How to segment low-voltage busbars

Segmenting low-voltage busbars involves dividing the main bus into multiple sections with proper connections, contact areas, and protection to ensure operational flexibility and safety.

Physical Segmentation and Shaping

Low-voltage busbars act as the backbone of switchgear, distributing energy from the main supply to branch circuits. To segment them:

• Machining and Shaping: Busbars must be carefully machined, bent, and shaped to avoid weakening or introducing stress points. Sharp bends or improper handling can reduce mechanical strength and increase the risk of failure .
• Branch Connections: Each segment can be connected to branch busbars or tap-off units. Contact areas should be at least five times the cross-section of the busbar for main continuity links, ensuring optimal heat transfer and minimal voltage drop .
• Contact Pressure: Use appropriately sized screws and torque settings to maintain firm contact. Devices like paint marks or brittle coatings can indicate loosening over time .

Electrical Segmentation and Protection

Segmenting busbars electrically allows for load balancing and fault isolation:

• Multiple Segments: A busbar can be divided into two or more segments, each feeding different circuits. This is common in double or triple busbar arrangements to minimize space and simplify maintenance .
• Protection Schemes: Each segment should have dedicated protection. Options include overcurrent-based interlocking, differential protection, high-impedance differential, or percentage differential protection. Differential protection is preferred for critical segments or where arc flash hazards exist .
• Dynamic Bus Tracking: For complex segmented systems, busbar protection must dynamically track which circuits are connected to each segment to trip only the faulted section without affecting other segments .

Standards and Compliance

• IEC 61439 / BS EN 61439-6: Segmentation and busbar design should comply with these standards, which cover temperature rise limits, short-circuit withstand, dielectric properties, and safe installation practices .
• Busbar Trunking Systems: For modular installations, busbar trunking allows vertical or horizontal runs with tap-off units at defined positions, providing flexibility and easier extension while maintaining compliance with rated current and voltage drop requirements .

Practical Tips

• Ensure full-surface contact for branch connections at nominal current ratings.
• Use engineered tap-off units to safely draw power from segmented busbars.
• Verify tightening torque and number of screws to maintain contact pressure.
• Plan segmentation to allow maintenance without complete shutdown, improving operational flexibility. By combining careful physical shaping, proper contact design, and segment-specific protection, low-voltage busbars can be safely segmented to optimize performance, reliability, and maintainability .