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also, the industry standard for office type buildings is 277/480 Y with most of the lighting circuits being 277 1 phaseWe have no idea where the OP is from and it makes it tough sometimes to create an answer to certain questions/
In the US, there is a 208V 3 phase Y system and a 240 V, 3 phase High LEG Delta system See: https://www.ridgidforum.com/forum/t40742/
Resisdential is typically a split-phase 240/120 which is called single phase. The residence is suppled from a center-tapped 240 VAC transformer. The CT is grounded.