Report for Vocational Training at

NTPC Limited, Sipat Super Thermal Power Project,

(CHHATTISGARH)

on

POWER PLANT FAMILIARIZATION

Submitted by-

Mechanical Engineering Govt. Engineering College, Bilaspur

DECLARATION

I hereby declare that this project is being submitted in fulfillment of the Vocational Training Programme in NTPC Limited, Sipat, and is the result of self-gained knowledge under the guidance of various Engineers and other officers.

I further declare that to the best of my knowledge,

The structure and contentsof this project are original

Andthe information anddata given in the report is

authentic.

SUBMITTED BY-

Mechanical Engineering Govt. Engineering College, Bilaspur

ACKNOWLEDGEMENT

I am truly thankful to all the Faculties who imparted the lectures on various subjects/topics along with detailed explanation about the plant and machinery.

I would also thank Sh. Pravin Patel (Manager-Training) and other Employees of EDC, Sipat for giving me the chance of having this wonderful learning experience.

I would also like to thank the training and placement officer and all the teachers of my College, for providing me a chance especially Mr. A.K. Garg for the support and guidance at each and every step which helped me secure this vocational training.

All the officials at NTPC went out of their way to provide me with as much information as they could, inspire of the fact that they were laden with their own work. I cant really express my feeling of gratitude towards them.

A lot of information has also been retrieved from the internet due to lack of proper plant visiting facilities.

INDEX

S.NO. TOPIC1. About NTPC

2. Overview of NTPC Sipat STPP

3. Basic Power Plant cycle

4. Coal to Electricity

5. Supercritical Technology

6. Boiler

7. Turbine

8. Electrical Equipments in Power Plant

9. Switchyard

10. Electronic Instruments in PP

11. Conclusion

PAGE

NO.

ABOUT NTPC:

NTPC Sipat Super Thermal Power Project is a cynosure of power generation in India. It is a priceless gem of mineral rich state of Chhattisgarh. Being in the vicinity of Bilaspur , the second largest city of Chhattisgarh and at the vertex of transport arteries adds to its majestic aura.

Total installed capacity of the Sipat Super Thermal Power Project is 2980 MW (Stage 1-660 X 3 & Stage II-500 X 2 MW).The present generation capacity of the project is 2320MW(Stage 1-660X2 &Stage II-500 X2). Plant's water requirement is catered by Hasdeo right bank canal. It gets coal supply from Dipika mines of SECL,Korba. The coal is transport via MGR system of total length 42 km.

Sipat Super Thermal Power Project has many accolades to its credits. Being a pioneer of Super Critical Technology in India and transmission system of 765 kV for the first time in India are the most unique attributes.

Addressing this most pressing need of the hour, i.e. our environment, Sipat Project has 100 meter wide peripheral green belt, submerged ash dykes and state-of-the art technology for environment management.

Indias largest power company, NTPC was set up in 1975 to accelerate power development in India. NTPC is emerging as a diversified power major with presence in the entire value chain of the power generation business. Apart from power generation, which is the mainstay of the company, NTPC has already ventured into consultancy, power trading, ash utilization and coal mining. NTPC ranked 337th in the 2012, Forbes Global 2000 ranking of the Worlds biggest companies. NTPC became a Maharatna company in May, 2010, one of the only four companies to be awarded this status.

The total installed capacity of the company is 41,184 MW (including JVs) with 16 coal based and 7 gas based stations, located across the country. In addition under JVs, 7 stations are coal based & another station uses naptha/LNG as fuel and 2 renewable energy projects. The company has set a target to have an installed power generating capacity of 1,28,000 MW by the year 2032. The capacity will have a diversified fuel mix comprising 56% coal, 16% Gas, 11% Nuclear and 17% Renewable Energy Sources(RES) including hydro. By 2032, non-fossil fuel based generation capacity shall make up nearly 28% of NTPCs portfolio.NTPC has been operating its plants at high efficiency levels. Although the company has 17.75% of the total national capacity, it contributes 27.40% of total power generation due to its focus on high efficiency.

In October 2004, NTPC launched its Initial Public Offering (IPO) consisting of 5.25% as fresh issue and 5.25% as offer for sale by Government of India. NTPC thus became a listed company in November 2004 with the Government holding 89.5% of the equity share capital. In February 2010, the Shareholding of Government of India was reduced from 89.5% to 84.5% through Further Public Offer. The rest is held by Institutional Investors and the Public.

At NTPC, People before Plant Load Factor is the mantra that guides all HR related policies. NTPC has been awarded No.1, Best Workplace in India among large organizations and the best PSU for the year 2010, by the Great Places to Work Institute, India Chapter in collaboration with The Economic Times.

The concept of Corporate Social Responsibility is deeply ingrained in NTPC's culture. Through its expansive CSR initiatives, NTPC strives to develop mutual trust with the communities that surround its power stations.

NTPC- COAL BASED THERMAL POWER PLANTSSr.No.ProjectStateUttarPradeshInst.Capacity(inMW)2,000Chhattisgarh AndhraPradesh WestBengal2,600 2,600 2,100MadhyaPradesh UttarPradesh4,260 2,500Bihar2,340UttarPradesh Orissa UttarPradesh1,820 3,000 1,050Orissa460AndhraPradesh2000UttarPradesh Delhi440 705Chhattisgarh Assam2980750(3x250MW)1.Singrauli SuperThermal Power Station2.NTPCKorba3.NTPCRamagundam4.FarakkaSuperThermal Power Station5.NTPCVindhyachal6.RihandThermal Power Station7.KahalgaonSuperThermal Power Station8.NTPCDadri9.NTPCTalcherKaniha10.FerozeGandhi Unchahar Thermal Power Plant11.TalcherThermal Power Station12.Simhadri SuperThermal Power Plant13.TandaThermal Power Plant 14.Badarpur Thermal PowerStation15.SipatThermal PowerPlant 16.NTPCBongaigaon(commissioning2013 onwards)17.NTPCMoudaMaharashtra18.RihandThermal Power Station (erection phase)Uttar Pradesh2320(2x500 MW;2x660MW) 1*500MWEvolution

NTPCwasset up in 1975 with 100%ownershipbytheGovernmentof India.Inthe last30 years,NTPChasgrown intothe largestpowerutilityin India.

