Overhead wire and cable, originally refers to the bare wire erected in the air with air insulation, mainly used as the trunk line of transmission lines or for special purposes. In the past ten years, in order to improve the safety of power transmission, the urban network transformation has changed the overhead bare wires to overhead insulated cables. Therefore, overhead wires and cables do not just refer to bare wires.
Feature of Overhead Cables
An important feature or requirement of overhead wires and cables is that the ratio of tensile force per unit weight and the unit weight ratio of the current carrying capacity is higher. Bigger is better. From this point of view, it is not difficult to draw the following conclusions from the comparison of various overhead wires and cables: copper is not as good as aluminum, pure aluminum is not as good as aluminum alloy, and the most classic overhead conductor.
Among several overhead conductors, the aluminum-clad steel-cored aluminum alloy stranded wire has the largest tensile force ratio. Copper stranded wire is defeated due to its small unit weight ratio, but due to its high conductivity and large current carrying capacity, it is also used in short sections in some power equipment.
Application of Expanded Diameter Wire
Therefore, the expanded diameter wire has the advantages of energy saving, consumption reduction and environmental protection, and is a kind of wire with great application prospects. Traditionally, this kind of wire is mostly used for ultra-high voltage transmission short lines in substations.
There are two common types of structures for expanded diameter wires: one is hollow expanded diameter wire. And the other is sparsely twisted expanded diameter wire. Because the hollow hose with hollow expanded diameter wire is extremely susceptible to corrosion.
It is rotten, has a short service life, and has tended to be eliminated. Now more sparse twisted structures are used. The so-called sparsely twisted structure means that the inner layer of aluminum wires is not full, so as to achieve the effect of diameter expansion. Since there is no standard specification, the current expanded conductors are not uniform in terms of structure and performance.
In addition, there are some special overhead bare wires, such as anti-ice and snow wires, self-damping wires, double-capacity wires and optical fiber composite overhead ground wires (OPGW), because the lack of standard specifications and the lack of sufficient overhead bare wires in coastal areas due to air pollution.
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