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Experts teach you how to see the wire cable

2018-06-07
First, the general principles of wire and cable selection:

In the selection of wire and cable, generally pay attention to wire and cable models, specifications (conductor section) choice.

1. The choice of wire and cable:

When using wire and cable, consider the use, laying conditions and safety; for example,

According to different uses, power cables, overhead insulated cables, control cables, etc. may be used;

According to the different laying conditions, general plastic insulated cables, steel tape armored cables, steel wire armored cables, anti-corrosion cables, etc. can be selected.

According to the safety requirements, non-flammable cables, flame-retardant cables, halogen-free flame-retardant cables, fire-resistant cables, etc. may be selected.

2. Selection of wire and cable specifications When determining the usage specifications (conductor cross-section) of wire and cable, heat, voltage loss, economical current density, and mechanical strength should generally be considered.

According to experience, the low voltage power line has a large load current, so generally select the cross section first according to the heat conditions, and then check its voltage loss and mechanical strength; low voltage lighting line can first press the allowable voltage loss condition because of its higher voltage level requirements. Select the section, and then check the heating conditions and mechanical strength; for high-voltage lines, first select the section according to the economic current density, and then check its heating conditions and allowable voltage loss; and high-voltage overhead lines, should also check the mechanical strength. If the user has no experience, they should consult the relevant professional unit or person.

Description: 1. The same specification of aluminum core wire carrying capacity is about 0.7 times that of copper core, the use of aluminum core wire can be larger than the copper core wire a specification, cross-linked polyethylene insulation can use a small file size, fire-resistant wire and cable should be selected Large size.

2. The calculation capacity of this table is based on the three-phase 380V and Cosφ=0.85. If the single-phase 220V and Cosφ=0.85, the capacity should be ×1/3.

3. When the ambient temperature is higher or the surface coating method is adopted, the safe ampacity will be reduced. At this time, larger specifications should be used. When used for chopper motors, two to three specifications should be used.

4. The PVC insulated wire of this watch is calculated according to the single overhead laying method. If it is a pipe or a plurality of laying pipes, 2~3 specifications shall be selected.

5 The above data is for reference only. The final design and determination of the cable type and specification should refer to the relevant professional information or the electrician's manual.

Second, the use of wire and cable properties


Product features See specific product catalog.

Third, wire and cable transport and storage 1. During transportation, it is strictly prohibited to drop cables or cable reels from high places, especially at lower temperatures (generally around 5°C and below), it is possible to throw or drop cables. Causes insulation, sheath cracking.

2. Avoid storing cables in the open air as much as possible. The cable trays must not be laid flat.

3. When lifting packages, it is forbidden to lift several packages at the same time. On vehicles, ships, etc., cable trays must be secured by suitable methods to prevent them from colliding or falling over each other to prevent mechanical damage to the cables.

4. The cable must not be in contact with acids, alkalis, or mineral oils. It must be stored in isolation from these corrosive substances. There must be no hazardous gases that can damage the insulation and corrode metals in the storage cable warehouse.

5. The cable should be rolled periodically during storage (3 months in summer and other days may be extended as appropriate). When rolling, place the tray side down and turn it upwards to prevent the bottom surface from getting damp and rot. Always pay attention to whether the cable gland is intact during storage.

6. The shelf life of the cable is limited to the time of the product's delivery. It is generally not more than one and a half years and not more than two years.

Fourth,
the design and construction of wire and cable installation and construction

wire cabling installed in accordance with relevant provisions of GB50217-94 "design specification power cables," etc., and to adopt the necessary cable accessories (terminals and connectors) . The operation quality, safety and reliability of the power supply system are not only related to the quality of the wire and cable itself, but also related to the construction quality of the cable accessories and lines.

Through statistical analysis of line faults, faults caused by construction, installation, connection, and other factors are often much more likely to be caused by defects in the wire and cable body. Therefore, in order to correctly select the wire and cable and supporting accessories, in addition to the design and construction in accordance with the specifications, the following issues should also be noted:

1. Installation and installation of cables shall be conducted by qualified professional units or professionals. Construction and installation that do not meet the requirements of the relevant specifications may result in the cable systems not operating properly.

2. When laying cables for humans, the command and control rhythm should be unified. Every 1.5 to 3 meters, one person shoulders the cable and pulls it slowly and slowly.

3. When the cable is mechanically applied, a special cable laying machine is generally used and equipped with necessary traction tools. The traction force is appropriate and uniform in control so as not to damage the cable.

4.Before releasing the cable, check the appearance of the cable and whether the sealing head is intact. Pay attention to the direction of rotation of the cable tray when it is applied. Do not flatten or scratch the outer sheath of the cable. Do not try to straighten the cable during the winter when the temperature is low. In order to avoid insulation, sheath cracking.

5. The bending radius of the cable when laying is greater than the specified value. Before and after the cable laying installation, measure the insulation resistance between the conductors of the cable with a 1000V Megohmmeter, and correct the measurement results according to the cable model specifications, length and ambient temperature. Small size (10mm2 or less solid core) The conductor) cable should also measure whether the conductor is open or not.

6. If the cable is laid directly, pay attention to the soil conditions. Generally, the buried depth of the cable under the building shall not be less than 0.3 meters. The softer or more complex surrounding environment, such as cultivated land, construction sites or roads, shall have a certain degree of burial. Depth (0.7 to 1 m) to prevent accidental damage to the buried cable. Significant signs should be erected when necessary.
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