How to ground high-voltage cable trays

High-voltage cable trays must be grounded to provide a low-impedance path for fault currents, protect personnel, and ensure system reliability.

Key Principles of Grounding Cable Trays

1. Use the Cable Tray as an Equipment Grounding Conductor (EGC) if Qualified Metallic cable trays can serve as the EGC in installations where qualified personnel maintain the system. This requires that the tray be electrically continuous and properly bonded at all sections to ensure a low-impedance path for fault currents .
2. Bonding Between Sections Each tray section should be bonded to adjacent sections using grounding clamps or connectors. This not only ensures electrical continuity but also mechanically secures the EGC, preventing it from being displaced by magnetic forces during fault conditions .
3. Use Proper Conductors
   • For aluminum trays, avoid bare copper conductors to prevent electrolytic corrosion. Use insulated conductors with insulation removed only at bonding points, connected with tin- or zinc-plated connectors .
   • Ensure the EGC is sized according to NEC Table 250.122 to safely carry fault currents .
4. Connection to Facility Grounding System The cable tray system must be connected to the facility's main grounding system. This provides a permanent, low-impedance path to earth, which is critical for clearing faults and protecting personnel and equipment .
5. High-Voltage Considerations
   • High-voltage trays often carry significant fault currents and may be exposed to lightning or overvoltage transients. Grounding should include connections to shield wires or grounding electrodes to safely dissipate energy .
   • Maintain proper separation between high-voltage and low-voltage circuits to reduce electromagnetic interference (EMI) and ensure signal integrity .
6. Maintenance and Inspection Regular inspection of bonding connections, corrosion, and mechanical integrity is essential. Loose or corroded connections can increase impedance, reducing the effectiveness of the grounding system and increasing safety risks .

Best Practices

• Use grounding clamps at each tray joint or at alternate sections for redundancy.
• Avoid running bare copper in aluminum trays; use insulated conductors with proper bonding.
• Ensure all metallic components, including supports and brackets, are bonded to the grounding system.
• Consider environmental factors such as moisture, chemical exposure, and soil resistivity when designing grounding for high-voltage trays .
• Follow NEC Article 250 and 392 for compliance with grounding and bonding requirements . By following these principles, high-voltage cable trays can be safely grounded, minimizing the risk of electric shock, equipment damage, and EMI, while ensuring compliance with electrical codes and long-term system reliability.