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Module 4: Overhead and Underground Power Lines . Overview of Module 4. Background on power lines Hazards of overhead and underground power lines Injury prevention techniques Summary. Background. Power lines transmit electricity Electrical current exposes workers to serious hazards

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Presentation Transcript
overview of module 4
Overview of Module 4
  • Background on power lines
  • Hazards of overhead and underground power lines
  • Injury prevention techniques
  • Summary
background
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

background cont
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

types of electrical lines
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
power line hazards
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

common misconceptions
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

common misconceptions8
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)
common misconceptions cont
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)

hazard identification
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
slide11

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

injury prevention techniques
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)

slide13

Operation Clearances for Energized Overhead Lines

“In Transit” Clearances for Energized Overhead Lines

Source: OSHA

injury prevention techniques14
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

injury prevention techniques15
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

injury prevention
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

injury prevention17
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

injury prevention18
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

injury prevention19
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

injury prevention20
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

underground power lines
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

underground power lines22
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

tree trimming
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

applicable standards
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
summary of the module
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
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