2010200920082005200419971975The company rechristenedasNTPCLimitedin line with itschanging businessportfolioand transformitselffroma thermalpowerutility toan integratedpower utility.NationalThermalPowerCorporationisthe largestpowergenerationcompanyinIndia.Forbes Global2000 for2009 rankedit317thin the worldGovernmentof India grantedNTPCstatusofNavratna beingone of the ninejewelsof India,enhancingthe powerstotheBoardofDirectors.NTPCbecamealistedcompanywith majorityGovernmentownershipof 89.5%. NTPCbecomesthirdlargestbyMarketCapitalisationof listedcompanies.NationalThermalPowerCorporationisthe largestpowergenerationcompanyinIndia.Forbes Global2000 for2008 rankedit411thin the worldBecameaMaharatnCompany

BASIC POWER PLANT CYCLE

RANKINE CYCLE

The Rankin cycle is a cycle that converts heat into work. The heat is supplied externally to a closed loop, which usually uses water. This cycle generates about 80% of all electric power used throughout the world, including virtually all solar thermal, biomass, and coal and nuclear

Power plants. It is named after William John Macquorn Rankin,a

ScottishPolymath. The

Rankincycle is the fundamental thermodynamic underpinningof

The steam engine.

Overview of NTPC Sipat

Super Thermal Power Project:-

A thermal power station consists of all the equipments and a subsystem required to produce electricity by using a steam generating boiler fired with fossil fuels or bio fuels to drive an electric generator. Some prefer to use the term ENERGYCENTRE because such facilities convert form of energy like nuclear energy, gravitational potential energy or heat energy (derived from the combustion of fuel) into electrical energy.

The description of some of the components of the thermal power plant is as follows:

1. Cooling Tower:It is evaporative coller for cooling water. Cooling tower uses the concept of evaporation of water to reject heat from processes such by cooling the circulating water used in oil refineries, chemical plants, power plants, etc. Smaller towers are normally factory built while larger ones are constructed on site. The primary use of large, industrial cooling tower system is to remove the heat by circulating the hot water used by the plants

The absorbed heat is rejected to the atmosphere by the evaporation of some of the cooling water in mechanical forced - draft or induced draft towers or in natural draft hyperbolic shaped cooling towers as seen at most nuclear power plants.

4 Nos Induced draft cooling towers with 10 fans each tower is installed at NTPCsipat for the above said purpose.

2. Three phase transmission line& step-up transformer:

Three phase electric power is a common method of electric power transmission. Its a type of polyphase system mainly used for power motors and many other devices. In a three phase system, three circuits reach their instantaneous peak values at different times. Taking one conductor as reference, the other two conductors are delayed in time by one-third and two-third of cycle of the electrical current. This delay between phases has the effect of giving constant power over each cycle of the current and also makes it impossible to produce a rotating magnetic field in an electric motor. At the power station, an electric generator converts mechanical power into a set of electric currents one from each electromagnetic coil or winding of the generator. The currents are sinusoidal functions of time, all at the same frequency but offset in time to give different phases. In a three phase system, the phases are spaced equally giving a phase separation of one-third of one cycle. Generators output at a voltage that ranges from hundreds fools to 30,000 volts at the power station. Transformers step-up this voltage for suitable transmission after numerous further conversions in the transmission and distribution network the power is finally transformed to standard mains voltage i.e. the household voltage. This voltage

transmitted may be in three phase or in one phase only when we have the corresponding step down at the receiving stage. The output of the transformer is usually star connected with the standard mains voltage being the phase neutral voltage.

3. Electrical Generator:

An electrical generator is a device that coverts mechanical energy to electrical energy, using electromagnetic induction whereas electrical energy is converted to mechanical energy with the help of electric motor. The source of mechanical energy may be a rotating shaft of steam turbine engine. Turbines are made in variety of sizes ranging from small 1 hp(0.75 kW) used as mechanical drives for pumps, compressors and other shaft driven equipment to 2,000,000 hp(1,500,000 kW) turbines used to generate electricity.

4. Steam turbine :

A steam turbine is a mechanical device that extractsthermal energy from

pressurized steam, andConvertsit into rotarymotion. Itsmodern

manifestationwas invented by Sir Charles Parsons in 1884.

It has almostcompletelyReplacedthe reciprocatingpiston steamengine

primarily because of its greater thermal efficiency and higher power-to-weight ratio. Because the turbine generates rotary motion, it is particularly suited to be used to drive an

electrical generator - about 80% of all electricity generation in the world is by use of steam turbines. The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency through the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible process.

5. Steam condenser :The condenser condenses the steam from the exhaust of the turbine into liquid to allow it to be pumped. If the condenser can be made cooler, the pressure of the exhaust steam is reduced and efficiency of the cycle increases. The surface condenser is a shell and tube heat exchanger in which cooling water is circulated through the tubes. The exhaust steam from the low pressure turbine enters the shell where it is cooled and converted to

condensate (water) by flowing over the tubes as shown in the adjacent diagram. Such condensers use steam ejectors or rotary motor-driven exhausters for continuous removal of air and gases from the steam side to maintain vacuum

6. Boiler Feed Pump :

A Boiler Feed Pump is a specific type of pump used to pump water into steam boiler. The water may be freshly supplied or retuning condensation of steam produced by the boiler. These pumps are normally high pressure units that use suction from a condensate return system and can be of centrifugal pump

type or positive displacement type. Constructionand Operation feed water

pumps range from sizes up to many horsepowerand the electric motor is

usually separated from the pump body by some form of mechanical coupling. Large industrial condensate pumps may also serve as the feed water pump. In either case, to force water into the boiler, the pump must generate sufficient pressure to overcome the steam pressure developed by the boiler. This is usually accomplished through the use of centrifugal pump. Feed water pumps usually run intermittently and are controlled by a float switch or other similar level-sensing device energizing the pump when it detects a lowered liquid level in the boiler substantially increased. Some pumps contain a two stage switch. As liquid lowers to the trigger point of the first stage, the pump is activated.

If the liquid continues to drop (perhaps because the pump has failed, its supply has been cut-off or exhausted, or its discharge is blocked),the second stage will be triggered. This stage may switch off the boiler equipment (preventing the boiler from running dry and overheating), trigger an alarm or both.

7. Control valves :

Control Valves are the valves used within industrial plants and elsewhere to control operating conditions such as temperature, pressure, flow and liquid level by fully or partially opening or closing in response to signals received from controllers that compare a "set point" to a "process variable" whose value is provided by sensors that monitor changes in such conditions. The opening or closing of control valves is done by means of electrical, hydraulic or pneumatic systems.

8. De-aerator :

A De-aerator is a boiler feed device for air removal and used to remove dissolved gases from water to make it non -corrosive. A de-aerator typically includes a vertical domed de-aeration section as the de-aeration feed water tank. A steam generating boiler requires that the circulating steam, condensate and feed water should be devoid of dissolved gases, particularly corrosive ones and dissolved or suspended solids. The gases will give rise to corrosion of the metal (due to cavitations). The solids will deposit on heating surfaces giving rise to localized heating and tube ruptures due to overheating. De-aerator level and pressure must be controlled by adjusting control

valves-the level by regulating condensate flow and pressure by regulating steam flow.

Most de-aerators guarantee that if operated properly, oxygen in de-aerated water will not exceed 7ppb by weight.

