Overhead cables are not simply ordinary paper-insulated or cross-linked insulated cables hung directly on overhead towers. Instead, they are specialized cables manufactured using a process similar to that of cross-linked cables.
Generally, overhead cables are single-core. Based on their structure, they can be categorized into hard aluminum wire structure, hard-drawn copper wire structure, aluminum alloy wire structure, steel core or aluminum alloy core supported structure, and self-supporting three-core composite structure (the core can be hard aluminum or hard copper wire), etc.
Hard aluminum wire structures are lightweight, have moderate tensile strength, are easy to bend, convenient to install, and have low project costs. They can be easily installed on existing towers and are commonly used in renovation or new construction projects.
Hard-drawn copper wire structures are heavier but have high tensile strength and strong resistance to external forces; the cable can even continue to carry power when the tower breaks. Aluminum alloy wire structures are lightweight and have high tensile strength, mainly used in long-span tower systems with spans up to 100m.
Steel-core or aluminum alloy-core supported structures are generally used in 35kV voltage systems with relatively large spans. Square insulators separate the support wire (bare wire) from the three insulated phase wires. The support wire can also be used as a lightning protection wire. Its biggest advantage is its small sag, with the arc weight only about 2.4% of the span.
Self-supporting three-core stranded structures are used in systems with medium spans. The disadvantages of this type of cable are: the manufacturing length of three-core cables is shorter than that of single-core cables, there are more joints, and it has an external semi-conductive shielding layer. At the cable end, a termination or stress cone structure must be installed like that of ordinary cables.