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 flexible joints between busbars in enclosed bus ducts, oxidation is prone to occur between the joints in humid weather in the south, resulting in poor contact between the joints and the busbars, making the contacts prone to heating. Therefore, they are rarely used in the south, and the volume between the joints is too large, resulting in inconsistent dimensions of the horizontal busbar section and an unattractive appearance.

Enclosed bus ducts are divided into initial enclosed bus ducts, direct 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 according to their purposes. 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.

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. A closed busbar trunking is a busbar system composed of metal plates (steel plates or aluminum plates) as protective shells, conductive bars, insulation materials, and related accessories.

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. The enclosed bus duct has a small volume and compact structure. The outer shell is rolled into a corrugated cross-section rod by a molding machine, which greatly improves its load capacity and gives it extraordinary support strength. It can connect a 6-meter bus center with a load capacity of 70kg and a deflection of no more than 15mm, solving the problem of installation in large-span places that cannot support lifting. The enclosed bus duct can be equipped with 2 sockets within a length of 1 meter, and up to 4 sockets can be installed on both sides without affecting its supporting strength.