9. Feed Water Heater :

A feed water heater is a power plant component used to pre heat water delivered to a steam generating boiler. Feed water heater improves the efficiency of the system. This reduces plant operating costs and also helps to avoid thermal shock to boiler metal when the feed water is introduced back into the steam cycle. Feed water heaters allow the feed water to be brought up to the saturation temperature very gradually.

10. Pulveriser-

A pulveriser is a device for grinding coal for combustion in a furnace.

11. Boiler Steam Drum-

Steam Drums are a regular feature of water tube boilers. It is reservoir of water/steam at the top end of the water tubes in the water-tube boiler. They store the steam generated in the water tubes and act as a phase separator for the steam/water mixture. The difference in densities between hot and cold water helps in the accumulation of the "hotter-water/and saturated - steam into steam drum. Made from high-grade steel (probably stainless) and its working involves temperatures 411'C and pressure well above 350psi (2.4MPa). The separated steam is drawn out from the top section of the drum. Saturated steam is drawn off the top of the drum. The steam will re-enter the furnace in through a super heater, while the saturated water at the bottom of steam drum flows down to the mud- drum /feed water drum by down comer tubes

accessories include a safety valve, water level indicator and fuse plug. A steam drum is used in company of a mud-drum/feed water drum which is located at a lower level. So that it acts as a sump for the sludge or sediments which have a higher tendency at the bottom.

12. Super Heater :

A Super heater is a device in a steam engine that heats the steam generated by the boiler again increasing its thermal energy and decreasing the likelihood that it will condense inside the engine. Super heaters increase the efficiency of the steam engine, and were widely adopted. Steam which has been superheated is logically known as superheated steam; non-superheated steam is called saturated steam or wet steam; Super heaters were applied to steam locomotives in quantity from the early 20th century, to most steam vehicles, and so stationary steam engines including power stations.

13. Economisers:Economiser is a mechanical device intended to reduce energy consumption, or to perform another useful function like preheating the fluid. The term economizer is used for other purposes as well, e.g. air conditioning. Boiler heating in power plants. In

boilers, economizer are heat exchange devices that heat fluids, usually water, up to but not normally beyond the boiling point of the fluid. Economizers are so named because they can make use of the enthalpy and improving the boiler's efficiency. They are a device fitted to a boiler which saves energy by using the exhaust gases from the boiler to preheat the cold water used for feed into the boiler (the feed water). Modern day

boilers, such as those in coal fired power stations, are still fitted with economizer which is decedents of Green's original design. In this context they are turbines before it is pumped to the boilers. A common application of economizer is steam power plants is to capture the waste hit from boiler stack gases (flue gas) and transfer thus it to the boiler feed water thus lowering the needed energy input, in turn reducing the firing rates to accomplish the rated boiler output. Economizer lowers stack temperatures which may cause condensation of combustion gases (which are acidic in nature) and may cause serious equipment corrosion damage if care is not taken in their design and material selection.

14. Air Preheater :

Air preheater is a general term to describe any device designed to heat air before another process (for example, combustion in a boiler). The purpose of the air preheater is to recover the heat from the boiler flue gas which increases the thermal efficiency of the boiler by reducing the useful heat lost by the flue gases. As a consequence, the flue gases are also sent to the flue gas stack (or chimney) at a lower temperature allowing simplified design of the ducting and the flue gas stack. It also allows control over the temperature of gas leaving the stack (chimney).

15. Electrostatic Precipitator:An Electrostatic Precipitator (ESP) or electrostatic air cleaner is a particulate device that removes particles from a flowing gas (such as air) using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices, and can easily remove fine particulate matter such as dust and smoke from the air steam. ESP's continue to be excellent devices for control of many industrial particulate emissions, including smoke from electricity-generating utilities (coal and oil fired), salt cake collection from black liquor boilers in pump mills, and catalyst collection from fluidized bed catalytic crackers from several hundred thousand ACFMin the largest coal-fired boiler application. The original parallel plate-Weighted wire design (described above) has evolved as more efficient (and robust) discharge electrode designs were developed, today focusing on rigid discharge electrodes to which many sharpened spikes are attached, maximizing corona production. Transformer -rectifier systems apply voltages of 50-100 Kilovolts at relatively high current densities. Modem controls minimize sparking and prevent arcing, avoiding damage to the components. Automatic rapping systems and hopper evacuation systems remove the collected particulate matter while on line allowing ESP's to stay in operation for years at a time.

16. Fuel gas stack :

A Fuel gas stack is a type of chimney, a vertical pipe, channel or similar structure through which combustion product gases called fuel gases are exhausted to the outside air. Fuel gases are produced when coal, oil, natural gas, wood or any other large combustion device. Fuel gas is usually composed of carbon dioxide (C02) and water vapor as well as nitrogen and excess oxygen remaining from the intake combustion air. It also contains a small percentage of pollutants such as particulates matter, carbon mono oxide, nitrogen oxides and sulfur oxides. The flue gas stacks are often quite tall, up to 400 meters (1300 feet) or more, so as to disperse the exhaust pollutants over a greater aria and thereby reduce the concentration of the pollutants to the levels

required by governmental environmental policies and regulations.

Coal to Electricity

Coal is first milled to a fine powder, which increases the surface area and allows it to burn more quickly. In these pulverised coal combustion (PCC) systems, the powdered coal is blown into the combustion chamber of a boiler where it is burnt at high temperature (see diagram below). The hot gases and heat energy produced converts water in tubes lining the boiler into steam.

The high pressure steam is passed into a turbine containing thousands of propeller-like blades. The steam pushes these blades causing the turbine shaft to rotate at high speed. A generator is mounted at one end of the turbine shaft and consists of carefully wound wire coils. Electricity is generated when these are rapidly rotated in a strong magnetic field. After passing through the turbine, the steam is condensed and returned to the boiler to be heated once again.

The electricity generated is transformed into the higher voltages (up to 400,000 volts) used for economic, efficient transmission via power line grids. When it nears the point of consumption, such as our homes, the electricity is transformed down to the safer 100-250 voltage systems used in the domestic market.

Supercritical Technology

Supercritical power plants were in service from the late fifties. But the technology did not really take off due to problems of reliability especially from the metallurgical aspect.

The single most important factor that determines the use of higher and higher pressure and temperatures are the availability of materials to withstand these conditions. Increases in operating pressure and temperatures have to go hand in hand with developments in metallurgy.

With more than 600 units in service the reliability issue seems to be resolved. Supercritical units are the standard for future power plants in many countries including China.

What are the key differences between the subcritical units and the Supercritical units?

Efficiency

The main advantage and the reason for a higher pressure operation is the increase in the thermodynamic efficiency of the Rankin cycle.

