THERMAL POWER PLANT - INTRODUCTION, COMPONENTS, PROCESSES ETC.

By
Advertisement

FUNCTIONAL DESCRIPTION

In Thermal Power Station fuel burns & use the resultant to make the steam, which derives the turbo generator. The Fuel i.e. coal is burnt in pulverized from. The pressure energy of the steam produce is converted into mechanical energy with the help of turbine. The mechanical energy is fed to the generator where the magnet rotate inside a set of stator winding & thus electricity is produced in India 65% of total power is generated by thermal power stations. To understand the working of the Thermal Power Station plant, we can divide the whole process into following parts.






1.       COAL FLOW
In coal fired plants, raw material are air & water in PTPS, coal is transported through Railway wagons from M/s Coal India & is kept reserved on a buffer stock. The brought out to the station is unloaded with the help of wagon tippler. After unloading, the coal is sent to crusher house with the help of conveyor belts. The coal which is now reduced to very small pieces is sent to the coal bunkers with the help of conveyor belt.  The raw coal is fed to coal mills through raw coal feeders raw coal feeders basically regulate raw coal to pulverized coal pipes. A position of the primary air is heated utilizing the heat of the fuel gases & then mixed with the cold air as per requirement by the pulverized coal. Normally the temperature is maintained at 60 to 70 degrees. The coal is now burnt in the furnace using oil in the beginning showered through the nozzles at different elevations in the furnace. To provide air for combustion, the heat of the flue gases also heat it the heat produced due to combustion is utilized for the conversion of water into steam. This water is stored in the boiler drum. There are two sets of pipes attached to the drum, one called riser & other known as down corner through which the water comes to the ring header & steam moves up due to the density difference of water & steam. Its steam is super heated using super heaters & meanwhile the flue gases are through out in the atmosphere through chimney.


2.       STEAM FLOW
The super heated steam is sent to the turbine through pipelines there are three turbines in the units, using this steam at different temperature & pressures. After passing through high pressure turbine the steam is send to the reheater for rising the temperature of the steam. After reheating the steam is sent to the intermediate pressure turbine through reheated line. Here it losses most of its temperature & pressure & finally sent to low pressure turbine. The uses of three different turbines help in increasing the efficiency of the plant. The turbine in turn connecting with a generator produces electricity. Then this electricity is stepped upto 220 KV with the help of step up transformer & supplied to various sub-stations grids.
Meanwhile, the steam through low pressure (L.P.) Turbine is condensed and the condensed water is stored in hot well.

3.       WATER FLOW
The condensed water is extracted from the hot well through condensate extraction pumps & sent to the boiler drum with the help of BOILER FEED PUMP (B.F.P.) before passing through low pressure heater and dearater. While loss in water is make up from C.S. Tank, which have D.M. Moor in it. The C.S. Tank is directly connected to hot well.
The water used in condenser is sent to cooling tower for cooling. After cooling this water is again sent to condenser with the help of circulating water pump. The loss is making from raw water pump house through clarifier pump house.

COMPONENTS DESCRIPTION

1.       WAGON TIPPLER:
It is the machine which is used to tip the coal from the wagon. The coal tipped is directly feed to conveyor belt. Its capacity is 12 wagon per hour.
2.       CRUSHER:
          It crushes the coal into small pieces.
3.       COAL MILLS:
In it small pieces of coal are converted into pulverized from. They are 6 in number.
4.       FURNACE:
          It is the chamber in which fuel burns & fire blows.
5.       BOILER DRUM:
          It contains water for boiling.
6.       ELECTROSTATIC PRECIPITATOR:
In this we have electrodes which attract fly ash and extract it from flue gases so that it cannot enter atmosphere.
7.       CHIMENY:
          It is used to release flue gases into the atmosphere.
8.       TURBINE:
Turbine is the part which revolves due to steam pressure. It is of three types.
            a)         High pressure turbine.
            b)         Intermediate pressure turbine.
            c)         Low pressure turbine.

9.       TURBO GENERATOR:
It is the main machine which produces 250 MW electricity .It is (H2O) water and H2 (Hydrogen) gas cooled therefore it is contained in cylindrical chamber.
10.     CONDENSER:
It condenses steam coming from low pressure turbine (L.P.T.) to hot water. By removing air and other non-condensable gases from steam while passing through them.



11.     COOLING WATER (C.W.) PUMP:
          This pump send water from cooling tower to condenser.
12.     COOLING TOWER:

It is used to coal the water its height is near about 143.5 mtrs. The hot water is led to the tower top and falls down through the tower and is broken into small particles while passing over the baffing devices. Air  enters the tower from the bottom and flow upwards. The air vaporizes a small percentage of water, thereby cooling water falls down into tank below the tower from where it is pumped to the condenser and cycle is repeated.
13.     RAW WATER PUMP HOUSE:
          It supplies raw water to the boiler.
14.     CLARIFIER PUMP HOUSE:
The water from raw is clear at clarifier by putting alum in it & filtering it & then supplied to the condenser.
15.     CONDENSATE EXTRACTION PUMP:
C.E.P. pump is used to extract the condense water from the hot well and supply to the deaerator after passing through L.P. heater & Economizer, so that high pressure steam in the cylinder can be created.
16.     LOW PRESSURE HEATER:
It is used to increase the temperature of water, in this way efficiency of system increases.



17.     DEAREATER:
It is used to remove air from water which is entrapped in the water molecules. It is very important part because the entrapped air effect air drum badly.
18.     BOILER FEED PUM (B.F.P.):
It is the heaviest drive in the plant & supply water to boiler drum from dearator.
19.     HIGH PRESSURE HEATER (H.P.):
In this temperature of water increases. Thus efficiency further increases.
20.     ECONOMISER:
In this flue gases exchange heat to the water to increase system  efficiency, causes saving in fuel consumption (5 to 10%). Economizer tubes are made up of steel either smooth or covered with fins to increase the heat transfer surface area.





CURRENT TRANSFORMER (C.T.)
SPECIFICATIONS REQUIRED FOR CTS ARE:
1.                  Class
2.                  Burden
3.                  Ratio
4.                  Resistance
5.                  Knee Point Voltage/Saturation
CTs can be broadly divided into two categories:-

1.       Metering CTs:
          Metering CTs are of very accurate for design of material having nickel iron alloys to reduce losses and having low flux density. The accuracy class of these CTs is 0/2%, 0.5% & 1.0%. Saturation level of these CTs is low i.e. 100 to 120% of In (CR secondary current) are thermal protection of meters.
Metering CTs are also known as Measuring CTs. These CTs cannot be used for protection purpose. The can only measure the current.

2.       Protection CTs:
Protection CTs are less accurate than metering CTs having high flux density. Saturation level of these CTs is high. Protection CTs are of two class i.e. 5P 10 & PS. 5P 10 is generally used for simple o/c & E/F protection where PS (purchaser specified) class is used for differential protection. These CTs are also used to measure current but up to specified limit.








GENERATOR
SPECIFICATION OF GENERATOR
KW/MW                         -210
P.F.                     -0.85
KVA                               -247000
KV                      -15.75
Amp                                -9050
Rotor volt           -310
EPM                                -3000
Rotor amp          -2600
Hz                                   -50
Phas                    -3
Connection-star star
Gas pressure       -3.5kg/cm2
Insulation class-B
SPEC- IE C34.1834.3 IS.5423
DIVIN-HARIDWAR
Coolants- H2O & H2

Supervision of cooling gas & cooling water temperature
          The adjustment or setting of cooling water flow should be made only by changing the adjustment f cooling water outlet valves. The inlet valve at header or valve at individual cooler section should be opened fully. The pressure of water at inlet of each cooler should be so adjusted as to keep the valve to 0.2kg/cm2 below the pressure of H2 in casing.


