<P> A very first operative AC line was put into service in 1885 in via dei Cerchi, Rome, Italy, for public lighting . It was powered by two Siemens & Halske alternators rated 30 hp (22 kW), 2 kV at 120 Hz and used 200 series - connected Gaulard 2 - kV / 20 - V step - down transformers provided with a closed magnetic circuit, one for each lamp . Few months later it was followed by the first British AC system, which was put into service at the Grosvenor Gallery, London . It also featured Siemens alternators and 2.4 - kV / 100 - V step - down transformers, one per user, with shunt - connected primaries . </P> <P> The concept that is the basis of modern transmission using inexpensive step up and step down transformers was first implemented by Westinghouse, William Stanley, Jr. and Franklin Leonard Pope in 1886 in Great Barrington, Massachusetts, resorting also to European technology . In 1888 Westinghouse also licensed Nikola Tesla's induction motor patent giving AC a much needed usable motor . This system was developed into the modern 3 - phase system by Mikhail Dolivo - Dobrovolsky and Allgemeine Elektricitäts - Gesellschaft and Charles Eugene Lancelot Brown in Europe, starting in 1889 . The simplicity of polyphase generators and motors meant that besides their efficiency they could be manufactured cheaply, compactly and would require little attention to maintain . Simple economics would drive the expensive, balky and mechanically complex DC dynamos to their ultimate extinction . As it turned out, the deciding factor in the War of Currents was the availability of low cost step up and step down transformers that meant that all customers regardless of their specialized voltage requirements could be served at minimal cost of conversion . This "universal system" is today regarded as one of the most influential innovations for the use of electricity . </P> <P> The case for alternating current was not clear at the turn of the century and high voltage direct current transmission systems were successfully installed without the benefit of transformers . Rene Thury, who had spent six months at Edison's Menlo Park facility, understood his problem with transmission and was convinced that moving electricity over great distances was possible using direct current . He was familiar with the work of Marcel Deprez, who did early work on high voltage transmission after being inspired by the capability of arc lamp generators to support lights over great distances . Deprez avoided transformers by placing generators and loads in series as arc lamp systems of Charles F. Brush did . Thury developed this idea into the first commercial system for high - voltage DC transmission . Like Brush's dynamos, current is kept constant, and when increasing load demands more pressure, voltage is increased . The Thury System was successfully used on several DC transmission projects from Hydro generators . The first in 1885 was a low voltage system in Bözingen, and the first high voltage system went into service in 1889 in Genoa, Italy, by the Acquedotto de Ferrari - Galliera company . This system transmitted 630 kW at 14 kV DC over a circuit 120 km long . The largest Thury System was the Lyon Moutiers project that was 230 km in length, eventually delivering 20 megawatts, at 125 kV . </P> <P> Ultimately, the versatility of the Thury system was hampered by the fragility of series distribution, and the lack of a reliable DC conversion technology that would not show up until the 1940s with improvements in mercury arc valves . The AC "universal system" won by force of numbers, proliferating systems with transformers both to couple generators to high - voltage transmission lines, and to connect transmission to local distribution circuits . By a suitable choice of utility frequency, both lighting and motor loads could be served . Rotary converters and later mercury - arc valves and other rectifier equipment allowed DC load to be served by local conversion where needed . Even generating stations and loads using different frequencies could also be interconnected using rotary converters . By using common generating plants for every type of load, important economies of scale were achieved, lower overall capital investment was required, load factor on each plant was increased allowing for higher efficiency, allowing for a lower cost of energy to the consumer and increased overall use of electric power . </P>

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