By Brian McDivitt, PE

Building power distributions are based on what electrical service the local utility company provides. In the United States, building power distributions are categorized in three main configurations. The first distinction is between single-phase and three-phase, with three-phase further distinguished as wye (Y) or delta (Δ).

Editor’s Note: This is the first in a three-part series on power distribution systems. Read part one and part three.

As described under Part 1, voltage is measured as line-to-line (VLL) or line-to-neutral (VLN). These designations will be used here.