Connecting the PE wire to the cable tray

The PE wire should be securely bonded to the metallic cable tray using grounding clamps or connectors, ensuring a continuous low-impedance path to the main earthing system.

Purpose of PE Connection

The Protective Earth (PE) conductor provides a safe path for fault currents from exposed conductive parts to the main earthing terminal, preventing electric shock and equipment damage. In cable tray systems, the PE wire ensures that all metallic components are at the same potential, forming part of the main equipotential bonding system .

Connection Methods

1. Grounding Clamps: Use tin- or zinc-plated grounding clamps to attach the PE wire to the cable tray. This provides both mechanical stability and electrical continuity under fault conditions .
2. Insulated Conductors: If using aluminum trays, avoid bare copper PE wires to prevent electrolytic corrosion. Use insulated conductors and remove insulation only at bonding points .
3. Bonding Between Tray Sections: For multi-section trays, bond the PE wire to each or alternate tray sections to maintain a continuous grounding path. This is recommended even if not strictly required by NEC .
4. Proximity to Live Conductors: In TN or IT systems, install the PE wire close to the live conductors on the same tray to minimize inductive reactance in fault currents .

Material and Sizing Considerations

• Ensure the PE conductor has an adequate cross-sectional area to carry potential fault currents safely. NEC Table 392.60(A) provides guidance for using cable trays as equipment grounding conductors .
• Steel trays can be used as grounding conductors for circuits with ground-fault protection up to 600 A, while aluminum trays have higher limits but require careful consideration of corrosion and insulation .

Best Practices

• Avoid interposing ferromagnetic materials between PE and live conductors to prevent impedance in fault paths .
• Connect the PE wire to the main earthing terminal at the origin of the installation, ensuring downstream PE connections do not tie into neutral conductors .
• For wire mesh trays supporting cables with built-in EGCs, a separate grounding wire is generally not required, but a low-impedance path to a non-system ground is recommended to reduce noise . By following these practices, the PE wire will provide a reliable, safe, and code-compliant grounding path for the cable tray system, ensuring both personnel safety and equipment protection.