Large Subcritical thermal power plants with 170 bar and 540 / 540 C (SH / RH) operate at an efficiency of 38 %. Supercritical units operating at 250 bar and 600/615 C can have efficiencies in the range of 42 %.

Ultra supercritical units at 300 bar and 615 / 630 C will still increase the efficiency up to 44 %.

Increase in efficiency directly lead to reductions in unit cost of power and CO2 emissions.

Operational Flexibility

Most of the Supercritical units use the once through technology. This is ideal for sliding pressure operation which has much more flexibility in load changes and controlling the power grid.

However this also requires more sensitive and quick responding control systems.

Evaporation End Point

In subcritical units the drum acts as a fixed evaporation end point. The furnace water walls act as the evaporator. Not so in the case of a supercritical unit. The evaporation end point can occur in various levels ofthe furnace depending on the boiler load. The percentage of Superheat in supercritical units is higher than subcritical units. Because of this the furnace tubes act more as super heaters than water walls. This necessitates the use of higher grade of materials like alloy steels in the furnace.

Heat transfer Area

Higher steam temperatures in supercritical units results in a lesser differential temperature for heat transfer. Because of this heat transfer areas required are higher than subcritical units.

Higher Superheat steam temperatures entering the HP turbine also mean higher reheater inlet temperatures which again results in a higher heat transfer areas.

Water chemistry

In supercritical units the water entering the boiler has to be of extremely high levels of purity. Supercritical boilers do not have a steam drum that separates the steam and the water. If the entering water quality is not good, carryover of impurities can result in turbine blade deposits.

Materials

Supercritical power plants use special high grade materials for the boiler tubes. The turbine blades are also of improved design and materials. In fact, the very increase in higher pressure and temperature designs are dependendent on the development of newer and newer alloys and tube materials.The aim of the industry is to achieve power plant efficiencies in the range of 50 %.

Boiler

A boiler is the central or an important component of the thermal power plant which focuses on producing superheated steams that is used for running of the turbines which in turn is used for the generation of electricity. A boiler is a closed vessel in which the heat produced by the

combustion of fuel is transferred to water for its conversation into

steam of the desired temperature & pressure.

The heat-generatingUnit includes a furnace

burned.With the advantage of water-cooled

heaters,air heatersand economizers, the term

evolved as a better description of the apparatus.

in which the fuel is furnace walls, super steam generator was

Boilers may be classified on the basis of any of the following characteristics

Use

Pressure

Materials

Size

Tube Content

Tube Shape and position

Firing

Heat Source

Fuel

Fluid

Circulations

Furnace position

Furnace type

General shape

Trade name

Special features.

Use: The characteristics of the boiler vary according to the nature ofservice performed. Customarily boiler is called either stationary or mobile. Large units used primarily for

electric power generation are known as control station steam generator or utility plants.

Pressure: To provide safety control over construction features, allboilers must be constructed in accordance with the Boiler codes, which differentiates boiler as per their characteristics.

Materials: Selection of construction materials is controlled by boiler code material specifications. Power boilers are usually constructed of special steels.

Size: Rating code for boiler standardize the size and ratings of boilers based on heating surfaces. The same is verified by performance tests. Tube Contents: In addition to ordinary shell type of boiler, there are two general steel boiler classifications, the fire tube and water tube boilers. Fire tube boiler is boilers with straight tubes that are surrounded by water and through which the products of combustion pass. Water tube boilers are those, in which the tubes themselves contain steam or water, the heat being applied to the outside surface.

Firing: The boiler may be a fired or unfired pressure vessel In fired boilers, the heat applied is a product of fuel combustion. A non-fired boiler has a heat source other than combustion.

Heat Source: The heat may be derived from (1) the combustion of

fuel (2) the hot gasses of other chemical reactions (3) the utilization of

nuclear energy.

Fuel: Boilers are often designated with respect to the fuel burned.

Fluid: The general concept of a boiler is that of a vessel to generate steam. A few utilities plants have installed mercury boilers.

Circulation: The majority of boilers operate with natural circulation. Some utilize positive circulation in which the operative fluid may be forced 'once through' or controlled with partial circulation.

Furnace Position: The boiler is an external combustion device in which the combustion takes place outside the region of boiling water. The relative location of the furnace to the boiler is indicated by the description of the furnace as being internally or externally fired.

The furnace is internally fired if the furnace region is completely surrounded by water cooled surfaces. The furnace is externally fired if the furnace is auxiliary to the boiler.

Furnace type: The boiler may be described in terms of the furnace type.

General Shape: During the evaluation of the boiler as a heat producer, many new shapes and designs have appeared and these arewidely recognized in the trade.

Trade Name: Many manufacturers coin their own name for each boiler and these names come into common usage as being descriptive of the boiler.

Special features: sometimes the type of boiler like differential firing and Tangential firing are described.

Categorization of Boilers:

Boilers are generally categorized as follows:

Steel boilers

Fire Tube type

Water tube type

Horizontal Straight tube

The boiler is generally used for power production are two types:-

1. Corner boiler2. Front fire boiler

The boiler mainly has natural circulation of gases, steam and other things. They contain vertical membrane water. The pulverized fuel which is being used in the furnace is fixed tangentially. They consume approximately 700 ton of coal of about 1370kg\cm2 of pressure having temperature of540oC.

The first pass of the boiler has a combustion chamber enclosed with water walls of fusion welded construction on all four sides. In addition there are four water platens to increase the radiant heating surface. Beside this super heater reheated sections are also suspended in the furnace combustion chamber. The first pass is a highheat zone since the fuel is burned in this pass.The second pass is surrounded by steam cooled walls on all four sides as well as roof of the boiler. A horizontal super heater, an economizer & two air heaters are located in the second pass.

The main components of a boiler and their functions are given below:

a) DRUM: It is a type of storage tank much higher placed than thelevel at which the boiler is placed, and it is also a place where water and steam are separated. First the drum is filled with water coming from the economizer, from where it is brought down with the help of down-comers, entering the bottom ring headers. From there they enter the riser, which are nothing but tubes that carries the water (which now is a liquid-vapor mixture), back to the drum. Now, the steam is sent to the super heaters while the saturated liquid water is again circulated through the down-comers and then subsequently through the risers till all the water in the drum turns into steam and passes to the next stage of heating that is superheating.

NOTE: for a 660 MW plant, the boiler does not employ any drum; instead the water and steam go directly into the super heater because the pressure employed being higher than the critical pressure of water on further stages of heating will eventually turn completely into steam without absorbing any latent heat of vaporization since the boiling part in the T-s curve no longer passes through the saturation dome rather its goes above the dome.

b) SUPER HEATERS: The steam from theboiler drum is

then sentfor superheating. This takes place in threestages. In the first

stage, thesteam is sent to a simple super heater, known as the low

temperature super heaters (LTSH), after which the second stage consists of several divisional panels super heaters (DPSH). The final stage involves further heating in the Platen super heaters (PLSH), after which the steam is sent through the Main Steam (MS) piping for driving the turbine.

