What is a bus-tie breaker and where is it used?

• A. A breaker that connects two bus sections to allow parallel operation or isolation of sections.
• B. A breaker that connects a generator to a bus.
• C. A breaker that protects against ground faults.
• D. A breaker used only in DC systems.

Answer: (A)

A bus-tie breaker is the device that links two bus sections together, allowing them to operate in parallel or to be separated for maintenance or fault isolation. It sits between two sections of a switchyard bus, and when it is closed, power can flow freely between the connected sections, enabling load transfer and shared supply paths. This provides greater reliability because you can reconfigure feeds, transfer loads from one bus to another, or keep parts energized while one section is serviced. When a section needs to be isolated or if there’s a fault, opening the bus-tie breaker electrically separates the two buses and confines the issue to one area.

This function is specific to AC switchgear arrangements and is not about connecting a generator to a bus, protecting against ground faults, or being limited to DC systems.