Cable tray bridging and grounding

Yes, cable tray installation typically includes grounding bridging to ensure electrical continuity and safety, especially for metallic trays.Grounding RequirementsAll metallic cable trays must be grounded according to NEC Article 250.96, regardless of whether the tray itself is used as an equipment grounding conductor (EGC) or a separate EGC is installed . Grounding ensures that the tray does not become energized and provides a safe path for fault currents, reducing the risk of electric shock or equipment damage .Grounding Bridging PracticesGrounding bridging refers to connecting adjacent sections of a cable tray with a conductive path to maintain electrical continuity. This is commonly done using:Copper-core flexible wires or bonding conductors with a cross-sectional area of ≥4 mm² for connecting tray sections .Grounding clamps to mechanically and electrically bond the EGC to the tray sections, which also prevents the EGC from being displaced under fault current conditions .Interlayer bridging for multi-tier trays, typically every 6 meters, to ensure continuity across layers . While the NEC does not explicitly require bonding each tray section with a separate conductor, it is considered a desirable practice for safety and reliability . International standards (e.g., GB 50303-2015) specify multiple grounding points along the tray, with bridging at connecting plates and expansion joints for long runs .Equipment Grounding Conductor (EGC) OptionsTray as EGC: If the tray meets cross-sectional area requirements (e.g., steel up to 600 A, aluminum up to 2000 A), it can serve as the EGC .Separate EGC: A dedicated conductor can be installed inside or attached to the tray, bonded to each or alternate tray sections .Multiconductor cables: Cables with individual EGCs can also be used, with bonding to the tray recommended for mechanical stability .SummaryIn practice, grounding bridging is an integral part of metallic cable tray installation to maintain electrical continuity, comply with NEC and international standards, and ensure safety. It involves connecting tray sections and layers with conductive bonds, using clamps or flexible conductors, and may include a separate EGC or the tray itself as the grounding path . Proper implementation prevents electrical hazards and supports reliable operation of the electrical system.