Busbars at Connectors sa mga Pag-install ng HV at EHV

Ano ang Electric Busbar?

Ang electric busbar ay isang konduktor o set ng mga konduktor na disenyo para makolekta ang electrical power mula sa mga incoming feeders at ibahagi ito sa outgoing feeders. Sa functional aspect, ito ay naglilingkod bilang isang junction kung saan ang inaasikasong current at outflowing currents ay nagtatagpo, gumagana bilang isang central hub para sa power aggregation at distribution.

Outdoor Busbar Installations

Sa high-voltage (HV), extra-high-voltage (EHV), at outdoor medium-voltage (MV) systems, ang mga bare busbars at connectors ay karaniwang ginagamit, na may mga konduktor na available sa tubular o stranded-wire configurations:

• Tubular Busbars: Suportado ng column insulators (karaniwang ceramic), ito ay nagbibigay ng mataas na mechanical strength at superior corona resistance.

• Stranded-Wire Busbars: Nakakabit sa dead-end clamps, ideal para sa mga installation na nangangailangan ng large-span flexibility.

(Mga halimbawa ng mga itong configuration ay ipinapakita sa Figures 1 at 2.)

Busbars para sa Switchgear Installations

Ang switchgear busbars ay karaniwang gawa sa copper, aluminum, o aluminum alloys (halimbawa, Al-Mg-Si series), na may key characteristics ng mga bare busbars kasama ang:

• Geometric Parameters

• Tubular conductors: Outer diameter at wall thickness

• Stranded wires: Nominal cross-sectional area

• Mechanical Properties

• Tensile/compressive/bending strength

• Buckling resistance

• Section modulus at moment of inertia

• Current-Carrying Capacity

• Rated current: Determined by material resistivity at heat dissipation conditions.Dahil ang mga bare conductors ay umaasa sa air insulation, ang rated voltage ay hindi primary selection criterion.

Busbar Connection Technology

Ang dedicated connectors ay mahalaga para sa pagtapos ng busbars sa equipment, tulad ng ipinapakita sa Figure 3. Ang typical configurations ay kasama ang:

• Bolted connections: Rigid joints secured by torque-controlled bolts, requiring contact resistance management to prevent overheating

• Expansion joints: Compensate for thermal expansion, mitigating structural stress concentrations

• Transition terminals: Address electrochemical corrosion between dissimilar materials (e.g., copper-aluminum interfaces)

Connection design must comply with:

• Contact area standards for temperature rise (e.g., IEC 61439)

• Material compatibility treatments (e.g., tin-plating for copper-aluminum transitions)

• Mechanical stability under short-circuit electro-dynamic forces

Engineering Considerations

Medium/high-voltage switchgear busbar systems require integrated design for:

• Thermal management: Optimized air convection or forced cooling to control temperature rise

• Dynamic stability: Structural integrity under short-circuit electrodynamic forces

• Environmental protection: IP3X or higher ingress protection matching operational environments

These measures collectively ensure reliable power transmission and extended equipment service life.

Widely used in data centers and industrial plants for high-current power distribution, these systems enable flexible layout and easy expansion through modular design.
For copper-copper connections, bronze connectors are used; for aluminium-aluminium connections, aluminium alloy connectors should be applied; and for copper-aluminium connections, bi-metallic connectors are mandatory to prevent corrosion caused by electrolytic effects.
Insulated Busbars & Trunking Systems
In indoor medium-voltage (MV) and low-voltage (LV) installations—particularly where high currents and limited space coexist—busbars are often enclosed in metallic casings for mechanical protection and insulation.This design reduces busbar heat dissipation due to restricted air flow and radiation losses, resulting in current ratings significantly lower than those for free-air installations. Ventilated enclosures can be used to minimize current derating.

Technical Details Analysis

• Electrochemical Protection for Different Material Connections

• Copper-copper joints: Bronze connectors (tin bronze or aluminium bronze) enhance contact reliability via solid solution strengthening, preventing pure copper creep relaxation.

• Aluminium-aluminium joints: 6061-T6 aluminium alloy connectors undergo aging treatment to ensure oxide film stability.

• Copper-aluminium transitions: Bi-metallic connectors use explosive welding or brazing (e.g., copper-aluminium composite bars) to block electrochemical corrosion paths.

• Thermal Management Challenges in Enclosed Busbars
  Thermal resistance analysis: Air gaps formed by enclosures reduce thermal conductivity by 30%-50%.
  Compensation solutions:
  

• Forced air cooling: Internal fans increase current-carrying capacity by 20%-30%.

• Enclosure cooling fins: Enhanced surface area for natural convection.

• High thermal conductivity insulation: Silicone rubber coatings to reduce thermal resistance.

• Engineering Application Specifications
  

• Protection class: Typically IP54 for indoor environments, upgraded to IP65 in humid conditions.

• Short-circuit withstand: Compliant with IEC 61439 dynamic and thermal stability requirements.

• Expansion compensation: Expansion joints every 30-50 meters to accommodate thermal deformation.

Widely used in data centers and industrial plants for high-current power distribution, these systems enable flexible layout and easy expansion through modular design.

Isolated Busbars

Isolated busbars typically consist of copper or aluminium flat bars (one or more per phase, sized according to current requirements), with each phase enclosed in a separately earthed sheath. The sheath ends are connected by short-circuit rated bars capable of carrying full fault currents.The sheath primarily prevents inter-phase short circuits. Additionally, it cancels out magnetic fields generated by conductor currents: an equal and opposite current induced in the sheath neutralizes the electromagnetic field almost completely.Common insulating media include air and SF₆.

LV Busbar Trunking Systems

In low-voltage installations, busbar trunking systems offer a cost-effective solution for power distribution, supplying multiple devices and interconnecting switchboards or transformers, as shown in Figure 5.

Busbar Trunking Systems

A busbar trunking system is a pre-assembled configuration housing flat-bar conductors (phase and neutral) within a single metallic enclosure.In feeder trunking systems, power tap-off is achieved via standardized tap-off units, which connect at predefined positions along the trunking. These units enable power extraction through compatible protective devices.

Advantages Over Cable Systems:

• Cost-Effectiveness & Installation Efficiency

• More economical for high-current applications: Eliminates the need for parallel single-core cables to meet current ratings, voltage drop, and dip requirements.

• Reduces overheating risks: Avoids heat buildup in cable bundles that can lead to short circuits.

• Mechanical Superiority

• Long-span stability: Requires minimal fixings, reducing installation time.

• Eliminates cable support structures: Minimizes metalwork requirements.

• Space & Maintenance Benefits

• Accommodates post-installation power changes (within trunking ratings).

• Enables easy repositioning of distribution points.

• Facilitates system expansion.

• Reduces switchboard termination space.

• Eliminates cable joints: Lowers contact resistance and failure points.

• Flexible tap-off design:

• Additional Advantages

• Aesthetic appeal in visible areas.

• Reusability: Can be dismantled and relocated.

• Enhanced fire resistance: Metal enclosures contain fire spread.