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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 ...
An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy along large distances. It consists of one or more conductors (commonly multiples of three) suspended by towers or poles.
In this system, the current is mainly carried between the overhead line and a feeder transmission line instead of the rail. The overhead line (3) and feeder (5) are on opposite phases so the voltage between them is 50 kV, while the voltage between the overhead line (3) and the running rails (4) remains at 25 kV. Periodic autotransformers (9 ...
Primaries provide power at the standard distribution voltages used in the area; these range from as low as 2.3 kV to about 35 kV depending on local distribution practice and standards, often 11 kV (50 Hz systems) and 13.8 kV (60 Hz systems) are used, but many other voltages are standard.
Long-distance transmission (hundreds of kilometers) is cheap and efficient, with costs of US$0.005–0.02 per kWh, compared to annual averaged large producer costs of US$0.01–0.025 per kWh, retail rates upwards of US$0.10 per kWh, and multiples of retail for instantaneous suppliers at unpredicted high demand moments. [23]
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 ]
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.
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.