電力系統(tǒng)的演化外文翻譯

中文 2188 字 EVOLUTION OF ELECTRIC POWER SYSTEMS The commercial use of electricity began in the late1870s when arc lamps were used for lighthouse illumination and street lighting. The first complete electric power system (comprising a generator, cable, fuse, meter, and loads)was built by Thomas Edison-the historic Pearl Street Station in New York City which began operation in September 1882.This was a dc system consisting of a steam-engine-driven dc generator supplying power to 59 customers within an area roughly 1.5km in radios. The load, which consisted entirely of incandescent lamps, was supplied at 110 V through an underground cable system. Within a few years similar systems were in operation in most large cities throughout the world. With the development of motors by Frank Sprague in 1884, motor loads were added to such systems. This was the beginning of what would develop into one of the largest industries in the world. In spite of the initial widespread use of dc systems, they were almost completely superseded by ac systems. By 1886, the limitations of dc systems were becoming increasingly apparent .They could deliver power only a short distance from the generators. To keep transmission power losers (RI2) and voltage drops to acceptable levels, voltage levels had to be high for long-distance power transmission. Such high voltages were not acceptable for generation and consumption of power; therefore, a convenient means for voltage transformation became a necessity. The development of the transformation and ac transmission by L. Gaulard and J.D. Gibbs of Paris, France, led to ac electric power systems. George Westinghouse secured rights to these developments in the United States. In 1886, William Stanley, an associate of Westinghouse, developed and tested a commercially practical transformer and ac distribution system for 150 lamps at Great Barrington, Massachusetts. In 1889, the first ac transmission line in North America was put into operation in Oregon between Willamette Falls and Portland. It was a single-phase line transmitting power at 4,000 V over a distance of 21 km. With the development of polyphase systems by Nikolas Tesla, the ac system became even more attractive. By 1888, Tesla held several patents on ac motors, generators, transformers, and transmission systems. Westinghouse bought the patents to these early inventions, and they formed the basis of the present-day ac systems. In the 1890s, there was considerable controversy over whether the electric utility industry should be standardized on dc or ac. There were passionate arguments between Edison, who advocated dc, and Westinghouse, who favored ac. By the turn of the century, the ac system had won out over the dc system for the following reasons; Voltage levels can be easily transformed in ac systems, thus providing the flexibility for use of different voltages for generation, transmission, and consumption. AC generators are much simpler than dc generators. AC motors are much simpler and cheaper than dc motors. The first three-phase line in North America went into operation in 1893-a 2,300 V, 12 km line in southern California. Around this time, ac was chosen at Niagara Falls because dc was not practical for transmitting power to Buffalo, about 30 km away. This decision ended the ac versus dc controversy and established victory for the ac system. In the early period of ac power transmission, frequency was not standardized. Many different frequencies were in use: 25, 50, 60, 125, and 133 Hz. This posed a problem for interconnection. Eventually 60 Hz was adopted as standard in North America, although many other countries use 50 Hz. The increasing need for transmitting larger amounts of power over longer distances created an incentive to use progressively higher voltage levels. The early ac systems used 12,44, and 60 kV(RMS line-to-line).This rose to 165 kV in 1922,220 kV in 1923,287 kV in 1935,330 kV in 1953,and 765 kV was introduced in the United States in 1969. To avoid the proliferation of an unlimited number of voltages, the industry has standardized voltage levels. The standards are 115, 138, 161, and 230 kV for the high voltage (HV) class, and 345, 500 and 765 kV for the extra-high voltage (EHV) class. With the development of mercury arc valves in the early 1950s, high voltage dc (HVDC) transmission systems became economical in special situations. The HVDC transmission is attractive for transmission of large blocks of power over long distances. The cross-over point beyond which dc transmission may become a competitive to ac transmission is around 500 kV for around 500 km for overhead lines and 50 km for underground or submarine cables. HDVC transmission also provides an asynchronous link between systems where ac interconnection would be impractical because of system stability considerations or because nominal frequencies of the systems are different. The first modern commercial application of HVDC transmission occurred in 1954 when the Swedish mainland and the island of Gotland were interconnected by a 96 km submarine cable. With the advent of thyristor valve converters, HVDC transmission became even more attractive. The first application of an HVDC system using thyristor values was at Eel River in 1972-a back-to-back scheme providing an asynchronous tie between the power systems of Quebec and New Brunswick. With the cost and size of