有關(guān)雷擊過電壓中英對照翻譯

1、<p><b>　　雷擊過電壓</b></p><p>　　雷電是由于那些因降雨而帶電的云層，以及通常存在于積云中的垂直氣流而引起的。在架空線上可能會由于直接和間接的雷擊而建立起的過電壓。在直接雷擊中，雷電電流的路徑是直接從云朵到設(shè)備(架空線)。通過架空線，雷電產(chǎn)生的電流可以越過絕緣子，然后順著線桿入地。架空線上產(chǎn)生的電壓或許會在此路徑上發(fā)生閃絡(luò)然后接地。</p>&

2、lt;p>　　在直接雷擊中，雷電產(chǎn)生的電流流經(jīng)一些附近的物體(例如樹)。架空線上出現(xiàn)電壓可做以下解釋：當(dāng)云朵飄到架空線上空時，它所帶的正電荷吸引到遠(yuǎn)處的負(fù)電荷，并將這些負(fù)電荷附在云層下的架空線。假設(shè)架空線沒有通電，那么線上的電壓就為零。假設(shè)云層在發(fā)生閃電的一刻放電，正電荷突然消失，留下負(fù)電荷沒有被釋放。那么架空線上的負(fù)電荷就會對地產(chǎn)生負(fù)電荷。</p><p>　　在發(fā)生閃絡(luò)時，閃電層立刻完成放電的。相反，產(chǎn)

3、生的電流在幾微秒內(nèi)從零值到最大值。并在幾百微秒內(nèi)全部釋放。</p><p>　　在許多情況下，可能產(chǎn)生的電壓通過閃絡(luò)接地而得以限制。增加絕緣子串的長度只能在閃絡(luò)發(fā)生前允許建立較高的電壓。大多數(shù)青年概況下可采用架設(shè)架空接地線的方法來防止直接雷擊。</p><p>　　接地線放置在電力導(dǎo)線上，使得每一次雷擊都要通過接地線而不是電力系統(tǒng)，雷擊產(chǎn)生的電流就會流到地。之后，電流的大部分都經(jīng)過塔腳地面

4、電阻入地，而少部分沿著傳輸線通過塔腳入地。塔架的電壓升高到一個值，該值是由電流和經(jīng)過的電阻確立的。</p><p>　　大致上，這個電壓出現(xiàn)在塔架和（沒有被擊穿）電力導(dǎo)線之間。如果該電壓低于所能一起閃絡(luò)的值，則不會引起任何麻煩。用兩條精心放置的接地線和減少塔腳接地電阻的方法，可改善這種保護(hù)方法。</p><p>　　從支撐于80～90英尺高的塔架上的傳輸線的雷擊報告中，可以表明上述線路保護(hù)

5、的簡單原理。但是從100英尺以上的鐵塔的不太理想的記錄表明，或許還必須考慮到其他因素，而對地絕緣水平較高的電壓線路就不太重要，這些線路可承受幾百千伏的電壓而不會發(fā)生閃絡(luò)。</p><p>　　Over voltage Due to Lightning </p><p>　　Over voltage on power systems are traceable to three bas

6、ic cause：Lightning， switching，and contact with circuits of higher voltage rating.The power system designer seeks to minimize the number of these occurrences，to limit the magnitude of the voltages produced，and to control

7、their effects on operating equipment.</p><p>　　Lightning results from the presence of clouds which have charged by the action of failing rain and vertical air currents，a condition commonly found in cumulus c

8、louds.Voltage may be set up on overhead lines due to direct strokes and due to indirect strokes.In a direct strke，the lightning current path is directly from the cloud to the subject equipment-anoverhead line.From the li

9、ne，the current path may be over the insulators and does the pole to ground.The voltage set up on the line may be that ne</p><p>　　On the occurrence of a stroke，lightning clouds do not discharge in zero time.

10、Instead，the stroke current rises from zero value to maximum value in a few microseconds and is completed in a few hundred microseconds.</p><p>　　Direct lightning strokes to lines are of concern on lines of a

11、ll voltage class，as the voltage that may be set up is in most instances limited by the flashover of the path to ground，increasing the length of insulator strings merely permits a higher voltage befoe flashover occurs.The

12、 most generally accepted method of protection against direct strokes is by use of the overhead ground wire.For simplification only one ground wire and one power conductor are shown.</p><p>　　The ground wire

13、is placed above power conductor at such a positon that practically all lightning-stroke paths will be to it instead of to the power conductor.Stroke current then follows to the ground，most of it passing through the tower

14、 footing ground resistance while a smaller part goes down the line and to ground through the adjacent tower footings.The tower rises in voltage due to the current though the resistance to a value whice is </p>&

15、lt;p>　　Approximately this voltage appears between the tower and the power conductor (which was not struck).If this voltage is less than that required to cause insulator flashover，no trouble results.Protection by this

16、method is improved by using two carefully placed ground wires and by making tower footing ground resistance of low value.</p><p>　　The lightning record of lines supported on towers 80 to 90 feet tall substan

17、tiates the simple theory of line protection just presented.The poorer record of lines on towers over 100ft in height indicates that other factors，perhaps the inductance of the path down the tower，should be considered.<

18、;/p><p>　　Indirect strokes produce relatively low volages on lines.They are of real concern on low-voltage lines supported on small insulators.They are of little importance on high-voltage lines whose insulator