Busbar
Overview
 
In electrical power distribution, a bus bar is a strip of copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 or aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

 that conducts electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

 within a switchboard
Electric switchboard
An electric switchboard is a device that directs electricity from one source to another. It is an assembly of panels, each of which contains switches that allow electricity to be redirected. The U.S...

, distribution board
Distribution board
A distribution board is a component of an electricity supply system which divides an electrical power feed into subsidiary circuits, while providing a protective fuse or circuit breaker for each circuit, in a common enclosure...

, substation
Electrical substation
A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions...

 or other electrical apparatus.

The size of the bus bar determines the maximum amount of current that can be safely carried. Bus bars can have a cross-sectional area of as little as 10 mm2 but electrical substation
Electrical substation
A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions...

s may use metal tubes of 50 mm in diameter (1,963 mm2) or more as bus bars.
Encyclopedia
In electrical power distribution, a bus bar is a strip of copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 or aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

 that conducts electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

 within a switchboard
Electric switchboard
An electric switchboard is a device that directs electricity from one source to another. It is an assembly of panels, each of which contains switches that allow electricity to be redirected. The U.S...

, distribution board
Distribution board
A distribution board is a component of an electricity supply system which divides an electrical power feed into subsidiary circuits, while providing a protective fuse or circuit breaker for each circuit, in a common enclosure...

, substation
Electrical substation
A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions...

 or other electrical apparatus.

The size of the bus bar determines the maximum amount of current that can be safely carried. Bus bars can have a cross-sectional area of as little as 10 mm2 but electrical substation
Electrical substation
A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions...

s may use metal tubes of 50 mm in diameter (1,963 mm2) or more as bus bars. An aluminum smelter will have very large bus bars used to carry tens of thousands of amperes to the electrochemical cell
Electrochemical cell
An electrochemical cell is a device capable of either deriving electrical energy from chemical reactions, or facilitating chemical reactions through the introduction of electrical energy. A common example of an electrochemical cell is a standard 1.5-volt "battery"...

s that produce aluminum from molten salts.

Design and placement

Bus bars are typically either flat strips or hollow tubes as these shapes allow heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...

 to dissipate more efficiently due to their high surface area
Surface area
Surface area is the measure of how much exposed area a solid object has, expressed in square units. Mathematical description of the surface area is considerably more involved than the definition of arc length of a curve. For polyhedra the surface area is the sum of the areas of its faces...

 to cross-sectional
Cross section (geometry)
In geometry, a cross-section is the intersection of a figure in 2-dimensional space with a line, or of a body in 3-dimensional space with a plane, etc...

 area ratio.
The skin effect
Skin effect
Skin effect is the tendency of an alternating electric current to distribute itself within a conductor with the current density being largest near the surface of the conductor, decreasing at greater depths. In other words, the electric current flows mainly at the "skin" of the conductor, at an...

 makes 50–60 Hz
Utility frequency
The utility frequency, line frequency or mains frequency is the frequency at which alternating current is transmitted from a power plant to the end-user. In most parts of the world this is 50 Hz, although in the Americas it is typically 60 Hz...

 AC
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....

 bus bars more than about 8 mm (1/3 in) thick inefficient, so hollow or flat shapes are prevalent in higher current applications. A hollow section has higher stiffness than a solid rod of equivalent current-carrying capacity, which allows a greater span between busbar supports in outdoor switchyards.

A bus bar may either be supported on insulators, or else insulation may completely surround it. Bus bars are protected from accidental contact either by a metal earthed enclosure or by elevation out of normal reach. Neutral
Ground and neutral
Since the neutral point of an electrical supply system is often connected to earth ground, ground and neutral are closely related. Under certain conditions, a conductor used to connect to a system neutral is also used for grounding of equipment and structures...

 bus bars may also be insulated. Earth
Ground and neutral
Since the neutral point of an electrical supply system is often connected to earth ground, ground and neutral are closely related. Under certain conditions, a conductor used to connect to a system neutral is also used for grounding of equipment and structures...

 bus bars are typically bolted directly onto any metal chassis of their enclosure. Busbars may be enclosed in a metal housing, in the form of bus duct or busway, segregated-phase bus, or isolated-phase bus
Isolated-phase bus
In electrical engineering, isolated-phase bus , also known as Phase-isolated Bus in some countries, is a method of construction for circuits carrying very large currents, typically between a generator and its step-up transformer in a steam or large hydroelectric power plant.Each phase current is...

.

Bus bars may be connected to each other and to electrical apparatus by bolted, clamp, or welded connections. Often joints between high-current bus sections have matching surfaces that are silver-plated to reduce the contact resistance. At extra-high voltages (more than 300 kV) in outdoor buses, corona
Corona discharge
In electricity, a corona discharge is an electrical discharge brought on by the ionization of a fluid surrounding a conductor that is electrically energized...

around the connections becomes a source of radio-frequency interference and power loss, so connection fittings designed for these voltages are used.

Bus bars are typically contained inside switchgear, panelboards, or busway. 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 the main supply at one location, they allow new circuits to branch off anywhere along the route of the busway.

Etymology

The word “bus” comes from a shortened version of “omnibus”, the Latin word that roughly means “all in one”.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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