電氣外文翻譯--電力系統(tǒng)故障

1、<p><b>　　中文3200字</b></p><p>　　附錄Ⅰ：專業(yè)相關(guān)文獻(xiàn)翻譯</p><p>　　Faults on power system</p><p>　　Each year new designs of equipment bring about increased reliability of operatio

2、n. Nevertheless, equipment failures and interference by outside sources occasionally result in faults on electric power system. On the occurrence of power from the generating stations to the loads may be unsatisfactory o

3、ver a considerable area, and if the faulted equipment is not promptly disconnected from the remainder of the system, damage may result to other pieces of operating equipment.</p><p>　　A fault is the unintent

4、ional or intentional connecting together of two or more conductors which ordinarily operate with a difference of potential between them. The connection between the conductions may be by physical metallic contact or it ma

5、y be through an arc. At the fault, the voltage between the two parts is reduced to zero in the case of metal-to-metal contacts, or to a very low value in case the connection is through an arc. Currents of abnormally high

6、 magnitude flow the network to the po</p><p>　　A distinction must be made between a fault and an overload. An overload implies only that loads greater than the designed value have been imposed on system. Und

7、er such a circumstance the voltage at the overload point may be low, but not zero. This undervoltage condition may extend for some distance beyond the overload point into the remainder of the system. The currents in the

8、overloaded equipment are high and may exceed the thermal design limits. Nevertheless, such currents are substantially lo</p><p>　　Overloads are rather common occurrence in homes. For example, a housewife mig

9、ht plug five waffle irons into the kitchen circuit during a neighborhood party. Such an over-load, if permitted to continue, would cause heating of the wires from the power center and might eventually start a fire. To pr

10、event such trouble, residential circuits are protected by fuse or circuit breakers which open quickly when currents above specified values persist. Distribution transformers are sometimes overloaded as c</p><p

11、>　　Faults of many types and causes may appear on electric power systems. many of us in our homes have seen frayed lamp cords which permitted the tow conductors of the cord to come in contact with each other. When this

12、 occurs, there is a resulting flash, and if breaker or fuse equipment functions properly, the circuit is opened.</p><p>　　Overhead lines, for the most part, are constructed of bare conductors. These are some

13、times accidentally brought together by action of wing, sleet, trees, cranes, airplanes, or damage to supporting structures. Overvoltages due to lightning or switching may cause flashover of supporting or from conductor t

14、o conductor. Contamination on insulators sometimes results in flashover even during normal voltage conditions.</p><p>　　The conductors of underground cables are separated from each other and from ground by s

15、olid insulation, which may be oil-impregnated paper or a plastic such as polyethylene. These materials undergo some deterioration with age, particularly if overloads on the cables have resulted in their operation at elev

16、ated temperature. Any small void present in the body of the insulating material will result in ionization of the gas contained therein, the products of which react unfavorably with the insulati</p><p>　　Tran

17、sformer failures may be the result of insulation deterioration combined with overvoltages due to lightning or switching transients. Short circuits due to insulation failure between adjacent turns of the same winding may

18、result from suddenly applied overvoltages. Major insulation may fail, permitting arcs to be established between primary and secondary windings or between a winding and grounded metal parts such as the core or tank.</p

19、><p>　　Generators may fail due to breakdown of the insulation between adjacent turns in the same slot, resulting in a short circuit in a single turn of the generator. Insulation breakdown may also occur betwee

20、n one of the windings and the grounded steel structure in which the coils are embedded. Breakdown between different windings lying in the same slot results in short-circuiting extensive sections of machine.</p>&l

21、t;p>　　Balanced three-phase faults, like balanced three-phase loads, may be handled on a lineto-neutral basis or on an equivalent single-phase basis. Problems may be solved either in terms of volts, amperes, and ohms.

