unit- i - rgmcet · amount of super heater surface installed, as well as the rating of the boiler....

UNIT- I

A Thermal Power Plant converts the heat energy of coal

into electrical energy.

Coal is burnt in a boiler which converts water into steam.

The expansion of steam in turbine produces mechanical

power which drives the alternator coupled to the turbine.

Thermal Power Plants contribute maximum to the generation

of Power for any country.

Thermal Power Plants constitute 75.43% of the total installed

captive and non-captive power generation in India.

In thermal generating stations coal, oil, natural gas etc. are

employed as primary sources of energy.

Thermal Power plant

General Layout of Thermal Power Station

Diagr am of a typical coal -f ired t hermal

pow er s tation

1. Cooling tower 10. Steam Control valve 19. Superheater

2. Cooling water pump 11. High pressure steam turbine 20. Forced draught (draft) fan

3. transmission line (3-phase) 12. Deaerator 21. Reheater

4. Step-up transformer (3-phase) 13. Feed water heater 22. Combustion air intake

5. Electrical generator (3-phase) 14. Coal conveyor 23. Economiser

6. Low pressure steam turbine 15. Coal hopper 24. Air preheater

7. Condensate pump 16. Coal pulveriser 25. Precipitator

8. Surface condenser 17. Boiler steam drum 26. Induced draught (draft) fan

9. Intermediate pressure steam

turbine 18. Bottom ash hopper 27. Flue gas stack

D i a gr am o f a t y p ical c o al - f ire d

t h e r m al p ow er s tat ion

Main and Auxiliary e q u i p m e n t s

1. Coal handling plant 2. Pulverizing plant 3. Draft fans 4. Boiler 5. Ash handling plant 6. Turbine 7. Condenser 8. Cooling towers and ponds 9. Feed water heater 10. Economiser 11. Superheater and Reheater 12. Air preheater

Coal handling plant

•The function of coal handling plant is automatic feeding of coal to the

boiler furnace.

• A thermal power plant burns enormous amounts of coal.

•A 200MW plant may require around 2000 tons of coal daily

Pulverising plant

In modern thermal power plant , coal is pulverised i.e. ground to dust like size and carried to the furnace in a stream of hot air. Pulverising is a means of exposing a large surface area to the action of oxygen and consequently helping combustion. Pulverising mills are further classified as: 1. Contact mill 2. Ball mill 3. Impact mill

Draft system

• The circulation of air is

caused by a difference in

pressure, known as Draft.

• Draft is a differential

pressure b/w atmosphere

and inside the boiler.

• It is necessary to cause the

flow of gases through boiler

setting

• It may be –

1. Natural draft

2. Mechanical draft

Boiler

• A boiler or steam generator is a closed vessel in which water

under pressure, is converted into steam.

• It is one of the major components of a thermal power plant

• Always designed to absorb maximum amount of heat released in

the process of combustion

Boilers are of two types-

1. Fire tube boiler

2. Water tube boiler

Superheater and reheater

Most of the modern boilers are having super heater and reheater arrangement.

Superheater :

Superheater is a component of a steam-generating unit in which steam, after it

has left the boiler drum, is heated above its saturation temperature. The amount

of superheat added to the steam is influenced by the location, arrangement, and

amount of super heater surface installed, as well as the rating of the boiler. The

super heater may consist of one or more stages of tube banks arranged to

effectively transfer heat from the products of combustion. Super heaters are

classified as convection , radiant or combination of these.

Reheater : Some of the heat of superheated steam is used to rotate the turbine where it loses some of its energy.

Reheater is also steam boiler component in which heat is added to this intermediate-pressure steam, which has given up some of its energy in expansion through the high-pressure turbine.

The steam after reheating is used to rotate the second steam turbine where the heat is converted to mechanical energy. This mechanical energy is used to run the alternator, which is coupled to turbine , there by generating electrical energy.

Turbine

Turbine – Full View

Steam turbine

A steam turbine converts heat energy of steam into mechanical energy

and drives the generator. It uses the principle that steam when issuing

from a small opening attains a high velocity. This velocity attained during

expansion depends on the initial and final heat content of the steam. This

difference b/w initial and final heat content represents the heat energy

converted into kinetic energy.

These are of two types :-

Impulse turbine

Reaction turbine

Ash handling plant

The percentage of ash in coal varies from 5% in good quality

coal to about 40% in poor quality coal

Power plants generally use poor quality of coal , thus amount

of ash produced by it is pretty large

A modern 2000MW plant produces about 5000 tons of ash

The stations use some conveyor arrangement to carry ash to

dump sites directly or for carrying and loading it to trucks and

wagons which transport it to the site of disposal

Condenser

Steam after rotating steam turbine comes to condenser. Condenser refers here to the shell and tube heat exchanger (or surface condenser) installed at the outlet of every steam turbine in Thermal power stations of utility companies generally. These condensers are heat exchangers which convert steam from its gaseous to its liquid state, also known as phase transition. In so doing, the latent heat of steam is given out inside the condenser. Where water is in short supply an air cooled condenser is often used. An air cooled condenser is however significantly more expensive and cannot achieve as low a steam turbine backpressure (and therefore less efficient) as a surface condenser. The purpose is to condense the outlet (or exhaust) steam from steam turbine to obtain maximum efficiency and also to get the condensed steam in the form of pure water, otherwise known as condensate, back to steam generator or (boiler) as boiler feed water.

Cooling towers and ponds

o A condenser needs huge quantity of water to condense the steam .

o Typically a 2000MW plant needs about 1500MGallon of water.

oMost plants use a closed cooling system where warm water coming from

condenser is cooled and reused

oSmall plants use spray ponds and medium and large plants use cooling towers.

oCooling tower is a steel or concrete hyperbolic structure having a reservoir at the

base for storage of cooled water

oHeight of the cooling tower may be 150 m or so and diameter at the base is 150 m

Feed water heater

Advantages of heating water before feeding back to the boiler:-

a) Feed water heating improves overall plant efficiency.

b) The dissolved oxygen and carbon dioxide which would

otherwise cause boiler corrosion are removed in feed water

heater

c) Thermal stresses due to cold water entering the boiler drum

are avoided.

d) Quantity of steam produced by the boiler is increased.

e) Some other impurities carried by the steam and condensate,

due to corrosion of boiler and condenser are precipitated

outside the boiler.

Economiser

Flue gases coming out of the boiler carry lot of heat. An economiser extracts a

part of this heat from flue gases and uses it for heating feed water. This use of

economiser results in saving coal consumption and higher boiler efficiency

Economizer

Air preheater

After flue gases leave economiser, some further heat

can be extracted from them and used to heat

incoming heat. Cooling of flue gases by 20 degree

centigrade increases the plant efficiency by 1%.

Air preheaters may be of three types

Plate type

Tubular type

Regenerative type

Electricity by definition is electric current that is used as a power source!

This electric current is generated in a power plant, and then sent out

over a power grid to your homes, and ultimately to your power outlets.

GENERATION STATION

Bulk electrical power is produced by special plants known as

generating station (or) power plants.

To provide cheap, reliable and continous service

Importance of electrical energy 1. Convenient form

Ex. heater

2.Easy control

3.Greater flexibility

Definition of A Turbo Machine

Turbines are energy developing machines. Turbines convert fluid energy into

mechanical energy. The mechanical energy developed by the turbines is used

in running an electric generator, which is directly connected, to the shaft of the

electrical generator.

