How to quickly discharge cables in cable trays

Properly discharging cable trays and cables involves grounding the tray system, bonding all components, and ensuring cables are terminated correctly to maintain electrical safety and system reliability.

Grounding and Bonding

Bond the Cable Tray System: All cable trays should be electrically bonded together using bonding jumpers to maintain continuity. Grounding should be applied at least every 15 meters (50 feet) and at both ends of the tray system to ensure safety and prevent potential differences that could cause electrical hazards (PakTechPoint). Expansion Joints: Install bonding jumpers at expansion joints and long outdoor runs to maintain electrical continuity.

Use compression lugs or grounding bushings to connect conduit drop-outs to the tray (PakTechPoint). Cable Termination: Ensure that all cables exiting the tray are properly terminated at panels, instruments, or equipment. This prevents stray currents and reduces electromagnetic interference (AutomationForum).

Cable Management Principles

Segregation: Separate power cables from control and signal cables to avoid interference. High-voltage cables should be isolated from low-voltage or data cables (ApexTray). Support and Routing: Position tray supports strategically so that connectors fall between support points, avoiding placing connectors at the center of spans.

Use guides that allow longitudinal movement to accommodate thermal expansion (PakTechPoint). Drainage and Moisture Control: For outdoor or washdown areas, ensure trays have drainage holes or are sloped to prevent water accumulation, which could compromise grounding and cable insulation (AutomationForum).

Safety and Maintenance

Inspection: Regularly check for rust, sagging, loose bolts, or damage from rodents. Preventive maintenance ensures the grounding system remains effective and cables are not stressed (AutomationForum). Documentation: Tag cables correctly, maintain color coding, and keep records of cable terminations and tray layouts.

This facilitates troubleshooting and ensures compliance with safety standards (AutomationForum). Compliance: Follow NEC, NEMA VE 2, and manufacturer installation instructions to ensure proper grounding, bonding, and cable handling (PakTechPoint).

Summary

To properly discharge cable trays and cables, bond all tray sections, ground at regular intervals, terminate cables correctly, segregate different cable types, and maintain proper support and drainage. Regular inspection and adherence to standards ensure electrical safety, reduce interference, and enhance system reliability.