輸電線路的距離保護(hù)中英文翻譯

1、輸電線路的距離保護(hù)在過電流保護(hù)靈敏度低或選擇性差時(shí)，應(yīng)當(dāng)考慮采用距離保護(hù)。距離保 護(hù)通常用于輸電線路相間短路的主保護(hù)和后備保護(hù)，裝有快速自動(dòng)重合閘的 線路不需要保持穩(wěn)定性，而且在線路末端區(qū)域短路時(shí)容許短時(shí)間延時(shí)。過電 流保護(hù)通常用于接地短路的主保護(hù)和后備保護(hù)，但接地故障也逐漸有運(yùn)用距 離保護(hù)的趨勢。單段式距離保護(hù)被用于發(fā)電機(jī)出線端相間短路的后備保護(hù)，同時(shí)，單段 距離保護(hù)也可方便的用于電力變壓器故障的后備保護(hù)。但在目前，還是用反 時(shí)限過電流保護(hù)作為電力變壓器故障的后備保護(hù)。距離保護(hù)比電流保護(hù)更好，因?yàn)榫嚯x保護(hù)受短路電流大小變化的影響比 電流保護(hù)小的多，因此，距離保護(hù)受電力系統(tǒng)運(yùn)行方式的影響非常小

2、。這是 因?yàn)?，距離保護(hù)的繼電器動(dòng)作是依據(jù)阻抗而不是電流。一、全阻抗繼電器、電抗繼電器和電阻繼電器的選擇因?yàn)榻拥仉娮枋强勺兊模拥鼐嚯x繼電器必須幾乎不受短路電阻大的 變化的影響。因此，電抗保護(hù)更適用于接地保護(hù)。對(duì)于相間保護(hù)，每一種類型都有它的優(yōu)點(diǎn)和缺點(diǎn)。在非常短的線路段， 使用電抗型繼電器更好的原因在于它可以迅速的保護(hù)更長的線路。這是因?yàn)?電抗繼電器實(shí)際上不受過渡電阻的影響，這或許是與線路全阻抗繼電器最大 的區(qū)別。另一方面，在系統(tǒng)中產(chǎn)生嚴(yán)重的同步振蕩時(shí)，電抗型距離保護(hù)在系 統(tǒng)中的某個(gè)區(qū)域很可能發(fā)生誤動(dòng)作，除非提供額外的保護(hù)裝置防止這種情況 發(fā)生。電阻型繼電器最適合用于可能發(fā)生嚴(yán)重的同步震蕩的長

3、線路的相間短 路保護(hù)。它可以不需要裝設(shè)額外的保護(hù)設(shè)備防止線路發(fā)生同步振蕩時(shí)發(fā)生誤 動(dòng)作。當(dāng)電阻型保護(hù)適合保護(hù)任何給定的線路段時(shí)，它的動(dòng)作特性曲線在 R-X圖表中的區(qū)域最小，這意味著它受其他異常系統(tǒng)情況的影響比受線路故 障的影響??；換句話說，在所有的距離保護(hù)中它最具有選擇性。因?yàn)殡娮枥^ 電器受過渡電阻的影響比其他類型的大，所以它適用于長線路。實(shí)際上它與 方向繼電器和測量阻抗繼電器聯(lián)合使用時(shí)將使它可靠性更好。全阻抗繼電器能較好的實(shí)用于中等長度線路的相間短路保護(hù)，而不實(shí)用于太長或太短線路的保護(hù)。過渡電阻對(duì)全阻抗繼電器的影響比對(duì)電抗繼電器 的影響大，而比對(duì)電阻繼電器的影響??；系統(tǒng)同步振蕩對(duì)全阻抗繼電器

4、的影 響比對(duì)電抗繼電器的影響小，而比對(duì)電阻繼電器的影響大。如果一個(gè)阻抗繼 電器的特性被補(bǔ)償，可以使它成為一個(gè)改良的繼電器，既可以類似于電抗繼 電器的特性也可以類似于電阻繼電器的特性，但它總是需要一個(gè)獨(dú)立的方向 元件。各種類型的距離繼電器在它們最適用的線路長度范圍上沒有嚴(yán)格的劃 分，實(shí)際上，這些區(qū)域存在著許多重疊。同樣，系統(tǒng)中發(fā)生的變化，比如線 路接線端的增加，可能要改換一種更實(shí)用于這種特殊區(qū)域的繼電器類型。因 此，應(yīng)該了解距離保護(hù)所有的性能，選用最適合各自需要的繼電器類型。在 某些情況下在同一類型的保護(hù)中能獲得更好的選擇，除此之外，如果保護(hù)被 用在最適合的各條線路上，相鄰線路上的不同類型的保護(hù)

