PRESTIGE INSTITUTE OF ENGINEERING AND SCIENCE, INDORE (M.P.)

Session:2010

An Industrial visit Report

on

Narmada Hydroelectric Development Corporation

(NHDC), Omkareshwar

Guided By: - Submitted By :-

Prof. Karuna Nikum Amit Kumar

Prof.S.S. Raghuvanshi Branch : EX

Roll no . 0863EX081003

Batch: 2008-12

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PRESTIGE INSTITUTE OF ENGINEERING AND SCIENCE ,INDORE (M.P.)

2010

Recommendation

The Industrial report entitled “Hydro Electric Power Plant NHDC, Omkareshwar” submitted by AMIT KUMAR towards the partial fulfillment of degree of Bachelor of Engineering (Electrical & Electronics), of Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal is satisfactory account of the progress made by his/her in dissertation work.

Guided By: - Prof. & Head

Prof. Karuna Nikum Ms. Karuna Nikum

Prof. S.S. Raghuvanshi (Asst. Prof.)

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PRESTIGE INSTITUTE OF ENGINEERING AND SCIENCE ,INDORE (M.P.)

2010

Certificate

It is certified that an industrial visit report entitled “Industrial Visit at NHDC, Omkareshwar” submitted by AMIT KUMAR towards the partial fulfillment of degree of Bachelor of Engineering (Electrical & Electronics), Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal is satisfactory account of the progress made by his/her in work.

Prof. & Head

Ms. Karuna Nikum

(Asst. Prof.)

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ACKNOWLEDGEMENTS

I owe a great debt to a number of people who generously gave me so much of their precious time, their

knowledge and their wisdom, and added whole dimensions to this report.I would like to thanks Dr. DPS

Chauhan, Prof. H.S.Mehta and Dr. Atul Upadhyay for all help and encouraging us for this “Industrial Visit”

for the student of Electrical and Electronics branch. I specially thanks to Ms. Karuna Nikum for arranging this

industrial visit. I am also grateful to Ms. Farheen Patel for many valuable ideas and suggestions and other

members or staffs who helped me directly or indirectly. I specially thanks to Mr. Swami Prasad (Assistant

Engineer) at NHDC without whose cooperation this report would not have been possible.

CONTENTS

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Acknowledgements

Abstract Page nos.

1. Introduction 6

2. Types Of Power Plant 7

2.1 Sources Of Energy 42.1.1 Non Conventional2.1.2 Conventional

2.2 Types of Hydro Power Plants 82.3 Comparison of Sources in India 10

3. Hydro electric Power Plant

3.1 Layout of Hydro electric Power Plant 123.2 Construction 133.3 Working 223.4 Advantage and Disadvantage 233.5 Detail of Narmada Hydroelectric Development Corporation(NHDC) 28

4. Transmission and Distribution System 39

4.1 Transmission4.1.1 Primary Transmission 404.1.2 Secondary Transmission 41

4.2 Distribution4.2.1 Primary Distribution 424.2.2 Secondary Distribution 43

5. Conclusion 52

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1. Introduction

OMKARESHWAR POWER STATION

Omkareshwar Power Station is a multipurpose project, which offers opportunity of power generation & irrigation on both the banks of river Narmada in districts Khandwa, Khargone & Dhar of Madhya Pradesh. The project is situated 80 km from Indore and 40 km down stream of Indira Sagar Project. The Cabinet Committee on Economic Affairs (CCEA) sanctioned the Project with an estimated cost of Rs.2224.73 Crores (Nov. 2002 Price Level) and total gestation period of 5 years. Omkareswar project was cleared by CCEA on 29.03.2003. The foundation stone of this project was laid by the then hon’ble Prime Minister of India Shri Atal Bihari Vajpayee on 30.08.2003 All the eight units of this project have started generation power from Nov. 2007 well ahead of sanctioned schedule. Due to early commissioning of units, substantial amount of savings has been made in the actual completion cost. Total installed capacity of the Omkareswar Project is 520 Megawatt (8x65). The project will generate 1167 Million Units energy, annually. Total catchments area at the proposed dame site is 64880 Sq. km, out of which 3238 Sq. is Downstream of Indira Sagar Power Station. The Project consists of 949 m long Concrete Gravity Dam with maximum height of 53 m from the deepest bed level across the river Narmada. A Central Ogee-type spillway 570 m long with crest level EL 179.6 m has been provided to pass the Probable Maximum Flood of 882315 cumecs. 23 No. Radial gates of size 20m x 18m have been erected for regulation of floodwater. 8 penstocks have been erected in 208 m long Power Dam with maximum height of 49m. 10 Nos. sluice gates of size 3.5m x 4.5m at the level of 173.5 m were provided for diversion purpose which has now been plugged. The surface Power House (202m x 23m x 53m) of the Project is within the body of Dam on the right bank of Narmada consisting of 8 Units of 65 MW capacity each with conventional Francis Type Turbines. Water is carried to the Turbines through 8 no. Penstocks of 7.66 m diameter each. After generation water is discharged back in the river through 145 m long Tail Race Channel

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1. Types of Power Plant

A Power Stations an industrial facility for the generation of electrical Power. Electricity generated at the power plant is transmitted at high voltage over great distances.

A Power Stations an industrial facility for the generation of electrical Power. Electricity generated at the power plant is transmitted at high voltage over great distances. The first power plants were run on water power or coal, and today we can depend on coal, nuclear, natural gas, solar energy, hydroelectricity, geothermal resources. Burning coal is the most polluting way to generate electricity.

There are many different Types of Power Generating Plants

●Solar Power Plants

●Thermal Power Plants

●Nuclear Power Plants

●Hydro Power Plants

Solar Power Plants: Solar energy arrives on the earth at a maximum power density of about 1 kilowatt per square meter. However, solar productivity is limited by certain geographical factors, including cloud cover and atmospheric humidity. In sunny, arid locations, one square kilometer of land can generate as much as 100 GW .Solar powered electricity generation is certainly good for the environment. India receives abundant sunlight. Solar Energy has been the power supply of choice for Industrial applications, transportation signaling, corrosion protection for pipelines solar energy is mainly used in solar heaters, solar dryers and solar cells. Nowadays, in most of the big cities in India, traffic lights are operated by solar energy. Solar energy does not cause any environmental pollution like the fossil fuels and nuclear power.

Thermal Power Plants: In a thermal power plant, the chemical energy stored in fossil fuels such as coal, fuel oil, natural gas is converted successively into thermal energy, mechanical energy and finally electrical energy.

The state of Maharashtra is the largest producer of thermal power in India.

