Connecting the low-voltage electrical cable tray to the low-voltage electrical cabinet

The bottom incoming line of a low-voltage cabinet is routed from the foundation or cable interlayer into the cabinet using cable trays or ladders, ensuring mechanical support, proper spacing, and safe entry into the switchgear.

Downward Entry Method

For L

V switchgear, downward entry refers to connecting power cables from the floor or trench into the bottom of the cabinet. This method is advantageous in compact spaces or renovation projects because it saves vertical space and simplifies the layout while maintaining a clean appearance. The cables are typically routed along cable trays or ladders that guide them from the trench to the cabinet terminals.

Cable Tray Connection

Support and Routing: Cables should be supported on cable trays or ladders with proper spacing and secure clamping to prevent sagging or mechanical stress. Drop-out accessories are used where cables turn down into the cabinet to maintain support and prevent sharp bends. Clearances: Maintain a minimum clearance behind and around the trays (typically 20mm or more) to allow for heat dissipation and future maintenance.

Electrical and instrumentation trays should be separated to reduce EMI, with power cables above and low-voltage control cables below. Entry Protection: Holes in the tray for cable entry should be bushed or lined with grommets to prevent insulation damage. The cables should enter the cabinet at a controlled bend radius to avoid stress on terminations.

Electrical and Safety Considerations

Mechanical Bonding: Cable trays must be mechanically strong and bonded to ensure no relative movement occurs, which protects the cables and maintains grounding continuity. Routing Efficiency: The path from the tray to the cabinet should be as straight and short as possible, minimizing unnecessary bends to reduce voltage drop and mechanical strain. Compliance: All installations should follow manufacturer specifications, IEC standards (e.g., IEC 61439 for LV switchgear), and local electrical codes to ensure safe operation and maintain accessibility for maintenance.

Summary

The bottom incoming line is connected to the LV cabinet by routing the cables along properly supported and protected cable trays, using drop-out accessories for bends, maintaining clearances, and ensuring mechanical and electrical safety. This method ensures efficient, safe, and maintainable connections while optimizing space in the distribution room.