电气专业外文翻译

1、精选优质文档-倾情为你奉上精选优质文档-倾情为你奉上专心-专注-专业专心-专注-专业精选优质文档-倾情为你奉上专心-专注-专业外文资料翻译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

30、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 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

31、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

32、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），有显着更好 的可