The enclosed bus duct can be made into a plug-in type enclosed bus duct with plug-in junction boxes at regular intervals,or a feeding type enclosed bus duct without a junction box in the middle.In the power supply system of high-rise buildings,power and lighting lines are often set separately,and enclosed bus ducts are installed vertically along the wall in the electrical shaft as the main power supply line.Due to the use of copper sheet soft joints for transition between busbars,oxidation is prone to occur between the joints in humid weather in the south,resulting in poor contact between the joints and busbars,which makes the contacts prone to heating.Therefore,it is less commonly used in the south.And the volume between the joints is too large,the horizontal bus segment size is inconsistent,and the appearance is not aesthetically pleasing.

　　The dense insulation plug-in bus duct has poor moisture-proof and heat dissipation effects.In terms of moisture prevention,the busbar is prone to moisture and water leakage during construction,causing a decrease in insulation resistance between phases.The heat dissipation of the busbar mainly relies on the shell.Due to the compact arrangement and installation between the wires,the heat dissipation of the L2 and L3 phases is slow,resulting in a high temperature rise in the enclosed busbar duct.The dense insulation plug-in enclosed bus duct is limited by the shell plate and can only produce horizontal sections no larger than 3m.Due to the small air gap between the busbars,a strong electric force is generated when the busbars pass through high currents,causing the magnetic oscillation frequency to form a superimposed state and resulting in excessive noise.High strength enclosed bus ducts can be divided into three types according to insulation methods:air type plug-in enclosed bus ducts,dense insulation plug-in enclosed bus ducts,and high-strength plug-in enclosed bus ducts.

　　The enclosed bus duct is installed vertically along the wall in the electrical shaft as the main power supply line for one or more trips.According to the purpose,a bus duct generally consists of high-strength enclosed bus ducts at the starting end,straight through enclosed bus ducts(with and without sockets),L-shaped vertical(horizontal)curved enclosed bus ducts,Z-shaped vertical(horizontal)offset enclosed bus ducts,T-shaped vertical(horizontal)three-way enclosed bus ducts,X-shaped vertical(horizontal)four-way enclosed bus ducts,variable capacity enclosed bus ducts,expansion enclosed bus ducts,terminal heads,terminal junction boxes,plug-in boxes,accessories and fastening devices related to enclosed bus ducts.

　　Compared with conventional power sources,the advantage of enclosed bus ducts is that they do not require balanced distribution of power loads,making them adaptable to situations of unbalanced loads.The application limitations of substation engineering and construction are due to the fact that transformers and low-voltage distribution boxes are forced to be at different levels,and large capacity transformers and cables cannot meet the needs of low-voltage and high current transmission.Even if the circuit bus design is completed or installed when turned off,it can still be a simple adjustment of the load according to changes in the new program,which cannot be compared to traditional power sources.In addition,cheap plug boxes have replaced expensive low-voltage distribution cabinets and power boxes,which can reduce investment.