Upper Float Alarm

Correct Answer

B — It closes the alarm circuit when the oil level drops

Explanation

Slow internal faults generate gas that accumulates in the Buchholz chamber and displaces oil, causing the upper float to fall. The upper-float mercury switch then closes the alarm circuit; severe oil surge operates the trip element.

Key Concept

Upper Float Alarm

Exam Point

Buchholz: upper float = alarm; lower/surge element = trip.

Common Mistake

Alarm operation is associated with the float falling as gas accumulates, not rising.