Earlier days method – wooden wheel

Overshot Wheel

Had very good efficiency

Could not handle large quantity of water

Undershot Wheel

Low Efficiency

Hydropower to Electric Power

Selection of site

• Location of Dam

• Choice of Dam

• Quantity of water available

• Accessibility of site (cost &type of land)

• Distance from the load center

Classification based on contraction • Runoff river plant without pondage

dam across river

low head

low capacity

• Runoff river plant with pondage

• Valley dam plant large storage capacity

Power plant is located at toe of the dam

• Diversion canal plant

• High Diversion canal plant

Sizes of Hydropower Plants

• Definitions may vary.

• Large plants : capacity >30 MW

• Small Plants : capacity b/w 100 kW to 30 MW

• Micro Plants : capacity up to 100 kW

How Hydropower Works!

• Hydrologic cycle

How Hydropower Works! (ctd…)

• Water from the reservoir flows due to gravity to drive the turbine.

• Turbine is connected to a generator.

• Power generated is transmitted over power lines.

Hydropower to Electric Power

Potential

Energy

Kinetic

Energy

Electrical

Energy

Mechanical

Energy

Electricity

How Hydropower Works

Water from the reservoir

flows due to gravity to

drive the turbine.

Turbine is connected to a

generator.

Power generated is

transmitted over power

lines.

General layout of Hydro-Power Plant

a) Reservoir

Reservoirs ensure supply of water through out the year, by storing water

during rainy season and supplying the same during dry season.

b) Dam

The function of the dam is to increase the reservoir capacity and to increase the

working head of the turbine.

c) Penstock

A pipe between dam and turbine is known as penstock. It will carry the water

from dam to turbine. Penstock is commonly made of steel pipes covered with

d) Surge tank/Forebay

When the rate of water flow through the penstock is suddenly decreased, the

pressure inside the penstock will increase suddenly due to water hammer

and thereby damage the penstock.

Surge tank/Forebay is constructed between the dam and turbine. It will act

as a pressure regulator during variable loads.

e) Turbine

Turbines convert the kinetic and potential energy of water into mechanical

energy to produce electric power.

f) Generator and Transformer

Electric generator converts mechanical energy into electrical energy. A step

up transformer will increase the voltage for loss free transmission.

Advantages of hydraulic power plants

Operating cost is very low

Less Maintenance cost and less manpower required

Pollution free

Quick to start and easy to synchronize

Can be used for irrigation and flood control

Long plant life.

Disadvantages of Hydraulic Power Plants

Initial cost of total plant is comparatively high

Power generation depends on availability of water

Cost of transmission is high since most of the plants are in remote areas

Project duration is long.

Advantages and Disadvantages of HPP

1) Hydraulic Efficiency – due to hydraulic losses

Power developed by the runner

Net power supplied at the turbine entrance

SI Unit: kW

Metric Unit : Horse Power/Water Horse Power (W.H.P)

2) Mechanical Efficiency – Due to mechanical losses ( bearing friction)

Power available at the turbine shaft (P)

Power developed by the runner

Efficiencies of Hydraulic Turbines

3) Volumetric Efficiency – due to amt of water slips directly to the tail race

Amount of water striking the runner

Amount of water supplied to the turbine

4) Overall Efficiency

Power available at the turbine shaft (P)

Net power supplied at the turbine entrance

Cont…

Classification of Turbines

Turbines are classified according to several considerations as indicated below.

i) Based on working principle

a) Impulse turbine

b) Reaction turbine

Impulse Turbine: (pressure less)

The pressure of liquid does not change while flowing through the rotor of the

machine. In Impulse Turbines pressure change occur only in the nozzles of

the machine.

One such example of impulse turbine is Pelton Wheel.

Reaction Turbine:

The pressure of liquid changes while it flows through the rotor of the

machine. The change in fluid velocity and reduction in its pressure causes

a reaction on the turbine blades; this is where from the name Reaction

Turbine may have been derived.

Francis and Kaplan Turbines fall in the category of Reaction Turbines.

Cont…

ii) Based on working media

a) Hydraulic turbine

b) Steam turbine

c) Gas turbine

d) Wind Turbine

iii) Based on head

Head is the elevation difference of reservoir water level and D/S water level.

a) Very High head turbine (500 m &above) Pelton Turbine

b) High head turbine ( 70-500 m) Francis Turbine (or )Pelton

b) Medium head turbine (15– 70 m) Kaplan (or) Francis Turbine

c) Low head turbine (Below 60 m) Kaplan Turbine

iv) Based on specific speed

Turbines can be classified based on Specific Speed. Specific speed is defined

as the speed in rpm of a geometrically similar turbine, which is identical in

shape, dimensions, blade angles and gate openings with the actual turbine

working under unit head and developing unit power. Specific speed is used to

compare the turbines and is denoted by Ns.

Specific speed Ns = N √P / H5/4

a) Low specific speed (8.5 – 30) - Pelton Turbine

b) Medium specific speed (50 – 340) - Francis Turbine

c) High specific speed (255 – 860) - Kaplan Turbine

Cont…

v) Based on disposition of turbine main shaft

a) Horizontal shaft

b) Vertical shaft

vi) Based on flow through the runner

a) Radial flow

1. Inward

2. Outward

b) Axial flow - Kaplan Turbine

c) Mixed flow - Francis Turbine

d) Tangential flow - Pelton Turbine

Cont…

Pelton Wheel Turbine

Design of Pelton Wheel Turbine

It has a circular disk with cup shaped blades/buckets,

Water jet emerging from a nozzle is tangential to the circumference of the

wheel.

Impulse Turbines

• Uses the velocity of the water to move the runner and discharges to atmospheric pressure.

• The water stream hits each bucket on the runner.

• High head, low flow applications.

• Types : Pelton turbine, Turgo turbine

Pelton Turbine

Turgo Turbine

Reaction

Turbines

• Combined action of pressure and moving water.

• Runner placed directly in the water stream flowing over the blades rather than striking each individually.

• Lower head and higher flows than compared with the impulse turbines.

Working Principle of Pelton Turbine

Water jets emerging strike the buckets at splitter.

Stream flow along the inner curve of the bucket and leave it in the direction

opposite to that of incoming jet.

The high pressure water can be obtained from any water body situated at some height or streams of water flowing down the hills.

The change in momentum (direction as well as speed) of water stream produces an impulse on the blades of the wheel of Pelton Turbine. This impulse generates the torque and rotation in the shaft of Pelton Turbine.

Horizontal shaft - Not more than 2 jets are used and Vertical shaft - Larger no. of jets (upto 6) are used.

Iron/Steel casing to prevent splashing of water and to lead water to the tail

Classification based on contraction • Runoff river plant without pondage

dam across river

low head

low capacity

• Runoff river plant with pondage

• Valley dam plant large storage capacity

Power plant is located at toe of the dam

• Diversion canal plant

• High Diversion canal plant

TECHNOLOGY

Technology

Hydropower

Technology

Impoundment Diversion Pumped

Storage

Impoundment facility

Dam Types

• Arch

• Gravity

• Buttress

• Embankment or Earth

Arch Dams

• Arch shape gives strength

• Less material (cheaper)

• Narrow sites

• Need strong abutments

Concrete Gravity Dams

• Weight holds dam in place

• Lots of concrete (expensive)

Buttress Dams

• Face is held up by a series of supports

• Flat or curved face

Dams Construction

Diversion Facility

• Doesn’t require dam

• Facility channels portion

of river through canal or

penstock

Pumped Storage

• During Storage, water

pumped from lower

reservoir to higher one.

