Bus duct

Originally a busway consisted of bare copper conductors supported on inorganic insulators, such as porcelain, mounted within a non-ventilated steel housing.

[2] Some bus ducts are rectangular similar to cable tray, but have thicker, cold-formed steel side rails and thinner sheet metal coverings.

Typically, individual busbars are wrapped or coated with a non-conducting, covalent material, such as plastic or (in older systems) electrical tape.

A plug-in bus duct system or busway can have disconnect switches and other devices mounted on it, for example, to distribute power along a long building.

A variant type is a low-impedance busway, which is designed to have lower voltage drop by virtue of close spacing of bus bars, which reduces inductive reactance.