by the year 2032.

The capacity will have a diversified fuel mix comprising 56% coal, 16% Gas, 11%

Nuclear and 17% Renewable Energy Sources(RES) including hydro. By 2032, non-fossil

fuel based generation capacity shall make up nearly 28% of NTPC‟s portfolio.

NTPC has been operating its plants at high efficiency levels. Although the company has

17.75% of the total national capacity, it contributes 27.40% of total power generation due

to its focus on high efficiency.

2

In October 2004, NTPC launched its Initial Public Offering (IPO) consisting of 5.25% as

fresh issue and 5.25% as offer for sale by Government of India. NTPC thus became a

listed company in November 2004 with the Government holding 89.5% of the equity

share capital. In February 2010, the Shareholding of Government of India was reduced

from 89.5% to 84.5% through Further Public Offer. The rest is held by Institutional

Investors and the Public.

3

Strategies of NTPC

Technological Initiatives

Introduction of steam generators (boilers) of the size of 800 MW.

Integrated Gasification Combined Cycle (IGCC) Technology.

Launch of Energy Technology Centre -A new initiative for development

of technologies with focus on fundamental R&D.

The company sets aside up to 0.5% of the profits for R&D.

Roadmap developed for adopting µClean Development.

Mechanism to help get / earn µCertified Emission Reduction.

4

Corporate Social Responsibility

As a responsible corporate citizen NTPC has taken up number of CSR initiatives.

NTPC Foundation formed to address Social issues at national level

NTPC has framed Corporate Social Responsibility Guidelines committing up

to0.5% of net profit annually for Community Welfare.

The welfare of project affected persons and the local population around

NTPC projects are taken care of through well drawn Rehabilitation and

Resettlement policies.

The company has also taken up distributed generation for remote rural areas

Partnering government in various initiatives

Consultant role to modernize and improvise several plants across the country.

Disseminate technologies to other players in the sector.

Consultant role ³Partnership in Excellence´ Programme for improvement of

PLF of 15 Power Stations of SEBs.

Rural Electrification work under Rajiv Gandhi Garmin Vidyutikaran.

Environment management

All stations of NTPC are ISO 14001 certified.

Various groups to care of environmental issues.

The Environment Management Group.

Ash tilization Division.

Afforestation Group.

Centre for Power Efficiency & Environment Protection.

Group on Clean Development Mechanism.

NTPC is the second largest owner of trees in the country after the

Forest department

5

Vision

“To be the world‟s largest and best power producer, powering India‟s growth.”

Mission

“Develop and provide reliable power, related products and services at competitive

prices, integrating multiple energy sources with innovative and eco-friendly

technologies and contribute to society.”

Core Values – BE COMMITTED

B Business Ethics

E Environmentally & Economically Sustainable

C Customer Focus

O Organizational & Professional Pride

M Mutual Respect & Trust

M Motivating Self & others

I Innovation & Speed

T Total Quality for Excellence

T Transparent & Respected Organization

E Enterprising

D Devoted

6

JOURNEY OF NTPC

7

NTPC Environment Policy

NTPC is committed to the environment, generating power at minimal environmental cost

and preserving the ecology in the vicinity of the plants. NTPC has undertaken massive a

forestation in the vicinity of its plants. Plantations have increased forest area and reduced

barren land. The massive a forestation by NTPC in and around its Ramagundam Power

station (2600 MW) have contributed reducing the temperature in the areas by about 3°c.

NTPC has also taken proactive steps for ash utilization. In 1991, it set up Ash Utilization

Division A

"Centre for Power Efficiency and Environment Protection- CENPEE" has been

established in NTPC with the assistance of United States Agency for International

Development- USAID. CENPEEP is efficiency oriented, eco-friendly and eco-nurturing

initiative - a symbol of NTPC's concern towards environmental protection and continued

commitment to sustainable power development in India. As a responsible corporate

citizen, NTPC is making constant efforts to improve the socio-economic status of

the people affected by its projects. Through its Rehabilitation and Resettlement

programmes, the company endeavors to improve the overall socio economic status

Project Affected Persons. NTPC was among the first Public Sector Enterprises to enter

into a Memorandum of Understanding-MOU with the Government in 1987-88. NTPC

has been placed under the 'Excellent category' (the best category) every year since the

MOU system became operative. Harmony between man and environment is the essence

of healthy life and growth. Therefore, maintenance of ecological balance and a pristine

environment has been of utmost importance to NTPC. It has been taking

various measures discussed below for mitigation of environment pollution due to power

generation.

NTPC is the second largest owner of trees in the country after the Forest department.

8

As early as in November 1995, NTPC brought out a comprehensive document entitled

"NTPC Environment Policy and Environment Management System". Amongst the

guiding principles adopted in the document is company‟s proactive approach to

environment, optimum utilization of equipment, adoption of latest technologies and

continual environment improvement. The policy also envisages efficient utilization of

resources, thereby minimizing waste, maximizing ash utilization and providing green belt

all around the plant for maintaining ecological balance.

Environment Management, Occupational Health and Safety Systems:

NTPC has actively gone for adoption of best international practices on environment,

occupational health and safety areas. The organization has pursued the Environmental

Management System (EMS) ISO 14001 and the Occupational Health and Safety

Assessment System OHSAS 18001 at its different establishments. As a result of pursuing

these practices, all NTPC power stations have been certified for ISO 14001 & OHSAS

18001 by reputed national and international Certifying Agencies.

Pollution Control systems:

While deciding the appropriate technology for its projects, NTPC integrates many

environmental provisions into the plant design. In order to ensure that NTPC complies

with all the stipulated environment norms, various state-of-the-art pollution control

systems / devices as discussed below have been installed to control air and water

pollution.

Electrostatic Precipitators:

The ash left behind after combustion of coal is arrested in high efficiency Electrostatic

Precipitators (ESPs) and particulate emission is controlled well within the stipulated

norms. The ash collected in the ESPs is disposed to Ash Ponds in slurry form.

9

Flue Gas Stacks:

Tall Flue Gas Stacks have been provided for wide dispersion of the gaseous emissions

(SOX, NOX etc.) into the atmosphere.

Low-NOX Burners:

In gas based NTPC power stations, NOX emissions are controlled by provision of Low-

NOX Burners (Dry or wet type) and in coal fired stations, by adopting best combustion

practices.

Neutralization Pits:

Neutralization pits have been provided in the Water Treatment Plant (WTP) for pH

correction of the Effluents before discharge into Effluent Treatment Plant (ETP) for

further treatment and use.

Coal Settling Pits / Oil Settling Pits:

In these Pits, coal dust and oil are removed from the effluents emanating from the Coal

Handling Plant (CHP), coal yard and Fuel Oil Handling areas before discharge into ETP.

DE & DS Systems:

Dust Extraction (DE) and Dust Suppression (DS) systems have been installed in all coal

fired power stations in NTPC to contain and extract the fugitive dust released in the Coal

Handling Plant (CHP).

Cooling Towers:

Cooling Towers have been provided for cooling the hot Condenser cooling water in

closed cycle, Condenser Cooling Water (CCW) Systems. This helps in reduction in

thermal pollution and conservation of fresh water.

10

Ash Dykes & Ash Disposal systems:

Ash ponds have been provided at all coal based stations except Dadri where Dry Ash

Disposal System has been provided. Ash Ponds have been divided into lagoons and

provided with garlanding arrangement for changeover of the ash slurry feed points for

even filling of the pond and for effective settlement of the ash particles.

Ash in slurry form is discharged into the lagoons where ash particles get settled from the

slurry and clear effluent water is discharged from the ash pond. The discharged effluents

conform to standards specified by CPCB and the same is regularly monitored.

At its Dadri Power Station, NTPC has set up a unique system for dry ash collection and

disposal facility with Ash Mound formation. This has been envisaged for the first time in

Asia which has resulted in progressive development of green belt besides far less

requirement of land and less water requirement as compared to the wet ash disposal

system.

Ash Water Recycling System:

Further, in a number of NTPC stations, as a proactive measure, Ash Water Recycling

System (AWRS) has been provided. In the AWRS, the effluent from ash pond is

circulated back to the station for further ash sluicing to the ash pond. This helps in

savings of fresh water requirements for transportation of ash from the plant.

The ash water recycling system has already been installed and is in operation at

Ramagundam, Simhadri, Rihand, Talcher Kaniha, Talcher Thermal, Kahalgaon, Korba

and Vindhyachal. The scheme has helped stations to save huge quantity of fresh water

required as make-up water for disposal of ash.

Dry Ash Extraction System (DAES):

Dry ash has much higher utilization potential in ash-based products (such as bricks,

aerated autoclaved concrete blocks, concrete, Portland pozzolana cement, etc.). DAES

has been installed at Unchahar, Dadri, Simhadri, Ramagundam, Singrauli, Kahalgaon,

Farakka, Talcher Thermal, Korba, Vindhyachal, Talcher Kaniha and BTPS.

11

Liquid Waste Treatment Plants & Management System:

The objective of industrial liquid effluent treatment plant (ETP) is to discharge lesser and

cleaner effluent from the power plants to meet environmental regulations. After primary

treatment at the source of their generation, the effluents are sent to the ETP for further

treatment. The composite liquid effluent treatment plant has been designed to treat all

liquid effluents which originate within the power station e.g. Water Treatment Plant

(WTP), Condensate Polishing Unit (CPU) effluent, Coal Handling Plant (CHP) effluent,

floor washings, service water drains etc. The scheme involves collection of various

effluents and their appropriate treatment centrally and re-circulation of the treated

effluent for various plant uses.

NTPC has implemented such systems in a number of its power stations such as

Ramagundam, Simhadri, Kayamkulam, Singrauli, Rihand, Vindhyachal, Korba, Jhanor

Gandhar, Faridabad, Farakka, Kahalgaon and Talcher Kaniha. These plants have helped

to control quality and quantity of the effluents discharged from the stations.

Sewage Treatment Plants & Facilities:

Sewage Treatment Plants (STPs) sewage treatment facilities have been provided at all

NTPC stations to take care of Sewage Effluent from Plant and township areas. In a

number of NTPC projects modern type STPs with Clarifloculators, Mechanical Agitators,

sludge drying beds, Gas Collection Chambers etc. have been provided to improve the

effluent quality. The effluent quality is monitored regularly and treated effluent

conforming to the prescribed limit is discharged from the station. At several stations

treated effluents of STPs are being used for horticulture purpose.

