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In Electric power distribution, a busbar also called bus bar, buss bar or busbar, which is a metallic strip or bar, typically housed inside switchgear, panel boards, and busway enclosures for local high current power distribution.

The busbar also used to connect high voltage equipment at electrical switchyards, and low voltage equipment in battery banks. The bus bar is generally uninsulated, and has sufficient stiffness to be supported in air by insulated pillars. These features allow sufficient cooling of the conductors, and the ability to tap in at various points without creating a new joint.

The material composition and cross-sectional size of busbar determine the maximum amount of current that can be safely carried. Busbars can have a cross-sectional area of as little as 10 square millimeters (0.016 sq inch), but electrical substations may use metal tubes 50 millimeters (2.0inch) in diameter (20 square millimeters or 0.031 SQ inch) or more as busbars.

An aluminum smelter will have very large busbars used to carry tens of thousands of emperes to the electrochemical cells that produce aluminum from molten salts.

Busbars are produced in a variety of shapes such as flat strips, solid bars and rods typically copper, brass or aluminum in solid or hollow tubes.

Some of these shapes allow heat to dissipate more efficiently due to their high surface area to cross-sectional area ratio. The skin effect makes 50-60 Hz AC busbars more than about 8 millimeters(0,31inch) thickness inefficient, so hollow or flat shapes are prevalent in higher current applications. A hollow section also has higher stiffness than a solid rod of equivalent current-carrying capacity, which allows a greater span between busbar supports in outdoor electrical switchyards.

A busbar must be sufficiently rigid to support its own weight, and forces imposed by mechanical vibration and possibly earthquakes, as well as accumulated precipitation in outdoor exposures. In addition, thermal expansion from temperature changes induced by ohmic heating and ambient temperature variations, and magnetic forces induced by large currents must be considered.

Distribution boards split the electrical supply into separate circuits at one location. Busways, or bus ducts, are long busbars with a protective cover. Rather than branching from the main supply at one location, they allow new circuits to branch off anywhere along the route of the busway.

A busbar may either be supported on insulators, or else insulation may completely surround it. Busbars are protected from accidental contact either by a metal earthed enclosure or by elevation out of normal reach. Power neutral busbar may also be insulated because it is not guaranteed that the potential between power neutral and safety grounding is always zero.

Earthing (Safety grounding) busbars are typically bare and bolted directly onto any metal chassis of their enclosure. Busbar may be enclosed in a metal housing, in the form of bus duct or busway, segregated-phase bus, or isolated-phase bus.