基礎防雷外文資料翻譯

1、 畢業(yè)設計(論文)外文資料翻譯系 （院）：電子與電氣工程學院專 業(yè)：電氣工程及其自動化姓 名： 學 號： 外文出處： (用外文寫)baidu library附 件：1.外文資料翻譯譯文；2.外文原文。指導教師評語： 年月日簽名： （手寫簽名） 注：請將該封面與附件裝訂成冊。附件1：外文資料翻譯譯文基礎防雷簡介 閃電是一個反復無常，隨機和不可預測的事件。它的物理特征包括：電流超過400 ka；溫度超過50000華氏度，速度接近或超過三分之一的光速。自2000年以來持續(xù)雷擊地球約100次每秒。美國保險公司的資料顯示每57索賠有一次是因為雷擊損壞。這些數(shù)據(jù)還不包括商業(yè)，政府和工業(yè)雷電造成的損失。在美

2、國每年因雷電造成的火災超過26000起，財產(chǎn)損失在5-6億美元。 地球上的雷擊現(xiàn)象，按目前的技術角度來看，遵循一個近似的規(guī)律：1。從頂層雷云朝地球的向下脈沖，尋求電氣地面目標。2。地基對象（圍欄，樹木，草葉，建筑，避雷針，等等）對此事件發(fā)出不同程度的電力活動。從這些地基對象向上發(fā)送電力波動，在離地面幾十米的位置，會出現(xiàn)一個“聚集區(qū)”加劇當?shù)氐碾妶觥?。當帶有異種電荷的雷云相遇，相當于電路“開關”被關閉，于是有電流流過。我們就會看到閃電。閃電效果可以直接也可能是間接的。直接影響是有電阻發(fā)熱，出現(xiàn)電弧并可能燃燒起來。間接影響是，多數(shù)時候?qū)﹄娙荩姼谐霈F(xiàn)電磁影響。在絕對意義上實現(xiàn)閃電的防護是不可能的

3、，只能使其產(chǎn)生的影響減少，可以由一個整體性，系統(tǒng)性的風險緩解辦法來實現(xiàn)保護。下面對通用條款進行描述。避雷針 從富蘭克林研究雷電開始，就使用避雷針進行建筑物防雷并引流接地。避雷針，是現(xiàn)在最常用的防雷裝置，根據(jù)建筑物不同的地點，高度和形狀，使用合適類型的避雷針來達到設計要求。一些公共事業(yè)如架空線、變電所喜歡屏蔽電線。在某些情況下，沒有任何避雷裝置的使用是最適當?shù)摹?高空避雷裝置的使用可能會改變閃電的動作。在等效電力場所，鈍尖桿被看作是一種有效的避雷針類型。高空防雷裝置的設計和性能是一個有爭議的并尚未解決的問題。因為“消除”閃電是一個值得懷疑的辦法。進一步的研究和試驗仍在進行中，以便更充分地了解各種

4、高空防雷裝置的可行性。引下線連接 引下線應通過一個安全的方式安裝，在已知電路外面敷設。引下線不可以涂漆，因為這樣會增加阻抗。漸進彎曲半徑最小為八英寸，應采取避免閃絡的方式。建筑鋼材可用于與大地連接的引下線，要保證所有的金屬建材有效的連接成網(wǎng)。所有金屬導體應進入連接，如燃氣及水管道，信號線，空調(diào)管道，鐵路軌道，橋式起重機等應被接地系統(tǒng)。各金屬導體的連接應該是熱連接，而不應是機械連接。機械連接時容易受到腐蝕和物理傷害。接地 接地系統(tǒng)必須面對地球的低阻抗和阻力。一個閃電的脈沖光譜研究揭示閃電既有高頻率也有低頻率的內(nèi)容。高頻率性能是頻譜變化速度非常迅速的，達到10微秒的峰值電流。低頻率分量延續(xù)時間長，

