电气专业外文翻译

1、外文资料翻 译Reliability of Lightning ResistantOverhead Distribution LinesLighting continues to be themajor causeof outagesonoverheadpower distribution lines. Through laboratory testing and field observationsand measurements, the properties of a lightning stroke andits effects on electrical distribution s

2、ystem componentsare well-understoodphenomena.This paperpresentsa compilation of 32 yearsof historical recordsfor outage causes,duration, and locationsfor eight distribution feedersat the Oak Ridge National Laboratory (ORNL) .Distribution type lightning arresters are placed at dead-endand angle struc

3、tures at pole mounted wormer locations and at high points on the overheadline. Station class lightning arresters are used to protect undergroundcable runs, pad mounted switchgear and unit substation transformers. Resistanceto earth of eachpole ground is typically 15 ohms or less. At higher elevation

4、s 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 1960's in an attempt to decreaselightning outages. Theseattempts were only partially s

5、uccessful 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 13.8 kV overhead line to be categorized with a uniform impulse flashover rating (

6、170 kV, etc.) or a numerical BIL voltage class (95 kV BIL; etc.). For simplicity purposes in the analysis, each overheadline was categorized with a nominal voltage construction class (15 kV, 34 kV, or 69 KV). Six of the eight overhead lines (feeders 1 through 6) were built with typical REA Standardh

7、orizontal wood cross arm construction utilizing single ANSI Class55- 5 porcelain pin insulators (nominal 15 kV insulation). The shield angle of the overhead ground wire to the phase conductors is typically 45 degrees. One overhead line (feeder 7) was built with transmission type wood pole constructi

8、on becausethe line extended to a research facility which was to have generatedelectricalpower to feed back into the grid. Pole structure of this line are of durable wood cross aconstruction which utilize double ANSI 52-3 porcelain suspension insulators to support the conductors (nominal 34 kV insula

9、tion). 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 in an attempt to reduce lightning causedoutages. Pole structures of the lin

10、e have phase over phase 24-inch long fiberglass suspension brackets with double ANSI 52-3 porcelain suspension insulatorsto support the conductors (nominal 69 kV insulation). The shield angle of the overhead ground wire to thephaseconductors for feeder 8 istypically 30 degrees. The failure data was

11、compiled for each of the eight 13.8 kV feeders and is presentedin Table, along with pertinent information regarding feeder construction, elevation, length, and age.A key finding of the failure analysis is that weather-related events account for over half (56%) of the feeder outagesrecorded. Fifty-se

12、ven of the 76 weather-related outageswere attributed to lightning. Insulation breakdown damagedue to lightning is also suspectedin at least a dozen of the equipment failures observed. The data indicates overhead lines which pass over high terrain are less reliable becauseof the greater exposure to l

13、ightning. 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 above the reference valley elevation. Overhead lines that are longer and to which more sub

14、stations 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 long as adequatemaintenanceis performed; none of the lines have had a notable increasein

15、the frequency of outages as the lines have aged. As would be expected,the empirical data presentedin Table I confirms the two overhead lines which have been insulated to a higher level (34 or 69 KV) have significantly better reliability records than those utilizing 15 kV class construction. Feeder 7

16、 (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 to the 15 kV class lines, yet they have a combined failure rate of 0.22 failures per year v

17、ersus 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 construction, outage rates are reduced by limiting the number of flashovers and the resultant power

18、follow which causesan 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 outages are also reduced. This is beneficial for critical facilities and processes which ca

19、nnot tolerate even momentary outages. An additional benefit is that outagesdue to animal contact are also reduced becauseof the greater distance from phase conductor to ground on pole structures. Distribution line equipment to increase line insulation values are "off the shelf" items and p

20、roven 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 replacementof standardpin insulators with line post insulators of greater flashover value is an effective

21、meansto 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 fiberglass, polymer, and epoxy technologies provide an affordable means to increase

22、line insulation.While the use of increasedinsulation levels to reduce lightning flashovers and the resultant outages on overhead distribution lines has been thoroughly tested and demonstratedin laboratory and experimental tests 5, long term history field data has positively demonstrated that the use

23、 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 increasedinsulation and a smaller shielding angle is an impressive and cost effective means to appreciably increase the reliability of

