Bus duct is a new type of conductor formed by using copper or aluminum as a conductor,supporting it with non vinyl insulation,and then installing it into a metal duct.It has become an indispensable wiring method for electrical equipment and power systems in high-rise buildings,factories,and other areas.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 major difference in busbar trunking accessories refers to the differential circuit composed of all branch currents except for the bus tie switch and section switch.

　　The small difference of the busbar refers to the differential circuit composed of all branches connected to the busbar,including the busbar and section switches,and the current.The large difference ratio differential of the busbar is used to distinguish between faults within and outside the busbar area,while the small difference ratio differential is used for the selection of fault busbars.Usually used in dual mother protection,the large difference is used as the initiating component to distinguish the shortcomings within the area;As a component for selection,distinguish the shortcomings on which bus.The difference between the large and small differential actions in differential protection is that the first time limit for the small differential action is to trip the busbar switch,and then trip all switches connected to the same busbar as the faulty equipment.

　　The major action is to trip all switches within the same time limit,regardless of which bus the equipment is attached to.Under normal dual mother operation,the input is small and selective.During the process of reversing the busbar,the busbar difference is set to a large difference to avoid the protection misoperation caused by the circulating current during the operation of the parallel knife switch.The major difference is more of a starting component,and the key is to choose the faulty busbar based on the minor difference,and then take action.As for the protection plan,the major difference is non selective.The protection plan consists of two busbars,while the minor difference is selective,which can distinguish which busbar has a disadvantage.The protective action will trip all switches and bus tie switches on the defective busbar.

　　The busbar trunking accessories are equipped with highly fire-resistant insulation and non combustible epoxy resin powder sprayed on the busbar.The accessories are fire-resistant insulation components.Specially processed parts such as busbar connectors,plug-in boxes,and busbar trunking accessory shells have fire-resistant properties that comply with fire resistance standards.Low voltage distribution main lines such as fire pumps,fire elevators,and emergency generators should be equipped with fire-resistant busbar trunking fittings to ensure power supply in case of fire and facilitate fire recovery.