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A grounded wire is sometimes strung along the tops of the towers to provide lightning protection. An optical ground wire is a more advanced version with embedded optical fibers for communication. Overhead wire markers can be mounted on the ground wire to meet International Civil Aviation Organization recommendations. [7]
Long-distance transmission is typically done with overhead lines at voltages of 115 to 1,200 kV. At higher voltages, where more than 2,000 kV exists between conductor and ground, corona discharge losses are so large that they can offset the lower resistive
Conventional 2-wire or 3-wire distribution lines have a higher power transfer capacity, but can require 7 poles per kilometre (12 poles per mile), with spans of 100 to 150 metres (110 to 160 yards). SWER's high line voltage and low current also permits the use of low-cost galvanized steel wire (historically, No. 8 fence wire). [ 9 ]
Rural electrification systems tend to use higher distribution voltages because of the longer distances covered by distribution lines (see Rural Electrification Administration). 7.2, 12.47, 25, and 34.5 kV distribution is common in the United States; 11 kV and 33 kV are common in the UK, Australia and New Zealand; 11 kV and 22 kV are common in ...
Unlike simple overhead wires, in which the uninsulated wire is attached by clamps to closely spaced crosswires supported by poles, catenary systems use at least two wires. The catenary or messenger wire is hung at a specific tension between line structures, and a second wire is held in tension by the messenger wire, attached to it at frequent ...
Transmission tower in Toronto, ON Single-circuit three-phase transmission line Transmission towers on a hill field. Three-phase electric power systems are used for high voltage (66- or 69-kV and above) and extra-high voltage (110- or 115-kV and above; most often 138- or 230-kV and above in contemporary systems) AC transmission lines.
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Substations often use busbars as conductors between electrical equipment. Busbars may be aluminum tubing 3–6 inches (76–152 mm) thick, or else wires (strain bus). [33] Outdoor, above-ground substation structures include wood pole, lattice metal tower, and tubular metal structures, although other variants are available.