5、是一種高能量后續(xù)的沖擊電流。接地系統(tǒng)是將雷電脈沖傳入大地來減少危害的。 單點接地系統(tǒng)是將所有內(nèi)部設備連接到一根主母線在連接到外部接地系統(tǒng)。接地系統(tǒng)的設計應以減少交流阻抗和直流電阻為前提。地球的零電位是防雷接地最重要的原因。采用徑向技術可以降低阻抗，能讓雷電能量發(fā)散，因為每個接地導體的都有一個電壓梯度，他們應該被連接到地面設施。瞬變和浪涌 普通熔斷器和斷路器并沒有與閃電感應瞬變的能力。避雷設備可以是電流分散，濾波器的特定頻率，鉗位組合等都是可以實現(xiàn)這個功能的組合。電壓鉗位器件可以處理極高峰值的浪涌，以及具有減少極快的上升沿瞬態(tài)的能力。采用壁壘防御是一種需要謹慎的行為：其可以保護主面板，保護所有相

6、關二次配電盤，保護一切有價值的插件設備，如過程控制儀表，計算機，打印機，火災報警，數(shù)據(jù)記錄和scada系統(tǒng)設備等。此外，還可以保護傳入和傳出的數(shù)據(jù)和信號線。保護那些服務的主要資產(chǎn)，如井口，遠程安全報警，閉路電視攝像頭，高桅桿照明，空調(diào)通風等穿透一個結(jié)構(gòu)從另一個不應被忽略的需要防雷的設施中工作的設備。 安裝電涌抑制器的最小的引線長度取決于各自的電氣面板。快速上升時間條件下，電纜電感成為重要的高瞬態(tài)電壓可以使用較長的引線。檢測閃電探測儀，在不同的成本和技術條件下，有時是可以起到雷電早期預警的作用的。一個最普通的應用是，被用來作為ac線路電源斷開到雷電到來之前的備用電源。用戶應提防過度依靠設備，因為

7、這不是每次都可用的。教育所有人都應該接受防雷安全教育。在出現(xiàn)雷暴的時候，在室內(nèi)或汽車里的時候，應避免接觸水和其他一些的金屬物件;避免在一些制高點行車，不要在孤立的樹木下面躲雨;不要在下雨的時候在室外打電話。如果在戶外時附近有閃電擊中，應該躲到安全的位置，丟掉手中的金屬物體，雙腳蜷縮在一起，低著頭，雙手捂在耳朵上，以避免雷聲震壞耳膜。 綜述需要申明的重要的一點，上述所有的內(nèi)容都是通過安全防雷的角度分析的。沒有絕對理想的防雷措施。因為閃電可能超出每一個人的想象。系統(tǒng)化的防雷措施是一種有效減少雷電危害的方法。參考文獻1。 2003年空氣污染指數(shù)，對所產(chǎn)生的靜電，火災2008閃電和雜散電流，美國石油研

8、究所，華盛頓特區(qū)，1991年12月。2。 golde，g.h.，閃電，學術出版社，紐約，1977。3。哈瑟，體育，低電壓系統(tǒng)，彼得peregrinus出版社，倫敦，1992年過電壓保護。4。 hovath，蒂博爾，防雷，威利計算，紐約，1991年。5。 ieee標準1100，供電和敏感的電子設備的接地，符合ieee，紐約州。 1992。6?？夏岬虾教熘行?，用于連接和接地，工程開發(fā)局，約翰肯尼迪航天中心，美國航天局，1991年標準。7。莫里斯，i，et.al.，火箭引雷研究的重要資產(chǎn)，在行業(yè)的應用，卷匯刊保護。 30，第3號，5 / 1994年6月。8。森德，e.d.輸電系統(tǒng)接地傳導效應，四凡諾

9、斯特蘭有限公司，紐約，1949年。9。湯，四，波動現(xiàn)象，多佛出版社，臺北。10。烏曼，馬丁，閃電，多佛出版社，紐約，1984。11。 viemeister，彼得，閃電書，麻省理工學院出版社，劍橋大學碩士，1972年附件2： fundamentals of lightning protectionintroductionlightning is a capricious, random and unpredictable event. its' physical characteristics include current levels sometimes in excess of 4

