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Cross section of busbar is
Rectangular
Circular
Triangular
Both (a) and (b)
Both (a) and (b)
Busbars are metallic strips or bars used in electrical switchgear to collect and distribute electric power. They are designed with various cross-sections, most commonly rectangular or tubular (circular), depending on the current capacity, mechanical strength requirements, and heat dissipation needs.
Busbars are metallic strips or bars used in electrical switchgear to collect and distribute electric power. They are designed with various cross-sections, most commonly rectangular or tubular (circular), depending on the current capacity, mechanical strength requirements, and heat dissipation needs.
RacтАЛ=RdcтАЛ├Ч(1+k) тАФ where k is the factor representing skin effect and is lower for circular conductors
I=J├ЧA тАФ where I is current, J is current density, and A is the cross-sectional area
The shape of a busbar influences its current-carrying capacity, skin effect, and mechanical rigidity. Rectangular bars provide a large surface area for heat dissipation, making them suitable for high current low-voltage applications. Circular or tubular conductors are preferred for extra high voltage (EHV) applications to reduce the skin effect and minimize corona discharge losses.
Rectangular busbars offer ease of making bolted joints and tap-offs.
Tubular busbars have high mechanical strength and are used in outdoor substations to span longer distances between supports.
Selection depends on current ratings, short-circuit force withstand capability, and skin effect considerations.
At higher frequencies or high current, the skin effect becomes significant, influencing conductor geometry choice.
Rectangular: Excellent thermal radiation properties due to large surface area.
Circular/Tubular: Superior mechanical rigidity against electromagnetic forces during short circuits.
Rectangular: Higher skin effect resistance at high frequencies.
Circular/Tubular: More complex to drill and bolt compared to flat surfaces.
Rectangular: Indoor switchgear panels, distribution boards.
Circular: Outdoor switchyards, EHV substations.
| Feature | Rectangular | Circular |
|---|---|---|
Skin Effect | Higher | Lower |
Mechanical Strength | Moderate | High |
Busbar material is usually copper or aluminium based on cost and conductivity requirements.
Option C (Triangular) is not a standard shape for power transmission busbars, though it may exist in niche structural applications.
D is correct тАФ Busbars are manufactured in both rectangular and circular (tubular) cross-sections depending on the specific application requirements like current rating and mechanical strength.
Always remember that in high voltage systems, circular or hollow-tubular shapes are used to mitigate corona discharge, which occurs more sharply at the edges of rectangular conductors.