電氣專業(yè)外文翻譯

1、精選優(yōu)質(zhì)文檔-傾情為你奉上精選優(yōu)質(zhì)文檔-傾情為你奉上專心-專注-專業(yè)專心-專注-專業(yè)精選優(yōu)質(zhì)文檔-傾情為你奉上專心-專注-專業(yè)外文資料翻譯Reliability of Lightning ResistantOverhead Distribution LinesLighting continues to be the major cause of outages on overhead power distribution lines. Through laboratory testing and field observations and measurements, the properti

2、es of a lightning stroke and its effects on electrical distribution system components are well-understood phenomena. This paper presents a compilation of 32 years of historical records for outage causes, duration, and locations for eight distribution feeders at the Oak Ridge National Laboratory (ORN

3、L) .Distribution type lightning arresters are placed at dead-end and angle structures at pole mounted wormer locations and at high points on the overhead line. Station class lightning arresters are used to protect underground cable runs, pad mounted switchgear and unit substation transformers. Resis

4、tance to earth of each pole ground is typically 15 ohms or less. At higher elevations in the system, resistance to earth is substantially greater than 15 ohms, especially during the dry summer months. At these high points, ground rods were riven and bonded to the pole grounding systems in the 1960s

5、in an attempt to decrease lightning outages. These attempts were only partially successful in lowering the outage rate. From a surge protection standpoint the variety of pole structures used (in-line, corner, angle, dead end, etc.) and the variety of insulators and hardware used does not allow each

6、13.8 kV overhead line to be categorized with a uniform impulse flashover rating (170 kV, etc.) or a numerical BIL voltage class (95 kV BIL; etc.). For simplicity purposes in the analysis, each overhead line was categorized with a nominal voltage construction class (15 kV, 34 kV, or 69 KV). Six of th

7、e eight overhead lines (feeders 1 through 6) were built with typical REA Standard horizontal wood cross arm construction utilizing single ANSI Class 55- 5 porcelain pin insulators (nominal 15 kV insulation). The shield angle of the overhead ground wire to the phase conductors is typically 45 degrees

8、. One overhead line (feeder 7) was built with transmission type wood pole construction because the line extended to a research facility which was to have generated electricalpower to feed back into the grid. Pole structure of this line are of durable wood cross a construction which utilize double AN

9、SI 52-3 porcelain suspension insulators to support the conductors (nominal 34 kV insulation). The shield angle of the overhead ground wire to the phase conductors for feeder 7 is typically 30 degrees. In 1969, an overhead line (feeder 8) was intentionally built with lightning resistant construction

10、in an attempt to reduce lightning caused outages. Pole structures of the line have phase over phase 24-inch long fiberglass suspension brackets with double ANSI 52-3 porcelain suspension insulators to support the conductors (nominal 69 kV insulation). The shield angle of the overhead ground wire to

11、the phase conductors for feeder 8 is typically 30 degrees. The failure data was compiled for each of the eight 13.8 kV feeders and is presented in Table, along with pertinent information regarding feeder construction, elevation, length, and age.A key finding of the failure analysis is that weather-r

12、elated events account for over half (56%) of the feeder outages recorded. Fifty-seven of the 76 weather-related outages were attributed to lightning. Insulation breakdown damage due to lightning is also suspected in at least a dozen of the equipment failures observed. The data indicates overhead lin

13、es which pass over high terrain are less reliable because of the greater exposure to lightning. For example, feeder 3 had the most recorded outages (48), of which two-thirds were due to weather-related events; this feeder is also the highest line on the plant site, rising to an elevation of 450 abov

14、e the reference valley elevation. Overhead lines that are longer and to which more substations and equipment are attached were also observed to be less reliable (more exposure to lightning and more equipment to fail). The age of the line does not appear to significantly lessen its reliability as lon

15、g as adequate maintenance is performed; none of the lines have had a notable increase in the frequency of outages as the lines have aged. As would be expected, the empirical data presented in Table I confirms the two overhead lines which have been insulated to a higher level (34 or 69 KV) have signi

