Three Phase Distribution Lines

Three-Phase Line Picture 1 Electricity leaves most distribution substations on three phase distribution lines. They typically are run along major streets, especially in commercial and industrial areas where there is a large need for three phase electrical service. Rather than run a separate three phase distribution line from the substation for each street in a commercial or industrial development, it is a common practice to "tap" off new lines from the main line wherever needed.

Three-Phase Line Picture 2Distribution lines can be connected as three-phase "wye" or three-phase "delta" lines. The names describe the configuration in which the three phases are connected together. The "Wye" connection resembles the shape of the letter "Y" and the Delta resembles the shape of a triangle. They don't necessarily physically look like this, but are simply interconnected in such a way as to make the "wye" or "delta" shorthand nomenclature applicable. Voltages and currents are different between wye and delta systems. Wye and delta systems also have different characteristics which make them applicable to different distribution situations.