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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 ...
A "4-way" (intermediate) switch is a purpose built double pole, double throw (DPDT) switch, internally wired in manufacture to reverse the connections between the input and output and having only four external terminals. This switch has two pairs of "traveler" terminals that it connects either straight through, or crossed over (transposed, or ...
This is distinct from the local wiring between high-voltage substations and customers, which is typically referred to as electric power distribution. The combined transmission and distribution network is part of electricity delivery, known as the electrical grid. Efficient long-distance transmission of electric power requires high voltages.
Between the generating station and consumer, electric power may flow through several substations at different voltage levels. A substation may include transformers to change voltage levels between high transmission voltages and lower distribution voltages, or at the interconnection of two different transmission voltages. They are a common ...
A telegraph line between two telegraph offices, like all electrical circuits, requires two conductors to form a complete circuit. This usually means two distinct metal wires in the circuit, but in the earth-return circuit one of these is replaced by connections to earth (also called ground) to complete the circuit. Connection to earth is made ...
A disadvantage of double circuit transmission lines is that maintenance can be difficult, as either work in close proximity of high voltage or switch-off of two circuits is required. In case of failure, both systems can be affected. The largest double-circuit transmission line is the Kita-Iwaki Powerline.
Dead-end towers may be used at a substation as a transition to a "slack span" entering the equipment, when the circuit changes to a buried cable, when a transmission line changes direction by more than a few degrees, or at intervals along a straight run to limit the extent of a catastrophic collapse. Strain pylons and an anchor gantry