Electrical Energy
Transfer
The Power Grid
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It involves a lot more than just flipping a
switch or plugging something into an outlet!
 If you have ever “lost “ power, you have been
reminded of how much you rely on electricity!
 Electricity was first used to illuminate a street and
a business in 1886! It was a few more years before
scientists figured out how to distribute it over a
distance and safely into homes.
 Think about how far people have come in less
than 120 years.
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Energy- the ability to make things move or
change
Fossil Fuel- a nonrenewable source of energy
that formed from the remains of organisms
that died millions of years ago
Electrical Energy- the energy of moving
electric charges
Electric Current- the rate at which charges
pass a given point
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Conductor-a material in which electric charges can
move easily
Insulator-a material in which electric charges
cannot move easily
Electric Circuit- a closed path through which
electricity can flow
Series Circuit- a circuit in which all parts are
connected in a single loop; charges must flow
through each part of the circuit
Parallel Circuit- a circuit in which loads are
connected side by side; charges have more than one
path on which they can travel
Voltage- the pressure that causes electrons to flow.
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 Current- The flow of electrons through a conductor (similar to water through
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a pipe).
Watt (W)- a unit of electrical power. Electrical power measured in Watts is
equal to the voltage times the current. (Kilowatt= (kW)= 1000 Watts)
Joule (J)- A joule is a measurement of electrical energy. 1 joule is equal to 1
watt of power for 1 second of time (watts x time = joules).
Generator-a machine that converts mechanical energy into electrical energy
Transformer-a device that increases or decreases electric voltage
Power Grid- a system of wires, transformers, and other devices that carry
electric current from power plants to individual users
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Energy is the ability to
make things move or
change. It comes in many
forms including light,
sound, heat, mechanical
energy, and electricity.
Electrical energy, or
electricity, is the energy of
moving electric charges.
Electricity can move
through objects that are
good conductors.
 A conductor is a material
that electrical energy can
flow through easily.
 Metals are examples of
good conductors because
of their properties.
 What are the properties of
metals?
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Non-metals are not
good conductors of
electricity.
 They are good
insulators. Insulators
are materials that
electrical energy does
not move through
easily.
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An electric current is a
flow of charges
particles through a
conductor (like a
metal). The current
must have a pathway
through which it can
move (like wires).
 The pathway is known
as an electric circuit.
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Simple circuits are
closed loops that
current can flow
though. They provide a
return path for the
current.
 Simple circuits consist
of an energy source, an
electrical device (load),
a switch, and wires.
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Circuits run on electrical energy from a
voltage source.
Voltage is the electrical energy available for
moving a charge.
Batteries are a common source of electrical
energy in wireless devices.
Electrical energy used
in most homes comes
from a power plant.
 The power plant
produces electricity
from other sources.
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 Fossil fuels
 Hydroelectric power
 Nuclear power
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Electricity produced in power plants must be
transported to homes and businesses
through a power grid.
A power grid is a system of wires,
transformers and other devices that carry
electric current from power plant to
individual users.
The grid also changes voltages of the current
it carries.
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Key components of a
power grid include:
 Power plant (generator)
 Overhead wires or
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transmission cables
Towers
Transformers
Substations
Junction boxes
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Generators change mechanical energy into
electrical energy.
Substations are small plots of land that contain
devices to regulate and continue the flow of
electricity.
Transformers increase or decrease the amount of
voltage.
Power lines enable the electricity to pass over great
distances to reach homes and businesses.
Junction boxes provide a way to redirect the source
of electricity to multiple places within a home or
business
The power plant!
Imagine this is the Jack
Watson plant… our
extension of Mississippi
Power. The majority of
power plants (like Jack
Watson) use coal as a
source of energy. The coal
is burned to heat water.
The heated water creates
steam. The steam turns
the turbine which turns
the generator which
creates the electricity that
is sent out of the plant.
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The electricity produced at the power plant is 3phase AC power. This means they are producing 3
different phases of AC power at the same time
offset at 120 degrees. It would look like this:
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Your home only uses 1 phase. So why do they
produce 3 phases? 3 x 120o =360o (a circle). This
means that there is always a current at peak
performance and never a slump in energy
production.
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From the power plant, electricity is sent to a
“step-up” transformer.
 Because it takes a lot of energy to send electricity
out to homes and businesses, the power behind it
(the volts) have to be “stepped-up” (or increased)
so it can make the trip.
A step-up
transformer
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After leaving the step-up transformer, the
electricity will travel along wires attached to
power poles. There are two main types of
power poles:
High voltage
you see these
close to plants,
or anywhere
the electricity
being
transmitted a
longer
distance.
Low voltage
You typically see
these in
neighborhoods ,
along streets or
highways…
anywhere with
places
reasonably close
together.
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We stepped-up the power behind the
electricity so it could travel, that power needs
to be taken back down before it enters your
house. This usually happens at a substation.
At the substation, the
power goes from
“transmission” to
“distribution”. It is taken
down to safe levels and
sent in different directions.
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The substation has a “bus”. It may not look
anything like the bus you ride on, it does
pretty much the same job. It sends the
electricity where it needs to go.
Notice all of the wires
going in many
different directions….
Anyone want some
power?
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Even though the power behind the electricity has been
“stepped-down” by the time it is traveling on the wires
down your street, it is still about 7,200 volts. The
electricity has to be stepped-down again because your
house runs on 120-240 volts.
You may have noticed that every few
power poles on your street have
something that looks like this on them.
This is another type of transformer that
takes the electricity in the wire down to a
safe level before it enters your home.
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Electricity generated at a
power plant must travel
long distances through a
power grid to reach its
destination. The current
follows a specific flow
through the grid.
First, a generator will send
the current to a step up
transformer. The
transformer will increase
the voltage of the
electricity to carry it
through wires to a
substation.
A substation houses
groups of transformers
which will increase or
decrease electric
voltage as necessary.
 The current will then
flow through wires to
step down
transformers which will
alter the voltage of the
current before it enters
homes and business,
traveling through a
junction box to the
outlet.
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In some areas of the country, other forms of
energy are utilized to create electricity.
Examples of renewable energy sources that
can be used are:
 Solar energy
 Hydroelectric energy
 Hydrothermic energy
Wind energy
If these alternate forms of energy produce enough
power to create an abundance of electricity in a
particular area, then the “extra” electricity can be
added to the existing power grid.
 In Mississippi, several businesses help to service the
power grid by maintaining and operating the power
grid.
 Kuhlman Electric Corporation in Crystal Springs is a
major supplier of transformers.
 Howard Industries, of Laurel and Ellisville,
Mississippi also supply equipment for the grid.
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