Hubbry Logo
BusbarBusbarMain
Open search
Busbar
Community hub
Busbar
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Busbar
Busbar
Busbar
View on Wikipedia
from Wikipedia
Copper busbar in a panel
1500 ampere copper busbars within a power distribution rack for a large building
Part of a series on
Power engineering
Electric power conversion
Electric power infrastructure
Electric power systems components

In electric power distribution, a busbar (also bus bar) is a metallic strip or bar, typically housed inside switchgear, panel boards, and busway enclosures for local high current power distribution, transmission, or switching substations at voltages up to 345 kV. They are also used to connect high voltage equipment at electrical switchyards, and low-voltage equipment in battery banks. They are generally uninsulated, and have sufficient stiffness to be supported in air by insulated pillars. Those features allow sufficient cooling of the conductors, and the ability to tap in at various points without having to create a new joint.

Design and placement

[edit]

The busbar's material composition and cross-sectional size determine the maximum current it can safely carry. Busbars can have a cross-sectional area of as little as 10 square millimetres (0.016 sq in), but electrical substations may use metal tubes 50 millimetres (2.0 in) in diameter or more as busbars. Aluminium smelters use very large busbars to carry tens of thousands of amperes to the electrochemical cells that produce aluminium from molten salts.

Busbars are produced in a variety of shapes, including flat strips, solid bars and rods, and are typically composed of copper, brass or aluminium as solid or hollow tubes.[1] 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 millimetres (0.31 in) 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. To address these concerns, flexible bus bars, typically a sandwich of thin conductor layers, were developed. They require a structural frame or cabinet for their installation. Mechanical forces generated by fault currents, which can momentarily reach hundreds of thousands of amperes, must also be considered.

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

A busbar may be either supported on insulators, or wrapped in insulation. They are protected from accidental contact either by a metal earthed enclosure or by elevation out of normal reach.[2] Insulated bus bars are used in busways listed to UL 857 standards.[3] Power neutral busbars 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. They may be enclosed in a metal housing, in the form of a bus duct or busway, segregated-phase bus, or isolated-phase bus.

Busbars may be connected to each other and to electrical apparatus by bolting, clamping or welding. Joints between high-current bus sections often have precisely machined matching surfaces that are silver-plated to reduce contact resistance. At extra high voltages (more than 300 kV) in outdoor buses, corona discharge around the connections becomes a source of radio-frequency interference and power loss, so special connection fittings designed for those voltages are used.

See also

[edit]
  • Bus (computing) – Data transfer channel connecting parts of a computer
  • Bus duct – Low resistance electrical conductor for high current transmission and distribution
  • Electrical busbar system – Modular approach to electrical wiring
  • Jumper (computing) – Short length of conductor
  • Wire bridge – Short length of conductor

References

[edit]

Further reading

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Busbar

View on Grokipedia
from Grokipedia
A busbar, also spelled bus bar, is a metallic conductor or assembly of conductors, typically in the form of a strip, bar, tube, or rod, designed to collect electrical current from incoming feeders and distribute it to outgoing circuits with minimal energy loss and high efficiency. It serves as a central junction in power systems, enabling the connection of multiple electrical circuits in a compact and reliable manner. Busbars are fundamental components in , widely used in substations, , distribution panels, and industrial power systems to handle high currents ranging from hundreds to thousands of amperes. The most common materials are and aluminum, chosen for their excellent electrical conductivity; offers superior performance but higher cost, while aluminum provides a cost-effective alternative with adequate conductivity for many applications. To enhance , busbars are often plated with tin or silver to resist oxidation and , and they may incorporate insulation materials like or for safety in high-voltage environments. Key types of busbars include rigid busbars, which are fixed and suitable for high-voltage substations, and flexible or strain busbars (often cable-based) that accommodate movement or in dynamic installations. Other configurations encompass flat strips for space-efficient designs, bars for maximum current capacity, and tubular shapes for better cooling and reduced at high frequencies. Busbar arrangements in systems can vary, such as single bus, double bus, or ring bus schemes, each optimized for reliability, maintenance, and in power distribution. In applications, busbars facilitate efficient power transfer in scenarios like generator docking stations, load banks, and control panels, outperforming traditional cabling by offering lower resistance, better heat dissipation, and simpler scalability for heavy-duty loads. Their considers factors like , minimization, and thermal management to ensure safe operation under varying electrical stresses.