5、在選擇上沒有明顯 的不利的影響。二、距離保護(hù)的整定相間距離保護(hù)依據(jù)保護(hù)安裝位置到短路位置之間線路的正序阻抗對(duì)給 定的繼電器進(jìn)行阻抗整定，發(fā)生在這個(gè)范圍外的短路繼電器不動(dòng)作。接地距 離保護(hù)用同樣的方法進(jìn)行整定，盡管某些保護(hù)可以對(duì)零序阻抗作出反應(yīng)。整 定的這個(gè)阻抗，或者是它相應(yīng)的距離，稱為繼電器或元件的保護(hù)范圍。為了 近視接近目的，習(xí)慣上取定一個(gè)正序阻抗平均值為每英里0.8歐姆的值作為 戶外輸電線路架設(shè)的保護(hù)范圍，并且可以忽略電抗。精確的數(shù)據(jù)在電力系統(tǒng) 分析書中是可以找到的。在整定相間或接地阻抗繼電器使初級(jí)阻抗轉(zhuǎn)化為使用的二次阻抗時(shí)，可 以使用下面公式：（；丁 ratio/心仁=已口匚i X1 V

6、T lalio式中CT ratio是高壓相電流與繼電器相電流的比值，VT ratio是高壓相電 壓與繼電器總相電壓在三相平衡條件下的比值。例如，對(duì)于一條50英里長、 輸電電壓為138KV的線路配置變比為600/5、Y型連接的CT時(shí)，二次的正序阻抗值為:m 11550 x O.Sxx 1.00 ohms.5 I 蹈.00。在實(shí)際中常整定距離保護(hù)第I段的保護(hù)范圍為雙端線路長度的80%90%, 或?yàn)槎喽司W(wǎng)絡(luò)中最近兩端距離的80%90%。這一段保護(hù)區(qū)內(nèi)沒有時(shí)間延遲。距離保護(hù)第II段保護(hù)的主要任務(wù)是保護(hù)第I段保護(hù)元件保護(hù)范圍外的 線路。它的整定值應(yīng)該可以使繼電器在線路末端甚至發(fā)生經(jīng)過渡電阻短路時(shí) 能動(dòng)作

7、。為了實(shí)現(xiàn)這個(gè)目的，第II段保護(hù)的保護(hù)范圍應(yīng)延伸到線路末端以 外。即使過渡電阻的影響沒有被考慮，也應(yīng)該把由于分支電流源的影響和由 于（1）整定依據(jù)的數(shù)據(jù)，（2）電流和電壓互感器和（3）繼電器產(chǎn)生誤差 的可能趨勢考慮在內(nèi)。通常第II段的保護(hù)區(qū)應(yīng)至少達(dá)到相鄰線路段的20%； 延伸到相鄰線路的范圍越大，用這個(gè)II段保護(hù)元件選擇的在下一級(jí)線路III 段保護(hù)區(qū)內(nèi)能被允許的誤差越多。圖表1第二段保護(hù)元件正常選擇的整定第II段保護(hù)范圍的最大值也有一個(gè)限制，在第II段保護(hù)范圍延伸的過遠(yuǎn) 的情況下，最短的相鄰線段上的距離保護(hù)的第二段保護(hù)元件選擇的第【段保 護(hù)范圍足夠小，如插圖一所示的那樣。瞬時(shí)過保護(hù)現(xiàn)象不需要考

