Electric power industry
The electric power industry covers the generation, transmission, distribution and sale of electric power to the general public and industry. The commercial distribution of electric power started in 1882 when electricity was produced for electric lighting. In the 1880s and 1890s, growing economic and safety concerns lead to the regulation of the industry. What was once an expensive novelty limited to the most densely populated areas, reliable and economical electric power has become an essential aspect for normal operation of all elements of developed economies.
By the middle of the 20th century, electricity was seen as a "natural monopoly", only efficient if a restricted number of organizations participated in the market; in some areas, vertically integrated companies provide all stages from generation to retail, and only governmental supervision regulated the rate of return and cost structure.
Since the 1990s, many regions have broken up the generation and distribution of electric power. While such markets can be abusively manipulated with consequent adverse price and reliability impact to consumers, generally competitive production of electrical energy leads to worthwhile improvements in efficiency. However, transmission and distribution are harder problems since returns on investment are not as easy to find.
History
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. 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 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 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.
File:Pylône haute tension.JPG|thumb|upright|right|High tension line in Montreal, Quebec, Canada
The AC power system used today developed rapidly, backed by industrialists such as George Westinghouse with Mikhail Dolivo-Dobrovolsky, Galileo Ferraris, Sebastian Ziani de Ferranti, Lucien Gaulard, John Dixon Gibbs, Carl Wilhelm Siemens, William Stanley Jr., Nikola Tesla, and others contributed to this field.
Power electronics is the application of solid-state electronics to the control and conversion of electric power. Power electronics started with the development of the mercury arc rectifier in 1902, used to convert AC into DC. From the 1920s on, research continued on applying thyratrons and grid-controlled mercury arc valves to power transmission. Grading electrodes made them suitable for high voltage direct current power transmission. In 1933, selenium rectifiers were invented. Transistor technology dates back to 1947, with the invention of the point-contact transistor, which was followed by the bipolar junction transistor in 1948. By the 1950s, higher power semiconductor diodes became available and started replacing vacuum tubes. In 1956, the silicon controlled rectifier was introduced, increasing the range of power electronic applications.
A breakthrough in power electronics came with the invention of the MOSFET 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. 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
The electric power industry is commonly split up into four processes. These are electricity generation such as a power station, electric power transmission, electricity distribution and electricity retailing. In many countries, electric power companies own the whole infrastructure from generating stations to transmission and distribution infrastructure. For this reason, electric power is viewed as a natural monopoly. The industry is generally heavily regulated, often with price controls and is frequently government-owned and operated. However, the modern trend has been growing deregulation in at least the latter two processes.The nature and state of market reform of the electricity market often determines whether electric companies are able to be involved in just some of these processes without having to own the entire infrastructure, or citizens choose which components of infrastructure to patronise. In countries where electricity provision is deregulated, end-users of electricity may opt for more costly green electricity.
Generation
Generation is the conversion of some primary energy source into electric power suitable for commercial use on an electrical grid. Most commercial electric power is produced by rotating electrical machines, "generators", which move conductors through a magnetic field to produce electric current. The generator is rotated by some other prime mover machine; in typical grid-connected generators this is a steam turbine, a gas turbine, or a hydraulic turbine. Primary energy sources for these machine are often fossil fuels, nuclear fission, geothermal steam, or falling water. Renewable sources such as wind and solar energy are increasingly of commercial importance.Since electrical generation must be closely matched with electrical consumption, enough generation capacity must be installed to meet peak demands. At the same time, primary energy sources must be selected to minimize the cost of produced electrical energy. Generally the lowest-incremental-cost source of electrical energy will be the next unit connected to meet rising demand. Electrical generators have automatic controls to regulate the power fed into the electrical transmission system, adjusting generator output moment by moment to balance with electrical demand. For a large grid with scores or hundreds of generators connected and thousands of loads, management of stable generator supply is a problem with significant challenges, to meet economic, environmental and reliability requirements. For example, low-incremental-cost generation sources such as nuclear power plants may be run continually to meet the average "base load" of the connected system, whereas more costly peaking power plants such as natural gas turbines may be run for brief times during the day to meet peak loads. Alternatively, load management strategies may encourage more even demand for electrical power and reduce costly peaks. Designated generator units for a particular electrical grid may be run at partial output only, to provide "spinning reserve" for sudden increases in demand or faults with other generating units.
In addition to electrical power production, electrical generation units may provide other ancillary services to the electrical grid, such as frequency control, reactive power, and black start of a collapsed power grid. These ancillary services may be commercially valuable when the generation, transmission, and distribution electrical companies are separate commercial entities.