Electrical Equipment Maintenance & Inspection Flashcards

What is the correct procedure for verifying that a conductor is de-energized before beginning maintenance work?

Answer: Test with a known good voltage tester, test the conductor, then retest the tester on a known live source

The 'test-before-touch' procedure requires verifying the tester works on a live source, testing the de-energized conductor, and confirming the tester still works to rule out tester failure.

During inspection of a dry-type distribution transformer, which finding should prompt immediate further evaluation and possible replacement?

Answer: Cracks or carbonization in the winding varnish coating

Cracks or carbonization in winding varnish indicate thermal degradation or previous overheating that may have compromised insulation integrity.

When should equipment grounding conductor (EGC) integrity be verified as part of a maintenance program?

Answer: After any modification to the branch circuit and during periodic maintenance inspections

EGC continuity should be verified after any circuit modification and periodically during maintenance to ensure the fault return path remains intact.

What hazard does a loose or missing bus bar bolt in a switchboard create during a bolted-fault condition?

Answer: Increased resistance generating heat and potential for arc flash due to the poor connection

A loose bus bolt creates a high-resistance joint that generates intense heat under load and can initiate an arc flash during fault conditions.

According to NFPA 70E, which condition allows energized electrical work to be performed without a written permit?

Answer: De-energizing the equipment would create a greater hazard or is infeasible due to equipment design

NFPA 70E permits energized work without a written permit only when de-energizing creates a greater hazard or is infeasible due to equipment design or operational limitations.

Which test best evaluates the mechanical condition of a vacuum interrupter in a medium-voltage circuit breaker?

Answer: Hi-pot (AC withstand) test across the open vacuum interrupter contacts

An AC withstand (hi-pot) test across the open contacts verifies that the vacuum integrity is sufficient to withstand the specified dielectric voltage, confirming the bottle is not compromised.

A qualified electrical worker discovers that a junction box cover in a wet location is missing. Under NFPA 70 (NEC), what is the correct corrective action?

Answer: Install an approved weatherproof cover rated for wet locations before the circuit is re-energized

NEC requires enclosures in wet locations to be weatherproof; an approved wet-location cover must be installed before re-energizing to prevent shock and equipment damage.