24、overhead distribution lines.This reliability study clearly illustrates that the insulationrequirements for high-reliability distribution feeders should be determined not by the 60 Hz operatingvoltage but rather by withstand requirementsfor the lightning transients or other high voltage transients th

25、at are impressed upon the line. Electrical equipment (switchgear, insulators, transformers, cables,etc.) have a reserve (BElevel or flashover value) to handle momentary over voltages, and by increasing that reserve, the service reliability is appreciably increased. As the electrical industry gradual

26、ly 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 or replacement effort. In considering new or upgradedoverhead line construction,

27、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 effectiveness varies with the application and the conditions to which it is be applied. Econo

28、mic 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 distribution lines, which can have a significant reduction in maintenance cost due to less

29、replacement materials and a large reduction in overtime hours for maintenancecrews.抗雷击架空配电线 路的可靠性闪电仍然是架空配电线路上的中断1 的主要原因。通过实验室测试和现场观察和测量，雷击和其对配电系统组件的属性是很好理解的现象。本文提出了一个 32 年的历史记录，停运的原因，时 间，地点，在橡树岭国家实验室的八个配电馈线汇编。配电型避雷器在死胡同和角度的结构被放置在极安装W 奥 莫尔的位置，并在高点上的架空线。站级避雷器是用来保护地下电缆运行，垫置式开关柜，单位变电站变压器。每个极接地的接地电阻通常是15

30、 欧姆或更小。在高海拔系统中，基本上是对地电阻大于15 欧姆， 尤 其是在干燥的夏季。在这些高点，研磨棒极接地系统，在1960 年 ，企图以减少雷击停电驱动和保税。这些尝试只是部分成功地降低停电率。从浪涌保护的角度来看，使用各种不同的杆件结构（列直插式，角，角，死路，等），和 绝缘体及使用的硬件的各种不允许每13.8 千伏架空线具有均匀的冲击闪络分类评价（170 千伏，等）或 一个数值的的BIL 电压类（ 95千伏 BIL， 等等 ）。在 分析中为了简单起见，每个分类的额定电压建筑类（ 15 千伏， 34 千伏， 69 千伏）架空线。六七八个架空线（馈线1 至 6） 建立典型的 REA 标准水

31、平木横担，利用单级的ANSI 55-5 瓷针 式 绝缘子（标称15千伏绝缘）。架 空地线相导线的屏蔽角通常是45 度。一架空线（馈线7） 建 延长线传输型木杆建设，因为这是已产生的电能反馈到电网的研究设施。这条 线极结构耐久的建设的其中利用双ANSI 52-3 瓷悬式绝缘子支持（标称34 千 伏绝缘 ）。馈 线 7 的架空地线的相导体的屏 蔽角通常是30 度。在 1969 年，架空线（馈线8）有意建立“抗雷击 ”试图减少雷电造成的停电。该行的极结构阶段阶段超过 24 英寸长的玻璃纤维悬挂支架与 双 ANSI 52-3 瓷悬式绝 缘 子，支持标称69 千伏绝缘的导体。 馈线 8 架空地线的相导体

32、的屏蔽角通常是30 度。编制各八个 13.8 千伏馈线故 障数据列于表I 中， 沿 馈线结构，海拔高度， 长度，和年龄的相关信息。故障分析的一个重要发现是，与天气有关的事件占了一半以上（56）的馈线停电记录。五十七名76 天气有关 的 中断是由于雷击。绝缘击穿损坏，由于雷击还涉嫌至少有十几观察到的设备故障。数据表明架空线路经过地势高，是不可靠的，因为雷击风险更大。例如，馈线3 最录制中断（48），其中三分之二是由于与天气有关的事件，这也是最高的馈线线厂区，上升到海拔450 英尺以上的参考山谷高度。也观察到架空线更长，更多的变电站和设备连接不可靠（多接触雷击和更多的设备失败）。行 的年龄似乎并不显着减轻其只要足够的维护 ;线中断的频率 有一个显着的增加作为线路岁。正如所预料的，实证的数据列于表我确认两架空线路绝缘已到一个更高的水平（34 或 69 千伏 ），