السلام عليكم ورحمة الله وبركاته
Two generators 10.5 kV are connected to a bus bar(33 kV)
through block delta/star transformers 10.5 / 33 kv
with the star side earthed through 250 ohm
A circuit breaker is installed at the 10.5 and 33 kV sides
One generator was in operation (i.e 10.5 and 33 kV breakers closed) and producing 40MW.
The other generator was in stand by (10.5 kV breaker opened while 33kV breaker closed)
An earth fault occured on the busbar and the in operation Generator sensed the fault through directional earth fault relay installed at the 33 kV side and tripped the 33 and 10.5 breakers.
The question is: Why for the stand by generator, it also sensed the fault and tripped the 33kV breaker, when it was not in operation and did not feed the fault
please explain if this have a relation to the fact that the block transformer at the 33kV side is star and earthed.
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السلام عليكم ورحمة الله وبركاته
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