• Water released back to

lower reservoir to generate

electricity.

Pumped Storage

• Operation : Two pools of Water

• Upper pool – impoundment

• Lower pool – natural lake, river

or storage reservoir

• Advantages :

– Production of peak power

– Can be built anywhere with

reliable supply of water

The Raccoon Mountain project

Sizes of Hydropower Plants

• Definitions may vary.

• Large plants : capacity >30 MW

• Small Plants : capacity b/w 100 kW to 30 MW

• Micro Plants : capacity up to 100 kW

Large Scale Hydropower plant

Small Scale Hydropower Plant

Micro Hydropower Plant

Micro Hydropower Systems

• Many creeks and rivers are permanent, i.e., they never dry up,

and these are the most suitable for micro-hydro power

production • Micro hydro turbine could be a waterwheel

• turbines : Pelton wheel (most common)

• Others : Turgo, Crossflow and various axial flow turbines

Generating Technologies

• Types of Hydro Turbines:

– Impulse turbines

• Pelton Wheel

• Cross Flow Turbines

– Reaction turbines

• Propeller Turbines : Bulb turbine, Straflo, Tube Turbine,

Kaplan Turbine

• Francis Turbines

• Kinetic Turbines

Impulse Turbines

• Uses the velocity of the water to move the runner and

discharges to atmospheric pressure.

• The water stream hits each bucket on the runner. • No suction downside, water flows out through turbine housing

after hitting.

• High head, low flow applications.

• Types : Pelton wheel, Cross Flow

Pelton Wheels

• Nozzles direct forceful

streams of water against a

series of spoon-shaped

buckets mounted around the

edge of a wheel.

• Each bucket reverses the

flow of water and this

impulse spins the turbine.

Pelton Wheels (continued…)

• Suited for high head, low

flow sites.

• The largest units can be up

to 200 MW.

• Can operate with heads as

small as 15 meters and as

high as 1,800 meters.

Cross Flow Turbines

• drum-shaped

• elongated, rectangular-

section nozzle directed

against curved vanes on a

cylindrically shaped runner

• “squirrel cage” blower

• water flows through the

blades twice

Cross Flow Turbines (continued…)

• First pass : water flows from the outside of the

blades to the inside

• Second pass : from the inside back out

• Larger water flows and lower heads than the

Pelton.

Reaction Turbines

• Combined action of pressure and moving

water.

• Runner placed directly in the water stream

flowing over the blades rather than striking

each individually.

• lower head and higher flows than compared

with the impulse turbines.

Propeller Hydropower Turbine

• Runner with three to six blades.

• Water contacts all of the blades constantly.

• Through the pipe, the pressure is constant

• Pitch of the blades - fixed or adjustable

• Scroll case, wicket gates, and a draft tube

• Types: Bulb turbine, Straflo, Tube turbine, Kaplan

Bulb Turbine

• The turbine and generator are a sealed unit placed directly in the water stream.

Others…

• Straflo : The generator is attached directly to the perimeter of

the turbine.

• Tube Turbine : The penstock bends just before or after the

runner, allowing a straight line connection to the generator

• Kaplan : Both the blades and the wicket gates are adjustable,

allowing for a wider range of operation

Kaplan Turbine

• The inlet is a scroll-shaped tube that wraps around the turbine's wicket gate.

• Water is directed tangentially, through the wicket gate, and spirals on to a propeller shaped runner, causing it to spin.

• The outlet is a specially shaped draft tube that helps decelerate the water and recover kinetic energy.

Francis Turbines

• The inlet is spiral shaped.

• Guide vanes direct the water

tangentially to the runner.

• This radial flow acts on the runner

vanes, causing the runner to spin.

• The guide vanes (or wicket gate)

may be adjustable to allow

efficient turbine operation for a

range of water flow conditions.

Francis Turbines (continued…)

• Best suited for sites with

high flows and low to

medium head.

• Efficiency of 90%.

• expensive to design,

manufacture and install,

but operate for decades.

Kinetic Energy Turbines

• Also called free-flow turbines.

• Kinetic energy of flowing water used rather than potential from the head.

• Operate in rivers, man-made channels, tidal waters, or ocean currents.

• Do not require the diversion of water.

• Kinetic systems do not require large civil works.

• Can use existing structures such as bridges, tailraces and channels.

Hydroelectric Power Plants in India

Baspa II Binwa

Continued …

Gaj Nathpa Jakri

Continued…

Rangit Sardar Sarovar

ENVIRONMENTAL IMPACT

Benefits…

• Environmental Benefits of Hydro

• No operational greenhouse gas emissions

• Savings (kg of CO2 per MWh of electricity):

– Coal 1000 kg

– Oil 800 kg

– Gas 400 kg

• No SO2 or NOX

• Non-environmental benefits

– flood control, irrigation, transportation, fisheries and

– tourism.

Disadvantages

• The loss of land under the reservoir.

• Interference with the transport of sediment by the dam.

• Problems associated with the reservoir.

– Climatic and seismic effects.

– Impact on aquatic ecosystems, flora and fauna.

Loss of land

• A large area is taken up in the form of a reservoir in case of large dams.

• This leads to inundation of fertile alluvial rich soil in the flood plains, forests and even mineral deposits and the potential drowning of archeological sites.

• Power per area ratio is evaluated to quantify this impact. Usually ratios lesser than 5 KW per hectare implies that the plant needs more land area than competing renewable resources. However this is only an empirical relation.

Methods to alleviate the negative

impact

• Creation of ecological reserves.

• Limiting dam construction to allow substantial free flowing

water.

• Building sluice gates and passes that help prevent fishes

getting trapped.

Favorable impact

• Enhanced fishing upstream.

• Opportunities for irrigated farming downstream.

• With the flooding of the forest habitat of the Tsetse fly, the

vector of this disease, the problem of Sleeping Sickness has

been substantially reduced.

Technological advancements

• Technology to mitigate the negative environmental impact.

– Construction of fish ways for the passage of fish

through, over, or around the project works of a

hydro power project, such as fish ladders, fish

locks, fish lifts and elevators, and similar physical

contrivances

– Building of screens, barriers, and similar devices

that operate to guide fish to a fish way

Continued…

• Evaluating a new generation of large turbines

– Capable of balancing environmental, technical, operational, and cost considerations

• Developing and demonstrating new tools

– to generate more electricity with less water and greater environmental benefits

– tools to improve how available water is used within hydropower units, plants, and river systems

• Studying the benefits, costs, and overall effectiveness of environmental mitigation practices

UNIT- II

Nuclear (Atomic) Power Plant

Working principle :

A nuclear power plant works in a similar way as a thermal

power plant. The difference between the two is in the fuel they

use to heat the water in the boiler(steam generator).

Inside a nuclear power station, energy is released by nuclear

fission in the core of the reactor.

1 kg of Uranium U235 can produce as much energy as the

burning of 4500 tonnes of high grade variety of coal or 2000

tonnes of oil.

Nuclear chain reaction

Neutrons released in fission trigger the fissions of other nuclei

proton

neutron

U-235 nucleus

Nuclear (Atomic) Power Plant…

Chain Reaction…

Uranium exists as an isotope in the form of U235 which is

unstable.

When the nucleus of an atom of Uranium is split, the neutrons

released hit other atoms and split them in turn. More energy is

released each time another atom splits. This is called a chain

reaction.

