Pre branched cable is a kind of cable which is prefabricated according to the user’s design drawing when the factory produces the main acsr cable. What are the advantages of pre branched cable? How to install pre branched cable? Pre branched cable is a new technology product in recent years, which is prefabricated according to the user’s design drawing when the factory produces the main cable.
The branch line factory is pre manufactured on the main cable. The section size and length of the branch line are determined according to the design requirements, which greatly shortens the construction period, greatly reduces the material cost and construction cost, and greatly ensures the reliability of power distribution.
1、 Overview of pre branching cable is to do pre branching on common cable models, such as VV, YJV cross-linked cable, fireproof cable, air tightness, dust prevention and waterproof of branch joint, so as to avoid cable failure caused by cable joint.
The pre branched cable consists of four parts
(1) Backbone cable;
(2) Branch line;
(3) Branch connector:
(4) There are three types of accessories: ordinary type, flame retardant type (Zr) and fire resistant type (NH). Pre branched cable is an alternative product of bus duct power supply in high-rise buildings. It has the advantages of reliable power supply, convenient installation, good waterproof, small building area, low failure rate, cheap price, maintenance free and so on. It is suitable for distribution lines with AC rated voltage of 0.6/1kv. It is widely used in vertical power supply of high and medium rise buildings, residential buildings, commercial buildings, hotels and hospitals, as well as in power supply systems of tunnels, airports, bridges and highways.
Main performance of prefabricated branch cable:
(1) Insulation resistance ≥ 200m Ω；
（ 2) Insulation withstand voltage ≥ 3.5kv/5min;
(3) Good air tightness and waterproof, that is to say, immerse the branch joint in water, measure the insulation resistance and power frequency withstand voltage between water and cable core, both of which shall meet the requirements of 1 and 2.
(4) The ratio of contact resistance to reference resistance of equal length branch line is less than 1.2;
(5) The change rate of contact resistance ratio after short circuit is less than or equal to 0.2;
(6) Zr-yjv flame retardant prefabricated branch cable, sheath self extinguishing time ≤ 12s, in line with the requirements of gb12666.5;
(7) NH fire-resistant cable can not only supply power under normal working conditions, but also keep normal operation for 90min under burning conditions, meeting the requirements of gb12666.6.
(8) The maximum working temperature of copper core of VV cable is 70 ℃, and that of YJV cable is 90 ℃（ 9) It has excellent corrosion resistance and can resist the corrosion of inorganic salt, oil, alkali, acid and organic deep agent;
(10) YJV type prefabricated branch aac cable has excellent thermal stability and anti-aging property.
(11) Gwdz, wdza, wdna, wdzan – clean prefabricated branch cables have the advantages of low smoke, low toxicity, halogen-free and fire resistance.
(12) Gzr-yjv chlorine barrier series branch cable. It has high flame retardancy, fire resistance and flame retardancy, exceeding class a of flame retardancy standard.
Advantages of pre branched cable:
(1) Excellent shock resistance, air tightness, waterproof and fire resistance.
(2) The main cable conductor has no joint, good continuity, reducing the probability of failure.
(3) Adopt advanced fully mechanized crimping technology to avoid the influence of human factors.
(4) It can be customized, and the branch position can be set according to the needs of the distribution point of the distribution system.
(5) The contact resistance of the branch is very small, and it is not affected by thermal expansion and cold contraction.
(6) Reduce the cost of distribution and engineering, high economic index, obvious comprehensive benefits.
(7) The installation is simple, the construction period is short, and the installation time is greatly reduced compared with the enclosed bus duct.
(8) After installation and operation, it is free of maintenance and does not need any maintenance at ordinary times.
2、 Pre branched cable structure
It is mainly composed of cable conductor, insulating layer, shielding layer, protective layer and pre branched cable connector, which is mainly used for power transmission; Because it is directly processed in the cable factory, there is no need to strip the cable on site as a branch, thus maintaining the complete electrical performance of the cable. The following is the structure diagram of power cable connector:
There are three types of branch joints: U-type, C-type and O-type, whose quality exceeds the national standard and reaches the international level. The branch opening of pre branched cable can be customized according to the site requirements, which can be up or down.
(1) Model: yfd-31 dimension: 180 × forty-four × 22mm applicable cable outer diameter: 50-150m2
(2) Model: yfd-32 dimension: 240 × fifty-five × 25 mm applicable cable outer diameter: 185-300 M2
(3) Model: yfd-33 dimension: 180 × forty-four × 22mm applicable cable outer diameter: 50-150m2
(4) Model: yfd-34 dimension: 240 × fifty-five × 25 mm applicable cable outer diameter: 185-240 M2
(5) Material: it is made of BMC (fiber reinforced unsaturated polyester molding compound) with excellent electrical and mechanical properties.
(6) Features and application: anti eddy current, flame retardant, non absorbent, high strength, easy installation, etc. Ensure that the cables in the electrical shaft are arranged in order, without cross arrangement, which can not only prevent eddy current loss, but also prevent the cables from moving due to external force or self weight. It is used for fixing the main power supply cable and emergency lighting cable in the electrical shaft of high-rise or multi-storey buildings. Because of its convenient installation, saving manpower and material resources, especially can replace the cable tray, it is a cable clamp product with high cost performance.
3、 Branch cable selection instructions
(1) For lighting and power transmission trunk system of general places or equipment, the “VV” type or “zr-vv” type shall be selected when the average ambient temperature is below 35 ℃.
(2) For the lighting and power transmission trunk system of places or equipment with fire protection requirements, the “YJV” type or “zr-yjv” type shall be selected when the average ambient temperature is above 35 ℃.
(3) “Nh-vv” type or “nh-yjv” type shall be selected for transmission line system with special fire protection requirements or fire protection equipment.