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Steam
Most steam-electric power plants burn fossil fuels--oil,
natural gas or coal--to change water into steam. Some
are using the atom, whereby the fuel-burning furnace is
replaced with a nuclear reactor. Splitting of atoms in
the reactor creates the necessary heat. Otherwise, nuclear
and fossil fuel plants operate in the same manner. Three
of Dairyland's four generating stations are coal-fired
steam plants.
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Fossil
Fuels
Fuel is burned in the boiler. Water, circulating through
the boiler, absorbs the heat and changes to steam. Pressure
of steam against the turbine blades spins the shaft. This
turns the generator, which produces electricity. Used steam,
cooled by the condenser, is changed back into water for
reuse in the boiler. Cool water to condense the steam is
drawn from the river or bay where the plant is located.
Electricity then goes to a transformer, which raises the
voltage for transmission.
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Nuclear
Heat is created by controlled fission of nuclear fuel in
the reactor. Water, under pressure to prevent it from boiling,
is circulated through the reactor, removing heat. Heated
water leaves the reactor and passes to the steam generator.
Here, the water from the reactor gives up heat to a second
separate system where water, not under as much pressure,
does boil, producing steam. Pressure of the steam turns
the turbine and, from this point, the nuclear plant operates
the same as a conventional plant.
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Combustion
Gases
Gas turbine burns either natural gas or low-sulfur oil.
Air is compressed and discharged into combustion chambers.
Fuel is added, mixed with air and burned. High pressure
combustion gases are formed and flow to the turbine. Pressure
rotates the turbine which turns an electric generator.
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Water
Millions of tons of water are needed to run a hydroelectric
plant. Water, which is held in a reservoir or lake behind
a dam, must be higher than the power plant so it can fall
with enough force to turn the huge steel blades of the turbine.
From the reservoir, water plunges down through large gates
or a long pipe (penstock) to the turbine. The spinning turbine
drives the shaft which turns the generator, producing electricity.
Dairyland owns the Flambeau Hydroelectric Station at Ladysmith,
Wis.
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Transmission
Lines
The high voltage electric current travels through thick
wires called transmission lines. Tall transmission towers
keep the transmission lines high above the ground. Insulators
made of glass or porcelain are used to prevent the electricity
from leaving the transmission lines and traveling through
the transmission towers which could cause damage and injury.
Transmission lines carry the electric current from the power
plant to where it is needed. A second set of wires is used
to carry the current back to the generator. These wires
are there because electric current travels in a closed circuit.
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High-Voltage
Substations
High-voltage substations are places where very high voltages
are reduced to lower levels. High-voltage power lines enter
and leave the transformer through large insulators. These
insulators are used to keep the high voltages away from
the metal tank containing the transformer coils. Oil flows
around the coils to keep them cool. Factories and other
large industrial plants may need high voltage to operate
heavy machinery. Medium voltage substations are designed
to further reduce the voltage for use in facilities that
do not need the higher voltages.
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Step-Down
Transformers
The electricity now travels from the substations to transformers
in your neighborhood. These transformers, called "Step-Down
Transformers," lower the voltage still further to make
the voltage safe for ordinary use in your home. These step-down
transformers are often located at the top of the poles which
carry electrical wires or on concrete pads.
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Electrical
Wires
Most electrical wires are above ground. They are supported
by tall wooden poles which may also support telephone wires
as well as street lights. Wires in cities may run through
underground cables. On some poles, near the top, are large
metal boxes which are the poles' transformers. Inside these
transformers are coils of wire which help reduce the voltage
to 120/240 volts which then can be used safely in homes.
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The
Electric Meter
Where the wires enter your home there is an electric meter.
The meter is used to measure the amount of electricity that
you use.
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