High-voltage switchgear typically includes one or more main busbars and several smaller auxiliary or sectional busbars, with the exact number depending on the configuration and operational requirements.

Main and Auxiliary Busbars

High-voltage switchgear can be configured with single, double, or bypass bus arrangements. In a single bus system, there is one main busbar, sometimes sectionalized into segments using bus couplers to limit outages . In double bus or main-and-transfer configurations, there are two main busbars plus optional bypass or auxiliary busbars to allow maintenance without interrupting supply . These auxiliary busbars are often smaller in size compared to the main busbars and are used to connect specific feeders or branches temporarily during maintenance or fault conditions .

Gas-Insulated Switchgear (GIS) Considerations

In GIS systems, the busbars are modular and enclosed in tubular metal housings. Each section or bay may include coaxial or tubular busbars, with smaller busbars used for branch connections, instrument transformers, or bypass circuits . The number of these small busbars varies depending on the number of feeders, circuit breakers, and sectionalizing requirements. Typically, a GIS bay may have one main busbar and one or more smaller branch or bypass busbars per feeder .

Factors Affecting the Number of Small Busbars

1. Operational flexibility: More small busbars allow isolation of sections for maintenance without interrupting the entire system .
2. Fault tolerance: Sectionalized busbars limit the impact of faults to a smaller portion of the network .
3. Substation size and criticality: Larger or more critical substations often have additional small busbars for redundancy and bypass operations .
4. Switchgear type: Indoor, outdoor, or GIS switchgear may have different numbers and arrangements of small busbars .

Typical Examples

• Small to medium substations: Usually a single main busbar with one or two sectional busbars .
• Large or critical substations: Double main busbars with multiple bypass or auxiliary busbars per feeder, sometimes totaling 3–5 small busbars per section depending on the design .

In summary, the number of small busbars in high-voltage switchgear is not fixed and depends on the system configuration, operational requirements, and substation design. Most installations include at least one main busbar and one or more smaller auxiliary or sectional busbars to ensure flexibility, maintainability, and fault isolation.