Written by Steve Stephenson
Electrical accidents result from injuries or death from:
- Electric shock
- Burns (electrical, arc flash or thermal contact)
- Explosions (including arc blast)
The most common electrical accidents are those resulting in an electrical shock.
When the body becomes a part of an electrical circuit an electrical shock occurs. What this means is that parts of the body are in contact with a source of electrical power such that electricity can enter the body at one point and leave through another. The two points may be very close together, or in widely separated parts of the body.
An electrical circuit is formed when one of three things happens:
- A person comes in contact with both wires in an electric circuit.
- A person contacts one wire of an energized circuit and the ground.
- A person contacts a metallic part that has become "hot" (electrically energized) and the ground.
What are the causes of electrical accidents?
Most electrical accidents are caused by a combination of three factors:
- Unsafe equipment or unsafe installation of equipment.
- Workplaces made unsafe by the environment.
- Unsafe work practices.
Electrical shock accidents are the most common types of electrical accidents. For example, the top five leading causes of electrical accidents in construction and maintenance work include:
- Failure to maintain an overheat clearance of 10 feet (eg. crane booms contacting overhead wires)
- Drilling and cutting through cables.
- Using defective tools, cables and equipment.
- Failure to de-energize circuits and follow Lockout/Tagout (LOTO) procedures.
- By-passing electrical protective devices.
The severity of the shock, and the resulting injury, in an electrical accident depends on a number of factors. These include the amount of electrical current (which depends on the voltage and the path through the body) and the amount of time the current flows through the body.
Even small amounts of electrical current can be dangerous in some circumstances. A current as low as 3 mA (milliamps) will produce painful muscle contractions. At 10 to 40 mA muscles will contract so strongly that you will not be able to let go of the electrical conductors. Currents greater than 30 mA can cause respiratory paralysis and death.
Notice how small these electrical current are. A circuit breaker might be set at 15 amps. This is 500 times greater than what can be lethal. Circuit breakers are designed to protect equipment, not people.
How can workers be protected from the electrical hazards?
OSHA gives the the basics of electrical hazard protection as:
- Insulation - cover live parts with high-resistance material such as rubber or plastic.
- Guard exposed live parts to prevent access by unqualified persons.
- Ground both complete systems, and individual machines and equipment.
- Use electrical protective devices – fuses, circuit breakers, and GFCIs.
- Safe work practices, including:
- De-energizing, locking out and appropriately tagging (LOTO) electric equipment before inspecting or making repairs.
- Using electric tools that are in good repair.
- Using good judgment when working near energized lines.
- Unqualified employees and mechanical equipment must stay at least 10 feet away from overhead power lines
- Using appropriate protective equipment.
- Be aware of your surroundings and any electrical hazards.
- Workers must be trained in safety-related work practices.
- Workers must be trained in any other electrical safety procedures.