Superheating is done to increase the dryness fraction of the exiting steam. This is because if the dryness fraction is low, as is the case with saturated steam, the presence of moisture can cause corrosion of the blades of the turbine. Super-heated steam also has several merits such as increased working capacity, ability to increase the plant efficiency, lesser erosion and so on. It is also of interest to know that while the super heater increases the temperature of the steam, it does not change the pressure. There are different stages of super heaters besides the sidewalls and extended sidewalls. The first stage consists of LTSH (low temperature super heater), which is conventional mixed type with

upper & lower banks above the economizer assemblyin rear pass.

The other is DivisionalPanel Super heaterwhich is hangingabove in the

first pass of the boilerabove the furnace.The third stage is the Platen

Super heater from where the steam goes into the HP turbine through the main steam line. The outlet temperature & pressure of the steam coming out from the super heater is 540 degrees Celsius & 157 kg/ern'. After the HP turbine part is crossed the steam is taken out through an outlet as CRH(Cold Re-heat steam) to be re-heated again as HRH(Hot Re-heat steam) and then is fed to the IPT(Intermediate pressure turbine) which goes directly to the LPT(Low pressure turbine) through the IP-LP cross-over.

c) WATER WALLS: The water from the bottom ring header is thentransferred to the water walls, where the first step in the formation of steam occurs by absorbing heat from the hot interior of the boiler where the coal is burned continuously. This saturated water steam mixture then enters the boiler drum.

In a 500 MW unit, the water walls are of vertical type, and have rifled tubing whereas in a 660 MW unit, the water walls are of spiral type till an intermediate ring header from where it again goes up as vertical type water walls. The advantage of the spiral wall tubes ensures an even distribution of heat, and avoids higher thermal stresses in the water walls by reducing the fluid temperature differences in the adjacent tubes and thus minimizes the sagging produced in the tubes.

Figure depictingthe differencebetween theverticalwater wall and

the spiral waterwall type of tubing where the vertical water waslies

have the rifle type of tubes toincrease thesurfacearea unlike the

spiral ones that have plain, smooth surfaces.

d) ECONOMIZER: The economizer is a tube-shaped structurewhich contains water from the boiler feed pump. This water is heated up by the hot flue gases which pass through the economizer layout, which then enters the drum. The economizer is usually placed below the second pass of the boiler, below the Low Temperature Super heater. As the flue gases are being constantly produced due to the combustion of coal, the water in the economizer is being continuously being heated up, resulting in the formation of steam to a partial extent. Economizer tubes are supported in such a way that sagging, deflection & expansion will not occur at any condition of operation.

e) DEAERATOR:

A deaeratoris a device thatiswidely usedfor the removalofair

and other dissolved gasesfromthe feedwatertosteam-generating

boilers.Inparticular, dissolved oxygen in boiler feedwaterswill cause

serious corrosion damage in steam systems by attachingto the walls of

metal piping and other metallic equipmentand formingoxides(rust).

Wateralso combines withany dissolvedcarbondioxideto form

carbonicacid that causesfurther corrosion.Mostde aeratorsare

designedto remove oxygen down to levels of 7ppb by weight (0.005

cmvl.)or less.

There are two basic types of deaerators, the tray-type and the spray-type:

The tray-type (also calledthe cascade-type) includesa vertical

domed de aeration sectionmounted on top of a horizontalcylindrical

vessel which serves as the deaerated boiler feedwater storage tank.

The spray-type consists only of a horizontal (or vertical) cylindrical vessel which serves as both the de aeration section and the boiler feedwater storage tank.

In addition to these there are several other smaller components attached to a boiler, including several safety valves, which have their own special significance.

So briefly, the boiler functions this way. The water enters the boiler through the economizer. From there it passes to the drum. Once the water enters the drum it comes down the down comers to the lower inlet water wall headers. From the headers the water rises through the water walls and is eventually turned into steam due to the continuous heat being generated by the burners. As the steam is formed it enters the steam drum. Here the steam and water is separated. The separators and dryers remove the droplets of water and the cycle through the water walls is repeated. This cycle is known as natural circulation cycle. In the forced circulation of water pumps are used to maintain the flow of water.

Turbine

the overall figure of the boiler depicting the flow of the fuel and the gases along the given direction of the arrows.

Sole purpose of turbine is to produce work by expanding steam from

very high pressure to low condenser pressure.

We mainly use three types of turbine here viz. 1 HP turbine,1 IP turbine

and 2 LP turbine

We are using different pressure turbines for reheating purposeSo

that we can enhance overall efficiency of the plant (or so thatwecan

overcome problem of wet steam)

First superheated steam is allowed to expand in HPT to someIPand

then send back to boiler for reheating purpose.

Then this reheated steam is sent to IP turbine for expandingwhereafter

it get expanded to some lower pressure a BLEND steam is taken out and sent to FEED WATER HEATER (FWH) for heating feed water for REGENERATION)

RATED CONDITIONS

LOAD:660MW

BEFORE HP STOP VALVE

STEAM PRESSURE:247KSC

STEAMTEMPERATURE:5370C

STEAM FLOW:2023.75T/HR

AFTER HPC

STEAM PRESSURE:48KSC

STEAM PRESSURE:298.710C

BEFORE IP STOP VALVE

STEAM PRESSURE:43.2KSC

STEAM TEMPERATURE:5650C

STEAM FLOW TO REHEATER:1681.12T/HR.

DESIGN CONDENSER PRESSURE:0.105KSC (abs.)

COOLING WATER FLOW:64000M3/HR

FINAL FEED WATER TEMP. :286.350C

FREQUENCY RANGE:47.5 51.5 Hz

Generator rated speed3000rpm

Generator manufacturerElectrosila

No. of bleedings8

Length of the turbine36.362m

No. of stages

HPT17

IPT11x2

LPT-15x2

LPT-25x2

Total59

INTRODUCTION TO STEAM TURBINE

A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion, lts modern manifestation was invented by Sir Charles Parsons in 1884.

Definitions of Steam turbine:

Turbine in which steam strikes blades and makes them tum.

A system of angled and shaped blades arranged on a rotor through which steam is passed to generate rotational energy. Today, normally used in power stations A device for converting energy of high-pressure steam (produced in a boiler) into mechanical power which can then be used to generate electricity. Equipment unit flown through by steam, used to convert the energy of the steam into rotational energy.

Principle of Operation:

In reciprocating steam engine, the pressure of energy of steam is used to overcome external resistance and dynamic action of the steam is negligibly small. Steam engine may be retum by using the full pressure without any expansion or drop of pressure in the cylinder.

