tripping the main generator breaker 11kv due to transformer inrush current

Zoubi...
In 1973, I was called to a refinery to participate in the investigation of a problem similar to yours.
They had finished "turnaround" on lineup of MV switchgear. It included checking contacts, cables, wiring, and connections of both 6.3-kV Power and 24-Vdc Control circuits, inside the Cubicles and Carriages.
Upon startup, a problem, similar to yours, appeared! Closure of the either adjacent Brkr, tripped the Tie-Brkr!
Discovery wasn't easy, But the solution was quick... Another Brkr was installed.
The problem was caused by loose control connections in its Carriage wiring! The impact of closure of either adjacent Brkr was enough to cause a normally Closed-circuit to Open-circuit in the Tie-Brkr's control wiring!
Regards, Phil Corso
 
Why not simply post the SLD identifying the protection scheme (with there settings inclusive of CT ratios and polarity) along with the parameters of gen set and Transformer, then an analysis can be done. The issue is a coordination one which can be easily solved.
 
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