| Electrical installations |
|---|
| Wiring practice by region or country |
| Regulation of electrical installations |
| Cabling and accessories |
| Switching and protection devices |
Inelectric power distribution, abus duct (also calledbusway) typically usessheet metal, welded metal[1] or cast resin to contain and isolatecopper oraluminiumbusbars for the purpose of conducting a substantialcurrent of electricity. It is an alternative means of conducting electricity topower cables or cable bus.
Originally abusway consisted of barecopperconductors supported on inorganic insulators, such asporcelain, mounted within a non-ventilated steel housing.[2]
Busways were produced due to request of the automotive industry in Detroit in the late 1920s. Since that time, busways improved and became an integrated part ofsecondary network for industrial plants.[2]
Some bus ducts are rectangular similar tocable tray, but have thicker,cold-formed steel side rails and thinnersheet metal coverings. Others can be circular.[3] Busbars inside may be separated with distinct and even gaps between them, or “sandwiched” together.
Typically, individual busbars are wrapped or coated with a non-conducting,covalent material, such asplastic or (in older systems)electrical tape.
At the connection point, busbars flare out to enable connection to the next segment.
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. Many forms of busway allow plug-in devices such as switches and motor starters to be easily moved; this provides flexibility for changes on an assembly line, for example.[4] In addition to powering floor fixtures, busways can provide power to plug-in light fixtures and even IoT devices.[5]
Feeder busway is used to interconnect equipment, such as between a transformer and a switchgear line up. 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.
A trolley busway provides power to equipment that must be frequently moved. The busway is open at the bottom, and a movable collector assembly "trolley" is used to connect between the fixed bus bars in the busway and the cable connected to moving equipment.[4]Bus ducts are building servicepenetrants that are required to be externallyfirestopped where they penetrate fire separations required to have afire-resistance rating.