Nuclear Power Plants: Nuclear energy is the energy released when certain changes take place in the nucleus of an atom. Nuclear power plants use the heat generated from nuclear fission in a contained environment to convert water to steam, which powers generators to produce electricity. There are lots of countries which uses Nuclear Power plants some of them are India, China, Pakistan, United States, Japan, Germany, South Korea, Canada, the United Kingdom, etc.Some of the Nuclear power plants are found in the states of Karnataka, Gujarat,TamilNadu,Rajasthan etcHydro Power Plants: Hydroelectricity is electricity generated by hydropower, i.e., the production of power through use of the gravitational force of falling or flowing water or  in other words the electricity produced from flowing water is called Hydroelectric power. Hydropower is a renewable source of energy as it is generating by a combination of the unending rain cycle and the abrupt topography of the earth.  India being one of the pioneering country in hydroelectric power in Asia which is located in State of Darjeeling.

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2.1 Sources of Energy

2.1.1 Non Conventional Energy Sources

Non-conventional (or unusual) sources of energy include:

a) Solar powerb) Hydro-electric power (dams in rivers)

c) Wind power

d) Tidal/ wave power

e) Geothermal power (heat from deep under the ground)

f) Biomass (burning of vegetation to stop it producing methane)

We hope that all the conventional sources will become rare, endangered and extinct, as they produce lots of carbon dioxide that adds to the greenhouse effect in the atmosphere (uranium leaves different dangerous byproducts).

And we similarly hope that all the non-conventional sources will become conventional, common, and every day, as they are all free, green and emit no carbon dioxide (well, biomass does, but it prevents the production of methane which is a greenhouse gas 21 times more dangerous that CO2).

a) Solar Energy

Solar energy is light and heat energy from the sun. Solar cells convert sunlight into electrical energy. Thermal collectors convert sunlight into heat energy. Solar technologies are used in watches, calculators, water pumps, space satellites, for heating water, and supplying clean electricity to the power grid. There is enough solar radiation striking the surface of the earth to provide all of our energy needs.

There are two main ways of using solar energy to produce electricity. These are through the use of solar cells and solar thermal technology. Using solar technologies to generate electricity is, at present, more expensive than using coal-fired power stations, but it produces much less pollution.

Solar cells are photovoltaic cells that turn light into electricity. Solar cells are used in three main ways. They are used in small electrical items, like calculators, and for remote area power supplies, like telephones and space satellites.

Solar cells are used to a limited extent in the development of solar-powered vehicles. Solar thermal technology uses heat gained directly from sunlight. The best known use of this technology is in solar water heating. Solar thermal electric generating plants use reflectors to collect heat energy to make steam which drives a turbine that produces electricity.

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b) Hydroelectric Energy

Fast-flowing water released from dams in mountainous areas can turn water turbines to produce electricity. While it doesn't cause pollution, there are many other environmental impacts to consider. Ecosystems may be destroyed, cultural sites may be flooded and sometimes people need to be resettled. There are also impacts on fish breeding, loss of wildlife habitat and changes in water flow of rivers.

Hydroelectricity is produced from falling water. The movement of the water spins turbines which generate electricity.

Places with high rainfall and steep mountains are ideal for hydroelectricity. Most hydroelectricity projects require the building of large dams on rivers, which can be very expensive. When large dams are built the flow of the dammed river is changed radically and large areas of land are flooded, including wildlife habitats and farming land.

Because of the environmental impact of traditional hydroelectric schemes, there has been increasing interest in alternative hydro schemes. Pumped storage systems can be installed on existing dams.

Run-of-river hydroelectric schemes cause less environmental damage. Large dams do not need to be built, as the run-of-river schemes divert only part of the river through a turbine.

c) Wind Energy

Moving air turns the blades of large windmills or generators to make electricity, or to pump water out of the ground. A high wind speed is needed to power wind generators effectively. While wind generators don't produce any greenhouse gas emissions they may cause vibrations, noise and visual pollution.

While wind-generated electricity does not cause air pollution, it does cost more to produce than electricity generated from coal.

Wind pumps and generators have been used in remote areas of Australia and in other countries around the world for many years. More recently, wind turbo-generators on wind farms have been providing electricity for cities and towns in more than a dozen countries. The United States of America and Denmark produce most of the world's wind-generated electricity. Australia has some small wind farms. The largest of these is at Esperance in Western Australia.A large wind turbo generator needs a minimum annual average wind speed of about 25 km/h. Sites need to be clear of tall vegetation and are often on prominent hills and headlands or in coastal areas. The southern states in Australia are in a good position to use wind generators because of a strong wind called the 'roaring forties' that blows across the south of the continent.Large wind generators can be more than 110 meters tall with blades spanning 130 meters. They can sometimes make a low-frequency sound that cannot be heard by humans, but which can rattle windows. Wind farms can be a danger to migrating birds flying at night and can cause TV and radio interference in nearby homes. Because of their size, some people think wind generators are ugly and spoil the scenery; however in some places they are a tourist attraction.

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d) Tidal/Wave Energy

If a dam or barrage is built across a river mouth or inlet, electricity can be obtained by the flow of water through turbines in the dam as the tide rises and falls. The movement of waves can also drive air turbines to make electricity. Although tidal and wave energy don't produce pollution, they can cause other environmental problems.

e) Geothermal Energy

Geothermal energy uses heat energy from beneath the surface of the earth. Some of this heat finds its way to the surface in the form of hot springs or geysers. Other schemes tap the heat energy by pumping water through hot dry rocks several kilometers beneath the earth's surface. Geothermal energy is used for the generation of electricity and for space and water heating in a small number of countries.

f) Biomass Energy

Biomass is plant and animal material that can be used for energy. This includes using wood from trees, waste from other plants (for example, bagasse from sugar cane) and manure from livestock. Biomass can be used to generate electricity, light, heat, motion and fuel. Converting biomass energy into useable energy has many environmental benefits. It uses waste materials that are usually dumped, and uses up methane (a greenhouse gas). Fuels such as ethanol can be made from biomass and used as an alternative to petrol to power motor cars.

All plant and animal matter is called biomass. It is the mass of biological matter on earth. We can get (biomass) energy:

Directly from plants, for example burning wood for cooking and heating. o Indirectly from plants, for example turning it into a liquid (alcohol such as ethanol) or gas (biogas) fuel.Indirectly from animal waste, for example biogas (mainly methane gas) from sewage and manure.An increasing number of renewable energy projects using biomass has been developed. Most of these use waste products from agriculture, so they solve a waste disposal problem and, at the same time, create energy for use in homes, farms and factories.

Biogas can also be produced from livestock manure and human sewage. Farms where animals graze and sewage plants are ideal places to produce energy from biogas. Waste peelings from food processing plants can also be used to produce biogas.

