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Thus, generators were sited near their loads, a practice that later became known as distributed generation using large numbers of small generators. The question is often asked why, if population increases, there is not an increasing necessity of supplying food products; and if there is such a necessity, why can great numbers be spared from the rural districts to engage in the business undertakings of the cities? Many installations seen today were first built more than 100 years ago, some when electric traction was barely out of its diapers, so to speak, and this has had a great influence on what is seen today. Ensure the electric wire reel you buy is strong and can store the required cord length. Submarine connections up to 600 kilometres (370 mi) in length have been deployed. We have already mentioned the problem (above) of a wave being formed in the wire by a pantograph moving at high speed.

High-voltage direct current (HVDC) systems require relatively costly conversion equipment that may be economically justified for particular projects such as submarine cables and longer distance high capacity point-to-point transmission. While the price of generating capacity is high, energy demand is variable, making it often cheaper to import needed power than to generate it locally. Reliability was improved and capital costs were reduced, because stand-by generating capacity could be shared over many more customers and a wider area. The optimum size of a conductor for a given voltage and current can be estimated by Kelvin's law for conductor size, which states that size is optimal when the annual cost of energy wasted in resistance is equal to the annual capital charges of providing the conductor. Thus, reducing the current by a factor of two lowers the energy lost to conductor resistance by a factor of four for any given size of conductor. For a given amount of power, a higher voltage reduces the current and thus the resistive losses. In general, losses are estimated from the discrepancy between power produced (as reported by power plants) and power sold; the difference constitutes transmission and distribution losses, assuming no utility theft occurs.

These companies developed AC systems, but the technical difference between direct and alternating current systems required a much longer technical merger. Different classes of loads (for example, lighting, fixed motors, and traction/railway systems) required different voltages, and so used different generators and circuits. 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 losses in the line conductors. Remote and low-cost sources of energy, such as hydroelectric power or mine-mouth coal, could be exploited to further lower costs. At times of lower interest rates and low commodity costs, Kelvin's law indicates that thicker wires are optimal. Since power lines are designed for long-term use, Kelvin's law is used in conjunction with long-term estimates of the price of copper and aluminum as well as interest rates. Copper or aluminum is chosen for high electrical conductivity, while stranding gives the cable flexibility. Costs can be prohibitive for transmission lines, but high capacity, long distance super grid transmission network costs could be recovered with modest usage fees. As of 1980, the longest cost-effective distance for DC transmission was 7,000 kilometres (4,300 miles).

The first transmission of single-phase alternating current using high voltage came in Oregon in 1890 when power was delivered from a hydroelectric plant at Willamette Falls to the city of Portland 14 miles (23 km) down river. 0.10 per kWh, and multiples of retail for instantaneous suppliers at unpredicted high demand moments. Local sources (even if more expensive and infrequently used) can protect the power supply from weather and other disasters that can disconnect distant suppliers. To begin with, the electric railway needs a power supply that the trains can access at all times. The conductor carries electric signals, the insulation secures the electric circuit, and the sheath prevents unwanted chemical reactions caused by external factors. What type of protection does a cable sheath provide? These animals characteristically engage in a type of behavior called "pica". It's called a loop because the two wires, connected at one end by the switch and at the other end by your phone, allow current to flow all the way around.

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