Branch cable is a new type of prefabricated building power distribution cable, which is widely used in the power distribution of medium and high-rise buildings, large factories and cultural venues. According to the structural characteristics and power distribution requirements of each specific building, the product integrates the main cable, branch line cable and branch connector, which has excellent technical and economic indicators and is widely used in engineering economy The advantages of sex, advanced technology and installation convenience are outstanding advantages over traditional cables and busbars. This paper aims at briefly introducing the structure and performance of branch cables, and emphatically analyzes and introduces the advanced technology of the product in meeting the relevant specifications of building electricity.
Structure and performance of branch cable
1. Production and technical standards
Branch cable is developed on the basis of ordinary plastic cable. Due to the development of modern civilization, urban high-rise buildings are becoming more and more popular. In the electrical design of high-rise building power distribution system, power supply reliability, engineering economy and construction convenience are becoming more and more important. Using ordinary power cable for power supply, the contradiction between the three is difficult to be completely unified, and can only be focused on according to different projects. According to the traditional method, there are three methods in the floor power distribution design
a. Radial, direct power supply for each floor by underground power distribution room, this method has the best reliability, but needs a large number of cables, bridge and large cable well, high cost and the worst economy.
b. The link method, which leads the cable from the distribution room to the bottom distribution box, and then links the power supply from the bottom layer to the top layer by layer, has the best economy, but because the more layers there are, the lower the security system is, and the number of security systems is multiplied step by step, so the reliability is the worst.
c. A high-rise building is divided into n unit areas. Each unit uses cables to supply power from the distribution room, and then it is distributed to each floor in the unit area. This method has good reliability and economy, and is often used.
d. The trunk cable branch method leads out one or several trunk cables from the distribution room, and each floor connects and branches on the trunk cable. This method has the best economy, and theoretically has the equivalent reliability of radial distribution, but the construction is the most troublesome. What's more troublesome is that when making floor branch on the main cable, due to the influence of cable structure, site construction conditions and personnel quality, the quality of joints is uneven, and the reliability of actual operation is not satisfactory. However, this method makes people think of making joints together with cables, thus giving birth to a new generation of building distribution cables - branch cables.
Branch cable is to take the single core power cable treated by special technology as the main cable of the building. According to the structural characteristics and size of each specific building, the branch joint, branch line and main cable are designed and manufactured together in advance. In the above (4) method, the on-site construction and management work is completed by the professional manufacturer, which greatly improves the reliability of the joint, and the process consistency also brings the quality consistency, so as to ensure the operation reliability.
Branch cable appeared earlier in Britain and Japan. In terms of technical standards, in 1980, Japan Wire Industry Association issued the first industrial standard jcs376 (1980). With the development and progress of technology, the standard was revised in 1992, which relaxed the requirements for structural materials of products and improved the technical indexes of finished products. At present, there are many regular branch cable manufacturers in China Our product standard is mainly based on this standard. Please log in: www.tede.cn Browse for more information
2. Structure
Branch cables are divided into single core type and multi-core stranded type in structure. Each single core branch cable can be divided into three parts: (1) trunk cable; (2) branch cable; (3) branch connector.
At present, the single core branch cable has been widely used because of its simple structure and easy production and construction. According to the Japanese standard, the multi-core branch cable is actually the twisted body of multiple single core cables, rather than the traditional multi-core cable structure. Each phase conductor of the multi-core branch cable has a separate insulation and sheath, and each core has an independent branch connector. The multi-core branch cable has the operation performance of the general multi-core cable. Only a few large-scale comprehensive cable factories in China have the production capacity, and they are now being popularized and applied.
3. Performance
Branch cable is a new type of power distribution cable, which has two key performances
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 materials should meet the standard of GB12706-91 - the performance of cable is the basic index of branch cable products.
Second, the performance of branch connector is very important, which is the key performance of branch cable. The branch connector connects the conductors of the trunk cable and the branch cable as a whole, and carries out 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 performance of the joint, namely mechanical tensile test and electrothermal cycle test. For mechanical tensile test, the breaking force of branch connector (including main line and branch line conductor) shall be maintained at more than 80% before connection. For electric heating cycle test, after 125 rated load and no-load cycles with certain time interval, the temperature rise of branch connector shall not be higher than 8 ℃ at 25 cycles. The key to determine the mechanical and electrical properties of the branch connector is the material and technology of the branch connector. For the majority of users, we should pay full attention to the cable quality of branch cable, the selection of joint materials and production process tooling.