National thermal power corporation

NATIONAL THERMAL POWER CORPORATIONINDUSTRIAL TRAINING

HIMANSHU PANDEY

B.TECH 4th YEAR (ELECTRICAL AND ELECTRONICS ENGINEERING),G.L.A.I.T.M

CONTENTS

•Introduction•Background•Principle of a steam Power Plant•Rankine Cycle•Various Cycles in SteamPowerPlant•Coal Handling •D M Plant•Coal & Steam Cycle•Steam Production• Turbine•Ash Handling Plant•Electrostatic Precipitator•Variable Frequency Drive•Generator•Conclusion

INTRODUCTION

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 other. Within a span of 32 years, NTPC has emerged as a truly national power company, with power generating facilities in all the major regions of the country.

BACKGROUND

Feroze Gandhi Unchahar Thermal Power Project conceived as a load center station by the U.P. government for the benefit of the stage and is stated to have the ultimate capacity of 1050 MW (5*210 MW) stages of the project consisting of two units of 210 MW each was implemented by state government.

UNIT OVERVIEW

Unit 1 -21 NOV 1988Unit 2 -22 MARCH 1989Unit 3 -27 JAN 1999Unit 4 -22 OCT 1999

ABOUT STPP UNCHAHAR

Foundation stone was laid by Late Prime Minister Mrs. Indira Gandhi in June 1981.

First two units of 210 MW were commissioned on 21stNovember, 1988 and 22ndMarch, 1989 by U.P. Rajya Vidyut Utpadan Nigam.

FGUTPP was handed over by U.P. Rajya Vidyut Utpadan Nigam to NTPC in 13th February, 1992.

After take over of FGUTPP from UPRVUN to NTPC, unit-3, unit-4 and unit-5 were commissioned on 27th January1999, 22nd October 1999 and 2006 respectively.

NTPC has been ranked first as per total income in the power generation, transmission, distribution sector among India’s top 500 companies for the year 2006 by Dun and Bradstreet.

PRINCIPLE OF STEAM POWER PLANT GENERATION

The working principle of a steam plant is based upon the

Rankine cycle. Generally steam is taken as the working

medium due to its ability to be stable and that it’s readily stable.

The flow of steam in the plant can be very easily be understood

by the flow diagram of the plant. A graph plotted between the

temperature and the entropy would indicate the technical

details of the working by the Rankine cycle.

Plant Flow Diagram(Modified Rankine Cycle)

AB- Heating of feed water (i.e. sensible heat addition)

BC- Evaporation of water in boiler (i.e. latent heat addition)

CD- Superheating of steam (i.e. heat addition)

DE- Isentropic expansion of steam in HP turbine

EF- Reheating of steam in Reheaters

FH- Isentropic expansion of steam in IP and LP turbine

VARIOUS PATH IN POWER PLANT

1. Coal Cycle: Railway wagon power house wagon tipplercoal hopper CHP conveyor belt crusher house conveyor belt coal stockyard or RC bunker RC feeder pulverised mill furnace

2. Feed water cycle : Deaerator boiler feed pump Hp heatereconomiser boiler drum

Condensate water cycle :

Condenser hot well condensate extraction pump gland steam cooler LP heater deaerator

Contd……………

1. Steam cycle : Boiler drum LT SH platen SH final SH HP turbine reheater IP turbine LP turbine condenser

1. Air Path : P.A. fan air heater & cold P.A. fan mill furnace

F.D. fan

1. Flue gas path : Furnace reheater economiser air preheater E.S.P. I.D. fan chimney atmosphere

PLANT LAYOUT AT UNCHAHAR

COAL HANLINGThe fuel used in the thermal power plants in the boiler

furnace is coal. Coal undergoes various processes like separation, crushing, etc and is then finally moved to the furnace in the form of pulverised coal.

Coal: It is a mixture of organic chemicals and mineral materials produced by natural process of growth and decay. The chemical properties of any coal depend upon the proportions of different chemicals components present in it. There are four types of coal:

1. Peat 2. Lignite 3. Bituminous Coal 4. Anthracite

DEMINERALIZE WATER PLANTWater is required in plant for many purposes like for formation of steam, for removal of ash, for safety during fire etc. But the water required for formation of steam should be perfectly devoid of minerals because if it would be present with the steam then it will strike the blades of turbine and due to being in high pressure it produces scars or holes on the turbine blades.