Overview

Definition and Function

A busbar is a metallic strip, bar, tube, rod, or assembly of conductors used as a conductor in electrical power systems to carry and distribute high currents efficiently. Typically constructed from or aluminum, it serves as a foundational element in , distribution panels, and substations for routing electrical power. The primary function of a busbar is to act as a common connection point for multiple circuits, facilitating the collection of from incoming sources and its distribution to outgoing loads with minimal . This role enables centralized power management, allowing efficient transfer of substantial electrical loads across systems while reducing the complexity of wiring. Key characteristics of busbars include high electrical conductivity and low resistance, which enable them to handle large amperages ranging from hundreds to thousands of amps without significant energy loss or overheating. Rigid busbars provide mechanical stability, making them suitable for fixed installations in high-power environments. Busbars originated in early practices of the late , developed to support centralized power routing in emerging electrical grids and distribution systems.

Basic Electrical Principles

Busbars operate under fundamental electrical principles that dictate their in conducting high currents with minimal losses. , expressed as V=IRV = IR, where VV is voltage, II is current, and RR is resistance, governs the relationship between these parameters in busbar systems. In busbar design, minimizing resistance RR is critical to reduce voltage drops and associated heat generation, ensuring stable power distribution over distances. Current density, defined as J=I/AJ = I / A with II as current and AA as cross-sectional area, quantifies the current per unit area in a conductor. For busbars, maintaining appropriate current density prevents excessive heating; typical values for copper busbars range from 1 to 2 A/mm², depending on cooling conditions, to avoid overheating and maintain operational integrity. Exceeding these limits can lead to thermal runaway, underscoring the need for sizing based on this principle. In alternating current (AC) applications, the skin effect influences current distribution, causing AC to concentrate near the conductor's surface rather than uniformly throughout, due to opposing magnetic fields induced by the changing current. This phenomenon increases effective resistance at higher frequencies, prompting busbar designs that optimize surface area for efficient current flow and reduced losses. The effect is negligible in direct current (DC) but significant in AC systems operating at 50-60 Hz or above. Power losses in busbars primarily arise from resistive heating, calculated using the formula P=I2RP = I^2 R, where power dissipation PP scales quadratically with current. This equation highlights why busbars, with their low resistance, are favored for high-power scenarios: even small reductions in RR yield substantial decreases in losses, improving overall system efficiency and preventing energy waste as heat. In high-current environments, such losses can otherwise compromise performance and require enhanced cooling.

History

Early Development

The concept of busbars originated in the late amid the rapid expansion of electrical power systems, coinciding with the development of both (DC) and (AC) technologies for urban . As power generation scaled beyond small-scale dynamos, engineers recognized the need for efficient, high-current conductors to replace cumbersome bundles of individual wires, enabling centralized distribution from generators to loads. This shift was driven by the electrification boom following the , when central stations began supplying to growing cities. A pivotal early implementation occurred at Thomas Edison's in , which commenced operations on September 4, 1882, as the world's first commercial central power plant. The station employed double half-round bars as main busbars to connect the six DC generators—each rated at 100 kW—to the distribution network, facilitating the delivery of 110 volts to approximately 400 lamps across a one-square-mile district. These busbars, constructed from solid for superior conductivity, marked a practical innovation in handling the station's initial capacity of 600 kilowatts. The station operated until a destroyed it on January 2, 1890, underscoring Edison's focus on reliable, underground DC distribution to commercial and residential customers. Key figures in this era included , who championed DC systems through his Edison Electric Illuminating Company, and , whose AC polyphase inventions—patented in 1888 and acquired by —addressed the limitations of DC for long-distance transmission. Westinghouse's adoption of Tesla's designs led to the first practical plants, such as the 1893 demonstration at the Chicago World's Fair, where busbars played a crucial role in scaling power delivery by interconnecting transformers and feeders more effectively than wire assemblages. These contributions by Edison, Tesla, and Westinghouse transformed busbars from station components into essential elements for accommodating surging electrical demands in industrial and urban settings. Initial applications centered on power plants and street lighting systems, where busbars enabled the management of increasing loads during the post-1880s boom. In Edison's network, they supported the station's expansion to serve 508 customers with 10,164 lamps by 1884, while Westinghouse's AC installations powered early arc and incandescent streetlights in cities like Buffalo and , distributing current from generators to multiple circuits without excessive . Early busbar designs relied on uninsulated bars mounted on insulators, which were effective for conductivity but vulnerable to arcing due to exposed surfaces and environmental factors like or . This susceptibility prompted initial enhancements in the early , including better spacing, enclosures, and the introduction of insulation wraps to mitigate faults in high-current environments.

