INDEXAbout companyEvolution of NTPCGeneration GrowthIntroductionUnit overviewVarious cycleSwitchyardCircuit BreakerLightening ArrestorGenerator and ProtectionTransformer BoilerESPCoal Handling and Its PartsAdvantages of Coal HandlingConclusion

NTPC-FGUTTP MAY 2012-13ABOUT THE COMPANY 

Corporate Vision:“A world class integrated power major, powering India’s growth, with increasing global presence” Core Values:B-Business EthicsC-Customer FocusO-Organizational & Professional prideM-Mutual Respect and TrustI- Innovation & SpeedT-Total quality for Excellence NTPC Limited is the largest thermal power generating company of India. A public sector company, it was incorporated in the year 1975 to accelerate power development in the country as a wholly owned company of the Government of India. At present, Government of India holds 89.5% of the total equity shares of the company and the balance 10.5% is held by FIIs, Domestic Banks, Public and others

EVOLUTION OF NTPC

1975

NTPC was set up in 1975 with 100% ownership by the Government of India. In the last 30 years, NTPC has grown into the largest power utility in India.  

1997

In 1997, Government of India granted NTPC status of “Navratna’ being one of the nine jewels of India, enhancing the powers to the Board of Directors.

2004

NTPC became a listed company with majority Government ownership of 89.5%. NTPC becomes third largest by Market Capitalisation of listed companies  

 2010

NTPC Ltd. Has granted of Maharatna status by Govt. of India. NTPC Ltd. Has been ranked 7th great place to work in India by The great places to work institute INDIA and The Economic times.

GENERATION GROWTH

INTRODUCTION

A)Location

Located on Lucknow Allahabad state highway 35 Km from Raebareli 80 Km from Allahabad 120 Km from Lucknow

 

B)Installed Capacity

Stage I = 2 X 210 MW Stage II = 2 X 210 MW Stage III = 210 MW  

C)Production Input Coal Source

Central Coal fields Ltd. ( CCL) Bharat Cooking Coal Ltd. (BCCL) Water Source

Sharada Sahayak Canal (main) Dalmau Pump Canal ( from river Ganga)

INTRODUCTION:-

D)Requirements

Coal – 140 tonnes / hr / unitWater – 700 tonnes/ hr / unit

E)Cost of Generation Rs. 2.40 / Kwh F)Environmental Aspects

Water Pollution- Effluents from thermal discharges from condenser, wastes from coal handling plant, service areas, oil, DM plant, sanitary waste and effluents from ash pond will be neutralized before being discharged.

Air Pollution- Particulate emission will be limited to 150 mg/Nm3 by installing high efficiency ESPs.

 

UNIT OVERVIEW

VARIOUS CYCLE

i. Coal Cycle

C.H.P Plant → Bunker →R.C Feeder → pulverize mill→ Boiler section

ii. Water Cycle

D.M. Plant → Hot Well → C.E.P. Pump → Low Pressure heater 1,2,3→Derater → Boiler Feed pump → High pressure Heater 5,6 → Feed Regulating station Economizer → Boiler Drum.

iii. Steam Cycle

Boiler drums → Ring Header → Boiler Drum (Steam chamber) → Super Heater → H.P. Turbine → Reheater → I. P. Turbine → L.P. Turbine

SWITCHYARDThe switch yard is the places from where the electricity is send outside. 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. It has both outdoor and indoor equipments.

Outdoor Equipments

Bus Bar Lightening Arrester Wave Trap Breaker Capacitor Voltage Transformer Earthing Rod Current Transformer Potential Transformer Isolators PLCC  Indoor Equipments Relays Control

CIRCUIT BREAKERCircuit 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:

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

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

The insulating fluids commonly used in circuit breakers are:

Compressed airOil which produces hydrogen for arc

excitation.VacuumSulphur hexafluoride (SF6 )There are two makes of Circuit Breakers

used at NTPC Unchahar switchyard:SF6 Circuit Breaker – manufactured by

ALSTOMGas Circuit Breaker – manufactured by CGL

SF6 CB

LIGHTENING ARRESTOR• It saves the transformer and reactor from over voltage and over currents. We have to use the lightning arrester both in primary and secondary of transformer and in reactor

Green – arrester is healthy

Red – arrester is defective

GENERATOR

The transformation of mechanical energy into electrical energy is carried out by the generator. The generator also called the alternator is based upon the principle of electromagnetic induction. This is a doubly excited system and the field is excited from dc supply whereas the output received from the alternator is ac

MAIN COMPONENT:-

1)ROTOR AND ROTOR WNDG2)STATOR,FRAME,CORE,WNDG

Excitation System

Static Excitation System-The generators in stage -1(u-1&u-2) have this excitation system. Static excitation system has slip ring and carbon brush arrangement. It consists of step down transformer, converter and AVR (automatic voltage regulator).