Nuclear fission:

Nuclear fission…

Nuclear fission: heavy nuclei split into two smaller parts in order to become more stable

proton

neutron

U-235 nucleus

Kr-92 nucleus

Ba-141 nucleus

energy

Nuclear Fission…

• It is a process of splitting up of nucleus of fissionable material like uranium into two or more fragments with release of enormous

amount of energy. •The nucleus of U235 is bombarded with high energy neutrons

U235+0n1 Ba 141+Kr92+2.50n

1+200 MeV energy.

• The neutrons produced are very fast and can be made to fission other nuclei of U235, thus setting up a chain reaction.

• Out of 2.5 neutrons released one neutron is used to sustain the chain reaction.

1 eV = 1.6X10-19 joule. 1 MeV = 106 eV

Nuclear fission…

U235 splits into two fragments (Ba141 &

K92) of approximately equal size.

About 2.5 neutrons are released. 1

neutron is used to sustain the chain

reaction. 0.9 neutrons is absorbed by

U238 and becomes Pu239. The remaining

0.6 neutrons escapes from the reactor.

The neutrons produced move at a very

high velocity of 1.5 x 107 m/sec and

fission other nucleus of U235. Thus

fission process and release of neutrons

take place continuously throughout the

remaining material.

A large amount of energy(200 Million

electron volts, Mev) is produced.

Note : Moderators are

provided to slow down the

neutrons from the high velocities

but not to absorb them.

Principal parts of a nuclear reactor:

Core : Here the nuclear fission process takes place.

Moderator : This reduces the speed of fast moving neutrons. Most moderators

are graphite, water or heavy water.

Principal parts of a nuclear reactor…

Control rods :

Coolant : They carry the intense heat generated. Water is used as a coolant,

some reactors use liquid sodium as a coolant.

Fuel : The fuel used for nuclear fission is U235 isotope.

Radiation shield : To protect the people working from radiation and

(thermal shielding) radiation fragments.

Control rods limit the number

of fuel atoms that can split.

They are made of boron or

cadmium which absorbs

neutrons

The chain reaction is not slowed down

a huge amount of energy is released very quickly

the rate of fission

increases rapidly

Nuclear bomb

Uncontrolled nuclear reaction

Nuclear reactors

Nuclear power plant: Rate of fission is controlled by artificial means to generate electricity

The Daya Bay

Nuclear Power

Station

Types of Nuclear power plant:

Main two types are :

* Pressurised Water Reactor (PWR)

* Boiling Water Reactor (BWR)

Pressurised Water Reactor

Heat is produced in the reactor due to

nuclear fission and there is a chain

reaction.

The heat generated in the reactor is

carried away by the coolant (water or

heavy water) circulated through the

The purpose of the pressure equalizer

is to maintain a constant pressure of 14

MN/m2. This enables water to carry

more heat from the reactor.

The purpose of the coolant pump is to

pump coolant water under pressure

into the reactor core.

Nuclear (Atomic) Power Plant… Pressurised Water Reactor

The steam generator is a heat exchanger

where the heat from the coolant is

transferred on to the water that circulates

through the steam generator. As the

water passes through the steam generator

it gets converted into steam.

The steam produced in the steam

generator is sent to the turbine. The

turbine blades rotate.

The turbine shaft is coupled to a

generator and electricity is produced.

After the steam performing the work on

the turbine blades by expansion, it comes

out of the turbine as wet steam. This is

converted back into water by circulating

cold water around the condenser tubes.

The feed pump pumps back the

condensed water into the steam

generator.

Schematic diagram of a nuclear power

plant with PWR

control rods

fuel rods

reactor pressure vessel

water (cool)

water (hot)

water (high pressure)

water (low pressure)

coolant out

coolant in steam condenser

steam (low pressure)

turbine

electric power

generator

steam (high pressure)

primary loop secondary loop

generator reactor

control rods

water (cool)

water (hot)

coolant out

turbine

electric power

generator

fuel rods They contain the nuclear fuel:

uranium (U-235)

They are surrounded by a

moderator (water or graphite) to

slow down the neutrons released.

control rods

water (cool)

water (hot)

coolant out

turbine

electric power

generator

fuel rods

They control the rate of reaction by

moving in and out of the reactor.

Move in: rate of reaction

Move out: rate of reaction

All are moved in: the reactor is

shut down

They are made of boron or

cadmium that can absorb neutrons.

generator

control rods

reactor pressure vessel water (high

pressure)

coolant out

fuel rods

The steam drives a turbine, which

turns the generator.

Electricity is produced by the

generator.

water (hot)

water (cool)

steam (low pressure) turbine

electric power

generator

control rods

fuel rods

water (cool)

water (hot)

coolant out

turbine

electric power

generator

Two separate water systems are used to avoid

radioactive substances to reach the turbine.

control rods

reactor pressure vessel water (high

pressure)

coolant out

turbine

electric power

fuel rods

The energy

released in

fissions heats up

the water around

the reactor.

The water in the

secondary loop

is boiled to

steam.

water (hot)

water (cool)

generator

Boiling Water Reactor

The water is circulated through the

reactor where it converts to water

steam mixture.

The steam gets collected above the

steam separator.

This steam is expanded in the turbine

which turns the turbine shaft.

The expanded steam coming out of the

turbine is condensed and is pumped

back as feed water by the feed water

pump into the reactor core.

Also the down coming recirculation

water from the steam separator is fed

back to the reactor core.

Steam power plant means any plant that uses steam to produce electricity.

E.g. Thermal and Nuclear power plants.

Advantages of Nuclear power plant:

Space required is less when compared with other power plants.

Nuclear power plant is the only source which can meet the increasing demand

of electricity at a reasonable cost.

A nuclear power plant uses much less fuel than a fossil-fuel plant.

1 metric tonne of uranium fuel = 3 million metric tonnes of coal = 12 million

barrels of oil.

Disadvantages of Nuclear power plant:

o Radioactive wastes must be disposed carefully, otherwise it will adversely

affect the health of workers and the environment as a whole.

o Maintenance cost of the plant is high.

Nuclear waste

They are highly radioactive

Many of them have very long half-lives.

Radioactive waste must be stored carefully.

Low level radioactive waste

cooling water pipes, radiation suits, etc.

stored in storage facilities

radioactivity will fall to a safe level after 10 to 50 years.

used nuclear fuel

highly radioactive

embedded in concrete and stored deep underground for several thousand years

High level radioactive waste

Nuclear fusion

Nuclear fusion: light nuclei fuse together to form a heavier nucleus

Nuclear fusion…

Nuclear fusion: light nuclei fuse together to form a heavier nucleus

proton

neutron

helium nucleus

neutron

energy

deuterium nucleus

tritium nucleus

H-2 + H-3 He-4 + n + energy

Videos and Animations

2. 9. Nuclear power station

3. 10. How a nuclear power plant

4. Nuclear Reactor

5. 11.Nuclear power –How it

6. How a pressurised water nuclear 12.

reactor works

7. 13. Nuclear power generator

14. Reactor components

1 nuclear fission.swf

2 nuclear react ions.sw f

3 nuclear reactor an activity.swf

5 nuclear reactor w orking.sw f

7-Nuclear pow er plant1.sw f

8 nuclear powerplant2.sw f

12 Nuclear pow er plant3.sw f

Thank You

UNIT- III

SUB-STATIONS

INTRODUCTION

The assembly of apparatus used to change some

characteristic(e.g. Voltage, a.c to d.c, frequency,

power factor etc) of electric supply is called a sub-

station

SITE SELECTION …..

