Every year many workers are injured or electrocuted due to direct or indirect contact with overhead power lines. In fact, over 40% of all U.S. electrical fatalities involve contact with overhead power lines. Most of these injuries are suffered by qualified utility line workers although a significant number of fatalities are incurred by unqualified workers such as painters, roofers, heavy equipment operators, and tree trimmers.
Before we go further I think it is important to understand the difference between direct and indirect electrical contact. Direct contact with a powerline is when some contacts the line with their hands or another body part. Indirect contact involves a conductive object, such as a scaffold pole or metal ladder that the worker is holding contacts or comes within close proximity to an energized line and because the metal object is conductive the worker receives a shock injury.
The Ten Foot Rule
Be safe by ensuring work is performed at a safe distance from energized power lines. OSHA refers to this safe distance as the minimum approach distance or MAD. See OSHA requirements for safe work near power lines in 1910.333 which states that unqualified employees and the longest conductive object he or she may contact must maintain a minimum approach distance of at least 10 feet from overhead power lines energized up to 50,000 volts to ground. Additional distance will have to be added to energized lines above 50kV to ground. (see 1910.333(c)(3)(i)(A)(2) for additional information)
NFPA 70E has language that mirrors OSHA but 70E uses different terms. Instead of minimum approach NFPA 70E uses the terms limited approach distance. See table 130.4(D)(a) on page 24 of the 2018 edition for safe distances from movable conductors such as over powerlines.
If work will be performed by unqualified workers inside of the minimum approach distance (MAD) the lines need to be de-energized, verified as de-energized by a qualified person and grounded (see 1910.333(c)(2) for additional details) Contact the utility to isolate the line from the source prior to the start of the work.
Prior to the start of work ask the utility to provide the information needed to properly plan the job. Such as the voltage at which the line is operating. Use this information to determine the safe working distance.
Post signs to alert truck drivers, tree trimmers and others performing work outside of your facility of the location of overhead power lines. Painted roads and driveways that indicate that power lines are overhead can also be an effective alerting method.
Erect a physical barrier by using cones and danger tape to keep employees and vehicles outside of the minimum approach distance to the powerline.
Have a written electrical safety program that includes a section that mandates your company’s safety requirements when working near powerlines. See NFPA 70E Informative Annex N which provides an example overhead powerline work procedure.
A pre-job brief can save a life
Prior to the start of work make workers aware of the powerline as well as any other hazards associated with the job. Discuss the precautions needed to ensure everyone’s safety. Walk the job site with the employees to identify the location of the powerline and the minimum approach distance to it.