Brushless Excitation System –The generators in stage -2(U-3, U-4& &U- 5) have this excitation system. It has two exciters, one is main exciter and other is pilot exciter.

GENERATOR PROTECTION:- Stator Protection- The neutral of star connected winding is connected to primary of neutral grounding transformer, so that earth fault current :

GENERATOR COOLING:- Water as well as hydrogen cooling is

present in stage-I turbo generators with following specification

Rotor cooling: Hydrogen gas pressure: 3.5 Kg/cm2, Purity: 98%

Stator cooling: Water pressure: 3.5 Kg/cm2, Rate of flow of water: 130 m3/hr

  Stage-II & III: Only hydrogen cooling is used for both

stator and rotor cooling. Rotor cooling: Hydrogen Stator

cooling: Hydrogen gas pressure: 2.0 Kg/cm2, Purity: 98%

mited by over voltage relay

RotorProtection-Rotor winding may be damaged by earth faults or open circuits. The field is biased by a dc voltage, which causes current to flow through the relay for an earth fault anywhere on the field system

TRANSFORMER

The transformer is a device that transfers electrical energy from one electrical circuit to another through the medium of magnetic field and without the change of frequency. It is an electromagnetic energy conversion device, since the energy received by the primary is first converted to magnetic and is then reconverted to electrical energy in the secondary

ACCESSORIES:-

1)CONSEVATOR

2)BREATHER

3)BUSHING

4)RELAY

5)TAP CHANGER

COOLING:-

Simple Cooling

Natural cooling by atmospheric circulation, without any special devices. The transformer core and coils are open all round to the air. This method is confined to very small units at a few kV at low voltages

Mixed Cooling

with alternative additional air-blast cooling.

MAIN TRANSFORMER:-Generator Transformer: -- This is a

step up transformer. This supply gets its primary supply from generator and its secondary supplies the switchyard from where it is transmitted to grid. This transformer is oil cooled. The primary of this transformer is connected in star. The secondary is connected in delta. These are five in number.

Station Transformer: --This transformer has almost the same rating as the generator transformer. Its primary is connected in delta and secondary in star. It is a step down transformer. These are 4 in number.

Unit Auxiliary Transformer: -- This is a step down transformer. The primary receives from generator and secondary supplies a 6.6 KV bus. This is oil cooled. These are 10 in number.

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.

BOILER The boiler used at FGUTPP is the water tube

boiler type in which, water circulates in tubes surrounded by fire. Hence it takes up heat and gets converted into steam. The steam then rises up and gets collected inside the boiler drum. The boiler is made up of carbon steel. The temperature of steam that comes out of the boiler is around 530 deg Celsius and its pressure is 120kg/cm2.

Soot blowers are basically pipe like structures that go inside the furnace and the boiler for efficient on load cleaning. Cleaning is done by the superheated steam which is tapped from the super heater for the purpose of soot blowing. The pressure is reduced to 31kg/cm2 at 330 deg Celsius by means of reducing valve. We mainly have three types of soot blowers:

long retraceable soot blower wall blower air Reheater Before sending this steam to the turbine, the

steam is again superheated and then its temperature is around 580deg Celsius

WATER TUBE BOILER

ESP:-

The ash content in the Indian coal is of the order of 30 to 40 %. When coal is fired in the boiler, ashes are liberated and about 80% of ash is carried along with the flue gases. If this ash is allowed to flow in the atmosphere, it will cause air pollution and lead to health troubles. Therefore it is necessary to precipitate the dust from the flue gases and this work is done by the electrostatic precipitator.

Working principle

The principle upon which an electrostatic precipitator works is that dust laden gases are passed into a chamber where the individual particles of dust are given an electric charge by absorption of free ions from a high voltage DC ionising field. Electric forces cause a stream of ions to pass from the discharge electrodes (emitting) to the collecting electrodes and the particles of ash in the gas are deflected out of the gas stream into the collecting surfaces where they are retained by electrical attraction. They are removed by an intermittent blow usually referred to as RAPPING

DIAGRAM

PARTS OF ESP:-

1)BASING

2)HOPPER

3)COLLECTING SYSTEM

4)EMITTING SYSTEM

5)RAPPING

COAL HANDLING:-

Introduction NTPC Unchahar gets its coal supply mainly from

Bihar. Now coal is also coming from Australia, as coal produced in India is of low grade and ash content is more. The coal being filled in the wagons of the rail reaches plant. The purpose of this plant is to convey the coal to the bunker in the size not larger than 20mm.It handles and transports the coal to the bunker from the wagons by passing through various conveyors, transfer points, crusher houses, etc.

BCCL costs Rs.4/kg CCI cost Rs.6/kg  

Properties of Coal

Calorific value: the heat evolved when unit amount of coal is burned.