Operating value
MAX. SETTING

1. Stator water inlet temp.    to stator winding
  1. Stator water outlet temp. from stator winding.
40oC

60oC
45oC

85oC



ALARM HIGH
VERY HIGH
3.  Cold gas temp.
25o-44oC
44oC
55oC
4.  Hot gas temp.
40o-75oC
75oC
-
5.  Stator core temp.
<95oC
95oC
-
6.  Stator slot temp.
50o-75oC
75oC
-
7.  Rotor winding temp.
<115oC
115oC
120oC
8.  Humidity monitor dew point
<10oC
<-3oC
-



HYDROGEN COOLERS

The turbo generator has been provided with four nos. gas coolers mounted longitudinally in side stator body for cooling of hot gas, thus taking away the heat losses generated by rotor winding, stator core and windage losses. 

The gas cooler is a shell and tube heat exchanger consisting of cooling tubes with coiled copper wire around them to increase the surface area of cooling. Cooling water flow through the tubes while hydrogen flowing across coolers comes into contact with external surface of cooling tubes. Heat remove from hydrogen is dissipated through cooling water.

On both ends of coolers, water chambers are bolted to two plates. The outside flange of water chamber on slipping end is elastically fixed to stator body with the help of molded rubber gasket to allow free expansion of cooler where as on the turbine end; it is fixed rigidly to the stator. At turbine end, inlet and outlet water pipes are connected to water flange. In order to remove air from cooler while filling them with water, wind pipes are provided on slip ring end. Shut off valves are installed in pipe line at inlet and outlet of each cooler.


GENERATOR DESCRIPTION

210 MW GENERATOR
The generator is two pole type with cylindrical rotor using direct water cooling of stator winding, including phase connecting bus bar, terminal bushing and direct hydrogen cooling of rotor winding using gap pick up method. The losses in other parts of generator such as stator iron losses, friction & windage losses are removed by hydrogen circulating in casing.

The generator stator frame is of pressure-resistant and gas tight construction with four horizontal coolers in the frame itself forming part of ventilation and closed cooling circuit.

The generator consists of the following components as shown:

STATOR:
Ø   Stator body
Ø   Stator core
Ø   Stator winding
Ø   Gas coolers

ROTOR:
Ø   Rotor shaft
Ø   Rotor winding
Ø   Rotor retaining ring and other fittings
Ø   Field connections.

BEARING WITH BRUSH GEAR:
Ø   Bearing
Ø   Brush gear





STATOR
1.       Stator Body:
          The stator body is a totally enclosed gas tight fabricated structure, suitable ribbed internally to ensure high rigidity, it is designed mechanically to withstand internal pressure and forces as a result of unlikely event o explosion of hydrogen, air mixture without any residual deformation, Hydrogen gas coolers are housed longitudinally inside the stator body.

2.       Stator Core:
The stator core is made up of segmental, varnish insulated punching of Electro technical sheet with low loss factor. The stampings are assembled in an inter leaved manner on dove tailed core bars in order to damp out the oscillations so that magnetic vibration of stator core are not transferred to foundation through stator frame.

3.       Stator Winding:
          Stator bars, bus bars and terminal bushing are designed for direct water cooling. In order to minimize the eddy losses, the bars are composed of separately insulated strands, solid as well as hollow. The high voltage insulation is provided by thermosetting insulation using epoxy mica paper tape. With this insulating system, several layers of this tape are applied to the formed bars continuously and half over lapped. The no. of   layers i.e. the thickness of the insulation depends on the machine voltage. The insulation is also water proof and oil resistant. For protection of the stator winding against the effects of current forces in slots sides fillers, bottom spacers and top spacer below the slot wedge ensure permanently firm seating of the bars in the slot during operation. The water headers are insulated from stator body which permits measurement of insulation resistance of winding. The stator winding is connected inside the machine by connecting bus bars and brought out to nine bushing located in box of welded non magnetic steel below the generator at exciter end.



                            ROTOR
1.       ROTOR SHAFT:
          The rotor shaft is single piece forging manufacturing from ingots which are cast by vacuum degassing process. The longitudinal slots for insertion of the field winding are milled into barrel portion. The slots are distributed over the circumstances so that two solid poles are obtained. To ensure that only high quality and defect free forging is used, strength test, chemical analysis and ultra sonic test are carried out during manufacturing. After completion of rotor assembly the rotor is balanced at different sped in various planes and then subjected to an over sped test at 120% of rated sped for 2 minutes.

2.       ROTOR WINDING AND RETAINING RINGS:
          The rotor winding comprises several coils which are inserted into the slots and series connected in such a way that two coil groups enclosing one pole each are obtained. The centrifugal forces of the rotor overhauling windings are taken up by single piece retaining ring. The retaining rings consist of non-magnetic high strength steel in order to reduce stray losses.

3.       FIELD LEAD CONNECTIONS:
          a).   SLIP RINGS:
         The slip rings consist of helically grooved alloy steel ring shrunk on the rotor body shaft and insulated from it. For convenience in assembly both rings are mounted on a single common steel bush which has an insulating jacket premoulded on it. The complete bush with slip rings is shrunk on the rotor shaft.
The slip rings are provided with inclined holes for self ventilation. The helical grooves cut on the outer surface of the slip rings improve brush performance by breaking the pressurized air pockets that would otherwise get formed between the brush and slip ring surface.

          b).     FIELD LEAD:
        The slip rings are connected to the field winding through semi flexible copper leads and current carrying bolts placed radially in the shaft semi-flexible o thin copper sheets silver plated and copper leads are made up insulated by glass cloth impregnated with epoxy resin for low resistance and ease of assembly. The connection between current carrying bolt and field winding is done by a filed lead bar which has similar construction as that of semi-flexible copper lead.


BEARING AND BRUSH GEAR

          a).     BEARING:
          The generator bearings are pedestal type with spherical seating to allow self alignment and are supported on a separate pedestal on slip ring side and in L.P. casing on the turbine side. The bearings have provision of hydraulic shaft lifting during start up and turning gear operation. To eliminate shaft current, exciter side bearing and its pipes are insulated from earth. The bearing temperature detectors embedded in the Babbitt of lower half bearing liner. Vibrations on the bearing in horizontal and vertical direction are measured by vibration pickups mounted on the bearing pedestal.

          b).     BRUSH GEAR:
                  The rotor winding is solidity connected to slip rings by means of field lead bars, current carrying bolts, field lead core bars and flexible leads. The filed current to the rotor winding is provided through the brush gear.
The current carrying brush gear assembly is rigidly fixed on the extended part of bearing pedestal on the exciter side. There are two brush gear stands, each made up of two symmetrical silicon brass casting half rings, which are bottled at the top to make one stand assembly, kept vertically. These rings stands are designed as helical from one end to the other to achieve uniform wear of slip rings as well as carbon brushes and smooth removal of carbon dust all along the width of slip rings. The design of brush gear permits replacement of the brushes during normal operation condition. This complete gear stand assembly is rigid fitted in position on brush gear support which as a whole unit is to be fixed on to bearing.

          c).      SHAFT SEALS:
         In order to prevent the escape of hydrogen from the generator casing along the rotor shaft, shaft seals supplied with oil under pressure are used. To ensure perfect sealing, the oil pressure in the annular gap is maintained at a higher level than the gas pressure in the generator cas8ng. As long as the seal oil pressure in the annular gap between the shaft seal and the rotor exceeds the gas pressure in the generator. No hydrogen will escape from the generator housing. The shaft seal is provided with seal oil by a separate closed circuit system.
For the operation of generator the following auxiliary system are required.

d).     STATOR WATER COOLING SYSTEM:
1.                  Seal oil supply system
2.                  Gas system.
3.                  Stator water cooling system.

