What is pre-branched cable? What are the advantages of pre-branched cable? How to lay and install?

Pre-branch cable is to make branch cables in advance. The cables are used directly after leaving the factory without branching on site. The one-time power-on rate is high to avoid various hidden dangers on site.

That is, the branch line factory is pre-manufactured on the main cable. The cross-sectional size of the branch line and the 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. What is the pre-branch cable? What are the advantages of the pre-branch cable? How to lay and install? Bird on the Tree Education Electrical Designer Online Teaching Network Course!

First, the overview of pre-branch cables is to make pre-branches on commonly used cable models, such as VV, YJV cross-linked cables, and the air tightness, dustproof and waterproof of fireproof cables to branch joints, thus avoiding cable failures caused by cable joints.

The pre-branched cable consists of four parts:

(1) Main cable;

(2) Branch line;

(3) Branch joints:

(4) Related accessories, and has three types: ordinary type, flame retardant type (ZR), fire-resistant type (NH). Pre branch cable is a high-rise building busway power supply alternative products, he has a reliable power supply, easy installation, good waterproof, accounting for a small building area, low failure rate, cheap, free maintenance and other advantages, suitable for AC rated voltage of 0.6/1KV distribution lines.

It is widely used in high-rise buildings, residential buildings, commercial buildings, hotels, hospitals, vertical power supply in electrical shafts, and is also suitable for power supply systems such as tunnels, airports, bridges, and highways.

Main performance of prefabricated branch cable:

(1) Insulation resistance ≥ 200MΩ;

(2) Insulation withstand voltage ≥ 3.5kV/5min;

(3) good air tightness and waterproof, that is, the branch joint is immersed in water, and the insulation resistance and power frequency withstand voltage measured between the water and the cable core shall meet the requirements of 1 and 2.

(4) The contact resistance of the branch connector is small, and the ratio of the contact resistance to the reference resistance of the branch line of equal length is less than or equal to 1.2;

(5) The joint short-circuit strength is large, and the change rate of the contact resistance ratio after short-circuit is less than or equal to 0.2;

(6)ZR-YJV type flame retardant prefabricated branch cable, the self-extinguishing time of the sheath is less than or equal to 12s, which meets the requirements of GB12666.5;

(7)NH fire-resistant cable in addition to power supply under normal working conditions, but also in the case of combustion, to maintain the normal operation of 90min, in line with the requirements of GB12666.6.

(8) The maximum working temperature of the copper core of the VV cable is 70 ℃, and the maximum working temperature of the copper core of the YJV cable is 90 ℃;

(9) has excellent corrosion resistance, can resist the corrosion of inorganic salt, oil, alkali, acid and organic deep agent;

(10)YJV type prefabricated branch cable has excellent thermal stability and aging resistance;

(11)GWDZ, WDZA, WDNA, WDZAN-clean prefabricated branch cable with low smoke, low toxicity, halogen-free, fire resistance and other superior performance.

(12)GZR-YJV the chlorine barrier series branch cable. With high flame retardant, fire resistance, flame retardant performance exceeds the flame retardant standard A.

Pre-branch cable advantages:

(1) Excellent shock resistance, air tightness, water resistance and fire resistance.

(2) the main cable conductor without joint, good continuity, reduce the probability of failure.

(3) Adopt advanced fully mechanized crimping technology to avoid the influence of human factors.

(4) The customizability is high, 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 body is extremely small, and it is not affected by thermal expansion and contraction.

(6) Reduce power distribution costs and engineering costs, high economic indicators, comprehensive benefits are obvious.

(7) the installation is simple, the construction period is short, compared with the closed bus duct greatly reduces the installation time.

(8) maintenance-free after installation and operation, do not need any maintenance and maintenance in peacetime.

2. pre-branch cable structure is mainly composed of cable conductor, insulation layer, shielding layer, protective layer and pre-branch cable connection body, which is mainly used for electric energy transmission. Because it is directly processed in the cable factory, it is not necessary to strip the cable on site to branch, thus maintaining the complete electrical performance of the cable. The following is the structure diagram of the power cable connection body:

Three types of branch joints are used: U type, C type and O type. The quality exceeds the national standard and reaches the international level. The branch opening of the pre-branched cable is customized according to the needs of the site and can be up or down.

(1) model: YFD-31 dimensions: 180 × 44 × 22mm applicable cable outer diameter: 50-150m ㎡

(2) Model: YFD-32 overall dimensions: 240 × 55 × 25mm Applicable cable outer diameter: 185-300m ㎡

(3) Model: YFD-33 overall dimensions: 180 × 44 × 22mm Applicable cable outer diameter: 50-150m ㎡

(4) model: YFD-34 dimensions: 240 × 55 × 25mm applicable cable outer diameter: 185-240m ㎡

(5) Material: BMC (fiber reinforced unsaturated polyester molding compound) material with excellent electrical and mechanical properties is molded.

(6) Features and application occasions: anti-eddy current, flame retardant, non-absorbent, high strength, easy installation, etc. Ensure that the cables in the electrical shaft are arranged neatly 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 the safe fixing of 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 use of cable tray, is a cost-effective cable clamp products.

3. branch cable selection instructions (1) general places or equipment lighting and power transmission trunk system, the average ambient temperature below 35 degrees, the choice of "VV" model or "ZR-VV" type.

(2) For the lighting and power transmission trunk system of places or equipment requiring fire protection, the average ambient temperature is above 35 degrees, and the "YJV" or "ZR-YJV" type is selected.

(3) The transmission line system with special requirements for fire protection or fire protection equipment shall be of "NH-VV" type or "NH-YJV" type.

Four, pre-branch cable laying and installation laying and installation preparation according to the requirements of the design drawings familiar with the direction and location of cable laying.

(1) Prepare construction plan and organize professional construction personnel.

(2) Prepare tools and equipment for installation.

(3) Verify the cable model specifications and packaging order.

(4) Verify the accessories and allocate the installation site of the accessories.

(5) Place the cable reel on the pay-off rack.

(6) When the cable is installed vertically, the cable pay-off rack is downstairs, and the cable is lifted by a hoist or pulley block through the rope, requiring professional construction personnel on each floor. As for the terminal, hang the cable on the installed hook

(7) When the cable is installed horizontally, as for the power receiving position, the cable shall be placed manually by professional construction personnel (one person is required every two meters, in the command personnel).

(8) The prefabricated branch cable trunk line and branch line shall be fixed to the middle part as required.

(9) Connect the main line, branch line and electrical control device according to the phase sequence.

(10) Clean up the site after the installation, and measure the insulation resistance of each circuit connected to each phase of the prefabricated branch cable.

(11) Fill in the construction records.

Precautions for 5. laying and installation (1) When laying, try to use forward lifting. When the construction site is restricted or has special requirements, reverse loading can also be used. No matter which kind of setting method, the branch line is not allowed to be released in advance during the process, so as to prevent the branch body from being scratched when passing through the hole and to avoid excessive mechanical external force.

(2) When lifting, the rope with the strength of more than 4 times the weight of the cable must be selected. After laying, the fixing fixture will be installed from top to bottom first.

(3) The bending radius of the cable shall not be less than 25D during laying and installation.

(4) When fixing single-core prefabricated branch cables, it is forbidden to use metal clamps.

(5) When the main line and branch line are connected with the receiving and measuring appliances and the electric measuring appliances, the metal wire clamp must be used, and the metal type of the wire clamp must be selected correctly.

(6) Hanging device must be installed on the load-bearing wall.