conversion equipment decreasing and its reliability increasing, there has been a steady increase in the use of HVDC transmission. Interconnection of neighboring utilities usually leads to improved security results from the mutual emergency assistance that the utilities can provide. Improved economy results from the need for less generating reserve capacity in each system. In addition, the interconnection permits the utilities to make economy transfers and thus take advantage of the most economical sources of power. These benefits have been recognized from the beginning and interconnections continue to grow. Almost all the utilities in the United States and Canada are now part of one interconnected system of enormous complexity. The design of such a system and its secure operation are indeed challenging problems. STRUCTURE OF THE POWER SYSTEM Electric power system varies in size and structural components. However, they all have the same basic characteristics: Are comprised of three-phase ac systems operating essentially at constant voltage. Generation and transmission facilities use three-phase equipment. Industrial loads are invariably three-phase; single-phase residential and commercial loads are distributed equally among the phases so as to effectively form a balanced three-phase system. Use synchronous machines for electricity. Prime movers convent the primary sources of energy (fossil, nuclear, and hydraulic) to mechanical energy that is, in turn, converted to electrical energy by synchronous generators. Transmit power over significant distances to consumers spread over a wide area. This requires a transmission system comprising subsystems operating at different voltage levels. Electric power is produced at generating stations (GS) and transmitted to consumers through a complex network of individual components, including transmission lines, transformers, and switching devices. It is common practice to classify the transmission network into the following subsystems: 1. Transmission system 2. Subtransmission system 3. Distribution system The transmission system interconnects all major generating stations and main load canters in the system. It forms the backbone of the integrated power system and operates at the highest voltage levels (typically, 230kV and above).The generator voltage are usually in the range of 11 to 35 kV. These are stepped up to the transmission voltage levels, and power is transmitted to transmission substations where the voltage are stepped down to the subtransmission level (typically, 69 kV to 138 kV).The generation and transmission subsystems are often referred to as the bulk power system. The subtransmission system transmits power in smaller quantities from the transmission substations to the distribution substations. Large industrial customers are commonly supplied directly from the substransmission system. In some systems, there is no clear demarcation between substransmission and transmission circuits. As the system expands and higher voltage levels become necessary for transmission, the older transmission lines are often relegated to subtransmission function. The distribution system represents the final stage in the transfer of power to the individual customers. The primary distribution voltage is typically between 4.0 kV and 34.5 kV. Small industrial customers are supplied by primary feeders at this voltage level. The secondary distribution feeders are supply residential and commercial customers at 120/240V. 翻譯： 電力系統(tǒng)的演化 商業(yè)用電始于 19 世紀 70 年代后期，弧燈用于燈塔照明和街道照明。 第一個完整的電力系統(tǒng)（由發(fā)電機、電纜、熔絲、電表和負荷組成）是由 Thomas Edison在紐約城的 Pearl Street Station 建成并與 1882 年 9 月投入運行，這是一個由蒸汽發(fā)動機驅動供 給 1.5 公里內(nèi) 59 個用戶組成的直流輸電系統(tǒng)。負荷是包括白熾燈在內(nèi)的 110V 供電的電纜系統(tǒng)。幾年之內(nèi)類似系統(tǒng)在運行在全世界大多數(shù)大城市中。隨著 1884 年弗蘭克電機的發(fā)展 ,電機負載計入電力系統(tǒng)系統(tǒng)。這是電力發(fā)展 為世界最大產(chǎn)業(yè)之一的開始。 盡管最初廣泛使用直流系統(tǒng)，（但后來）幾乎完全交流系統(tǒng)所取代。到 1886 年，直流系統(tǒng)的局限性日益突現(xiàn)，只能在很短的距離內(nèi)從發(fā)電機向外送電。為了保持功率損耗和電壓降落在可接受水平，需提高電壓水平以保證遠距離輸電。發(fā)電機和用電設備不能承受較高電壓電能，因此，方便轉換電壓成為一種必要。 由于 L.Gaulard 和法國巴黎的 J.D.Gibbs 開發(fā)了變壓器和交流輸電技術，由此產(chǎn)生了交流電力系統(tǒng)。 George Westinghouse 獲得了這些新權利在美國應用的權利。在 1886 年，西屋的助手 William Stanley 開發(fā)和試驗了商業(yè)實用的變壓器和在 Great Brrington， Massachusetts 的由150個電燈組成的交流配電系統(tǒng)。在 1889年 ,第一個交流輸電線路在北美 Oregon 的 Willamette Falls 和 Portland 之間投運。這是一個單相線傳輸電能為 4000 V 輸送距離超過 21 公里的電力系統(tǒng)。 隨著 Nikolas Tesla 多相系統(tǒng)的建立和發(fā)展，交流系統(tǒng)變得更加有吸引力。到 1888 年， Tesla持有關于交流電動機、發(fā)電機、變壓器和輸電系統(tǒng)的若干專利。 Westinghouse 購買了這些早期發(fā)明專利，這些發(fā)明奠定了當今交流電力系統(tǒng)的基礎。 在 19 世紀 90 年代 ,關于電力工業(yè)應采用直流還是交流作為標準的相當大的爭論。在主張直流的 Edison 和偏好交流的 Westinghouse 之間發(fā)生過激烈的辯論。到世紀末 ,交流系統(tǒng)戰(zhàn)勝了直流系統(tǒng) ,原因如下： 在交流系統(tǒng)中容易變壓，因此可以靈活地使用不同電壓等級的發(fā)電機，變壓器和用電設備。 交流發(fā)電機比直流發(fā)電機簡單得多。 交流電動機比直流發(fā)電機更簡單，更便宜。 第一個三相 12 公里 2300V 輸電線路在于 1893 年在北美 California 南部投運。在那個時候，因為直流不能實際傳輸電能到 30 公里外的 Buffalo，所以 Niagara Falls 選擇了直流供電。這個決定結束了交流和直流爭議 ,奠定了交流系統(tǒng)成功的基礎。 在早期的交流輸電中頻率不統(tǒng)一。 使用許多不同平頻率為： 25、 50、 60 、 125 和 133赫茲。這是互聯(lián)的一個問題。北美最終采用 60HZ 為標準，盡管其他地區(qū)和國家采用 50HZ。 由于大量長距離輸電的增長需要，創(chuàng)造 和激勵了電壓水平的逐漸提高。 早期的交流系統(tǒng)使用 12、 44 和 60kV（ RMS line-to-line）。電壓等級在 1922 年上升到 165kV， 1923 年上升到287kV， 1953 年上升到 330kV， 1969 年美國引進了 765kV 的高壓。 為了避免電壓等級的無限增加，電力行業(yè)將電壓等級標準化。這些高壓類（ HV）的標準電壓等級是： 115、 138、 161 和 230 kV，特高壓（ EHV）有 345、 500 和 765kV 幾個電壓等級 。 隨著 20 世紀 50 年代初汞弧閥發(fā)展，高電壓直流傳輸系統(tǒng)變得經(jīng)濟。為此，高壓直流輸電在大面積、長距離方面很具有吸引力。在 500kV500