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1. What requirements should the design of cable joints and intermediate heads meet? The requirements to be met are:
(1) High compressive strength, good conductor connection;
(2) large mechanical strength, small medium loss;
(3) Simple structure, strong sealing.
2. Where are the inner shielding layer and outer shielding layer of the power cable? What material is used? What does it do?
In order to make the insulation layer and the cable conductor have better contact and eliminate the increase in the electric field strength of the conductor surface caused by the unsmoothness of the conductor surface, the conductor surface is generally covered with an internal shielding layer of metalized paper or semiconductor paper tape. In order to make the insulation layer and the metal sheath have better contact, there is generally an outer shielding layer on the surface of the insulation layer. The outer screen layer is the same material as the inner screen layer, and sometimes copper tape or braided copper wire tape is tied outside.
3. Which aspects should be considered in choosing the section of power cable? The following aspects should be considered:
(1) The working current allowed through the cable for a long time;
(2) Thermal stability once short-circuited;
(3) The voltage drop on the line cannot exceed the allowable working range.
4. cable in the transportation and loading process should pay attention to what?
(1) In the transportation and loading process, the cable and cable tray should not be damaged, it is strictly prohibited to push the cable tray directly from the car, the cable should not be flat transport, flat storage.
(2) Before transporting or rolling the cable tray, it must be ensured that the cable tray is firm, the oil pipe between the cable wound and the oil-filled cable and the pressure tank should be fixed and not damaged, the pressure tank should be firm, and the pressure indication should meet the requirements.
5. What are the requirements for bending the cable core when making the cable head?
When bending the wire core, the paper insulation shall not be damaged, and the bending radius of the core wire shall not be less than 10 times that of the cable core. Special care should be taken when making, and the bending part of the wire core should be evenly stressed, otherwise it is easy to damage the insulation paper.
6. briefly describe the plastic cable heat shrink sealing method.
The heat shrink method is suitable for the sealing of medium and low voltage rubber and plastic cable joints and terminal heads, and can also be applied to non-dripping and viscous impregnated insulated cables. Two kinds of heat shrinkable tubes, crosslinked polyethylene type and silicone rubber type, which can shrink evenly when exposed to heat, are adopted. The tube is covered in the predetermined adhesive sealing part, and the adhesive part is coated with hot melt adhesive, when heated to a certain temperature, the heat shrink tube will shrink, and the hot melt adhesive will melt, and a good sealing layer will be formed after natural cooling.
7. What should be paid attention to when bending cable protection tubes with electric pipe bending machine?
(1) The pipe bending machine should be operated by personnel who understand its performance and are familiar with the operation knowledge;
(2) It must be checked before use, the button, the operation handle, the stroke switch should be in good condition, and the pipe bender must be reliably grounded;
(3) Select the mold that meets the requirements and determine the required bending radius;
(4) There should be sufficient scope of activity around the construction site;
(5) When the idling is normal, it can work with load. During operation, it is forbidden to touch the rotating part with hands and feet;
(6) After the work is completed, the power should be cut off in time to release the oil pressure.
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