22、The handling of faults on single-phase lines is of course identical to the method of handling three-phase faults on an equivalent single-phase basis. </p><p>　　Voltage transformers</p><p>　　V

23、oltage transformers are used with voltmeters, watt-meters, watt-hour meters, power-factor meters, frequency meters, synchroscopes and synchronizing apparatus, protective and regulating relays, and the no-voltage and over

24、-voltage trip coils of automatic circuit breakers. One transformer can be used for a number of instruments at the same time if the total current taken by the instruments does not exceed that for which the transformer is

25、designed and compensated.</p><p>　　Voltage transformers are generally designed for a capacity of about 200 volt-amp. There are two causes of errors in voltage transformers, namely, ratio error and phase-angl

26、e error. The part of these errors due to the exciting current is constant for any particular voltage. It can be reduced to a minimum by choosing the best quality of iron and working it at a low magnetic density. The part

27、 of the errors due to the load current varies directly with the load and can be minimized by making the resi</p><p>　　Voltage transformers are compensated for their iron losses at rated voltage. When used on

28、 some other voltage, either higher or lower, an error is introduced. In general this error will not be more than 0.15 percent of rated voltage. A voltage transformer should never be used on a circuit whose voltage is mor

29、e than 10 percent above the rated voltage of the transformer.</p><p>　　The secondary terminals of a voltage transformer should never be short-circuited, a heavy current will flow which, if continued, will bu

30、rn out the windings. In order to protect the system against sustained short circuits in the transformer circuit, it is generally recognized as good practice to introduce into the primary circuit a resister and fuse, thes

31、e been connected in series. The resistors are designed to limit the current to about 20 to 40 amp., while the fuses are designed to break such c</p><p>　　Current transformers</p><p>　　Current tr

32、ansformers are used with ammeters, watt-meters, power-factor meters, watt-hour meters, compensators, protective and regulating relays, and the trip coil of circuit breakers. One current transformer can be used to operate

33、 not to exceed that for which the transformer is designed and compensated.</p><p>　　The current transformer is connected directly in series with the line, and usually has a fixed number of instruments in the

34、 secondary. A rise or fall in the line current requires a corresponding rise or fall in the secondary voltage to force the secondary current through the impedance of the meter load. the magnetic flux in the iron, which s

35、upplies the voltage, thus follows the rise and fall of the primary or line current.</p><p>　　The instruments connected in the secondary circuit of the transformer are placed in series, so that the secondary

36、current will pass through each instrument. As the instrument are added, higher voltage is required to force the current through the instruments. This requires a high magnetic density in the iron. A higher magnetic densit

37、y increases both the iron loss and the magnetizing current; hence both the ratio and the phase-angle errors are magnified. For the sake of accuracy, therefore, there </p><p>　　The secondary circuit of a curr

38、ent transformer should never be opened while the primary is carrying current. If it is necessary to disconnect instruments, the secondary should first be short-circuited. If the secondary circuit is opened, a difference

39、of potential is developed between terminals which is dangerous to anyone coming in contact with the meters of leads. The cause of this high voltage is that with open secondary circuit all the primary ampere turns are eff

40、ective in producing flux in t</p><p><b>　　Arresters</b></p><p>　　One of the means of protecting transmission equipment is the surge arrester. two types of surge arresters may be used

41、 for this reason: active gap (SiC) and gapless (ZnO) metal oxide surge arresters.</p><p>　　Active gap (SiC) arrester</p><p>　　The two principal components of active gap surge arresters (diverter

42、s) are the spark gap and the non-linear resister. One of the earlier designs was the lightning arrester with plate gaps, which is still used today in some medium voltage networks. At still higher voltages, arresters with

43、 magnetically blow spark gaps are more commonly used, in particular in EHV networks (300—750kV). These consist mainly of three parts: spark gaps, discharge resistors and a grading system that monitors the distrib</p&g

44、t;<p>　　ZnO oxide arresters</p><p>　　The materials used for ZnO arresters are uniformly mixed, formed into grains, and sintered through special processes at temperatures between 1100 and 3500℃. The ga

45、pless surge arrester obtained using ZnO elements has the property that its resistance decreases sharply as the voltage across it increases.</p><p>　　In order to keep the stress on the system insulation as lo

46、w as possible, a good overvoltage protection system or, an arrester has to meet and fulfill the following requirements.</p><p>　　it must withstand the normal phase to earth voltage of the system for the whol

47、e of its operating life, even in the presence of pollution and after repeated discharges of high energy, such as are expected in a network;</p><p>　　it must be withstand, without damage, temporary over-volta

48、ge caused by earth faults and other system transient conditions and discharge these over-voltages to earth without causing an earth fault;</p><p>　　interruption of the following current;</p><p>