Gross calorific value: the heat evolved when all the products of combustion are cooled to the atmospheric temperature.

Net calorific value: it is the value obtained when GCV is subtracted by sensible and latent heat of water in the products of combustion.

Grindablity: it is the ease with which the coal can be ground to fine sizes. It is measured on the hard grove scale. Coal used here has a Grindablity index of 55.

COAL HANDLING:- Coal analysis It is done in two ways: Proximate analysis: it gives the behaviour of coal

when heated. Ultimate analysis: it tells the elementary composition

of coal. It is useful in determining the air required for combustion and in finding the weight of combustion products

Different methods of unloading the coal Manual Unloading: - Previously, manpower was used

for unloading the wagons. But it was very time consuming and more workers were

required for the job to be done.

2. Box in (using wagon tippler for unloading): - This method is still used in stage-1 of NTPC Unchahar. For this method, Indian Railway grants 10 hours for unloading the 58 wagons. In this method, Wagons are separated and tippled by using wagon tippler. The Beetle Feeder is used to move the wagon on wagon tippler. The coal from the wagons gets accumulated in The Track Hopper. At this time; the size of the coal is approximately 300mm.

3. BOBR: - This method is used in used in stage -2 and stage-3 of NTPC Unchahar. Indian Railway grants only 2.5 hours for Unloading 58 BOBR wagons. This is an advanced technology in which we use the compressor system. In Bottom Open Bottom Release (BOBR) technology the wagons are opened from side. Pressure is applied by the compressor to open the bottom gates of the wagon so that the coal gets released over the track hopper and wagon get unloaded quickly.

 

PARTS OF CHP:-

Marshalling Yard: it consist of railway tracks provided to receive the loaded trains, to unload them and to put them back in formation without interference between loaded and empty racks.

Wagon Tripler: The wagon Tripler is a most important device in thermal power Project

Paddle Feeder: - They have been installed on conveyors below the manual unloading track hopper. There are 6 nos. of paddle feeders, 3 on each conveyer. 3 Paddle Feeders of each conveyer move to and fro within a limiting range.

Vibrating Feeder: - They have been installed below the track hoppers of wagon tippler. The coal is accumulated over the vibrating feeder so by giving vibrations to the vibrating feeder we discharge the coal from track hopper to the conveyors.

Transfer Points: - Transfer Point is provided with flap gate and Conveyer. In transfer Point the coal is transferred from one conveyer to other conveyer.

Flap Gate: - The flap Gate is a two-way device. It consists of two gates. Both gates cannot operate together. By help of the flap Gate, we change the way of coal that fall down on the conveyer

CHP:-

Conveyers: - The Conveyer Belt is a moving device. It travels on its platforms. The shape of the conveyer belt is to be flat but on the platforms it is to be in curve shape. The coal falls down the conveyer and goes to the primary Crusher House Platforms. The capacity of conveyer in Stage – I is 800MT/ hr. & in Stage –II is 1200MT / hr.

 

•Primary crusher (rotary breaker): - In Primary Crusher House, the coal breaks in Rotary Breaker. Here the coal comes from the Transfer point; breaks here and the stone fall down to a separate place. Coal is converted from 300mm to 150mm size.

•Secondary Crusher (Ring Granulator): - In Secondary crusher House first the magnetic part separate from the coal and then feed to the Secondary Crusher. This Crusher breaks the coal in 20mm size and coal is sent to the Flap Gate and then feeded to the conveyer.

CHP:-

Coal handling•Magnetic separator: - They will remove the ferrous particles, which passes along with the coal. It consists of electromagnet around which a belt is moving. It is suspended from top, perpendicular to the conveyor belt at certain height. Whenever any iron particle passes below the CBMS, it is attracted by the magnet and stick to the cross belt below it. The CBMS capacity is of 50kg.

•Metal Detector: - The purpose of installation is to detect any metallic piece passing through the conveyor. Whenever the pieces pass below the search coil of the metal detector, it gives the trip command to the conveyor. Simultaneously, sand bag marker will fall on the conveyor belt so that the metal can be searched easily and removed.

Stacker/Reclaimer: - It is a very important device. The whole Structure of it is called Super Structure. It stacks the excessive coal and reclaims the coal on its requirement

CHP:-

Advantages:It can operate at full load

capacity in bad weather.It is productive at all times

as no return journey is to be performed.

DISADVANTAGE: The only drawback is that it

is expensive

CONCLUSION:-

NTPC Unchahar is one the plants in India to be under highest load factor for the maximum duration of time and that to operating at highest plant efficiencies. This plant is an example in terms of working efficiency and management of resources to all other thermal plants in our country. The operating plf of the NTPC as compared to the rest of country is the highest with 87.54% the highest since its inception.

The training gave me an opportunity to clear my concepts from practical point of view with the availability of machinery of diverse ratings.