Natural Forces At Work

George Carlin summed up the hazards of working with electricity quite well when he said, “Electricity is really just organized lightning.” Few people, except for some extreme golfers and Benjamin Franklin, would normally take extraordinary risks with lightning. Yet, too many electricians are still injured and killed each year on the job. 

While there are sources of such incidents unrelated to electricity, including falls, vehicular accidents and tools, the unique aspects of electricity and its potential devastating effects on the human body rightly get significant attention from the safety agencies, as more than half of the fatalities are caused by exposure or contact to this hazard. In addition to electrocution, a few of the hazards that need to be considered include potential damage from radiant and convective heat (an electric arc is hotter than the sun), infrared and ultraviolet light damage to the eyes, excessive decibel levels to the ears, and pressure wave and concussive forces to external and internal body parts.

Electrical accidents are not limited to electricians. Fortunately, the figure below shows a decline for all construction workers, which is similar to the trend for all industries, declining 31 percent over the same time period.

Of the 67 deaths in 2011 from electrical contact in the construction industry, 34 were classified as electricians, along with an injury rate in 2011 of 3.6 percent to the 723,000 electricians. There are all sorts of statistics about age (fatalities over age 55 are nearly triple those under 24), season (June to September accounts for more than half of the injuries in a year), and many other categories. What matters more is why the accidents occur and how we can force that number lower.

Obviously, contact with wires is the source of the current, whether overhead, in the walls, or within equipment or tools. Strangely, it is at the power line frequencies (50–60 hertz) that the human body is most vulnerable to the amount of current; it creates a “can’t-let-go” situation. For most males, that is only 9 milliamps (mA) of alternating current, whereas it is nearly six times that for direct current, and likewise for 10 kilohertz. That is why the trip point for most ground-fault circuit interrupter (GFCI) receptacles is 5 mA.

Removing the hazard by de-energizing­ the circuit being worked on and any that could possibly be contacted is the ideal scenario, but, in some rare situations, that isn’t going to happen. Both NFPA 70E, Standard for Electrical Safety in the Workplace, and OSHA 29 CFR 1910 provide detailed information on who, what, where and how to create an electrically safe working condition. Anyone who is exposed to the hazards should know them. The following suggestions do not supersede or replace of those requirements, but rather they give brief perspective on creating them.

The overall process is to plan, do, check and act. Every company, whether a sole proprietor or a 250-person electrical contracting firm, should establish appropriate policies and practices to address worker safety. Conduct periodic training on preventive and protective measures with regard to the hazards and safe practices for all workers, no matter how many years of experience. Supervisors and co-workers should continually check that such practices are being followed and determine what corrective actions are needed. All must act to ensure that the process is continually reviewed and improved. Most workers are probably familiar with what they need to do, but cutting corners to get jobs done faster, complacency in using the proper tools and personal protective equipment, neglecting proper lockout/tagout procedures, a lack of understanding of the potential hazards, and neglecting to monitor the situation while at work are all contributing factors to accidents.

Of these factors, we have made great strides in wearing the proper PPE and understanding the arc flash hazard, which may explain a part of the declining injuries and fatalities trends. National Electrical Code 2011 Article 110.24 states that nondwelling service equipment is required to be field-marked with the amount of available fault current when installed or modified. OSHA requires that, where there is a risk of injury to a worker’s skin from fire or explosion, an employer or contractor shall provide the worker with—and require the worker to use—outer fire-resistant clothing that meets an approved industry standard and is appropriate to the risk.

Following these two requirements will minimize the damaging effects on the human body when inadvertent contact with energized circuits unleashes the “organized lightning.”

About the Author

Richard P. Bingham

Power Quality Columnist
Richard P. Bingham, a contributing editor for power quality, can be reached at 732.287.3680.

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