There are many kinds of bus ducts made of steel or aluminum alloy. Therefore, in the electrical installation of high-rise buildings, the installation of bus duct is very important. How to install the low voltage bus? Let's see.
1. Low voltage bus channel connection
1. Connection between low-voltage bus duct and low-voltage bus duct. There are two connection modes between low voltage bus and low voltage bus: plug-in type and butt type. From the previous operation, every accident happened in the low-voltage bus duct, because the joint was heated and the insulation layer was damaged, resulting in the short circuit between phases. Calculation formula for thermal stability of low pressure main tank joint:
The calculation value of the maximum allowable temperature of the bus joint at the maximum current; the calculation value corresponding to the initial working temperature of the bus joint before the maximum current; time; maximum stable current. It can be seen from the calculation formula that the temperature rise is directly proportional to the time of the square of the maximum steady-state current and inversely proportional to the square of the contact area. Therefore, the larger the contact area, the smaller the corresponding temperature rise. In order to prevent heating, the contact area of low voltage bus joint must be increased.
从这个角度看，低压母线槽的连接是低压母线槽安装中的薄弱环节，也是低压母线槽安全运行的隐患。有效地消除隐患,保证连接器的低压母线槽的安装质量,首先在低压母线槽的安装,在设置关节两侧的500毫米横臂架,确保低压母线槽联合部队,不是两个相同的低压母线槽的线,增加低压母线槽连接器的接触面积,涂以电力联合复合,增加接触面积。第三，用扭矩扳手按规定扭矩(ml0为20n)拧紧芯绝缘螺栓。M M12等于70N。M, M16是115N.M);
From this point of view, the connection of the low-voltage bus duct is the weak link in the installation of the low-voltage bus duct, and also the hidden danger of the safe operation of the low-voltage bus duct. Effectively eliminate the hidden dangers and ensure the installation quality of the low-voltage bus duct of the connector. First, install the low-voltage bus duct with a 500mm cross arm on both sides of the joint to ensure that the joint force of the low-voltage bus duct is not the center line of the two same low-voltage bus ducts, increase the contact area of the low-voltage bus duct connector, and apply the power joint compound to increase the contact area. Third, use a torque wrench to tighten the core insulation bolt according to the specified torque (ml0 is 20n). M M12 is equal to 70N. M. M16 is 115N. M);
2. Connection of LV bus duct and transformer. The expansion joint is used for the over connection between the low-voltage bus duct and the transformer. However, due to the large design current at the low-voltage outlet side of the transformer, the section of the corresponding expansion joint is also large, but the elasticity is small, and the low-voltage bushing of the transformer is still in the state of stress. Therefore, the low-voltage bus of substation substation is connected as shown in Figure 1 and fixed on the "rigid" channel steel. In this way, the "flexibility" of the expansion joint is matched with the "rigidity" connection of the channel steel support, so that the low-voltage bushing of the transformer is not damaged by stress.
Installation of low voltage bus
1. Disadvantages of round steel hoisting of low-voltage bus duct. Round steel hoisting is a kind of "flexible" fixation, which can only lift the low-voltage bus duct to make it unable to move downward. The low-voltage bus slot is affected by torsional stress because it may change left and right or during short-circuit electrical installation or operation, which makes the joints of the low-voltage bus slot loose and increases the contact resistance, leading to serious heating joint (especially the low-voltage bushing may be damaged, etc.).
2. Fixing method of low voltage bus channel. According to the above analysis, the low-voltage bus duct is supported by channel steel bracket, both sides of the low-voltage bus duct are fixed on the channel steel bracket by pressing plate, and the channel steel bracket is fixed by "rigid" support and hanger.
3. The two ends of the low-voltage bus duct are used as the phase relationship of the low-voltage incoming line
4. Between transformer and low-voltage inlet cabinet. Due to the structural design of civil engineering, the change of the layout design of distribution equipment and the design of distribution equipment manufacturers, for example, the phase sequence of bus ducts at both ends of low-voltage distribution equipment is not in place, resulting in that the transformer and low-voltage incoming cabinet cannot be directly connected to the low-voltage bus duct, the small current is connected by the auxiliary incoming box bus transposition (usually zero bus transposition), and the large current (greater than 1000A) is connected by the reversing joint;
5. Between low-voltage feeder cabinet and low-voltage electrical control panel. Due to the layout design of process equipment and the design of manufacturer of process equipment and low-voltage electrical control panel, and the phase sequence of bus duct at both ends of low-voltage distribution equipment is not in place, the low-voltage feeder cabinet and low-voltage electrical control panel cannot be directly connected to the low-voltage bus duct, and the small current connected with auxiliary box connection bus transposition (usually zero bus transposition), The large current is connected through the reversing joint (more than 1000A), so that the devices at both ends of the low-voltage bus are correctly connected in the same phase.
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