27.1 : 伝送線路設計の考慮事項

Aluminum, being abundant and cost-effective, has largely replaced copper in overhead transmission lines. The popular steel-reinforced aluminum conductor consists of layers of aluminum strands around a steel core.

Other types include all-aluminum, all-aluminum alloy, aluminum conductor alloy-reinforced, and aluminum-clad steel conductors. Aluminum conductors with steel support and gap-type ZT-aluminum conductors can operate above 150ºC. The electrical design for transmission lines considers conductor type, size,  bundle number per phase, thermal capacity, voltage gradient control, insulator discs, clearance, and line insulation. Shield wires intercept lightning strikes and reduce tower footing resistance.

Transmission lines operating above 69 kV use suspension-type insulators, typically made of porcelain, toughened glass, or polymer discs.

Structures supporting these lines range from lattice steel towers for high voltages to wooden frames for lower voltages.

The mechanical design ensures stability, while environmental considerations account for land use and visual impact.