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 Pearl 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. 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. 1878年,爱迪生开始研究电灯,提出由位于中央的电站向四周地区提供照明的想法。1879年10月,他进一步改进了他的电灯的设计,纽约Peral街电站的运行标志着电力工业的开始。在Pearl街,由蒸汽机驱动直流发电机(被称做)向1平方里范围内的59个用户的110V的白炽灯供电,供电负荷最初为30kW。从1882年至1972年,电力工业成长速度惊人,主要原因是由于科技上不断取得的成就和工程界创造性的成果,电能价格持续下降。 The introduction of the practical dc motor by Sprague electric, as well as the growth of incandescent lighting, promoted the expansion of Edison’s 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 maximum distance and load were overcome in 1885 by William Stanley’s 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 corresponding 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. 由Sprague电力引进的实用的直流电机及白炽灯的发展推动了爱迪生的直流系统的发展。3线220V直流系统的发明在一定程度上提高了供电负荷,但是当输电距离和负荷继续增加,电压成为一大问题。1885年William Stanley发明的经济可行的变压器解决了这一在输电距离和负荷上的限制问题。Stanley在Massachusetts的Great Barrington建立了一个交流配电系统,为150盏灯供电。变压器使得电能可以在更高电压和更低电流传输,降低了线路电压降,使交流系统比直流系统跟具吸引力。美国第一条单相交流线路1889年在Oregon运行,该线路21公里,电压等级为4kV,连接Oregon和Portland. The growth of ac systems was further encouraged in 1888 when Nikola Tesla presented a paper 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. 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. 1888年Nikola Tesla在美国电气工程师协会的会议上,提交了一篇讲解两相感应和同步电机的论文,使得多相系统相对单相系统的优势更加明显了,这更加推进了交流系统的发展。1891年,第一条三相线路在德国运行,传输距离179km,电压等级12kv。在1893年美国(加利福尼亚)的第一条三相线路开始运行,传输距离12km,电压等级2.3kv。Tesla所设想的三相感应电动机逐渐成为工业的主力. In the same year that Edison’s steam-driven generators were inaugurated, 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 account for about 7%. Gas turbines are used in some cases to meet peak loads. 同年,爱迪生的蒸汽驱动发电机落成,一台由水轮驱动的发电机安装在Wisconsin的Appleton。自那以后,大部分的电能都由蒸汽驱动和水驱动(称为水电)的电厂产生。今天,汽轮机占据了美国电力发电的85%以上,而水轮机大约占7%。燃气轮机用在某些情况下,以满足峰荷的需要。 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 converted 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 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. 蒸汽电厂的主要燃料是煤,天然气,石油和铀。其中,由于储量丰富,煤是在美国使用最广泛的燃料。虽然,在20世纪70年代早期很多以煤为燃料的电厂都转化为以石油为燃料,然而由于1973年至1974年石油禁运而导致的石油短缺,这一趋势又被反转以燃煤为主,以减少对外国石油的依赖。1957年,相当于90MW汽轮机装机容量,以铀为燃料的核电机组投建,如今,具有1312MW汽轮机装机容量的核电机组在使用中。但是,由于建设费用的增加,申请许可的拖延和公众的舆论阻碍了美国核电容量的增长。 Starting in the 1990s, the choice of fuel for new power plants in the United States 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. Expansion. However, increasing natural gas prices may slow this trend. 自从20世纪90年代以来,美国新建电厂的燃料一直是天然气。燃气轮机安全,干净,一致认为比其他技术更有效率。截至2001年,天然气的发展趋势一直在加快。据估计,200个大型燃气电厂正在发展中,占据了美国电源规划的75%-90%。然而,天然气价格的提高可能会减慢燃气电厂的发展。 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 earth’s upper crust; solar cell arrays; and tidal power plants. These sources of energy cannot be ignored, but they are not expected to supply a large percentage of the world’s 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 producing 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. 