The steam energy is converted mechanical work by expansion through the turbine. The expansion takes place through a. series of fixed blades (nozzles) and moving blades each row of fixed blades and moving blades is called a stage. The moving blades rotate on the central turbine rotor and the fixed blades are concentrically arranged within the circular turbine casing which is substantially designed to withstand the steam pressure.

Classification of Steam Turbines

The first steam turbine, at its time indeed did spark off the industrial revolution throughout the west. However, the turbine at that time was still an inefficient piece of heavy weighing high maintenance machine. The power to weight ratio of the first reciprocating steam turbine was extremely low, and this led to a great focus improving the design, efficiency and usability of the basic steam turbine, the result of which are the power horses that currently produce more than 800/0of today's electricity at power plants.

Steam Turbines are Classified as:

Steam Turbines can be classified on the basis of a number of factors. Some of the important methods of steam turbine classification are enunciated below:

On the basis of Stage Design:

Steam turbines use different stages to achieve their ultimate power conversion goal Depending on the stages used by a particular turbine, it is classified as Impulse Turbine, or Reaction type.

On the Basis of the Arrangement of its Main Shaft:

Depending on the shaft arrangement of the steam turbine, they may be classified as Single housing (casing), tandem compound (two or more housings, with shafts that are coupled in line with each other) and Cross compound turbines (the shafts here are not in line).

On the Basis of Supply of Steam and Steam Exhaust Condition:

They may be classified as Condensing, Non Condensing, Controlled or Automatic extraction type, Reheat (the steam is bypassed at an intermediate level, reheated and sent again) and Mixed pressure steam turbines (they have more than one source of steam at different pressures). On the basis of Direction of Steam Flow:

They may be axial, radial or tangential flow steam turbines.

On the Basis of Steam Supply:

Superheated steam turbine or saturated steam turbine.

Basic types of Turbines

The two most basic and fundamental types of steam turbines are the impulse turbine and the impulse reaction turbine.

The Impulse Turbine:

The impulse turbine consists of a set of stationary blades followed by a set of rotor blades which rotate to produce the rotary power. The high pressure steam flows through the fixed blades, which are nothing but nozzles, and undergo a decrease in pressure energy, which is converted to kinetic energy to give the steam high velocity levels. This high velocity steam strikes the moving blades or rotor and causes them to rotate. The fixed blades do not completely convert all the pressure energy of the steam to kinetic energy, hence there is some residual pressure energy associated with the steam on exit. Therefore the efficiency of this turbine is very limited as compared to the next turbine we are going to review-the reaction turbine or impulse reaction turbine.

Working of Impulse Turbine

The impulse turbine was one of the basic steam turbines. It involved striking of the blades by a stream or a jet of high pressure steam, which caused the blades of the turbine to rotate. The direction of the jet was perpendicular to the axis of the blade. It was realized that the impulse turbine was not very efficient and required high pressures, which is also quite difficult to maintain. The impulse turbine has nozzles that are fixed to convert the steam to high pressure steam before letting it strike the blades. Impulse turbine Mechanism deals with the Impulse force action-reaction.

As we all know the Newton 3rd law of motion," Every action has equal and opposite reaction", the same is work on this.

As the water fall on the blade of the rotor it generate the impact force on the blade surface, The blade tends to give the same reaction to the fluid, but the rotor is attached to the rotating assembly, it absorb the force impact and give the reaction In the direction of the fluid now. Thus the whole turbine rotates.

The rotation speed of the turbine depends on the fluid velocity, more the fluid velocity, greater the rotation speed, and greater the speed means more power generation.

The Reaction Turbine

The reaction turbine is a turbine that makes use of both the impulse and the reaction of the steam to produce the rotary effect Oil the rotors. The moving blades or the rotors here are also nozzle shaped (They are aerodynamically designed for this) and hence there is a drop in pressure Willie moving through the rotor as weU. Therefore in this turbine the pressure drops occur not only in the fixed blades, but a.further pressure drop occurs in the rotor stage as well. This is the reason why this turbine is more efficient as the exit pressure of the steam is lesser, and the conversion is more. The velocity drop between the fixed blades and moving blades is almost zero, and the main velocity drop occurs only ill the rotor stage.

WORKING OF REACTION TURBINE:

In the reaction turbine, the rotor blades themselves are arranged to form convergent nozzle Reaction Turbines. In the reaction turbine, the rotor blades themselves are arranged to form convergent

nozzles. This type of turbine makes use of the reaction force produced as the steam accelerates through the nozzles formed by the rotor. Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the stator as a jet that fills the entire circumference of the rotor. The steam then changes direction and increases its speed relative to the speedof the blades. A pressure drop occurs across both the stator and the rotor, with steam accelerating through the stator and decelerating through the rotor, with no net change in steam velocity across the stage but with a decrease in both pressure and temperature, reflecting the work performed in the driving of the rotor. This type of turbine makes use of the reaction force produced as the steam accelerates through the nozzles formed by the rotor. Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the stator as a jet that fills the entire circumference of the rotor. The steam then changes direction and increases its speed relative to the speed of the blades. A pressure drop occurs across both the stator and the rotor, with steam accelerating through the stator and decelerating through the rotor, with no net change in steam velocity across the stage but with a decrease in both pressure and temperature, reflecting the work performed in the driving of the rotor.

LUBRICATION OIL SYSTEM

Introduction: same oil is used for governing & lubrication. The oil is kept in the main oil tank. The governing is designed for operation at the oil pressure of 14kglcmsq while lubrication of bearings is designed to work at 2kglcmsq.The following equipment is available in the lubricating system.

1. Auxiliary oil pump

2. A.C lube oil pt1l11p

3. D.C emergency oil pump

4. main oil pump

5. booster pump

6. oil tank

7. oil coolers

8. vent fans

Lubrication oil system lubricates both turbine and generator bearings. Moreover it supplies oil to seal oil system.

During normal operation of turbine shaft directly drives pump (centrifugal type) at 3000 rpm and supplies oil to the lubrication system. Auxiliary oil pump is incorporated in the oil system to deliver oil to governing system and bearings at the time of starting of turbine with back up protection. D.C. stands by oil pumps are used for bearing oil supply only.

AUXILARY OlL PUMP:

It is centrifugal pump driven by A.C electric motor. Auxiliary oil pump is provided for meeting the requirement of oil for the turbine governing system and bearing lubrication system during and stopping. It is mounted on the main oil tank.

DC LUB OIL PUMP:

The bearing are protected from possible lubrication failure by the provision of two automatically starting oil pumps-i.e. AC lubrication oil pUl11pand DC emergency oil pump AC lube oil pump automatically start when lubrication oil pressure drops to l.2kglcmsq. The emergency

lubrication oil pump (DC driven) is provided as a backup protection against the failure of AC lubrication oil pump or AC supply. DC lubrication oil pull up cuts in automatically when lubrication pressure drops down to 0.8kglcmsq. Both AC lubrication oil pump and DC lubrication oil pump are mounted on main oil tank.