• It should be located at the centre of gravity of

• It should be easily operated and maintained

• It should provide safe and reliable arrangement

• It should involve minimum capital cost

CLASSIFICATION OF SUB-STATIONS

Sub-stations

Service requirement

Constructional features

ACCORDING TO SERVICE REQUIREMENT

Transformer sub stations : these are used to change the voltage levels of

supply

switching sub stations: they simply perfome switching operations of power

Power factor sub stations: they improve the power factor of the system by

using synchronous condensers

Frequency sub stations: those sub stations which change supply

frequency

Converting sub stations: those sub stations which change a.c. power to

d.c. power

Industrial sub stations: those sub stations which supply power to industries

Substations are classified as……..

TRANSFORMER SUB-STATIONS Transformer substations are classified into 4 types these are……..

step up substation: the generation voltage is stepped up to high voltage

Primary grid substation: here the voltage level is step down to 66kv from

220kv for secondary transmission

Secondary substation: the voltage level is further step down to 11kv and

these substations are generally outdoor type

Distribution substation: the electric power from 11kv lines is delivered to

distribution substation. These are generally located near consumer

localities…

ACCORDING TO CONSTRUCTIONAL FEATURES

According to constructional features, the sub stations are classified as:

Indoor sub station: these substations can be installed for voltages up to 11kv

Outdoor sub station: for voltages beyond 66kv these type of sub stations can be

installed

Underground sub stations: in thickly populated areas, the space available is less

so we install these type of substations

Pole mounted substations: this is an outdoor substation with equipment installed

overhead on h-pole or 4 pole structure

INDOOR SUBSTATION…..

BLOCK DIAGRAM>>>>>>

pole mounted substation It is a schematic view of pole mounted substation……

POLE MOUNTED SUBSTATION……

UNDERGROUND SUBSTATION…… While designing a underground sub station the following points are to be

followed:

the size of substation should be minimum

There should be reasonable access for both equipment

There should be provision for emergency lights and protection against fire

There should be good ventilation

the transformers,switches,fuses should be air cooled to avoid bringing oil

into premises

Schematic view………

SYMBOLS FOR EQUIPMENT IN SUB STATIONS

EQUIPMENT IN A TRANSFORMER SUB STATION

BUS BARS: various incoming and out going circuits are connected to bus

bars.busbars receive power from incoming circuits and deliver power to out

going circuits.

Electric substations are the part of power systems and used for transferring

power from generating points to load centres.some of important components

are…

INSULATORS: insulators serve two purposes

1) they support conductors(busbars)

2) confine the current to the conductors

most commonly used material for manufacture of insulators is

porcelain.

ISOLATING SWITCHES: in sub stations it is often desired to disconnect a

part of system for general maintenance and repairs. this is accomplished by an

isolating switch or isolators.

Circuit breaker: circuit breaker is used for switching during

normal and abnormal conditions. it is used to interrupt short circuit

currents .there are many types of circuit breakers..

1) air blast circuit breaker.

2) oil circuit breaker

3) sf6 circuit breaker

power transformers: these are used to step down or step up a.c. voltages

and to transfer electrical power from one voltage level to another.

Current transformers: current transformer in essentially a

step up transformer which steps down the current to a

known ratio.

voltage transformer: it is essentially a step down transformer and steps down

the voltage to a known ratio.

metering and indicating instruments: there are several metering and indicating

instruments installed in a sub station to maintain watch over the circuit quantities.

in addition to these there may be following equipment in a substation.

1) fuses

2) carrier current equipment

3) sub station auxiliary supplies

BUS BAR ARRANGEMENTS IN A SUBSTATION

Single bus bar system…

Duplicate bus bar system…..

Key diagram of 66/11kv substation

Key diagram of 11/440v indoor substation

GAS INSULATED SUBSTATION

INTRODUCTION…

Gas Insulated substations use sulphur

hexa fluoride(SF6) gas which has

superior dielectric properties. Gas

insulated substations are used where

there is space for providing the

substation is expensive in large cities

and towns

TYPES OF GAS INSULATED

SUBSTATIONS Gas insulated substations are classified according to the

type of configurations as………..

isolated phase module

3-phase common modules

hybrid modules

Compact modules

Highly integrated systems

Isolated-phase module

The individual circuit elements such as a pole of a circuit breaker, a single pole

isolator, one phase assembly of a current transformer etc..are connected together

forms an isolated phase GIS module.

THREE PHASE COMMON MODULE

In this type of module a three phase bay is assembled using the desired number

of three phase elements. This reduces the total number of enclosures to one third.

HYBRID MODULES

It is the combination of isolated phase and three phase common elements is

used to achieve an optimal solution. Hybrid GIS technology has gained

popularity, specially in the medium and low voltage range

COMPACT MODULE

Compact GIS systems are essentially three phase common systems in

which the elements such as three phase circuit breaker, current

transformer etc…. Are placed

HIGHLY INTEGRATED SYSTEM

These are used in outdoor substations .highly integrated substations are

ready to install substations.

SINGLE LINE DIAGRAM

BUS BARS

The high voltage conductor made up of copper

or aluminum is centrally placed in a tabular

metal enclosure. In isolated phase GIS ,coaxial

bus bar are common

Constructional aspects of GIS……..

The main parts of GIS are…….

gas circuit

seals and gaskets

disconnectors

earth switch

Circuit breaker

Current transformer

Plug in joints

Enclosure

Expansion joints

Gas circuit : gas circuit has to maintain the dual purpose

(i.e. arc interruption and insulation). Gas circuit should

maintain the pressure throughout its life period so there

should be no leakages

SEALS AND GASKETS : seals and gaskets are used to

capture the SF6 gas lekages.these are manufactured with

nitrile rubber and viton. These serves sealing purpose

Disconnectors…..

Disconnectors or isolators are used for electrical

isolation of circuit parts.

They are slow acting and operating at off load.

Disconnectors must be carefully designed and tested

to be able to break small charging current without

generating too higher over voltage.

Circuit Breakers…….

Circuit breaker is a metal clad and uses SF6 gas for the purpose of

insulation and fault interruption. The circuit breaker is directly

connected to either current transformers or isolators

Earthing switch……

fast earth switch: these are used to protect the

circuit connected current transformer, voltage

transformer

Maintenance earth switch: these are used for

grounding the high voltage conductors during

maintenance

PLUG IN JOINTS: these are designed in such a way that

they can carry rated full load current uninterruptedly and can

carry heavy transient currents types of plug in joints are

Static joints

Quasi static joints

MAINTENANCE AND INSTALLATION

S.NO 145KV 170KV 245KV

Bay width (m) 1.5 2.0 2.0

2 Bay depth 3.3 3.35 3.4

3 Bay height 3.2 3.4 3.4

4 Floor area (sq.m)

4.95 6.7 6.8

5 Volume 15.84 22.78 23.12

6 Weight 3800 5000 5700

Advantages of GIS….

GIS have no risk for fire and explosion due to

leakage of oil.

They generate no noise and have no radio

interference.

The maintenance of GIS is free.

It offers solutions,

-Industrial areas where space and

pollution problems .

-Mountain areas where ice and snow are

major problems.

Disadvantages of GIS…….

Gas insulations tend to be much more

expensive than air insulated installations with

the same ratings.