12

ABOUT BTPS

BADARPUR THERMAL POWER STATION was established on 1973 and it was the

part of Central Government. On 01/04/1978 is was given as No Loss No Profit Plant of

NTPC. Since then operating performance of NTPC has been considerably above the

national average. The availability factor for coal stations has increased from 85.03 % in

1997-98 to 90.09 % in 2006-07, which compares favorably with international standards.

The PLF has increased from 75.2% in1997-98 to 89.4% during the year 2006-07 which is

the highest since the inception of NTPC.

Badarpur thermal power station started with a single 95 mw unit. There were 2 more units

(95 MW each) installed in next 2 consecutive years. Now it has total five units with total capacity of

720 MW. Ownership of BTPS was transferred to NTPC with effect from 01.06.2006 through

GOIs Gazette Notification .

The power is supplied to a 220 KV network that is a part of the northern grid. The ten

circuits through which the power is evacuated from the plant are:

1. Mehrauli

2. Okhla

3. Ballabgarh

4. Indraprastha

5. UP (Noida)

6. Jaipur

13

Given below are the details of unit with the year they’re installed.

14

Station Location

Badarpur is situated only 20 km away from Delhi. The plant is located on the left side of the National

Highway (Delhi-Mathura Road) and it comprises of 430 hectares (678 acres) bordered by the Agra

Canal from East and by Mathura-Delhi Road from West. However, the area for ash

disposal is done in the Delhi Municipal limit and is maintained with the help of Delhi Development

Authority. The plant is also close to the project of 220 kv Double Circuit Transmission line between the

I.P. station and Ballabgarh Cooling Water is obtained from Agra Canal for the cooling

system. Additional 60 cusecs channel has also been constructed parallel to the Agra

Canal so as to obtain uninterrupted water supply during the slit removing operation in

Agra Canal.

15

OPERATION OF A POWER PLANT

Basic Principle

As per FARADAY‟s Law-“Whenever the amount of magnetic flux linked with a circuit

changes, an EMF is produced in the circuit. Generator works on the principle of

producing electricity. To change the flux in the generator turbine is moved in a great

speed with steam.” To produce steam, water is heated in the boilers by burning the coal.

In a Badarpur Thermal PowerStation, steam is produced and used to spin a turbine that

operates a generator. Water is heated, turns into steam and spins a steam turbine which

drives an electrical generator. After it passes through the turbine, the steam is condensed

in a condenser; this is known as a Rankine cycle.

The electricity generated at the plant is sent to consumers through high-voltage power

lines The Badarpur Thermal Power Plant has Steam Turbine-Driven Generators which

has a collective capacity of 705MW. The fuel being used is Coal which is supplied from

the Jharia Coal Field in Jharkhand. Water supply is given from the Agra Canal.

16

Basic Steps of Electricity Generation

The basic steps in the generation of electricity from coal involves following steps:

Coal to steam

Steam to mechanical power

Mechanical power to electrical power

17

Coal to Electricity : Basics

18

19

20

PARTS OF A POWER PLANT

The various parts are listed below:-

1. Cooling tower

2. Cooling water pump

3. Transmission line (3-phase)

4. Unit transformer (3-phase)

5. Electric generator (3-phase)

6. Low pressure turbine

7. Condensate extraction pump

8. Condenser

9. Intermediate pressure turbine

10. Steam governor valve

11. High pressure turbine

21

12. Deaerator

13. Feed heater

14. Coal conveyor

15. Coal hopper

16. Pulverised fuel mill

17. Boiler drum

18. Ash hopper

19. Super heater

20. Forced draught fan

21. Reheater

22. Air intake

23. Economiser

24. Air preheater

25. Precipitator

26. Induced draught fan

27. Flue Gas

1. Cooling Tower

Cooling towers are heat removal devices used to transfer process waste heat to the

atmosphere. Cooling towers may either use the evaporation of water to remove process

heat and cool the working fluid to near the wet-bulb air temperature or in the case of

closed circuit dry cooling towers rely solely on air to cool the working fluid to near the

dry-bulb air temperature. Common applications include cooling the circulating water

used in oil refineries, chemical plants, power stations and building cooling.

The towers vary in size from small roof-top units to very large hyperboloid structures that

can be up to 200 meters tall and 100 meters in diameter, or rectangular structures that can

be over 40 meters tall and 80 meters long. Smaller towers are normally factory-built,

while larger ones are constructed on site. The absorbed heat is rejected to the atmosphere

by the evaporation of some of the cooling water in mechanical forced-draft or induced

22

Draft towers or in natural draft hyperbolic shaped cooling towers as seen at most nuclear

power plants.

2. Cooling Water Pump

it pumps the water from the cooling tower which goes to the condenser.

3. Three phase transmission line

Three phase electric power is a common method of electric power transmission. It is a

type of polyphase system mainly used to power motors and many other devices. A three

phase system uses less conductive material to transmit electric power than equivalent

single phase, two phase, or direct current system at the same voltage. In a three phase

system, three circuits reach their instantaneous peak values at different times.

Taking current in one conductor as the reference, the currents in the other two are delayed

in time by one-third and two-third of one cycle .This delay between “phases” has the

effect of giving constant power transfer over each cycle of the current and also makes it

possible to produce a rotating magnetic field in an electric motor. At the power station, an

electric generator converts mechanical power into a set of electric currents, one from each

electromagnetic coil or winding of the generator.

The current are sinusoidal functions of time, all at the same frequency but offset in time

to give different phases. In a three phase system the phases are spaced equally, giving a

phase separation of one-third of one cycle. Generators output at a voltage that ranges

from hundreds of volts to 30,000 volts.

4. Unit transformer (3-phase)

At the power station, transformers step-up this voltage to one more suitable for

transmission. After numerous further conversions in the transmission and distribution

network the power is finally transformed to the standard mains voltage (i.e. the

“household” voltage). The power may already have been split into single phase at this

point or it may still be three phase. Where the step-down is 3 phase, the output of this

transformer is usually star connected with the standard mains voltage being the phase-

23

neutral voltage. Another system commonly seen in North America is to have a delta

connected secondary with a center tap on one of the windings supplying the ground and

neutral.

This allows for 240 V three phase as well as three different single phase voltages( 120 V

between two of the phases and neutral , 208 V between the third phase ( or wild leg) and

neutral and 240 V between any two phase) to be available from the same supply.

5. Electrical generator

An Electrical generator is a device that converts kinetic energy to electrical energy,

generally using electromagnetic induction. The task of converting the electrical energy

into mechanical energy is accomplished by using a motor. The source of mechanical

energy maybe water falling through the turbine or steam turning a turbine (as is the case

with thermal power plants). There are several classifications for modern steam turbines.

Steam turbines are used in our entire major coal fired power stations to drive the

generators or alternators, which produce electricity. The turbines themselves are driven

by steam generated in "boilers “or "steam generators" as they are sometimes called.

Electrical power stations use large steam turbines driving electric generators to produce

most (about 86%) of the world‟s electricity. These centralized stations are of two types:

fossil fuel power plants and nuclear power plants. The turbines used for electric power

generation are most often directly coupled to their-generators .As the generators must

rotate at constant synchronous speeds according to the frequency of the electric power

system, the most common speeds are 3000 r/min for 50 Hz systems, and 3600 r/min for

60 Hz systems. Most large nuclear sets rotate at half those speeds, and have a 4-pole

generator rather than the more common 2-pole one.

6. Low Pressure Turbine

Energy in the steam after it leaves the boiler is converted into rotational energy as it

passes through the turbine. The turbine normally consists of several stages with each

stages consisting of a stationary blade (or nozzle) and a rotating blade. Stationary blades

convert the potential energy of the steam into kinetic energy and direct the flow onto the

24

rotating blades. The rotating blades convert the kinetic energy into impulse and reaction

forces, caused by pressure drop, which results in the rotation of the turbine shaft. The

turbine shaft is connected to a generator, which produces the electrical energy.

Low Pressure Turbine (LPT) consists of 4x2 stages. After passing through Intermediate

Pressure Turbine steam is passed through LPT which is made up of two parts- LPC

REAR & LPC FRONT. As water gets cooler here it gathers into a HOTWELL placed in

lower parts of turbine.

7. Condensation Extraction Pump

A Boiler feed water pump is a specific type of pump used to pump water into a steam

boiler. The water may be freshly supplied or returning condensation of the steam

produced by the boiler. These pumps are normally high pressure units that use suction

from a condensate return system and can be of the centrifugal pump type or positive

displacement type.

Construction and operation:

Feed water pumps range in size up to many horsepower and the electric motor is usually

separated from the pump body by some form of mechanical coupling. Large industrial

condensate pumps may also serve as the feed water pump. In either case, to force the

water into the boiler, the pump must generate sufficient pressure to overcome the steam

pressure developed by the boiler. This is usually accomplished through the use of a

centrifugal pump. Feed water pumps usually run intermittently and are controlled by a

float switch or other similar level-sensing device energizing the pump when it detects a

lowered liquid level in the boiler. Some pumps contain a two-stage switch. As liquid

lowers to the trigger point of the first stage, the pump is activated. If the liquid continues

to drop, (perhaps because the pump has failed, its supply has been cut off or exhausted, or

its discharge is blocked) the second stage will be triggered. This stage may switch off the

boiler equipment (preventing the boiler from running dry and overheating), trigger an

alarm, or both.

25

8. Condenser

The steam coming out from the Low Pressure Turbine (a little above its boiling pump) is

brought into thermal contact with cold water (pumped in from the cooling tower) in the

condenser, where it condenses rapidly back into water, creating near Vacuum-like

conditions inside the condenser chest.

9. Intermediate Pressure Turbine

Intermediate Pressure Turbine (IPT) consists of 11 stages. When the steam has been

passed through HPT it enters into IPT. IPT has two ends named as FRONT & REAR.

Steam enters through front end and leaves from Rear end.

