Read the regulator rating correctly
The reference table pairs 13.8 kV and 200 A with a 276 kVA regulation rating. The single-phase through-load apparent power at that operating point is 2,760 kVA; the two figures describe different duties. Do not size a feeder by the regulation-kVA label alone.
Check connection, insulation and current together. A three-phase bank also needs an agreed connection and control strategy; it is not defined by ordering three identical cans.