Cable trays are a support system for electrical cables, power, signal, and communication and optical fiber cables. What is the role of a cable tray in electrical engineering? A cable tray allows for the neat and aesthetic arrangement of cables. Cable trays and pipes serve as the backbone of electrical and fluid transportation systems in both residential and industrial environments. They have openness, and therefore, everything is easily seen. One of the strongest traits of cable trays is customization giving you the flexibility to adapt them to your specific site and load requirements. NEC section 300-8 does not permit any tube, pipe, or equal for water, air gas, drainage, steam, or any service other than electrical in raceways or cable trays containing.