【正文】 use are 10, 35, 110 for HV class, and 220, 330(only in Northwest China)and500 line will be built in the near future in Northwest the development of the AC/DC converting equipment, high voltage DC(HVDC)transmission systems have bee more attractive and economical in special HVDC transmission can be used for transmission of large blocks of power over long distance, and providing an asynchronous link between systems where AC interconnection would be impractical because of system stability consideration or because nominal frequencies of the systems are basic requirement to a power system is to provide an uninterrupted energy supply to customers with acceptable voltages and electricity can not be massively stored under a simple and economic way, the production and consumption of electricity must be done fault or misoperation in any stages of a power system may possibly result in interruption of electricity supply to the , a normal continuous operation of the power system to provide a reliable power supply to the customers is of paramount system stability may be broadly defined as the property of a power system that enables it to remain in a state of operating equilibrium under normal operating conditions and to regain an acceptable state of equilibrium after being subjected to a disturbance..Instability in a power system may be manifested in many different ways depending on the system configuration and operating , the stability problem has been one of maintaining synchronous power systems rely on synchronous machines for generation of electrical power, a necessary condition for satisfactory system operation is that all synchronous machines remain in synchronism or, colloquially “in step”.This aspect of stability is influenced by the dynamics of generator rotor angles and powerangle relationships, and then referred to “ rotor angle stability ”譯文：電力系統(tǒng)現(xiàn)代社會比以往任何時候更多地依賴于電力供應。如果世界各地電力供應中斷了,無法想象世界會變成什么樣。電力系統(tǒng)（或電力能源系統(tǒng)），提供電力到現(xiàn)代社會，已成為產(chǎn)業(yè)界不可缺少的組成部分。歷史上第一個完整的電力系統(tǒng)（包括發(fā)電機，電纜，熔斷器，計量，加載）由托馬斯愛迪生所建——紐約市珍珠街電站，始于1882年9月運作。這是一個直流系統(tǒng)組成蒸汽發(fā)動機驅動的直流發(fā)電機，送給59個客戶。他們的負載，其中包括白熾燈，通過地下電纜系統(tǒng)提供110V電壓。一個個類似的系統(tǒng)在世界各地大多數(shù)大城市運行了數(shù)年。隨著弗蘭克斯普拉格在1884年對馬達的發(fā)展，電機負載被添加到這些系統(tǒng)，從此開始發(fā)展成為世界上最大的產(chǎn)業(yè)之一。最初的直流系統(tǒng)被廣泛使用，盡管如此，他們幾乎完全被交流系統(tǒng)所取代。到1886年，直流系統(tǒng)的局限性也日益明顯。他們從發(fā)電機提供功率只有很短的距離。為了保持發(fā)射功率損失（I 2 R）和電壓下降到可接受的水平，長途輸電電壓必須高。如此高的電壓發(fā)電和電力消耗是可以接受的，因此，電壓轉換有一個方便的手段成為了必要。1889年，在北美波特蘭和威拉梅特大瀑布之間的俄勒岡州第一次實施交流傳輸線。這是一個單相線路傳輸為4,000伏，超過21公里距離的系統(tǒng)。隨著交流的發(fā)展多相系統(tǒng)由尼古拉特斯拉，成為更具吸引力的。在1888年，尼古拉特斯拉取得多項交流專利，包括電動機，發(fā)電機，變壓器和輸電系統(tǒng)。西屋公司購買了這些早期的發(fā)明專利，并形成了現(xiàn)在交流系統(tǒng)的基礎。19世紀90年代，有很大的爭議在于直流或交流電力行業(yè)是否應該統(tǒng)一。到了世紀之交時，下面的原因使交流系統(tǒng)贏過了直流系統(tǒng)：（1）交流系統(tǒng)電壓水平可以很容易地改變，從而提供了傳輸?shù)撵`活性，發(fā)電用不同的電壓和消費。（2）交流發(fā)電機比直流發(fā)電機簡單得多。（3）交流電機的馬達比直流簡單且便宜得多。首次三相交流電線1893年投產(chǎn)于北美南加州1根 2300V，12公里長的線路。在電力傳輸初期交流頻率并不規(guī)范。有許多不同頻率在使用：25，50，60，125，和133赫茲。這對互連的問題。最后北美的60赫茲標準獲得通過，雖然50赫茲在許多其他國家仍在使用。較長的距離越來越需要大量的電壓傳輸這激勵了他們逐步使用高壓。為了避免電壓增殖數(shù)值無限，業(yè)界標準了電壓水平。在美國，標準是115，138，161，和230千伏的高電壓（高壓）類，345，500和765千伏級的特高電壓（超高壓）。在中國，各級使用電壓為10，35，110級高壓，220，330（僅在西北）和500千伏超高壓類。第一個750 kVtransmission線將在不久的將來建在中國西北地區(qū)。