Grounding of cable tray support

Proper grounding of cable trays and their supports ensures electrical safety, prevents shocks, reduces interference, and maintains compliance with NEC standards.

Importance of Grounding Cable Trays

Grounding cable trays is essential to safely channel electrical leakage from conductors to the earth, reducing the risk of electric shock and equipment damage. It also prevents static electricity buildup and electromagnetic interference, which is critical in environments with sensitive electronics. Proper grounding facilitates troubleshooting and safe maintenance operations while ensuring compliance with electrical regulations and standards .

Grounding Methods

• Metallic Cable Trays: Metallic trays can serve as equipment grounding conductors (EGC) if they meet NEC requirements. Sections of the tray should be bonded using flexible jumpers with lugs of appropriate cross-section to maintain electrical continuity .
• Non-Metallic Cable Trays: Non-metallic trays cannot act as grounding conductors. Independent grounding lines must be installed in critical applications such as industrial facilities, rail systems, or solar power plants .
• Cable Screens and Conductors: Cable screens should be connected to the grounding system at both ends. Multi-conductor cables with individual EGCs should be bonded to the tray sections using grounding clamps to prevent mechanical displacement under fault conditions .
• Insulated Conductors: In aluminum trays, bare copper EGCs should be avoided to prevent electrolytic corrosion. Insulated conductors with stripped ends at bonding points are recommended, using tin or zinc-plated connectors .

Support Grounding

Supports and mounting hardware for cable trays should also be grounded to maintain a continuous low-impedance path to earth. This ensures that any fault current is safely directed away from personnel and equipment. Grounding resistance should ideally be 4 ohms or less to ensure effective fault current dissipation .

NEC Compliance

• NEC Article 392 governs cable tray systems, including grounding and bonding requirements .
• Metallic trays used as EGCs must comply with Article 250.96 and Table 392.60(A) limitations .
• Proper tray fill, separation of high-power and low-power cables, and accessibility for maintenance are also required to meet NEC standards .

Best Practices

• Plan grounding points and conductor routes during system design.
• Use flexible jumpers to bond tray sections and supports.
• Avoid placing bare conductors in aluminum trays; use insulated conductors with proper connectors.
• Ensure low grounding resistance and keep grounding conductors clear of flammable or corrosive materials . By following these practices, cable tray systems can provide safe, reliable, and interference-free operation while meeting regulatory requirements.