Water is purified in DM plant through a chain of processes as under:-

1. Carbon filter -: Water taken from river is first sent to the carbon filter for the removal of carbon content in the water.

2. Strong acid cation exchanger-: After passing through the carbon filter water is sent to the strong acid cation exchanger which is filled with the concentrated HCL. The acid produces anions which get combined with the cations present in the water.

1. Strong base anion exchanger-: After passing though the two chambers of strong acid cation exchanger water is sent to the stron base anion exchanger which is filled with the concentrated NaOH. The base produces cations which get combined with the anions present in the water.

2. Mixed bed exchanger -: At last water is sent to the chamber of mixed bed exchanger where the remaining ions are removed.

COAL CYCLE

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

R.C. Feeder -: It is induction motor driven device, which determines the Quantity of coal enter in to pulverize mill

Pulverize mill: - Pulverization means exposing large surface area to the action of oxygen. Two types of mill are used in the plant.

Ball mill: - A ball mill operates normally under suction. A large drum partly filled with steel balls, is used in this mill. The drum is rotated slowly while coal is fed in to it. The ball pulverizes the coal by crushing.

Contact mill: - This mill uses impact principle. All the grinding elements and the primary air fan are mounted on a single shaft. The flow of air carries coal to the primary stage where it is reduced to a fine granular state by impact with a series of hammers

STEAM CYCLEBoiler drums → Ring Header → Boiler Drum (Steam

chamber) → Super Heater → H.P. Turbine → Reheater → I.

P. Turbine → L.P. Turbine.

BOILER DRUM:-

Boiler drum consist two chamber water chambers, steam chamber. Before entering in super heater the steam is going in to boiler drum, where the boiler drum filtered the moisture and stored in to water chamber.

SUPER HEATER:-

The function of super heater is to remove the last traces of moisture from the saturated steam leaving the water tube boiler. The temperature is approx 5300 c.

Contd………..

TURBINE:-

Steam turbine converts the heat energy in to mechanical energy and drives on initial and final heat content of the steam.

Turbine having number of stage in WHICH the pressure drops takes place.

STEAM PRODUCTION

The pulverised coal finally reaches the furnace. It is a primary part of the boiler where the chemical energy available in the fuel is converted into thermal energy by combustion. Furnace is designed for efficient and complete combustion. The pressure inside the furnace is maintained at -5mm to 10mm of water column. The air inside the furnace is not sufficient for full coal burning hence Forced Draught fans are employed for blasting air inside the furnace at very high pressure. Then to start the firing some oil is also sprinkled by means of oil igniters.

The method which has been adapted at FGUTPP is the Tangential Firing of Corner Firing. Here the burners are set at each corner of the furnace and directed to strike the outside of an imaginary circle in the furnace which is called the Fire Ball. Since the streams of fuel strike each other, extremely good mixing is obtained.

DIAGRAM OF WATER TUBE BOILER

Furnace is placed at the bottom of the most important part of the thermal plant where steam is generated. 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 5300 Celsius and its pressure is 120kg/cm2. The type of boiler can be further elaborated as natural circulation, dry bottom, and tangential fired, radiant heat type with direct fired pulverised coal system.

Once the steam is produced in the boiler, it gets collected inside the boiler drum. Boiler drum is a special type of cylindrical drum like structure which contains a mixture of water and steam. Steam being lighter gets collected at the top portion and beneath it we have the water. It is very important to maintain a safe level of water in the drum since we have two main types of constraints in this regard. If the steam produced and collected is more then it can lead to a blast in the boiler drum else tiny droplets of water can enter the turbine. Hence in order to keep a check we measure the level by hydrastep. Hydrastep is based on the difference in the conductivities of water and steam.

Soot blowers are basically pipe like structures that go inside the furnace and the boiler for efficient cleaning. Cleaning is done by the superheated steam which is tapped from the superheater 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:

1. long retraceable soot blower 2. wall blower 3. air reheater

Before sending this steam to the turbine, the steam is again

superheated and then its temperature is around 5800Celsius. This increases the efficiency since the temperature is the measure of energy hence higher temperature higher is the energy. Hence, during the phenomenon of superheating the steam which is dry and saturated, is being heated and hence the temperature of steam again rises.