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2.1.2 Conventional Energy Sources

The term "Conventional" means "not unusual or extreme or ordinary." Conventional energy sources are the traditional sources of energy like coal and petroleum. In terms of being "usual", however, the impact on society by these sources is something extra-ordinary and have actually been quite serious. Conventional energy sources are finite. They will not last forever. What if all the petroleum reserves in the world come to an end? What if all the coal gets exhausted? It takes hundreds of years for a coal bed to get formed. It takes less than a month for the same to get extracted for use. Excessive use of these sources of energy result in global warming. Statistics tell that the average daily temperature of earth and the rainfall pattern has changed drastically. Ocean temperatures have increased. Number of days of rain, an important parameter in monsoon countries, has come down. Burning of coal produces harmful chemical emissions - Sulphur, Nitrogen Oxide and Mercury. All of these are known to have disastrous environmental and health effects on this fragile earth. Another form of pollution caused by the conventional sources is the "thermal pollution" or letting out of heat into the environment. When these fuels are burnt to be converted into other forms of energy, a lot of heat is produced and let out into the environment. This has resulted in climate changes - unseasonal rains, excessive rains, floods and drought in several parts of the world. The answer is "Non Conventional" sources of energy, which are naturally replenished.

Conventional sources of energy include fossil fuels, thermal energy.Fossil FuelsIt includes fuels which are most commonly used such as wood, coal and petroleum. These fossil fuels are non-renewable sources of energy. Therefore we need to conserve them.

Wood

It is a major source of energy for man as it is widely used for cooking and heating It is a primary fuel which can be used directly to produce heat

Coal

Coal varies in quality according to the amount of pressure and heat to which it is subjected to during its formation

It consists largely of carbon, hydrogen, oxygen and a small amount of sulphur and nitrogen

It is formed in layers called seams and takes millions of years to be formed

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2.2 Types of Hydro Power Plants

Classification of Hydro Power Plant

The hydro power plants are generally classified according to a) Availability of head b) according to the nature of load c) according to the quantity of water available for generation

a) Classification according to availability of head:

1. Low head power plant: Head of water available is below 30m2. Medium head power plant : Head of water available is between 30 to 100m3. High head plant : Head of water available is more than 100m

b) Classification according to nature of load (demand):

1. Base load plant: Plant designed for average load of the demand curve2. Peak load plant: Plant designed for peak load of the demand curve

c) Classification according to quantity of water available:

1. Run-off river plant without pondage :

It does not store the water and uses water as it comes.

Utility of this plant is very less as compared to others due to non- uniformity of and lack of assurance for continuous constant supply

2. Run-off river plant with pondage :

A pond is incorporated in the plant.

The pond stores water during off peak hours and uses during peak hours.

When providing pondage tail race conditions should be such that floods do not raise tail-race water level thus reducing the head on the plant and impairing its effectiveness.

This type of plant is comparatively more reliable and its generating capacity is less dependent on available rate of flow of water.

3. Storage type plants :

A storage plant is that which has a reservoir of such size as to permit carrying over storage from wet season to the next dry season.

Water is stored behind the dam and is available to the plant with control as required. Such a plant has better capacity and can be used efficiently throughout the year. Majority of the

hydroelectric plants are of this type.

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4. Pump storage plants : A pumped-storage plant has two reservoirs:

Upper reservoir - Like a conventional hydropower plant, a dam creates a reservoir. The water in this reservoir

flows through the hydropower plant to create electricity.

Lower reservoir - Water exiting the hydropower plant flows into a lower reservoir rather than re-entering the river and flowing downstream.

Using a reversible turbine, the plant can pump water back to the upper reservoir. This is done in off-peak hours. Essentially, the second reservoir refills the upper reservoir. By pumping water back to the upper reservoir, the plant has more water to generate electricity during periods of peak consumption

Low-cost off-peak electric power is used to run the pumps. During periods of high electrical demand, the stored water is released through turbines. Although the losses of the pumping process makes the plant a net consumer of energy overall, the system increases revenue, by selling more electricity during periods of peak demand, when electricity prices are highest.

d) Classification based on installed capacity:

Micro:  up to 100 KW Mini:     101KW to 2 MWSmall:   2 MW to 25 MWMega:   Hydro projects with installed capacity >= 500 MW

2.3 Comparison of Sources in India

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The primary energy requirement is anticipated to be 455 MMTOE in 2001-02 and isprojected to be 556.2 MMTOE and 722.3 MMTOE in the terminal years of the Tenth andEleventh Plans respectively. However due to an anticipated decline of the energyintensity, the actual demand may be 5 – 10 percent below the estimated figures. Therecommended fuel mix for the Tenth and Eleventh Plan Period is given in the Table 1.Table 1. Recommended Fuel Mix

In power sector, all India Installed Capacity of electric power generating stations underutilities was 104917.5 MW as on 31-03-2002 consisting of 26261.22 MW hydro,74428.82 MW thermal, 2720 MW nuclear and 1507.46 MW wind, detail break up ofwhich is given in Table. From the historical data it has been found that power generating capacity had increased impressively at a rate of over 12 per cent per annum during the 1960s. The 1970s could not maintain the momentum and recorded an annual increase of 7.5 per cent. Capacity addition during 1980s and 1990s recorded growth rate of 8.1 and 4.5 per centrespectively. Thermal generation during 1990-91 to 1999-00 moved up to 8.4 per cent perannum while growth in hydel generation was only 1.3 per cent per annum in the same period.

On the consumption side, industrial sector is the principal consumer of electricityfollowed by agricultural and domestic sector. The share of electricity consumption by theindustrial sector has been declining considerably due to higher power tariff anduncertainty in supply. The domestic sector shows the highest growth rate in electricityconsumption in the recent past. On the other hand, electricity consumption in theagricultural sector has been rising at a rate of 7-8 per cent due to government’s policy ofsupplying heavily subsidized power to the farmers and massive rural electrification.

In 2001-02, energy and peak load shortages were 7.5 and 12.6 per cent respectively andaccording to CEA estimates these shortages will be ballooning day by day as GDPgrowth accelerates to an ambitious 8 to 10 per cent. Under such circumstances,imaginative repositioning of the power sector is the need of hour to double the existingcapacity by 2012 in order to meet the higher growth trajectory and also accomplish the

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targeted mission of “Power for All’ by 2012.

Table 2: India’s perspective plan for electric power for zero deficit power by 2011/12(power on demand)

3. Hydro electric Power Plant

3.1 Layout of Hydro electric Power Plant

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Hydroelectric power plants convert the hydraulic potential energy from water into electrical energy. Such  plants are suitable were water with suitable head are available. The layout covered in this article is just a simple one and only cover the important parts of  hydroelectric plant.The different parts of  a hydroelectric power plant are

(1) DamDams are structures built over rivers to stop the water flow and form a reservoir.The reservoir stores the water flowing down the river. This water is diverted to turbines in power stations. The dams collect water during the rainy season and stores it, thus allowing for a steady flow through the turbines throughout the year. Dams are also used for controlling floods and irrigation. The dams should be water-tight and should be able to withstand the pressure exerted by the water on it. There are different types of dams such as arch dams, gravity dams and buttress dams. The height of water in the dam is called head race.

