Overhead cable introduction (full name overhead insulated cable) is an overhead wire equipped with an insulating layer and a protective sheath. It is a special cable manufactured by a production process similar to cross-linked cables. It is between overhead wires and underground cables. The new power transmission method overhead cables are all single-core. According to their different structures, they can be divided into hard aluminum wire structure, hard drawn copper wire structure, aluminum alloy wire structure, steel core or aluminum alloy core support structure and self-supporting three-core Textured structure (the core can be hard aluminum or hard copper wire) and so on.
1. High power supply reliability. The use of overhead cables can greatly reduce various short-circuit faults (especially the common flashover faults of overhead bare wires). Compared with overhead bare wires, the failure rate is 4-6 times lower.
2. The safety of power supply is good. The use of overhead cables can greatly reduce the accidents of personal injury and death due to electric shock. The Shanghai Electric Cable Research Institute once set up a special subject to carry out the “Research and Test on Personal Safety of Overhead Cable Insulation”. Tests and calculations show that even if the insulated surface of a live cable is touched by hand, the induced current is less than 0.1mA (10kV) and 0.2mA (35kV), which is much lower than the 50-100mA lethal standard stipulated by the national electrical safety regulations.
3. Convenient erection and maintenance. Overhead cables can be erected on any kind of poles or towers, or along walls. Under special circumstances, they can also run through bushes and be directly fixed on tree poles with hardware. It can be erected on a single circuit, or multiple circuits can be erected on the same pole, without requiring a wide “electrical corridor”.
4. Reasonable economy
Although the use of overhead cables is more expensive than the use of overhead bare wires, it is cheaper than ordinary underground installation cables.