Technical exploration of using enclosed busbar trunking for power transmission and distribution

Technical exploration of using enclosed busbar trunking for power transmission and distribution

Compared with traditional cables, it fully demonstrates its performance in high current transmission. At the same time, due to the use of new technologies and processes, the contact resistance and temperature rise at the connection points of the two ends of the bus duct and the junction of the distribution port are greatly reduced. High quality insulation materials are used in the bus duct, thereby improving the safety and reliability of the bus duct and making the entire system more complete. The characteristics of busbar trunking are a series of matching, commercial production, small size, large capacity, short design and construction period, easy assembly and disassembly, non combustible, safe and reliable, and long service life. Bus duct products are suitable for three-phase four wire and three-phase five wire power supply and distribution system engineering with AC 50Hz, rated voltage 380V, and rated current 250A-6300A.

When installing a closed bus duct, the overall structure should be horizontal and vertical, and the bus duct should be installed horizontally. The distance between the two supports should not exceed 2500mm, and the distance between vertical installations should not exceed 3600mm; When installed horizontally, the height above the ground should not be less than 2.2m, and the suspension rod should have technical measures to adjust the level.

When laid vertically, the distance from the ground should be at least 1.8m. The installation bracket of Shanxi enclosed busbar trunking manufacturer should be drilled with holes on the channel side plate and fastened with M6-M8 bolts. Brackets should be added at the corners of the busbar and at the connection with the plug-in box. When installing brackets in rows, they should be arranged neatly and spaced evenly. When the terminal box and starting box of the busbar are suspended, they should be fixed with brackets. The brackets on the wall and top plate of the enclosed busbar trough must be fixed with two expansion bolts, which should be equipped with flat washers and spring washers.

When the busbar is laid vertically through the top plate, it should be supported and fixed with channel steel on the passing bottom plate. When the enclosed busbar crosses the expansion joint or settlement joint of the building, measures that adapt to the movement of the building structure should be taken to prevent the horizontal movement of the busbar connection from causing breakage and affecting the power supply and distribution of the busbar.

Installation acceptance:

Mainly inspect the busbar current carrying capacity, IP protection level, insulation resistance, etc. The current carrying capacity test uses a low-voltage high current generating device to conduct a current carrying test on the bus duct (the test current is the rated current of the bus duct), and stops when the temperature change is less than 1K per hour. Temperature rise refers to the difference between the conductor temperature at the plug interface or connection and the ambient temperature, which should meet the user's requirements. The IP protection level shall be tested according to GB4208 standard, including the connection head, elbow and body of the busbar, which shall meet the IP requirements or user bidding requirements. IP51 or above, insulation resistance should be tested after the test. Use a 1000V megohmmeter to measure the insulation resistance of the bus duct. The insulation resistance of a single section of the bus should be greater than 20M Ω, and the total length should be greater than 1M Ω.

The application advantage of busbar trunking lies in its compact size, making it very convenient to transport and operate during installation. At the same time, the bus duct has a large capacity, so the power supply is strong and the production time is relatively short, which can save a lot of time to do other things.

Next is the installation of supports and hangers. Any enclosed or plug-in busbar supports and hangers should be installed accurately, horizontally and vertically, and securely fixed. When installed in rows, they should be arranged neatly and spaced evenly. The fixed bracket bolts should be fixed with flat washers and spring washers, with 2-4 exposed threads.

① The fixing of expansion bolts for brackets should be based on the accurate measurement of the bracket position according to the direction of the busbar path when installing brackets on buildings. The expansion bolts for brackets should be fixed on the drilled holes. It should be noted that the difference between the diameter of the drill hole and the outer diameter of the casing should not exceed 1mm.
② Installation of T-shaped angle steel bracket, which is suitable for horizontal installation of busbars on walls. The bracket is embedded in the wall by pre embedding method. The buried depth of the angle steel bracket is 120mm and 150mm, and the exposed length of the angle steel is the width of the busbar plus 140mm when the busbar is installed vertically. When the busbar is installed horizontally on the side, it is the height of the busbar plus 160mm

The allowable temperature for heating during long-term operation of copper and aluminum bare enclosed busbars is 70 ℃. However, when their surfaces are reliably covered with tin (such as ultrasonic tinning), the allowable temperature can be increased to 85 ℃. Due to the limitation of the continuous heating allowable temperature, different raw materials and cross-sections of enclosed busbars have obtained relative long-term allowable currents. When selecting a cross-section of enclosed busbars, the specific current flow during long-term operation of the enclosed busbar should be lower than the long-term allowable current of the selected cross-section enclosed busbar.

