Module 4: Overhead and Underground Power Lines

1. Module 4:Overhead and Underground Power Lines

2. Overview of Module 4 • Background on power lines • Hazards of overhead and underground power lines • Injury prevention techniques • Summary

3. Background • Power lines transmit electricity • Electrical current exposes workers to serious hazards • Most common hazard is electrocution • Most workers are unaware of potential electrical hazards • Power lines can be • Overhead • Underground Power lines and transmission towers Underground Utility Work

4. Background (cont) • Some activities may cause interference with power lines • Overhead power lines • Operation of a crane, forklift, and other construction equipment • Changing street lights • Tree trimming • Underground power lines • Excavation Caution: Look out for overhead power lines when operating equipment

5. Types of Electrical Lines • Electrical Cables • High Voltage, Low Voltage • Supervisory and Signaling Cables • Cathodic protection (cabinets, cables, earthing conductors, cable shrouds) • Communication Cables • Phone lines • Coaxial cables (e.g. data cables) • Broadband cables • Tram traction cables and trolley wires • Railway supply cables and traction wires

6. Power Line Hazards Who is at risk? • Almost everyone working near power lines • Common hazards: • Electrocution • Injuries are typically fatal • Electrical shock • Fires • Falls • As a result of contact with electricity When unloading materials, watch out for overhead power lines Fire may be caused after overhead power lines are hit

7. Common Misconceptions • Birds land on power lines, so they must be safe to touch - NO • Main objective of electricity is to reach the ground using the most direct route • Birds do not get electrocuted when they land on wires because they do not represent a path to the ground The power lines are safe for perching, but not when struck

8. Common Misconceptions • Power lines are insulated, so they are safe to touch - NO • They are not always insulated • Insulation deals with placing nonconductive material around the wire • Insulation is a material that offers high electric resistance making it suitable for covering wires to prevent the possible future contact of adjacent conductors resulting in a short circuit • Just because a wire is weather protected does not mean that it is insulated • Weather protection prevents water and snow from reaching the wire (and insulation, if used)

9. Common Misconceptions (Cont) • Nonmetallic ladders are safe around power lines - NO • Wet ladders can be a conducting medium for electricity • If power lines are not touched, they are safe - NO • Electricity can jump Maintain a safe distance from the Danger Zone (10 foot radius from the power line)

10. Hazard Identification • Conduct site investigation to identify existing conditions of: • Voltages of lines and equipment • Presence of hazardous, induced voltages • Presence and condition of protective grounds and equipment grounding conductors • Locations of electrical circuits and equipment • Maximum switching transient voltages

11. Dump truck operators should use caution when unloading materials near overhead power lines

12. Injury Prevention Techniques • Stay away from power lines while working • Maintain a safe distance • OSHA’s “10-Foot Circle of Safety” rule • Increase safe distance near higher voltage power lines Maintain a safe distance from the Danger Zone (10 foot radius from the power line)

13. Operation Clearances for Energized Overhead Lines “In Transit” Clearances for Energized Overhead Lines Source: OSHA

14. Injury Prevention Techniques • Recognize high voltage power lines • If unknown, the appropriate agency should be contacted • Inform others about high-voltage power lines Be aware of nearby high-voltage power lines

15. Injury Prevention Techniques • Examine the site • Be mindful of power lines • Search carefully around the site • Look for lines not seen due to obstructions • Alert others at the pre-job briefing • Assume all lines are energized and potentially dangerous • Make a safety clearance boundary • Portable safety barriers HAZARD: Safe distance has not been maintained

16. Injury Prevention • Use a spotter • Equipment operators have limited visibility • Get spotter’s help to stay clear of overhead power lines • Spotter’s job should only require spotting and NOT guiding • Guiders may be at risk of electrical shock • Especially when using a tag line A spotter guiding heavy equipment operator

17. Injury Prevention • When working with tall and long equipment • Carefully plan and organize work with heavy equipment • Keep vehicles clear of power lines • Watch out for long objects • Adjust the position of equipment to maintain a safe distance from power lines Working with tall equipment

18. Injury Prevention • In cases of fallen power lines • Stay away • Call for help • Shuffle with your feet together and on the ground to minimize electrical shock • Encourage others to do the same Down power lines are dangerous

19. Injury Prevention • Fallen power lines can cause fires • If a co-worker makes contact with a power line • Stay away • Protect yourself • You could be shocked too if you touch someone who is in contact with electricity Fire caused by fallen power line

20. Injury Prevention • If you hit a power line • In case of no immediate danger • Move the equipment away • Have someone call 911 • Stay on the equipment until you know it is safe. • Warn others to stay away • If you MUST get off the equipment, jump clear Crane hitting a power line

21. Underground Power Lines • Hitting a buried power, gas or communications line can cause • Injury • Excessive cost of repair • Plan the work ahead • Call the utility company With proper planning, these types of mistakes can be avoided

22. Underground Power Lines • Locate and mark the perimeter of underground lines • Exercise caution when excavating near power lines • Some manual excavation may be required • Stay away from pad mount transformers • Green metal box Underground utility line that has been hit

23. Tree Trimming • Trees that grow into power lines can cause unnecessary power outages • Trees planted under or near power lines are potentially dangerous hazards • Before tree trimming, check for the power lines • Use proper equipment and trained personnel Tree trimming may be dangerous if power lines are hidden in the foliage

24. Applicable Standards • 29 CFR 1926, Subpart K – Electrical • 29 CFR 1926, Subpart N – Cranes, Derricks • 29 CFR 1926, Subpart O – Motor Vehicles, Mechanized Equipment • 29 CFR 1926, Subpart P – Excavations • 1926.416 Electrical Hazards • 1926.955 Overhead Lines • 1926.956 Underground Lines

25. Summary of the Module • Working in proximity of overhead and underground power lines is hazardous • Most common hazard is electrocution • Workers should be aware of such hazards • Several injury prevention techniques should be exercised to prevent injuries and fatalities • Need sufficient training to understand the hazards and practices for injury prevention • One of the best ways of hazard elimination is maintain a minimum safe distance • Properly locate underground power lines before starting of work

26. End of Module 4