Electrical Equipment Maintenance & Inspection Flashcards
7 cards from real ESC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electrical Equipment Maintenance & Inspection flashcards as text
According to NFPA 70E, what is required before an electrician opens an energized electrical panel cover for inspection?
Answer: An energized electrical work permit and appropriate PPE based on the arc flash hazard analysis
NFPA 70E requires an energized electrical work permit and PPE selected based on incident energy analysis or PPE category before opening energized panels.
A power transformer's oil sample shows a high concentration of acetylene (C₂H₂) during dissolved gas analysis (DGA). What fault condition does this most likely indicate?
Answer: High-energy electrical arcing inside the transformer
Acetylene is produced only by high-energy electrical arcing and is a critical fault gas indicating an active arc discharge inside the transformer.
Which maintenance task is most critical for ensuring proper operation of a thermal-magnetic circuit breaker's overload protection function?
Answer: Verifying calibration of the thermal element via injection testing
Injection testing verifies that the bimetallic thermal element trips within the required time-current curve parameters, confirming overload protection accuracy.
When performing contact resistance testing on switchgear bus connections, which instrument is used and what does an abnormally high reading indicate?
Answer: Low-resistance ohmmeter (DLRO); indicates a loose or corroded connection
A DLRO (Ducter) measures micro-ohm contact resistance, and high values indicate loose bolting or corrosion that will cause heating under load current.
What is the primary purpose of exercising (operating) a disconnect switch or circuit breaker during scheduled electrical maintenance?
Answer: To prevent oxidation buildup and verify mechanical operation
Exercising switching devices removes oxide buildup on contacts and confirms that the mechanical operating mechanism functions correctly when needed.
Under NFPA 70B 2023, which practice is specifically recommended for maintaining motor branch circuit protective devices?
Answer: Verifying that fuse clips provide firm contact and that fuse ratings match the motor's nameplate
NFPA 70B recommends confirming fuse clip tension and correct fuse ratings to ensure reliable overcurrent protection matched to the motor nameplate.
A maintenance technician finds that the arc flash label on a panelboard lists an incident energy of 8 cal/cm². Which PPE category is the minimum required for energized work on this equipment?
Answer: PPE Category 2 (8 cal/cm² minimum arc rating)
PPE Category 2 has a minimum arc rating of 8 cal/cm², which meets the requirement for equipment with an incident energy of 8 cal/cm².