RRaghunath,
Indeed we need over frequecy protection primarily for prime mover protection. However as edison has told, this will also have role while synchronising at higher frequencies. This I have ssen particularly in eastern grids in India.
The desicion to trip which CB is debatable. If...
Sngpl,
What I meant by open delta configuration - PTs with two windid only on HV and LV. HV side both wdgs connected in series - voltages are applied at one phase at each end of wdg (A&C) at middle pt third phase (B). Secondary too is connected in similar way but middle point is grounded...