In situations where the average load is high and the enclosed busbar is long (such as enclosed busbars in outdoor distribution equipment), the selection of enclosed busbars is generally based on the economic development current intensity method. The current intensity of economic development is the amount of current that passes through the cross-section of a closed busbar enterprise, taking into account the loss of enclosed busbars, the annual maintenance costs and depreciation of enclosed busbars and attached machinery and equipment. The cross-sectional area of a closed busbar is obtained by dividing the current intensity of economic development by the long-term working current that is not counted as overload.

Multiple protective structures are used to wrap the conductive row, such as wrapping insulation film on the upper and lower arms of the conductive row to ensure the overall insulation of the conductive row. In addition, a sealing strip is further provided between the connection side sealing plate and the connection cover plate to increase the sealing performance of the two assembled together. At the same time, the upper and lower cover plates and side plates are made of non-magnetic alloy materials, greatly reducing the electromagnetic wave radiation generated during the operation of the conductive bars. A heat sink is also added between the two conductive bars, and the surface of the conductive bars is also equipped with several heat dissipation fins to improve the heat dissipation efficiency of the conductive bars.

The insulation layer and outer sheath of ordinary cables will burn. Even flame-retardant cables can burn under flames, only burning after the flames have left. Fire resistant cables do not burn, but they are expensive and should only be used in situations where power outages are not allowed, such as in fire alarm circuit systems. The shell of the bus duct is made of metal and will not burn. Even if the insulation material of the copper bar burns, the flames will not endanger the outside of the bus duct.

The main focus is on verifying the process of the product, the IP protection level of the bus duct connector, the temperature rise of the bus duct plug interface, and the stability and effectiveness of the PE wire. The product process mainly depends on the processing technology and surface treatment technology of the appearance, as well as the precision of the bus assembly. The main consideration for dense bus ducts is that the more compact the precision, the better. The IP protection level of the busbar and busbar connector is an important technical treatment process, and there are many short-circuit accidents in the busbar trunking caused by joint heating, moisture, or water ingress.

According to the usage environment, the installation method should be selected for the busbar trunking. When selecting the busbar trunking, the usage environment should be comprehensively considered. The selection of the enclosure protection level of the busbar trunking should comply with the following regulations: for indoor clean places, IP30 or above should be used. Indoor ordinary places shall adopt a rating not lower than IP40. For indoor areas with splash proof requirements, a rating of no less than IP54 shall be used. For indoor humid areas or areas with splash proof requirements, IP65 or higher shall be used. For places or outdoors with anti-corrosion requirements, fully enclosed resin cast bus ducts with IP68 rating shall be used.

Therefore, necessary protective measures should be taken for installation methods that may cause water ingress into the bus duct. When the bus duct passes through the enclosure layer, due to various reasons such as production or roof leakage, water accumulates on the floor, which will leak down along the bus duct passing through the floor, causing water to enter the bus duct and reducing its insulation. After the bus duct of our acrylic fiber plant polymerization workshop was put into use, a short circuit fault occurred due to water ingress when the bus duct passed through the floor, causing the entire production plant to shut down. The solution is to add waterproof cofferdams when the air type enclosed bus duct passes through floors, even if the bus duct and transformer are connected by expansion joints as a transition. However, due to the use of bus ducts as low-voltage incoming main busbars, the current is generally high, some have reached 2500A, and the corresponding expansion joint section is large and the elasticity is small, which may still cause stress on the low-voltage sleeve of the transformer.