MAIN OIL PUMP:

During normal operation of turbine, main lubrication oil I pUl11pis mounted on turbine shaft and driven by turbine shaft at 3000rpm. It supplies oil to the governing and lube oil system.

Pump is designed for continues operation at 3000rpm and installed inside the front pedestal of turbine. The MOP is capable to supply oil to the system at full capacity when the turbine reaches to 2800rpm. Then the AOP, which is in service, will be separated from the system automatically.

BOOSTER PUMP:

The oil pressure developed by auxiliary oil pump discharge during starting and stopping of turbine operates booster pump. During normal running of turbine (at 3000rpm) it is operated by main oil pump discharge. It supplies oil to lubricating.

OIL TANK:

Oil is stored in main oil tank (MOT) whose capacity is 16cum. Two numbers of vapor fans are mounted on MOT to extract oil vapor and dissolved gases also to the atmosphere from MOT. Auxiliary oil pump, AC lubrication oil pump, DC lubrication booster pump and oil coolers are mounted on MOT.Oil level indicators and instruments such as oil pressure and temperature gauges and pressure switches for pump interlocks and annunciation's are mounted on MOT. Local starting and stopping of plilllpS and local pressure indicators are also available on MOT. The oil cooler changing system and magnetic duplex system selection also mounted on MOT. The line to oil purification system is connected to .MOT.

OIL COOLERS:

Oil coolers are of surface type. Usually one cooler will be in service while

the other is standby. It consists of tubes through which cooling medium flows. The cooling medium used is raw water. The oil cooler consist of the following.

1. shell

2. upper water chamber

3. lower water chamber

4. tube system

5. cooler change over mechanism

Main turbine Lubricating Oil SystemSteam Turbine Flow Diagram

Electrical Equipments in Power Plant

Power plant consists of variety of electrical equipment.

Majorelectrical equipment are Alternator, Exciters,

Synchronizing Equipment,CircuitBreakers, currentand

potentialtransformers,relaysandprotection equipment,

isolator,lighting arresters, earthingequipment,station

transformer, battery and motorfor driving auxiliaries

Generator

In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric current to flow through an external circuit.

Generator are varies in type according to the type power plant. Generator decide the size of power plant.

Exciters

Excitation system is required to provide the necessary fieldcurrent to the rotor winding of a synchronous machine. Availability of excitation at all times important. Larger the load currents, lower the speed and lagging power factor which require more excitation.

Types of excitation system:

1. DC Excitation System

2. AC Excitation System

3. Static Excitation System

Power Transformer

Power transformers are used for stepping-up the voltage for transmission at generating stations and for stepping-down voltage for distribution purpose.

Normally naturally cooled, oil immersed, two winding, three phase transformers are used up to the rating of 10 MVA. For regulating the voltage, transformers are provide with on load tap changers. They are put in operation during large load hours and disconnected during light load hours.

Voltage Regulators

Every alternator provide with automatic voltage regulator which perform following function

1. Control of voltage within prescribed limits.

2. Proper division of reactive power b/w alternator operating in parallel.

3. Prevention of dangerous over-voltage in system.

Types

Using Transformer

Induction Voltage Regulator * Now-a-days Electronic voltage regulators are used for greater sensitivity and accuracy.

Bus-Bars

Bus bar is a main bar or conductor carrying an electric current to which many connections are to be made.

Usually two buses are provided in a system one is called the Main" bus and other Auxiliary" or transfer bus

There are many shapes of bus bar available like round tubes, round solid bars or square tube

Material used for bus bar is aluminum because it has high corrosion resistance than copper and lower cost.

Bus bar of 5 to 6 meter in length.

Reactors

Reactor is a coil having large inductive reactance in comparison touts resistance.

It is used in the circuit to limit the short circuit currents to a safer value in order to protect the electrical installation

As their reactance is very small, the efficiency of the system is not affected.

It avoid the faulty current to flow through the healthy system. Types of reactor

1. Open type

2. Oil Immersed type

Insulators

The porcelain insulators are used to support the bus-bar

It also provide the insulation to the bus-bar from pole to ground

Current rating of porcelain is above 2000A Post type insulator

Switchgear

During the operation of power system the generating plants,

transmission lines, distributors and other electrical equipment are required to be switched on and offunder both normal and abnormal conditions Switchgears aroused.

All the protection equipment like switches, fuse, Circuit breakers, relays are installed in switchgear

Types

1. Outdoor type

2. indoor type

For the voltage above the 66KV outdoor switchgear are installed.

Switches

A switch is a device which is used in making or breaking the electric circuit. By simple motion of a knob or handle.

They can make or break the circuit during normal andabnormal conditions

Types of switches:

1. Air switches

2. Oil switch

Oil switches are used in high voltage and heavy current circuit.

Protective Instruments

Protective equipment are very important in system to isolate the abnormal conditions

Feature of protective equipment

1. greater reliability

2. High speed of operation

3. Simple and withstand to large value of fault

Various Protective equipment are Fuse, Circuit Breakers, Relays,

Lightning arresters.

Fuse

A Fuse is a wire of short length or thin strip of material which melt with the flow of excessive current

Under normal working conditions safe value of current flows but during short circuit load current increased which heat the wire so wire melt and circuit break.

Advantages:-

1. Cheap in cost

2. Needs no maintained

3. It interrupts short-circuit current without noise, flame, gas or smoke

4. Under short circuit condition it limits the current of inverse time characteristic it is easily provided for over load protection.

Disadvantages of fuse:-

1. Wire should be replaced after every operation Rewire able Kit-Kat Fuse.

Circuit Breaker

A circuit breaker is mechanical device used to open and close contact under normal and abnormal conditions

Relay is use as a sensor with circuit breaker for automatic operation.

Circuit breaker carry normal current without overheating

or damage.

Function of circuit breaker:-

1. To carry full load current continuously

2. To open and close the circuit under no load

3. To break the circuit under short-circuit condition

Types of circuit breaker according to voltage level:

1. Low Voltage CB :- V 6300A Miniature Circuit Breaker

Relay

Relay is electro-mechanical device which sense the excessive flow of current and send signal to the circuit breaker.

Relay has three essential elements:

1. Sensing element- it sense and measure the change.

2. Comparing element- compare the measured quantity to pre-settled value.

3. Controlling element- it sends signal to circuitbreaker.

Types of relay:

1.Latching relay

2. Reed relay

3. Mercury relay

4. Polarized relay

5. Solid-state relay

Current Transformer

It is an instrument transformer which is used to measure the current from high voltage line with these of normal ampere meter.

