CTSP Electrical Hazards and Utility Line Safety 5 — Questions and Answers
Question 1: Which type of wood is generally considered the MOST dangerous to use near energized conductors because of its electrical conductivity?
- Green (freshly cut) wood with high moisture content (Correct answer)
- Dry seasoned hardwood
- Dead standing wood that has dried for over one year
- Pressure-treated lumber used as rigging anchors
Correct answer: Green (freshly cut) wood with high moisture content
Green wood has high moisture content, which dramatically increases its electrical conductivity and makes it far more dangerous to use near energized lines than dry wood.
Question 2: What is 'touch potential' and why is it relevant to tree workers after a tree contacts a power line?
- The voltage difference between the ground and an energized object a worker touches simultaneously, creating a path for current flow (Correct answer)
- The pressure required for a branch to pierce conductor insulation
- The minimum force at which a downed line can energize soil
- The voltage a rubber glove can withstand before breakdown
Correct answer: The voltage difference between the ground and an energized object a worker touches simultaneously, creating a path for current flow
Touch potential is the voltage between a worker's hand touching an energized object (like a tree in contact with a line) and their feet on the ground, which drives current through the body.
Question 3: When a tree or large limb falls across a high-voltage transmission line, which action is PROHIBITED for the tree crew?
- Attempting to remove the tree or limb using any equipment until the utility confirms the line is de-energized and grounded (Correct answer)
- Calling 911 to report the incident
- Keeping bystanders at least 300 feet from the downed line
- Documenting the incident for the job file
Correct answer: Attempting to remove the tree or limb using any equipment until the utility confirms the line is de-energized and grounded
No equipment operation or removal attempt is permitted until the utility has de-energized and grounded the line, regardless of whether the line appears intact.
Question 4: How does arc flash differ from direct contact electrocution as a hazard for tree workers near high-voltage lines?
- Arc flash can injure or kill a worker without any physical contact with the conductor, through radiant heat and blast pressure (Correct answer)
- Arc flash only occurs in underground cable vaults, not overhead lines
- Arc flash requires the worker to be touching two conductors simultaneously
- Arc flash is less dangerous than direct contact because it dissipates quickly
Correct answer: Arc flash can injure or kill a worker without any physical contact with the conductor, through radiant heat and blast pressure
Arc flash releases tremendous energy — heat, UV radiation, pressure, and molten metal — that can severely injure or kill workers who are near but not touching the conductor.
Question 5: Which type of rope is PROHIBITED for use as a climbing line or rigging line when working near energized conductors?
- Natural fiber rope (manila, sisal) or any rope that is wet or contaminated (Correct answer)
- Double-braid polyester climbing rope
- Kernmantle nylon climbing line rated above 5,000 lbs
- Braided Technora rigging line rated above 10,000 lbs
Correct answer: Natural fiber rope (manila, sisal) or any rope that is wet or contaminated
Natural fiber ropes absorb moisture and become conductive; any wet or contaminated rope significantly reduces the insulating properties needed near energized lines.
Question 6: A utility provides a 'clearance' to work on a distribution line. What does this mean for an arborist crew?
- The utility has de-energized, tested, and grounded the specific circuit, and the crew may proceed within the cleared zone (Correct answer)
- The utility has inspected the work area and confirmed no lines are present
- The crew is authorized to cut within 1 foot of any conductor in the area
- The utility has moved the line to create physical clearance from the tree
Correct answer: The utility has de-energized, tested, and grounded the specific circuit, and the crew may proceed within the cleared zone
A utility clearance means the specific circuit has been de-energized, tested for absence of voltage, and grounded — making it safe for authorized workers to operate within the cleared zone.
Question 7: What OSHA standard primarily governs electrical hazard requirements for tree trimming and removal work performed by utility line-clearance contractors?
- 29 CFR 1910.269 — Electric Power Generation, Transmission, and Distribution (Correct answer)
- 29 CFR 1926.416 — General Electrical Requirements for Construction
- 29 CFR 1910.303 — General Wiring Requirements
- 29 CFR 1910.147 — Control of Hazardous Energy (Lockout/Tagout)
Correct answer: 29 CFR 1910.269 — Electric Power Generation, Transmission, and Distribution
OSHA 29 CFR 1910.269 specifically covers work on or near electrical power generation, transmission, and distribution lines, including utility line-clearance tree trimming operations.
CTSP Electrical Hazards and Utility Line Safety 5
Which type of wood is generally considered the MOST dangerous to use near energized conductors because of its electrical conductivity?