INDUSTRIAL TRAINING REPORT

NTPC BARH

NTPC Overview NTPC Limited (Formerly National Thermal Power Corporation) is the largest

power generation company in India and was founded on November 7, 1975. Forbes Global 2000 for 2009 ranked it 317th in the world.

Contributing 26% of country’s entire power generation, it has placed itself in the Nav - Ratan companies of Indian government and hence is the public sector company.

The total installed capacity of the company is 31134 MW (including JVs) with 15 coal based and 7 gas based stations, located across the country. In addition under JVs, 3 stations are coal based & another station uses naphtha/LNG as fuel.

NTPC has been operating its plants at high efficiency levels. Although the company has 18.79% of the total national capacity it contributes 28.60% of total power generation due to its focus on high efficiency.

The company has set a future goal of having 75000 MW by 2017.

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Coal availability and linkage

:-Coal requirement for Barh STPP, stage-1 is proposed to be metfrom Amarpali block of north Karanpuracoalfields. Coal requirement for the project in estimated as 10 million tones/annum considering a GCV of 3350kcal/kg and 80% PLF

Coal transportation:

Coal from amarpali block of north karanpura coalfields is proposedto be transported to the project site through Indian railways system for adistance of approximately 250kms via shorter route .

Construction power

The requirements of the construction power supply for the projectwould be met at 33Kv level from the nearby BSEB substations. Necessary33kV substation and 11kV ring main /LT substations shall be provided for the power plant area.

Power Evacuation system

Power generated is proposed to be stepped up to 400kV bygenerator transformer and will be evacuated through the transmission systemto be evolved and implemented by Power Grid Corporation of India Ltd. Theswitchyard at power plant end is owned by NTPC

Beneficiary state

The states & UTs of Northern & Western regions and state of Bihar

Coal before fixing in the furnace is Pulverized.coal pulverization is required in the whole system process not just in terms of furnace performance and heat rate but in terms of mechanical reliability and integrity of furnace.

Flame is established in the furnaceUsing the LDO(light diesel oil).LDO isatomized by applying arc to it.

Coal+air- Co2+CO+Sox+MOx+heat+ASHHere CO2-heat carrier

CO-Acidic, danger to tubes(less air) MOX,SOX-Acidic formation in waterbodies and atmosphere.

To avoid the gases CO,MOX,SOX a ratio is maintained between air and coal of 1:6.It also ensures proper combustion.The water is purified(DM water) before injunction in the furnace to prevent choking of pipes due to the scale formation.

1.BOILER2.TURBINES3.COOLING WATER PUMP4.CONDENSER5.DEAREATOR6.REHEATER7.AIR PREHEATER8.PRECIPITATOR9.ECONOMISER10.COOLING TOWER11.TRANSMISSION LINES(3 PHASE)12.UNIT TRANSFORMERS(3 PHASE)13.ELECTRIC GENERATORS(3 PHASE)14.CONDENSATE EXTRACTION PUMP

15. Steam governor valve 16. FEED HEATER17.COAL CONVEYOR18.COAL HOPPER19.FORCED DRAUGHT FAN20.FLUE GAS

Boiler is a rectangular furnace about 50 feet on side and 130 feet tall. theirs walls are made of high pressure steel tubes about 2.3 inches in diameter which circulates DM water to be converted into steam. The thermal radiation heats water and changes to steam. Steam is sent to the turbine .The efficiency and technology of boiler vary according to the operational pressures.1. Operational pressure>221 KSC---%n=42.45%-----super critical boiler2. 175KSC <Operational pressure<221 KSC---%n=38.42%----- critical boiler3. Operational pressure<175KSC---%n=38%-----sub critical boiler

The turbine generator consists of a series of steam turbines interconnected to each other and generators on a common shaft. There is a high pressure turbine at one end, followed by intermediate pressure turbine and low pressure turbine in other end. Steam loses pressure and temperatures as it passes through turbines and expands in volume.

It pumps the water from the cooling tower which goes to the 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.

A deareator 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 deareator typically includes a vertical domed deareation section as the deareation 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.

Reheater is a heater which is used to raise the temperature of steam which has fallen from the intermediate pressure turbine.

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.

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

General Voltage LevelLT – 415 V

HT – 11KV & 3.3 KVEHT – 400KV

Voltage generation level (NTPC Barh)stage 1 – 24.5kv

stage 2 – 21.5kv

voltage level ( power plant)5.5kv, 11kv, 132kv,400kv

Switchyard is considered as the HEART of the Power Plant. Power generated can be worthy only if it is successfully transmitted and received by its consumers. Switchyard plays a very important role as a junction between the generation and transmission. It is a junction, which carries the generated power to its destination (i.e. consumers).

