Risk Management Magazine

Search for Articles

Deadly Currents

Deadly Currents

Headquarters, U.S. Army Corps of Engineers
Safety and Occupational Health Office
Washington, D.C.

Overhead power lines are so common that we practically don’t see them when we look down a road or walk around a building. Birds sit on them and pairs of shoes hang from them with no sparks, fire or other signs of dangerous energy. But contacting power lines is one of the most common causes of Army electrical accidents in both tactical operations and on base. It’s probably because we see them all the time — without any fireworks — that we don’t recognize the hazardous energy they contain.

I used to roof and paint houses. There always came a time when I had to work around the service entrance lines, the heavy cables bringing power into the house. At first, I avoided all contact with the wires, thanks to the local power company’s school program and its flying cartoon light bulb that made me scared of them.

Of course, when you’re working fast, there can come a time when you lose your caution. My hand would slip and I’d hit the wires with my arm. Fortunately, nothing happened. Standing on a porch roof, I backed into the wires and, again, nothing happened.

Eventually, I came to think that these wires were pretty safe to touch, as long as they had that black insulation on them. I would push them, lean on them, lift them, no problem. I realize now the only thing protecting me was dumb luck — seriously dumb luck.

Let me tell you what could have happened through this true description of an accident investigated during my Army safety career. A painter put a metal ladder against the side of a base command building to paint around the service entrance cables. The lines were normal distribution lines — just 110 volts on the hot side, like you’d see in most neighborhoods in the United States. They had a typical rubberized black sleeve on them, which appeared to be in good shape. Where the overhead cables connected to the building wires, there were bolted connections covered with insulating putty. There was no metal visible.

It was a hot day, and the worker busily painted around the hangers holding the wire to the building. He then brushed paint in the tight area right under the hanger. Without warning, there was a dull pop and the worker fell from the ladder. Twelve feet isn’t much of a fall and the worker survived, but he lost his arm. The pop was his arm basically exploding above his elbow.

During the site investigation, it was found that the insulating putty had been worn away from the edge on one of the bolt heads in the cable connection. The worker had accidentally touched this with the back of his hand during a brush stroke. Because of the hot weather, his skin was wet with sweat, allowing the power from the line to easily travel through his arm.

What saved his life — but cost him his arm — was that his bicep was touching the metal ladder as he stretched to reach across it. The current jumped from his arm into the ladder and went to ground, but the heat caused by his body’s resistance to the current inflicted an explosion-type exit wound. And no, he didn’t stand there and shake, like in the movies. It all happened in one, maybe two seconds.

So what does this have to do with Soldier safety? About one-quarter of the Army’s serious electrical injuries and deaths are caused by contact with overhead power lines. There is no completely safe way for a non-electrician to handle these cables if they are energized. The best you can do is stay away from them and call for the proper personnel. If you absolutely don’t have a choice, use a non-conducting object (fiberglass pole, plastic pipe, dry wooden broom handle) to move them out of your way. When you will be in an elevated position, especially the top of a moving vehicle, plan ahead for this hazard and keep an eye out for cables.

Electricity kills or injures in three main ways. The first is by arc flash. On a small scale, if an electrical outlet is loose and won’t hold a plug firmly, or if you don’t push in the plug all the way, the loose connection can cause a very small arc that constantly jumps from the outlet to the metal blade of the plug. This can build up heat quickly and cause a fire. Imagine the size of the flash when a larger power line arcs.

Several Soldier accidents happened when metal objects were accidentally or intentionally put into circuit-panel boxes. The resulting arc flash is like a localized ball of lightning. It can cause burns, vaporize metals that the Soldier inhales and transmit enough power through the body to kill.

The second way you can be injured or killed by electricity is by the current running through your body and interfering with your nerves and muscles. By touching wires or energized surfaces, you can become part of the circuit. It doesn’t take much power either. At 10 to 15 milliamps (one-thousandth of an amp), your muscles can contract and you can’t let go of an energized object. If you’re exposed to that current for long, you can die, especially if the current is running through your heart. If the current runs through major nerves or the brain, it can cause serious permanent injuries or death.

To keep current out of your body, stay well away from exposed, uninsulated electrical conductors such as open panel boxes. Insulation prevents conductors from contacting each other.  Never attempt to repair a damaged cord with tape. Also, never use tools or extension cords with damaged insulation. Be aware that when you’re wet, your skin is up to 10 times less resistant to current than when dry, so avoid all electrical equipment.

The most important measure to protect you from becoming a path for electricity is to make sure all power systems are grounded. Grounding means that there is a wire or other conductive pathway that the electricity can use instead of your body. Use a simple plug-in tester to see if your outlets are grounded. If they are not, stop using the outlets and notify the proper authorities immediately. Never use a three-prong (grounded) plug that has the grounding pin removed. Any equipment plugged into the cord can malfunction and you would not be protected.

The third way electricity kills is by causing internal damage and burns. When power runs through any conductor, the material has some resistance to the current. The resistance causes heat. If there is high current and high resistance, like there is in your body, the fast buildup of heat causes extreme damage that cannot heal. Many electrical shock victims who do survive lose whole organs or limbs due to internal burns.

As mentioned in the accident description above, this heat buildup can be extremely fast — so fast the water in the muscles turns to steam, expanding and causing explosive wounds. Protection against these injuries is the same; don’t contact energized conductors and make sure grounds are in place.

In many accident investigations, it looks like the hazard that led to the injuries or deaths should have been obvious to everyone involved. It doesn’t help the victim or their teammates to see this after the accident. What we all need to do is practice good risk management and evaluate all the hazards of a task or operation — even the hazards we see every day.

  • 16 October 2016
  • Author: Army Safety
  • Number of views: 1085
  • Comments: 0