There are two types of enclosed busbars.One type has a high current carrying capacity but is not resistant to high temperatures,and can only operate at a temperature of 200℃.It is generally installed on power transmission lines and is also known as dense enclosed busbars;Another type of enclosed busbar can withstand high temperatures,generally maintaining 1.5 hours of transmission operation under ambient temperatures of 700-1000℃.Its current carrying capacity can reach up to 5000A.This type of enclosed busbar is called fire-resistant enclosed busbar.The difference between fire-resistant enclosed busbar trunking and dense enclosed busbar lies in the shell part.The shell of fire-resistant enclosed busbar is coated with a layer of fire-resistant coating,while the surface of dense enclosed busbar is sprayed,smooth,and has strong adhesion to the anti-corrosion layer.

　　When designing fire protection and emergency power lines using busbars,fire-resistant enclosed busbars are used.The installation of fire-resistant enclosed busbars requires a relatively large space and is inconvenient for turning,but there are relatively few accessories required for installation.Meanwhile,fire-resistant enclosed busbars can prevent damage from small animals and facilitate future operation and maintenance after installation.The price of the busbar with a current carrying capacity of 450~630A plus other installation costs.When installing fire-resistant enclosed busbars,attention should be paid to using a shaking table to test the insulation resistance value of the enclosed busbar,and making test records and keeping records.The insulation resistance should be greater than or equal to 20MΩ.Because the fire-resistant enclosed busbar is divided into 2.5m sections.During construction,the resistance value should be measured by shaking every section of the enclosed busbar installed.

　　When connecting copper busbars,attention should be paid to applying conductive paste and tightening bolts to prevent fine gaps between the copper busbars that enclose the bus duct.But if the bolt is tightened too tightly,it will crush the insulation ceramic block at the connection of the fire-resistant enclosed busbar,causing insulation degradation.If the bolt connection is loose and the torque of the bolt is less than 27 N,there will be a small gap at the busbar connection,resulting in poor contact and increased busbar resistance.When the torque is between 29~33 N,there are no fine seams at the connection between the busbars,and the insulation ceramic blocks between the busbars are intact.After the installation of the entire fire-resistant enclosed busbar,the insulation resistance should be measured by shaking the busbar.If the insulation resistance is less than 20MΩ,it is due to the bolt connection being too tight at one or several places,causing the insulation ceramic blocks between the busbars to break and resulting in a decrease in insulation resistance.At this time,the problem can only be found by using the segmented method.

　　When installing enclosed busbars with a length exceeding 80m,busbar expansion joints should also be installed.Busbar slot expansion joints are busbar mainline units with axial variation,installed in appropriate positions to absorb axial variation caused by thermal expansion and contraction.The enclosed bus duct should be made of copper or aluminum bars,with plug-in box openings left every few meters.The plug-in box is plugged into the copper or aluminum busbar,and there is an air switch inside the plug-in box that branches out from here.Generally speaking,it has a larger capacity than cable power supply.It's just an iron box with an air switch inside.There are four clips like things under the box,which happen to be stuck on the four copper bars of the bus duct.The current flows from the copper bar to the clamp,and then connects to the air switch through wires.