16、ficantly better reliability records than those utilizing 15 kV class construction. Feeder 7 (insulated to 34 KV) and feeder 8 (insulated to 69 kV) have bad only 3 outages each over their 32 and 23 year life spans, respectively. These lines follow similar terrain and are comparable in length and age

17、to the 15 kV class lines, yet theyhave a combined failure rate of 0.22 failures per year versus 4.32 failures per year for the remaining feeders.On typical 15 kV insulated line construction, lightning flashovers often cause 60 cycle power follow and feeder trip. With the higher insulation constructi

18、on, outage rates are reduced by limiting the number of flashovers and the resultant power follow which causes an over current device to trip. This allows lightning arresters to perform their duty of dissipating lightning energy to earth. The number of re closer actions and their resultant momentary

19、outages are also reduced. This is beneficial for critical facilities and processes which cannot tolerate even momentary outages. An additional benefit is that outages due to animal contact are also reduced because of the greater distance from phase conductor to ground on pole structures. Distributio

20、n line equipment to increase line insulation values are off the shelf items and proven technology. New lightning resistant construction typical by utilizes horizontal line posts, fiberglass standoff brackets or any other method which world increase the insulation value. The replacement of standard p

21、in insulators with line post insulators of greater flashover value is an effective means to retrofit existing wood cross arm construction. The doubling and tripling of dead end and suspension insulators is also a means of increasing flashover values on existing angle and dead-end structures. Current

22、 fiberglass, polymer, and epoxy technologies provide an affordable means to increase line insulation.While the use of increased insulation levels to reduce lightning flashovers and the resultant outages on overhead distribution lines has been thoroughly tested and demonstrated in laboratory and expe

23、rimental tests 5, long term history field data has positively demonstrated that the use of lightning resistant construction can greatly reduce outages. Field use at ORNL has shown that in areas which are vulnerable to lightning, the use of increased insulation and a smaller shielding angle is an imp

24、ressive and cost effective means to appreciably increase the reliability of overhead distribution lines. This reliability study clearly illustrates that the insulation requirements for high-reliability distribution feeders should be determined not by the 60 Hz operating voltage but rather by withsta

25、nd requirements for the lightning transients or other high voltage transients that are impressed upon the line. Electricalequipment (switchgear, insulators, transformers, cables, etc.) have a reserve (BE level or flashover value) to handle momentary over voltages, and by increasing that reserve, the

26、 service reliability is appreciably increased. As the electrical industry gradually moves away from standard wood cross arm construction and moves toward more fiberglass, polymer and epoxy construction, increased insulation methods can be applied as part of new construction or as part of an upgrade

27、or replacement effort. In considering new or upgraded overhead line construction, the incremental increased cost of the higher insulation equipment is d in proportion to the total costs of construction (labor, capital equipment, cables, electric poles, right-of-way acquisition), Its cost effectivene

28、ss varies with the application and the conditions to which it is be applied. Economic benefits include increased electrical service reliability and its inherent ability to keep manufacturing processes and critical loads in service. Other more direct benefits include less repair of overhead distribut

29、ion lines, which can have a significant reduction in maintenance cost due to less replacement materials and a large reduction in overtime hours for maintenance crews.抗雷擊架空配電線路的可靠性閃電仍然是架空配電線路上的中斷 1 的主要原因。通過實(shí)驗(yàn)室測(cè)試和現(xiàn)場(chǎng) 觀察和測(cè)量，雷擊和其對(duì)配電系統(tǒng)組件的屬性是很好理解的現(xiàn)象。本文提出了 一個(gè) 32 年的歷史記錄，停運(yùn)的原因，時(shí)間，地點(diǎn)，在橡樹嶺國(guó)家實(shí)驗(yàn)室的八個(gè) 配電饋線匯編。配電型避雷器

