ABOUT NTPC
India‟s largest power company, NTPC was set up in 1975 to accelerate power
development in India. NTPC is emergi...
In October 2004, NTPC launched its Initial Public Offering (IPO) consisting of 5.25% as
fresh issue and 5.25% as offer for...
Strategies of NTPC

Technological Initiatives


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



Int...
Corporate Social Responsibility


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



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

Mission
“Develop and provide reliabl...
JOURNEY OF NTPC

6
NTPC Environment Policy

NTPC is committed to the environment, generating power at minimal environmental cost
and preservi...
As early as in November 1995, NTPC brought out a comprehensive document entitled
"NTPC Environment Policy and Environment ...
Flue Gas Stacks:
Tall Flue Gas Stacks have been provided for wide dispersion of the gaseous emissions
(SOX, NOX etc.) into...
Ash Dykes & Ash Disposal systems:
Ash ponds have been provided at all coal based stations except Dadri where Dry Ash
Dispo...
Liquid Waste Treatment Plants & Management System:
The objective of industrial liquid effluent treatment plant (ETP) is to...
ABOUT BTPS
BADARPUR THERMAL POWER STATION was established on 1973 and it was the
part of Central Government. On 01/04/1978...
Given below are the details of unit with the year they’re installed.

13
Station Location
Badarpur is situated only 20 km away from Delhi. The plant is located on the left side of the National
Hi...
OPERATION OF A POWER PLANT

Basic Principle

As per FARADAY‟s Law-“Whenever the amount of magnetic flux linked with a circ...
Basic Steps of Electricity Generation
The basic steps in the generation of electricity from coal involves following steps:...
Coal to Electricity : Basics

17
18
19
PARTS OF A POWER PLANT

The various parts are listed below:1. Cooling tower
2. Cooling water pump
3. Transmission line (3-...
12. Deaerator
13. Feed heater
14. Coal conveyor
15. Coal hopper
16. Pulverised fuel mill
17. Boiler drum
18. Ash hopper
19...
Draft towers or in natural draft hyperbolic shaped cooling towers as seen at most nuclear
power plants.

2. Cooling Water ...
neutral voltage. Another system commonly seen in North America is to have a delta
connected secondary with a center tap on...
rotating blades. The rotating blades convert the kinetic energy into impulse and reaction
forces, caused by pressure drop,...
8. Condenser
The steam coming out from the Low Pressure Turbine (a little above its boiling pump) is
brought into thermal ...
“process variable” whose value is provided by sensors that monitor changes in such
conditions. The opening or closing of c...
metal when the feed water is introduced back into the steam cycle. In a steam power
(usually modelled as a modified Rankin...
stainless) and its working involve temperature of 390°C and pressure well above 350psi
(2.4MPa). The separated steam is dr...
22. Air Intake
Air is taken from the environment by an air intake tower which is fed to the fuel.

23. Economizers
Economi...
25. Precipitator
An Electrostatic precipitator (ESP) or electrostatic air cleaner is a particulate device that
removes par...
device. Flue gas is usually composed of carbon dioxide (CO2) and water vapour as well
as nitrogen and excess oxygen remain...
VARIOUS CYCLES AT POWER STATION

 PRIMARY AIR CYCLE
 SECONDARY AIR CYCLE
 COAL CYLCE
 ELECTRICITY CYCLE
 FLUE GAS CYC...
PRIMARY AIR CYCLE

P A FAN

APH

COLD AIR DUCT

SEAL AIR FAN

HOT AIR DUCT

PULVERISER

33
SECONDARY AIR CYCLE

IGNITER FAN

FD FAN

SCANNER AIR FAN

SCAPH

SCANNER COOLING

APH

WIND BOX

BOILER

34

W
I
N
D

B
O...
ELECTRICITY CYCLE

GENERATOR

UAT

UAT

To Auxiliaries
To Auxiliaries

MAIN TRANSFORMER

SWITCH YARD

OUTGOING FEEDER

35
CONDENSATE CYCLE
HOT WELL

CONDENSATE PUMPS

MAIN EJECTOR

GLAND STEAM COOLER WITH EJECTOR

LP HEATER 2

LP HEATER 3

LP H...
FEED WATER CYCLE

BOILER FEED PUMP

HP HEATOR 5

HP HEATOR 6

HP HEATOR 7

FEED REGULATING STN

ECONOMISER

BOILER DRUM

D...
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

CONDENS...
Coal Cycle

39
Flue Gas Cycle

40
ELECTRICAL MAINTENANCE DEPARTMENT – I (EMD-I)

Electrical maintenance division 1
 It includes:


