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Wire and cable industry knowledge

November 30, 2022

Wire and cable industry knowledge

1. What do you mean by insulation strength?

A: Insulating material in the electric field, when the electric field strength increases to a certain limit will be breakdown, this leads to insulation breakdown of the electric field strength is called insulation strength.

2. What are the advantages of cross-linked heat-shrinkable cable accessories?

A: This is a new type of material, it is now compared with other types of accessories with superior electrical performance, small size, small quality, easy installation, material matching and other advantages, in addition to weather resistance, dirt resistance, flame retardant self-extinguishing ability.

3. What are the requirements for the mechanical strength of the cable conductor connection points?

A: The mechanical strength of the connection point is generally lower than the tensile strength of the cable conductor itself, for fixed laying of power cables, the tensile strength of the connection point requires no less than 60% of the tensile strength of the conductor itself.

4. the power cable insulation material should have what the main performance?

A: should have the following main properties.
(1) high breakdown strength.
(2) low dielectric loss.
(3) a fairly high insulation resistance.
(4) excellent discharge resistance.
(5) has a certain degree of flexibility and mechanical strength.
(6) long-term stability of insulation performance.

5. When laying cables mechanically, what are the traction strength provisions?
A: For copper-core cable, when traction head, the allowable traction strength of 70N/cm; for aluminum-core cable, when traction head, the allowable traction strength of 40N/cm; if the use of wire mesh traction, lead sheathed cable allowable strength of 10N/cm; lead sheathed cable for 40N/cm.

6. What are the provisions for the cable protection tube?
A: (1) the cable needs to wear protection tube laying, the inner diameter of the tube should not be less than 1.5 times the outer diameter of the cable, concrete pipe, terra cotta pipe, asbestos, cement pipe should not be less than 100mm inner diameter.
(2) The bending radius of the cable pipe shall conform to the provisions of the bending radius of the penetrated cable.
(3) each tube should not exceed a maximum of three elbows, right-angle bend should not be more than two.


7. how to measure the outer diameter of the cable sheath?

A: At five points evenly distributed around the circumference of the sheath, measure the outer diameter of the sheath and its average value, the average outer diameter of both the sheath's outer diameter.

8. How to connect the copper core cables of different cross-sections?
A: Different cross-section of copper core cable connection, can be used to open weak back copper receiver, connected by tin welding method, but also available pure copper rod according to the different cross-section requirements connected into copper receiver, connected by crimping method.

9. briefly describe the process of 10KV cross-linked cable heat-shrinkable production of indoor terminal?
A; (1) Preparation stage: check whether the heat-shrinkable cable accessories are available and whether the models match, check and confirm that the cable has no moisture after checking the cable.
(2) Excise the excess cable and decide the cable length according to the site condition.
(3) Strip the sheath.
(4) Weld the grounding wire to the steel strip.
(5) Fill the trigeminal opening and wrap around the sealant.
(6) Install the three-core branch sheath, put the sheath into the root and start shrinking from the middle, first to the root and then to the finger.

(7) Strip the copper tape and outer semi-conductive layer, strip and cut the copper tape of more than 20mm at the mouth of the three-core branch sheath, forbid to damage the main insulation, and clear the clean semi-conductive layer.
(8) install the stress tube, the mouth end of the tube part of the branch sleeve butt after heat shrinkage.
(9) Installation of terminal blocks.
(10) installation of insulation tube.
(11) installation of sealing tube.
(12) Install the phase color pipe after verification.

10. What are the installation steps for indoor and outdoor prefabricated terminals?
A: (1) Position the cable according to the intended location, fix, clean the surface, peel the outer sheath with reference to the instructions, if there is a special need, the outer sheath peeling length can be adjusted, respectively, from the copper tape, outer sheath armored lead 2 groups of ground.
(2) From the outer sheath mouth upward to measure the required size, remove the excess cable, set into the heat-shrinkable three-finger sleeve to the root of the trigeminal mouth by the middle of the heating shrinkage, from the finger sleeve upward to measure the specified size (35kv for 350 ~ 380mm). Remove the excess copper tape (retain 20mm), then retain the semiconductor predetermined location, crimp out the line terminal seal.