The typical safe spacing for a 35kV busbar ranges from approximately 100 mm to 200 mm, depending on insulation, environmental conditions, and design standards.

Clearance and Spacing Considerations

The distance between busbars, known as clearance, is critical to prevent arcing and ensure safe operation. For a 35kV busbar, the spacing depends on:

• Voltage level: Higher voltages require greater spacing to prevent dielectric breakdown .
• Insulation type: Enclosed or coated busbars can allow reduced spacing, while bare conductors require larger clearances .
• Environmental conditions: Humidity, pollution, and altitude affect air insulation; higher pollution or altitude requires increased spacing .
• Busbar configuration: Parallel arrangements or layered spacers may require additional spacing to reduce electromagnetic interference .

Typical Dimensions

Manufacturers of medium-voltage switchgear often provide working guides for busbar spacing. For 35kV systems:

• Phase-to-phase and phase-to-ground spacing is usually in the range of 100–200 mm for metal-enclosed switchgear .
• Tubular or insulated busbars may allow slightly smaller clearances while maintaining safety and dielectric performance .
• ANSI and IEC standards focus on performance and dielectric withstand tests rather than prescribing exact distances, so spacing is determined by passing these tests .

Practical Design Tips

• Ensure busbars are supported and aligned to prevent sagging or contact.
• Avoid sharp edges to reduce localized electric field intensity. Rounded or chamfered edges improve insulation performance .
• Consider short-circuit current rating and thermal expansion when determining spacing .
• Use simulation or manufacturer guidelines to optimize spacing for safety, efficiency, and reliability. In summary, while there is no single mandated distance, a 35kV busbar in typical switchgear is spaced roughly 100–200 mm apart, with adjustments based on insulation, environmental factors, and design requirements to ensure safe and reliable operation .