Motors



High Tension...
MOTORS

Motors can be classified as AC and DC
.

AC MOTORS
1. Squirrel cage motor
2. Wound motor
3. Slip ring induction mo...
motion. The rotor does not rotate at synchronous speed, its speed varies with applied
load. The slip speed being just enou...
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 ...
SWITCH GEAR

INTRODUCTION
Switchgear is one that makes or breaks the electrical circuit. It is a switching device that ope...
THE EQUIPMENTS THAT NORMALLY FALL IN THIS CATEGORY ARE:1. ISOLATOR
An isolator is one that can break the electrical circui...
4. LOAD BREAK SWITCHES
These are those interrupting devices which can make or break circuits. These are normally on same
c...
4. OVERLOAD RELAY
For overload protection, thermal overload relay are best suited for this purpose. They
operate due to th...
 HT SWITCHGEAR
1. MINIMUM OIL CIRCUIT BREAKER
These use oil as quenching medium. It comprises of simple dead tank row pur...
2. AIR CIRCUIT BREAKER

In this the compressed air pressure around 15 kg per cm^2 is used for extinction of arc
caused by ...
3. SF6 CIRCUIT BREAKER

This type of circuit breaker is of construction to dead tank bulk oil to circuit breaker but
the p...
4. VACUUM CIRCUIT BREAKER
It works on the principle that vacuum is used to save the purpose of insulation and. In
regards ...
COAL HANDLING PLANT (CHP)

The coal handling plant consists of two plants:


Old Coal Handling Plant (OCHP)



New Coal ...
COAL CYCLE

54
OLD COAL HANDLING PLANT (OCHP)

KEY DIAGRAM

55
The main constituents of OCHP plant are:-

WAGON TIPPLER
Wagon from coal yard come to the tippler and emptied here. There ...
CONVEYER
Conveyer belts are used in the OCHP to transfer coal from one place to other as required
in a convenient & safe w...
STACKER-CUM-RECLAIMER
It is used for stacking & reclaiming the coal from the stockyard in case of unavailability
of wagons...
The control & protection scheme normally includes: 

A hooter system to warn that the plant is going to be started. The p...
NEW COAL HNDLING PLANT (NCHP)

KEY DIAGRAM

60
The main constituents of NCHP plant are:Most of the constituents of the NCHP are the same as that of OCHP.

WAGON TIPPLER
...
COAL FEEDER TO THE PLANT
Vibro feeders are installed below the hopper which helps in putting the coal to the conveyor belt...
SEQUENTIAL OPERATION OF NCHP:-

a) Coal arrives in wagons and tipples into hoppers.
b) if the coal is oversized (400mm sq)...
V.

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

VI.

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

VII.

VF 1-6: - 7.5Kw, 160m, ...
2. RC FEEDER
It transports pre-crust coal from raw coal bunker to mill. The quantity of raw coal
fed in mill can be contro...
7. THE TURNIGATE
It serves to transport pulverized coal from cyclone separators to pulverized coal bunker or
to worm conve...
ELECTRICAL MAINTENANCE DEPARTMENT –II (EMD-II)

Electrical maintenance division 2
 It includes:


Generators



Transfo...
GENERATORS

The generator works on the principle of electromagnetic induction. There are two
components stator and rotor. ...


DM water is used to cool the stator.