SEAL OIL SUPPLY SYSTEM:
The shaft seals are supplied with seal oil from a separate circuit which consists of following principle components:

Ø    Vacuum tank
Ø    AC seal oil pump 1 & 2
Ø    DC seal oil pump
Ø    Vacuum pump
Ø    Oil coolers
Ø    Sea; oil filters
Ø    Intermediate oil tank
Ø    Constant pressure regulating valve-1
Ø    Constant pressure regulating valve-2
Ø    Constant pressure regulating valve-3
Ø    Differential pressure regulating valve-1
Ø    Differential pressure regulating valve-2

GAS SUPPLY SYSTEM:
The gas system essentially consists of the following equipment:
Ø    H2 & CO2 cylinders
Ø    Pressure reducers
Ø    CO2 vaporizer
Ø    Pressure gauges
Ø    Gas drier
Ø    Humidity monitors
Ø    Purity measuring instruments

STATOR WATER COOLING SYSTEM:
The stator water supply system essentially comprises the following components:
Ø    Expansion tank
Ø    Stator water pump-A
Ø    Stator water pump-B
Ø    Stator water cooler-A
Ø    Stator water cooler-B
Ø    Stator water filter-A
Ø    Stator water filter-B

GENERATOR PROTECTION:

An AC generator forms the electromechanical stage of an overall energy conversion process that results in the production of electrical power. A reciprocating engine, or one of many forms of turbine, acts as a prime mover to provide the rotary mechanical input to the alternator. There are many forms of generating plant that utilize a variety of sources of energy available, e.g. Combustion of fossil fuels, hydro dams and nuclear fission. Generation schemes may be provided for base-load production, peak lopping or for providing standby power.
Electrical protection shall quickly detect the initiate shut down for major electrical faults associated with the generating plant and less urgently to abnormal operating conditions which may lead to plant damage.
Abnormal electrical conditions can arise as a result of a failure within the generating plant itself, but can also be extremely imposed on the generator. Common categories of faults and abnormal conditions which can be detected electrically are listed as follows:

Major Electrical Faults:
Ø    Insulation failure of stator windings or connections.

Secondary Electrical Faults:
Ø    Insulation failure of excitation system.
Ø    Failure of excitation system.
Ø    Unsynchronized over voltage

Abnormal Prime Mover or Control Conditions:
Ø    Failure of prime mover
Ø    Over frequency
Ø    Over fluxing
Ø    Dead machine energisation
Ø    Breaker flashover

System Related:
Ø    Feeding on un-cleared fault
Ø    Prolonged or heavy unbalance loading
Ø    Prolonged or heavy overload
Ø    Loss of synchronism
Ø    Over frequency
Ø    Under frequency
Ø    Synchronized over voltage
Ø    Over fluxing
Ø    Under voltage
In addition various types of mechanical protection may be necessary, such as vibration detection lubricant and coolant monitoring, temperature detection etc.
The action required following response of an electrical or mechanical protection is often categorized as follows:

Ø    Urgent shutdown
Ø    Non-urgent shutdown
Ø    Alarm only

An urgent shutdown would be required for example, if a phase to phase “Fault occurred within the generator electrical connection. A non-urgent shutdown right to sequential, where the prime mover may be shutdown prior to electrically unloading the generator, in order to avoid over sped. A non-urgent shutdown may be initiated in the case of continued” unbalanced loading. In this case, it is desirable that an alarm should be given before shutdown becomes necessary, in order to allow for operator intervention to remedy the situation.
For urgent tripping, it may be desirable to electrically maintain the shutdown condition with latching protection output contact, which would require manual resetting. For a non-urgent shutdown, it may be required that the output  contacts are self-reset, so that production of power can be re-started as soon as possible. Accordingly generator protection has been divided into three categories:

1.       Class A Protection:- Urgent shutdown /tripping without any time delay causing tripping of GCB, FB, UATs & Turbine simultaneously.
            (a) GT REF Protection (64 GT)
            (b) Generator differential Protection (87G)
            (c) Generator interterm fault (87G1)
            (d) Generator Reserve Power Protection (32G1)
                 Loss of Excitation (40G)
(e)    Backup impedance Protection 21G)
(f)    UAT Differential protection (87UAT)
(g)   GT/UAT Turbine (63 PTXG, 63 PTX)
(h)   Over voltage protection (59 G1)
(i)     Generator 100% stator E/F Protection (64G3)
(j)     Over fluxing Protection (99G)
(k)   AVR Trouble
(l)     Over Current for UAT (50UAR)
(m) Rotor E/F Protection (64F)
(n)   GT Overall differential protection (87 OA)
(o)    Generator 95% stator E/F Protection (64G2)

2.       Class B Protection:- Urgent shutdown /tripping delay of turbine first and tripping of  GCB, FB, UATs & Turbine on class A protection through LEP/RP protection (0.5% to 210 MW).
          (a)  Under Frequency Protection (81 G)
(b) GT Trouble relays
(c)  Loss of Excitation Protection (40 G1)
(d)  Negative Phase flow seq. Protection (46 G)
(e)  Stator water flow low and Conductivity high
(f)  UAT Trouble        

3.       Class C Protection:- Only GCB trip and unit can  be run on house load.
            (a)        Generator Backup impedance protection (21 G)
            (b)        GT Over current Protection (51 GT)
            (c)        Negative Phase seq, Protection.
          (d)       U/F Protection
            (e)        GT Natural O/C Protection (51 NGT)
          (f)        Generator Pole Slipping Protection (78 G)





Generator Differential Protection
Failure of stator windings, or connection isolation, can result in severe damage to the windings and state core. The extent of the damage will depend, upon the fault current level and the duration of the fault. Protection should be applied to limit the degree of damage in order to disconnection of the plant from the power generating plant, high –speed maintain system stability.


Two methods are commonly used. A biasing technique, where the relay setting is raised as through current increases. Alternatively, a high impedance technique, where the relay impedance is such element is insufficient for the relay to operate.


Biased differential protection
In a biased differential relay, through the current is used to increase the setting of the differential element or heavy through faults, it is unlikely  that the CT outputs at each zone end will be identical, due to the effects of CT saturation. In this case a differential current can be produced. However, the biasing will increase the relay setting, such that the differential spill current is insufficient to operate the relay. Through the current is calculated as the average of the scalar sum of the current entering and leaving the zone of protection. This calculated through current is then used to apply percentage bias to increase the differential setting.


Setting Guidelines  For Biased Differential Protection
The differential current setting, should be set to a low setting to protect as much of the machine winding as possible. A setting of 5% of rated current of machine is generally considered to be adequate. The threshold, above which the second bias setting is applied, should be set to 120% of the machine rated current.
The initial bias slope setting should be set to 0% to provide optimum sensitivity for internal faults. The second bias slope may typically be set to 150% to provide adequate stability for external faults. These settings may be increased where low accuracy class CTs is used to protection. 




High impedance differential Protection
The high impedance principle is best explained by considering a differential scheme where one CT is saturated for an external fault, as shown in Figurer.
If the relay circuit is considered to be very high impedance, the secondary current produced by the healthy CT will flow through the saturated CT. If the magnetizing impedance of the saturated CT is considered to be negligible, the maximum voltage across the relay circuit will be equal to the secondary fault current multiplied by the connected impedance, (RL3+R14+RCT12)
The relay can be made stable for this maximum applied voltage by increasing the overall impedance of the relay circuit, such that the resulting current through the relay is less than its current setting. As the impedance of the relay input alone is relatively low, a series connected external resistor is required. The value of this resistor, RST, is calculated by the formula shown in Figure 3. An additional on linear resistor, Metrosil, may be required to limit the peak secondary circuit voltage during internal fault conditions.




To ensure that the protection will operate quickly during an internal fault the CTs used to operate the protection must have a knee point voltage of at least 4Vs.

