Proper connection of low-voltage busbars to switchgear requires clean contact surfaces, correct torque on fasteners, and secure mechanical alignment to ensure reliable conductivity and safety.

Busbar Preparation

Before connecting, inspect the busbar material (copper or aluminum) for damage or oxidation. For copper busbars, polish the contact surfaces with fine sandpaper to achieve a mirror finish and remove oxidation. Apply a power compound grease compliant with EN 50165 to enhance conductivity. For aluminum busbars, use an aluminum-specific anti-oxidation agent and, if connecting to copper, employ copper-aluminum transition joints to prevent galvanic corrosion. Insulating heat-shrink tubing rated ≥125°C may be used to protect joints from high temperatures .

Mechanical Connection

1. Alignment: Position the busbar and switchgear connection points carefully. For horizontal busbars in cubicles, remove protective plates to access the connection points and align joint pieces with the adjacent cubicle bars .
2. Contact Area: Ensure the contact area is sufficient. For main busbars, the contact area should be at least five times the cross-section of the bar to allow optimal heat transfer. For branch busbars, smaller contact areas are acceptable but must still meet the minimum requirement .
3. Fastening: Use high-quality bolts or screws, typically stainless steel, and tighten them with a torque wrench to the manufacturer's recommended torque (e.g., 20 Nm for MNS Light W switchgear). Avoid over-tightening, which can exceed bolt elasticity and deform the busbar, and under-tightening, which can create high-resistance joints .
4. Verification: Apply a tell-tale mark (paint or brittle coating) to monitor loosening over time. Ensure all bolts are properly torqued and that the busbar is mechanically stable .

Connection to Devices

• Direct Bolt Connection: MCCBs or other devices can be bolted directly to the busbar, ensuring flush metal-to-metal contact.
• Lug-Based Connection: Use compression lugs when alignment is not exact, ensuring the lug is properly crimped and torqued.
• Plug-On/Comb Systems: Some devices allow plug-on connections to comb busbars, which require compatible profiles and careful insertion to maintain contact integrity .

Safety and Final Steps

• Reinstall protective plates after connections are complete.
• Verify all connections visually and mechanically.
• Ensure proper earthing and insulation clearances are maintained.
• Conduct a final inspection before energizing the switchgear to prevent overheating or electrical faults . By following these steps, the low-voltage busbar will be securely and safely connected to the switchgear, ensuring reliable operation and compliance with IEC 61439 standards.