A closed busbar trunking is an efficient distribution device for transmitting current.It is a sealed metal trunking device made of aluminum and copper busbar columns,used as a carrier for collecting and distributing electricity.Therefore,it is also known as a closed busbar trunking.Enclosed bus ducts can be divided into three forms according to different insulation methods:high-strength plug-in sealed bus ducts,dense insulation plug-in sealed bus ducts,and air type plug-in sealed bus ducts.According to the differences in the structure and purpose of enclosed bus ducts,they can be further divided into air insulation,air additional insulation,dense insulation,fire-resistant,tree expansion insulation,and sliding contact enclosed bus ducts.

　　We can divide enclosed bus duct enclosures into steel enclosures,aluminum alloy enclosures,and steel aluminum hybrid enclosures based on the materials used for their production.Compared with traditional cables and transmission wires,it has significant technological advantages in large-scale current transmission due to its small size,large capacity,and quick assembly and disassembly.In addition,high-quality insulation materials are used in the enclosed bus duct,which improves the safety and reliability of the power supply and distribution system while also extending the service life of the enclosed bus duct.

　　In the selection and use of enclosed bus ducts,comprehensive consideration should be given to the specific environment,and the appropriate type and material of enclosed bus duct should be selected according to different situations.In addition,for various enclosed bus ducts,the cross-section of the enclosed bus duct should usually be selected according to the long-term operating current.And according to the premise of passing through a large short-circuit current,verify the short-term thermal stability and dynamic stability of the enclosed bus duct.

　　Under normal circumstances,enclosed bus ducts are used in three-phase four wire and three-phase five wire power supply and distribution systems with 50Hz,rated voltage of 380V,and rated current of 250~4000A.Due to factors such as the resistance of conductors and the AC current meter effect when multiple conductors approach each other,passing current through a closed bus duct can cause fever.The permissible temperature for copper and aluminum bare enclosed bus ducts during long-term operation is 70℃,but when there is a reliable tin cover at the contact surface,the permissible temperature increases to 85℃.