USE OF “METROSIL” NON –LINEAR RESISTORS
Metrosils are used to limit the peak  voltage developed by the below the insulation level of the current transformer, relay and interconnecting leads, which are normally able: to withstand 30000V peak.
The following formulae should be used to estimate the peak transient voltage that could be produced for an internal fault will be a function of the current transformer knee point voltage and the prospective voltage that would be produced for an internal fault if current transformer saturation did not occur. This prospective voltage will be a function of maximum internal fault secondary current, the current transformer ratio, the current transformer led resistance to the common point, the relay lead resistance and the stabilizing resistor value.
Vp=2V2 Vk (Vf-Vk)
V,=1(RCT+2RL+RST)where
Vp=peak voltage developed by the CT under internal fault conditions.
Vk= current transformer knee-point voltage
V= Maximum voltage that would be produced if CT saturation did not occur.

Setting guidelines for Stator earth fault protection function (51N)
·                     Current operated from a CT in the neutral earth path.
·                     Two independent tripping stages.
·                     First stage tripping can incorporate either a definite time or standard inverse type IDMT delay.
·                     Second stage tripping can be instantaneous or definite time delayed.
·                     Immune to third harmonics.


Applied to directly connection generators.
The protection must be time graded with other earth fault protection; the setting employed should be less than 33% of the earth fault level.
In case of direct generator connection, it is common that only one generator of a parallel set is earthed at any one time, with the arth connections of other machines left open, if the generating plant can also be run directly in parallel with a medium voltage public supply, it is a common requirement that all generator earth connections are left open during parallel operation. In such circumstances, the main earth fault protection element (le>) will only be operational for an earthed machine, It will provide primary earth fault protection for other machines and the rest of the power system and thermal protection for the earthing resistor.
For indirectly connected applications, the time-delayed earth fault protection function may be employed in one of two ways.
1.                  To measure earth fault current indirectly, via a CT in the secondary circuit of a distribution transformer earthing arrangement.
2.                  To measure earth fault directly, via a CT in the generator winding earth connection.
With the first mode of application, the current operated protection function (51N) may be used in conjunction with voltage operated protection function (59N), measuring the distribution transformer secondary voltage. This is a complementary arrangement, where the voltage operated protection function (59N) is able to operate in the event of an open –circuited loading resistor and the current operated protection function (51N) is able to operate in the event of a short circuited resistor.

The second mode of application would be used for cases of direct resistive earthing. For distribution transformer earthing, this mode offers the advantage of being able to respond to an earth fault condition that leads to a flashover of the distribution transformer primary connections. Such a primary short circuit would render protection on the secondary side of the transformer inoperative and it would also result in a very high and damaging primary earth fault current.

In either mode of application, the main stator earth fault current operated protection element (le>) should be sent to have a primary sensitivity of around 5% of the maximum earth fault current as limited by the earthing impedance. Such a setting would provide protection for upto 95% of the generator stator windings. The probability of an earth fault occurring in the lower 5% of the generator ‘winding would be extremely low, due to the fact that the winding voltage with respect to earth is low in this region.

The time characteristic and setting of the main current operated protection element (le>) should be set to prevent false operation during HV system earth fault clearance, where a transient generator earth connection current may appear as –result of the inter-winding capacitance of the generator step-up transformer. The protection element should also co0operate with operation of generator VT primary fuses, for a VT primary earth fault, and with VT secondary fuses for a secondary earth fault on a VT that has its primary windings earthed. Depending on the VT fuse characteristics, and on HV system earth fault protection clearance times, a definite time delay anywhere between 0.5s and 3.0s would be appropriate.   
 In machines with complex winding connection arrangements, e.g. some hydro generators, the probability of a fault occurring in the stator winding star-end region (first 5% of the winding) might be higher. For a higher rated, expensive machine such increased probability may prompt operators to apply 100% stator earth fault protection. A suitable 100% stator earth fault protection scheme can be applied in these cases.

A setting of 5% of the earth fault level should be applied for applications where the differential protection provides less than 95% coverage of the stator winding.

Applied to in-directly connected generators

(With the generator earthed via a distribution transformer)
Can be supplied from a CT in either the primary or secondary circuit of the Distribution transformer.
With a CT in the primary circuit, the protection has the advantage of being able to detect an earth fault which causes flashover of the primary winding of the distribution transformer. With the CT in the secondary circuit the protection has the advantage of detecting a short circuit across the loading resistor. A sensitive 5% setting can be applied to the first tripping stage, a short time delay can be applied to stabilize the protection against small earth current due to VT failures or earth leakage during HV system faults.
The second tripping stage can be utilized as a high set a 10% setting and instantaneous operation ensures fast clearance of generator earth faults.

100% stator Earth Fault Protection:
The conventional unit type generator has the neutral earthed through a resistance loaded distribution type transformer. For a single ground fault near the neutral end of the winding, there will be proportionately less voltage available to drive the current through the ground, resulting in a lower fault current and a lower neutral bus voltage.

6.6 K.V. CIRCUIT BREAKER
A circuit breaker is device which:-
  • Makes or breaks a circuit either manually or by remote control under normal conditions.
  • Breaks a circuit automatically under fault conditions.
Thus a circuit breaker is just a switch which can be operated under normal & abnormal conditions both automatic or manually to perform this operation, a circuit breaker is essential consisting of fixed and moving contacts called electrodes. When a fault occurs on power system, the trip coil of circuit breakers energized which pulls apart moving contacts. Thus open the circuit dc supply is used for the operation of circuit breaker on the basis of medium used for extinction the circuit breakers are classified as:
  1. OIL CIRCUIT BREAKERS
  2. AIR BLAST CIRCUIT BREAKER
  3. SULPHER HEXAFLURID CIRCUIT BREAKER        
                                           
1.       OIL CIRCUIT BREAKER: -                            
                               It is well known that when a circuit carrying a large current is broken, an arc occur at that point where the contacts are separate, the arching is specially served when high voltages are involved and if a short circuit occur on a high voltage cable which is supplied from large power station. The arc would be powerful to bridge the contacts of the switch and destroy it by burning the device is employed as a oil circuit breaker. Oil breaker posses the property of always breaker an alternative current at its zero value.                              
 These switches are suitable for a maximum voltage of 6.6kv the contact of these switches, which break high tension circuit are put in a box in which we have create a vacuum .to ensure rapid & effective rupture of the circuit. When the arc occurs, there is no medium in the box and the arc slow down easily, as it is difficult to maintain high value of vacuum under the condition of commercial manufacture and operation.

Oil is the best voltage insulator with stress level upto 107v/cm limited only by emission from the electrode surface. This decreases to less then 105v/cm for gaps for coverall centimeters. The dielectric constant of all dialectical gases is very nearly hinting.



SPECIFICATION OF OIL BREAKER:-

                             TYPE – BIBARE.T, BKRT TYPE.
                             VOLTAGE – 7.2KV
                             FREQUENCY – 50Hz
                             SHORT TIME CURRENT – 40A
                             DURATION – 15
                             MAKING CAPACITY – 100 KAP
                             POWER FECTOR WITH STAND – 27KV
                             IMPULSE WITH STAND – 60KVP
                             SHUNT TRIP COIL – 220V
                             SPRING RELEASE COIL – 220V

2.       AIR BLAST CIRCUIT BREAKER:


3.  SULPHER HEXAFLURID CIRCUIT BREAKER:



6.6 KV UNIT SWBD # 8CA

1) BFP#8C                                      4600KW
2) ACWP#8A                                   550KW
3) CWP#8A                                                1965KW
4) CEP#8A                                       325KW
5) SPARE MOTOR FEEDER         2400KW
6) BFP#8A                                      4600KW
7) MILL#8AB                                 2400KW
8) PAFAN#8A                                1550KW
9) FDFAN#8A                                  790KW
10) IDFAN#8A                               1800KW
11) 2500KVA                                 6.6/0.433KV
      OIL FILLED SPARE TRANSFORMER FEEDER.
12) 2000KVA                                 6.6/0.433KV
       DRY TYPE UNIT SERVICE TRANSFORMER # 8DAT01
13) 2500KVA                                 6.6/0.433KV
       OIL FILLED ESP SERVICE TRANSFORMER # 8DBT01
14) FEEDER PT
15) INCOMER FROM UAT#8A
16)  BUS PT
17) TIF FROM 6.6KV STATION SWBD#OCC

