UL Certification Knowledge of Environmental Protection for Wire and Cable and Heat-shrinkable Cable Accessories and Heat-shrinkable Pipes
1. What kinds of wires and cables are commonly used according to their uses?
It can be divided into bare conductors, insulated wires, heat-resistant wires, shielded wires, power cables, control cables, communication cables, radio frequency cables and so on.
2. What kinds of insulated wires are there?
There are several kinds of common insulated wires: PVC insulated wires, PVC insulated flexible wires, NBR-PVC mixed insulated flexible wires, rubber insulated wires, agricultural underground directly buried aluminium-cored 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 bridge suitable for?
Cable bridge is suitable for laying power cables and control cables indoor and outdoor in general industrial and mining enterprises. It can also be used for indoor and outdoor installation in telecommunications, radio and television departments.
4. What are the cable accessories?
Commonly used thermal shrinkable cable accessories are cable terminal junction box, cable intermediate junction box, connecting pipe and terminal, steel plate junction slot, cable bridge, etc.
5. What is cable intermediate joint?
The device that connects the cable to the conductor, insulating shielding layer and protective layer of the cable, so as to connect the thermal shrinkable pipeline of the cable, is called the cable intermediate joint.
6. What is the main electrical connection?
Electrical main wiring is the connection mode of main electrical equipment and busbar in power plant and substation, including the connection mode of main busbar and auxiliary power system according to certain functional requirements.
7. What regulations should be followed in selecting the section of power cable?
The selection of power cables should follow the following principles:
(1) The rated voltage of the cable shall be greater than or equal to the rated voltage of the power supply system at the installation point;
(2) The permissible current of the cable shall be equal to or greater than the maximum permissible current of the power supply load.
(3) Core section should satisfy the stability requirement of power supply system in short circuit.
(4) Check whether the voltage drop meets the requirements according to the length of the cable;
(5) The minimum short-circuit current at the end of the line should enable the protection device to operate reliably.
8. What are the advantages of XLPE cable compared with oil-paper cable?
(1) Easy to install, because it allows the minimum bending radius to be small and the weight to be light;
(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 dry.
(5) Simple operation and maintenance, no oil leakage;
(6) Low prices;
(7) High reliability and low failure rate;
(8) There are few manufacturing processes, simple processes and remarkable economic benefits.
9. What are the requirements of fixtures for fixing AC single-core cables? Why?
Answer: Fixture should have no iron parts to form a closed magnetic circuit. This is because when the cable core passes through the current, it generates magnetic lines around it. The magnetic lines are proportional to the current passing through the core. If the magnetic conductive materials such as iron parts are used, according to the electromagnetic induction, eddy currents will be generated in the iron parts to heat the cable or even burn the cable. Therefore, iron can not be used as a fixture for single-core AC cable.
10. What are the greatest features and advantages of the accessories below the thermal shrinkable cable head?
Answer: The greatest feature of heat shrinkable accessories is to replace the traditional stress cone with stress tube. It not only simplifies the construction process, but also reduces the size of the terminal of the joint. It is convenient to install, time-saving and labor-saving, with superior performance and metal saving. Thermal shrinkable cable accessories are a combination of perfusion type and dry package type, which combines the advantages of these two kinds of accessories!
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