When we change the tap position of 10MVA transformer it
suddenly tripped with Out of step indication and also with
Static differential relay indication, Transformer Bucholz
relay indn and Low oil level indication. Before 1 week the
same problem occured by changing the tap position. but at
that time only oltc bucholz relay activated. After testing
the TxR Relay team & PET team cant find any solid reason.
The values are ok also. So plz answer wat's the reason for
this incident? anybody plz help.
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Answer Posted / k.prakashchandra
OLTC has contact switches on rotating spindle and diverter
switch. Bucholtz relay acts as the oil is burnt in the
chamber due to arcing caused by loose contact .The spring
tension of the switches are to be checked for correct
tightness.If the contact is not correct ,the differential
relay may also act due to imbalance of currents.Do not
operate OLTC till the fault is set right.And the oil may
have to reconditioned.
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