6.6KV STATION SWBD # OCC

1)      TIE TO 6.6KV UNIT SWITCH BOARD # 8CA
2)      O/G FEEDER TO 6.6KV COAL HANDLING SWBD # OCE     
3)      1000KVA                                         6.6/0.433KV
 OIL FILLED SPARE TRANSFORMER   CP #8C                    
4)   TIE TO 6.6KV STATION SWBD#OCA.
 5)  1000KVA                                          6.6/0.433KV

       OIL FILLED CHP. TRANSFORMER # ODHT02.
 6) 2000KVA                                           6.6/0.433KV
  OIL FILLED SWITCHYARD TRANSFORMER#02.
 7) 2000KVA                                           6.6/0.433KV
      DRY TYPE UNIT SERVICE TRANSFORMER#ODATO2.
 8)1250KVA                                             6.6/0.433KV
OIL FILLED RAW WATERTRANSFORMER # ODGT02.
 9) AIR COMPRESSOR # C                     400KW
    10)     CEP # 8C                                     325KW
    11)     MILL#8EF                                 2400KW
    12)     SPARE MOTOR FEEDER          2400KW
    13)     BUS PT.
    14)     FEEDER PT.
    15)     INCOMER FROM STATION TRANSFORMER#B.

6.6KV STATION SWBD#OCD

1)                INCOMER FROM STATION TRANSFORMER#B.
2)                FEEDER PT.
3)                BUS PT.
4)                SPARE MOTOR FEEDER        1800KW.
5)                PAFAN # 8C                              1550KW.
6)                AIR COMPRESSOR #D            400KW.
7)                ID FAN # 8C                              1800KW.
8)                1600KVA                                   6.6/0.433KV    
OIL FILLED SPARE TRANSFORMER   FEEDER.
9)                1250KVA                                    6.6/0.433KV                                                                  
 OIL FILLED WATER TREATEMENT #ODBTO2.
10)           2000KVA                                    6.6/0.433KV                              
               DRY TYPE STATION SERVICE TRANSFORMER # ODBT02.                
11)     630 KVA                                    6.6/0.433 KV
          OIL FILLED ASH SILD TRANSFORMER #ODTT02.
12)     1600KVA                                    6.6/0.433KV    
          OIL FILLED FIRE FIGHTING TRANSFORMER #ODCT02.
     13)    TIE TO 6.6KV STATION, SWBD#OCB.
14)    O/G FEEDER TO 6.6KV ASH HANDLING SWBD # OCF.
15)    TIE TO 6.6KV UNIT SWITCH BOARD # 8CB.

6.6 KV UNIT SWBD#8CB

1)                TIE FROM 6.6KV STATION SWBD#OCD.
2)                BUS PT.
3)                INCOMER FROM UAT # 8B.
4)                FEEDER PT.
5)                2500 KVA                                   6.6/0.433 KV
OIL FILLED ESP SERVICE TRANSFORMER # 8DBT02.
6)                2000 KVA                                   6.6/0.433KV
DRY TYPE UNIT SERVICE TRANSFORMER # 8DAT02.
7)                2500KVA                                    6.6/0.433KV
OIL FILLED SPARE TRANSFORMER FEEDER.
8)                ID FAN# 8B                                1800KW.
9)                FDFAN# 8B                                790KW.
10)           PAFAN# 8B                                1550KW.
11)           MILL 8CD                                   2400KW.
12)           BFP# 8B                                      4600KW.
13)           SPARE MOTOR FEEDER                   1800KW.
14)           CEP# 8B                                                325KW.
15)           CWP# 8B                                     1965KW.
16)           ACWP# 8B                                  550KW.
17)    BFP# 8C                                 4600KW.        


                            

MOTOR

HIGH TENSION MOTOR
HIGH TANSION MOTORS OPERATED AT HIGH VOLTAGES

IN PANIPAT THERMAL POWER STATION, THESE MOTORS ARE OPERATED AT 6.6kv SOME OF THESE MOTORS ARE AS FOLLOWS:-
1. CIRCULATING WATER (C.W.) PUMP MOTERS:-
              A). SPACIFICATIONS:-
                    I.          MAKER – B.H.E.L
                        II.        CAPACITY (K.W.)-1265KW
iii.                RATED VOLTAGE(VOLTS)-6600V
iv.                RATED R.P.M.-493
v.                  RATED CURRENT-140A
vi.                CONNECTINS-STAR
vii.              DUTY-CONTINUOUS
viii.            INSULATION CLASS-F
ix.                INSTALATION POSITION-VERTICAL
x.                  PHASE-3

            b). FUNCTION:- 
C.W PUMP IS USED TO CIRCULATE COOLING WATER TO THE CONDENSER; SO THAT HIGH PRESSURE LEFT OUT STEAM IN THE L.P. CYLINDER CAN BE CONVERTED INTO WATER.

2. C.E.P. MOTOR:-
            a) SPECIFICATIONS:-
                   i.          MAKE-B.H.E.L.
                        ii.         CAPACITY-500KW
                        iii.        RATED VOLTAGE-6600V
iv.              RATED R.P.M.-1482
v.                 RATED CURRENT-52.8A
vi.              CONNECTIONS-STAR
vii.            DUTY-(2WRKING, 1 STANDBY) CONTINUOUS
viii.         INSULATION CLASS-F
ix.              INSTALATION POSITION-VERTICA
x.                 PHASE-3           

 b). FUNCTION:-
C.E.P. PUMP IS USED TO EXTRACT THE CONDENSATE WATER FROM THE HOT WELL AND SUPPLY TO THE DEAREATOR AFTER PASSING THROUGH L.P. HEATER AND ECONOMIZER, SO THAT HIGH PRESSURE STEAM IN THE CYLINDER CAN BE CREATED.

3. BOILER FEED PUMP(B.F.P.) MOTOR:-
                        No. of motor used = 3(6A, 6B, 6C)
            a). SPECIFICATION:-
                   i.          MAKE B.H.E.L.
                        ii.         CAPACITY-3500KW
iii.              STATOR VOLTAGE-6600V
iv.              RATED R.P.M.-1481
v.                 RATED CURRENT-360A
vi.              CONNECTION-STAR
vii.            DUTY-(2WRKING, 1 STANDBY) CONTINUOUS
viii.         INSULATION CLASS-F
                         Xi       PHASE-3
             b). FUNCTION:- 
ITS FUNCTION IS TO SUPPLY THE WATER TO WATER TO THE BOILER DRUM.  IT TAKES THE WATER FROM THE DELINEATOR BY CREATING A STRONG SUCTION.

4. COAL MILL MOTOR:-
                   No. of motor used = 3(6A, 6B, 6C)
          a). SPECIFICATION:-
i.                   MAKE B.H.E.L.
ii.                 CAPACITY-2400KW
iii.              STATOR VOLTAGE-6600V
iv.              RATED R.P.M.-992
v.                 RATEDCURRENT-40.7A
vi.              CONNECTION-STAR
vii.            DUTY- CONTINUOUS
viii.         INSULATION CLASS-F
ix.              INSULATION POSITION-HORIZONTAL
x.                 PHASE-3

             b). FUNCTION: -
THE FUNCTION OF THE COAL MILL IS TO GRIND THE COAL PIECES OF THE FINE POWDER (PULVERIZED FORM) i.e. UPTO TO SIZE OF 25 MICRON.

