Prefabricated branch cable is a kind of new type building distribution cable, widely used in high-level architecture, large workshops, cultural venues power distribution, the structure characteristics of the products according to various concrete construction and distribution requirements, connect the trunk cable, branch cable, branch body three parts such as the integration of design and manufacture, with excellent technical and economic indicators, in the aspect of engineering economy, technology and installation convenience, has outstanding advantages than traditional cable and bus.
The purpose of this paper is to briefly introduce the branch cable structure, performance on the basis of the focus on the analysis of the product in accordance with the building electrical related specifications of the technical advancement.
Structure and performance of branch cable
1. Generation and technical standards
The branch cable is developed on the basis of ordinary plastic cable.
Due to the development of modern civilization, urban high-rise buildings are more and more popular, in the electrical design of the distribution system of high-rise buildings, the reliability of power supply, engineering economy and construction convenience are more and more important, the use of ordinary power cable power supply, the contradictions of the three are always difficult to be completely unified, can only be focused on according to different projects.
According to the traditional method, in the floor distribution design, there are usually three kinds of methods:
A. Radiative type. The underground distribution room directly supplies power to the lead cables of each floor respectively. This method has the best reliability, but requires a large number of cables, Bridges and large cable Wells, with high cost and the worst economy.
B, link method, from the distribution room lead cable to the bottom distribution box, and then from the bottom layer up link power supply, this method is the best economy, but because the more layers, the lower the safety system, the number of safety system is multiplied step by step, therefore, the worst reliability.
C. Divide a high-rise building into N unit areas, each unit is supplied by cable from the distribution room, and then distributed to each floor in the unit area.
This method has good reliability and economy and is often adopted.
D, trunk cable branch method, from the distribution room leads to one or more trunk cables, each floor in the trunk cable joint branch, this method is the best economy, theoretically also has the radiative distribution of the reliability, but the construction is the most troublesome.
More troubling floors on the main cable branch, the cable structure and site construction conditions and the influence of personnel quality, joint quality is uneven, the reliability of the actual operation is not satisfactory, but this method makes people think of the connector with cable manufacture, was born of a new generation of building distribution cable, branch cable.
Branch cable is the single core power cable which has been specially processed as the main cable of the building. According to the structural characteristics and size of the specific building, the branch joint is designed and manufactured together with the branch line and the main cable in advance.
Is the above (4) method in the site construction and management of the work by professional manufacturers to complete, so that the joint reliability is greatly improved, and the process consistency also brings the quality consistent, to ensure the purpose of reliability of operation.
Branch cable earlier appeared in the UK and Japan, in terms of technical standards, in 1980, the Japanese wire industry association issued the first industry standard JCS376 (1980), with the development and progress of technology, for the standard was revised in 1992, to relax the requirements of product structure, improve the technical indexes of finished product, at present, the domestic regular branch cable factory main is based on the standard of product standards.
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2, structure,
Branch cable in the structure, divided into single core type and multi-core stranded type two, each single core branch cable can be divided into three parts :(1) main cable;
(2) branch cable;
(3) branch connecting head.
At present, the single-core branch cable has been widely used because of its simple structure and convenience in production and construction.
According to the provisions of the Japanese standard, multi-core branch cable is essentially a combination of multiple single core cables, rather than the traditional concept of multi-core cable structure, multi-core branch cable has a separate insulation and sheath outside each phase conductor, each wire core has an independent branch connecting head.
Multi-core branch cable has the operation performance of general multi-core cable.
Only a few large comprehensive cable plants in China have the production capacity, which is now being applied.
3, performance,
Branch cable is a new type of power distribution cable, which has two key properties:
First of all, a branch cable with good quality must be a power cable with excellent performance. For domestic products, the conductor performance, insulation performance and mechanical and physical properties of the material should meet the GB12706-91 standard -- the performance of the cable is the basic index of branch cable products.
Second, the performance of the branch connector is critical, which is the key performance of the branch cable.
The branch connector connects the main cable and the conductor of the branch cable as a whole, and provides insulation and moisture-proof treatment.
From the appearance, it is impossible to know the quality of the internal joint. There are two important tests that can detect the joint performance, namely the mechanical tension test and the electric heating cycle test.
For mechanical tensile test, the breaking force of branch connector (including trunk and branch conductors) should be maintained at more than 80% before connection. For electric heating cycle test, the temperature rise of branch connector should not be higher than the temperature of branch connector at 25 cycles after 125 rated load and no-load cycles.
The material and process of the branch joint are the key factors to determine the mechanical and electrical properties of the branch joint.
For the majority of users, we should fully care about the cable quality of the branch cable, the material selection of the joint and the production process tooling.