10. Steam Governor Valve

Steam locomotives and the steam engines used on ships and stationary applications such

as power plants also required feed water pumps. In this situation, though, the pump was

often powered using a small steam engine that ran using the steam produced by the boiler

a means had to be provided, of course, to put the initial charge of water into the boiler

(before steam power was available to operate the steam-powered feed water pump).The

pump was often a positive displacement pump that had steam valves and cylinders at one

end and feed water cylinders at the other end; no crankshaft was required. In thermal

plants, the primary purpose of surface condenser is to condense the exhaust steam from a

steam turbine to obtain maximum efficiency and also to convert the turbine exhaust

steam into pure water so that it may be reused in the steam generator or boiler as boiler

feed water. By condensing the exhaust steam of a turbine at a pressure below atmospheric

pressure, the steam pressure drop between the inlet and exhaust of the turbine is

increased, which increases the amount heat available for conversion to mechanical

power. Most of the heat liberated due to condensation of the exhaust steam is carried

away by the cooling medium (water or air) used by the surface condenser. Control valves

are valves used within industrial plants and elsewhere to control operating conditions

such as temperature, pressure, flow and liquid level by fully or partially opening or

closing in response to signals received from controllers that compares a “set point” to a

26

“process variable” whose value is provided by sensors that monitor changes in such

conditions. The opening or closing of control valves is done by means of electrical,

hydraulic or pneumatic systems.

11.High Pressure Turbine

Steam coming from Boiler directly feeds into HPT at a temperature of 540°C and at a

pressure of 136 kg/cm2. Here it passes through 12 different stages due to which its

temperature goes down to 329°C and pressure as 27 kg/cm2. This line is also called as

CRH – COLD REHEAT LINE. It is now passed to a REHEATER where its temperature

rises to 540°C and called as HRH-HOT REHEATED LINE.

12. Deaerator

A Deaerator is a device for air removal and used to remove dissolved gases (an alternate

would be the use of water treatment chemicals) from boiler feed water to make it non-

corrosive. A dearator typically includes a vertical domed deaeration section as the

deaeration boiler feed water tank. A Steam generating boiler requires that the circulating

steam, condensate, and feed water should be devoid of dissolved gases, particularly

corrosive ones and dissolved or suspended solids. The gases will give rise to corrosion of

the metal. The solids will deposit on the heating surfaces giving rise to localized heating

and tube ruptures due to overheating. Under some conditions it may give rise to stress

corrosion cracking. Deaerator level and pressure must be controlled by adjusting control

valves the level by regulating condensate flow and the pressure by regulating steam flow.

If operated properly, most deaerator vendors will guarantee that oxygen in the deaerated

water will not exceed 7 ppb by weight (0.005 cm3/L)

13. Feed water heater

A Feed water heater is a power plant component used to pre-heat water delivered to a

steam generating boiler. Preheating the feed water reduces the irreversibility involved in

steam generation and therefore improves the thermodynamic efficiency of the system.

This reduces plant operating costs and also helps to avoid thermal shock to the boiler

27

metal when the feed water is introduced back into the steam cycle. In a steam power

(usually modelled as a modified Rankine cycle), feed water heaters allow the feed water

to be brought up to the saturation temperature very gradually. This minimizes the

inevitable irreversibility associated with heat transfer to the working fluid (water).

14. Coal conveyor

Coal conveyors are belts which are used to transfer coal from its storage place to Coal

Hopper. A belt conveyor consists of two pulleys, with a continuous loop of material- the

conveyor Belt – that rotates about them. The pulleys are powered, moving the belt and

the material on the belt forward.

Conveyor belts are extensively used to transport industrial and agricultural material, such

as grain, coal, ores etc.

15. Coal Hopper

Coal Hoppers are the places which are used to feed coal to Fuel Mill. It also has the

arrangement of entering Hot Air at 200°C inside it which solves our two purposes:-

1. If our Coal has moisture content then it dries it so that a proper combustion takes place.

2. It raises the temperature of coal so that its temperature is more near to its Ignite

Temperature so that combustion is easy.

16. Pulverized Fuel Mill

A pulveriser is a device for grinding coal for combustion in a furnace in a fossil fuel

power plant.

17. Boiler drum

Steam Drums are a regular feature of water tube boilers. It is reservoir of water/steam at

the top end of the water tubes in the water-tube boiler. They store the steam generated in

the water tubes and act as a phase separator for the steam/water mixture. The difference

in densities between hot and cold water helps in the accumulation of the “hotter”-

water/and saturated –steam into steam drum. Made from high-grade steel (probably

28

stainless) and its working involve temperature of 390°C and pressure well above 350psi

(2.4MPa). The separated steam is drawn out from the top section of the drum.

Saturated steam is drawn off the top of the drum. The steam will re-enter the furnace in

through a super heater, while the saturated water at the bottom of steam drum flows down

to the mud-drum /feed water drum by down comer tubes accessories include a safety

valve, water level indicator and fuse plug.

18. Ash Hopper

A steam drum is used in the company of a mud-drum/feed water drum which is located at

a lower level.

So that it acts as a sump for the sludge or sediments which have a tendency to accumulate

at the bottom.

19. Super Heater

A Super heater is a device in a steam engine that heats the steam generated by the boiler

again increasing its thermal energy. Super heaters increase the efficiency of the steam

engine, and were widely adopted. Steam which has been superheated is logically known

as superheated steam; non- superheated steam is called saturated steam or wet steam.

Super heaters were applied to steam locomotives in quantity from the early 20th century,

to most steam vehicles, and also stationary steam engines including power stations.

20. Force Draught Fan

External fans are provided to give sufficient air for combustion. The forced draught fan

takes air from the atmosphere and, warms it in the air preheater for better combustion,

injects it via the air nozzles on the furnace wall.

21. Reheater

Reheater is a heater which is used to raise the temperature of steam which has fallen from

the intermediate pressure turbine.

29

22. Air Intake

Air is taken from the environment by an air intake tower which is fed to the fuel.

23. Economizers

Economizer, or in the UK economizer, are mechanical devices intended to reduce energy

consumption, or to perform another useful function like preheating a fluid. The term

economizer is used for other purposes as well-Boiler, power plant, heating, ventilating

and air-conditioning. In boilers, economizer are heat exchange devices that heat fluids ,

usually water, up to but not normally beyond the boiling point of the fluid. Economizers

are so named because they can make use of the enthalpy and improving the boiler‟s

efficiency. They are devices fitted to a boiler which save energy by using the exhaust

gases from the boiler to preheat the cold water used to fill it (the feed water). Modern day

boilers, such as those in cold fired power stations, are still fitted with economizer which

is decedents of Green‟s original design. In this context there are turbines before it is

pumped to the boilers. A common application of economizer in steam power plants is to

capture the waste heat from boiler stack gases (flue gas) and transfer thus it to the boiler

feed water thus lowering the needed energy input , in turn reducing the firing rates to

accomplish the rated boiler output . Economizer lower stack temperatures which may

cause condensation of acidic combustion gases and serious equipment corrosion damage

if care is not taken in their design and material selection.

24. Air Preheater

Air preheater is a general term to describe any device designed to heat air before another

process (for example, combustion in a boiler). The purpose of the air preheater is to

recover the heat from the boiler flue gas which increases the thermal efficiency of the

boiler by reducing the useful heat lost in the flue gas. As a consequence, the flue gases

are also sent to the flue gas stack (or chimney) at a lower temperature allowing simplified

design of the ducting and the flue gas stack. It also allows control over the temperature of

gases leaving the stack.

30

25. Precipitator

An Electrostatic precipitator (ESP) or electrostatic air cleaner is a particulate device that

removes particles from a flowing gas (such as air) using the force of an induced

electrostatic charge. Electrostatic precipitators are highly efficient filtration devices, and

can easily remove fine particulate matter such as dust and smoke from the air steam.

ESPs continue to be excellent devices for control of many industrial particulate

emissions, including smoke from electricity-generating utilities (coal and oil fired), salt

cake collection from black liquor boilers in pump mills, and catalyst collection from

fluidized bed catalytic crackers from several hundred thousand ACFM in the largest coal-

fired boiler applications. The original parallel plate-Weighted wire design (described

above) has evolved as more efficient (and robust) discharge electrode designs, today

focus is on rigid discharge electrodes to which many sharpened spikes are attached ,

maximizing corona production. Transformer –rectifier systems apply voltages of

50-100 Kilovolts at relatively high current densities. Modern controls minimize sparking

and prevent arcing, avoiding damage to the components. Automatic rapping systems and

hopper evacuation systems remove the collected particulate matter while on line allowing

ESPs to stay in operation for years at a time.

26. Induced Draught Fan

The induced draft fan assists the FD fan by drawing out combustible gases from the

furnace, maintaining a slightly negative pressure in the furnace to avoid backfiring

through any opening. At the furnace outlet and before the furnace gases are handled by

the ID fan, fine dust carried by the outlet gases is removed to avoid atmospheric

pollution. This is an environmental limitation prescribed by law, which additionally

minimizes erosion of the ID fan.

27. Flue gas stack

A Flue gas stack is a type of chimney, a vertical pipe, channel or similar structure through

which combustion product gases called flue gases are exhausted to the outside air. Flue

gases are produced when coal, oil, natural gas, wood or any other large combustion

31

device. Flue gas is usually composed of carbon dioxide (CO2) and water vapour as well

as nitrogen and excess oxygen remaining from the intake combustion air. It also contains

a small percentage of pollutants such as particulates matter, carbon mono oxide, nitrogen

oxides and sulphur oxides. The flue gas stacks are often quite tall, up to 400 meters (1300

feet) or more, so as to disperse the exhaust pollutants over a greater area and thereby

reduce the concentration of the pollutants to the levels required by government's

environmental policies and regulations. The flue gases are exhausted from stoves, ovens,

fireplaces or other small sources within residential abodes, restaurants, hotels through

other stacks which are referred to as chimneys.

32

VARIOUS CYCLES AT POWER STATION

PRIMARY AIR CYCLE

SECONDARY AIR CYCLE

COAL CYLCE

ELECTRICITY CYCLE

FLUE GAS CYCLE

CONDENSATE CYCLE

FEED WATER CYCLE

STEAM CYCLE

33

PRIMARY AIR CYCLE

P A FAN

COLD AIR DUCT

SEAL AIR FAN

APH

HOT AIR DUCT

PULVERISER

34

SECONDARY AIR CYCLE

W

I

N

D

B

O

X

IGNITER FAN

SCANNER AIR FAN

SCANNER COOLING

FD FAN

SCAPH

APH

WIND BOX

BOILER

35

ELECTRICITY CYCLE

GENERATOR

UAT UAT

MAIN TRANSFORMER

SWITCH YARD

OUTGOING FEEDER

To Auxiliaries To Auxiliaries

36

CONDENSATE CYCLE

HOT WELL

CONDENSATE PUMPS

MAIN EJECTOR

GLAND STEAM COOLER WITH EJECTOR

LP HEATER 2

LP HEATER 3

LP HEATER 4

DEAERATOR

BOILER FEED PUMP

37

FEED WATER CYCLE

BOILER FEED PUMP

HP HEATOR 5

HP HEATOR 6

HP HEATOR 7

FEED REGULATING STN

ECONOMISER

BOILER DRUM

DOWN COMERS

UPRISERS

BOILER DRUM

38

STEAM CYCLE

BOILER DRUM

L.T.S.H.