Outdoor equipments

1. Bus bar2. Lightening Arrester3. Wavetrap4. Breaker5. Capacitive voltage transformer6. Earthingrod7. Current transformer8. Potential transformer9. Lightening Mask

Indoor equipments

1. Relays2. Control panels’3. Circuit breakers

1. Bus bar

1.In electrical power distribution, a busbar is a strip

orbar of copper, brass or aluminium that conducts

electricity within a switchboard, distribution board,

substation, battery bank, or other electrical apparatus.

PICTORIAL VIEW OF BUS BAR

A lightning arrester is a device used on electrical power systems and telecommunications systems to protect the insulation and conductors of the system from the damaging effects of lightning. The typical lightning arrester has a high-voltage terminal and a ground terminal.

2.lightning arrester

PICTORIAL VIEW OF LIGHTNING ARRESTER

3.wave trap

Wave Traps are used at sub-stations using Power Line Carrier Communication (PLCC). PLCC is used to transmit communication and control information at a high frequency over the power lines. This reduces need for a separate infra for communication between sub-stations.

4 .Breaker

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and interrupt current flow.

Depending on the arc quenching medium being used C.B.s can be categorizedinto various types. In BSTPP for 400 KV/132 KV switchyard only one type is being used

ACB (Air break circuit breaker):-operated as well asarc quenched through air.

BOCB (Bulk oil circuit breaker):-arc quenching done through oil(Aerosol fluid oil).

MOCB (Minimum oil circuit breaker):-arc quenching done through oil(Aerosol fluid oil).

ABCB (Air Blast Circuit Breaker):-arc quenching done by blast of air

SF6 circuit breaker:-arc quenching done through SF6 gas.

A capacitor voltage transformer (CVT), or capacitance-coupled voltage transformer (CCVT), is a transformer used in power systems to step down extra high voltage signals and provide a low voltage signal, for metering or operating a protective relay.

5. CAPACITIVE VOLTAGE TRANSFORMER

6.CURRENT TRANSFORMER

The current transformer is a step up transformer , it means current is steppeddown to a very low value (generally 1 A or 5 A) so that it can be used for measuring and protection purposes .C.T is designed in such a way its Core Material could give high accuracy withlow saturation factor. Core Material is generally made of CRGO Silicon steelFor very low loss characteristics, µ material (Alloy of Ni-Fe) is used.

Current Transformer is used for basically two major functions: -1 .Meteringwhich means current measurement.

2. Protectionsuch as over current protection, overload earth faultprotection, Bus-bar protection, Bus differential protection.CT is typically described by its current ratio from primary to secondary. Thereis not more difference between 132 KV and 400 KV C.T , only current ratio differ

SPECIFICATIONS OF 132 KV C.T

Standard IS2705

Highest System Voltage 145 KV

Insulation Level 275/650 KV

Frequency 50 Hz

Short Time Current 31.5 KA for 1 sec

Rated Primary Current 1200 A

Extended Current 120

Standard IS2705

Rated Voltage 420 KV

Insulation Level 275/650 KV

Frequency 50 Hz

Short Time Current 31.5 KA for 1 sec

Rated Continous normal Current 2000 A

Extended Current 200/120%

Oil weight 750 Kg

Total weight 2500 K

SPECIFICATIONS OF 400 KV C.T

ISOLATOR An isolator is one, which can break an electrical circuit when the circuit is to beswitched on no load. These are normally used in various circuits for the purposes of isolating a certain portion when required for maintenance etc.

It isalways used in OFF-LOAD condition."Switching isolators" are capable of •Interrupting transformer magnetized currents;•Interrupting line charging current; and•Load transfer switching

In BSTPP there are two switchyards:-

(i) 400KV SWITCHYARD(ii) 132KV SWITCHYARD

.400 KV SWITCHYARDThere are total 22 bay in 400 KV switchyard. A Bay is basically

a way for the incoming power from generator as well as

outgoing power for distribution.

5 Bay for each generating transformer

3 Bay for ICT(Inter Connecting Transformer)

2 Bay for PATNA line

2 Bay for KAHALGAON line

2 Bay for BALIA line

7 for FUTURE line

1 Bay for SHUNT REACTOR

There are four main buses in 400 KV switchyard.

Main bus – 1& 2

Main bus – 3&4

132 KV SWITCHYARDThere are total 11 Bay in 132 KV switchyard.

3 Bay for ICT (Inter Connecting Transformer)

5 Bay for S.T (Station Transformer)

2 Bay for MST (Miscellaneous Service Transformer)

1 Bay for Bus Coupler

There are two main buses in 132 KV switchyard.