(2) SpillwayA spillway as the name suggests could be called as a way for spilling of water from dams. It is  used to provide for the release of flood water from a dam. It is used to prevent over toping of the dams which could result in damage or failure of  dams. Spillways could be controlled type or uncontrolled type. The uncontrolled types start releasing water upon water rising above a particular level. But in case of the controlled type, regulation of flow is possible.

(3) Penstock and TunnelPenstocks are pipes which carry water from the reservoir to the turbines inside power station. They are usually made of  steel and are equipped with gate systems.Water under high pressure flows through the penstock. A tunnel serves the same purpose as a penstock. It is used when an obstruction is present between the dam and power station such as a mountain.

(4) Surge TankSurge tanks are tanks connected to the water conductor system. It serves the purpose of reducing water hammering in pipes which can cause damage to pipes. The sudden surges of water in penstock is taken by the surge tank, and when the water requirements increase, it supplies the collected water thereby regulating water flow and pressure inside the penstock.

(5) Power StationPower station contains a turbine coupled to a generator. The water brought to the power station rotates the vanes of the turbine producing  torque and rotation of turbine shaft. This rotational torque is transfered to the generator and is converted into electricity. The used water is released through the tail race. The difference between head race and tail race is called gross head and by subtracting the frictional losses we get the net head available to the turbine for generation of electricity.

3.2 Construction of Hydro electric Power Plant

When designing a hydroelectric power plant a number of elements and equipment need to be taken into consideration. Dam size, retention basin size and depth, inlet valves, weir and control gates, penstock length and diameter, turbines, generators, transformers and excitation equipment, and efficiency all have to be examined.

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Elevation or head and stream flow have to be established as well. In our case we can achieve a maximum drop of 21 feet or 6.4 meters and have an average stream flow of 9070 cubic feet per second or 256.83 cubic meters per second. According to the INEEL hydropower resource database we can achieve 2500kW of electric power. Using this information we can find out how much of the flow we need to achieve 2500kW.

Plant Specifications

The next task is actually choosing the specifications for the plant. The main dam is already in place, as we chose a site with a pre-existing dam. However, in the spot where our power plant will sit, there will be a head of 21 feet. The dam is an integral part of the power plant. It is what controls the water; by damming up the water, the amount of water used to create power can be determined. When building a power plant from the ground up, the building of the dam would be the first step. Building a dam requires much research, approval, time, and money. The geology of the area must be taken into account (as was mentioned previously) so to avoid collapse due to geologic activity such as earthquakes. The size of the retention basin, or where the water sits behind the dam, must also be considered. Flow rate of the river and sediment load. must also be determined in order to establish an estimate on the dam lifetime. If the river carries a large sediment load, sediment will build up behind the dam more quickly than if there is less of a load. There are also mitigation techniques for removing sediment that can be considered for the project to lengthen lifetime. The dam also must go through an extensive approval and permit process. The Federal Energy Regulatory Commission is the main government body that provides the license for such a project as a hydroelectric power plant. Building dams and power plants takes a lot of time and money as well. There is always the chance of holdups and delays and sometimes projects can even run out of money. By choosing a site with an existing dam, all that needs to be done is some modifications – a choice that will require a lot less time and money (Woodward).

Upon approval and completion of the dam the actual power plant needs to be built and each component fashioned. The following picture is a schematic of a power plant and all of its component parts.

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Intake

The intake is the entrance to the system for the water. The inlet valves and control gate control how much water is going to enter the system. There are a number of different inlet valve designs. Three types that TOSHIBA Company of Japan offers are spherical or rotary, butterfly, and thruflow. GE Power Systems offers butterfly and rotary designs, as well as 6 others. We chose a thruflow (pictured left) as it has less head loss and leakage than the butterfly arotary (pictured right) designs (GE Power Systems and TOSHIBA).

The next step is the intake weir and where the water will enter the power plant. The weir also is responsible for diverting the water. It also must help keep solid material from entering the system. Three examples of intakes are the side intake without weir, side intake with weir, and bottom intake. A side intake without a weir is relatively cheap requiring no complex machinery, but asks for regular maintenance and repairs. At low flows very little water will be diverted so this type of intake is not suitable for rivers with great fluctuations in flow. The side intake with weir is a set-up in which the weir can be partially or completely submerged in the water. This design requires little maintenance but low flow cannot be diverted properly. The weir is completely submerged in the third design, the bottom intake. It is very useful with fluctuating flows and allows excess water to pass over the weir. With our location and dam we would use the side intake with weir design. It allows us the most flexibility and will be the most effective and economic (Micro Hydropower Basics).

Penstock 18

The Penstock is a tunnel that caries the water from the intake to the turbines. There are a number of factors to consider when deciding which material to use in the building of the penstock. They are: surface roughness, design pressure, method of jointing, weight and ease of installation, accessibility of the site, terrain, soil type, design life and maintenance, weather conditions, availability, relative cost, and likelihood of structural damage. When considering soil type, you have to choose a material that will not be degraded or eroded by the surrounding soil. Economically speaking, the penstock can account for up to 40% of total cost of the plant. This is why efficient planning is critical (Micro Hydropower Basics).

Turbines

Once the water flows down the penstock, it passes and turns the turbines. There are a number of different models of turbines depending on which company the turbine is purchased from. However, there are common designs. Two different types of turbines are impulse and reaction turbines. Impulse turbines include Pelton, Turgo, cross-flow, and multi jet Pelton designs. Reaction turbines include the Francis, propeller, and Kaplan turbines. There are different designs specified for different head values. High head requires either a Pelton or Turgo, medium head calls for cross-flow, multi-jet, or Francis, and low head requires cross-flow, propeller, or Kaplan. In our situation, we have medium head so the cross-flow is going to be the best design for us. Also, the cross-flow has to be horizontal and that will work the best with our set up. “Also called a Michell-Banki turbine a cross-flow turbine has a drum-shaped runner consisting of two parallel discs connected together near their rims by a series of curved blades. A crossflow turbine always has its runner shaft horizontal (unlike Pelton and

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Turgo turbines which can have either horizontal or vertical shaft orientation)” (Micro Hydropower). A specific type of cross-flow turbine is the Ossberger. It has an efficiency of up to 86%. It can operate in head ranges of 1-200m and with water flows of 0.025-13 cubic meters per second.