49、　　the energy absorption capability must be such that, even after the most severe switching surges and temporary over-voltages, the temperature of the blocks does not rise to a point where thermal runaway sets in;</p&g

50、t;<p>　　protection level must be maintained as low as possible.</p><p>　　The newly developed ZnO surge arrester with its excellent high non-linearity characteristic, energy capability and protective p

51、erformance can meet these conditions and fulfill these requirements.</p><p><b>　　中文譯文：</b></p><p><b>　　電力系統(tǒng)故障</b></p><p>　　每年新設(shè)計的電力設(shè)備都使系統(tǒng)的可靠性不斷提高,然而,設(shè)備的使用不當(dāng)以

52、及一些偶然的外在因素均會導(dǎo)致系統(tǒng)故障的發(fā)生.發(fā)生故障時，電流、電壓變得不正常，從電廠到用戶的送電在相當(dāng)大的區(qū)域不令人滿意。此時若故障設(shè)備不立即從系統(tǒng)中切除的話，則會造成其他運(yùn)行設(shè)備的損壞。</p><p>　　故障是由于有意或無意地使兩個或更多的導(dǎo)體相接觸而造成的。到體之間是有電位存在的，而這種接觸可能是金屬性接觸，也可能是電弧引起的。如果是前者造成的故障，則兩部分導(dǎo)體之間電壓會降低為零；若為后者，則電壓變得很低

53、，超常的大電流經(jīng)過網(wǎng)絡(luò)流至故障處。此短路電流通常會大大超出導(dǎo)線以及供電發(fā)電機(jī)的熱承受能力，其結(jié)果，溫度的升高會導(dǎo)致導(dǎo)體燒毀或絕緣體焦化。在允許的期限內(nèi)，最靠近故障處的電壓會變得很低，致使用電設(shè)備無法運(yùn)行。顯然，系統(tǒng)設(shè)計者必須事先考慮到故障可能發(fā)生在什么地方，能夠推測出故障期間的各種情況，提供調(diào)節(jié)好的設(shè)備，以便驅(qū)動為將故障設(shè)備切除所必需斷開的開關(guān)能夠跳閘。通常希望此時系統(tǒng)無其他開關(guān)打開，否則會導(dǎo)致系統(tǒng)線路不必要的修改。</p>

54、<p>　　過負(fù)荷與故障是兩個概念。過負(fù)荷僅指施加于系統(tǒng)的負(fù)荷超過了設(shè)計值。發(fā)生這種情況時，過負(fù)荷處的電壓可能很低，但并等于零。這種電壓不足的情形可能會越過過負(fù)荷處蔓延一定距離，進(jìn)而影響系統(tǒng)其他部分。過負(fù)荷設(shè)備的電流變大而超過預(yù)定的熱極限，但是這種情況比發(fā)生故障時的電流要小。此時，供電雖往往能維持，但電壓較低。</p><p>　　過負(fù)荷的情況經(jīng)常在家里發(fā)生，例如請街坊鄰居聚會時，女主人可能將五個華

55、夫餅干烘烤器的插頭同時插入廚房的插座，諸如此類的過負(fù)荷倘若不能迅速處理的話，就會造成電力線發(fā)熱甚至釀成火災(zāi)。為了避免這種情況發(fā)生，須采用保險絲或斷路器來保護(hù)住宅區(qū)電路免受損壞。斷路器會在電流超出預(yù)定值時迅速切斷電路。當(dāng)用戶安裝的用電器增加時，也會超過變壓器負(fù)荷能力，因此有必要不時地監(jiān)視配電線路以確保在負(fù)荷增加時變壓器的容量也相應(yīng)增加。</p><p>　　電力系統(tǒng)會發(fā)生各種類型，由各種原因引起的故障。我們在家里看

56、到過破損的照明燈電線，使得其兩根導(dǎo)線相觸，并會發(fā)出弧光。如果此時斷路器或保險絲能夠正常工作，見分曉電路能被自動切斷。</p><p>　　大部分架空明線是用裸線架設(shè)的，有時由于風(fēng)、雪、或大樹、起重機(jī)，飛機(jī)及支撐物的損壞等因素會使導(dǎo)線偶然碰到一起。由雷電或開關(guān)瞬變過程引起的過電壓會在支撐物或?qū)w之間產(chǎn)生電弧，即使在電壓正常的情況下，絕緣材料的污染也回引起電弧。</p><p>　　通常采用油