5. COAL CRUSHER:-
No. of motor used = 2(6A, 6B)
          a). SPECIFICATION:-
i.                   MAKE – N.G.F.E
ii.                 CAPACITY-600KW
iii.              RATED VOLTAGE-6600V
iv.              RATED R.P.M.-747
v.                 RATED CURRENT-72A
vi.              CONNECTION-STAR
vii.            DUTY- CONTINUOUS
viii.         INSULATION CLASS-F
ix.              PHASE-3

b). FUNCTION:-
IT’S FUNCTIONED TO CRUSH THE BIG SIZE COAL PIECES TO A SIZE OF 25 MM SQ. WHICH ARE THEN CARRIED TO THE BANKERS ON THE CONVEYOR BELT.

6. PRIMARY AIR FAN (P.A. FAN) MOTOR:-
            No. of motor used = 3(8A, 8B, 8C)
          a). SPECIFICATION:-
i.                   MAKE B.H.E.L.
ii.                 CAPACITY-1250KW
iii.              RATED VOLTAGE-6600V
iv.              RATED R.P.M.-1487
v.                 RATED CURRENT-132A
vi.              CONNECTION-STAR
vii.            DUTY- CONTINUOUS
viii.         INSULATION CLASS-F
ix.              PHASE-3

              b).  FUNCTION:-
ITS FUNCTION IS TO CARRY PULVERIZED COAL FROM THE COAL MILL TO THE FURNACE FOR ITS IGNITION.  IT CREATES A STROP IT CREATES A STRONG DRAFT OF AIR THAT CARRIES THE POWDERED COAL.

7). FORCE DRAUGHT (F.D.) FAN MOTOR:-
           a). SPECIFICATION:-
i.                   MAKE B.H.E.L.
ii.                 CAPACITY-750KW
iii.              RATED VOLTAGE-6600V
iv.              RATED R.P.M.-1490
v.                 RATED CURRENT-80.2A
vi.              CONNECTION-STAR
vii.            DUTY- CONTINOUS
viii.         INSULATION CLASS-F
ix.              PHASE-3


           b). FUNCTION:-
ITS FUNCTION IS TO SUPPLY FRESH AIR TO THE FURNACE FOR THE PROPER IGNITION OF COAL IN SIDE THE FURNACE.

8. INDUCED DRAFT (I.D.) FAN MOTOR:-
          a). SPECIFICATION:-
i.                   MAKE B.H.E.L.
ii.                 CAPACITY-1300KW
iii.              RATED VOLTAGE-6600V
iv.              RATED R.P.M.-750
v.                 RATED CURRENT-147.5A
vi.              CONNECTION-STAR
vii.            DUTY- CONTINOUS
viii.         INSULATION CLASS-F
  ix      PHASE -3



b). FUNCTION:-

ITS FUNCTION IS TO DISCHARGE THE FLUE GASSES TO THE ATMOSPHERE
THROUGH THE CHIMNEY AFTER PASSING THROUGH THE PRECIPITATOR.

9. BEARING COOLING WATER PUMP MOTOR:-
         a). SPECIFICATION:-
i.                   MAKE CROMPTON CREAVESES.
ii.                 CAPACITY-335KW
iii.              RATED VOLTAGE-6600V
iv.              RATED R.P.M.-980
v.                 CONNECTION-STAR
vi.              DUTY- CONTINOUS
vii.            INSULATION CLASS-F
viii.         INSTALTION POSITION-HORIZONTAL
ix.              PHASE-3

b). FUNCTION:-
IT SUPPLIES COOLING WATER TO THE MOTOR & OTHER AUXILLARY FOR
COOLING PURPOS.

LOW TENSION MOTOR

LOW TENSION MOTORS ARE THOSE WHICH ARE OF 415V. THEY ARE
MAINLY USED IN H.T MOTOR AUXXILLARY. 

1. B.C.W.DRAIN MOTOR (BEARING COOLING WATER):-    
 A) SPECIFICATION:-
                          i). CAPACITY-136KW
                          ii). RATED R.P.M-987
                          iii).RATED CURRENT-43A
                          iv).FREQUENCY-50HZ
                          v). MAKE –KRILOSKER
                          vi).INSULATION CLASS-B

       B) FUNCTION:-
                               IT PUMP THE D.C WATER TO THE BEARING OF HT MOTER FOR THE PURPOSE OF COOLING.

2. SEAL WATER PUMP MOTER:-
        A) SPECIFICATION:-
                         i).  CAPACITY-25KW
                         ii). RATED R.P.M-1479
                         iii).RATED CURRENT-43A
                         iv).FREQUENCY-50HZ
                         v). PHASE-3
                         vi). MAKE –NGEF
                         vii).INSULATION CLASS-B

      B) FUNCTION:-
IT PROVIDES A LAYER OF WATER TO THE LOWER POSITION OF BOILER IN ORDER TO SEAL IT FROM THE ENTERY OF ATMOSPHERIC AIR.

3. SEAL WATER VAPOUR EXHAUST FAN:-
         A) SPECIFICATION:-
                         i). CAPACITY-1.5KW
                         ii). RATED R.P.M-6205
                         iii).RATED CURRENT-3.1A
                         iv).FREQUENCY-50HZ
                         v). PHASE-3
                         vi). MAKE –KILOSKER
                         vii).INSULATION CLASS-B

B) FUNCTION:-
                        IT PREVENTS THE ENTERY OF AIR BUBBLES IN THE TURBINE CYLINDER BY PROVIDING THE OPPOSITE PUSH.

4.  CENTIFUGE PUMP MOTOR :-
          A) SPECIFICATION:-
                         i). CAPACITY-7.5KW
                         ii). RATED R.P.M-1440
                         iii).RATED CURRENT-14.2A
                         iv).FREQUENCY-50HZ
                         v). PHASE-3
                         vi). MAKE –CROMPTION GREAVES
                         vii).INSULATION CLASS-B

      B) FUNCTION:-
                                TO CENTRIFUGE THE VAPOUR THAT ENTERS BY   CHANGE IN TURBINE AN REMOVE THEM.






5.  ASH SULLRY PUMP MOTOR:-
          A) SPECIFICATION:-
                          i). CAPACITY-100KW
                          ii). RATED R.P.M-1485
                          iii).RATED CURRENT-176A
                          iv).FREQUENCY-50HZ
                          v). PHASE-3
                          vi). MAKE –NGEF
                          vii).INSULATION CLASS-B

B) FUNCTION:-
                               IT PUMP ASH SLURRY TO THE ASH DISPOSAL AREA .IT PUMPS THE SLURRY WITH GREAT PRESSUR TO THE OUT SIDE ,IT IS KNOWN OF THE HIGH PRESSUR OF HANDLING FAN AND IT MAKES SLURRY OF ASH AND WATER.

6.  EMERGENCY OIL PUMP:-
      A) SPECIFICATION:-
                           i). CAPACITY-15KW
                           ii). RATED R.P.M-1425
                           iii).RATED CURRENT-125A
                           iv).FREQUENCY-NA (DC)

      B)FUNCTION:-
                           TO PROVIDE OIL THE SHAFT AND BEARING  OF THE  TURBINE IF    SEAL OIL PUMP AND TAKING OIL PUMP FAILS.

7.  RAW WATER MOTOR PUMP:-
            A) SPECIFICATION:-
                         i). CAPACITY-90KW
                         ii). RATED R.P.M-1450
                         iii).RATED CURRENT-154A
                         iv).FREQUENCY-50HZ
                         v). PHASE-3
                         vi). MAKE –KILOSKER
                         vii).INSULATION CLASS-B             
   
B) FUNCTION:-
     IT  IS USE TO PUMP RAW WATER FROM THE  LAKE TO THE PLANT.
8.  INSTRUMENT AIR COMPRESSOR :-
               A) SPECIFICATION:-
                        i). CAPACITY-105KW
                        ii). RATED R.P.M-1485
                        iii).RATED CURRENT-184A
                        iv).FREQUENCY-50HZ
                        v). PHASE-3
                        vi). MAKE –KILOSKER
                        vii).INSULATION CLASS-B         

 B) FUNCTION:-
                         IT IS USED TO COMPRESS THE AIR USED THE AIR USED TO CANTROL PNEUMATIC CANTROLLED INSTRUMENTS AT A PRESSUR 6 TO 7 KG/CM CUBE.

