The enclosed bus ducts can be divided into four types: air-type plug busbars, dense insulation plug busbars, high-strength plug busbars, and cast busbars.

First, dense insulation plug bus duct (CMC). Its moisture-proof, poor cooling effect. In terms of moisture protection, busbars are prone to moisture and water seepage during construction, resulting in reduced interphase resistance. The heat dissipation of the busbars mainly depends on the shell. Because of the compact arrangement and installation between the wires, the L2 and L3 phases emit heat slowly, forming a high temperature rise of the busbar. Intensive insulated plug busbars are limited by shell plates and can only produce horizontal sections up to 3m. Because the air gaps between the phases of the busbars are small, when the busbars pass a large current, a strong electric power is generated, so that the magnetic oscillation frequency forms a superposition state, resulting in excessive noise. The plug-in busway is a trunk system, which has the advantages of small size, compact structure, reliable operation, large transmission current, convenient tapping and feeding, convenient maintenance, low energy consumption, good dynamic thermal stability, etc., and is obtained in high-rise buildings. widely used.

Second, high strength closed busbar (CFW). The process manufacturing is not limited by the sheet material, and the shell is made into a tile groove form, so that the mechanical strength of the busbar is increased, and the horizontal section of the busbar can be produced to a length of 13m. As the shell is made of gutters, the pits are intended to separate and fix the busbars, and there is a space of 18mm between the busbars. The ventilation between the lines is good, so that the moisture-proof and heat-dissipation functions of the busway are obviously improved, and it is adapted to the southern climate; due to the line There is a certain gap between the wires, which reduces the temperature rise of the wire, which increases the overload capacity and reduces the magnetic oscillation noise. However, the stray current and inductive reactance produced by it are much larger than that of the intensive bus duct. Therefore, when compared with the specifications, the cross section of the conductive row must be larger than that of the densely insulated plug busway.

Third, the air plug busbar (BMC). Because the connectors between the busbars are soft-connected with copper sheets, the weather is humid in the south, and oxidation is easily generated between the connectors. This leads to poor contact between the connectors and the busbars and makes the contacts easy to generate heat. Therefore, it is rarely used in the south. And the volume between the joints is too large, the size of the horizontal bus section is inconsistent, and the appearance is not beautiful enough.

Fourth, the pouring busbars originated from the volcanic rock ash (inorganic materials) pouring busbars in Belgium and Taiwan. Because the raw material volcanic rocks are hard to find, some domestic manufacturers use epoxy resin to cast them. Although the protection level is better, the heat dissipation performance is poor. In addition, the epoxy resin itself is a combustion-supporting material, and the temperature resistance is poor, so the application is less.