The International Electrotechnical Commission (IEC) provides detailed guidelines for cable tray systems under IEC 61537. This standard outlines the construction requirements, testing methods, and performance parameters for cable trays and related support systems. us-trations without notice. The mechanical and electrical characteristics, tests, certifications, overall quality management, recommendations mentioned. en completely installed, without damage either to conductors or structural system use maintain spacing or to keep cables in place when the tray is ect the minimum bend ra-dius for cables as they exit the bottom of the cable tray. A rung spacing of 6 to 9 inches (150 to 230 mm) is preferable when. Not all cable trays are equivalent. Tray shall be ventilated on both the bott of the tray.