Modern Evolution

Following , busbar technology advanced significantly to meet growing industrial demands for efficient power distribution. By the mid-20th century, aluminum busbars gained prominence as a cost-effective alternative to , leveraging aluminum's lower material costs and lighter weight to reduce installation expenses while maintaining adequate conductivity for medium-voltage applications. By the , insulation emerged as a key innovation, enabling more compact busbar designs by providing robust dielectric protection in confined spaces, particularly in where space efficiency was critical. The marked a period of standardization, with the (IEC) establishing guidelines for busbar connectors and high-voltage applications, such as those outlined in early standards like IS/IEC equivalents for connectors, which improved and safety in global power systems. This era laid the groundwork for reliable high-voltage busbar deployment in substations and industrial settings. Entering the 1990s, busbars integrated with modular designs, facilitating scalable power distribution in emerging data centers by allowing customizable configurations that supported rapid expansion and reduced downtime during upgrades. Since the 2000s, flexible busbars, including braided designs, have gained prominence for environments subject to , such as generators and transformers, where their pliability absorbs mechanical stress without compromising electrical integrity. Post-2010, smart busbars with embedded sensors for real-time monitoring of current, temperature, and faults have transformed , integrating IoT capabilities to enhance reliability in dynamic power networks. The rise of sources has further driven busbar evolution, with designs adapted for solar and integration requiring higher current capacities—up to 10,000 A by the 2020s—to handle variable loads from inverters and storage systems efficiently. These advancements support grid stability amid increasing renewable penetration, emphasizing modular and high-capacity configurations.

Materials and Construction

Common Materials

Busbars are primarily constructed from or aluminum due to their favorable electrical properties. offers superior electrical conductivity at approximately 58 MS/m, enabling efficient current carrying with smaller cross-sections, though it is denser and more costly. Aluminum, with a conductivity of about 37 MS/m—roughly 61% that of —requires larger cross-sections to achieve equivalent performance but is significantly lighter (about one-third the weight of ) and less expensive, making it suitable for weight-sensitive applications. To enhance durability, busbars often incorporate alloys and protective coatings. Copper-tin alloys, such as tin bronzes, provide improved resistance while maintaining good conductivity and compared to pure . Silver is commonly applied to contact points on copper busbars to minimize and prevent oxidation, ensuring stable performance in high-current environments. Tin serves as an alternative coating, offering effective protection and at a lower cost than silver, particularly in humid conditions. Material selection balances cost against performance requirements, including and mechanical compatibility. Copper's higher price and weight may favor aluminum in large-scale installations where space allows for increased dimensions, but excels in compact, high-reliability setups. differences are critical for joint integrity: has a coefficient of 17 × 10⁻⁶/°C, versus 23 × 10⁻⁶/°C for aluminum, influencing design to accommodate differential expansion under load. Environmental factors increasingly guide material choices, emphasizing and compliance. Both and aluminum are highly recyclable, with aluminum's infinite recyclability reducing energy demands and emissions in production. Since the RoHS Directive's implementation in 2006, lead-based solders have been avoided in busbar assemblies to limit hazardous substances, promoting safer, eco-friendly electrical systems.

