During a routine inspection of a main generator output breaker, a technician discovers severely damaged main contact surfaces.
Which one of the following is the most likely cause of the damaged contact surfaces?
A. The main generator breaker automatically tripped open after it was closed with the generator and power grid voltages 60 degrees out of phase.
B. The main generator breaker automatically tripped open due to a faulty trip relay actuation while the main generator was operating unloaded.
C. The main generator breaker automatically tripped open on a loss of offsite power while the main generator was operating at its maximum rated load.
D. The main generator breaker automatically tripped open after it was closed with the generator and power grid voltages in phase but with generator frequency 0.2 Hz lower than power grid frequency.
Show Answer
Answer: A
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