Switchgear and Busway Inspection Flashcards

What is the NETA-recommended minimum insulation resistance value (in megohms) for switchgear bus insulation rated at 5 kV when tested with a 2500 V megohmmeter?

Answer: 100 MΩ

NETA specifies a minimum of 100 MΩ as the acceptable insulation resistance for medium-voltage switchgear bus insulation tested at 2500 V DC.

Which of the following describes the correct procedure for verifying the operation of a manual trip mechanism on a medium-voltage circuit breaker?

Answer: Manually operate the trip lever or push-button with the breaker closed and confirm it opens

The manual trip mechanism is verified by manually actuating it while the breaker is in the closed position and confirming the breaker opens as designed.

Plug-in busway is distinguished from feeder busway primarily by which characteristic?

Answer: Plug-in busway has tap-off openings at regular intervals for branch circuit connections; feeder busway does not

Plug-in busway includes tap-off openings spaced at regular intervals (e.g., every 2 feet) to allow branch circuit plug-in units to be inserted; feeder busway is a straight run without tap-off provisions.

After completing a switchgear maintenance outage, which of the following must be verified before re-energizing?

Answer: All tools, materials, and personnel are clear and all safety grounds are removed

Before re-energizing, it must be confirmed that all personnel are clear, all tools and materials are removed, and all temporary safety grounds have been removed.

What is the significance of the 'close and latch' rating on a circuit breaker in the context of switchgear fault interruption?

Answer: The maximum fault current the breaker can close into and remain latched closed without welding its contacts

The 'close and latch' rating specifies the peak fault current the breaker can close onto and mechanically latch without the contacts welding together.

During infrared scanning of energized switchgear, which condition requires the most immediate corrective action?

Answer: A 50°C rise on a cable lug termination compared to adjacent cables

A 50°C temperature rise on a cable lug termination indicates severe connection degradation and an imminent failure risk requiring immediate action.

What test is used to verify that the primary injection current through a switchgear current transformer accurately matches the secondary output per the nameplate ratio?

Answer: Current transformer ratio (turns ratio) test

A current transformer ratio test applies a known primary current and measures secondary output to confirm the CT is performing to its nameplate ratio.