Iterative upgrades to overhead cables contribute to the high-quality development of distribution networks.

Overhead cables, commonly referred to as overhead conductors or overhead wiring, are specialized power transmission lines installed by suspension in the air. They are supported by infrastructure components such as utility poles, towers, crossarms, insulators, and hardware, with air serving as their primary insulating medium. Widely used in power transmission and distribution networks, they represent one of the most prevalent outdoor wiring solutions in power systems. The key distinctions between overhead cables and direct burial cables, conduit cables, and cable trays lie in their installation environment, insulation methods, and outdoor weather resistance design.

I.Main Classification and Structure:

Based on the presence or absence of an insulation layer, overhead cables can be classified into two main categories: bare overhead conductors and insulated overhead cables.

(1)Bare overhead conductor: 

The entire cable lacks an insulating sheath and consists solely of conductive metal and reinforcing structures, relying on air and spacing to achieve insulation between phases and between phase and ground.

Main Models and Structures:

1.Steel-core aluminum stranded wire (JL/G1A, JL/G2A, etc.):

The most commonly used category. It consists of a high-strength galvanized steel core that withstands mechanical tension, with an outer layer of stranded aluminum wires responsible for electrical conductivity. This design balances electrical performance with tensile strength, wind resistance, and break resistance.

2.Pure aluminum stranded wire (JL):

Made entirely of aluminum, it is lightweight and cost-effective but has low mechanical strength, making it suitable only for short-distance, low-load applications.

3.Aluminum alloy stranded wire (JLHA):

Outperforms conventional aluminum wires in conductivity, strength, and corrosion resistance, making it suitable for corrosive environments such as coastal areas and saline-alkali regions.

Key features:

Low cost, high current-carrying capacity, and excellent heat dissipation; however, being exposed to the environment makes it susceptible to external impacts, tree entanglement, bird perching-induced short circuits, and electric shock hazards, resulting in inadequate safety protection.

Application scenarios:

Main trunk networks for high-voltage and ultra-high-voltage long-distance power transmission; large-span lines in suburban areas; and long-distance power grids in mountainous regions.

(2)Overhead insulated cables (overhead insulated wires):

These feature an insulating layer extruded around the conductor, with some models additionally equipped with a sheath, serving as the primary product for low-voltage power distribution in both urban and rural areas.

Basic structure: From inside to outside, it consists of a conductor layer followed by an insulating layer; some outdoor products with stringent requirements may additionally include a protective sheath and a shielding layer.

Conductor: Typically made of pure copper, aluminum, or aluminum alloy, available in single-core or multi-core configurations;

Insulation layer: Commonly made of polyvinyl chloride (PVC), cross-linked polyethylene (XLPE), or weather-resistant polyethylene, which exhibits resistance to ultraviolet radiation and aging.

Mainstream Model：Common designations include JKV, JKYJ, and JKLYJ, where "JK" is the dedicated code for overhead lines. Among these, JKLYJ (aluminum-core cross-linked polyethylene insulated overhead line) has the widest application range.

Key features: 

Equipped with insulation protection, significantly reducing the risks of inter-phase short circuits and electric shock; suitable for dense installation, requiring less space for wiring; resistant to sunlight exposure, rain, and aging, making it ideal for long-term outdoor use; compared to bare conductors, it has a slightly lower current-carrying capacity and higher cost.

Application scenarios: Urban streets, residential communities, rural power distribution systems, outdoor low-voltage lines in industrial areas, and branch lines extending from roads to households.

II. Supporting Installation Accessories:

Overhead cables cannot be installed independently; they must be paired with specialized electrical fittings and insulation components to ensure stable line operation.

Support structures: Utility poles, transmission towers, crossarms, and clamps, used to secure the entire power line;

Insulation types: Suspension insulators, needle insulators, butterfly insulators; isolation cables and towers to prevent leakage current.

Fixed connection types: Wire clamps, tie-down clips, trench-clamped connectors, and tension-resistant clamps, used for securing conductors, connecting electrical circuits, and tightening cables.

III. Core Performance Requirements:

Due to prolonged outdoor operation, overhead cables must meet the following stringent environmental requirements:

1.Weather resistance: Resistant to ultraviolet radiation, extreme temperatures, rain exposure, frost, snow, and ice accumulation; unlikely to crack or age during prolonged outdoor use.

2.Mechanical properties: High tensile strength, capable of withstanding tension forces exerted by strong winds, typhoons, and the self-weight of power lines, ensuring minimal line breakage; exhibits adequate resistance to sagging and vibration.

3.Electrical performance: Stable insulation resistance, compliant with voltage withstand requirements, no leakage current or breakdown during operation; conductor resistance meets national standards with low transmission losses.

4.Environmental adaptability: Coastal areas require protection against salt spray corrosion; chemical processing zones demand resistance to acid and alkali erosion; cold regions necessitate low-temperature brittleness resistance.

IV. Typical Application Scenarios:

High-voltage long-distance power transmission: Main grid systems and inter-regional power transmission primarily utilize bare conductors such as steel-core aluminum stranded wires.

Urban and rural low-voltage power distribution: Household wiring in streets, communities, and villages primarily uses overhead insulated cables.

Industrial and mining plant areas: Outdoor power distribution systems within the plant premises, as well as external wiring connections for equipment;

Special terrain areas: Mountainous regions, river valleys, farmland, and other locations where underground construction is highly challenging and costly.

V. Summary of Advantages and Disadvantages:

Merit：

1.Simple construction process with short project duration, requiring no ground excavation and causing minimal damage to road surfaces and vegetation;

2.Convenient for subsequent inspection, fault diagnosis, maintenance, and replacement;

3.Overall construction cost is lower than that of underground pipeline cables, offering superior cost-effectiveness for long-distance power transmission;

4.The cable provides excellent aerial ventilation and heat dissipation, with superior current-carrying capacity at equivalent cross-sectional areas.

Shortcoming：

1.Highly susceptible to weather conditions; strong winds, lightning strikes, ice accumulation, and heavy snowfall can easily cause power line failures;

2.Exposure to the outdoors makes them vulnerable to external damage, obstruction by trees, or interference from foreign objects, compromising operational safety;

3.They occupy overhead space, detracting from urban aesthetics and limiting their use in densely populated urban areas and core commercial zones;

4. They pose electric shock hazards; residential areas require strict adherence to specified installation heights and spacing requirements.