The conductor of the bus duct is generally copper or aluminum,which is divided into three-phase four wire or three-phase five wire.Each phase is insulated from each other and enclosed by a metal shell made of stainless steel and aluminum manganese alloy to ensure corrosion resistance.Each section of the bus duct is not very long,which is for the convenience of transportation and installation.Connectors are used to connect each section.The current carrying capacity of a bus duct refers to the effective value of the current that the bus can carry under specified conditions.When the busbar is placed vertically,its current carrying capacity is higher than when it is placed horizontally.Generally,when the busbar is placed horizontally and the width is less than 60mm,its current carrying capacity is 0.95 times that of when it is placed vertically.When the width is greater than 60mm,its current carrying capacity is 0.92 times that of when it is placed vertically.This is because the heat dissipation performance is better when it is placed vertically than when it is placed horizontally.

　　Bus duct tapping is convenient.The so-called plug-in bus duct refers to its use of plugging to tap the power supply of the main line to the branch line,making tapping very convenient.The disadvantage of cables is that they need to be customized from the factory;The branch connection method adopts an open"C"-shaped clamp.Over time,can the clamping force be guaranteed?In addition,the price of each branch head is expensive,so the application of prefabricated branch cables is still not widely used.Any floor needs to cut off the power supply,and the bus duct does not need to be powered off.As long as it is unloaded,the plug-in box of the bus duct can be removed.But it is very dangerous to cut off the branch power supply of the prefabricated branch cable while it is live.

　　The strong overload capacity of the bus duct depends on the high working temperature of the insulation material used.The insulation material used for the bus duct is made of materials with a working temperature of 105℃.Radiation cross-linked flame-retardant winding tape(PER)and radiation cross-linked hydrocarbon heat shrink tubing with a working temperature of over 140℃have been developed.The insulation material used in cables generally operates at temperatures of 95℃and 105℃,so the overload capacity of bus ducts is much greater than that of cables.From the perspective of current carrying capacity,wires and cables carry small currents,while busbars carry large currents;Bus duct can prevent overload and fire:The bus duct shell is made of steel and will not burn.Even if the insulation material of the copper bar burns,the flames will not spread outside the bus duct.The insulation layer and outer skin of ordinary cables will burn,and flame-retardant cables will also burn under flames.They only do not burn after the flame has left,while fire-resistant cables will not burn,but they are expensive.Only fire-resistant cables are used for power supplies that are not allowed to be cut off,such as firefighting.

　　Bus ducts have good heat dissipation performance,and the insulation materials of cables(core insulation and outer insulation)are both insulation materials and thermal insulation materials.Therefore,when laying power cables in cable trays,it is allowed to lay two layers more,and the reason for this is to consider heat dissipation.Bus ducts utilize air conduction for heat dissipation and dissipate heat through closely contacting metal shells.Therefore,their heat dissipation performance is average compared to cables.The service life of busbar trunking is over 50 years,and the service life of branch cables is 10-12 years.It can be seen that enclosed busbar trunking has a much longer service life than branch cables.Bus ducts are easy to maintain and require almost no maintenance.Daily maintenance usually involves measuring the temperature rise of the casing and bus connectors,the temperature rise of the incoming box joints,and whether the fasteners are loose.