Seal oil is used to prevent hydrogen leakage



Seal oil coolers are present ...
TURBOGENERATOR100MW

MAKE

BHEL, Haridwar

CAPACITY

117,500 KVA

POWER

100,000 KW

STATOR VOLTAGE

10,500 V

STATOR CURR...
TRANSFORMERS

INTRODUCTION
It is a static machine which increases or decreases the AC voltage without changing the
frequen...
MAIN PARTS
 CONSERVATOR
It is used generally to conserve the insulating property of the oil from deterioration&
protect t...
CONSTRUCTIONAL FEATURES:






3 phase transformer is constructed in the core type construction
For reducing losses a...
COOLING OF TRANSFORMERS OF LARGE MVA:
As size of transformer becomes large, the rate of the oil circulating becomes insuff...
ix.

Earth Point

x.

Explosion Vent

xi.

Temperature Gauge.

xii.

Buchholz Relay

xiii.

Secondary Terminal

xiv.

Prim...
GENERATOR TRANSFORMER (166 MVA UNIT-IV)
RATING

240MVA

TYPE OF COOLING

ON/OB/OFB

TEMP OF OIL
TEMP WINDING
VOLTS AT NO L...
UNIT AUXILIARY TRANSFORMER (UAT)

Unit I & V- 12.5 MVA

The UAT draws its input from the main bus-ducts. The total KVA cap...
SWITCH YARD
As we know that electrical energy can‟t be stored like cells, so what we generate should
be consumed instantan...


BUS BAR
Bus bars generally are of high conductive aluminum conforming to IS-5082 or
copper of adequate cross section .B...


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

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



REL...
In contrast to wet scrubbers which apply energy directly to the flowing fluid
medium, an ESP applies energy only to the pa...
CONTROL & INSTRUMENTATION



INTRODUCTION



C&I LABS



CONTROL & MONITORING MECHENISM



PRESSURE MONITORING



TEM...
OPERATION AND MAINTAINANCE
Control and Instrumentation Department has following Control Units:

1. Unit Control Board2.
2....
1. MANOMETRY LAB

TRANSMITTERS
It is used for pressure measurements of gases and liquids, its working principle is that th...
UTILITY
It should keep it mind that range of the Gauge should be according to our need else
Overpressure Failure may occur...
b. The conductivity of the silver is unimpaired by the surges of the current that
produces temperatures just near the melt...
3. AUTOMATION LAB
This lab deals in automating the existing equipment and feeding routes. Earlier, the old
technology deal...
5. FURNACE SAFETY AND SUPERVISORY SYSTEM LAB
This lab has the responsibility of starting fire in the furnace to enable the...
CONTROL & MONITORING MECHANISMS

There are basically two types of Problems faced in a Power Plant
1. Metallurgical
2. Mech...
PRESSURE MONITORING

Pressure can be monitored by three types of basic mechanisms
1. Switches
2. Gauges
3. Transmitter typ...
The Plant standard for current and voltage are as under
• Voltage : 0 –10 Volts range
• Current : 4 –20 milli-Amperes

We ...
TEMPERATURE MONITORING

We can use Thermocouples or RTDs for temperature monitoring. Normally RTDs are
used for low temper...
FLOW MEASUREMENT

Flow measurement does not signify much and is measured just for metering purposes and
for monitoring the...
TURBINE TYPE:
They are simplest of all. They work on the principle that on each rotation of the turbine a
pulse is generat...
CONTROL VALVES

A valve is a device that regulates the flow of substances (either gases, fluidized solids,
slurries, or li...
FURNACE SAFEGUARD SUPERVISORY SYSTEM

FSSS is also called as Burner Management System (BMS). It is a microprocessor Based
...
REFERNCES

