Installation specifications and precautions for bus ducts and cable trays

　　1.Cable tray wiring

　　(1)When using cable trays indoors for wiring,cables should not be made of jute or other materials

　　(2)When using network cable trays for wiring in corrosive or particularly humid environments,corresponding protective measures should be taken according to the different corrosive media of the enterprise,and plastic sheathed cables should be used.

　　(3)When installing cable trays horizontally,the height above the ground should not be less than 2.50m.When installed vertically,a metal cover should be installed below 1.80m from the ground for protection,but it should be laid outside special electrical rooms(such as distribution rooms,electrical shafts,technical floors,etc.).

　　(4)When installing cable trays horizontally,the optimal time span should be selected based on the load standard curve for technical support,with a span generally ranging from 1.5 to 3 meters.

　　(5)When multiple sets of cable trays are installed in parallel at the same height,the maintenance distance between adjacent cable trays should not exceed 2m.

　　(6)Cables can be laid without distance on cable trays.The filling rate of cable cross-sections in cable trays should not exceed 40%for power system cable companies;The control and cable should not exceed 50%.

　　(7)The following two cables with different operating voltages and economic purposes shall not be laid on the same bridge:

　　a)Cables above 1kV and below 1kV.

　　b)A bidirectional power cable that supplies power to primary loads on the same path.

　　c)Emergency lighting system and other lighting control cables.

　　d)Strong and weak electrical cables.

　　If it is necessary to install on the same level of the bridge due to conditions,partitions should be used to separate them.

　　(8)When cable trays are parallel or intersecting with various pipelines,their minimum clearance distance should meet the requirements of Table DQ4-1.

　　(9)Cable trays should not be installed in corrosive gas pipelines and

　　(10)The cables inside the cable tray should be fixed in the following positions.During installation,anti-corrosion and insulation measures should be taken.Vertical,at the top of the cable,with an interval of 1.50-2m.When laying horizontally,the cable should turn every 5-10 meters at both ends.

　　2.Bus duct wiring

　　(1)Bus duct wiring is suitable for general indoor dry and mechanically undamaged places,but it is not suitable for places with severe corrosion of bus ducts.

　　(2)All phase and neutral wires of the same circuit should be laid in the same bus duct,and lines without anti-interference requirements on the same path can be laid in the same duct.The total number and cross-section(including outer sheath)of wires or cables inside the trunking should not exceed 20%of the cross-section inside the trunking,and the current carrying wires should not affect each other by more than 30.For control,signal or similar circuits,the total cutting amount of wires or cables should exceed 50%of the lower limit of the number of wires or cables in the cross-sectional area of the trunking.

　　(3)When the bus duct is installed vertically or at an angle,measures should be taken to prevent wires or

　　(4)The wiring method of bus duct can be made of metal material pipes,hard plastic pipes,semi-rigid plastic pipes,metal through flexible hoses or cables.The lead out part shall not damage the wires or cables.

　　(5)The groove should be smooth without deformation,and the inner wall should be smooth without burrs.

　　(6)Bus ducts should be reliably grounded or zeroed,but cannot serve as grounding conductors for equipment on their own.