High currents or voltages of electrical power systemcannot be directly fed to relays and meters. (T steps down rated system current to 1Amp or 5

The relays and meters are generally designed for 1 Amp, 5 Amp and 110V.

It is normally a step-down transformer

Secondary winding has a 5 ampere value of current tithe rated current of primary winding.

Potential Transformer

It is also an instrument transformer which is used to measure the voltage above 380 volts Take the ordinary low voltage instrument suitable for measurement if high voltage and isolate from high voltage.

When rated high voltage is applied to primary of PT, it give the secondary voltage of 110 volts.

Batteries

All power plant and sub-stations uses DC supply for protection and control purpose

DC supply is provided from Storage batteries.

Lead acid batteries mostly used in power stations because their higher cell voltage and lower cost.

Control Rooms

Control room is nerve center of the power station

Various controls like Voltage adjustments, load control, emergency tripping of turbine and other equipment and instruments are housed in the control room.

Location of control room is away from noise and should near to the switch house.

There should be no glare, neat and clean, well-ventilated and free from draughts.

SWITCHYARD

It is a switching station which has the following credits :

Main link between generating plant and Transmission system, which has a large influence on the security of the supply.

Step-up and/or Step-down the voltage levels depending upon the Network Node.

Switching ON/OFF Reactive Power Control devices, which has effect on Quality of power.

Salient Features of SIPAT Switchyard

First switchyard in INDIA at 765 Kv level.

First switchyard in NTPC with total substation automation and numerical relays.

First switchyard in INDIA with a highest rating EHV Interconnecting transformer of 1000MVA.

Various voltage levels such as 765Kv, 400Kv and132Kv.

Two 765 kiva lines to SEONI , two 400 kv lines to Raipur, two 400 kv lines to Ranchi. One LILO from LANCO patadi to Raipur.

As we know that electrical energy cant 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.

SINGLE LINE DIAGRAM OF 220KV SWITCH YARD-

OUTDOOR EQUIPMENTSINDOOR EQUIPMENTS

1. BUS BAR

2.LIGHTENING ARRESTER1.RELAYS

3.WAVE TRAP2.CONTROL PANELS

4. BREAKER

5. CAPACITOR VOLTAGE TRANSFORMER

6. CORONA RING

7. EARTHING ROD

8. CURRENT TRANSFORMER

9. POTENTIAL TRANSFORMER

10. LIGHTENING MASK

11. LIGHTENING MOOSE

CIRCUIT BREAKER:

The code for circuit breaker is 52. An electric power system needs some form of switchgear in order to operate it safely & efficiently under both normal and abnormal conditions.

Circuit breaker is an arrangement by which we can break the circuit or flow of current. A circuit breaker in station serves the same purpose as switch but it has many added and complex features. The basic construction of any circuit breaker requires the separation of contact in an insulating fluid that servers two functions:

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

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

The insulating fluids commonly used in circuit breakers are:

1. Compressed air

2. Oil which produces hydrogen for arc excitation.

3. Ultra high vacuum

4. Sulphur hexafluorides

The Specifications of the circuit breaker used are:

MAKE

TYPE

RATED VOLTAGE

CROMPTON GREAVES LTD.

AIR BLAST CIRCUITREAKER

245 KV

RATEDLIGHTING

IMPULSE

WITHSTAND VOLTAGE

RATED SHORT CIRCUIT

BREAKING CURRENT

RATED FREQUENCY

RATEDNORMAL

CURRENT

1050 KV

25 - 40KA

50HZ

2000 A TO 4000 A

RATEDCLOSING220 V DC

VOLTAGE

RATEDOPENING220 V DC

VOLTAGE

LIGHTING ARRESTER:

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

A meter is provided which indicates the surface leakage and internal grading current of arrester.

1. Green arrester is healthy

2. Red arrester is defective.

In case of red we first de-energize the arrester and then do the operation.

AIR BREAK EARTHING SWITCH:

The code of earthling switch is 5, 6, 7.The work of this equipment comes into picture when we want to shut down the supply for maintenance purpose. This help to neutralize the system from induced voltage from extra high voltage. This induced power is up to 2KV in case of 400 KV lines.

The specification of earthling switch is:

MAKE

TYPE

VOLTAGE

CURRENT

MOTOR VOLT (AC)

CONTROL VOLT (DC)

S & S POWER

MADRAS

245 KV

10 KA

415 VOLTS

220 VOLTS

BUS BAR:

Bus bars generally are of high conductive aluminum conforming to IS-5082 or copper of adequate cross section .Bus bar located in air insulated enclosures & segregated from all other components .Bus bar is preferably cover with polyurethane.

1. Current Transformer (CT):

A current transformer is a type of instrument transformer designed to provide a current in its secondary winding proportional to the alternating current flowing in its primary

. Current Transformer DiagramApplication:

1. They are commonly used in metering and protective relaying in the electrical power industry where they facilitate the safe measurement of large currents, often in the presence of high voltages.

2. The current transformer safely isolates measurement and control circuitry from the high voltages typically present on the circuit being measured.

3. Current transformers are used extensively for measuring current and monitoring the operation of the power grid. The CT is typically described by its current ratio from primary to secondary. Often, multiple CTs are installed as a "stack" for various uses (for example, protection devices and revenue metering may use separate CTs). Similarly potential transformers are used for measuring voltage and monitoring the operation of the power grid.

4. Capacitive Voltage Transformer (CVT):

A capacitor voltage transformer (CVT) is a transformer used in power systems to step-down extra high voltage signals and provide low voltagesignals either for measurement or to operate a protective relay. In itsmost basic form the device consists of three parts: two capacitors across which the voltage signal is split, an inductive element used to tune the device to the supply frequency and a transformer used to isolate and further step -down the voltage for the instrumentation or protective relay as shown in figure below.

The device has at least four terminals, a high-voltage terminal for connection to the high voltage signal, a ground terminal and at least one set of secondary terminals for connection to the instrumentation or protective relay. CVTs are typically single -phase devices used for measuring voltages in excess of one hundred kilovolts where the use of voltage transformers would be uneconomical. In practice the first capacitor, C1, is often replaced by a stack of capacitors connected in series. This results in a large voltage drop across the stack of capacitors that replaced the first capacitor and a comparatively small voltage drop across the second capacitor C2, and hence the secondary terminals.

Conclusion

All theminor&majorsectionsinthe thermal

project hadbeen visited & also understoodto thebest

of myknowledge.I believethatthis traininghas

made me wert versed withthe variousprocesses in

the power plant . As far as I thinkthereis a long way

to go till we use our newestofeverimproving

technologiestoincreasetheefficiency becausethe

stocksof coal aredwindling andtheyare not going

to last forever. Itsimperativethatwestart

shoulderingtheburden together to see a shiningand

Sustainable India.