It depends on your system. If this is a distribution system with single phase loads or has fairly long feeders, it should be solidly grounded. Actually, if you have single-phase (line-to-neutral) loads it has to be solidly grounded. A utility-type 33 kV distribution system is normally solidly grounded to provide sufficient ground fault current to clear faults that are remote from the substation.
If this is an industrial facility, you will want some type of resistance grounding to limit fault current.
