Distributing heavy currents inside equipment, buildings, or switching yards
Electrical trunking systems are used to carry a compound current where various electrical cables come together. Such systems normally consist of a rigid piece of copper, typically flat strips or hollow bars. Although copper is the preferred material for trunking systems, aluminium is occasionally used because of its cheaper initial purchase price, despite significant disadvantages.
The cross-section of a copper trunking system is determined by the maximum current that it must be able to carry safely. It can be as little as 10 mm2 or as large as 2,000 mm2.
Trunking systems are used in various applications. A busbar trunking system is used inside electrical apparatus, inside switchgear or at a power company switching yard. Busways or busducts are used to bring the main power feed into a building or to make connections to large switchgear. A plug-in bus is used to distribute power over the entire length or height of an industrial building.
Busduct phase conductors can run inside the same enclosure (non-isolated bus), they can be separated from each other by a grounded barrier (segregated bus) or they can run inside a separate grounded metal enclosure (isolated-phase bus).
Connections to trunking systems are generally bolted, welded or clamped.