98
APPENDIX

NTPC COURSE MATERIAL FOR TRAINEES

99
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  1. 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 341 st 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. 1
  2. 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. 2
  3. 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. 3
  4. 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 4
  5. 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 5
  6. 6. JOURNEY OF NTPC 6
  7. 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. 7
  8. 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. 8
  9. 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 LowNOX 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. 9
  10. 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. 10
  11. 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. 11
  12. 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 12
  13. 13. Given below are the details of unit with the year they’re installed. 13
  14. 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. 14
  15. 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. 15
  16. 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 16
  17. 17. Coal to Electricity : Basics 17
  18. 18. 18
  19. 19. 19
  20. 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 20
  21. 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 21
  22. 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 phase22
  23. 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 23
  24. 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. 24
  25. 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 25
  26. 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 noncorrosive. 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 26
  27. 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 27
  28. 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. 28
  29. 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. 29
  30. 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 coalfired 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 30
  31. 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. 31
  32. 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 32
  33. 33. PRIMARY AIR CYCLE P A FAN APH COLD AIR DUCT SEAL AIR FAN HOT AIR DUCT PULVERISER 33
  34. 34. SECONDARY AIR CYCLE IGNITER FAN FD FAN SCANNER AIR FAN SCAPH SCANNER COOLING APH WIND BOX BOILER 34 W I N D B O X
  35. 35. ELECTRICITY CYCLE GENERATOR UAT UAT To Auxiliaries To Auxiliaries MAIN TRANSFORMER SWITCH YARD OUTGOING FEEDER 35
  36. 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 36
  37. 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 37
  38. 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 38
  39. 39. Coal Cycle 39
  40. 40. Flue Gas Cycle 40
  41. 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. 41
  42. 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. DISTRIBUTEDWINDING: This type of winding is distributed over a number of slots. 2. DOUBLELAYERWINDING: 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 42
  43. 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. 43
  44. 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. 44
  45. 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 45
  46. 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. 46
  47. 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. 47
  48. 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. 48
  49. 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 49
  50. 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 50
  51. 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 51
  52. 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 52
  53. 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. COALSUPPLIEDAT 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. 53
  54. 54. COAL CYCLE 54
  55. 55. OLD COAL HANDLING PLANT (OCHP) KEY DIAGRAM 55
  56. 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 5056 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. 56
  57. 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. 57
  58. 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. 58
  59. 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. SEQUENTIALOPERATIONOFOCHP:- 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. 59
  60. 60. NEW COAL HNDLING PLANT (NCHP) KEY DIAGRAM 60
  61. 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. 61
  62. 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 62
  63. 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 63
  64. 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. RCBUNKER 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. 64
  65. 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. BALLMILL: 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. 65
  66. 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. WORMCONVEYOR 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 66
  67. 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. 67
  68. 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. 68
  69. 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. RATINGSOFTHE GENERATORSUSED  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. 69
  70. 70. TURBOGENERATOR100MW 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 70
  71. 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). 71
  72. 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. 72
  73. 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) ACCORDINGTO THECORE: a) Core type transformer b) shell type transformer c) Berry type transformer (II) ACCORDINGTO PHASES: a) 1phase transformer b) 3phase transformer (III) ACCORDINGTOTHE PURPOSEFOR WHICHUSED : a) b) c) d) e) Distribution transformer Transmission transformer Generator transformer Station transformer Unit Auxiliary transformer (UAT) 73
  74. 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. 2. 3. 4. Oil Natural Air Natural (ONAN) Oil Natural Air Forced (ONAF) Oil Forced Air Natural (OFAN) 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. 74
  75. 75. ix. Earth Point x. Explosion Vent xi. Temperature Gauge. xii. Buchholz Relay xiii. Secondary Terminal xiv. Primary Terminal GENERATORTRANSFORMER (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 75
  76. 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 76
  77. 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. 77
  78. 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 78
  79. 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. 79
  80. 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. 80
  81. 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. 81
  82. 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). 82
  83. 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 83
  84. 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 84
  85. 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 mind1. 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. 85
  86. 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. 86
  87. 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 System1) 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. 87
  88. 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 CENSORThis 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) . 88
  89. 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. 89
  90. 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 90
  91. 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. 91
  92. 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. 92
  93. 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. 93
  94. 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. 94
  95. 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- v12). And we know that rate of flow is given by: Flow = k √ (D.P) Where DP is Differential Pressure or the Pressure Drop. 95
  96. 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 96
  97. 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 97
  98. 98. REFERNCES 98
  99. 99. APPENDIX NTPC COURSE MATERIAL FOR TRAINEES 99

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