8、慮繼電器有 較高的復(fù)位率，因?yàn)樵斐蛇^保護(hù)的瞬時(shí)現(xiàn)象將在第二段保護(hù)跳閘之前終止。 然而，如果復(fù)位的比率低，第二段保護(hù)區(qū)必須設(shè)置（1 ）足夠短的保護(hù)范圍， 這樣其過保護(hù)將不超出相同的條件下的相鄰線段的第一段保護(hù)區(qū)的范圍外， 或者（2 ）有足夠長的時(shí)間延遲作為相鄰線路段的第二段保護(hù)區(qū)動(dòng)作時(shí)間的 選擇，正如圖2所示的那樣。在這種情況下，相鄰線路上的繼電器的任何欠保護(hù)的趨勢必須被考慮。如果一條相鄰線非常圖表2相鄰線路保護(hù)第二段的延時(shí)特性短，以至于不可能得到繼電器作出反應(yīng)的需要的時(shí)間的選擇，這時(shí)增加時(shí)間 延遲是必要的，正如插圖2.中所示那樣。另外，第二保護(hù)區(qū)時(shí)間延遲應(yīng)足夠 的長以保證（1 ）在線路的另一端

9、的母線上的母線橫差保護(hù)，（2）在線路的 另一端的母線上的變壓器的變壓器橫差保護(hù)，或（3）相鄰線路的線路保護(hù) 最低的選擇性。這些各種各樣原理的斷路器切斷電路的時(shí)間也將影響第二段 的動(dòng)作時(shí)間。這個(gè)第二段的動(dòng)作時(shí)間通常大約為0.2秒到0.5秒。圖表3第三段保護(hù)元件的正常整定特性第III段保護(hù)作為相鄰線路的后備保護(hù)，它應(yīng)盡可能的保護(hù)到最長相鄰線 路的末端外，在最大的保護(hù)范圍內(nèi)，圖3是一個(gè)標(biāo)準(zhǔn)的后備保護(hù)特性圖。第 三段的動(dòng)作延時(shí)通常大約為0.4秒到1.0秒。為了保護(hù)到長的相鄰線路的末端 仍然用短線路的保護(hù)來選擇動(dòng)作時(shí)間，它可能需要用額外的延時(shí)來達(dá)到選擇性，如圖4所示那樣。%M瓦A1珀圖表4相鄰線路第三段

10、的延時(shí)整定三、過渡電阻對(duì)距離繼電器動(dòng)作的影響過渡電阻的區(qū)域在線路上是很小的一點(diǎn)，但在這個(gè)區(qū)域上距離繼電器的 動(dòng)作將會(huì)從無時(shí)限延遲為第二段動(dòng)作時(shí)間，或從第二段動(dòng)作時(shí)間延遲為后備 保護(hù)時(shí)間。我們考慮在無時(shí)限區(qū)內(nèi)的電孤使繼電器在第二時(shí)間內(nèi)動(dòng)作，在第 二段動(dòng)作區(qū)的電孤使繼電器在后備保護(hù)時(shí)間內(nèi)動(dòng)作，或在后備保護(hù)區(qū)的電弓瓜 阻止繼電器徹底動(dòng)作。換句話說，電孤的影響可能造成距離繼電器的拒動(dòng)。對(duì)于恰好在第一段保護(hù)區(qū)末的電弓瓜，我們關(guān)心的是它的初始特性。距離 繼電器第一段區(qū)動(dòng)作是那樣快速，以至于，如果在這種情況阻抗遭電孤襲擊 時(shí)，保護(hù)區(qū)將會(huì)在電孤略微伸展進(jìn)而增加其阻抗之前動(dòng)作。因此，我們可 以計(jì)算孤的初始特性以

11、確定相間短路導(dǎo)線間的最長等效距離，或相地短路絕 緣子串的距離。另一方面，對(duì)于在第二動(dòng)作時(shí)間或后備保護(hù)區(qū)的電弓瓜，應(yīng)該 考慮電孤輻射的影響，再者，繼電器整定的動(dòng)作時(shí)間在結(jié)果上也是一個(gè)重要 的方面。當(dāng)它在第二段或后備保護(hù)區(qū)時(shí)，在較長的時(shí)間內(nèi)電孤不得不在空氣中輻 射，實(shí)際上也是這樣的，電孤故障離繼電器越遠(yuǎn)，繼電器的動(dòng)作受的影響越 小，也就是說，在繼電器與故障點(diǎn)的線路阻抗越大，電孤阻抗增大時(shí)總的阻抗變化越小。另一方面，電孤離繼電器越遠(yuǎn)，它表現(xiàn)出的阻抗越大，因?yàn)閬?自線路末端繼電器的電流將變的更小，在下文將予以討論。由于電孤的影響，無時(shí)限保護(hù)區(qū)的保護(hù)范圍將略有減小，如果是不可 避免的，它可以被容許。我們

