Basic knowledge of wires and cables

1. What types of commonly used wires and cables are classified by purpose?

Answer: According to the purpose, it can be divided into bare wires, insulated wires, heat resistant wires, shielded wires, power cables, control cables, communication cables, radio frequency cables, etc.

2. What are the types of insulated wires?

Answer: Common types of insulated wires include the following: PVC insulated wires, PVC insulated flexible wires, nitrile PVC mixture insulated flexible wires, rubber insulated wires, agricultural underground buried aluminum core plastic insulated wires, rubber insulated cotton yarn textile flexible wires, PVC insulated nylon sheathed wires, PVC insulated flexible wires for power and lighting, etc.

3. Where is the cable tray suitable?

Answer: Cable trays are suitable for indoor and outdoor overhead laying of power cables and control cables in general industrial and mining enterprises, and can also be used for indoor and outdoor installation in telecommunications, radio and television departments.

4. What are the cable accessories?

Answer: Common electrical accessories include cable terminal boxes, cable intermediate junction boxes, connecting pipes and terminals, steel plate wiring slots, cable trays, etc.

5. What is a cable intermediate joint?

Answer: The device that connects the conductor, insulation shield, and protective layer of a cable to connect the cable line is called a cable intermediate joint.

6. What is the main electrical connection?

Answer: The main electrical wiring is the connection method of main electrical equipment and buses in power plants and substations, including the connection method of main bus and auxiliary power system according to certain functional requirements.

7. What regulations should be followed when selecting the cross-section of power cables?

Answer: The selection of power cables should follow the following principles: ① The rated voltage of the cable should be greater than or equal to the rated voltage of the power supply system at the installation point; ② The continuous allowable current of the cable shall be equal to or greater than the maximum continuous current of the power supply load; ③ The cross-section of the wire core shall meet the stability requirements of the power supply system during short circuit; ④ Check whether the voltage drop meets the requirements according to the cable length; ⑤ The minimum short circuit current at the end of the line should enable reliable operation of the protection device.

8. What are the advantages of cross-linked polyethylene cables compared to oil-paper cables?

Answer: ① Easy to install because it allows for a small minimum bending radius and light weight; ② Not limited by line drop; ③ Good thermal performance, high allowable operating temperature, and large transmission capacity; ④ The cable accessories are simple and all of them are of dry structure; ⑤ Simple operation and maintenance without oil leakage; ⑥ Low price; ⑦ High reliability and low failure rate; ⑧ Less manufacturing processes, simple process, and significant economic benefits.

9. What are the requirements for fixing clamps for AC single core cables? Why?

Answer: The clamp should have no iron parts to form a closed magnetic circuit, because when the cable core passes through the current, magnetic lines of force are generated around it, which are proportional to the amount of current passing through the cable core,  If magnetic conductive materials such as iron are used, it can be known from electromagnetic induction that eddy currents will be generated in the iron to heat the cable, or even burn the cable.  Therefore, iron parts cannot be used as fixing clamps for single core AC cables.

10. What are the biggest features and advantages of the following accessories for heat shrinkable cable heads?

Answer: The biggest feature of heat shrinkable accessories is to replace traditional stress cones with stress tubes, which not only simplifies the construction process, but also reduces the size of the terminal of the joint,  Convenient installation, time and labor saving, superior performance, and metal saving. The heat shrinkable cable accessory integrates the advantages of the perfusion type and the dry package type.