IEC Electrical Safety Practices 3 — Questions and Answers
Question 1: What is the primary purpose of equipotential bonding on job sites involving excavations near underground utilities?
- To increase circuit capacity
- To eliminate voltage differences that could cause electric shock between conductive objects (Correct answer)
- To ground equipment to the nearest panel
- To protect against lightning strikes
Correct answer: To eliminate voltage differences that could cause electric shock between conductive objects
Equipotential bonding eliminates potential differences between conductive surfaces so workers are not exposed to shock from voltage gradients.
Question 2: What is the correct sequence for applying personal protective grounds to a de-energized conductor?
- Connect to the conductor first, then to ground
- Connect to ground first, then to the conductor (Correct answer)
- Either order is acceptable if done quickly
- Connect to neutral first, then ground, then conductor
Correct answer: Connect to ground first, then to the conductor
Grounds must always be connected to the grounding electrode first, then to the de-energized conductor, to protect the worker from any residual charge.
Question 3: Which of the following is classified as an 'other than serious' OSHA violation related to electrical safety?
- Exposed live parts that could cause death
- Failure to use proper PPE when there is imminent danger
- Missing cover plate on an outlet box in a low-voltage area (Correct answer)
- Overloaded extension cord causing a fire risk
Correct answer: Missing cover plate on an outlet box in a low-voltage area
An 'other than serious' violation has a direct relationship to job safety but would not likely cause death or serious harm, such as a missing cover plate in a low-risk area.
Question 4: Under NFPA 70E, what is the incident energy analysis method used to determine arc flash PPE requirements?
- Hazard Risk Category (HRC) table lookup only
- Calculated incident energy based on system fault current, working distance, and clearing time (Correct answer)
- Visual inspection by a safety officer
- Manufacturer's label on the equipment
Correct answer: Calculated incident energy based on system fault current, working distance, and clearing time
Incident energy analysis calculates the actual energy exposure based on system fault current, arcing duration, and working distance to select appropriate PPE.
Question 5: What is the required minimum safe distance to maintain from overhead power lines when using metal ladders or scaffolding?
- 3 feet
- 5 feet
- 10 feet (Correct answer)
- 25 feet
Correct answer: 10 feet
OSHA requires at least 10 feet of clearance from overhead power lines up to 50kV when using conductive tools, ladders, or equipment.
Question 6: When using a voltage tester to verify a circuit is de-energized, which procedure best follows NFPA 70E?
- Test once and proceed if no voltage is detected
- Test the tester on a known live source, test the circuit, then test the tester again on a live source (Correct answer)
- Use a non-contact tester and visually inspect the breaker position
- Test between line and neutral only
Correct answer: Test the tester on a known live source, test the circuit, then test the tester again on a live source
NFPA 70E requires the 'test before touch' approach: verify the tester works on a known source, test the circuit, then confirm the tester still works — preventing false negatives from a failed tester.
Question 7: What does an arc flash PPE Category 2 require a worker to wear at minimum?
- Daily wear clothes and safety glasses only
- Arc-rated clothing with a minimum arc rating of 8 cal/cm², face shield, and hard hat (Correct answer)
- 40 cal/cm² arc flash suit
- Class E hard hat and leather gloves only
Correct answer: Arc-rated clothing with a minimum arc rating of 8 cal/cm², face shield, and hard hat
PPE Category 2 requires arc-rated clothing with a minimum arc rating of 8 cal/cm², an arc-rated face shield or flash suit hood, and other required PPE.
IEC Electrical Safety Practices 3
What is the primary purpose of equipotential bonding on job sites involving excavations near underground utilities?