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Wire and cable selection method
时间:2014-07-22   点击:(2499)

First, the general principles of wire and cable optional 
 
In the selection of wire and cable, wire and cable in general should pay attention to models, specifications (conductor cross section) of choice. 
⒈ wire and cable type selection 
Selection of wire and cable, to consider the use of laying conditions and safety; example, 
Depending on the application, the choice of power cables, overhead insulated cables, control cables, etc.; 
Depending on laying conditions, the choice of general plastic insulated cables, steel tape armored cables, steel wire armored cables, cable and other corrosion; 
According to security requirements, the choice retardant cables, fire-retardant cables, flame retardant cables, fire-resistant cables. 
⒉ select wire and cable specifications 
Determine the use of wire and cable specifications (conductor cross-section), the general should be considered fever, voltage loss, economic current density, mechanical strength selection criteria. 
According to experience, low-voltage power lines because of the load current is large, it is generally hot conditions press select section, and then checking the voltage loss and mechanical strength; Low voltage lighting line because of its high level of requirements can press the allowable voltage loss condition Select the cross-section, and then checking the heating conditions and mechanical strength; pair of high-voltage lines, then press the economic current density select section, and then checking its heat conditions and allows the voltage loss; while high voltage overhead lines, but also checking its mechanical strength. If the user does not have experience, you should consult the relevant professional units or people.
This table is based on calculation of capacity-phase 380V, Cosφ = 0.85 as a reference, if the single-phase 220V, Cos & phi = 0.85, capacity should × 1/3. 
3 When the ambient temperature is high or the methods used for surface, with its safe carrying capacity will decline, and you should choose a larger size; frequent starter motor when used, should be used in 2 ~ 3 specifications. 
4 This table PVC insulated wire laid by a single overhead calculated, if it is worn or more laying pipe, you should use a large 2 ~ 3 specifications. 
5 The above data for reference only, the final design and determine the cable type and specifications should refer to the relevant professional information or electrician manual. 
Second, the use of wire and cable characteristics 
Product features detailed product-specific directory. 
Third, the wire and cable transport and storage 
⒈ transport in non air-dropped cable or cable reels from a height, especially at low temperatures (typically about 5 ℃ and below), throw, throw the cable will likely lead to insulation, sheathing cracking. 
⒉ in the open air in order to avoid possible way to store bare cables, cable tray allowed to lie flat. 
⒊ lifting the package, the non several dishes simultaneously lifting. In vehicles, ships and other means of transport, cable tray use appropriate methods to be fixed to prevent a collision or overturn, in order to prevent mechanical damage to cables to each other. 
⒋ cable forbidden contact with acids, alkalis and mineral oils, and these substances should be stored isolated from corrosive. Shall not have the storage warehouse damaged cable insulation and corrosion of metals harmful gases exist. 
⒌ cable in custody, should be regularly roll (summer three months time, other seasons may be extended as appropriate). When you scroll, the store down to the rim roll up, so the bottom surface of damp rot. Storage should always pay attention to the cable head is intact. 
⒍ cable shelf-life period is limited to products manufactured, usually not more than a year and a half, no longer than two years. 
Fourth, wire and cable installation and construction 
Design and construction of wire and cable installation shall be laying the relevant provisions of GB 50217-94 "Power Engineering cable design specifications," etc., and to adopt the necessary cable accessories (terminals and connectors). Power system operation quality, safety and reliability of wire and cable itself not only with the quality, but also with construction quality cable accessories and related lines. 
Through statistical analysis of line faults, due to the construction, installation and connection failures caused by such factors often much greater than the probability of failure caused by faulty wire and cable body. Therefore, to correctly use wire and cable and related accessories, in addition to regulatory requirements for the design and construction, we must also pay attention to the following aspects of the problem: 
⒈ cabling installed by a qualified professional units or professionals, do not comply with the specification requirements of construction and installation, it may lead cable system can not function properly. 
⒉ manpower when laying cable, should be unified command and control tempo, every 1.5 to 3 m cable with one shoulder, side discharge side pull, slowly cast. 
⒊ mechanical cast cable, cable laying machines generally use a dedicated and equipped with the necessary tools traction, traction size appropriate control evenly, so as not to damage the cable. 
⒋ cast before cable, to check whether the cable appearance and head intact, note the direction of rotation of the cable tray when cast, not crushed or scratch the cable sheath, in the winter when low temperatures do not beat the way to school with straight cable, avoid insulation, sheathing cracking. 
⒌ laying cable bend radius is greater than a predetermined value. Before laying the cable installation, the insulation resistance between the rear with 1000V megger cable conductors are normal, and according to the cable model specifications, different length and ambient temperature on the measurement results be properly corrected, the small size (10mm 2 following solid core conductor) cable should measure whether the conductor-off. 
⒍ such as burying cable, pay attention to soil conditions, general building cable burial depth of not less than 0.3 meters, soft, or the surrounding environment more complex, such as arable land, buildings or roads, construction sites, there should be some buried depth (0.7 to 1 meter) to prevent accidental damage to buried cable, if necessary to erect signs.

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