Manufacturing Techniques

Busbars are typically manufactured starting from raw metal billets or ingots of or aluminum, which are processed through a series of forming, assembly, and finishing steps to achieve the desired electrical and mechanical properties. The primary shaping methods focus on creating uniform cross-sections suitable for high-current conduction, followed by assembly techniques to form complex configurations, insulation for safety, and rigorous testing to ensure reliability. The core fabrication begins with , a process where heated metal is forced through a die to produce continuous lengths of busbar with precise rectangular or custom profiles, commonly used for both and aluminum to ensure consistent dimensions and surface quality. Rolling follows to refine the extruded stock into thinner sheets or bars, improving uniformity and reducing thickness variations, while drawing pulls the material through dies for further dimensional accuracy and enhanced surface finish, particularly for round or smaller cross-sections. Once shaped, busbars are assembled using joining techniques tailored to maintain electrical integrity and structural strength. Bolting provides a simple, removable connection by threading holes and securing with fasteners, ideal for modular systems. , such as inert gas (TIG) for , creates permanent, low-resistance joints by melting the with a non-consumable in an inert atmosphere, minimizing oxidation and ensuring high conductivity. Crimping compresses connectors onto the busbar ends for secure, vibration-resistant terminations without heat-affected zones. Insulation is applied post-assembly to prevent short circuits and enhance , often via dipping the preheated busbar (typically 320–370°C) into molten or PVC powder, which adheres uniformly and cures to a thickness exceeding 0.12 inches for high-voltage applications. Alternatively, molding techniques coat the busbar with powder in a or use overmolding for complex shapes, providing and corrosion resistance. Quality control involves non-destructive and mechanical tests to verify performance. Conductivity is assessed using the four-point probe method, where current is applied through outer probes and voltage measured across inner ones to determine resistivity accurately, ensuring minimal losses in power distribution. Mechanical strength is evaluated through , targeting values of 200–400 MPa depending on the grade, to confirm the busbar's ability to withstand operational stresses without deformation. Customization enhances busbar functionality for specific installations, with computer numerical control (CNC) used to create precise bends, holes, and cutouts in the formed bars, allowing for compact routing in enclosures. Industrial production scales to handle lengths up to several meters, enabling efficient fabrication of extended runs for large-scale power systems.

Design Considerations

Electrical Design Parameters

The primary electrical design parameter for busbars is the determination of the required cross-sectional area to handle specified load currents without excessive heating. This is calculated using the formula A=IJA = \frac{I}{J}, where AA is the cross-sectional area in mm², II is the continuous load current in amperes, and JJ is the allowable in A/mm². For copper busbars under continuous loads in enclosed installations, a representative value of J=1.5J = 1.5 A/mm² is commonly used to limit temperature rise to 65°C above ambient, though values can range from 1.0 to 2.0 A/mm² depending on ventilation and configuration. Additionally, the mounting orientation affects the permissible continuous current for rectangular busbars; according to the Russian electrical code PUE (Rules for Electrical Installations), mounting on edge allows higher currents compared to flat mounting, with the currents from Tables 1.3.31–1.3.33 reduced by 5% for bars with strip width up to 60 mm and by 8% for widths greater than 60 mm due to differences in heat dissipation. Voltage drop is another critical parameter, ensuring efficient power delivery across the busbar length. The voltage drop ΔV\Delta V is given by ΔV=ρLIA\Delta V = \frac{\rho L I}{A}, where ρ\rho is the material resistivity in Ω·m, LL is the busbar length in meters, II is the current in amperes, and AA is the cross-sectional area in m². For copper at 20°C, ρ=1.68×10−8\rho = 1.68 \times 10^{-8} Ω·m, and design practices typically limit ΔV\Delta V to less than 3% of the nominal voltage for distribution systems to maintain equipment performance. Busbars must also be designed to withstand short-circuit currents without mechanical or thermal failure. The peak short-circuit current IpeakI_{peak} for asymmetrical faults is calculated as Ipeak=Irms2(1+e−t/τ)I_{peak} = I_{rms} \sqrt{2} \left(1 + e^{-t / \tau}\right)
Add your contribution
Related Hubs
User Avatar
No comments yet.