vahid
it seems that u have a big problem in signal interfaces between MV and LV feeder. according to this type of systems there should be an inter lock between upstream and downstream CB. if the MV CB trip or open in any reason the lv CB should be open too .
in some circuit we have direction relay in LV sides that will be tripped LV CB in some situation like this.
but in any case u should have lockout relay for Deferential protection . in this case the trip will not reset .