Care should be taken that no dust particles

enter into the live compartments which results

in flash over.

When fault occurs internally the diagnosis of

the fault and rectifying takes very long time.

UNIT- IV

INTRODUCTION

• The electrical energy generated at generating stations

• It is Conveyed to the consumers through a network

of transmission and distribution system.

POWER SYSTEM

PRIMARY

GRID SS

SECONDARY

HT-CONSUMERS

DISTRIBUTION

SECONDARY

DISTRIBUTION

HT-CONSUMERS

VOLTAGES USED IN INDIA

• Generation : 3.3KV, 6.6KV, 11KV, 33KV

• Transmission : 110KV, 132KV, 220KV, 400KV

• High voltage distribution : 3.3KV, 6.6KV,11KV

• Low voltage distribution :

• AC : 400V between phases, 230V to Neutral

• DC : 3Wire, 2x220V.

DISTRIBUTION SYSTEM

• The conductor system by which Electrical energy is

conveyed from a bulk power source (sub-station) to the

consumer is called Distribution system.

Primary distribution

Secondary distribution

Distribution

DISTRIBUTION SYSTEMS

REQUIREMENTS OF GOOD DISTRIBUTION SYSTEM

• The declared consumer voltage should be within the prescribed limits i.e., + 5%

• High reliability

• Maximum efficiency

• Non overloading of distribution lines

• High insulation resistance of the system

• Economical

• The conductor system through which the power is

distributed between secondary transmission sub-station

to the primary distribution sub-station.

• Primary distribution voltages are 3.3KV, 6.6KV, 11KV

PRIMARY DISTRIBUTION SYSTEM

SECONDARY DISTRIBUTION SYSTEM

• The conductor system through which the power is distributed

between primary distribution sub-stations to the consumer.

• Secondary distribution voltages are - AC 400V line to line,

230V line to phase DC 3Wire, 2 x 220V.

Feeder A

C Feeder

Service mains

Service mains Service mains

Service mains

11KV/0.4KV

FEEDERS

• The conductors which connects substations to the areas

served by these stations.

• No tapings are taken from the feeders to feed the consumers

• Feeders are mainly designed on the basis of its current

carrying capacity

DISTRIBUTORS

• The conductors from which numerous tapings are taken for supplying the power to the consumers

• Current flowing through the distributor lines are not constant.

• Distributor lines are mainly designed on basis of

voltage drop

SERVICE MAINS

• The conductor which connect the consumer terminal to the

distributors.

Type of current

Construction

Service

No of wires

Scheme of connection

CLASSIFICATION OF DISTRIBUTION SYSTEMS

• The distribution systems are classified on the basis of

BASED ON TYPE OF CURRENT:

• A.C. distribution System

• D.C. distribution System

FEEDER

STATION

FEEDER

AC DISTRIBUTION

11KV/0.4KV

DISTRIBUTOR

FEEDER

STATION

FEEDER

DC DISTRIBUTION

DISTRIBUTOR

BASED ON CONSTRUCTION:

• Over head distribution system

• Under ground distribution system

11KV/0.4KV

OVER HEAD DISTRIBUTION SYSTEM

Ground level

BASED ON SERVICE:

• General Lighting and Power distribution

system

• Industrial Power distribution system

• Railways distribution system

• Street Lighting distribution system

BASED ON NO.OF WIRES:

• Two Wire distribution System

• Three Wire distribution System

• Four Wire Distribution System

BASED ON SCHEME OF CONNECTION:

• Radial distribution System

• Ring distribution System

• Parallel distribution system

• Inter connected distribution system

SS PRIMARY

RING DISTRIBUTION SYSTEM

CONNECTED

SYSTEM

11KV/0.4KV

FEEDER

LOADS DISTRIBUTOR

• In this system, separate feeder radiate from a single substation and feed the

distributors at one end only.

Radial system:

• RADIAL DISTRIBUTION SYSTEM

33/11KV

11KV/400V D.T/F

FEEDER

DISTRIBUTORS

FEEDER

Advantages of radial system

• Simple in construction

• Switching equipment is less

• Low investment cost

• Simple protective relaying

Disadvantages of radial system

• Lack of security of supply

• Over loading of the distributor end nearest to the feeding point

• Series voltage fluctuation affects the end consumer

• Not suitable for long distances

• It is a closed loop circuit from the substations bus bars, make a loop through the

area to be served and returns to the substation

• The distributors are tapped from different points through distribution transformer

SS PRIMARY

Advantages of ring distribution system:

• Less voltage fluctuations at consumer’s terminals

• More reliability as compared to radial system

• Easy maintenance

• Low voltage drop

• Both consumer is fed through two feeders

INTER CONNECTED DISTRIBUTION SYSTEM

• The feeder ring is energized by two or more generating

stations (or) substations. it is called inter connected system

CONNECTED

SYSTEM

11KV/0.4KV

FEEDER

LOADS DISTRIBUTOR

INTER CONNECTED DISTRIBUTION SYSTEM

Advantages:

• Increase in service stability

• More efficiency of the system

• Feeding any area during peak load period from more no. of generating stations is possible

COMPARISON BETWEEN RADIAL AND

RADIALDISTRRIBUTION

• More voltage drop

• Not reliable

• Not economical system

• Consumer is fed by a simple distributor

• No provision distributor for interconnect or

RING DISTRIBUTION

• Less voltage drop

• More reliability

• More economical

• Consumer in fed through two or more distributor

• Possibility of inter connection to rise the potential

TABLE NO.1

DISTRIBUTORS

• The conductors from which numerous tapings

are taken for supplying the power to the consumers is called

distributors

CLASSIFICATION OF DISTRIBUTORS

Distributor

Loading

Feeding

Concentrated loading

Uniformly distributed loading

At unequal

voltage

Fed at one end

Fed at both ends At equal

voltage

Fed at center

Fed at any point on ring

distributor Fig.1

CLASSIFICATION BASED ON LOADING

• Concentrated loading distributors

• Uniformly distributed loading distributors

CONCENTRATE LOADING OF DISTRIBUTOR

• The distributor is connected to the supply at one or both ends and loads are taken at different points along the length of the distributor.

I1 I2 I3 I4

F I1 r1

D C B A I2 r2 I3 r3

CONCENTRATED LOADING OF DISTRIBUTOR

UNIFORM DISRIBUTED LOADING DISTRIBUTOR

• The distributor is connected to the supply at one or

both ends.

• Loads are taken uniformly at different equal distant points

along the length of the distributor.

UNIFORM DISTRIBUTED LOADING

CLASSIFICATION BASED ON FEEDING ENDS

• Fed at one end only

• Fed at both ends with equal voltages

• Fed at both end with un equal voltages

• Fed at centre of the distributor

• Fed at any point on the ring distributor

DISTRIBUTER FED AT ONE END: • The distributor is connected to the supply at one end and loads

are taken at different points along the length of the distributor

• The current flowing in different sections of the distributor away from the feeding point goes on decreasing

• The voltages across the loads away from the feeding point goes on decreasing

• Continuity of supply is interrupted in case of fault on the feeder

DISTRIBUTER FED AT ONE END:

I1 I2 I3 I4

D C B A

I2 r2 I3 r3 I4 r4

DISTRIBUTOR FED AT BOTH ENDS:

• The distributor is connected to the supply mains at both ends . • The loads are taped-off at different points along the length.

