Transcript Overhead and Underground Power Lines

Overhead and Underground
Power Line Safety
Quentin Baker
Director of Safety
513-5463
516-7456
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Overview
 Background on power lines
 Hazards of overhead and
underground power lines
 Injury prevention
techniques
 Summary
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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
Underground Utility Work
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Background (cont)
• Some activities may
cause interference with
power lines
– Overhead power lines
• Caution: Look out for
overhead power lines
when operating equipment
• Operation of a crane,
forklift, and other
construction equipment
• Changing street lights
• Tree trimming
– Underground power
lines
• Excavation
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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
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Power Line Hazards
When unloading materials, watch
out for overhead power lines
Fire may be caused after overhead
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power lines are hit
Common Misconceptions
• Birds land on power
lines, so they must be
safe to touch - NO
The power lines are safe for
perching, but not when struck
– 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
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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)
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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
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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
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Dump truck operators should use caution when unloading materials near
overhead power lines
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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
Maintain a safe distance from the
power lines
Danger Zone
(10 foot radius from the power line)
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Operation Clearances for Energized Overhead Lines
Nominal Voltage
Minimum Required Distance (Feet)
0 to 50,000
10
Over 50,000
10+0.4 inch for each 1,000 volt
“In Transit” Clearances for Energized Overhead Lines
Nominal Voltage
Minimum Required Distance (Feet)
0 to 50,000
4
50,000 to 345,000
10
Over 345,000 to
750,000
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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
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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
HAZARD:
Safe distance has not
been maintained
– Portable safety barriers
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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
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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
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Injury Prevention
Down power lines are
dangerous
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Injury Prevention
• Fallen power lines can cause fires
Fire caused by fallen power line
• 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
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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
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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
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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
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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
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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
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Summary…
• 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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Conclusion
• Thank you for attending today’s training, if you
have questions for discussion I am available
after the session or I maybe reached at: (336)
513-5463
• Please make sure you signed onto the Training
Roster.
• Remember: Plan your Work and Work your
Plan
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