Installation of horizontal busbar in low-voltage switchgear

Horizontal busbars in low-voltage switchgear should be installed with proper alignment, secure connections, and adherence to thermal, mechanical, and safety standards to ensure reliable power distribution.

Busbar Placement and Orientation

Horizontal busbars serve as the main conductors connecting incoming power to outgoing circuits. Their placement affects current capacity, heat dissipation, and mechanical stress within the switchgear. Modern designs increasingly favor rear-mounted horizontal busbars over top-mounted layouts because rear-mounted configurations improve thermal performance, reduce copper usage, and allow higher current ratings without oversizing conductors . Proper spacing between phases and neutral/earth bars is essential to prevent insulation aging and maintain safe creepage distances .

Material Selection

Busbars are typically made of copper or aluminum, with copper preferred for higher conductivity and smaller cross-sections. The choice of material impacts weight, thermal performance, and fault withstand capability. Aluminum may be used for cost-sensitive applications, but careful consideration of current-carrying capacity and thermal limits is required .

Installation Procedure

1. Preparation and Handling: Switchgear cubicles are delivered pre-assembled with horizontal busbars. Handle cubicles using lifting plates or fork-lift trucks, ensuring angles do not exceed 60° to prevent mechanical stress .
2. Access and Protection: Remove protective plates covering the busbars to access connection points. Keep the busbars clean and free from dust or moisture during installation .
3. Connection Between Cubicles: Align joint pieces with the busbars of adjacent cubicles. Tighten bolts using a torque wrench, typically around 20 Nm for MNS Light W systems, ensuring secure electrical and mechanical contact .
4. Reinstallation of Protection: After connections are made, replace protective covers to maintain safety and prevent accidental contact .
5. Tap-Off Units: Connect outgoing circuits via tap-off units at designated positions along the busbar trunking system, ensuring overcurrent protection is provided for each outlet .

Thermal and Mechanical Considerations

• Horizontal busbars generate heat under load; proper spacing and orientation help dissipate heat efficiently. Rear-mounted busbars benefit from natural convection and reduce ambient temperature rise .
• Ensure busbars are mechanically supported to withstand short-circuit forces and vibration. Joint quality and alignment are critical for long-term reliability .

Compliance and Standards

Installation must comply with IEC 61439-1 and IEC 61439-6, which define requirements for low-voltage switchgear assemblies, including busbar design, current rating, insulation, and testing . Verification of torque, insulation, and continuity should be performed before energizing the system.

Advantages of Proper Installation

• Reduced copper usage and material cost
• Improved thermal performance and current capacity
• Easier maintenance and future expansion
• Enhanced safety and reliability of the switchgear system By following these guidelines, horizontal busbars in low-voltage switchgear can be installed safely, efficiently, and in compliance with international standards, ensuring optimal performance and longevity.