of which the nearest is a Phase Transposition Tower Although electricity had been known to be produced as a result of the chemical reactions that take place in an
electrolytic cell since
Alessandro Volta developed the
voltaic pile in 1800, its production by this means was, and still is, expensive. In 1831,
Michael Faraday devised a machine that generated electricity from rotary motion, but it took almost 50 years for the technology to reach a commercially viable stage. In 1878, in the
United States,
Thomas Edison developed and sold a commercially viable replacement for gas lighting and heating using locally generated and distributed
direct current electricity.
Robert Hammond, in December 1881, demonstrated the new electric light in the
Sussex town of
Brighton in the UK for a trial period. The ensuing success of this installation enabled Hammond to put this venture on both a commercial and legal footing, as a number of shop owners wanted to use the new electric light. Thus the Hammond Electricity Supply Co. was launched. In early 1882, Edison opened the world's first steam-powered electricity generating station at
Holborn Viaduct in
London, where he had entered into an agreement with the City Corporation for a period of three months to provide street lighting. In time he had supplied a number of local consumers with electric light. The method of supply was direct current (DC). Whilst the Godalming and the 1882
Holborn Viaduct Scheme closed after a few years the Brighton Scheme continued on, and supply was in 1887 made available for 24 hours per day. It was later on in the year in September 1882 that Edison opened the
Pearl Street Power Station in
New York City and again it was a DC supply. It was for this reason that the generation was close to or on the consumer's premises as Edison had no means of voltage conversion. The voltage chosen for any electrical system is a compromise. For a given amount of power transmitted, increasing the
voltage reduces the
current and therefore reduces the required wire thickness. Unfortunately it also increases the
danger from direct contact and increases the required
insulation thickness. Furthermore, some load types were difficult or impossible to make work with higher voltages. The overall effect was that Edison's system required power stations to be within a mile of the consumers. While this could work in city centres, it would be unable to economically supply suburbs with power. The mid to late 1880s saw the introduction of
alternating current (AC) systems in Europe and the U.S. AC power had an advantage in that
transformers, installed at
power stations, could be used to raise the voltage from the generators, and transformers at local
substations could reduce voltage to supply loads. Increasing the voltage reduced the current in the transmission and distribution lines and hence the size of conductors and distribution losses. This made it more economical to distribute power over long distances. Generators (such as
hydroelectric sites) could be located far from the loads. AC and DC competed for a while, during a period called the
war of the currents. The DC system was able to claim slightly greater safety, but this difference was not great enough to overwhelm the enormous technical and economic advantages of alternating current which eventually won out.
Transistor technology dates back to 1947, with the invention of the
point-contact transistor, which was followed by the
bipolar junction transistor (BJT) in 1948. By the 1950s, higher power semiconductor
diodes became available and started replacing
vacuum tubes. In 1956, the
silicon controlled rectifier (SCR) was introduced, increasing the range of power electronic applications. A breakthrough in power electronics came with the invention of the
MOSFET (metal-oxide-semiconductor field-effect transistor) in 1959. Generations of MOSFETs enabled power designers to achieve performance and density levels not possible with bipolar transistors. In 1969,
Hitachi introduced the first vertical
power MOSFET, which would later be known as the
VMOS (V-groove MOSFET). The power MOSFET has since become the most common
power device in the world, due to its low gate drive power, fast switching speed, easy advanced paralleling capability, wide
bandwidth, ruggedness, easy drive, simple biasing, ease of application, and ease of repair. While HVDC is increasingly being used to transmit large quantities of electricity over long distances or to connect adjacent
asynchronous power systems, the bulk of electricity generation, transmission, distribution and retailing takes place using alternating current. == Organization ==