CTSP Electrical Hazards and Utility Line Safety 4 — Questions and Answers
Question 1: What is 'step potential' in the context of electrical hazards during tree work?
- The voltage difference between two points on the ground that a worker's feet can span (Correct answer)
- The electrical charge stored in a tree's root system
- The potential energy of a falling tree near power lines
- The voltage required to activate a ground fault circuit interrupter
Correct answer: The voltage difference between two points on the ground that a worker's feet can span
Step potential is the voltage difference between two ground points separated by a step distance, which can drive current through a worker's body when a downed energized line contacts the ground.
Question 2: When trimming trees near distribution lines, which condition requires an arborist to STOP work and notify the utility?
- A branch rubbing intermittently against an insulated secondary conductor
- Discovering that a conductor's insulation is cut, abraded, or missing (Correct answer)
- Wind causing a conductor to sway more than 6 inches
- The work site is within 300 feet of a substation
Correct answer: Discovering that a conductor's insulation is cut, abraded, or missing
Damaged or missing conductor insulation creates an immediate electrocution hazard; work must stop and the utility must be notified before any further operations.
Question 3: A tree crew is asked to remove a tree whose trunk leans toward a 7,200-volt primary distribution line. What is the FIRST action?
- Establish the minimum approach distance and assess whether the work can be done safely without contacting the line (Correct answer)
- Begin removing branches on the opposite side to counterbalance the lean
- Install a ground rod adjacent to the tree before starting
- Call 911 to have the line de-energized before arriving on site
Correct answer: Establish the minimum approach distance and assess whether the work can be done safely without contacting the line
Before any cutting begins, the crew must establish whether the minimum approach distance can be maintained; if it cannot, the utility must be contacted to de-energize or guard the line.
Question 4: Which personal protective equipment is SPECIFICALLY required when an arborist must work within the electrical hazard zone of an energized line?
- Rubber insulating gloves and sleeves rated for the voltage present (Correct answer)
- FR (flame-resistant) clothing and a hard hat only
- Class E hard hat and leather gloves
- Arc flash suit rated at 40 cal/cm²
Correct answer: Rubber insulating gloves and sleeves rated for the voltage present
Rubber insulating gloves and sleeves rated to the line voltage are the required PPE when a qualified electrical worker must contact or come within the restricted approach boundary of an energized conductor.
Question 5: Under ANSI Z133, what is the minimum approach distance for a qualified line-clearance arborist working near a 4,160-volt (phase-to-phase) distribution line?
- 1 foot 0 inches (0.30 m) (Correct answer)
- 2 feet 2 inches (0.66 m)
- 3 feet 6 inches (1.07 m)
- 5 feet 0 inches (1.52 m)
Correct answer: 1 foot 0 inches (0.30 m)
ANSI Z133 Table A-1 specifies a minimum approach distance of 1 foot 0 inches for voltages up to 4,999 volts (phase-to-phase) for qualified line-clearance arborists.
Question 6: What does the term 'qualified line-clearance arborist trainee' mean regarding electrical hazard work?
- A worker in training who may only work within the minimum approach distance under the direct supervision of a qualified line-clearance arborist (Correct answer)
- An arborist with fewer than two years of experience who cannot work near power lines
- Any ISA-certified arborist who has taken an electrical safety class
- A utility employee who is also a certified tree climber
Correct answer: A worker in training who may only work within the minimum approach distance under the direct supervision of a qualified line-clearance arborist
ANSI Z133 defines a qualified line-clearance arborist trainee as someone who works inside the MAD only under direct supervision of a qualified line-clearance arborist.
Question 7: A limb falls and drapes across a 12,000-volt primary line, but does not sever it. What is the CORRECT crew response?
- Evacuate the area, establish a safety perimeter, and contact the utility to de-energize before any limb removal (Correct answer)
- Use a fiberglass pole saw to push the limb free from the ground
- Allow the limb to remain until it falls on its own to avoid disturbing the conductor
- Climb the adjacent tree and cut the limb above the conductor with rubber gloves
Correct answer: Evacuate the area, establish a safety perimeter, and contact the utility to de-energize before any limb removal
A limb in contact with an energized primary conductor creates an extreme electrocution risk; only the utility can safely de-energize the line before removal attempts.
CTSP Electrical Hazards and Utility Line Safety 4
What is 'step potential' in the context of electrical hazards during tree work?