Connecting busbars in low-voltage switchgear requires proper contact area, pressure, material preparation, and torque control to ensure safe and reliable operation.

Busbar Preparation

Before connecting, prepare the busbar surfaces to ensure good conductivity and prevent corrosion. For copper busbars, polish the contact surfaces with fine sandpaper until a mirror finish is achieved, then apply a power compound grease compliant with EN 50165. For aluminum busbars, use an aluminum-specific anti-oxidation agent and, if connecting to copper, employ copper-aluminum transition joints with insulating heat-shrink tubing rated ≥125°C to prevent electrochemical corrosion and withstand high temperatures .

Contact Area and Pressure

The contact area between busbars is critical for heat dissipation and current flow. For main busbar continuity links, the contact area should be at least five times the cross-section of the bar (Sc > 5 × Sb). Branch busbars can have smaller contact areas but must still meet this minimum. For equipment connection plates, ensure contact over the entire surface to handle nominal current . Contact pressure is provided by bolts or screws. Use the correct size, number, and torque according to the busbar dimensions and current rating. Over-tightening can exceed the bolt's elastic limit and cause copper creep, while insufficient torque reduces contact pressure and increases resistance. Devices like paint marks or brittle coatings can indicate loosening and verify proper tightening .

Mechanical Connection Steps

1. Access the busbar joint by removing protection plates in front of the bars.
2. Align the joint pieces with the busbars of adjacent cubicles.
3. Insert and tighten bolts using a torque wrench to the specified torque (e.g., 20 Nm for typical low-voltage connections). For double joint pieces, ensure both are positioned correctly at the front of the bars .
4. Reinstall protection plates to maintain safety and insulation.

Compliance and Safety

Follow IEC 61439 requirements for low-voltage switchgear, which specify minimum clearances, creepage distances, and short-circuit withstand strength. Proper spacing, support, and insulation coordination are essential to prevent overheating, electrical faults, and ensure personnel safety .

Summary Tips

• Always polish and clean busbar surfaces before connection.
• Apply appropriate anti-oxidation compounds for the material.
• Ensure sufficient contact area and correct torque on bolts.
• Use transition joints for dissimilar metals.
• Verify compliance with IEC 61439 and manufacturer specifications. Following these steps ensures reliable, safe, and efficient busbar connections in low-voltage switchgear, minimizing maintenance and operational risks.