Shocks & Electrocutions
IS HE DEAD YET?
I often hear, “My client was electrocuted and now has permanent debilitating damage that severely affects his life.”
Electrocution is a grammatical contraction of Electrical Execution that hearkens back to the competition between Thomas Edison and George Westinghouse over whose system, AC or DC, would dominate the power grid. Westinghouse taunted the use of Edison’s DC for executions as a reason why his own AC systems would be safer and should be chosen. He won the competition.
If your client is alive, he was SHOCKED.
If your client is dead, he was ELECTROCUTED, either intentionally or accidentally.
EFFECTS ON THE BODY
Generally the effects of electricity on the body are the purview of Bioengineers, Medical Doctors or Anatomists. However, electricity takes parallel paths through a body via channels of different resistance, i.e., skin, muscle, bone, nerves, and blood vessels. This awareness can often allow the electrical engineer to verify or augment the opinions of the above experts.
Must a shocked or electrocuted person exhibit wounds? Are there entry and exit wounds?
Electricity is not like a bullet. To be shocked or electrocuted, electrical current must pass through the body necessitating at least two points of contact. By far, most shocks are from AC current which alternates direction 120 times per second (twice for each of the 60 cycles per second). Therefore, each point of contact becomes both an entrance and exit.
Is each also a wound?
A wound at the points of contact occurs when the energy density is high enough to damage the skin and underlying tissue, meaning that the amount of current is relatively high or the contact area is relatively small.
In surgery, doctors sometimes use an electric arc at the incision site to both cut and cauterize the skin at the same time. Since there has to be two points of contact for this technique to work, why doesn’t the other point also get cut and cauterized? The technique uses a large metal plate, usually placed beneath the buttocks, to distribute the current over a wide area, thus avoiding any high current density that would damage the skin.
Consider a worker on a tall ladder who has stabilized himself by hooking his armpit over a grounded fire sprinkler pipe and then bumps an energized wire. The contact area at the pipe combined with the salty sweat of the pit will produce a large area of low current density that will not leave a telltale mark. Conversely, the other small point of inadvertent contact will often display an associated burn.
POWER LINE CONTACTS
Unfortunately, people are sometimes injured when inadvertently contacting high voltage power lines, e.g., 4,000v, 12,000v and higher. This can occur from proximity to CB antennas, tossing metal tie-down cables, tree trimming, and other activities like fruit harvesting.
Such contacts can impart very high energy into the human body resulting in blown out heels and severed limbs.
An analysis of the design or construction standards for overhead lines often finds errors or omissions that contribute to the inadvertent contact.
Fire Cause and Origin
Power Wiring and Circuits
National Electrical Code (NEC)
General Order 95
Electrician Trade Practice
Lock Out / Tag Out