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.

Answer Posted / k.prakashchandra

There is a loose connection in one of the phases of OLTC
contacts.

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