Due to these specifications, we will need to use four turbines at our location to generate the maximum amount of power. Ossberger turbines are relatively slow moving at 20-80 revolutions per minute. “The Ossberger turbine is a radial and partial admission free stream turbine. From its specific speed it is classified as a slow speed turbine. The guide vanes impart a rectangular cross-section to the water jet. It flows through the blade ring of the cylindrical rotor, first from the outside inward, then after passing through the inside of the rotor from the inside outward. Where the water supply requires, the Ossberger is built as a multi-cell turbine. The normal division in this case is 1:2. The small cell utilizes small and the big cell medium water flow. With this breakdown, any water flow from 1/6 to 1/1 admission is processed with optimum efficiency. This explains why Ossberger turbines utilize greatly fluctuating water supplies with particular efficiency”

Generators, Transformers, and Electricity Production

Water flows through the turbine to turn it and its shaft to create mechanical energy that is transformed into electrical energy by the generators and transformers. Depending on the company purchased from, there are a number of different models of generators. Two main designs are the vertical or horizontal arrangements (TOSHIBA). There are four major components to the generator; they are the shaft, exciter, rotor, and stator. The water turns the turbine, which turns the shaft and causes the exciter to send an electrical current to the rotor. The rotor is comprised of a series of large electromagnets that spin inside the stator, which is a tightly wound coil of copper wire. This process creates a magnetic field, which creates an alternating current, AC, by the moving of electrons. The transformer then converts the AC to a higher voltage current. The generator and transformer sit in what is known as the powerhouse. This is the main building of the hydropower plant. From the powerhouse there are four main wires that leave. There are three for the three phases of produced power and a ground wire common to the other three. These power lines are connected to the regional power grid. The last component to the system is the tailrace. The tailrace is simply the pipelines that carry the water back out to the river.

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3.3 Working of Hydro electric Power Plant

In earlier times, water mills were used to generate hydropower. Now they are rarely found and advanced technology such as water turbines has taken its place. No matter how advanced, it still runs on the basic concept of extracting energy produced by flowing water. Advanced technology used in hydropower plants work on the same foundation. The process in which they work is explained below: 

Rivers are blocked in various points on their course with construction of dams which create a large reservoir of water.

Once the dam gates are opened, the water forcefully gushes out through a pipeline (called penstock) which is connected to the turbine. The water pressure in the pipe begins to rise.

A generator is attached to the turbine through a shaft.

At the end of the pipe, the water turns the turbine blades that are connected to the generator.

In tandem with the each rotation of the turbine blades, there is a series of magnets inside the generator that rotate too. These magnets rotate inside tightly-wounds copper coils, producing alternating current (AC).

In the powerhouse, the transformer that is connected to the generator converts AC into higher voltage electricity.

The power lines then carry this electricity

from the powerhouse to the end consumer.

The water used in this process is carried through pipelines called ‘tailraces,’ back into the river downstream. 

Hydropower is a renewable, natural resource that can be effectively used to meet energy needs. Hydropower is a more preferred source of energy as it is considered less expensive compared to sun and wind power generation.  

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3.4 Advantage and Disadvantage of Hydro electric Power Plant

Advantages

The Ffestiniog Power Station can generate 360 MW of electricity within 60 seconds of the demand arising.

Economics

The major advantage of hydroelectricity is elimination of the cost of fuel. The cost of operating a hydroelectric plant is nearly immune to increases in the cost of fossil fuels such as oil, natural gas or coal, and no imports are needed.

Hydroelectric plants also tend to have longer economic lives than fuel-fired generation, with some plants now in service which were built 50 to 100 years ago.[13] Operating labor cost is also usually low, as plants are automated and have few personnel on site during normal operation.

Where a dam serves multiple purposes, a hydroelectric plant may be added with relatively low construction cost, providing a useful revenue stream to offset the costs of dam operation. It has been calculated that the sale of electricity from the Three Gorges Dam will cover the construction costs after 5 to 8 years of full generation.[14]

CO2 emissions

Since hydroelectric dams do not burn fossil fuels, they do not directly produce carbon dioxide. While some carbon dioxide is produced during manufacture and construction of the project, this is a tiny fraction of the operating emissions of equivalent fossil-fuel electricity generation. One measurement of greenhouse gas related and other externality comparison between energy sources can be found in the ExternE project by the Paul Scherrer Institut and the University of Stuttgart which was funded by the European Commission.[15] According to this project, hydroelectricity produces the least amount of greenhouse gases and externality of any energy source.[16] Coming in second place was wind, third was nuclear energy, and fourth was solar photovoltaic.[16]

The extremely positive greenhouse gas impact of hydroelectricity is found especially in temperate climates. The above study was for local energy in Europe; presumably similar conditions prevail in North America and Northern Asia, which all see a regular, natural freeze/thaw cycle (with associated seasonal plant decay and regrowth).

Other uses of the reservoir

Reservoirs created by hydroelectric schemes often provide facilities for water sports, and become tourist attractions themselves. In some countries, aquaculture in reservoirs is common. Multi-use dams installed for irrigation support agriculture with a relatively constant water supply. Large hydro dams can control floods, which would otherwise affect people living downstream of the project.

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Disadvantages

Ecosystem damage and loss of land

Hydroelectric power stations that uses dams would submerge large areas of land due to the requirement of a reservoir.

Large reservoirs required for the operation of hydroelectric power stations result in submersion of extensive areas upstream of the dams, destroying biologically rich and productive lowland and riverine valley forests, marshland and grasslands. The loss of land is often exacerbated by the fact that reservoirs cause habitat fragmentation of surrounding areas.

Hydroelectric projects can be disruptive to surrounding aquatic ecosystems both upstream and downstream of the plant site. For instance, studies have shown that dams along the Atlantic and Pacific coasts of North America have reduced salmon populations by preventing access to spawning grounds upstream, even though most dams in salmon habitat have fish ladders installed. Salmon spawn are also harmed on their migration to sea when they must pass through turbines. This has led to some areas transporting smolt downstream by barge during parts of the year. In some cases dams, such as the Marmot Dam, have been demolished due to the high impact on fish.[17] Turbine and power-plant designs that are easier on aquatic life are an active area of research. Mitigation measures such as fish ladders may be required at new projects or as a condition of re-licensing of existing projects.

Generation of hydroelectric power changes the downstream river environment. Water exiting a turbine usually contains very little suspended sediment, which can lead to scouring of river beds and loss of riverbanks.[18] Since turbine gates are often opened intermittently, rapid or even daily fluctuations in river flow are observed. For example, in the Grand Canyon, the daily cyclic flow variation caused by Glen Canyon Dam was found to be contributing to erosion of sand bars. Dissolved oxygen content of the water may change from pre-construction conditions. Depending on the location, water exiting from turbines is typically much warmer than the pre-dam water, which can change aquatic faunal populations, including endangered species, and prevent natural freezing processes from occurring. Some hydroelectric projects also use canals to divert a river at a shallower gradient to increase the head of the scheme. In some cases, the entire river may be diverted leaving a dry riverbed. Examples include the Tekapo and Pukaki Rivers in New Zealand.

Flow shortage

Changes in the amount of river flow will correlate with the amount of energy produced by a dam. Lower river flows because of drought, climate change or upstream dams and diversions will reduce the amount of live storage in a reservoir therefore reducing the amount of water that can be used for hydroelectricity. The result of diminished river flow can be power shortages in areas that depend heavily on hydroelectric power.

