Several small busbars on the high-voltage switchgear

High-voltage switchgear contains small busbars such as branch, auxiliary, and flexible busbars that connect main busbars to circuit breakers, feeders, and control devices.

Overview of Small Busbars

In high-voltage switchgear, small busbars are used to distribute power from the main busbars to individual circuits or equipment. Unlike the main busbars, which carry the full system current, small busbars handle lower currents and are often used for:

• Branch busbars: Connect the main busbar to outgoing feeders or circuit breakers, allowing power to be distributed to specific loads or sections of the network .
• Auxiliary busbars: Supply control circuits, protection relays, and instrumentation within the switchgear, typically carrying very low currents .
• Flexible busbars: Made from braided copper or laminated thin layers, these accommodate movement, vibration, or thermal expansion, often connecting moving parts like draw-out circuit breakers to the main bus .

Design and Material Considerations

Small busbars are usually copper or aluminum, with copper preferred for high reliability and compact installations due to its superior conductivity and mechanical strength . They can be:

• Flat or rectangular: Provides good heat dissipation and ease of connection.
• Tubular or hollow: Reduces weight and improves cooling in compact designs.
• Insulated or bare: Insulated busbars allow tighter spacing and reduce short-circuit risk, while bare busbars rely on proper spacing and supports .

Function in High-Voltage Switchgear

Small busbars serve as intermediate conductors, linking the main busbars to:

• Incoming and outgoing circuit breakers
• Feeder connections
• Control and protection devices They ensure safe, reliable power distribution while allowing flexibility for maintenance, sectionalizing, and future expansion . Their smaller size compared to main busbars is sufficient for the lower current they carry, and their design must account for thermal performance, mechanical strength, and insulation requirements.

Summary

In high-voltage switchgear, small busbars are essential for connecting main busbars to branch circuits, auxiliary systems, and moving components. They are typically made of copper or aluminum, can be flat, tubular, or flexible, and may be insulated or bare depending on safety and space requirements. Proper design ensures reliable operation, thermal stability, and ease of maintenance .