1-3 Energy & Power Fundamentals of Electrical Power Engg 9-9-13

7/27/2019 1-3 Energy & Power Fundamentals of Electrical Power Engg 9-9-13

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Fundamentals

ofElectric PowerSystems


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Energy Sources


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The study ofElectric Power SystemsIs concerned withThe Generation,Transmission,Distribution andUtilization of ElectricPower.Generation involves theConversion of energyFrom a non-ElectricalForm such as Thermal,Hydraulic, Solar, or WindOr Tidal energyInto electrical energy.

It is thereforeAppropriate to beginWith a discussion ofEnergy.


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Fundamentals of

Electric Power SystemsEnergy & Power


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Importance of Electrical Energy


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Work

If you push a box with a force ofonenewton for a distance ofone meter, you

have done exactly one joule of work.


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Work ( when force is parallel to distance)

W = F x dDistance (m)

Force (N)

Work (joules)


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10.2 Work (force at angle to distance)

W = Fd cos (q)

Distance (m)

Force (N)

Work (joules) Angle


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Energy & Power Let a force Fbe applied to a mass so as to

move the mass through a linear displacementd in the direction of F, then the work done bythe force is W=Fd .. (1.1)

If the displacement is not in the direction of F,then the work done is the product of thedisplacement and the component of the forcealong the displacement, that is,

W=Fd.Cos .. (1.2)

where is the angle Fmakes with d.


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Work & Energy

Work is measured in joules (J). From 1.1, one

joule is the work done by a force of one

newton in moving a body through a distant of

one meter in the direction of the force:

1j=1N.m

Energy of a body is its capacity to do work.

Energy has the same unit as work.

For electrical energy, the Fundamental unit is

the Watt-second. Where 1W.s=1J . (1.3)


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K.Wh So, Electrical Energy in Watt-sec (or Joules)

= Voltage in volts x Current in amperes x Time inseconds

Joules or Watt-sec is a very small unit of

electricity for practical purposes In practice, & most commonly, electrical

energy is measured in bigger units, viz watt-hour or kilowatt-hours (kWh):

1 watt-hour =1 watt x 1hr=1 wattx3600 sec= 3600 watt-sec

1kWh= 1kwx1hr= 1000 wattx3600sec= 36x10 5 watt-sec= 3.6x10 6 J .. (1.4)


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Kinetic Energy & Potential Energy A body possesses KE by virtue of its motion, such

that a object of mass M (kgs) moving with a

velocity v (m/s) has

KE = Mv2(in Joules) . (1.5)

A body possesses PE by virtue of its position.

Gravitational PE results from an objects position

in a gravitational field. A body of mass M (Kgs) at

a height h(m) above earths surface has PE=Mgh (in joules) . (1.6)

Where g is acceleration due to gravity (m/s)


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Work done against gravity

W =mghHeight object raised (m)

Gravity (m/sec2)

Work (joules)

Mass (g)


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Heat

Heat is a form of energy which produces the

sensation of warmth. The unit of heat is calorie,

British Thermal Unit (BTU), and Centigrate Heat

Units (CHU) on various systems. Calorie: it is the amount of heat required to raise

the temperature of 1gm of water through 1C,

1Calorie= 1gm of water x 1C= 4.186 J (1.7)


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Thermal Energy

Sometimes a bigger unit namely kilocalorie isused. A Kilocalorie is the amount of heat

required to raise the temperature of 1kg of

water by 1C.

1 Kilocalorie= 1kg x 1C=1000gm x 1C= 1000 Calories

Yet another unit of thermal energy is Btu,

related to Joule and Calorie as

1 Btu = 1 lb x 1F=1.055x103 J = 0.252x103 cal (1.8) 1 CHU= 1 lbx1C


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Quad

Joule and calorie are relatively small units.Thermal and electric energy are expressed in

Btu or kWh, or MWh.

A still larger unit of energy is quad=( Quadrillion British thermal units)

1 quad = 1015 Btu = 1.055x 1018 J

Some authors define 1 quad as 1018 Btu


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Power Power is defined as the rate at which work is

done. Power is the time rate of change of

energy. Thus instantaneous power

p= dU/dt =dw/dt, where U is work & wis energy.

SI unit of power is the watt (W), and 1 watt is

equal to 1 joule/s

The power ratings (outputs) of electric motors

are expressed in horsepower (hp), where

1 hp= 745.7 W


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Major Energy Sources Fossil fuels---coal, petrolium, and natural gas ---

are major sources of energy. Solar radiation isanother major source of energy on earth, whichmay be obtained either directly as interceptedsolar radiation or indirectly as Wind andhydropower.

Other significant forms of energy are tidal energy,and nuclear energy.

Turbine-type wind energy generators transformthe KE of the wind into rotary shaft movementand in turn, into electrical energy


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Power extracted from wind is

P =2.46x10-3 D2 u2 (in watts) where D is theblade diameter in ft., and u , wind velocity in mph.

In Hydropower conversion the PE of a mass of

water at a hydraulic head is converted into the

KE of a hydraulic turbine that drives an electric

generator.

In general hydropower developed is

P=[0.736/75]Qwh kW

=p t g


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Tidal Energy is obtained by closing off a bay

with a dam, allowing it to fill during periods of

high tide, and recovering the energy as it

empties during periods of low tide. For a max.

tidal Head (m), the avg tidal power obtained

per unit area of tidal bay is given byPav= 0.219H2 in MW /Sq.km


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Operational Factors Demand Factor=[Max.Demand]/connected Load

Load Factor=Avg. Demand/Max.Demand

Load Factor can be defined for a period such as

daily, monthly or annual.

Diversity Factor=Sum of individual consumers

max. Demand/Maximum Demand on Station

Plant Capacity Factor=Avg Demand/Installed Cap. Plant use factor= actual energy produced/[Plant

CapacityxHours the plant has been in operation].


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TARIFFs


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Electrical energy is most useful form of energy because it can be most conveniently

transformed into other forms of energy like heat light, mechanical energy that we

require in our day to day life.

But electricity is not readily available and is required to be produced (generated) in a

factory called power station.

Like any other manufacturing process, the production (generation) of electricity alsoneed some cost to be incurred - Plants and Equipment, Inputs (water, fuel etc.), Ash

smoke disposal systems, Personnel

Cost of Transmission and Distribution to the large number of consumers of various

categories (viz. domestic, commercial, industrial, agricultural etc.)

All these costs when added together constitutes the total cost of electricity which in

the consumers have to share according to the quantum of electricity consumed

taking into account the nature and time of use of electricity by each category of

consumers.

INTRODUCTION


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Tariffs (Contd.) The tariff for the consumer is fixed based on

Fixed costs incurred during generation,transmission and distribution incldg cost of plant,bldg, depreciation , salaries etc. and does notdepend upon no of units generated.

Operational costs ( also called variable costs orrunning units) and depends on the unitsgenerated. Commonly use Tariffs are:

i. Flat Rate Tariff

ii. Block Rate Tariff

iii. Two part Tariff

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1-3 Energy & Power Fundamentals of Electrical Power Engg 9-9-13