First the steam from boiler drum enters the low temperature super heater (LTSH). After LTSH steam enters the platen superheater and then finally to a high temperature superheater. The steam which is now produced goes to the HP turbine.

TURBINEThe superheated steam after coming out of the superheater goes to the turbine. A turbine is a form of an engine running on steam, which requires a source of high grade energy and a source of low grade energy. When the fluid flows through the turbine a part of the energy content is continuously extracted and continuously converted into useful mechanical work.The main advantage of using a steam turbine rather than a prime mover is that the steam in a turbine can be expanded down to a lower back pressure, thereby making available a greater heat drop and a larger amount of this heat drop can be converted into useful mechanical work due to higher efficiency of the turbine. Therefore a turbine is suitable for driving a generator.

Turbines are of two types:

1. Impulse Turbine 2. Reaction Turbine

However another form called impulse-reaction turbine is also used which provide benefits of both types. The impulse-reaction turbine is used here at FGUTPP.

Here three stages of turbine are used:

HP turbine (high pressure)

IP turbine (intermediate pressure)

LP turbine (low pressure)

View Of Steam Turbine

The steam flow in the turbine takes place as follows; the steam from the superheater first goes to the HP turbine where it does work and loses its temperature. The steam from HP turbine is the fed to the reheater where its temperature is increased pressure remains the same as that from the outlet from HP turbine. The steam from the reheater is then fed to the IP turbine and then finally to the LP turbine. The LP turbine is connected to the generator and the mechanical output from the turbine is used to drive it.

ASH HANDLING PLANT

The ash produced in the boiler is transported to the ash dump area by means of ash handling system. It contains bottom ash system, fly ash system and ash slurry system.

Bottom Ash-: the bottom ash is collected in water troughs employed below bottom ash hoppers. The ash is continuously transported onto the respective clinker grinders which reduce lump sizes to fineness. The crushed ash from the clinker grinder falls into the hopper and from here it is taken to the ash slurry house.

Fly Ash-: the fly ash also gets collected into the separate hoppers where it gets mixed with flushing water.

Ash Slurry System-: this is the main system which is responsible for carrying away the ash slurry.

ELECTROSTATIC PRECIPITATORS

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. This causes the ash to drop into hoppers situated below the electrodes

STEPS-1. Ionisation of gases and charging of particles. 2. Migration of particles to respective electrodes. 3. Deposition of particles on the electrodes. 4. Dislodging of particles from the electrodes.

Description:

The ESP consist of two sets of electrodes, one in the form of helical thin wires called emitting electrode which is connected to -70KV DC and the collecting electrode in grounded.

Mechanism

The following mechanism takes place electrically:

Emitter electrode (E) creates a strong electric field near the surface and corona discharge takes place.

Positive and negative ions are formed by this discharge. The positive ions move towards anti positive charge line

electrodes called emitting electrodes and the negative ions towards collecting electrodes.

During this passage ions collide with ash particles and adhere to them.

These charged particles stick on the collector curtain which is the dislodged by the rapping motors which is collected by the hoppers. For optimum functional efficiency of the precipitator the

supply voltage should be maintained near above the flash over level between electrodes. This is achieved by the electronic control. The efficiency of ESP is about 99.95%.

ELECTRICAL MAINTENANCE DEPARTMENT – I (EMD-I)

It includes: Motors High Tension/Low Tension Switchgear Coal handling plant

MOTORSAC MOTORS

Squirrel cage motor Wound motor 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:

DISTRIBUTED WINDING :This type of winding is distributed over a number of slots.

  DOUBLE LAYER WINDING :

Each stator slot contains sides of two different coils.

SQUIRREL CAGE INDUCTION MOTOR 

Squirrel cage and wound cage have same mode of operation. Rotor conductors cut the rotating stator magnetic field. an emf is induced across the rotor winding, current flows, a rotor magnetic field is produced which interacts with the stator field causing a turning 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

Oil lubrication Grease lubrication Insulation

INSULATION

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

INSTRUMENTS SEEN

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

 MEGGAR This instrument is used for measuring insulation resistance.

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

SWITCH GEAR 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. In low tension switch gear thermal over load relays are used whereas in high

tension 5 different types of relays are used.

