Christopher D. Wyckoff, Glen H. Hetzel
Virginia Cooperative Extension
Introduction
What
Can You Do?
What
Else Can You Do?
What
to Do In Case of An Accident
"Shocking
Statistics"
- There
are approximately 290 accidental electrocutions each
year.
- An
additional 800 people die in fires caused by faulty
electrical systems every year.
- Thousands
are shocked and burned as the result of accidental
contact with electricity every year.
- An
estimated $1.2 billion in property damage occurs each
year due to faulty use of electricity.
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Electricity,
or electric current, is the flow of electrons from one atom
to another in any material. Materials that allow electricity
to flow easily are called conductors. Most metals, such as
copper and aluminum, make good conductors of electricity.
Insulators are materials that do not allow electricity to
flow through them. Good examples of insulators are glass,
plastic, and rubber. Unfortunately, our bodies can allow current
to pass through them, causing anywhere from a mild tingling
sensation to cardiac arrest and burning.
There
are many ways in which electrical accidents happen. Hazards
result from the degradation of electrical wire insulation
due to rodents, weathering, or normal wear, improper wiring,
improper wire size or type, and corrosion of electrical connections,
for example. In addition to these normal hazards, agricultural
workers are particularly subject to the hazards of electricity
because tall equipment, such as grain augers, combines, and
raised dump truck beds can become entangled in overhead power
lines. Accidents have also occurred with overhead power lines
when moving irrigation pipe. Agricultural buildings are subject
to dusty, moist and corrosive environments, making them especially
troublesome when using electricity. Electricity was the seventh
largest cause of deaths on farms in 1988, and causes unknown
amounts of property and livestock loss every year. Fortunately,
there are several devices and methods that can be employed
to protect yourself, your animals, and your property.
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There
are four kinds of electrical safety devices and features that
you should be aware of. These are fuses and circuit breakers,
GFCI's, grounding, and polarization.
The
most common form of electrical protection is the fuse or circuit
breaker. These are devices that are designed to protect the
electrical system from too much current. These devices, when
used properly, work well to protect equipment and prevent electrical
fires due to overloads on the electrical system. They do not,
however, protect an individual from electrical shock. Fifteen
amps, which is typically the smallest size breaker found in
a normal household, is 250 times greater than is required to
cause cardiac arrest in an individual.
Fuses
and circuit breakers have a numbered rating system which indicates
the maximum amount of current that they will allow through.
The fuses and circuit breakers are matched to the size of
the electrical wires used in the system. Thus, fuses should
always be replaced with a new fuse of the same rating. A higher
rated fuse will not offer any protection if the system was
to draw too much electricity and could result in an electrical
fire or damage to your equipment. A smaller rated fuse will
cause the circuit to blow the fuse more frequently, leading
to your aggravation and the temptation to bypass the system.
If absolutely necessary, use a smaller rated fuse for temporary
power, but never a larger one.
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Another important safety feature is "grounding." Grounding
occurs when a ground wire is connected from ground potential
to the frame of an electrical device. Grounding is not necessary
for a circuit to work, it is only there for the protection
of individuals from stray current. In a normal circuit, electricity
flows from the "hot" wire (which is usually black) to the
electrical device and back to ground potential through the
neutral wire (which is usually white or gray). A ground wire
(which is usually bare or green) is provided so there can
be an alternate path for the electricity to flow back to ground
potential if an electrical short occurs. For example, if the
wires inside an electrical device have become worn or the
insulation broken down such that the hot wire makes contact
with the case on the device, then the current could possibly
flow through the individual using the device back to ground.
If a ground wire is present, however, the current will take
the path of least resistance and flow through the ground wire
back to ground instead of flowing through the individual causing
an electrical shock.
Never
destroy or cut off the round grounding prong on a plug to
fit it into a socket or extension cord that does not accommodate
the prong. If the equipment you are working with does not
have a ground wire, then consider rewiring the device to accommodate
the grounding feature. Another option is to use double insulated
tools. These tools have an air space around the device to
help insulate you from an electrical shock.
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Another protective device that can be used is called a Ground
Fault Circuit Interrupter, commonly referred to as a GFI or
GFCI. This device is meant to protect human beings from electrical
shocks due to faulty electrical equipment. A GFCI works by
monitoring the current flow to an electrical device and comparing
it to the amount of current flowing back. If there is a difference
between these two values, this means that some electricity
is flowing back to ground through a path other than the wire.
This is called a "ground fault" and when the GFCI detects
this, it stops current flow altogether in the circuit. Consider
the previous example in which the wires inside an electrical
device have become worn or damaged so that the hot wire makes
contact with the casing. If a person were to use the tool,
then electricity could possibly flow through the individual
back to ground. When a GFCI detects this situation, it stops
current flow before harmful amounts of electricity flow through
the individual. Electricity will flow through an individual
easier if the person is working in wet or damp conditions,
which is why it is recommended that GFCI's be installed in
all bathrooms, kitchens laundry rooms, garages, and other
buildings where moisture can be a problem. The protection
from grounding and from a GFCI are similar. However, if your
equipment does not have a ground wire, then a GFCI is your
only form of protection from faulty equipment. GFCI's also
offer protection if the grounding mechanisms are faulty.