FLATEN S.H.

FINAL S.H.

H P TURBINE

C.R.H.

H.R.H

I P TURBINE

L P TURBINE

CONDENSER

39

Coal Cycle

40

Flue Gas Cycle

41

ELECTRICAL MAINTENANCE DEPARTMENT – I (EMD-I)

Electrical maintenance division 1

It includes:

Motors

High Tension/Low Tension Switchgear

Coal handling plant

I was assigned to do training in this division from 11th

June to 29th

June.

42

MOTORS

Motors can be classified as AC and DC

.

AC MOTORS

1. Squirrel cage motor

2. Wound motor

3. Slip ring induction motor

In modern thermal power plant three phase squirrel cage induction motors are used but

sometime double wound motor is used when we need high starting torque e.g. in ball mill.

THREE PHASE INDUCTION MOTOR

Ns (speed) =120f/p

Stator can handle concentrated single layer winding, with each coil occupying one stator slot

The most common type of winding are:

1. DISTRIBUTED WINDING :

This type of winding is distributed over a number of slots.

2. DOUBLE LAYER WINDING :

Each stator slot contains sides of two different coils.

SQUIRREL CAGE INDUCTION MOTOR

Squirrel cage and wound cage have same mode of operation. Rotor conductors cut the

rotating stator magnetic field. an emf is induced across the rotor winding, current flows,

a rotor magnetic field is produced which interacts with the stator field causing a turning

43

motion. The rotor does not rotate at synchronous speed, its speed varies with applied

load. The slip speed being just enough to enable sufficient induced rotor current to produce the power

dissipated by the motor load and motor losses.

BEARINGS AND LUBRICATIONS

A good bearing is needed for trouble free operation of motor. Since it is very costly part of the motor,

due care has to be taken by checking it at regular intervals. So lubricating plays an

important role. Two types of lubricating are widely used

1. Oil lubrication

2. Grease lubrication

3. Insulation

INSULATION

Winding is an essential part so it should be insulated. Following types of insulation are widely used

TYPES OF INSULATION

CLASS TEMP UPTO WHICH THEY ARE EFFECTIVE

(DEGREE CENTIGRADE)

Y 90

A 105

E 120

B 130

F 155

H 180

C more than 180

F class insulation is generally preferred.

44

MAIN MOTOR USED IN BOILER AND OFF SIDE AREA

1. ID FAN( 2 PER UNIT)

It is located between EP and chimney used for creating induced draft in the furnace.

2. PA FAN(2 PER UNIT)

It is used for handling atmospheric air up to temperature 50 degree centigrade

3. FD FAN(2 PER UNIT)

It is used for handling secondary air for the boiler.

4. SCANNER FAN( 2 PER UNIT )

It is required for requisite air for scanner cooling.

5. IGNITOR FAN

It supplies air for cooling of igniters.

INSTRUMENTS SEEN

1. MICROMETER

This instrument is used for measuring inside as well as outside diameter of bearing.

2. MEGGAR

This instrument is used for measuring insulation resistance.

3. VIBRATION TESTER

It measures the vibration of the motor. It is measured in three dimensions-axial, vertical and

horizontal.

45

SWITCH GEAR

INTRODUCTION

Switchgear is one that makes or breaks the electrical circuit. It is a switching device that opens& closes a

circuit that defined as apparatus used for switching, Lon rolling & protecting the electrical

circuit & equipments. The switchgear equipment is essentially concerned with switching & interrupting

currents either under normal or abnormal operating conditions. The tubular switch with ordinary

fuse is simplest form of switchgear & is used to control & protect& other equipments in

homes, offices etc. For circuits of higher ratings, a High Rupturing Capacity (H.R.C) fuse in

condition with a switch may serve the purpose of controlling &protecting the circuit. However

such switchgear cannot be used profitably on high voltage system (3.3 KV) for 2 reasons. Firstly, when a

fuse blows, it takes some time to replace it &consequently there is interruption of service to

customer. Secondly, the fuse cannot successfully interrupt large currents that result from

the High Voltage System. In order to interrupt heavy fault currents, automatic circuit

breakers are used. There are very few types of circuit breakers in B.P.T.S they are VCB, OCB, and

SF6 gas circuit breaker. The most expensive circuit breaker is the SF6 type due to gas. There

are various companies which manufacture these circuit breakers: VOLTAS, JYOTI, and

KIRLOSKAR. Switchgear includes switches, fuses, circuit breakers, relays & other equipments

46

THE EQUIPMENTS THAT NORMALLY FALL IN THIS CATEGORY ARE:-

1. ISOLATOR

An isolator is one that can break the electrical circuit when the circuit is to be switched on no load.

These are used in various circuits for isolating the certain portion when required for

maintenance etc. An operating mechanism box normally installed at ground level drives the isolator.

The box has an operating mechanism in addition to its contactor circuit and auxiliary contacts may be

solenoid operated pneumatic three phase motor or DC motor transmitting through a spur gear to

the torsion shaft of the isolator. Certain interlocks are also provided with the isolator

These are

1. Isolator cannot operate unless breaker is open

2. Bus 1 and bus 2 isolators cannot be closed simultaneously

3. The interlock can be bypass in the event of closing of bus coupler breaker.

4. No isolator can operate when the corresponding earth switch is on

2. SWITCHING ISOLATOR

Switching isolator is capable of:

1. Interrupting charging current

2. Interrupting transformer magnetizing current

3. Load transformer switching. Its main application is in connection with the

transformer feeder as the unit makes it possible to switch gear one transformer

while the other is still on load.

3. CIRCUIT BREAKER

One which can make or break the circuit on load and even on faults is referred to as circuit

breakers. This equipment is the most important and is heavy duty equipment mainly utilized for

protection of various circuits and operations on load. Normally circuit breakers

installed are accompanied by isolators.

47

4. LOAD BREAK SWITCHES

These are those interrupting devices which can make or break circuits. These are normally on same

circuit, which are backed by circuit breakers

5. EARTH SWITCHES

Devices which are used normally to earth a particular system, to avoid any accident

happening due to induction on account of live adjoining circuits. These equipments do not handle

any appreciable current at all. Apart from this equipment there are a number of relays

etc. which are used in switchgear.

LT SWITCHGEAR

In LT switchgear there is no interlocking. It is classified in following ways:-

1. MAIN SWITCH

Main switch is control equipment which controls or disconnects the main supply. The

main switch for 3 phase supply is available for the range 32A, 63A, 100A, 200Q,

300A at 500V grade.

2. FUSES

With Avery high generating capacity of the modern power stations extremely heavy

carnets would flow in the fault and the fuse clearing the fault would be required to

withstand extremely heavy stress in process. It is used for supplying power to

auxiliaries with backup fuse protection. With fuses, quick break, quick make and

double break switch fuses for 63A and 100A, switch fuses for 200A,400A, 600A,

800A and 1000A are used.

3. CONTACTORS

AC Contractors are 3 poles suitable for D.O.L Starting of motors and protecting the

connected motors.

48

4. OVERLOAD RELAY

For overload protection, thermal overload relay are best suited for this purpose. They

operate due to the action of heat generated by passage of current through relay element.

5. AIR CIRCUIT BREAKERS

It is seen that use of oil in circuit breaker may cause a fire. So in all circuits breakers

at large capacity air at high pressure is used which is maximum at the time of quick

tripping of contacts. This reduces the possibility of sparking. The pressure may vary from

50-60kg/cm^2 for high and medium capacity circuit breakers.

49

HT SWITCHGEAR

1. MINIMUM OIL CIRCUIT BREAKER

These use oil as quenching medium. It comprises of simple dead tank row pursuing

projection from it. The moving contracts are carried on an iron arm lifted by a long

insulating tension rod and are closed simultaneously pneumatic operating mechanism by

means of tensions but throw off spring to be provided at mouth of the control the main

current within the controlled device.

Type-HKH 12/1000c·

Rated Voltage-66 KV

Normal Current-1250A·

Frequency-5Hz·

Breaking Capacity-3.4+KA Symmetrical

3.4+KA Asymmetrical

360 MVA Symmetrical

Motor Voltage-220 V/DC

50

2. AIR CIRCUIT BREAKER

In this the compressed air pressure around 15 kg per cm^2 is used for extinction of arc

caused by flow of air around the moving circuit . The breaker is closed by applying

pressure at lower opening and opened by applying pressure at upper opening. When

contacts operate, the cold air rushes around the movable contacts and blown the arc:

It has the following advantages over OCB:-

i. Fire hazard due to oil are eliminated.

ii. Operation takes place quickly.

iii. There is less burning of contacts since the duration is short and consistent.

iv. Facility for frequent operation since the cooling medium is replaced

constantly.

Rated Voltage-6.6 KV

Current-630 A

Auxiliary current-220 V/DC

51

3. SF6 CIRCUIT BREAKER

This type of circuit breaker is of construction to dead tank bulk oil to circuit breaker but

the principle of current interruption is similar to that of air blast circuit breaker. It simply

employs the arc extinguishing medium namely SF6. When it is broken down under an

electrical stress, it will quickly reconstitute itself.

Circuit Breakers-HPA

Standard-1 EC 56

Rated Voltage-12 KV

Insulation Level-28/75 KV

Rated Frequency-50 Hz

Breaking Current-40 KA

Rated Current-1600 A

Making Capacity-110 KA

52

4. VACUUM CIRCUIT BREAKER

It works on the principle that vacuum is used to save the purpose of insulation and. In

regards of insulation and strength, vacuum is superior dielectric medium and is better

that all other medium except air and sulphur which are generally used at high pressure.

Rated frequency-50 Hz·

Rated making Current-10 Peak KA

Rated Voltage-12 KV

Supply Voltage Closing-220 V/DC

53

COAL HANDLING PLANT (CHP)

The coal handling plant consists of two plants:

Old Coal Handling Plant (OCHP)

New Coal Handling Plant (NCHP)

The OCHP supplies coal to Unit- I, II, III &

NCHP supplies coal to Unit- IV and V.