9.  SERVICE AIR COMPRESSOR:-
             A) SPECIFICATION:-
                        i). CAPACITY-30KW
                        ii). RATED R.P.M-1485
                        iii).RATED CURRENT-184A
                        iv).FREQUENCY-50HZ
                        v). PHASE-3
                        vi). MAKE- NGEF
                        vii).INSULATION CLASS-B



  B) FUNCTION:-
                             ITS FUNCTION IS SIMILER TO INSTRUMENT AIR-  COMPRESSOR .
10.  CLARIFIER WATER PUMP MOTOR:-
                 A) SPECIFICATION:-
                    i). CAPACITY-30KW
                    ii). RATED R.P.M-1470
iii).RATED CURRENT-43A
iv).FREQUENCY-50HZ
v). PHASE-3
vi). MAKE- CROMPTON
vii).INSULATION CLASS-B

B) FUNCTION:- 
IT PUMP THE FILTERED WATER FROM CLERIFIER TO D.M. WATER TREATEMWNT PLANT.

TRANSFORMERS

The Transformer is the most convenient & economical device for transfer of power from one
voltage to another voltage at the same frequency. It works on the principle of
electromagnetic induction. There is hardly any installation without a transformer. Due to this
equipment it has been possible to transmit bulk power to load centers from far off power
houses and to various machineries and switchgears of the power plant. Transformers are of
two types:-



STEP-UP TRANSFORMER –
Which step-up the voltage at secondary side called step up transformer.

STEP-DOWN TRANSFORMER –
Which step-down the voltage at secondary side are called step-down transformer.
MAIN PARTS OF POWER TRANSFORMERS
# Primary winding
# Secondary winding
# Oil tank
# Drain coke
# Conservator
# Breather
# Tubes for cooling
# Transformer oil
# Earth point
# Explosion vent
 # Temperature gauge
 # Buchholz relay
 # Primary terminals
 # Secondary terminals
SOME ACCESSORIES OF TRANSFORMERS ARE DESCRIBES BELOW:-
1. Oil conservator: - Oil conservator is a short of dump mounted on the top of transformer. A level indicator is fixed to it, which gives alarm at low level. Conservator is connected through a pipe to the transformer tank containing oil. This oil produced & so the oil level in conservator is left open to the atmosphere through a breather so that the extra air may go out or come in.

2.  Breather:- The breather is a box containing calcium chloride or silica gel to absorb moisture of our entering the conservator as it is well known fact that the insulating property of the transformer oil is lost if a small amount of moisture enter in it. So dry air is allowed to pass though the breather. When oil level in oil conservator changes, air moves in & out of the conservator. This action is known as breathing. Dry silica gel is of the blue color it turns pale pink as it absorbs moistures. The wet silica gel can be regenerated by drying.

3.  Buchholz relay:- This relay is a gas- actuated relay which is meant for the protecting of oil immersed transformer from insulation failure, core heating or any type of internal fault which may cause the heating of oil beyond the specified temp. due to any internal fault, oil is heated-up & oil vapour so formed causes either the alarm circuit (for less fault) or trip the circuit (for server fault).



4.  Explosion vent: - It is also a safety device of the transformer which protects the transformer tank from gases induced by & any type of short circuit in the transformer. This consists of a vertical pipe closed by a diaphragm of thin bakelite sheet. This diaphragm burst or slides out is case of abnormal pressure inside the tank. A diverter plate is used at the bottom of the explosion vent to ensure that gases produced inside the transformer are directed toward the buchholz relay & don’t get collected inside the ventilation and equalize the pressure on each side of the diverter plate.

5.  Tem. Indicator: - It is also a protective device fitted to the transformer to indicate temp. of transformer oil. For measuring temp. of the oil, bulb of the vapor pressure type transformer is placed in the hot oil & dial of the transformer is mounted outside the tank. Two indicating pointers black and red are provided. Alarm contacts are predetermined permissible higher temperature is reached under abnormal operating conditions.

6. Bushing: - The serve as supports and insulation of the bus bars and transformer thermal. The bushing consists of porcelain shell body. Upper and lower locating washer used for fixing the position of bus bar and mounting flange with the hole drilled for fixing bolt and it is supplied with an earthing bolt.

7.   Magnetic oil gauge: - The magnetic oil level gauge supervises the level of oil in the conservator tank. The oil level gauge is provided on the transformer are of dial type with minimum and maximum level marking and a pointer which indicate the level of oil in the conservator sometime the scale is also graduated for oil temperature o the basis of its level.

8.   Tap changer: - The voltage control of transmission and distribution system is obtained by Tap Changer tap changer are either on load or off load tap changer, tap changer is fitted with the transformer for adjusting secondary voltage.

SWITCHYARD COMPONENTS

1.       SWITCH-GEAR: - Switch gear is a control switch that controls the operation of a power circuit. The two function of a switch in power systems are:-
i)          To permit the transmission lines to be convenient put into and taken out from service.
ii)         To disable the some plant and lines when these become faulty. To be rapidly and safety isolated by automatic means.
The first of these can be served by relatively simple switches the second however require circuit breakers, which are more robust & capable of breaking the largevalue of fault power that results in faults on major power system since all plants and lines are liable to develop faults as a results of mechanical damage, electrical breakdown, errors in operation etc. The simple isolators switch in favour of automatic circuit breakers even for switching function. The whole switchgear assembly consists of two parts:

1.       PANEL:
            Panel consists of protective relays. Mounting of potential transformer, current transformer, ammeter, voltmeter & energy meter. The potential transformer is mounted on the panel. The primary is connected to 11KV & the reduce voltage from the secondary is given to energy meter as line voltages & for protective purposes.
2.       TROLLEY:
           The trolley consists of current carrying contracts called electrodes. These are normally engaged but in predetermined conditions. Separate to interrupt the circuit,when the contact are made.

BUS BAR ARRANGEMNT

            Conductors to which a number of circuits are connected called bus-Bars. In power plants, shut                      down results disconnection of supply to a large are. Hence to avoid shut down the major plants                     should have elaborate bus bar arrangement with duplicat buses. Alternative supply arrangement                     section etc. The extra high voltage equipments such as isolators circuit breaker are generally costly                  hence unnecessary equipment should not be provided.

1.       SINGLE BUS BAR ARRANGEMENT: -
         The single arrangement consists of a single (three phase) Bus Bar to which various feeders are connected. In case of fault or maintenance of Bus. The entire bus bar has to be de-energized and the total shutdown results. This scheme is most economical and simple.

2.       DOUBLE BUS BAR ARRANGEMENT: -
The double bus systems provide additional flexibility, continuity of supply and permit
periodic maintenance. In the event of fault on the bust bar the other can be used. The
figure shows to the bus bar arrangement. There are two buses called main bus and
reserve bus. The two buses can be closed so as to connect two buses while
transferring the power to the reserve bus 

i)                    Closed bus coupler the two buses are now at same potential.
ii)                  Closed isolator on reserve bus.
iii)                Open isolator on main bus.

                    LIGHTING ARRESTER
A lighting arrester is device, which proves low impedance path for the flow of currentbetween the line and earth when the systems voltage increases more than the desire valueand regains its original properties of an insulator at normal voltage. It is connected betweenline and earth at the switchyard near the transformer.


The lighting arresters are extensively used for protection of transformers, switch gears andelectrical equipments of over head lines, power houses and sub-station. There are also use toprotect the line and equipments from sky lighting.