• Continuity of supply is maintained even any fault occurs

on any section of the distributor

• Cross sectional area of the conductor required is lesser

than single fed distributor

• Continuity of supply is maintained even any fault occurs

on any fed point

ADVANTAGES

•The load voltage reaches maximum at the other feeding point

• The load voltage decreases as we move away from any

feeding point

DISADVANTAGE

• Middle point at minimum potential

• The distributor can be imagined to be cut into two at the

middle point

i i i i i i i i i i i i

Distributor Fed At Both Ends With Equal Voltages

i i i i i i

V1 = V2

i i i i i i

Distributor imagined to be cut into two equal parts

FED AT BOTH ENDS AT DIFFERENT VOLTAGES

DISTRIBUTER FED AT THE CENTRE

The distributor is fed at The centre through supply mains

• The distributor is equivalent to two single fed distributors with a common feeding point

• Distributor is equivalent to two single fed distributor of length equal to half of the total length

DISTRIBUTOR FED AT THE CENTRE :

RING MAIN DISTRIBUTOR FED AT ANY POINT

• The distributor is equivalent to a straight distributor with equal voltages.

• The distributor ring may be fed at one (or) more points

DISTRIBUTION RING

FEEDERS

RING DISTRIBUTOR FED AT ANY POINT

DISTRIBUTION

FEEDERS

AC DISTRIBUTION

• A.C distribution is widely used in the world

• A.C distribution used for domestic consumer supply

• A.C distribution is used for all industrial consumer supply

DISTRIBUTION

FEEDERS

DC DISTRIBUTION

w.r.t. VS

w.r.t VL 1

Power factor

vectorically simple arithmetic Addition & subtraction of V&I

R, L, C only R Drop in distributor

due to

AC DC CRITERIA

DIFFERENCES BETWEEN AC & DC

DISTRIBUTION TABLE.1

AC DISTRIBUTION VOLTAGES

• A.C –HT distribution voltage is 11KV

• A.C –LT 3 Phase distribution voltage is 400V

• A.C -LT 1 Phase distribution voltage is 230V

In AC distribution calculations, p.f. of various load currents have to be

considered.

The p.f. of load currents may be given W.r.t receiving or sending end

voltage, W.r.t to load voltage itself

Methods of solving AC distribution

MODEL PROBLEM

• Consider ac distributor ABC having load current I1 and I2 at B

and C with power factor cosФ1 & cosФ 2 respectively

• Let R1 +JX1 be the impedance of the section AB

and R2+JX2 be the impedance of the section BC

From figure Current flowing in section BC=I2 (ampere)

Voltage drop in section BC=I2Z2=I2(R2+JX2)

Voltage at B=voltage drop between BC +Voltage at C =Vc+I2(R2+JX2)

Current in section AB=I1+I2

Voltage at A=Voltage at B+Voltage drop in section AB VA=VB(I1+I2)(R1+jX1)

VECTOR DIAGRAMS W.R.T TO RECEIVING END Case 1:

Case 2: VECTOR DIAGRAMS W.R.T TO LOAD POINT

PROBLEM-1

• A single phase AC distributor is shown in figure.1. Calculate

the total voltage drop. The resistance and reactance are

0.25ohm and 0.125ohm for 1000m for to and fro.

B F A C

I1=100A

0.707 lag I3=80 A

0.8 Lag

I2=120A

100 m 150 m 150 m

GIVEN DATA

• Resistance of the distributor ,R=0.25 Ώ

• Reactance of the distributor ,X=0.125 Ώ

• Length of the distributor to and fro ,

L=1000m

SOLUTION

Resistance per metre = resistance of the distributor length of the distributor = R L = 0.25/1000 = 0.25×10-3Ώ

• Reactance per metre = reactance of the distributor

length of the distributor

=0.125/1000

=0.125 × 10-3 Ώ

• Impedance of the section FA,

Z = impedence per metre × length of the section

=Z/m × l

=(0.25 × 10-3+j 0.125 ×10-3) ×100

=(25+j12.5 )×10-3 Ώ

• Impedence of the section AB,

Z2= impedence per metre × length of the section

=(0.25 × 10-3+j 0.125 ×10-3) ×150

=(37.5+j18.75) 10-3 Ώ

• Impedance of the section BC,

Z3=(0.25 × 10-3+j 0.125 ×10-3) ×150

=(37.5+j18.75) 10-3 Ώ

• Current flowing in the section FA,

=I1+I2+I3

=100 45°+120 0°+80 36.86°

= (254.7-j118.7)Amp

• Current flowing in the section AB,

=I1+I2

=120 0°+80(0.8-j0.6)

=(184-j48)Amp

Current flowing in the section BC,

= 80(0.8 -j0.6)

= (64-j48)Amp

• Voltage drop in section FA,

=Current flowing in section FA ×impedance of the section FA

=(254.7-j118.7)(25+j12.5 )× 10-3

=(7.851+j 0.22) volt

• Voltage drop in the section AB,

=current flowing in the section AB× impedence of the section

=(184-j48) ×(37.5+j18.75) × 10-3

=(7.8+j1.65)Volt

Voltage drop in section BC=Current in section BC x

impedance of the section BC

=(64-j48) (37.5+ j 18.75)x 10-3

= 3.3-j0.6

• Total voltage drop in the distributor

=voltage drop in section FA+ voltage drop in section AB

+voltage drop in section BC

=(7.851+j0.22)+(7.8+j1.65)+(3.3-j0.6)

=18.951+j1.27

=19Volts

UNIT- V

ECONOMIC ASPECTS OF POWER GENERATION

Load Curves The curve showing the variation of load on the power station with respect to

(w.r.t) time is known as a load curve.

Importance of Load Curve

The Daily Load Curve gives the information of load on the power station during different running hours of the day.

The number of unit’s generation per day is found from the area under the daily Load Curve.

Average load is found from the Load Curve.

Average load= [Area (KWh) under daily load curve/24 hours]

The maximum demand of the station on that day is found from the highest point of the daily Load Curve.

The size and the number of generating units can be determined from the load curve.

This Load Curve helps to determine the operation schedule of the station. In that case when all the units or the less units needs to running is found.

Load Duration Curve

• When the load elements of a load curve are arranged in the order of descending magnitudes, the curve thus obtained is called a load duration curve.

Important Terms and Factors

• Connected load : • It is the sum of continuous ratings of all the equipments connected to supply

system.

• Maximum demand: • It is the greatest demand of load on the power station during a given period.

• Demand factor: • It is the ratio of maximum demand on the power station to its connected load.

• Diversity factor: • The ratio of the sum of individual maximum demands to the maximum demand on

power station is known as diversity factor

• Reserve Capacity • Plant Capacity – Maximum demand

• Average load: • The average of loads occurring on the power station in a given period (day or

month or year) is known as average load or average demand.

• Load factor: • The ratio of average load to the maximum demand during a given period is known

as load factor.

•Plant capacity factor: • It is the ratio of actual energy produced to the maximum possible

energy that could have been produced during a given period

• Plant use factor • It is ratio of kWh generated to the product of plant capacity and the number of

hours for which the plant was in operation

Suppose a plant having installed capacity of 20 MW produces annual output of

7·35 × 106 kWh and remains in operation for 2190 hours in a year. Then,

•Utilisation factor • it is the ratio of maximum demand to plant capacity.

• Base load • The unvarying load which occurs almost the whole day on the station is

known as base load.

• Peak load • The various peak demands of load over and above the base load of the station is

known as peak load.