30、在死胡同和角度的結(jié)構(gòu)被放置在極安裝 W 奧莫爾的位置，并 在高點(diǎn)上的架空線。站級(jí)避雷器是用來(lái)保護(hù)地下電纜運(yùn)行，墊置式開關(guān)柜，單 位變電站變壓器。每個(gè)極接地的接地電阻通常是 15 歐姆或更小。在高海拔系統(tǒng) 中，基本上是對(duì)地電阻大于 15 歐姆，尤其是在干燥的夏季。在這些高點(diǎn)，研磨 棒極接地系統(tǒng)，在 1960 年，企圖以減少雷擊停電驅(qū)動(dòng)和保稅。這些嘗試只是部 分成功地降低停電率。從浪涌保護(hù)的角度來(lái)看，使用各種不同的桿件結(jié)構(gòu)（列 直插式，角，角，死路，等），和絕緣體及使用的硬件的各種不允許每 13.8 千 伏架空線具有均勻的沖擊閃絡(luò)分類評(píng)價(jià)（170 千伏，等）或一個(gè)數(shù)值的的 BIL 電壓類（95 千

31、伏 BIL，等等）。在分析中為了簡(jiǎn)單起見，每個(gè)分類的額定電壓 建筑類（15 千伏，34 千伏，69 千伏）架空線。六七八個(gè)架空線（饋線 1 至 6） 建立典型的 REA 標(biāo)準(zhǔn)水平木橫擔(dān)，利用單級(jí)的 ANSI 55-5 瓷針式絕緣子（標(biāo)稱 15 千伏絕緣）。架空地線相導(dǎo)線的屏蔽角通常是 45 度。一架空線（饋線 7）建 延長(zhǎng)線傳輸型木桿建設(shè)，因?yàn)檫@是已產(chǎn)生的電能反饋到電網(wǎng)的研究設(shè)施。這條 線極結(jié)構(gòu)耐久的建設(shè)的其中利用雙 ANSI 52-3 瓷懸式絕緣子支持（標(biāo)稱 34 千伏 絕緣）。饋線 7 的架空地線的相導(dǎo)體的屏蔽角通常是 30 度。在 1969 年，架空線 （饋線 8）有意建立“抗雷擊”試圖

32、減少雷電造成的停電。該行的極結(jié)構(gòu)階段階 段超過 24 英寸長(zhǎng)的玻璃纖維懸掛支架與雙 ANSI 52-3 瓷懸式絕緣子，支持標(biāo)稱 69 千伏絕緣的導(dǎo)體。饋線 8 架空地線的相導(dǎo)體的屏蔽角通常是 30 度。編制各 八個(gè) 13.8 千伏饋線故障數(shù)據(jù)列于表 I 中，沿饋線結(jié)構(gòu)，海拔高度，長(zhǎng)度，和年 齡的相關(guān)信息。故障分析的一個(gè)重要發(fā)現(xiàn)是，與天氣有關(guān)的事件占了一半以上（56）的 饋線停電記錄。五十七名 76 天氣有關(guān)的中斷是由于雷擊。絕緣擊穿損壞，由于 雷擊還涉嫌至少有十幾觀察到的設(shè)備故障。數(shù)據(jù)表明架空線路經(jīng)過地勢(shì)高，是不可靠的，因?yàn)槔讚麸L(fēng)險(xiǎn)更大。例如，饋線 3 最錄制中斷（48），其中三分之二 是由于與天氣有關(guān)的事件，這也是最高的饋線線廠區(qū)，上升到海拔 450 英尺以 上的參考山谷高度。也觀察到架空線更長(zhǎng)，更多的變電站和設(shè)備連接不可靠 （多接觸雷擊和更多的設(shè)備失?。?。行的年齡似乎并不顯著減輕其只要足夠的維 護(hù);線中斷的頻率有一個(gè)顯著的增加作為線路歲。正如所預(yù)料的，實(shí)證的數(shù)據(jù)列 于表我確認(rèn)兩架空線路絕緣已到一個(gè)更高的水平（34 或 69 千伏），有顯著更好 的可