12、可以用電抗型或改良阻抗型距離繼電器將這個(gè) 縮小減到最小程度。第二段保護(hù)區(qū)的保護(hù)范圍不是一定由于電孤而減小，但 在電孤點(diǎn)下一級(jí)線路后的保護(hù)將不能被選擇；當(dāng)然，它們也受電孤的影響， 但影響不是很大。電抗型或改良阻抗型距離繼電器在使第二段保護(hù)區(qū)保護(hù)范 圍的縮小程度最小方面也是非常有用的。插圖5顯示了阻抗或電阻特性如何 被補(bǔ)償使它圖表5偏置繼電器的特性使電弧影響最小對(duì)電孤的反應(yīng)最小化。它也能通過使第二段保護(hù)區(qū)盡可能延伸來促進(jìn)這種情 況，以便在電孤的影響下容許一個(gè)特定的保護(hù)范圍。一般的保護(hù)不在后備保 護(hù)區(qū)使用電抗元件，而是使用全阻抗元件或電阻元件。如果電孤幅射太長， 后備保護(hù)元件動(dòng)作失敗，可以使用改進(jìn)的

13、阻抗元件，電阻元件或起動(dòng)元件的 特性可以被改進(jìn)使它的動(dòng)作受過渡電阻的影響減小。一些類型的距離繼電器 稍微的重新設(shè)定它的特性在防止電孤輻射太長方面是很有利的。盡管電孤本身實(shí)際上都是電阻，但從裝設(shè)保護(hù)的線路末端看它可以有一個(gè)容抗或感抗。電孤的電抗用下式來計(jì)算:式中：I1為從被保護(hù)線路末端流入電孤的電流，I2為從線路另一端流入電孤的電流，RA為電流（I1+I2）流過的電孤電阻。大量重要的實(shí)踐表明，正如上面的公式所示那樣，電孤阻抗的表現(xiàn)值比它實(shí) 際的大，而且它的值可能非常高。當(dāng)?shù)竭_(dá)線路的另一端后，電孤阻抗值將非 常的高，因?yàn)殡姽码娏鲗⒔档?。然而，它的出現(xiàn)對(duì)于保護(hù)的影響將不會(huì)再擴(kuò) 大，因?yàn)殡娏鳌?將變?yōu)?/p>

14、零。電孤的電阻對(duì)保護(hù)的影響是否比原來高還是低依 賴于距離斷路器斷開前和后電流的相對(duì)變化關(guān)系和實(shí)際值。附錄5LINE PROTECTION WITH DISTANCE RELADistance relaying should be considered when overcurrent relaying is too slow or is not selective. Distance relays are generally used for phase-fault primary and back-up protection on subtransmission lines, and on

15、transmission lines where high-speed automatic reclosing is not necessary to maintain stability and where the short time delay for end-zone faults can be tolerated. Overcurrent relays have been used generally for ground-fault primary and back-up protection, but there is a growing trend toward distanc

16、e relays for ground faults also.Single-step distance relays are used for phase-fault back-up protection at the terminals of generators. Also, single-step distance relays might be used with advantage for back-up protection at power-transformer tanks, but at the present such protection is generally pr

17、ovided by inverse-time overcurrent relays.Distance relays are preferred to overcurrent relays because they are not nearly so much affected by changes in short-circuit-current magnitude as overcurrent relays are, and , hence , are much less affected by changes in generating capacity and in system con

18、figuration. This is because, distance relays achieve selectivity on the basis of impedance rather than current.THE CHOICE BETWEEN IMPEDANCE, REACTANCE, OR MHOBecause ground resistance can be so variable, a ground distance relay must be practically unaffected by large variations in fault resistance.