隨著交流/直流轉換設備的發(fā)展，高壓直流（HVDC）傳輸系統(tǒng)已經(jīng)成為更具吸引力和經(jīng)濟性的特殊情況。高壓直流輸電可用于輸入大塊輸電和長距離輸電，并提供不同系統(tǒng)間的異步連接，因為在交流聯(lián)網(wǎng)系統(tǒng)間是不切實際的，因為穩(wěn)定考慮，或因為系統(tǒng)間不同的頻率?；疽蟮诫娫聪到y(tǒng)是提供一個客戶可接受的電壓和頻率不間斷的能源供應。由于電力無法用簡單和經(jīng)濟的方法大量儲存，電力的生產(chǎn)和消費必須同時進行。系統(tǒng)在任何階段的故障或誤操作可能導致給客戶的電力供應中斷。因此，一個正常的電力系統(tǒng)能連續(xù)運行提供可靠的電力供應給客戶是至關重要的。電力系統(tǒng)穩(wěn)定，可廣泛定義為干擾財產(chǎn)的權力系統(tǒng)，可繼續(xù)經(jīng)營的狀態(tài)下正常運行的平衡條件和后向遭受恢復一個可以接受的平衡狀態(tài)。在電力系統(tǒng)的不穩(wěn)定可能會表現(xiàn)在經(jīng)營方式和多種不同的方式上，這取決于系統(tǒng)配置。傳統(tǒng)上，穩(wěn)定性問題一直是一個保持同步運行最主要的問題。由于電力系統(tǒng)的發(fā)電電力，一個令人滿意的系統(tǒng)運行的必要條件是，依靠同步電機都留在同步或通俗的“步驟”。這一方面是受穩(wěn)定的發(fā)電機轉子的動態(tài)角度和功角的關系，然后提到“轉子角穩(wěn)定”。第四篇：測繪專業(yè)英語論文外文翻譯The measurement of the surveying and mapping in mine Since the seventy s, as the electronic technology and laser technology development, the type of surveying and mapping instruments with electronics(such as range finder, electronic tachometer, gyroscopes)to the traditional surveying and mapping instruments methods produced profound satellite remote sensing, global positioning system, as a representative of the space on earth observation technology in surveying and mapping application in the science of mature, puter technology, system scientifically based geographic information system and application for the emergence of surveying and mapping information source of access, analyze, management, processing and application fully provide strong technical support, automation and intelligence of surveying and mapping system is already in investigation, therefore we can say, the modern mapping technology is undergoing a profound of measuring technology of an important application field, in the vast coal, metal mines, nonferrous mine production process played an important survey of modern task is: in mine exploration, design, development and production of the different stages of the operation of the ground and underground mining area, the space, resources,(in mineral and land resources and environment are mainly)information acquisition, storage, processing, display and use for reasonable and effective development resources, protecting the resources, protecting the environment, management, industrial and environmental services for the continuous development of the order to realize its modern task, mine measurement must be making full use of modern surveying and mapping instruments and techniques, put the advanced modern technology with mine surveying the actual work, specific characteristics, and the bination of broaden the living space mine survey and business scope, promote the reform and development of mine survey, adapt to the market economy system and mining system reform tachometer, space information technology, the inertial measurement system and other modern surveying and mapping instruments have been in mine survey technology is used to further development and are paper to modern surveying and mapping instruments of the development of the technology and its application in 、Electronic tachometer and its application in mine survey: Electronic tachometer as the most widely used surveying and mapping instruments, is electronic technology and optical technology development of th