Other than shocks to people electrical accidents can start fires, cause explosions, and
damage equipment.
Many forms of electricity have been applied to the body for therapy and the electricity
generated within the body is measured for diagnosis. Consider, for examples, the defibrilator,
electro-shock therapy, the pacemaker, the electro-cardiograph, the electro-encephelograph, the
electro-cauterizer.
Electricity is used for capital punishment and for torture.
I will talk about some of the casualties and how we protect against them, and I will
describe some of the lawsuits involving them in which I participated as a consultant
or expert witness.
Every year approximately 400 people in the U.S. are killed by electric shock. More are
injured by being startled by an electric shock, lose their balance, and fall off a
ladder.
To cause a shock the electricity must enter at one place on your body and exit at
another place. It is the current through your body which causes the shock, not the
voltage at a single place. A bird on a high voltage wire gets no shock. It is common
for one of the shock places to be the earth or a piece of metal connected to the earth. Think
of a faucet in your bathroom for an example. Think of bare feet on wet ground for another
example.
Electricity through your body spreads out between the two places and can raise bloody
hell between. If enough passes through your heart your story ends by ventricular
fibrillation followed by asphyxiation because the heart stops pumping blood. Electric current can
damage your organs and your nervous system. Among
my clients is one whose one bare foot was on the ground, whose other bare foot
stepped on a manhole cover, and whose body shakes to this day. Dogs are sometimes
electrocuted sniffing around construction sites. Cows give less milk when they get
small shocks from milking machines; there is major litigation as a result. People get
shocked, and sometimes killed, by touching an electrocuted body in order to rescue it
from contact with a fallen high voltage wire. A minor electric shock to a person on a
ladder can startle a person who then loses his balance, falls off, and is seriously injured
by the fall. I will talk about electric tools later on.
A common mode of shock comes from touching a defective electrical appliance, such
as a hair dryer, with one hand and a water faucet with the other. To say nothing about
standing in a bathtub of water.
There are several odd effects of electricity on the body. If you get a shock through an
arm, if the current exceeds a 'let go' level, your arm will be paralyzed. (It happened
to me.) A second effect is that your arm may jerk, as did Signor Galvani s laboratory
frog leg for the world's first galvanic response. The jerk may make you fall off a
ladder, and often does. A third effect is that the heart is sensitive to electrocution
during only approximately 1/7 of its cycle. (I was an example of let go paralysis and
heart cycle insensitivity when I forgot to pull the switch on a 440 volt power supply
and picked up two wires, hand to hand.)
Many electric shocks result from improper handling of electrical wires and devices. An
entire class of shocks comes from the accidental touching of overhead high voltage electric
wires. These have been touched by cranes, irrigation pipes being handled, grain augers,
trucks, workers on scaffolding or roofs, boat masts, radio and TV antennas, tree
branches, and workers with long tools. And by trespassers.Yet such wires can be
handled quite safely if handled with proper insulated tools and trained skill.
Electric current through anything heats it. If the anything is a light bulb the heat
radiates light; that is how Edison started the electric utility industry. But if the anything
is combustible insulation, and the current in an adjacent wire is accidentally too high,
the heat can start a fire. Much of the National Electric Code is to prevent such fires.
Short circuit current can be enormous for a fraction of a second before a fuze or circuit
breaker interrupts it. If it flows through an arc before interruption, radiant heat from the arc can
cause a skin burn and clothing fire and the hot gas of the arc can cause an explosion.
In addition to human damage electricity can cause material losses by being too high or
too low a voltage, having momentary high voltage pulses, having the wrong alternating
current wave form and by unplanned interruption.
The combination of utility and danger has given rise to major engineering and to major
law to permit the utility and to protect from the danger. A few examples:
Electrical circuits may be passed through fuses of low melting point metal which melt
and open the circuit if the current exceeds their rating. The disadvantage of fuses is that
they are one-shot and must be replaced after each action. Older homes used fuzes.
Instead of a fuse an electro-mechanical circuit breaker pops open if the current exceeds
its rating and may be re-closed either by hand or by remote control. Newer homes use
manual reset circuit breakers. Circuit breakers are sized from small fractions of an
ampere in electronic circuits to many thousands of amperes at high voltage in public
utilities. I had a case in which a large circuit breaker exploded and sprayed burning oil
on workers.
A truly wonderful device, now used almost everywhere in homes, is the Ground Fault
Circuit Interupter, the GFCI, invented by professor Dalziel at UC Berkeley. It is a circuit
breaker which opens within a tenth of a second if a shock current exceeds six
milliamperes, a safe combination. They are incorporated in electrical outlets near water
faucets in bathrooms since a common source of shocks is from holding a defective
hair dryer and touching the faucet or standing in the bath. Also elsewhere, of course.
The most common safety device is the three prong plug. In addition to the two prongs
which connect to the power wires there is a third prong which is wired to the metal
body of the connected device, and which touches a contact in the socket which is
wired to ground. If a defect in the device connects a power wire to the metal
body, the resulting short circuit blows a fuse or circuit breaker but prevents a power
connection to the user who may also be touching ground.
There is now a dangerous practice of depending on a wide blade prong to connect the
device body to that power side which is typically grounded and dispensing with the
third prong ground connection. This is the practice with plastic body electric hand
tools which boast of double insulation of the motor winding. I had a corpse which
disputed this small economy. Sure, the winding was well insulated but the motor
brushes and commutator could not be. I measured a direct connection from power wire
to brush to commutator to internal moisture to motor shaft to metal gears to drill chuck.
Thence to hand, through the user, to his wet feet to ground where that corpse now lies.
The product liability settlement included an secrecy agreement about my analysis. And yes, the
printed
instructions said that you should not use the drill in a wet environment. I have things
to say about printed instructions.
A vital if mundane safety is the lockout/tagout requirement to protect an installation
or maintenance technician from encountering live wires. I had a case in which, among
other things, an electrician melted the jaws of his wire cutter by cutting a two
conductor cable he assumed had been locked out.
In industry large electric motors are connected to power by three wires instead of two. (It is
called
3 phase power.)
If any two wires are interchanged in error the motor runs the wrong way. I had a
lawyer's client with crushed fingers as a result.
An electrical tool was enclosed in a pair of matching plastic case halves. Its
power cord used stranded wire for flexibility, as is common practice. But there was
inadequate internal insulation so one bare strand peeked out between the halves,
shocked the user, and he fell off his ladder.
A dog wash operator with wet feet used a hair dryer on a dog and was shocked. No
GFCI of course.
A boat owner improperly connected an extension cord to his boat. His friend also was
shocked when he touched and moved the body. No GFCI of course.
A $2.5 million dollar fire was blamed on a neon sign transformer. An electrical expert
set up and video recorded a classic example of a neon sign transformer starting a fire,
which it absolutely can do under certain circumstances. I know about such
transformers and demonstrated that these circumstances did not obtain.
The $2.5 million suit was settled for $13,000.
That circuit breaker explosion was due to an inadequately trained electrician who left
an improper setting within the breaker, as I explained to the juries in two trials. The
burned electrician was awarded $1.1 million, the largest ever award in Southern Ohio.
Power to an AC motor was incorrectly measured by measuring motor current and
voltage. AC motor power can only be measured by a wattmeter. (Motor current
includes a component which does not deliver power.)
Note: All numbers are very approximate because of the variations among people
and the different electrical paths through individual victims.
First, shocks and electrocutions.
Next, defenses
Next, how about another few cases which might resemble yours?
Summary
Kinds of electrical accidents:
References