COAL SUPPLIED AT BTPS

Coal is supplied to BTPS by Jharia coal mines. It is non-cooking coal and has following

specifications:-

Moisture- less than 8%

Volatile matter-17% to 19%

Ash- 35% - 40%

Calorific Value- 4500 to 5300 Kcal/kg

Coal is received in railway box racks containing 20 - 42 wagons in each rack.

Capacity of each box wagon is about 55 ton.

These wagons are placed on 2 wagon tippler in OCHP & one wagon tippler in

NCHP, in total 3, capacity 80 ton each.

54

COAL CYCLE

55

OLD COAL HANDLING PLANT (OCHP)

KEY DIAGRAM

56

The main constituents of OCHP plant are:-

WAGON TIPPLER

Wagon from coal yard come to the tippler and emptied here. There are 2 wagon tipplers

in the OCHP. The tippler is tilted to about 137°- 141° so that coal from the wagon is

emptied into the hopper. Elliptics feeder is used in OCHP. Total 8 feeders are used, 4 in

each hopper.

Slip Ring Induction Motor is used to operate a wagon tippler. This type of IM is used in

the tippler because of its high resistance, low speed & high torque characteristics. The

rating of the motor used is:

o Power 55 Kw

o Voltage 415V

o Current 102A

o Speed 1480rpm

o Phase 3

o Frequency 50Hz

Three types of wagon tipplers are used:-

a) ROTASIDE: - It is used for open type wagons in which each wagon carries around 50-

56 tons of coal. The wagon is tilted by 150° to put the coal in the unloading hopper.

b) ROTARY: - In this case the unloading hopper is placed directly under the tippler table.

This is also used to tilt the wagon tippler to 180°.

c) ROCKING TYPE: - It is used for close type wagons. In this hoppers is placed by the

side of end rocking is provided to facilitate unloading of coal at corners of the wagon.

57

CONVEYER

Conveyer belts are used in the OCHP to transfer coal from one place to other as required

in a convenient & safe way. All the belts are numbered accordingly so that their function can be easily

demarcated. These belts are made of rubber & move with a speed of 250-300 m/min.

Motor employed for the conveyer has a capacity of 150 HP. These conveyers have a capacity of

carrying the coal at the rate of 400 ton/hr.

ZERO SPEED SWITCH

It is used as a safety device for the motor i.e. if the belt is not moving & the motor is ON,

then it burns to save the motor. This switch checks the speed of the belt & switches off the motor when

speed is zero.

METAL DETECTOR

As the conveyer belt take coal from wagon to crusher house, no metal piece should go

along with coal. To achieve this objective, metal detectors & separators are used. In the

OCHP, these MD‟s are installed in the conveyer belts 2A & 2B.

CRUSHER HOUSE

Both the plants i.e. OCHP & NCHP use TATA crusher powered by BHEL motor.

Crusher is of ring type and the motor is a HT motor of rating 400HP & 6.6 KV. Crusher is designed to

crush the pieces to 20 mm size i.e. practically considered as the optimum size for transfer

via conveyer.

ROTARY BREAKER

If any large piece of metal of any hard substances like metal impurities comes in the conveyer belt which

cause load on the metal separator, then the rotary breaker rejects them reducing the load on the metal

detector.

58

STACKER-CUM-RECLAIMER

It is used for stacking & reclaiming the coal from the stockyard in case of unavailability

of wagons from coal mines.

PLOUGH FEEDER

These plough feeders are generally installed under slot bunkers or hoppers. These are used top lough the

coal to the belt from the coal fed from stockyard. These feeders used in this power station

are generally of rotary type.

TRIPPERS

Trippers are provided in the conveyer to collect the material at desired location on either side or along the

conveyer with the help of chute/ducts fitted with tripper itself. The motor in the tripper can make it move

both in forward and reverse direction.

PULL GUARD SWITCH

These are the switches which are installed at every 10m gap in a conveyer belt to ensure the safety of

motors running the conveyer belts. If at any time some accident happens or coal jumps

from belt and starts collecting at a place, this switch can be moved to NO(normally open)

position from NC (normally closed) position to stop conveyor belt from moving. At this

time the problem can be corrected & then again the switch can be moved to NC (normally closed)

position for normal working again.

INTERLOCKS: -

The CHP is normally spread over a wide area with centralized control room. Elaborate

scheme is therefore provided. If due to any emergency either the conveyor belt or the motor has to be

stopped, due to this interlocking all the other motors connected to it will automatically

stop &will not work till signal is given from the control room.

59

The control & protection scheme normally includes: -

A hooter system to warn that the plant is going to be started. The plant can be

started only after a definite time after the hooter is energized.

Sequential starting of conveyor system and tripping of all proceeding system if

any equipment in the chain is tripped.

Tripping of conveyor from speed switch for protection against belt slippage.

SEQUENTIAL OPERATION OF OCHP: -

I. Unloading the coal

II. Crushing & storage.

III. Conveying to boiler bunkers.

a) Coal arrives to plant via road, rail, sea, and river or canal route from collieries.

Most of it arrives by rail route only in railway wagons. Coal requirement by this plant is

approximately 10,500 metric ton/day.

b) This coal is tippled into hoppers. If the coal is oversized (400 mm sq), then it is

broken manually so that it passes the hopper mesh where through elliptic feeder it is put into

vibrators & then to conveyor belt 1A & 1B.

c) The coal through conveyor belts 1A & 1B goes to the crusher house. Also the

extra coal is sent to stockyard through these belts.

d) In the crusher house the small size coal pieces goes directly to the belt 2A & 2B whereas the

big size coal pieces are crushed in the crusher & then given to the belts 2A & 2B.

e) The crushed coal is taken to the bunker house via the conveyor belts 3A & 3B where it can be

used for further operations.

60

NEW COAL HNDLING PLANT (NCHP)

KEY DIAGRAM

61

The main constituents of NCHP plant are:-

Most of the constituents of the NCHP are the same as that of OCHP.

WAGON TIPPLER

In NCHP there is only one wagon tippler. In this it takes 52 sec to raise a wagon, 10 sec to empty the

wagon completely & then again 52 sec to bring the tippler down. A semicircular huge WT gear is used

to run the tippler. Protocol cameras have been installed for safety to ensure that no moving

creature or object is near the wagon which is on the tippler.

62

COAL FEEDER TO THE PLANT

Vibro feeders are installed below the hopper which helps in putting the coal to the conveyor belts. There

are 2 conveyor belts & 3 vibro feeder per plant, so in total there are 6 vibrofeeders.

Given below are the feeder motor specifications:

Power 15HP

Voltage 415V

Speed 1450rpm

CONVEYOR TURNING POINT-6BREAKER HOUSE

This house is required to render the coal size to 100mm sq. A 415W LT motor is used

in the breaker house.

REJECTION HOUSE

The coal comes to breaker house via conveyor belts 12A & 12B. Now in the breaker house the huge

stones & metal impurities are separated & sent to reject bin house through belts 18A

&18B.

RECLAIM HOPPER

It is the stockyard in which coal is stored for emergency purposes. Around 3 lakh ton of

coal can be stored in it

TURNING POINT 7

CRUSHER HOUSE

To ensure that the coal is of uniform size it is passed through crusher. The crusher is of ring

type. Has a motor rating of 400HP, 606KV. It is designed to crush the pieces to 20mm size

EXIT

63

SEQUENTIAL OPERATION OF NCHP:-

a) Coal arrives in wagons and tipples into hoppers.

b) if the coal is oversized (400mm sq), then it is broken manually so that it passes through

the hopper mesh.

c) From hopper it is taken to TP-6 12A & 12B.

d) Conveyors 12A & 12B take the coal to the breaker house which renders the coal size to be 100 mm

sq.

e) Metal separator & metal detector are installed in conveyor belts 14A/B & 15A/B respectively to

remove the metal impurities

.f) Stones which are not able to pass through the 100mm sq mesh of hammer are rejected

via 18A & 18B to the rejection house.

g) Extra coal is sent to the reclaim hopper via conveyor 16A & 16B.

h)From TP-7, coal is taken by conveyor 14A & 14B to the crusher house whose function

is to render size of the coal to 20mm sq.

SPECIFICATIONS OF MOTORS USED IN NCHP:-

I. Crusher: - BHEL ILAT/12B HD/02, 736rpm, 550Kw, 6600V.

II. Wagon Tippler: - 5D315l, 98Kw slip ring motor.

III. Conveyors: -

1)11A/B, 12A/B: - 125Kw, 315m, 1485rpm.

2)13A/B: - 55Kw, 250m, 1480rpm.

3)14A/B, 15A/B: - 150Kw, 355m, 1485rpm.

4)16A/B, 17A/B: - 110Kw, 315m, 1485rpm.

5)18A/B: - 37Kw, 225m, 1470rpm.

IV. Rotary Breaker: - 110Kw, 315m, 1485rpm

64

V. Belt Feeder: - 15Kw, 180L, 1445rpm

VI. Reversible Belt Feeder: - 18.7Kw, 200L, 1485rp

VII. VF 1-6: - 7.5Kw, 160m, 1485rpm

VIII. VF 7-8: - 15Kw, 180L, 1485rpm

IX. VF 9-12: - 11Kw,160L, 1485rpm

X. WSP Crusher House: - 15Kw, 160m, 4000rpm

XI. WSP Breaker House: - 7.5Kw, 132m, 1865rpm

XII. Metal Separator: - 5KV, 132m, 1410rpm

XIII. Spray Precipitator: - 18.5Kw, 200L, 3000rpm

SAFETY DEVICES FOR BELT CONVEYORS

Sometimes the belt is wet due to any reason, so it may not run due to reduced friction. A

switch senses this and prevents the belt from choking.

Sometime any accident may occur which requires the belt to stop, the pull cords are

pulled to stop the conveyor. This system starts again only when the pull cords are rest.

There is a push button in the control room from where the belt can be stopped in case

of emergency stoppage. Other equipments are pulley. Pulleys are made of mild steel,

rubber logging is provided to increase the friction factor between the pulley and belt.

MILLING SYSTEM

1. RC BUNKER

Raw coal is fed directly to these bunkers. These are 3 in no. per boiler. 4 & ½ tons of coal

are fed in 1 hr. the depth of bunkers is 10m.

