When vertically installed, the height of cable trays from the ground should not be lower than 1. If the above standards cannot be met, metal covers must be added for protection. In practice, cable tray dimensions are a system of interrelated measurements —width, depth, length, and material thickness—that directly affect cable fill compliance, heat dissipation, structural loading, and long-term expandability. This does not apply. Standard Lengths (Z): All NEMA classes are available in standard straight section lengths of 3000 mm (3 meters) and 6000 mm (6 meters). Cables Smaller than 4/0 AWG/Kcmil (120 Sq.