Cooperative Living June 2015 - 25

T'S YOUR BUSINESS by Tom Tate, Contributing Writer
Transformers,
Line Loss and
Home Generator
Connections
I
f we were to ask you to describe your
co-op's electric distribution system, you
might say, " Poles, wires and those
round grey things. "
Round grey things? That is often the
description given for transformers, those
pieces of equipment that are crucial in
converting electricity to a voltage that is
safe for use in homes and businesses.
So, how do they work? First off, transformers
are nothing like those creations of
the silver screen. They don't transform from
vehicles to incredible combat robots.
Instead, they transform the voltage of the
electricity that passes through them.
Time for a little electric system 101.
Electricity loses voltage as it is transmitted
due to the resistance in wires and
other components. As a result, higher
voltages are used to offset " line losses, "
as we call them.
It all starts at the power plant. There,
generators produce electricity at very
high voltages and use transformers to
step-up this voltage, often to 350,000
volts or more. Since the power plants are
far away, these voltages are necessary
to survive the trip over the system to where
it is needed.
Transmission lines connect to substations
brimming with transformers and other
control gear. Here is where the transformers
step-down the voltage to safer, more
manageable levels. Depending upon the
distance involved to the furthest member
and the amount of load served, distribution
voltages can range from 7,200 to
24,900 volts. A couple more step-downs
and the electricity arrives at your home at
440 volts. This is quite different from the
original voltage.
June 2015/www.co-opliving.com
transformers, they all work in the same
manner. Transformers have two sides: a
high-voltage side and a low-voltage side. In
normal operation, electricity flows into the
transformer on the high-voltage side, where
it goes into a coil of wire usually wound
around an iron core. As the electricity flows
through this coil, it creates a magnetic field
that " induces " a voltage in the other coil.
Here is where the magic (aka physics) of
Time for a little electric
system 101. Electricity loses
voltage as it is transmitted
due to the resistance in wires
and other components. As a
result, higher voltages are
used to offset " line losses, "
as we call them. It all starts
at the power plant. There,
generators produce electricity
at very high voltages and
use transformers to step-up
this voltage, often to
350,000 volts or more. Since
the power plants are far
away, these voltages are
necessary to survive the trip
over the system to where it
is needed.
different number of turns. The greater the
number of turns, the higher the voltage. The
coil on the high side will have more turns
than the one on the low side. As a result,
the voltage induced on the low side is less.
Then transformation occurs.
Transformers aren't just limited to utility
use. They can be found everywhere in our
daily lives, even if not so obvious as those
on your co-op's system. The best example is
the charger that all cellphones and many
other electrical devices use. These small
cousins of utility transformers basically perform
the same function. Charging your cellphone
with 120 volts will fry it instantly. So,
the charger converts the voltage to a more
tolerable 5 volts or so. Take a moment to
look around your home and see just how
many of these miniature transformers you
have. You might be surprised!
It is important to note that transformers
work in both directions. Electricity flowing in
on the low side is stepped up to the voltage
of the high side. This is why your co-op
works hard to educate members on proper
connection and use of home standby generators.
A generator feeding 220 volts into
a residential transformer will produce whatever
voltage the transformer is rated for on
the other side, creating a deadly risk for
our line crews and your neighbors. So
please, connect your generators according
to the manufacturer's recommendations. Or
give your co-op a call for advice. It's
always best to be safe. 
Source: NRECA, www.nreca.coop
Tom Tate writes on cooperative issues for the National
Rural Electric Cooperative Association, the Arlington,
Va.-based service arm of the nation's 900-plus consumer-owned,
not-for-profit electric cooperatives.
23
LEISURETIME70/ISTOCK/THINKSTOCK
http://www.nreca.coop
Cooperative Living June 2015

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