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Methane emissions (from reservoirs)

The Hoover Dam in United States is a large conventional dammed-hydro facility, with an installed capacity of up to 2,080 MW.See also: Environmental impacts of reservoirs

Lower positive impacts are found in the tropical regions, as it has been noted that the reservoirs of power plants in tropical regions may produce substantial amounts of methane. This is due to plant material in flooded areas decaying in an anaerobic environment, and forming methane, a very potent greenhouse gas. According to the World Commission on Dams report,[19] where the reservoir is large compared to the generating capacity (less than 100 watts per square metre of surface area) and no clearing of the forests in the area was undertaken prior to impoundment of the reservoir, greenhouse gas emissions from the reservoir may be higher than those of a conventional oil-fired thermal generation plant.[20] Although these emissions represent carbon already in the biosphere, not fossil deposits that had been sequestered from the carbon cycle, there is a greater amount of methane due to anaerobic decay, causing greater damage than would otherwise have occurred had the forest decayed naturally.

In boreal reservoirs of Canada and Northern Europe, however, greenhouse gas emissions are typically only 2% to 8% of any kind of conventional fossil-fuel thermal generation. A new class of underwater logging operation that targets drowned forests can mitigate the effect of forest decay.[21]

In 2007, International Rivers accused hydropower firms for cheating with fake carbon credits under the Clean Development Mechanism, for hydropower projects already finished or under construction at the moment they applied to join the CDM. These carbon credits – of hydropower projects under the CDM in developing countries – can be sold to companies and governments in rich countries, in order to comply with the Kyoto protocol.[22]

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Relocation

Another disadvantage of hydroelectric dams is the need to relocate the people living where the reservoirs are planned. In February 2008, it was estimated that 40-80 million people worldwide had been physically displaced as a direct result of dam construction. In many cases, no amount of compensation can replace ancestral and cultural attachments to places that have spiritual value to the displaced population. Additionally, historically and culturally important sites can be flooded and lost.

Such problems have arisen at the Aswan Dam in Egypt between 1960 and 1980, the Three Gorges Dam in China, the Clyde Dam in New Zealand, and the Ilisu Dam in Turkey.

Failure hazard

Main article: Dam failure

Because large conventional dammed-hydro facilities hold back large volumes of water, a failure due to poor construction, terrorism, or other causes can be catastrophic to downriver settlements and infrastructure. Dam failures have been some of the largest man-made disasters in history. Also, good design and construction are not an adequate guarantee of safety. Dams are tempting industrial targets for wartime attack, sabotage and terrorism, such as Operation Chastise in World War II.

The Banqiao Dam failure in Southern China directly resulted in the deaths of 26,000 people, and another 145,000 from epidemics. Millions were left homeless. Also, the creation of a dam in a geologically inappropriate location may cause disasters like the one of the Vajont Dam in Italy, where almost 2000 people died, in 1963.

Smaller dams and micro hydro facilities create less risk, but can form continuing hazards even after they have been decommissioned. For example, the small Kelly Barnes Dam failed in 1967, causing 39 deaths with the Toccoa Flood, ten years after its power plant was decommissioned in 1957. [25]

Comparison with other methods of power generation

Hydroelectricity eliminates the flue gas emissions from fossil fuel combustion, including pollutants such as sulfur dioxide, nitric oxide, carbon monoxide, dust, and mercury in the coal. Hydroelectricity also avoids the hazards of coal mining and the indirect health effects of coal emissions. Compared to nuclear power, hydroelectricity generates no nuclear waste, has none of the dangers associated with uranium mining, nor nuclear leaks. Unlike uranium, hydroelectricity is also a renewable energy source.

Compared to wind farms, hydroelectricity power plants have a more predictable load factor. If the project has a storage reservoir, it can be dispatched to generate power when needed. Hydroelectric plants can be easily regulated to follow variations in power demand.

Unlike fossil-fuelled combustion turbines, construction of a hydroelectric plant requires a long lead-time for site studies, hydrological studies, and environmental impact assessment. Hydrological data up to 50 years or more is usually required to determine the best sites and operating regimes for a large hydroelectric plant. Unlike plants operated by fuel, such as fossil or nuclear energy, the number of sites that can be economically developed for hydroelectric production is limited; in many areas the most cost effective sites have already been exploited.

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New hydro sites tend to be far from population centers and require extensive transmission lines. Hydroelectric generation depends on rainfall in the watershed, and may be significantly reduced in years of low rainfall or snowmelt. Long-term energy yield may be affected by climate change. Utilities that primarily use hydroelectric power may spend additional capital to build extra capacity to ensure sufficient power is available in low water years.

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3.4 Details of Narmada Hydroelectric Development Corporation(NHDC)

SALIENT FEATURES

LOCATION(1) State in which it is located : Madhya Pradesh

(2) Name of the District : East Nimar (Khandwa)

(3) Name of the River : Narmada

(4) Location of Dam : 1 KM downstream of the confluence of river Narmada and its tributary river kaveri.

CONCRETE GRAVITY DAM1. Total length : 949 meters

(i) Non overflow : 167 meters

(ii) Overflow Portion (Spillway : 570 meters

(iii) Power dam : 212 meters

2. Maximum height : 56.50 meters

RADIAL CREST GATES

1. Number : 232. Length : 20 meters

3. Width : 18.037 meters

RESERVOIR LEVELS1. Top level of Dam : 203.00 meters

2. maximum water level : 199.62 meters

3. F.R.L. : 196.60 meters

4. M.D.D.L. : 193.54 meters

5. Crest level (spillway) : 179.60 meters

6. water Spread area at F.R.L. : 93.36 sq. meters

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WATER CONDUCTOR SYSTEM1. Number of penstock : 8