65

2. RC FEEDER

It transports pre-crust coal from raw coal bunker to mill. The quantity of raw coal

fed in mill can be controlled by speed control of aviator drive controlling damper

and aviator change

3. BALL MILL :

The ball mill crushes the raw coal to a certain height and then allows it to fall

down. Due to impact of ball on coal and attraction as per the particles move over

each other as well as over the Armor lines, the coal gets crushed. Large particles

are broken by impact and full grinding is done by attraction. The Drying and

grinding option takes place simultaneously inside the mill. In ball mill coal is

converted to powdered form and due to pneumatic action the powdered form of

coal is transferred upwards.

4. CLASSIFIER:

It is equipment which serves separation of fine pulverized coal particles medium from

coarse medium. The pulverized coal along with the carrying medium strikes the

impact plate through the lower part. Large particles are then transferred to the ball mill.

5. MILL FAN

From ball mill the powdered coal is sucked through mill fan.

6. CYCLONE SEPARATORS

It separates the pulverized coal from carrying medium. The mixture of pulverized coal

vapour caters the cyclone separators tangentially in the upper part of the separator. Due

to decrease in the velocity the centrifugal action, the pulverized coal separated from the

vapour &falls down to the lower epical part.

66

7. THE TURNIGATE

It serves to transport pulverized coal from cyclone separators to pulverized coal bunker or

to worm conveyors. There are 4 turnigates per boiler.

8. WORM CONVEYOR

It is equipment used to distribute the pulverized coal from bunker of one system to

bunker of other system. It can be operated in both directions

67

ELECTRICAL MAINTENANCE DEPARTMENT –II (EMD-II)

Electrical maintenance division 2

It includes:

Generators

Transformers

Switch yard

I was assigned to do training in this division from 2nd

July to 13th July.

68

GENERATORS

The generator works on the principle of electromagnetic induction. There are two

components stator and rotor. The rotor is the moving part and the stator is the stationary

part. The rotor, which has a field winding, is given a excitation through a set of 3000rpm

to give the required frequency of HZ. The rotor is cooled by Hydrogen gas, which is locally

manufactured by the plant and has high heat carrying capacity of low density. If oxygen

and hydrogen get mixed then they will form very high explosive and to prevent their combining in any

way there is seal oil system. The stator cooling is done by de-mineralized (DM) water through hollow

conductors. Water is fed by one end by Teflon tube. A boiler and a turbine are coupled to electric

generators. Steam from the boiler is fed to the turbine through the connecting pipe. Steam

drives the turbine rotor. The turbine rotor drives the generator rotor which turns the

electromagnet within the coil of wire conductors.

Carbon dioxide is provided from the top and oil is provided from bottom to the generator.

With the help of carbon dioxide the oil is drained out to the oil tank.

Hydrogen gas is used to cool down the rotor.

Lube oil is used to cool the bearings.

69

DM water is used to cool the stator.

Seal oil is used to prevent hydrogen leakage

Seal oil coolers are present to cool the seal oil

Hydrogen dryer are used which removes the moisture from hydrogen gas and then

is supplied to the generator.

Clarified water in cooling tower is used to cool down the hydrogen gas.

RATINGS OF THE GENERATORS USED

Turbo generator 100MW

TURBO GENERATOR 210 MW

The 100 MW generator generates 10.75 KV and 210 MW generates 15.75 KV. The

voltage is stepped up to 220 KV with the help of generator transformer and is connected to the grid.

The voltage is stepped down to 6.6 KV with the help of UNIT AUXILLARY TRANSFORMER

(UAT) and this voltage is used to drive the HT motors. The voltage is further stepped

down to 415 V and then to 220 V and this voltage is used to drive Lt Motors.

70

TURBO GENERATOR 100MW

MAKE BHEL, Haridwar

CAPACITY 117,500 KVA

POWER 100,000 KW

STATOR VOLTAGE 10,500 V

STATOR CURRENT 6475 A

SPEED 5000rpm

POWER FACTOR 0.85

FREQUENCY 50 HZ

EXCITATION 280 V

TURBO GENERATOR 210MW

MAKE BHEL, Haridwar

CAPACITY 247,000 KVA

POWER 210,000 KW

STATOR VOLTAGE 15,750 V

STATOR CURRENT 9050 A

SPEED 5000 rpm

POWER FACTOR 0.85

FREQUENCY 50 HZ

EXCITATION 310 V

GAS PRESSURE 3.5 kg/cm

71

TRANSFORMERS

INTRODUCTION

It is a static machine which increases or decreases the AC voltage without changing the

frequency of the supply.

It is a device that:

Transfer electric power from one circuit to another.

It accomplishes this by electromagnetic induction.

In this the two electric circuits are in mutual inductive influence of each other.

WORKING PRINCIPLE:

It works on FARADAY‟S LAW OF ELECTROMAGNETIC INDUCTION (self

or mutual induction depending on the type of transformer).

72

MAIN PARTS

CONSERVATOR

It is used generally to conserve the insulating property of the oil from deterioration&

protect the transformer against failure on account of bad quality of oil.

SILICAGEL DEHYDRATING BREATHER

It is used to prevent entry of moisture inside the transformer tank. The breather

consists of silica gel.

GAS OPERATED RELAY (BUCHHOLZ RELAY)

It is a gas actuated relay used for protecting oil immersed transformer against all

types of faults. It indicates presence of gases in case of some minor fault & take

out the transformer out of circuit in case of serious fault.

BUSHINGS

It is made from highly insulating material to insulate & to bring out the terminals

of the transformer from the container. The bushings are of 3 types:

a. Porcelain bushings used for low voltage transformer

b. Oil filled bushings used for voltage up to 33KV.

c. Condensed type bushings used for voltage above 33KV.

OIL GUAGE

Every transformer with an oil guage to indicate the oil level. The oil guage may be

provided with the alarm contacts which gave an alarm the oil level has dropped

beyond permissible height due to oil leak etc.

TAPPINGS

The transformer are usually provided with few tappings on secondary side so

that output voltage can be varied for constant input voltage.

RADIATORS

It increases the surface area of the tank & more heat is thus radiated in less time.

WINDINGS TEMPERATURE INDICATOR (OIL GUAGE)

Device which indicates the temperature of winding of transformer & possible damage

to the transformer due too overload can be prevented.

73

CONSTRUCTIONAL FEATURES:

3 phase transformer is constructed in the core type construction

For reducing losses a smaller thickness of lamination is used.

For the above reason it is also called cold-rolled steel instead hot-rolled steel is

used.

High flux densities (1.4 to 1.7 Wb/sq m) are used in the core of power transformer

which carry load throughout.

For high voltage winding, disc type coils are used.

CLASSIFICATION:

(I) ACCORDING TO THE CORE:

a) Core type transformer

b) shell type transformer

c) Berry type transformer

(II) ACCORDING TO PHASES:

a) 1phase transformer

b) 3phase transformer

(III) ACCORDING TO THE PURPOSE FOR WHICH USED

:

a) Distribution transformer

b) Transmission transformer

c) Generator transformer

d) Station transformer

e) Unit Auxiliary transformer (UAT)

74

COOLING OF TRANSFORMERS OF LARGE MVA:

As size of transformer becomes large, the rate of the oil circulating becomes insufficient

to dissipate all the heat produced & artificial means of increasing the circulation by

electric pumps. In very large transformers, special coolers with water circulation may

have to be employed.

TYPES OF COOLING:

Air cooling

1. Air Natural (AN)

2. Air Forced (AF)

Oil immersed cooling

1. Oil Natural Air Natural (ONAN)

2. Oil Natural Air Forced (ONAF)

3. Oil Forced Air Natural (OFAN)

4. Oil Forced Air Forced (OFAF)

Oil immersed Water cooling

1. Oil Natural Water Forced (ONWF)

2. Oil Forced Water Forced (OFWF)

MAIN PARTS OF TRANSFORMER

i. Secondary Winding

ii. Primary Winding.

iii. Oil Level

iv. Conservator

v. Breather

vi. Drain Cock

vii. Cooling Tubes.

viii. Transformer Oil.

75

ix. Earth Point

x. Explosion Vent

xi. Temperature Gauge.

xii. Buchholz Relay

xiii. Secondary Terminal

xiv. Primary Terminal

GENERATOR TRANSFORMER (125MVA UNIT-I & UNIT-III)

RATING 125MVA

TYPE OF COOLING OFB

TEMP OF OIL 45^C

TEMP WINDING 60^C

KV (no load) HV-233 KVA

LV-10.5 KVA

LINE AMPERES HV-310 A

LV-6880

PHASE THREE

FREQUENCY 50 HZ

IMPEDANCE VOLTAGE 15%

VECTOR GROUP Y DELTA

INSULATION LEVEL HV-900 KV

LV-Neutral-38

CORE AND WINDING WEIGHT 110500 Kg

WEIGHT OF OIL 37200 Kg

TOTAL WEIGHT 188500 Kg

OIL QUANTITY 43900 lit

76

GENERATOR TRANSFORMER (166 MVA UNIT-IV)

RATING 240MVA

TYPE OF COOLING ON/OB/OFB

TEMP OF OIL

TEMP WINDING

VOLTS AT NO LOAD HV-236000

LV-A5750

LINE AMPERES HV-587 A

LV-8798

PHASE THREE

FREQUENCY 50 HZ

IMPEDANCE VOLTAGE 15.55%

VECTOR GROUP Y DELTA

CORE AND WINDING WEIGHT 138800 Kg

WEIGHT OF OIL 37850 Kg

TOTAL WEIGHT 234000 Kg

OIL QUANTITY 42500 lit

GUARANTEED MAX TEMP

DIVISION KERELA

YEAR 1977

77

UNIT AUXILIARY TRANSFORMER (UAT)

Unit I & V- 12.5 MVA

The UAT draws its input from the main bus-ducts. The total KVA capacity of UAT

required can be determined by assuming 0.85 power factor & 90% efficiency for total

auxiliary motor load. It is safe & desirable to provide about 20% excess capacity then

circulated to provide for miscellaneous auxiliaries & possible increase in auxiliary.

STATION TRANSFORMER

It is required to feed power to the auxiliaries during startups. This transformer is normally

rated for initial auxiliary load requirements of the unit in typical cases; this load is of the

order of 60% of the load at full generating capacity. It is provided with on load tap

change to cater to the fluctuating voltage of the grid.