19、Consequently, reactance relays are generally preferred for ground relaying.For phase-fault relaying, each type has certain advantages and disadvantages. For very short line sections, the reactance type is preferred for the reason that more of the line can be protected at high speed. This is because

20、the reactance relay is practically unaffected by arc resistance which may be large compared with the line impedance, as described elsewhere in this chapter. On the other hand, reactance-type distance relays at certain locations in a system are the most likely to operate undesirably on severe synchro

21、nizing-power surges unless additional relay equipment is provided to prevent such operation.The mho type is best suited for phase-fault relaying for longer lines, and particularly where severe synchronizing-power surges may occur. It is the least likely to require additional equipment to prevent tri

22、pping on synchronizing-power surges. When mho relaying is adjusted to protect any given line section, its operating characteristic encloses the least space on the R-X diagram, which means that it will be least affected by abnormal system conditions other than line faults; in other words, it is the m

23、ost selective of all distance relays. Because the mho relay is affected by arc resistance more than any other type, it is applied to longer lines. The fact that it combines both the directional and the distance-measuring functions in one unit with one contact makes it very reliable.The impedance rel

24、ay is better suited for phase-fault relaying for lines of moderate length than for either very short or very long lines. Arcs affect an impedance relay more than a reactance relay but less than a mho relay. Synchronizing-power surges affect an impedance relay less than a reactance relay but more tha

25、n a mho relay. If an impedance-relay characteristic is offset, so as to make it a modified, relay, it can be made to resemble either a reactance relay or a mho relay but it will always require a separate directional unit.There is no sharp dividing line between areas of application where one or anoth

26、er type of distance relay is best suited. Actually, there is much overlapping of these areas. Also, changes that are made in systems, such as the addition of terminals to a line, can change the type of relay best suited to a particular location. Consequently, to realize the fullest capabilities of d

27、istance relaying, one should use the type best suited for each application. In some cases much better selectivity can be obtained between relays of the same type, but, if relays are used that are best suited to each line, different types on adjacent lines have no appreciable adverse effect on select

28、ivity.THE ADJUSTMENT OF DISTANCE RELAYSPhase distance relays are adjusted on the basis of the positive-phase-sequence impedance between the relay location and the fault location beyond which operation of a given relay unit should stop. Ground distance relays are adjusted in the same way, although so

29、me types may respond to the zero-phase-sequence impedance. This impedance, or the corresponding distance, is called the reach of the relay or unit. For purposes of rough approximation, it is customary to assume an average positive-phase-sequence-reactance value of about 0.8 ohm per mile for open tra

30、nsmission-line construction, and to neglect resistance. Accurate data are available in textbooks devoted to power-system analysis.To convert primary impedance to a secondary value for use in adjusting a phase or ground distance relay, the following formula is used:(T ratio= A pr i 氐-VT laliowhere th

31、e CT ratio is the ratio of the high-voltage phase current to the relay phase current, and the VT ratio is the ratio of the high-voltage phase-to-phase voltage to the relay phase-to-phase voltage-all under balanced three-phase conditions. Thus, for a 50-mile, 138-kv line with 600/5 wye-connected CTs,

32、 the secondary positive-phase-sequence reactance is about600115,x 0.S x x. = 4.00 ohms.513亂 ODOIt is the practice to adjust the first, or high-speed, zone of distance relays to reach to 80% to 90% of the length of a two-ended line or to 80% to 90% of the distance to the nearest terminal of a multite

33、rminal line. There is no time-delay adjustment for this unit.The principal purpose of the second-zone unit of a distance relay is to provide protection for the rest of the line beyond the reach of the first-zone unit. It should be adjusted so that it will be able to operate even for arcing faults at

34、 the end of the line. To do this, the unit must reach beyond the end of the line. Even if arcing faults did not have to be considered, one would have to take into account an underreaching tendency because of the effect of intermediate current sources, and of errors in: (1) the data on which adjustme

35、nts are based, (2) the current and voltage transformers, and (3) the relays. It is customary to try to have the second-zone unit reach to at least 20% of an adjoining line section; the farther this can be extended into the adjoining line section, the more leeway is allowed in the reach of the third-

36、zone unit of the next line-section back that must be selective with this second-zone unit.The maximum value of the second-zone reach also has a limit. Under conditions ofmaximum overreach, the second-zone reach should be short enough to be selective with the second-zone units of distance relays on t

