1、 附 录 附录 A 英文原文： history of electric power system In 1878, Thomas A. Edison began work on the electric light and formulated the concept of a centrally located power station with distributed lighting serving a surrounding area. He perfected his light by October 1879, and the opening of his historic Pe
2、arl Street Station in New York city on September 4, 1882, marked the beginning of the electric utility industry. At Pearl Street, dc generators, then called dynamos, were driven by steam engines to supply an initial load of 30kW for 110-V incandescent lighting to 59 customers in a 1-square-mile area
3、. From this beginning in 1882 through 1972, the electric utility industry grew at a remarkable pace a growth based on continuous reductions in the price of electricity due primarily to technological accomplishment and creative engineering. The introduction of the practical dc motor by Sprague electr
4、ic, as well as the growth of incandescent lighting, promoted the expansion of Edisons dc systems. The development of three-wire 220-V dc systems allowed load to increase somewhat, but as transmission distances and loads continued to increase, voltage problems were encountered. These limitations of m
5、aximum distance and load were overcome in 1885 by William Stanleys development of a commercially practical transformer. Stanley installed an ac distribution system in Great Barrington, Massachusetts, to supply 150 lamps. With the transformer, the ability to transmit power at high voltage with corres
6、ponding lower current and lower line-voltage drops made ac more attractive than dc. The first single-phase ac line in the United States operated in 1889 in Oregon, between Oregon city and Portland 21 km at 4 kV. The growth of ac systems was further encouraged in 1888 when Nikola Tesla presented a pa
7、per at a meeting of the American Institute of Electrical Engineers describing two-phase induction and synchronous motors, which made evident the advantages of polyphase versus single-phase systems. The first three-phase line in Germany became operational in 1891, transmitting power 179 km at 12 kV.
8、The first three-phase line in the United States (in California) became operational in 1893, transmitting power 12 km at 2.3 kV. The three-phase induction motor conceived by Tesla went on to become the workhorse of the industry. In the same year that Edisons steam-driven generators were inaugurated,
9、a waterwheel-driven generator was installed in Appleton, Wisconsin. Since then, most electric energy has been generated in steam-powered and in water-powered (called hydro) turbine plants. Today, steam turbines account for more than 85% of U.S. electric energy generation, whereas hydro turbine accou
10、nt for about 7%. Gas turbines are used in some cases to meet peak loads. Steam plants are fueled primarily by coal, gas, oil, and uranium. Of these, coal is the most widely used fuel in the United States due to its abundance in the country. Although many of these coal-fueled power plants were conver
11、ted to oil during the early 1970s, that trend has been reversed back to coal since the 1973/74 oil embargo, which caused an oil shortage and created a national desire to reduce dependency on foreign oil. In 1957, nuclear units with 90MW steam-turbine capacity, fueled by uranium, were installed, and
12、today nuclear units with 1312 MW steam-turbine capacity ware in service. However, the growth of nuclear capacity in the United States has been halted by rising construction costs, licensing delays, and public opinion. Starting in the 1990s, the choice of fuel for new power plants in the United State
13、s has been natural gas. The gas-fired turbine is safe, clean, more efficient than competing technologies, and uncontroversial. As of 2001, the tread toward natural gas has accelerated. It is estimated that 200 large gas-fired plants are being developed, accounting for 75-90% of planned U.S. Expansio
14、n. However, increasing natural gas prices may slow this trend. Other types of electric power generation are also being used, including wind-turbine generators； geothermal power plants, wherein energy in the form of steam or hot water is extracted from the earths upper crust； solar cell arrays； and t
15、idal power plants. These sources of energy cannot be ignored, but they are not expected to supply a large percentage of the worlds future energy needs. On the other hand, nuclear fusion energy just may. Substantial research efforts have shown nuclear fusion energy to be a promising technology for pr
16、oducing safe, pollution-free, and economical electric energy later in the 21st century and beyond. The fuel consumed in a nuclear fusion reaction in deuterium, of which a virtually inexhaustible supply is present in seawater. The early ac systems operated at various frequencies including 25, 50, 60,
17、 and 133 Hz. In 1891, it was proposed that 60 Hz be the standard frequency in the United States. In 1893, 25-Hz systems were introduced with the synchronous converter. However, these systems were used primarily for railroad electrification (and many are now retired) because they had the disadvantage
18、 of causing incandescent lights to flicker. In California, the Los Angeles Department of Power and Water operated at 50 Hz, but converted to 60 Hz when power from the Hoover Dam became operational in 1937. In 1949, Southern California Edison also converted from 50 to 60 Hz. Today, the two standard f
19、requencies for generation, transmission, and distribution of electric power in the world are 60 Hz (in the United States, Canada, Japan, Brazil) and 50 Hz ( in Europe, the former Soviet republics, South America except Brazil, India, also Japan). The advantage of 60-Hz systems is that generators, mot
20、ors, and transformers in these systems are generally smaller than 50-hz equipment with the same ratings. The advantage of 50-Hz systems is that transmission lines and transformers have smaller reactances at 50 Hz than at 60 Hz. The rate of growth of electric energy in the United States was approxima
21、tely 7% per year from 1902 to 1972. This corresponds to a doubling of electric energy consumption every 10 years over the 70-year period. In other words, every 10 years the industry installed a new electric system equal in energy-producing capacity to the total of what it had built since the industr
22、y began. The annual growth rate slowed after the oil embargo of 1973/74. Kilowatt-hour consumption in the United States increased by 3.4% per year from 1972 to 1980, and by 2.1% per year from 1980 to 2000. Along with increases in load growth, there have been continuing in creases in the size of gene
23、rating units. The principal incentive to build larger units has been economy of scale that is, a reduction in installed cost per kilowatt of capacity for larger units. However, there have also been steady improvements in generation efficiency. For example, in 1934 the average heat rate for steam gen
24、eration in the U.S. electric industry was 17,950 BTU/kWh, which corresponds to 19% efficiency. By 1991, the average heat rate was 10,367 BTU/kWh, which corresponds to 33% efficiency. These improvements in thermal efficiency due to increases in unit size and in steam temperature and pressure, as well as to the use of steam reheat, have resulted in savings in fuel costs and overall operating costs. There have been continuing increases, too, in transmission voltages. From Edisons 220-V three-wire dc grid to 4-kV single-phase and 2.3-kV three-phase