UNIT- VI

Economics of Power Generation

The art of determining the per unit (i.e., one kWh) cost of production of electrical energy is known as economics of power generation.

This economics of power generation can be used two types

1. Interest: The cost of use of money is known as interest.

2. Depreciation: The decrease in the value of the power plant equipment and building due to constant use is known as depreciation.

Cost of electrical energy :

This cost of electrical energy can be divided in to 3 types

I. Fixed cost

II. Semi-fixed cost

III. Running or operating cost

I. Fixed cost: It is the cost which is independent of maximum demand and units generated.

II. Semi-fixed cost: It is the cost which depends upon maximum demand but is independent of units generated.

III. Running cost: It is the cost which depends only upon the number of units generated.

Expression for cost of electrical energy

The overall annual cost of electrical energy generated by a power station can be expressed in two farms.

(i) Three part form.

(ii) (ii) Two part form.

Three part form:

In this method, the overall annual cost of electrical energy generated is divided into three parts viz fixed cost, semi-fixed cost and running cost i.e.

Total annual cost of energy = Fixed cost + Semi-fixed cost + Running cost

= Constant + Proportional to max. demand + Proportional to kWh generated.

= Rs ( a + b kW + c kWh) where a = annual fixed cost independent of maximum demand

and energy output. It is on account of the costs mentioned in Art. 4.2.

b = constant which when multiplied by maximum kW demand on the station gives the annual semi-fixed cost.

c = a constant which when multiplied by kWh output per annum gives the annual running cost.

(ii) Two part form: It is sometimes convenient to give the annual

cost of energy in two part form. In this case, the annual cost of energy is divided into two parts viz., a fixed sum per kW of maximum demand plus a running charge per unit of energy. The expression for the annual cost of energy then becomes :

Total annual cost of energy = Rs. (A kW + B kWh) where A = a constant which when multiplied by maximum

kW demand on the station gives the annual cost of the first part.

B = a constant which when multiplied by the annual kWh generated gives the annual running cost. It is interesting to see here that two-part form is a simplification of three-part form.

TARRIF

The rate at which electrical energy is supplied to a consumer is known as tariff.

Objectives of tariff:

(i) Recovery of cost of producing electrical energy at the power station.

(ii) (ii) Recovery of cost on the capital investment in transmission and distribution systems.

(iii) (iii) Recovery of cost of operation and maintenance of supply of electrical energy e.g., metering equipment, billing etc.

(iv) (iv) A suitable profit on the capital investment.

Desirable characteristics of a tariff

(i) Proper return :

The tariff should be such that it ensures the proper return from each consumer. In other words, the total receipts from the consumers must be equal to the cost of producing and supplying electrical energy plus reasonable profit. This will enable the electric supply company to ensure continuous and reliable service to the consumers.

(ii) Fairness : The tariff must be fair so that different types of consumers are satisfied

with the rate of charge of electrical energy. Thus a big consumer should be charged at a lower rate than a small consumer. It is because increased energy consumption spreads the fixed charges over a greater number of units, thus reducing the overall cost of producing electrical energy. Similarly, a consumer whose load conditions do not deviate much from the ideal (i.e., nonvariable) should be charged at a lower* rate than the one whose load conditions change appreciably from the ideal.

(iii) Simplicity :

The tariff should be simple so that an ordinary consumer can easily understand it. A complicated tariff may cause an opposition from the public which is generally distrustful of supply companies.

(iv) Reasonable profit :

The profit element in the tariff should be reasonable. An electric supply company is a public utility company and generally enjoys the benefits of monopoly. Therefore, the investment is relatively safe due to non-competition in the market. This calls for the profit to be restricted to 8% or so per annum.

(v) Attractive :

The tariff should be attractive so that a large number of consumers are encouraged to use electrical energy. Efforts should be made to fix the tariff in such a way so that consumers can pay easily.

Types of tariff Simple tariff:

When there is a fixed rate per unit of energy consumed, it is called a simple tariff or uniform rate tariff.

Disadvantages:

(i) There is no discrimination between different types of consumers since every consumer has to pay equitably for the fixed* charges.

(ii) The cost per unit delivered is high.

(iii) It does not encourage the use of electricity.

Flat rate tariff:

When different types of consumers are charged at different uniform per unit rates, it is called a flat rate tariff.

Disadvantages:

(i) Since the flat rate tariff varies according to the way the supply is used,

separate meters are required for lighting load, power load etc. This makes the application of such a tariff expensive and complicated.

(ii) A particular class of consumers is charged at the same rate irrespective of the magnitude of energy consumed. However, a big consumer should be charged at a lower rate as in his case the fixed charges per unit are reduced.

Block rate tariff: When a given block of energy is charged at a

specified rate and the succeeding blocks of energy are charged at progressively reduced rates, it is called a block rate tariff.

Two-part tariff: When the rate of electrical energy is charged on the

basis of maximum demand of the consumer and the units consumed, it is called a two-part tariff.

Total charges = Rs (b × kW + c × kWh) where, b = charge per kW of maximum demand c = charge per kWh of energy consumed This type of

tariff is mostly applicable to industrial consumers who have appreciable maximum demand.

Advantages (i) It is easily understood by the consumers.

(ii) It recovers the fixed charges which depend upon the maximum demand of the consumer but are independent of the units consumed. Disadvantages

(i) The consumer has to pay the fixed charges irrespective of the fact whether he has consumed or not consumed the electrical energy.

(ii) (ii) There is always error in assessing the maximum demand of the consumer.

Maximum demand tariff

it is similar to two-part tariff with the only difference that the maximum demand is actually measured by installing maximum demand meter in the premises of the consumer. This removes the objection of two-part tariff where the maximum demand is assessed merely on the basis of the rateable value.

Power factor tariff

The tariff in which power factor of the consumer’s load is taken into consideration is known as power factor tariff.

a. kVA maximum demand tariff

b. Sliding scale tariff

c. kW and kVAR tariff

Three-part tariff: When the total charge to be made from the consumer is

split into three parts viz., fixed charge, semi-fixed charge and running charge, it is known as a three-part tariff. i.e.,

Total charge = Rs (a + b × kW + c × kWh)

where a = fixed charge made during each billing period. It includes interest and depreciation on the cost of secondary distribution and labour cost of collecting revenues,

b = charge per kW of maximum demand,

c = charge per kWh of energy consumed.

unit- i - rgmcet · amount of super heater surface installed, as well as the rating of the boiler....

Documents

hired hand super saver heater manual

rgmcet rajeev gandhi memorial college of engg. and tech

heater cores heater cores heater cores2017 mei corporation...

imia wg paper 95(16) supercritical boilers · pdf file2.1...

unit heater kbp · #c4017 super heater 10-13 (800) 322-4707...

indus heaters · sprue coil heater coil heater for plastic...

digital communication course file - rgmcet | group · ·...

classic super lite travel trailers & fifth wheels€¦ ·...

super heater trouble shooting report at a hi plant by kkp

final technical report project title: · pdf fileproject...

cixi xinlun electrical appliance co., ltd. · 2017. 12....

economical heater fueleconomical heater fuel

design matters when e choosing a heater for super plastic...

master of business administration - rgmcet

power system protection - rgmcet | group · power system...

syllabus insp.of boiler.pdf · in boiler plant. boilers...

detailed project report on whrs in...

future perfect! · storage water heater instant water...

4801-1015 - super-saver xltm heater · 2 4801-1015...

j |p |s |t jornal...