Electrical Safety and Safe Work Practices
Electrical Safety and Safe Work Practices
This domain tests how you establish and verify an electrically safe work condition, select PPE and test instruments, and apply NFPA 70E and OSHA rules in the field.
Core rules
- De-energize, lock/tag, release stored energy, and verify absence of voltage before work. Test the tester on a known source, then test all phase combinations, then re-test the tester.
- Use a meter with a CAT rating equal to or higher than the location: CAT IV at service entrances, CAT III at distribution and MCCs. Verify the meter voltage rating and leads.
- Establish limited, restricted, and arc-flash boundaries; complete a shock and arc-flash risk assessment; use an energized work permit only when justified.
- Treat capacitors, UPSs, VFDs, and backfeed sources as stored-energy hazards.
Worked example
A 480 V MCC bucket is to be worked on. The technician selects a CAT III 600 V meter, proves it on a known 120 V source, opens the disconnect, locks/tags, verifies the bucket terminals phase-to-ground and phase-to-phase, then re-proves the meter. All readings are zero; the bucket is safe. The reasoning: the meter CAT rating matches the location, the proving unit confirms the meter works before and after, and all combinations are tested to catch a backfeed or stuck pole.
Traps
- Relying on PPE instead of de-energizing.
- Using a CAT II meter at a service entrance.
- Testing only phase-to-ground and missing a backfeed.
- Forgetting that a VFD can retain DC bus charge.