Inspection Standards for Cable Tray Grounding

1. Mandatory Inspection Items

• All metal cable trays (steel, galvanized, aluminum alloy) must be equipped with PE protective grounding.
• Grounding points:
  • Total length ≤ 30 m: ≥ 2 grounding points (one at each end).
  • Total length ＞ 30 m: add one grounding point every 20–30 m.
   
• Grounding connection is mandatory at entries/exits of distribution boxes, cabinets, and electrical rooms.
• The entire length must form a continuous electrical path; no broken, insulated, or non‑conductive sections are allowed.

2. Connection and Bonding Standards

① Galvanized Cable Tray

• Each end of the joint plate shall have ≥ 2 bolts with lock washers or lock nuts.
• Contact surfaces must be clean (no paint, plastic, or debris) to ensure metal‑to‑metal conductivity.
• No jumper wire required.

② Spray‑painted, baked‑enamel, non‑galvanized tray

• Jumper bonding is required at both ends of each connection.
• Jumper: copper core flexible wire ≥ 4 mm².
• Paint/coating must be removed at bonding points to expose bare metal.

③ Deformation joints / expansion joints

• Must use flexible jumpers (typically braided copper wire ≥ 16 mm²).
• Ensure grounding continuity during thermal expansion, contraction, or structural settlement.

3. Grounding Resistance Standard

• Protective grounding resistance ≤ 4 Ω.
• When shared with lightning protection grounding: ≤ 1 Ω.
• Must be verified on‑site using a ground resistance tester.

4. Continuity Inspection (Critical for Inspection)

• Test with multimeter (resistance range).
• Between any two segments and between tray and main grounding bar:
  • Continuity must be reliable, resistance near 0 Ω.
  • No high resistance or open circuit allowed.
   

5. Appearance and Installation Standards

• Grounding connections firm, no looseness or missing parts.
• Jumpers neatly routed, not taut, twisted, or crushed.
• Grounding conductors must be yellow‑green.
• Supports and hangers shall be equipotentially bonded to the tray.
• No breaks in grounding continuity at wall or floor penetrations.

6. Acceptance Conclusion (Simplified Pass Criteria)

• Metal cable tray is continuously grounded along its entire length.
• Number of grounding points ≥ 2, with additional points for long runs.
• Galvanized tray: double bolts + locked; non‑galvanized: 4 mm² jumpers + paint removal.
• Entire system shows good electrical continuity.
• Grounding resistance ≤ 4 Ω.
• Deformation joints equipped with flexible jumpers.