57、浸電纜紙或聚乙烯一類固體塑料絕緣材料將埋地電纜中的導(dǎo)線與導(dǎo)線和導(dǎo)線與地隔開。這些絕緣材料會隨著時間的流失而老化，尤其是在過負(fù)荷引起高溫下運(yùn)行的時候更是如此。絕緣材料內(nèi)的空隙會造成氣體的電離，其生成物對絕緣不利。絕緣材料老化回引起絕緣性下降而導(dǎo)致導(dǎo)線短路。電纜故障的可能性會因雷電或開關(guān)瞬間引起的導(dǎo)線的電壓驟然變高而增加。</p><p>　　變壓器故障可能是由絕緣老化、加上雷電、開關(guān)瞬變過程導(dǎo)致的過電壓造成的。同一

58、繞組相鄰線圈之間由于絕緣問題造成的短路可能是由于突然遇到外加高電壓所致。絕緣失敗會在一次繞組與二次繞組之間或繞組與接地金屬部件（如鐵芯或變壓器外殼）之間產(chǎn)生電弧。</p><p>　　發(fā)電機(jī)故障可能是由于同一槽中相鄰線圈之間絕緣被破壞而造成的，其結(jié)果會導(dǎo)致發(fā)電機(jī)匝內(nèi)短路。絕緣損壞也可能發(fā)生在某一繞組與定子鐵芯的接地鋼結(jié)構(gòu)之間。同一槽內(nèi)不同繞組之間的絕緣損壞會導(dǎo)致電機(jī)大范圍短路。</p><p&

59、gt;　　像處理平衡三相負(fù)荷一樣，處理平衡三相故障也是依照基于由火線到零線的電路或等效單相電路的原則進(jìn)行?？梢酝ㄟ^電壓、電流和電阻的規(guī)律求解問題。當(dāng)然，單相線路上故障的處理方法也可用于在單相等效電路下三相故障的處理中。</p><p><b>　　電壓互感器</b></p><p>　　電壓互感器與電壓表、功率表、電能表、功率因數(shù)表、頻率表。同步檢測裝置和同期設(shè)備、保

60、護(hù)和調(diào)節(jié)繼電器以及自動化斷路器的失壓和過壓調(diào)閘線圈一起使用。只要儀表的總電流不超過互感器的設(shè)計的補(bǔ)償要求，一個互感器可以同時供多個儀表使用。</p><p>　　通常，電壓互感器繁榮容量設(shè)計為200VA電壓互感器的誤差有兩個，稱為變比誤差和相角誤差。對于任何電壓，這些誤差中由于勵磁電流而引起的部分是恒定的。通過選擇最佳質(zhì)量的鐵心和低磁場強(qiáng)度下運(yùn)行，可以將這個誤差減到最小。這些誤差中由于負(fù)荷電流引起的部分直接隨著負(fù)

61、荷變化，并且可以通過繞組電阻的減小來使其最小化。</p><p>　　需要對電壓互感器在額定電壓下的鐵芯損耗進(jìn)行補(bǔ)償。當(dāng)運(yùn)行在其他電壓時，無論電壓高低，都會產(chǎn)生誤差?？偟膩碇v，當(dāng)使用電壓為額定電壓的50%~110%時，這些誤差都不會超過0.15%。電壓互感器不允許應(yīng)用于電壓超過其額定電壓10%的電路。</p><p>　　電壓互感器的二次側(cè)端子不允許短路。如果其二次側(cè)持續(xù)短路的話，將在二次

62、繞組中產(chǎn)生巨大電流，從而燒毀繞組。為了防止系統(tǒng)中電壓互感器電路持續(xù)短路，一個認(rèn)可的常用措施是在電壓互感器的一次側(cè)串連接入一個電阻器和熔斷器（保險）。電阻器的選擇是將電流限制到約20~40A，而熔斷器的選擇是按照能斷開這樣的電流來設(shè)計的。在正常運(yùn)行狀況下，流過電阻器的僅僅是電壓互感器的小的一次側(cè)電流，并且他們引起的電壓降落是可忽略的。</p><p><b>　　電流互感器</b></p

