Power Line Safety and Electrical Hazards
Power Line Safety and Electrical Hazards
This domain tests clearance, voltage assumptions, and encroachment prevention. Expect table clearances and the rule that contact is never acceptable.
Core rules
- OSHA 1926.1408 Table A sets minimum clearances for construction cranes: 10 ft for lines up to 50 kV; 15 ft for 51–200 kV; 20 ft for 201–350 kV; 25 ft for 351–500 kV; 35 ft for 501–750 kV; 45 ft for 751–1,000 kV; 50 ft over 1,000 kV.
- If voltage is unknown, treat the line as the highest voltage that could be present, or use the most conservative table value and get the utility to confirm.
- De-energize and isolate, or use a qualified spotter and proximity warning device. Do not rely on rubber tires or insulation.
- Maintain clearance for the boom, jib, load line, load, and any suspended rigging, not just the boom tip.
- If contact occurs: keep everyone away, do not touch the crane, and call the utility and emergency services.
Worked example: A 138 kV line is near the swing path. Table A requires 15 ft. If the planned boom position cannot guarantee 15 ft for every movement, stop and have the utility de-energize or relocate the line.
Traps
- Measuring clearance only at the starting position.
- Assuming 10 ft is enough for low-voltage lines.
- Using a spotter who is not qualified or has no authority to stop the lift.
- Exiting the crane during contact without following emergency procedure.