A distribution substation is a part of an electrical generator, transmission, and distribution system. They transform voltage from high to low, or low to high. The term substation comes from the days before the distribution system was a grid. An electrical switchboards is a device on the substation that diverts electricity from one source to another. Its purpose is to divide the current into smaller currents for further distribution, and to provide protection and metering to these various currents. A medium voltage switchgear is located on both the high and low voltage sides of large power transformers.

A bus duct is metal raceway the supports and contains a group of electrical bus bars. A non segregated phase bus is an assembly of bus conductors with associated connections, joints, and insulating supports confined within a metal enclosure without interphase barriers. These would be used in circuits containing a medium voltage switchgear. With a medium voltage switchgear, a non segregated phase bus is capable of carrying rated current continuously without exceeding a conductor temperature rise of 65 degrees above the outside temperature. The bus also needs a siemens bus plug.