What is an overhead cable?
What is an overhead cable?
Aerial cable (full name overhead insulated cable) is an overhead conductor with an insulating layer and a protective sheath. It is a special cable manufactured by a production process similar to cross-linked cables, and is a new transmission method between overhead wires and underground cables.
1. Aerial cables (can simplify the structure of line towers, and even lay along walls, which not only saves line materials, but also beautifies city streets.
2. Overhead cables (conducive to improving the safety and reliability of the power distribution system, greatly reducing the risk of personal electric shock casualties. Insulated conductors can prevent interphase short circuits caused by foreign objects, reduce the number of power outages in the operation of connecting rod lines, and reduce maintenance workloads , improve the power utilization of the line.
3. Save the power loss of the line and reduce the voltage loss. The reactance of this line is only 1/3 of that of ordinary bare wires.
4. Go deep into the high-voltage load center to improve voltage quality and reduce power loss.
5. Reduce the gravity requirement of the line, reduce the input of accessories, and reduce the labor intensity of the workers to erect the line.
6. It saves the space occupied by overhead lines and facilitates the passage of overhead lines in narrow passages. Line corridors are reduced, which can be reduced by 1/2 compared to overhead bare lines.
7. Reduce wire corrosion, thereby correspondingly improving the service life of the line and the reliability of power distribution.
8. The insulation requirements for line supports are reduced, and the number of lines on the same tower is increased. Due to the improvement of line technology, the maintenance workload is reduced, the maintenance cycle is prolonged, and the time of power failure due to maintenance is reduced.
Aerial cable environmental requirements
1. When laying overhead cables (, the ambient temperature should not be lower than -20°C. When laying below -20°C, the cables must be preheated.
2. When laying overhead cables, the bending radius of the rated voltage 1kV overhead insulated cable is not less than 6 times the outer diameter of the cable, and the bending radius of the 101kV and 35KV overhead insulated cables is not less than 15 times the outer diameter.
3. The cable erection method is the same as the bare overhead line, and it still needs to be fixed on the cross arm insulator, but the distance can be appropriately reduced.
4. Cables should be used with specially designed overhead insulated cable metal appliances.
5. During the laying and storage process, attention should be paid to the sealing of the cable end to prevent the cable from entering water and reducing its performance.
6. The long-term operating temperature of overhead cables (that is, the long-term allowable working temperature of the cable conductor core), cross-linked polyethylene insulation does not exceed 90 ° C, high-density polyethylene insulation does not exceed 75 ° C; polyethylene and polyvinyl chloride insulation should not exceed 70℃; the insulation of XLPE shall not exceed 250℃ during short circuit; the insulation of HDPE and PVC shall not exceed 150℃, and the duration shall not exceed 5 seconds.