But the mid-1880s saw a breakthrough with the development of functional transformers that allowed AC power to be "stepped up" to much a higher voltage for transmission, then dropped down to a lower voltage near the end user. The problem of transmitting electricity over longer distances became a recognized engineering roadblock to electric power distribution, with many less-than-satisfactory solutions tested by lighting companies. In practice, Edison's DC generating plants needed to be within about 1.5 miles (2.4 km) of the farthest customer to avoid even thicker, more expensive conductors. This low voltage translated to higher current, requiring thick copper cables for transmission. This was due to the low voltage (110 V) it used throughout, from generation to end use. By contrast, direct-current indoor incandescent lighting systems, for example Edison's first power station, installed in 1882, had difficulty supplying customers more than a mile away. And each doubling of voltage would allow a given cable to transmit the same amount of power four times the distance than at the lower voltage (with the same power loss). Both were supplanting gas lighting systems, with arc lighting taking over large-area and street lighting, and incandescent lighting replacing gas lights for business and residential users.ĭue to the high voltages used in arc lighting, a single generating station could supply a long string of lights, up to 7 miles (11 km) long. The first power-distribution systems installed in European and US cities were used to supply lighting: arc lighting running on very-high-voltage (around 3,000 V) alternating current (AC) or direct current (DC), and incandescent lighting running on low-voltage (100 V) direct current. Before that, electricity was usually generated where it was used. History įurther information: History of electric power transmission The late 1870s and early 1880s saw the introduction of arc-lamp lighting used outdoors or in large indoor spaces, such as this Brush Electric Company system installed in 1880 in New York City.Įlectric power distribution didn't become necessary until the 1880s when electricity started being generated at power stations. The final circuit in an urban system may be less than 15 metres (50 ft), but may be over 91 metres (300 ft) for a rural customer. The power comes to the customer via a service drop and an electricity meter. Ĭloser to the customer, a distribution transformer steps the primary distribution power down to a low-voltage secondary circuit, usually 120/240 V in the US for residential customers. Rural distribution is mostly above ground with utility poles, and suburban distribution is a mix. Urban distribution is mainly underground, sometimes in common utility ducts. The bus distributes power to distribution lines, which fan out to customers.
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