There
are three different types of GFCI's available. The most common
type is the GFCI breaker. These are used instead of conventional
breakers to protect everything on the circuit. There are also
GFCI outlets that can easily replace conventional outlets.
These will offer protection for everything plugged into them.
There are also portable types that can be plugged into any
outlet. The device you want to use is then plugged into the GFCI.
All GFCI's are equipped with test buttons which intentionally
cause a ground fault to insure the device is working properly.
It is recommended that all GFCI's be tested every month.
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Polarization
refers to the plugs and outlets that have two different sized
prongs or slots. The idea behind polarization is to ensure that
the hot wire travels through the switch on the device before
it encounters the load or resistance. This helps ensure there
are no "live" wires that are exposed unless the switch is turned
on and current is traveling through the entire circuit. Consider,
for example, a lamp; without polarization, the hot wire could
be traveling through the socket and then to the switch. If someone
was to then touch the socket, they could be shocked. Polarization
ensures that the hot wire travels through the switch first,
protecting you from accidental contact with an energized socket.
Even
with all of these protective devices in place, you can still
get shocked if you accidentally touch both the hot and neutral
wires of a live circuit. This is different from a ground fault
because during a ground fault only some of the current in
the circuit will flow through you to ground. If you touch
both hot and neutral wires then all of the current in the
system will flow through you and your body will act as a normal
electrical device. Therefore, there are additional precautions
you need to take to prevent accidental death and injury.
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- Install
and use the electrical safety devices that are available.
-
Treat every electrical wire as a"hot" wire.
-
Check the condition of all power cords and devices and repair
or replace as necessary.
-
Make sure power is disconnected before working on any electrical
device.
-
If a "hot" circuit must be worked on, call a qualified electrician.
-
Use double insulated tools, which put an additional barrier
between you and electricity.
-
Make sure that any wiring you do meets the suggestions from
the National Electric Code, which are contained in most
books on electricity.
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The
size of wire chosen, usually expressed in the American Wire
Gauge number, for electrical circuits is determined by the electrical
load. The larger the wire size number, the smaller the wire
and therefore, the smaller the electrical load that can be operated
through that circuit. The distance the electricity has to travel
also makes a difference. You can not simply take a 12 gauge
100 ft. extension cord and expect to run a 1 hp motor efficiently.
Improper wiring can result in decreased efficiency and heat
build up in the wire, which in turn can result in a fire. Proper
wiring is accomplished by looking at charts, which will yield
you the proper gauge wire for a given load and a given distance
for a 120 Volt AC circuit. Charts can be found in most books
on electricity.
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Entanglement
with overhead power lines is a special problem on farms. There
are several things you can do to protect yourself from entanglement
with overhead power lines. The best option is to bury all electrical
wires underground. This will eliminate the possibility of entanglement,
but caution will be needed when digging. Always check with your
electric company or call "Miss Utility" before digging to determine
if there are any underground utility lines in the area. Another
thing you can do is to ensure that all augers, dump truck beds,
etc., are lowered before moving them. This simple procedure
will prevent most accidental entanglements. Another thing you
need to be careful of is bumping into the guide wires on electrical
poles. This will cause sagging in the overhead lines and will
make entanglement more likely. Always stay alert and never take
unnecessary risks.
Another
special problem with electricity on the farm is the dusty,
moist and corrosive environments of most livestock houses.
There are waterproof, dust proof, and even explosion proof
electrical boxes, outlets, and motors available for use in
the uniquely troublesome environments of livestock facilities.
These materials ensure safe and reliable use of electricity
throughout your farm.
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So
far we have focused on ways to prevent electrical accidents
and misuse. If an accident still occurs, then certain steps
should be taken.
- If
a fire starts as the result of improper wire size, lack
of over current protection (fuses), or degradation of insulating
materials, then only use fire extinguishers that are recommended
for electrical fires. Fire extinguishers rated for use on
electrical fires will be labeled as a C, BC, or ABC extinguisher.
- If
someone is being shocked by electricity, then disconnect
the power source by turning off the circuit breaker only.
Never try to unplug the cord, move an energized line with
any object, or grab the person yourself to free them. Once
free, CPR should be administered to resuscitate the individual
if necessary.
- If
entanglement occurs with overhead power lines while in machinery,
never try to leave the machinery. Wait until help arrives
because the machine itself can be energized, acting as a
path for the electricity to ground, and if you try to leave
the machine then you can also become a path to ground. If
it is absolutely necessary to leave the potentially energized
machine, as in the case of a fire, then jump free of the
machine with both feet at one time. Do not try to climb
out of the machine as you would normally.
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Disclaimer
and Reproduction Information: Information in NASD does not represent
NIOSH policy. Information included in NASD appears by permission
of the author and/or copyright holder. More
NASD Review: 04/2002
October, 1996
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