Thirty cable common problem knowledge popularization（3）
11. What should be stated on the cable sign? What are the requirements for writing?
Answer: The cable line design number, cable model, specification and starting point should be indicated on the signboard. Cables used in parallel should have sequence numbers. The handwriting is required to be clear and not easy to fall off.
12. How should the yellow wax silk ribbon, black glass paint ribbon, alkali-free glass ribbon, etc. used for making cable joints be dehumidified before construction?
Answer: ① Constant temperature drying method: roll the insulating tape into a small roll with a diameter of 25~30mm, put it into a constant temperature drying oven at 110~120℃ for 4~5 hours, cool and dry, take it out, and put it into a dry sealed cylinder.
②Oil immersion moisture drainage method: Put the small roll of insulation tape into the cable oil with a constant temperature of 120~130℃, keep a distance of 30mm from the bottom of the pot. After a certain period of time, the oil surface will no longer produce foam, take it out, and put it into the stored cable. In oil barrels, the oil level should exceed all contained objects and be sealed.
13. What is the function of the cable outer sheath?
Answer: Protect the inner protective layer from mechanical damage and chemical corrosion and enhance mechanical strength.
14. What requirements should outdoor cable trenches meet?
Answer: The upper part of the cable trench should be slightly higher than the ground and covered with a concrete cover. The cables should be laid flat on the bracket and have good drainage pipes.
15. What is the function of the inner sheath of the cable?
Answer: Keep the insulation layer from coming into contact with water, air or other objects, prevent the insulation from getting damp and prevent the insulation layer from mechanical damage.
16. What should you pay attention to when using wire cutters?
Answer: Before use, be sure to check whether the insulation of the insulated handle is intact. Do not use wire cutters to cut metal wires exceeding the specifications allowed. It is also prohibited to use wire cutters instead of hammers to hit the tool to avoid damage.
17. What is insulation strength?
Answer: When an insulating material is in an electric field, it will be broken down when the electric field intensity increases to a certain limit. This electric field intensity that leads to insulation breakdown is called insulation strength.