Main bus - 1

Main bus - 2

It is a static machine which increases or decreases the AC voltage without changing the frequency of the supply. It is a

device that:

Transfers 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).

CLASSIFICATION:

(I) ACCORDING TO THE CORE: a) Core type transformer b) shell type transformer c) Berry type transformer

(II) ACCORDING TO PHASES: a) 1phase transformer b) 3phase transformer

(III) ACCORDING TO THE PURPOSE FOR WHICH USED : a) Distribution transformer b) Transmission transformer c) Generator transformer d) Station transformer e) Unit Auxiliary transformer (UAT)

GENERATING TRANSFORMER

A generating transformer is a single – phase power transformer(3 single phaseunits shall form a bank) . Generating Transformer steps–up the generatedvoltage of 24 KV by alternator to a higher voltage of 400 KV (hence, workingas a step-up Transformer).This voltage of 400 KV is then transmitted to

switchyard

HV Nominal Voltage 420/sqrt(3) KV

LV Nominal Voltage 24 KV

Rated Power 260 MVA

HV Nominal Current 1072.22 A

LV Nominal Current 10833.33 A

Frequency 50 Hz

Phases single phase *

Lightning impulse withstand voltage 1425 kVp(HV)170 kVp(LV)95 kVp(HVn

SPECIFICATIONS

Tap range ± 5% in steps of 2.5%on HV neutral side

Oil weight 60430 Kg

Total weight 250930K

INTER CONNECTING TRANSFORMER

An ICT is a 3-phase auto transformer used to interconnect 400 KVswitchyard and 132 KV switchyard.

SPECIFICATIONS

Standard IS:2026

Type Auto Transformer

Rated power 200 MVA(HV)200 MVA(MV)67 MVA(LV)Reactive5 MVA Active

Current rating of different cooling 40% /60%/100% (A)

Winding connection star(HV)star(MV)delta(LV)solidlygrounded(HVn)

Core and winding mass 115600 Kgs

Oil mass 81880 Kgs

Total oil quantity 92000 litr

STATION TRANSFORMER

Station Transformer isused only for initializing the start-up of the station (MainPlant).Itis very beneficial during emergency situations such as tripping of Units, shut-down etc. Station transformers is used to startStation auxiliaries awhich are required for generating services such as coal and ash handlingsystem, lighting system, water purifying system etc.It gets the supply in its primary from 132 KV switchyard, stepsdown it to 11.5KV which is used for starting various equipments & devices used in the Main power plant

SPCIFICATIONS

Standard IS:2026/77-81

Type Three Winding

Rated outpu t90/45/45 MVA

Cooling ONAN/ONAF

Rated voltage 132 KV (HV)11.5 KV(LV1 & LV2)

Core & coil mass 60500 Kg

Oil quantity 33700 Litre

Total mass 121500 K

UNIT TRANSFORMER

Unit transformer is directly coupled to the unit itself so when that unit is inrunning condition it supplies power to which are coupled to auxiliaries directlyor through unit auxiliary transformer depending upon load. Unit auxiliaries arethosewhich are directly associated with the generating unit such as ID and FDfans, Boiler feed pumps, coal mills, fans, circulating water pumps etc

SPECIFICATION

Rated output 35 MVA

Cooling ONAN/ONAF

Voltage ratio 24 / 11.5 KV

Frequency 50 Hz

Phases Three

ONAN ratingmin 80% of rated MVA

MISCELLANEOUS SERVICE TRANSFORMER

Miscellaneous service transformer are used to supply miscellaneous loads of plant. It is a two winding transformer connected to 132 KV switchyard.

SPECIFICATION

Core & coil mass 17650 Kg

Oil quantity 10400 litre

Total mass 37600 kG

Standard IS:2026/77-81

Rated output 16 MVA

Full load rated current 69.98 A803.27 A

Cooling ONAN

Type Two winding

Voltage ratio 132 / 11.5 KV

Frequency 50 Hz

Phase Thre

GENERATOR SPECIFICATIONS-

KVA 247000

Pf 0.85

Volts of stator 15750

Amperes of stator 9050

Volts of rotor 310

Amperes of rotor 2600

Rpm 3000

Hz 50

Phase 3

Connection YY

Coolant water(stator)&hydrogen(rotor)

Gas pressure 3.5kg/cm-sq.

Insulation class B

Turbo generators are used in thermal power stations because of the steam energy to mechanical energy

conversion, turbo generators are more efficient.