10、00 ka, temperatures to 50,000 degrees f., and speeds approaching one third the speed of light. globally, some 2000 on-going thunderstorms cause about 100 lightning strikes to earth each second. usa insurance company information shows one homeowner's damage claim for every 57 lightning strikes. d

11、ata about commercial, government, and industrial lightning-caused losses is not available. annually in the usa lightning causes more than 26,000 fires with damage to property (nlsi estimates) in excess of $5-6 billion.the phenomenology of lightning strikes to earth, as presently understood, follows

12、an approximate behavior:1. the downward leaders from a thundercloud pulse towards earth seeking out active electrical ground targets.2. ground-based objects (fences, trees, blades of grass, corners of buildings, people, lightning rods, etc., etc.) emit varying degrees of electric activity during thi

13、s event. upward streamers are launched from some of these objects. a few tens of meters off the ground, a "collection zone" is established according to the intensified local electrical field.3. some leader(s) likely will connect with some streamer(s). then, the "switch" is closed

14、 and the current flows. we see lightning.lightning effects can be direct and/or indirect. direct effects are from resistive (ohmic) heating, arcing and burning. indirect effects are more probable. they include capacitive, inductive and magnetic behavior. lightning "prevention" or "pro

15、tection" (in an absolute sense) is impossible. a diminution of its consequences, together with incremental safety improvements, can be obtained by the use of a holistic or systematic hazard mitigation approach, described below in generic terms.lightning rodsin franklin's day, lightning rods

16、 conducted current away from buildings to earth. lightning rods, now known as air terminals, are believed to send streamers upward at varying distances and times according to shape, height and other factors. different designs of air terminals may be employed according to different protection require

17、ments. for example, the utility industry prefers overhead shielding wires for electrical substations. in some cases, no use whatsoever of air terminals is appropriate (example: munitions bunkers). air terminals do not provide for safety to modern electronics within structures.air terminal design may

18、 alter streamer behavior. in equivalent e-fields, a blunt pointed rod is seen to behave differently than a sharp pointed rod. faraday cage and overhead shield designs produce yet other effects. air terminal design and performance is a controversial and unresolved issue. commercial claims of the &quo

19、t;elimination" of lightning deserve a skeptical reception. further research and testing is on-going in order to understand more fully the behavior of various air terminals.downconductors, bonding and shieldingdownconductors should be installed in a safe manner through a known route, outside of

20、the structure. they should not be painted, since this will increase impedance. gradual bends (min. eight inch radius) should be adopted to avoid flashover problems. building steel may be used in place of downconductors where practical as a beneficial part of the earth electrode subsystem.bonding ass

21、ures that all metal masses are at the same electrical potential. all metallic conductors entering structures (ac power, gas and water pipes, signal lines, hvac ducting, conduits, railroad tracks, overhead bridge cranes, etc.) should be integrated electrically to the earth electrode subsystem. connec

22、tor bonding should be thermal, not mechanical. mechanical bonds are subject to corrosion and physical damage. frequent inspection and ohmic resistance measuring of compression and mechanical connectors is recommended.shielding is an additional line of defense against induced effects. it prevents the

23、 higher frequency electromagnetic noise from interfering with the desired signal. it is accomplished by isolation of the signal wires from the source of noise.groundingthe grounding system must address low earth impedance as well as low resistance. a spectral study of lightning's typical impulse

24、 reveals both a high and a low frequency content. the high frequency is associated with an extremely fast rising "front" on the order of 10 microseconds to peak current. the lower frequency component resides in the long, high energy "tail" or follow-on current in the impulse. the

25、 grounding system appears to the lightning impulse as a transmission line where wave propagation theory applies.a single point grounding system is achieved when all equipment within the structure(s) are connected to a master bus bar which in turn is bonded to the external grounding system at one poi

26、nt only. earth loops and differential rise times must be avoided. the grounding system should be designed to reduce ac impedance and dc resistance. the shape and dimension of the earth termination system is more important a specific value of the earth electrode. the use of counterpoise or "crow