THE EQUIPMENTS THAT NORMALLY FALL IN THIS CATEGORY ARE:-

ISOLATOR  Isolator cannot operate unless breaker is open Bus 1 and bus 2 isolators cannot be closed simultaneously The interlock can be bypass in the event of closing of bus coupler breaker. No isolator can operate when the corresponding earth switch is on

SWITCHING ISOLATOR  Switching isolator is capable of:

Interrupting charging current Interrupting transformer magnetizing current 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.

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.

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

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.

Low Tension SWITCHGEAR 

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. 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.

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

motors.

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. 

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.

Contactors used in ntpcThermal overload relay

HT SWITCHGEAR 

MINIMUM OIL CIRCUIT BREAKER  These use oil as quenching medium.

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

SF6 CIRCUIT BREAKER  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.

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.

OIL CIRCUIT BREAKERS

AIR CIRCUIT BREAKERS

SF6 CIRCUIT BREAKERS

ELECTRICAL MAINTENANCE DEPARTMENT –II (EMD-II)

It includes: Generators Transformers Switch yard

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.

RATINGS OF THE GENERATORS USED

Turbo generator 100MW TURBO GENERATOR 210 MW  The 100 MW generator generates 10.75 KV and 210 MW

generates 15.75 KV. The voltage is stepped up to 220 KV with the help of generator transformer and is connected to the grid.

The voltage is stepped down to 6.6 KV with the help of UNIT AUXILLARY TRANSFORMER (UAT) and this voltage is used to drive the HT motors. The voltage is further stepped down to 415 V and then to 220 V and this voltage is used to drive Lt Motors.

TURBO GENERATOR 210MW

  MAKE  BHEL, HaridwarCAPACITY  247,000 KVAPOWER  210,000 KWSTATOR VOLTAGE  15,750 VSTATOR CURRENT 9050 ASPEED  5000 rpmPOWER FACTOR 0.85FREQUENCY  50 HZEXCITATION 310 VGAS PRESSURE 3.5 kg/cm

TRANSFORMERS

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).

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 coolingAir Natural (AN) Air Forced (AF) Oil immersed cooling Oil Natural Air Natural (ONAN)Oil Natural Air Forced (ONAF)Oil Forced Air Natural (OFAN)Oil Forced Air Forced (OFAF) Oil immersed Water cooling Oil Natural Water Forced (ONWF)Oil Forced Water Forced (OFWF)

MAIN PARTS OF TRANSFORMER 1. Secondary Winding2. Primary Winding.3. Oil Level4. Conservator5. Breather6. Drain Cock7. Cooling Tubes.8. Transformer Oil.9. Earth Point10. Explosion Vent 11. Temperature Gauge.12. Buchholz Relay13. Secondary Terminal14. Primary Terminal

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

RATING 125MVA TYPE OF COOLING  OFB TEMP OF OIL  45^C TEMP WINDING 60^C KV (no load) HV-233 KVA

LV-10.5 KVA LINE AMPERES  HV-310 A

LV-6880 PHASE THREE FREQUENCY 50 HZ IMPEDANCE VOLTAGE  15% VECTOR GROUP  Y DELTA INSULATION LEVEL  HV-900 KV

LV-Neutral-38 CORE AND WINDING WEIGHT  110500 Kg WEIGHT OF OIL  37200 Kg TOTAL WEIGHT  188500 Kg OIL QUANTITY  43900 lit 

GENERATOR TRANSFORMER (166 MVA UNIT-IV)

RATING 240MVA TYPE OF COOLING  ON/OB/OFB TEMP OF OIL  45 C TEMP WINDING  60 C 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  45 C DIVISION KERELA YEAR 1977

UNIT AUXILIARY TRANSFORMER (UAT) 

Unit I & V- 12.5 MVAThe 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 TRANSFORMERIt 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.

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 BUS BAR. LIGHTENING ARRESTER WAVE TRAP BREAKER CAPACITATIVE VOLTAGE TRANSFORMER EARTHING ROD CURRENT TRANSFORMER. POTENTIAL TRANSFORMER LIGHTENING MASK INDOOR EQUIPMENTS RELAYS. CONTROL PANELS CIRCUIT BREAKERS

EARTHING RODNormally 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.

POTENTIAL TRANSFORMER It is essentially a step down transformer and it step downs the voltage to a known ratio. RELAYSRelay 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:Current relayPotential relayElectromagnetic relayNumerical relay etc. AIR BREAK EARTHING SWITCHThe 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.

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