NEUTRAL GROUNDED TRANSFORMER

This transformer is connected with supply coming out of UAT in stage-2. This is used to

ground the excess voltage if occurs in the secondary of UAT in spite of rated voltage.

78

SWITCH YARD

As we know that electrical energy can‟t be stored like cells, so what we generate should

be consumed instantaneously. But as the load is not constants therefore we generate electricity according

to need i.e. the generation depends upon load. The yard is the places from where the electricity is send

outside. It has both outdoor and indoor equipments.

OUTDOOR EQUIPMENTS

i. BUS BAR.

ii. LIGHTENING ARRESTER

iii. WAVE TRAP

iv. BREAKER

v. CAPACITATIVE VOLTAGE TRANSFORMER

vi. EARTHING ROD

vii. CURRENT TRANSFORMER.

viii. POTENTIAL TRANSFORMER

ix. LIGHTENING MASK

INDOOR EQUIPMENTS

i. RELAYS.

ii. CONTROL PANELS

iii. CIRCUIT BREAKERS

79

BUS BAR

Bus bars generally are of high conductive aluminum conforming to IS-5082 or

copper of adequate cross section .Bus bar located in air insulated enclosures & segregated

from all other components .Bus bar is preferably cover with polyurethane.

BY PASS BUS

This bus is a backup bus which comes handy when any of the buses become faulty. When any

operation bus has fault, this bus is brought into circuit and then faulty line is removed there by

restoring healthy power line.

LIGHTENING ARRESTOR

It saves the transformer and reactor from over voltage and over currents. It

grounds the overload if there is fault on the line and it prevents the generator transformer. The

practice is to install lightening arrestor at the incoming terminal of the line. We have to use the

lightning arrester both in primary and secondary of transformer and in reactors. A meter is

provided which indicates the surface leakage and internal grading current of arrester.

WAVE TRAP

Power line carrier communication (PLCC) is mainly used for telecommunication,

tele-protection and tele-monitoring between electrical substations through power

lines at high voltages, such as 110 kV, 220 kV, and 400 kV. PLCC integrates the

transmission of communication signal and 50/60 Hz power signal through the

same electric power cable. The major benefit is the union of two important

applications in a single system. WAVETRAP is connected in series with

the power (transmission) line. It blocks the high frequency carrier waves (24 KHz

to 500 KHz) and let power waves (50 Hz - 60 Hz) to pass-through.

80

BREAKER

Circuit breaker is an arrangement by which we can break the circuit or flow of current. A circuit

breaker in station serves the same purpose as switch but it has many added and complex

features. The basic construction of any circuit breaker requires the separation of

contact in an insulating fluid that servers two functions:

i. extinguishes the arc drawn between the contacts when circuit breaker opens.

ii. It provides adequate insulation between the contacts and from each contact to earth.

CAPACITATIVE VOLTAGE TRANSFORMER

A capacitor voltage transformer (CVT) is a transformer used in power systems to

step-down extra high voltage signals and provide low voltage signals either for

measurement or to operate a protective relay. It is located in the last in the switchyard as it

increases the ground resistance. Finally the voltage from CVT in the switchyard is

sent out from the station through transmission lines.

EARTHING ROD

Normally un-galvanized mild steel flats are used for earthling. Separate earthing electrodes are

provided to earth the lightening arrestor whereas the other equipments are earthed

by connecting their earth leads to the rid/ser of the ground mar.

CURRENT TRANSFORMER

It is essentially a step up transformer which step down the current to a known

ratio. It is a type of instrument transformer designed to provide a current in

its secondary winding proportional to the alternating current flowing in its

primary.

81

POTENTIAL TRANSFORMER

It is essentially a step down transformer and it step downs the voltage to a known ratio.

RELAYS

Relay is a sensing device that makes your circuit ON or OFF. They detect the

abnormal conditions in the electrical circuits by continuously measuring the electrical quantities,

which are different under normal and faulty conditions, like current, voltage frequency. Having

detected the fault the relay operates to complete the trip circuit, which results in the opening of

the circuit breakers and disconnect the faulty circuit.

There are different types of relays:

i. Current relay

ii. Potential relay

iii. Electromagnetic relay

iv. Numerical relay etc.

AIR BREAK EARTHING SWITCH

The work of this equipment comes into picture when we want to shut down the supply for

maintenance purpose. This help to neutralize the system from induced voltage

from extra high voltage. This induced power is up to 2KV in case of 400 KV

lines.

ELECTROSTATIC PRECIPITATOR

An electrostatic precipitator ( ESP) or electrostatic air cleaner

is a particulate collection device that removes particles from a flowing gas (such

as air) using the force of an induced electrostatic charge. Electrostatic

precipitators are highly efficient filtration devices that minimally impede the flow

of gases through the device, and can easily remove fine particulate matter such as

dust and smoke from the air stream.

82

In contrast to wet scrubbers which apply energy directly to the flowing fluid

medium, an ESP applies energy only to the particulate matter being collected and

therefore is very efficient in its consumption of energy (in the form of

electricity).The most basic precipitator contains a row of thin vertical wires, and

followed by a stack of large flat metal plates oriented vertically, with the plates

typically spaced about 1 cm to18 cm apart, depending on the application. The air

or gas stream flows horizontally through the spaces between the wires, and then

passes through the stack of plates. A negative voltage of several thousand volts is

applied between wire and plate. If the applied voltage is high enough an electric

(corona) discharge ionizes the gas around the electrodes. Negative ions flow to

the plates and charge the gas-flow particles.

The ionized particles, following the negative electric field created by the power

supply, move to the grounded plates. Particles build up on the collection plates

and form a layer. The layer does not collapse, thanks to electrostatic pressure

(given from layer resistivity, electric field, and current flowing in the collected

layer).

83

CONTROL & INSTRUMENTATION

INTRODUCTION

C&I LABS

CONTROL & MONITORING MECHENISM

PRESSURE MONITORING

TEMPERATURE MONITORING

FLOW MEASUREMENT

CONTROL VALVES

INTRODUCTION

This division basically calibrates various instruments and takes care of any faults occur in

any of the auxiliaries in the plant.

“Instrumentation can be well defined as a technology of using instruments to

measure and control the physical and chemical properties of a material.”

C&I LABS

Control and Instrumentation Department has following labs:

Manometry Lab.

Protection and Interlocks Lab.

Automation Lab.

Electronics Lab.

Water Treatment Plant.

Furnaces Safety Supervisory System Lab

84

OPERATION AND MAINTAINANCE

Control and Instrumentation Department has following Control Units:

1. Unit Control Board2.

2. Main Control Board3.

3. Analog & Digital Signal Control4.

4. Current Signal Control

This department is the brain of the plant because from the relays to transmitters followed by the

electronic computation chipsets and recorders and lastly the controlling circuitry, all fall under this.

A View of Control Room at BTPS

85

1. MANOMETRY LAB

TRANSMITTERS

It is used for pressure measurements of gases and liquids, its working principle is that the

input pressure is converted into electrostatic capacitance and from there it is conditioned

and amplified. It gives an output of 4-20 ma DC. It can be mounted on a pipe or a wall.

For liquid or steam measurement transmitters is mounted below main process piping and

for gas measurement transmitter is placed above pipe.

MANOMETER

It‟s a tube which is bent, in U shape. It is filled with a liquid. This device corresponds to a

difference in pressure across the two limbs.

BOURDEN PRESSURE GAUGE

It‟s an oval section tube. Its one end is fixed. It is provided with a pointer to indicate the

pressure on a calibrated scale. It is of 2 types :

(a) Spiral type: for Low pressure measurement.

(b) Helical Type: for High pressure measurement. While selecting Pressure Gauge these

parameters should keep in mind-

1. Accuracy

2. Safety

3. Utility

4. Price

ACCURACY

Higher Accuracy implies Larger Dial Size for accuracy of small and readable pressure

scale increments.

SAFETY

While selecting Pressure Gauge it should consider that Gauge Construction Material

should be chemically compatible with the environment either inside or outside it.

86

UTILITY

It should keep it mind that range of the Gauge should be according to our need else

Overpressure Failure may occur resulting in damage of Gauge.

PRICE

Lager the Gauge‟s Dial size larger would be our price. Better Gauge‟s Construction

material also increases the cost. So they must be chosen according to our need.

2. PROTECTION AND INTERLOCKING

INTERLOCKING

It is basically interconnecting two or more equipments so that if one equipment fails other

one can perform the tasks. This type of interdependence is also created so

that equipments connected together are started and shut down in the specific sequence to

avoid damage. For protection of equipments tripping are provided for all the equipments.

Tripping can be considered as the series of instructions connected through OR GATE,

which trips the circuit. The main equipments of this lab are relay and circuit breakers.

Some of the instrument uses for protection are:

RELAY

It is a protective device. It can detect wrong condition in electrical circuits by constantly

measuring the electrical quantities flowing under normal and faulty conditions. Some

of the electrical quantities are voltage, current, phase angle and velocity. 2. FUSES it is a

short piece of metal inserted in the circuit, which melts when heavy current flows through

it and thus breaks the circuit.

Usually silver is used as a fuse material because:

a. The coefficient of expansion of silver is very small. As a result no critical

fatigue occurs and thus the continuous full capacity normal current ratings are

assured for the long time.

87

b. The conductivity of the silver is unimpaired by the surges of the current that

produces temperatures just near the melting point

c. Silver fusible elements can be raised from normal operating temperature to

vaporization quicker than any other material because of its comparatively low

specific heat.

Miniature Circuit Breaker

They are used with combination of the control circuits to.

a) Enable the staring of plant and distributors.

b) Protect the circuit in case of a fault. In consists of current carrying contacts, one

movable and other fixed. When a fault occurs the contacts separate and are is

stuck between them.

There are three types of trips.

I. MANUAL TRIP

II. THERMAL TRIP

III. SHORT CIRCUIT TRIP

Protection and Interlock System-

1) HIGH TENSION CONTROL CIRCUIT for high tension system the control

system is excited by separate D.C supply. For starting the circuit conditions

should be in series with the starting coil of the equipment to energize it. Because

if even a single condition is not true then system will not start.

2) LOW TENSION CONTROL CIRCUIT For low tension system the control

circuits are directly excited from the 0.415 KV A.C supply.

The same circuit achieves both excitation and tripping. Hence the tripping coil is

provided for emergency tripping if the interconnection fails.