2. Diameter of Penstock : 7.66 meters

HEAD 1. Maximum Head : 34.08 meters

2. Minimum Head : 28.89 meters

3. Designed Head : 31.95 meters

4. Design Discharge Per Unit : 237.25 cumecs

HEAD RACE CHANNEL

1. Length : 171.5 meters

2. Width : 222 meters (Varying)

3. Bed level : 169.50 meters

TAIL RACE CHANNEL1. Length : 145 meters

2. Width : 192.84 – 204.16 meters

3. Maximum Tail Level : 164.65 meters

4. Minimum Tail Water Level : 162.52 meters

POWER HOUSE

1. Type of Power House : Surface

2. Installed Capacity : 520 MW (8X65)

3. Firm Power Generation : 131.20 MW

4. Type of Turbine : Vertical Shaft Francis Spiral

SWITCH YARD1. Type : 220 KV, surface

2. No. of Bus : 2

3. No. of Bays (Generator/Line/Bus) : 8 + 5 + 1

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TECHNICAL SPECIFICATIONS OF MAIN COMPONENTS

A) TURBINE

Type : Vertical Shat Francis Spiral

Numbers : 08

Rated Output P : 66.33 MW

Rated Speed N : 93.75 RPM

Rated Flow Q : 230.4 M3 / 5

Rated Head H : 31.09 M

Runway Speed ND (Max) : 185 RPM

No. of blades : 11

Outer Dia : 5760 mm

Weight : 64.4 T

Shaft Dia : 950 mm

B) GUIDE VANE

No. of wicket gate : 24

Guide Van Height : 1800 mm

Guide Van Opening : 545.0 mm

Weight / Per piece : 1.55 T

C) DRAFT TUBE

Draft tube cone inlet dia : 5675.0 mm

Draft tube outlet width : 18160.0 mm

Draft tube outlet height : 7150.0 mm

D) LOWER GUIDE BEARING

Bearing Inner Dia : 1300.0 mm

Bearing Segment Size : 315 mm

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Number of segment : 8

LGB Weight / Per piece : 0.1 T

E) COMBINED THRUST GUIDE BEARING

G.B. Weight / Segment : 0.05 T

G.B. Inner Dia : 2350 mm

G.B. Segment Size : 250 mm

No. of Segment : 12

Thrust Bearing Inner Dia : 1500 mm

Thrust Bearing Pad size : 420 mm

No. of Bearing Pads : 12

Weight Thrust Pad / piece : 0.14 T

F) AIR ADMISSION

Air Admission on Supply Pipe Line : 300.0 m

G) PEN STOCK GATE

No. of Gate : 8

Size of Gate : 7.3 m X 8.73 n (H)

GENERATORRated Output : 72.220 MVA

Maximum Power : 79.440 MVA

Rated Voltage : 11 KV

Rated Current : 3791 MVA

Rated Frequency : 50 HZ

Rated Power Factor : 0.9

No of Pole : 64

Rated Speed ; 93.8 RPM

Runway Speed : 185 RPM

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Class in Insulation Stator : F

Class in Insulation Rotor : F

Maximum High Temperature Stator : 128 C

Maximum High Temperature Rotor : 133 C

Rated Excitation Current : 908 AMP

No load Excitation Current : 526 AMP

Type of Excitation : Static

Continuous generator : 60.5 MVA

OUTPUT CHARGING A TRANSMISSION LINE

Stator Winding Resistance : 17.8 MZ

Rotor Winding Resistance : 157 MZ

Stator winding Caparifable : 0.84 MF/Phase

BUS DUCT (MAIN)

Conductor ; Aluminum Alloy

Rating : 5000 AMP

Rates Voltage : 11 KV

Enclosure : Aluminum

BUS DUCT (AUXILIARY)

Connector : Aluminum Alloy

Rating : 100 AMP

Voltage Rating : 11 KV

Enclosure : Aluminum

EXCITATION TRANSFORMERType : 3 Phase Dry Type

Eating : 532 KVA

Rated Voltage (Primary) : 11 KV

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Rated Voltage (Secondary) : 342 V

Primary Current : 27.92 AMP

Secondary Current : 898.1 AMP

Impedance : 6.8%

Cooling : AN

Make : Ocrev – Italy

GENERATOR TRANSFORMERType : 3 Phase Oil immersed Transformer

Rating : 80 MVA

Rated Voltage (LV) : 11 KV

Rated Voltage (HV) : 220 KV

Rated Current (LV) : 4198.91 AMP

Rated current (HV) : 209.94 AMP

Cooling Type : OFWF

Oil Capacity : 38000 Litre

Vector Group : Ynd - 11

COOLING WATER SYSTEMNo. of motor pump set / Unit : 2

Operating Pressure : 4 to 7 bars

Motor Rating : 55 KW

Current Rating : 95 AMP

Water required for 12 Generator Coolers : 217.1 M3 Per H

Water Required for 2 Transformer

Oil Coolers : 40.6 M3 Per H

Water required for 3 Combined bearing Oil

Coolers : 32.1 M3 Per H

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Water Required for TGB Oil Coolers : 1.3 M3 Per H

Water Required for HVAC Cooling : 15.0 M3 Per H

Shaft Seal : 5 M3 Per H

Filter Type : Filter

HP COMPRESSOR SYSTEMNo. of Compressor for all units : 2

Volume of Supplied air reffered to initial

Condition Capacity : 200 Ltr. Per Min.

Working Pressure : 9.0 MPA (90Kg/cm2)

SERVO MOTORNo. of Servomotor Per Unit : 2

Piston diameter : 350 mm

Piston rod diameter : 140 mm

Maximum stroke ; 521 mm

Nominal stroke : 506 mm

Design pressure : 6.4 MPA

Maximum working pressure : 6.0 MPA

Minimum working pressure : 4.0 MPA

GOVERNOR OIL PUMPS No. of pump per unit : 2

Rating of Motor : 15 MW

Nominal speed : 1460 VPM

Type : 3 , 50 H

Working pressure : 6.0 MPA

Pump discharge : 96 M3 Per Min.

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220 BATTERY BANKMake : Exide

Type : TH – 12004

No. of Bank : 2

No. of battery per bank : 108

AH Rating : 1200 H (10 hr. discharge)

Ah Rating : 600 AH ( 1 hr. discharge)

Normal charging current : 120 A

Maximum permissible charged current : 144 A

220 BATTERY CHARGERSType : Float Per Boost Type

AC supply : 415 + 10%, 3

Adjustable voltage : 220 V – 245 V (Float)

Range : 195 – 290 V (Boost)

Rated DC Current : 150 A (Float) / 180 A (Boost)

48 V DC BATTERY BANKMake :

Type : Ni-cd battery

CIRCUIT BREAKER

Make : ABB

Type : SF 6

Rated continues current : 2500

Short time current ratings : 40 VA for 3 sec.

No. of quenching chambers : 1

Mechanical opening time : 35 MS

Total breaking time : 60 MS

Total closing time : 130 MS 37

Operating mechanism : Pneumatic

Control voltage : 220 V QC

ISOLATOR

Rated continuous current : 2500 A

Short time current rating : 40 KA for 1 sec.

Total operating time : 8 – 12 Seconds.

