Three-Phase Wiring Schemes:
Unlike the single-phase wiring scheme which must make a provision for a neutral leg and separate ground, the three-phase system needs neither a separate neutral nor a ground to operate safely.
Therefore, to avoid any unsafe condition, all 3- and 4-wire, three-phase systems could involve an effective ground path. As with the past single-phase discussion, just the secondary side of the transformer and its connected load required to be studied.