The Definition of Overhead Power Lines

Definition of Overhead Power Lines

Overhead power line safety is the set of planning, distance and work practices that keep workers, tools and equipment from contacting or arcing to energized overhead electrical lines. Contact with overhead lines is a leading cause of electrocutions, especially in construction, tree trimming, agriculture and work with cranes, dump trucks, ladders and aerial lifts. Because many overhead lines are not insulated, OSHA requires workers to assume all overhead lines are energized unless the utility confirms they have been de-energized and visibly grounded.

Key Facts About Overhead Power Lines

• For lines up to 50 kV, cranes and unqualified workers must generally stay at least 10 feet away.
• Required clearances increase with voltage, such as 15 feet for lines over 50 kV up to 200 kV under OSHA's crane standard (1926.1408).
• Coverings on overhead lines are usually weather protection, not insulation.
• Electricity can arc across air gaps, so contact isn't needed for an electrocution.
• A dedicated spotter, warning lines and proximity alarms are common controls when equipment works near lines.

Example of Overhead Power Lines

Before raising a dump truck bed at a job site under a distribution line, the foreman marks a no-go zone, assigns a spotter, and calls the utility to confirm the line's voltage. Because the work would come within 10 feet, the utility de-energizes and grounds the line before work starts.

How to Work Safely Near Overhead Lines

1. Survey the site for overhead lines during planning.
2. Contact the utility to confirm voltage and request de-energizing or insulating covers.
3. Set clear minimum distances and mark them with flags or warning lines.
4. Use a dedicated spotter whenever equipment could approach the limit.
5. Use nonconductive ladders and keep tools and materials away from lines.
6. If equipment contacts a line, stay in the cab if safe, and keep others away.

Related Terms

• Minimum Approach Distance (MAD)
• Electrocution
• Electrical Hazard
• OSHA Focus Four (Fatal Four)

Frequently Asked Questions: Overhead Power Lines

What should you do if equipment touches a power line?

Stay in the cab if there is no fire, warn others to stay away, and call the utility. If you must leave, jump clear without touching the machine and ground at the same time, then shuffle away with small steps.

Are power lines with a black coating insulated?

Usually not. Most coverings on overhead lines protect against weather and won't protect a person from shock.

How do I find out the voltage of a power line?

Contact the utility that owns the line. Never estimate voltage by the size of the line or pole.