其他类型的电力发电也在使用中,包括风力涡轮发电机;从地壳获得蒸汽或热水形式能源的地热发电厂,太阳电池阵列和潮汐发电厂。这些能源不容忽视,但预计它们不能满足世界未来的大部分能源需求。相反,核聚变能源却能够满足这一需求。大量的研究已经表明,因核聚变能源生产安全,无污染并且节约(经济)电力能源,其将是21世纪后期及以后一项大有可为的技术。核聚变反应消耗的氚,海水是其几乎取之不尽的补给。 The early ac systems operated at various frequencies including 25, 50, 60, 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 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 frequencies 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, motors, 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. 最早的交流系统以25Hz, 50Hz, 60Hz 和 133Hz各种频率运行。1891年60Hz成为美国的标准频率。1893年,通过采用同步换流器,开始使用25Hz系统。但是,这些系统主要用于铁路电气化(很多现在已经退役),因为它们有造成白炽灯闪烁的缺点。加利福尼亚的水利电力部采用50Hz,但是,当1937年Hoover大坝开始运作,频率就转换为60Hz。1949年南加利福尼亚的Edison公司也将频率从50Hz转变为60Hz。今天,60Hz(在美国,加拿大,日本和巴西使用)和50Hz(在欧洲,前苏联,除巴西以外的南美洲,印度以及日本使用)是世界上发电,输电和配电的两个标准频率。60Hz系统的优点在于系统中的发电机,电动机和变压器通常比同等级50Hz系统的设备小。50Hz系统的优点是传输线和变压器的电抗在50Hz时较60Hz时小。 As shown in Figure 1.2, the rate of growth of electric energy in the United States was approximately 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 industry 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. 如图1.2所示,从1902年到1972年美国电力能源以每年大约7%的速度增长。这相当于在70年中每10年电能消耗就增加了一倍。换而言之,每10年电力工业新增的容量等于初始时所建容量的总和。1973/1974的石油禁运之后,每年的增长率就比较缓慢了。1972到1980年美国的千瓦时消耗每年增长3.4%,而1980至2000年每年增长2.1%。 Along with increases in load growth, there have been continuing in creases in the size of generating 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 generation 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. 随着负荷的增长,发电机组的规模也在不断的增加。投建较大机组的主要目的就是规模效应,即减少了每千瓦容量的安装成本。不过,发电效率也在稳步的提高。例如,1934年美国电力工业蒸汽发电的平均耗热率是17,950BTU/kWh,相当于19%的效率。到1991年,平均耗热率是10,367 BTU/kWh,效率为33%。由于机组规模和蒸汽温度、压力的改进,还有蒸汽再加热的使用,使得热效率得到提高,节约了燃料费用和总的运行费用。 There have been continuing increases, too, in transmission voltages. From Edison’s 220-V three-wire dc grid to 4-kV single-phase and 2.3-kV three-phase transmission, ac transmission voltages in the United States have risen progressively to 150, 230, 345, 500, and now 765 kV. And ultra-high voltages (UHV) above 1000 kV are now being studied. The incentives for increasing transmission voltages have been: (1) increases in transmission distance and transmission capacity, (2) smaller line-voltage drops, (3) reduced line losses, (4) reduced right-of-way requirements per MW transfer, and (5) lower capital and operating costs of transmission. Today, one 765-kV three-phase line can transmit thousands of mega watts over hundreds of kilometers. 传输电压也在不断地提高。从爱迪生的220V三相直流电网到单相4kV和三相2.3kV输电,美国的交流输电电压已经逐步上升到150,230,345,500和现在的765kV。并且1000kV以上的超高压正在研究当中。提高传输电压的目的是为了:(1)提高传输距离和传输容量,(2)线电压下降较小,(3)降低线路损耗,(4)减小每MW输电用地费用,(5)减少输电的投资和运行费用。如今,一条三相765kV的线路能将数千兆瓦的功率输送至几百公里以外。
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