63、><p>　　電流互感器與電流表、功率表、功率因數(shù)表、電能表、補(bǔ)償裝置、保護(hù)和調(diào)節(jié)繼電器以及斷路器的跳閘線圈一起使用。一個電流互感器可在不超過其設(shè)計和補(bǔ)償值的范圍內(nèi)運(yùn)行。</p><p>　　電流互感器串聯(lián)于電路，并且在二次側(cè)連接儀表數(shù)量是固定的。線電流的增加或減小需要二次側(cè)電壓降落相應(yīng)的上升或下降，從而強(qiáng)制二次側(cè)電流流過表計負(fù)荷的阻抗。因此，產(chǎn)生這個電壓的鐵心中的磁通也將隨著一次側(cè)電流上升或

64、下降。</p><p>　　連接與電流互感器二次側(cè)電路的儀表是串聯(lián)接入的，以便二次側(cè)電流流過每一個儀表。隨著儀表的增加，就需要較高的電壓來強(qiáng)制電流流過這些儀表。這要求在鐵芯中具有較大磁場密度。一個較高的磁場密度將增大鐵芯損耗和勵磁電流，因此造成變比誤差和相角誤差增大。因此，為了保證一定的精確度，需要對每一個電流互感器所允許帶的儀表數(shù)設(shè)置一個極限。</p><p>　　一次側(cè)負(fù)載運(yùn)行時，電流

65、互感器的二次側(cè)電流不允許開路。如果必須要斷開儀表的話，應(yīng)首先將二次側(cè)斷路。如果二次側(cè)電路開路的話，在端子之間將產(chǎn)生電位差，這對于任何接近或接觸表計和表頭的人員都將是危險的。引起這個高電位差的原因時：當(dāng)二次側(cè)電路開路時，所有的一次側(cè)安匝都有效的用于產(chǎn)生鐵芯的磁通，而正常中只有總安匝中的小部分用于產(chǎn)生鐵芯磁通。事實上，而磁側(cè)電壓的波形上升達(dá)到波峰并產(chǎn)生最大值，危險被放大。在這種情況下所產(chǎn)生的大磁通還會永久性的改變磁狀況和鐵芯，從而損害互感器

66、的精確度。</p><p><b>　　避雷器</b></p><p>　　保護(hù)輸電設(shè)備的一個方法就是使用避雷器，用于這個目的的避雷器有兩種類型：有效間隙（碳化硅）避雷器和無間隙（氧化鋅）金屬氧化物避雷器。</p><p><b>　　碳化硅避雷器</b></p><p>　　有效間隙避雷器的兩個主

67、要部分是火花間隙和非線性電阻。早期的一種設(shè)計是平板間隙的避雷器，今天在一些中壓供電網(wǎng)中還仍然得到使用，而在高壓電網(wǎng)中，特別是在超高壓電網(wǎng)中（300~750kV），通常更普遍使用的是磁吹火花間隙的避雷器。它主要包括三個部分：火花間隙、放電電阻和一個能監(jiān)測通過火花間隙的電壓分布的分級系統(tǒng)。</p><p><b>　　氧化鋅避雷器</b></p><p>　　這種避雷器的

68、材料是被均勻混合，形成晶粒，經(jīng)過特殊過程在溫度1100~1350℃時燒結(jié)。使用氧化鋅材料的無間隙避雷器的特性是：隨著電壓增大其電阻值迅速減小。為了保持系統(tǒng)絕緣受到的應(yīng)力盡可能的小，一個好的過電壓保護(hù)系統(tǒng)或者一個避雷器應(yīng)該滿足下列要求：</p><p>　　(1)在它的運(yùn)行壽命中，即使在污染的情況下，或在電網(wǎng)可能出現(xiàn)的大能量的重復(fù)放電后，它必須能承受系統(tǒng)的正常的相對地電壓；</p><p>

69、　　(2)它必須能承受由姐弟故障和其他的系統(tǒng)過渡狀態(tài)造成的短時過電壓而不被破壞，并且這些過電壓對大地放電不會導(dǎo)致接地故障；</p><p>　　(3)能斷開續(xù)流電流；</p><p>　　(4)它的能量吸收能力必須滿足這種情況，即在最嚴(yán)重的操作過電壓和短時過電壓下，其部件的溫度也不能升高到散熱允許的設(shè)定值；</p><p>　　(5)它必須維持盡可能低的保護(hù)水平。&