Following are the main type of lighting arresters.
i)                    Horn gap lighting arrester.
ii)                  Expulsion type lighting arresters.
iii)                Oxide film lighting arrester.
iv)                Pellet lighting arrester.
v)                  Thyrite lighting arrester.
vi)                Auto value lighting arrester.

EXPULSION TYPE LIGHTING ARRESTER
IT CONSISTS OF:-
i)                    A tube made of fibre which is very effective gas evolving materials.
ii)                  An isolating spark gap (or external series gap)
iii)                An interrupting spark gap inside the fibre tube.
During operational, ARC due to impulse spark or inside. The fibrous tube causes some fibre material of the tube volatize in form of gas, which is expelled through a vent from the bottom of the tube. Thus extinguishing the ARC just like in circuit breaker since the gases generated have to be expelled one of the Electrode is hollow and diverter is open at its lower end.

THYRITE LIGHTING ARRESTER:-
This type of lighting arrester consists of number of discs of inorganic ceramic compound. These discs are placed in a series having some gap in between them and are sealed in a porcelain tube. This tube has metallic cap and electrodes at its end.
The compound used for disc serves as an insulator but changes to a good conductor when voltages across it rise to a certain predetermined value. It is used upto 220 KV systems. 

210 MW TURBO GENERATOR

GENERAL: -
Modern features of direct cooling by water & hydrogen are incorporated in the 210 mwturbo generator, thus evolve an economical & reliabledesign. The machine is provided with a fast acting excitation system & dependableauxiliary service to give prolonged trouble free operation over the years. All the material that goes into the manufacture of this machine subjected to various test as per national & international standards. Each component undergoes series of stage wise tests. Description of various parts is given below:- 



      1.      STATOR WINDING AND INSULATION: - The stator has a three phase, double layer, short chorded, bar type winding, having two parallel parts. Each coil side consists of glass insulated solid and hollow conductors with cooling water passing through the patter. The elementary conductors are rebel transposed in the slot position of winding to minimize eddy current losses.
Adequate protection is provided to avoid corona & other discharges in the slots, the sides are firmly held in the position by fibrous slot wages, which are mechanically strong and have high dielectric properties. The overhang portion of the coil is securely lashed with glass chord to bondage rings & special brackets of non magnetic steel, which are in turn, fixed to the core press rings. On short circuits the process between the conductors tends to open the cone formed by overhang portion of the coils, but the movement is effectively presented by supports & lashings.

     2.      DISTILLATE HEADERS OR STATOR WATER HEADER: - Ring type water heads, made of copper are provided separately for distillate inlet & outlet in the stator on turbine side. The headers are supported on insulators and isolated from stator body. The winding ends are than ultrasonically tested. Individual bars provided with water inlet/outlet connections made of P.T.F.E. houses. The bar heads are insulated by fiber moulded corners. The winding scheme along pneumatic tests at various stages to ensure water tightness and to detect blocking of the flows paths.
      3.      TERMINALS BUSHINGS: - Water cooled terminal bushings are housed in the lower part of the stator on the slip ring side. Porcelain insulators are provided to insulate the terminal bars from the stator body. Effective sealing is provided between the terminal bushing are housed inside a chamber made of non magnetic steel plates. Three phase terminals are brought out to facilitate external connections. The terminal bushings can be replaced without removing the stator from foundation. Provision is made for fixing the external bus ducts with the terminal plate.
      4.      ROTOR: - The rotor is of cylindrical type shaft and body being forged in one piece from chromium, nickel, molybdenum & vanadium steel. Prior to matching, a series of comprehensive ultrasonic examination and other tests are carried out on rotor body and shaft portion to ensure of any internal defects. The rotor with all the details assembled, dynamically balanced to a high degree of accuracy and subjected to 20% over speeding for 2 minutes ensuring mechanical strength.
     5.     FIELD WINDING: - The field winding is made from hard drawn silver bearing copper. Rotor winding is held in position against centrifugal forces by duralium forces wedges in the slot portion & by non magnetic steel retaining rings in the over hang portion. Gap pick up system is employed for direct hydrogen cooling of rotor winding. Several groups of ventilation ducts are mulled on the sides of the rotor coil for gas passage. The rotor slot wedges are of special profiles with elliptical holes rolled in to match the ventilation ducts on the windings stacks. The end windings are insulated from rings with the help of glass epoxy molded segments. Copper segmental type damper winding is provided in the end zone of rotor morrows to prevent over heating of returning rings during asymmetrical & asynchronous operation. 
     6.      SHAFT MOUNTED FANS: - For circulating the cooling gas inside the generator, two propeller type fans are shaft mounted on this & of rotor body fan hubs are made from alloy forging and are hot fitted on the Rotor shaft with sufficient interference. The steel cast fan blades are machined in the tail portion to suit the fan hub and held in position with the help of conical pins. The blades can be easily removed from or assembled in the fan hub. Fan shields fixed to the end shields. Guide the flow of Gas through the fan sections.
      7.      SLIP RINGS: - The slip ring consists of helically grooved Allow steel rings shrunk on the rotor shaft & insulated from it. For convenience in assembly both the rings are mounted on a single common steel bush, which has an insulated jacket pre moulded on it. The complete bush with slip ring is shrunk on the rotor shafts. The slip rings are provided with inclined holes for self- ventilation. The slip rings improve brush performance. 
    
     REFERENCES:-     
  • www.wikipedia.org/wiki/Panipat_Thermal_Power_Station_I
  •   www.hpgcl.gov.in





18 comments:

  1. Very nice post. I just stumbled upon your weblog and wanted to mention that I have truly enjoyed surfing around your blog posts. After all I’ll be subscribing on your rss feed and I’m hoping you write once more very soon!Steam Flow Meter: GFM200.

    ReplyDelete
  2. This blog is too good with lot of information..Thank you

    ReplyDelete
  3. Very nice blog, It's useful to everyone and informative blog, i really like and shared for your blog. Thank You.

    ReplyDelete
  4. This comment has been removed by the author.

    ReplyDelete
  5. Great blog....just i stopped my surfing here....Exact that information which i was in most need.....Thank You so much sir.

    ReplyDelete
  6. I Gone through your Website its really amazing. you having very good content.
    very good information on Electric product i got know useful information thanks for this.

    Semi-Automatic Coil Winding Machine

    Transformer Winding Machine

    ReplyDelete
  7. You really delivered reliable information. Thank you regarding discussing information.Solar Panels for sale

    ReplyDelete
  8. It is very much appreciated for that blog specially very useful for me, thanks
    Anyone can provide me automation work in power plant, like all the motors running with drives or DOL, drives company make, PLC etc.

    ReplyDelete
  9. This comment has been removed by the author.

    ReplyDelete
  10. Santek Equipments Pvt. Ltd. is recognized amongst the prominent manufacturer & supplier of a wide range of material handling Equipments such as cranes & conveyors.

    Santek Equipments Pvt. Ltd. is Pune (India) based company having fully equipped factory with skilled workforce to design, fabricate, supply & commissioning of various type of material handling equipments & systems.

    We are committed towards quality & leave no stone unturned to meet the international quality standards in our range.
    http://www.santek.co.in/

    ReplyDelete
  11. The Air Compressors can be acquired in various models from us. We provide Air Compressors at market-leading price to the buyers. For more details about air compressor price.

    ReplyDelete
  12. Very good piece of information. very good for someone entering power plant operations

    ReplyDelete
  13. This comment has been removed by the author.

    ReplyDelete
  14. i was looking for blogs related of Types of Mechanical Components and their uses , then i found this blog, this is different as per my searching but really interesting to read about thermal power plant.

    ReplyDelete
  15. very good post, and very useful for peoples workings in lower MW. and keep posting

    ReplyDelete
  16. Thanks a lot for sharing informative post with us. keep posting like this blog.
    graphic designer in pune

    ReplyDelete