27、's foot" radial techniques can lower impedance as they allow lightning energy to diverge as each buried conductor shares voltage gradients. ground rings around structures are useful. they should be connected to the facility ground. exothermic (welded) connectors are recommended in all circu

28、mstances.cathodic reactance should be considered during the site analysis phase. man-made earth additives and backfills are useful in difficult soils circumstances: they should be considered on a case-by-case basis where lowering grounding impedances are difficult an/or expensive by traditional mean

29、s. regular physical inspections and testing should be a part of an established preventive maintenance program.transients and surgesordinary fuses and circuit breakers are not capable of dealing with lightning-induced transients. lightning protection equipment may shunt current, block energy from tra

30、veling down the wire, filter certain frequencies, clamp voltage levels, or perform a combination of these tasks. voltage clamping devices capable of handling extremely high amperages of the surge, as well as reducing the extremely fast rising edge (dv/dt and di/dt) of the transient are recommended.

31、adopting a fortress defense against surges is prudent: protect the main panel (ac power) entry; protect all relevant secondary distribution panels; protect all valuable plug-in devices such as process control instrumentation, computers, printers, fire alarms, data recording & scada equipment, et

32、c. further, protect incoming and outgoing data and signal lines. protect electric devices which serve the primary asset such as well heads, remote security alarms, cctv cameras, high mast lighting, etc. hvac vents which penetrate one structure from another should not be ignored as possible troubleso

33、me electrical pathways.surge suppressors should be installed with minimum lead lengths to their respective panels. under fast rise time conditions, cable inductance becomes important and high transient voltages can be developed across long leads.in all instances, use high quality, high speed, self-d

34、iagnosing protective components. transient limiting devices may use a combination of arc gap diverters-metal oxide varistor-silicon avalanche diode technologies. hybrid devices, using a combination of these technologies, are preferred. know your clamping voltage requirements. confirm that your vendo

35、r's products have been tested to rigid ansi/ieee/iso9000 test standards. avoid low-priced, bargain products which proliferate the market (caveat emptor).detectionlightning detectors, available at differing costs and technologies, sometimes are useful to provide early warning. an interesting appl

36、ication is when they are used to disconnect from ac line power and to engage standby power, before the arrival of lightning. users should beware of over-confidence in such equipment which is not perfect and does not always acquire all lightning data.educationlightning safety should be practiced by a

37、ll people during thunderstorms. preparedness includes: get indoors or in a car; avoid water and all metal objects; get off the high ground; avoid solitary trees; stay off the telephone. if caught outdoors during nearby lightning, adopt the lightning safety position (lsp). lsp means staying away from

38、 other people, taking off all metal objects, crouching with feet together, head bowed, and placing hands on ears to reduce acoustic shock.measuring lightning's distance is easy. use the "flash/bang" (f/b) technique. for every count of five from the time of seeing the lightning stroke t

39、o hearing the associated thunder, lightning is one mile away. a f/b of 10 = 2 miles; a f/b of 20 = 4 miles, etc. since the distance from strike a to strike b to strike c can be as much as 5-8 miles. be conservative and suspend activities when you first hear thunder, if possible. do not resume outdoo

40、r activities until 20 minutes has past from the last observable thunder or lightning.organizations should adopt a lightning safety policy and integrate it into their overall safety plan.testingmodern diagnostic testing is available to mimic the performance of lightning conducting devices as well as

41、to indicate the general route of lightning through structures. this testing typically is low power, 50 watt or less. it is traceable, but will not trip movs, gas tube arrestors, or other transient protection devices. knowing the behavior of an event prior to occurrence is every businessman's ear

42、nest hope. with such techniques, lightning paths can be forecast reliably.codes & standardsthe marketplace abounds with exaggerated claims of product perfection. frequently referenced codes and installation standards are incomplete, out dated and promulgated by commercial interests. on the other hand iec, ieee, mil-std, faa, nasa and sim