three-phase seven-wire system

three-phase seven-wire system

[′thrē ¦fāz ′sev·ən ¦wīr ′sis·təm]
(electricity)
System of alternating-current supply from groups of three single-phase transformers connected in Y to obtain a three-phase, four-wire grounded neutral system of higher voltage for power, the neutral wire being common to both systems.