ESC Electrical Equipment Maintenance & Inspection 3

Question 1

According to NFPA 70E, what is required before an electrician opens an energized electrical panel cover for inspection?

Accepted Answer

An energized electrical work permit and appropriate PPE based on the arc flash hazard analysis

Answer

NFPA 70E requires an energized electrical work permit and PPE selected based on incident energy analysis or PPE category before opening energized panels.

Question 2

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?

Accepted Answer

High-energy electrical arcing inside the transformer

Answer

Acetylene is produced only by high-energy electrical arcing and is a critical fault gas indicating an active arc discharge inside the transformer.

Question 3

Which maintenance task is most critical for ensuring proper operation of a thermal-magnetic circuit breaker's overload protection function?

Accepted Answer

Verifying calibration of the thermal element via injection testing

Answer

Injection testing verifies that the bimetallic thermal element trips within the required time-current curve parameters, confirming overload protection accuracy.

Question 4

When performing contact resistance testing on switchgear bus connections, which instrument is used and what does an abnormally high reading indicate?

Accepted Answer

Low-resistance ohmmeter (DLRO); indicates a loose or corroded connection

Answer

A DLRO (Ducter) measures micro-ohm contact resistance, and high values indicate loose bolting or corrosion that will cause heating under load current.

Question 5

What is the primary purpose of exercising (operating) a disconnect switch or circuit breaker during scheduled electrical maintenance?

Accepted Answer

To prevent oxidation buildup and verify mechanical operation

Answer

Exercising switching devices removes oxide buildup on contacts and confirms that the mechanical operating mechanism functions correctly when needed.

(ESC) Electrical Safety Certification Practice Test

(ESC) Electrical Safety Certification Practice Test

ESC Electrical Equipment Maintenance & Inspection 3