Electrical Equipment and Systems Safety
Core concepts
This domain tests whether you can recognize unsafe equipment and conditions and choose the correct response. You should understand arc flash and shock hazards, approach boundaries, lockout and de-energization, PPE selection, temporary power, grounding and bonding of equipment, and the role of approval marks and field evaluation. Know that electrical equipment must be approved for its use, and that modified or repaired equipment may lose its approval unless recertified.
Traps to watch
- Working live: questions often present a convenient reason to work energized. The correct answer is almost always to de-energize, verify absence of voltage, and apply locks and tags, unless justified energized work with the required documentation and PPE exists.
- Testing before touching: always test the tester on a known source, test the circuit, then retest the tester. Questions reward this sequence.
- PPE and boundaries: know that approach boundaries and incident-energy ratings determine PPE, and that rubber gloves need periodic testing and inspection.
- Defective equipment: damaged cords, missing covers, unlisted components, and overloaded circuits must be removed from service, not repaired informally on site.
- Temporary wiring: it must still be approved, protected, and supported; "temporary" does not mean unregulated.
Rule of thumb
Ask: what is the energy source, how is it isolated, how is isolation verified, and who is protected? Any answer that skips verification of de-energization is wrong. For equipment questions, ask whether the item is approved for the location and use; if not, it cannot be installed.
Worked example
A panel cover is missing and a worker proposes taping the opening before starting work. The correct response is to stop, secure the area, and have the cover restored or the equipment taken out of service; tape is not a barrier or an approved repair. The reasoning: exposed live parts remain accessible, so the hazard is uncontrolled regardless of intent.