37、he shortest adjoining line sections, as illustrated in Fig. 1. Transient overreach need not be considered with relays having a high ratio of reset to pickup because the transient that causes overreach will have expired before the second-zone tripping time. However, if the ratio of reset to pickup is

38、 low, the second-zone unit must be set either (1) with a reach short enough so that its overreach will not extend beyond the reach of the first-zone unit of the adjoining line section under the same conditions, or (2) with a time delay long enough to be selective with the second-zone time of the adj

39、oining section, as shown in Fig. 2. In this connection, any underreaching tendencies of the relays on the adjoining line sections must be taken into account. When an adjoining line is so short that it is impossible to get the required selectivity on the basis of react, it becomes necessary to increa

40、se the time delay, as illustrated in Fig. 2. Otherwise, the time delay of the second-zone unit should be long enough to provide selectivity with the slowest of (1) bus-differential relays of the bus at the other end of the line(2)transformer-differential relays of transformers on the bus at the othe

41、r end of the line,Fig. 2. Second-zone adjustment with additional time for selectivity with relay of a very short adjoining line section.or (3) line relays of adjoining line sections. The interrupting time of the circuitbreakers of these various elements will also affect the second-zone time. This se

42、cond-zone time is normally about 0.2 second to 0.5 second.Fig. 3. Normal selective adjustment of third-tone unit.The third-zone unit provides back-up protection for faults in adjoining line sections.So far as possible, its reach should extend beyond the end of the longest adjoining linesection under

43、 the conditions that cause the maximum amount of underreach, namely, arcs and intermediate current sources. Figure 3 shows a normal back-up characteristic. The third-zone time delay is usually about 0.4 second to 1.0 second. To reach beyond the end of a long adjoining line and still be selective wit

44、h the relays of a short line, it may be necessary to get this selectivity with additional time delay, as in Fig. 4.Fig. 4. Third-zone adjustment with additional time for selectivity with relay of a short adjoining line snd to provide back-up protection for a long adjoining line.THE EFFECT OF ARCS ON

45、 DISTANCE-RELAY OPERATIONThe critical arc location is just short of the point on a line at which a distance relays operation changes from high-speed to intermediate time or from intermediate time to back-up time. We are concerned with the possibility that an arc within the high-speed zone will make

46、the relay operate in intermediate time, that an arc within the intermediate zone will make the relay operate in back-up time, or that an arc within the back-up zone will prevent relay operation completely. In other words, the effect of an arc may be to cause a distance relay to underreach.For an arc

47、 just short of the end of the first- or high-speed zone, it is the initial characteristic of the arc that concerns us. A distance relays first-zone unit is so fast that, if the impedance is such that the unit can operate immediately when the arc is struck, it will do so before the arc can stretch ap

48、preciably and thereby increase its resistance. Therefore, we can calculate the arc characteristic for a length equal to the distance between conductors for phase-to-phase faults, or across an insulator string for phase-to-ground faults. On the other hand, for arcs in the intermediate-time or back-up

49、 zones, the effect of wind stretching the arc should be considered, and then the operating time for which the relay is adjusted has an important bearing on the outcome.Tending to offset the longer time an arc has to stretch in the wind when it is in the intermediate or back-up zones is the fact that

50、, the farther an arcing fault is from a relay, the less will its effect be on the relays operation. In other words, the more line impedance there is between the relay and the fault, the less change there will be in the total impedance when the arc resistance is added. On the other hand, the farther

51、away an arc is, the higher its apparent resistance will be because the current contribution from the relay end of the line will be smaller, as considered later.A small reduction in the high-speed-zone reach because of an arc is objectionable, but it can be tolerated if necessary. One can always use

52、a reactance-type or modified-impendance type distance relay to minimize such reduction. The intermediate-zone reach must not be reduced by an arc to the point at which relays of the next line back will not be selective; of course, they too will be affected by the arc, but not so much. Reactance-type

53、 or modified-impendance-type distance relays are useful here also for assuring the minimum reduction in second-zone reach. Figure 5 shows how an impedance or mho characteristic can be offset to minimize its susceptibility to an arc. One can also help the situation by making the second-zone reach as long as possible so that a certain amount of