88

3. AUTOMATION LAB

This lab deals in automating the existing equipment and feeding routes. Earlier, the old

technology dealt with only (DAS) Data Acquisition System and came to be known

as primary systems. The modern technology or the secondary systems are coupled with

(MIS) Management Information System. But this lab universally applies the pressure

measuring instruments as the controlling force. However, the relays are also provided

but they are used only for protection and interlocks.

4. PYROMETRY LAB

LIQUID IN GLASS THERMOMETER

Mercury in the glass thermometer boils at 340° C which limits the range of temperature

that can be measured. It is L shaped thermometer which is designed to reach all

inaccessible places.

ULTRA VIOLET CENSOR-

This device is used in furnace and it measures the intensity of ultra violet rays there and

according to the wave generated which directly indicates the temperature in the furnace.

THERMOCOUPLES

This device is based on SEEBACK and PELTIER effect. It comprises of two junctions at

different temperature. Then the emf is induced in the circuit due to the flow of electrons.

This is an important part in the plant.

RTD (RESISTANCE TEMPERATURE DETECTOR)

It performs the function of thermocouple basically but the difference is of a resistance. In

this due to the change in the resistance the temperature difference is measured. In this

lab, also the measuring devices can be calibrated in the oil bath or just boiling water

(for low range devices) and in small furnace (for high range devices)

.

89

5. FURNACE SAFETY AND SUPERVISORY SYSTEM LAB

This lab has the responsibility of starting fire in the furnace to enable the burning of coal.

For first stage coal burners are in the front and rear of the furnace and for the second and

third stage corner firing is employed. Unburnt coal is removed using forced draft or

induced draft fan. The temperature inside the boiler is 1100°C and its heights 18 to 40 m.

It is made up of mild steel. An ultra violet sensor is employed in furnace to measure the

intensity of ultra violet rays inside the furnace and according to it a signal in the same

order of same mV is generated which directly indicates the temperature of the furnace.

For firing the furnace a 10 KV spark plug is operated for ten seconds over a spray

of diesel fuel and pre-heater air along each of the feeder-mills. The furnace has six feeder

mills each separated by warm air pipes fed from forced draft fans. In first stage indirect

firing is employed that is feeder mills are not fed directly from coal but are fed from three

feeders but are fed from pulverized coalbunkers. The furnace can operate on the

minimum feed from three feeders but under no circumstances should anyone be left

out under operation, to Prevent creation of pressure different with in the furnace, which

threatens to blast it.

6. ELECTRONICS LAB

This lab undertakes the calibration and testing of various cards. It houses various types of

analytical instruments like oscilloscopes, integrated circuits, cards auto analyzers etc.

Various processes undertaken in this lab are:

1. Transmitter converts mV to mA.

2. Auto analyzer purifies the sample before it is sent to electrodes. It extracts the

magnetic portion.

ANNUNCIATIN CARDS

They are used to keep any parameter like temperature etc. within limits. It gets a signal

if parameter goes beyond limit. It has a switching transistor connected to relay that helps

in alerting the UCB.

90

CONTROL & MONITORING MECHANISMS

There are basically two types of Problems faced in a Power Plant

1. Metallurgical

2. Mechanical

Mechanical Problem can be related to Turbines that is the max speed permissible for a

turbine is3000 rpm so speed should be monitored and maintained at that level.

Metallurgical Problem can be view as the max Inlet Temperature for Turbine is 1060°

C so temperature should be below the limit. Monitoring of all the parameters is necessary

for the safety of both:

1. Employees

2. Machines

So the Parameters to be monitored are:

1. Speed

2. Temperature

3. Current

4. Voltage

5. Pressure

6. Eccentricity

7. Flow of Gases

8. Vacuum Pressure

9. Valves

10. Level

11. Vibration

91

PRESSURE MONITORING

Pressure can be monitored by three types of basic mechanisms

1. Switches

2. Gauges

3. Transmitter type

For gauges we use Bourdon tubes. The Bourdon Tube is a non-liquid pressure

measurement device. It is widely used in applications where inexpensive static pressure

measurements are needed. A typical Bourdon tube contains a curved tube that is open

to external pressure input on one end and is coupled mechanically to an indicating needle

on the other end, as shows schematically below.

Typical Bourdon Tube Pressure Gages

For Switches pressure switches are used and they can be used for digital means of

monitoring as switch being ON is referred as high and being OFF is as low.

All the monitored data is converted to either Current or Voltage parameter.

92

The Plant standard for current and voltage are as under

• Voltage : 0 –10 Volts range

• Current : 4 –20 milli-Amperes

We use 4mA as the lower value so as to check for disturbances and wire breaks.

Accuracy of such systems is very high.

ACCURACY: ± 0.1 %

Programmable Logic Circuits (PLCs) are used in the process as they are the heart

of Instrumentation.

93

TEMPERATURE MONITORING

We can use Thermocouples or RTDs for temperature monitoring. Normally RTDs are

used for low temperatures.

Thermocouple selection depends upon two factors:

1. Temperature Range

2. Accuracy Required

Normally used Thermocouple is K Type Thermocouple:

In this we use Chromel (Nickel-Chromium Alloy) / Alumel (Nickel-Aluminium Alloy) as

two metals. This is the most commonly used general purpose thermocouple. It is

inexpensive and, owing to its popularity, available in a wide variety of probes. They are

available in the−200°C to +1200°C range. Sensitivity is approximately 41 μV/°C.

RTDs are also used but not in protection systems due to vibrational errors.

We pass a constant current through the RTD. So that if R changes then the Voltage also

changes

RTDs used in Industries are Pt100 And Pt1000

Pt100: 0°C – 100 Ω ( 1 Ω = 2.5 0C )

Pt1000: 0°C - 1000Ω

Pt1000 is used for higher accuracy.

The gauges used for Temperature measurements are mercury filled Temperature gauges.

For Analog medium thermocouples are used and for Digital medium Switches are used

which are basically mercury switches.

94

FLOW MEASUREMENT

Flow measurement does not signify much and is measured just for metering purposes and

for monitoring the processes

ROTAMETERS:

A Rotameter is a device that measures the flow rate of liquid or gas in a closed tube. It is

occasionally misspelled as 'Rotometer'.

It belongs to a class of meters called variable area meters, which measure flow rate

by allowing the cross sectional area the fluid travels through to vary, causing some

measurable effect. A rotameter consists of a tapered tube, typically made of glass, with a

float inside that is pushed up by flow and pulled down by gravity. At a higher flow rate

more area (between the float and the tube) is needed to accommodate the flow, so the

float rises. Floats are made in many different shapes, with spheres and spherical ellipses

being the most common. The float is shaped so that it rotates axially as the fluid passes.

This allows you to tell if the float is stuck since it will only rotate if it is not.

For Digital measurements Flap system is used.

For Analog measurements we can use the following methods :

1. Flow meters

2. Venturimeters / Orifice meters

3. Turbines

4. Mass flow meters (oil level)

5. Ultrasonic Flow meters

6. Magnetic Flow meter (water level )

Selection of flow meter depends upon the purpose, accuracy and liquid to be measured so

different types of meters used.

95

TURBINE TYPE:

They are simplest of all. They work on the principle that on each rotation of the turbine a

pulse is generated and that pulse is counted to get the flow rate.

VENTURIMETERS :

Referring to the diagram, using Bernoulli's equation in the special case of incompressible

fluids (such as the approximation of a water jet), and the theoretical pressure drop at the

constriction would be given by (ρ/2)(v22- v1

2).

And we know that rate of flow is given by:

Flow = k √ (D.P)

Where DP is Differential Pressure or the Pressure Drop.

96

CONTROL VALVES

A valve is a device that regulates the flow of substances (either gases, fluidized solids,

slurries, or liquids) by opening, closing, or partially obstructing various passageways.

Valves are technically pipe fittings, but usually are discussed separately. Valves are

used in a variety of applications including industrial, military, commercial, residential,

transportation. Plumbing valves are the most obvious in everyday life, but many more are

used.

Some valves are driven by pressure only, they are mainly used for safety purposes in

steam engines and domestic heating or cooking appliances. Others are used in

a controlled way, like in Otto cycle engines driven by a camshaft, where they play a

major role in engine cycle control.

Many valves are controlled manually with a handle attached to the valve stem. If the

handle is turned a quarter of a full turn (90°) between operating positions, the valve

is called a quarter-turn valve. Butterfly valves, ball valves, and plug valves are often

quarter-turn valves. Valves can also be controlled by devices called actuators attached to

the stem. They can be electromechanical actuators such as an electric motor or solenoid,

pneumatic actuators which are controlled by air pressure, or hydraulic actuators which

are controlled by the pressure of a liquid such as oil or water. So there are basically three

types of valves that are used in power industries besides the handle valves.

They are :·

PNEUMATIC VALVES –They are air or gas controlled which is compressed to turn or

move them·

HYDRAULIC VALVES – They utilize oil in place of Air as oil has better compression·

MOTORISED VALVES – These valves are controlled by electric motors

97

FURNACE SAFEGUARD SUPERVISORY SYSTEM

FSSS is also called as Burner Management System (BMS). It is a microprocessor Based

programmable logic controller of proven design incorporating all protection facilities

required for such system. Main objective of FSSS is to ensure safety of the boiler.

The 95 MW boilers are indirect type boilers. Fire takes place in front and in rear side.

That‟s why it‟s called front and rear type boiler.

The 210 MW boilers are direct type boilers (which means that HSD is in direct contact

with coal) firing takes place from the corner. Thus it is also known as corner type boiler.

IGNITER SYSTEM

Igniter system is an automatic system, it takes the charge from 110kv and this spark is

brought in front of the oil guns, which spray aerated HSD on the coal for coal

combustion. There is a 5 minute delay cycle before igniting, this is to evacuate or burn

the HSD. This method is known as PURGING.

PRESSURE SWITCH

Pressure switches are the devices that make or break a circuit. When pressure is applied,

the switch under the switch gets pressed which is attached to a relay that makes or break

the circuit.

Time delay can also be included in sensing the pressure with the help of pressure valves.

Examples of pressure valves:

1. Manual valves (tap)

2. Motorized valves (actuator) –works on motor action

3. Pneumatic valve (actuator) - works due to pressure of compressed air

4. Hydraulic valve

98

REFERNCES

99

APPENDIX

NTPC COURSE MATERIAL FOR TRAINEES