Type : 3 pole, wale brake

No. of auxiliary contact : 6 No. + 6 NC

OUT DOOR CTMake : ABB

Ratio : 2500 – 500 – 300 - 1

Accuracy class (Protection) : 5 P 20, PS / 20 Accuracy class (Metering) : 0.5 / 20

CVTMake : ABB

Ratio : 220 KV / 3

Accuracy class (Protection) : 3 P

Accuracy class (Metering) : 02

Normal capacitance : 4400 PF

High frequency range : 40 – 500 KHZ

No. of core : 3

SURGE ARRESTOR

Make : CGL

Type : Station, Gapless

Rated voltage : 198 KV

Continuous & Maximum operating voltage : 168 KV

Discharge current : 10 KA 38

Class : 3

WAVE TRAPMake : Alstom

Type : Pedastal

Rated continuous current : 1250 A

Inductance : 0.5 MH

Nominal discharge current : 10 KA

DG SET

Make : Kirloskar comers

Rating : 2 X 1010 KVA

Rated generation voltage : 11 KV

Speed : 1500 RPM

Excitation : Brashness self excitation

PROTECTION RELAYS

GENERATOR

REG 316 * 4 (VAR – 2) [Main 1 & 2]

- Generator break up Impedance Protection (21 G) - Reverse power protection (32 G) - Loss of excitation protection (40 G) - Negative phase sequence protection (46 C) - Generator over voltage protection (59 G) - Generator under voltage protection (27 G) - Over flux protection (99 V/F) - Generator differential protection (87G) - Pole slipping protection (98 F) - Instantaneous / Time delay over current protection 50/51 - Stator overload protection (49 S) - Under / Over frequency protection (81) Voltage controlled O/C protection (5/27 G)

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11KV Substation

4. Transmission and Distribution System

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The electric power is generated at the power stations, which are located far away from consumers. It is then transmitted over large distances to load centres with help of conductors. These lines are known as transmission lines. The power station, transmission lines and load centres are called as transmission system.

The electric power is transferred from load centres to the consumer premises with help of conductors, which is known as distribution system.

Transmission and Distribution System

4.1.1 Primary Transmission

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The transmission system is the bulk power transfer system between the power generation station and the distribution center from which power is carried to customer delivery points. The transmission system includes step-up and step-down transformers at the generating and distribution stations,respectively. The transmission system is usually part of the electric utility's network. Power transmission systems may include subtransmission stages to supply intermediate voltage levels. Subtransmission stages are used to enable a more practical or economical transition between transmission and distribution systems.Transmission Voltage:Usually, generated power is transformed in a substation, located at the generating station, to 46 kV or more for transmission. Standard nominal transmission system voltages are: 69 kV, 115 kV, 138 kV, 161 kV and 230 kV. Some transmission voltages,however, may be at 23 kV to 69 kV, levels normally categorized as primary distribution system voltages. There are also a few transmission networks operating in the extra-high-voltage class (345 kV to 765 kV).Transmission Lines: Transmission lines supply distribution substations equipped with transformers which step the high voltages down to lower levels. The transmission of large quantities of power over long distances is more economical at higher voltages. Power transmission at high voltage can be accomplished with lower currents which lower the I2R(Power) losses and reduce the voltage drop.

4.1.2 Secondary Transmission

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A power transmission system is sometimes referred to as a "grid", which is a fully connected network of transmission lines. The Regional Power Grids are established for optimal utilization of the power generated from the unevenly distributed power generating stations, by having intra-regional and inter-regional power exchanges depending upon day-to-day power availability and load conditions. The surplus power is transferred to the power deficit regions. Due to the large amount of electric power involved, transmission normally takes place at high voltage (110 kV or above). Electric power is usually sent over long distances through overhead power transmission lines. Power is transmitted underground in densely populated areas, such as large cities, but is typically avoided due to the high capacitive and resistive losses incurred. Redundant paths and lines are provided so that power can be routed from any power plant to any load center, through a variety of routes, based on the economics of the transmission path and the cost of power. The grid consists of two infrastructures: the high-voltage transmission systems, which carry electricity from the power plants and transmit it hundreds of miles away, and the lower-voltage distribution systems, which draw electricity from the transmission lines and distribute it to individual customers. High voltage is used for transmission lines to minimize electrical losses; however, high voltage is impractical for distribution lines. Electricity distribution is the penultimate process in the delivery of electric power, i.e. the part between transmission and user purchase from an electricity retailer. It is generally considered to include medium-voltage (less than 50kV) power lines, low-voltage electrical substations and pole-mounted transformers, low-voltage (less than 1000V) distribution wiring and sometimes electricity meters. This interface features transformers that "step down" the transmission voltages to lower voltages for the distribution systems. Transformers located along the distribution lines further step down the voltage for household use. Substations also include electrical switchgear and circuit breakers to protect the transformers and the transmission system from electrical failures on the distribution lines. Circuit breakers are also located along the distribution lines to locally isolate electrical problems (such as short circuits caused by downed power lines).

4.2.1 Primary Distribution

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The transmission system voltage is stepped-down to lower levels by distribution substation transformers. The primary distribution system is that portion of the power network between the distribution substation and the utilization transformers.The primary distribution system consists of circuits, referred to as primary or distribution feeders that originate at the secondary bus of the distribution substation. The distribution substation is usually the delivery point of electric power in large industrial or commercial applications.

Nominal System Voltages: Primary distribution system voltages range from 2,400 V to69,000 V. Some of the standard nominal system voltages are:

The primary distribution voltages in widest use are 12,470 V and 13,200 V, both three wire andfour wire. Major expansion of distribution systems below the 15 kV nominal level (12 kV - 14.4 kV) is not recommended due to the increased line energy costs inherent with lower voltagesystems.

4.2.2 Secondary Distribution

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The secondary distribution system is that portion of the network between the primary feeders and utilization equipment. The secondary system consists of step-down transformers and secondary circuits at utilization voltage levels.Residential secondary systems are predominantly single-phase, but commercial and industrialsystems generally use three-phase power.

Secondary Voltage Levels: The voltage levels for a particular secondary system aredetermined by the loads to be served. The utilization voltages are generally in the range of 120 to600 V. Standard nominal system voltages are:

In residential and rural areas the nominal supply is a 120/240 V, single-phase, three-wiregrounded system. If three-phase power is required in these areas, the systems are normally208Y/120 V or less commonly 240/120 V. In commercial or industrial areas, where motor loadsare predominant, the common three-phase system voltages are 208Y/120 V and 480Y/277 V.The preferred utilization voltage for industrial plants, however, is 480Y/277 V. Three-phasepower and other 480 V loads are connected directly to the system at 480 V and fluorescentlighting is connected phase to neutral at 277 V. Small dry-type transformers, rated480-208Y/120 or 480-120/240 V, are used to provide 120 V single-phase for convenience outletsand to provide 208 V single- and three-phase for small tools and other machinery.

5. Conclusion

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In conclusion, there were many thing that I have experience and learned during the visit at NHDC, Omkareshwar. The

whole training period was very interesting, instructive and challenging. Through this training I was able to gain new

insights and more comprehensive understanding about the real electricity generation and transmission. The visit also has

provided me the opportunities to develop and improve my basic knowledge. All of this valuable experience and

knowledge that I have gained were not only acquired through the direct involvement in visit provided but also through

other aspects.From what I have undergone, I am hundred percent agree that the industrial training program have achieve

its entire primary objective. It’s also the best ways to prepare student in facing the real working life. As a result of the

program now I am more confident to enter the employment world and build my future career.

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