What are the small busbars on the top of the high-voltage switchgear

Small busbars in high-voltage switchgear are typically branch or auxiliary busbars used to connect individual circuits, breakers, or auxiliary equipment, often designed for lower current than the main bus.

Overview

In high-voltage switchgear, small busbars serve as secondary or branch conductors that distribute power from the main bus to individual circuit breakers, transformers, or auxiliary devices. Unlike the main busbars, which carry the full system current, small busbars handle lower currents and are often used for tapping points, control circuits, or interconnections within the switchgear assembly .

Types and Materials

• Rigid busbars: Solid copper or aluminum bars, providing mechanical stability and reliable current flow. Small rigid busbars are often used for branch connections where movement is minimal .
• Flexible busbars: Made from braided copper or laminated thin layers, these are used where vibration, thermal expansion, or movement occurs, such as connections to breakers or auxiliary circuits .
• Flat or laminated busbars: Flat copper strips or laminated conductors with insulation between layers are used in compact designs to save space and improve cooling .
• Insulated or enclosed busbars: Small busbars may be insulated to reduce short-circuit risk and allow tighter layouts inside the switchgear panel .

Design Considerations

• Current rating: Small busbars are sized according to the branch circuit current, which is lower than the main bus. Material choice (copper or aluminum) affects cross-sectional area and thermal performance .
• Thermal management: Flat or hollow shapes improve heat dissipation, preventing overheating in confined switchgear spaces .
• Mechanical support: Small busbars are supported by insulated pillars or brackets to maintain spacing and prevent electrical faults .
• Integration: They connect the main bus to outgoing feeders, breakers, or auxiliary equipment, forming part of the overall power distribution and protection scheme .

Applications

• Branch circuits: Distribute power from the main bus to individual feeders or transformers.
• Control and auxiliary circuits: Supply power to relays, meters, or control devices.
• Compact switchgear designs: Laminated or insulated small busbars allow high-density layouts without compromising safety or performance . In summary, small busbars in high-voltage switchgear are essential for distributing power to secondary circuits and auxiliary equipment, designed with appropriate materials, shapes, and insulation to ensure safe, reliable, and compact operation within the switchgear assembly .