論電網規(guī)劃中無功功率補償 中英文(3000).doc

1、論電網中無功功率補償許多電設備均是根據電磁感應原理工作的，如配電變壓器、電動機等，它們都是建立交變磁場才能進行能量的轉換和傳遞。為建立交變磁場和感應磁通而需要的電功率成為無功功率。因此，所謂的“無功”并不是“無用”的電功率。只不過它的功率并不轉化為機械能、熱能而已；因此在供電系統(tǒng)中除了需要有功電源外，還需要無功電源，兩者缺一不可。在功率三角形中，有功功率p與視在功率s的比值，稱為功率因數(shù)cos。其計算公式為：cos=p/s=p/（p2+q2）1/2在電力網的運行中，功率因數(shù)反映了電源輸出的視在功率被有效利用的程度，我們希望的是功率因數(shù)越大越好。這樣電路中的無功功率可以降到最小，視在功率將大部分

2、用來供給有功功率，從而提高電能輸送的功率。1、 影響功率因數(shù)的主要因素（1） 大量的電感性設備，如異步電動機、感應電驢、交流電焊機等設備是無功功率的主要消耗者。據有關的統(tǒng)計，在工礦企業(yè)所消耗的全部無功功率中，異步電動機的無功消耗占了60%70%，所以要改善異步電動機的功率因數(shù)就要防止電動機的空載運行并盡可能提高負載率。（2） 變壓器消耗的無功功率一般約為其額定容量的10%15%，它的空載無功功率約為滿載時的1/3，因而，為了改善電力系統(tǒng)和企業(yè)的功率因數(shù)，變壓器不應空載運行或長期處于低負載運行狀態(tài)。（3） 供電電壓超過超出規(guī)定范圍會對功率因數(shù)造成很大的影響當供電電壓高于額定值的10%時，由于磁路

3、飽和的影響，無功功率將增長得很快，據有關資料統(tǒng)計，當供電電壓為額定值的110%時，一般無功將增加35%左右。當供電電壓低于額定值時，無功功率也相應減少而使它們的功率因數(shù)有所提高，但供電電壓降低會影響電氣設備的正常工作，所以，應當采取措施使電力系統(tǒng)的供電電壓盡可能保持穩(wěn)定2 無功補償?shù)囊话惴椒o功補償通常采用的方法主要有3種：低壓個別補償，低壓集中補償，高壓集中補償，下面簡單介紹這三種補償方式的適用范圍及使用該補償方式的優(yōu)缺點。（1） 低壓個別補償：低壓個別補償就是根據個別用電設備對無功的需要量將單臺或多臺低壓電容器組分散地與用電設備并接，它與用電設備公用一套斷路器，通過控制、保護裝置與電機，同

4、時投切，隨機補償適用于補償個別大容量且連接運行（如大中型異步電動機）的無功損耗，以補勵磁無功為主，低壓個別補償?shù)膬?yōu)點是，用電設備運行時。無功補償投入，用電設備停運時，補償設備也退出，因此不會造成無功倒送，具有投資少、占位小、安裝容易、配置方便靈活、維護簡單、事故率低等優(yōu)點。（2） 低壓集中補償：低壓集中補償是指將低壓電容器通過低壓開關接在配電變壓器低壓母線側，以無功補償投切裝置作為控制保護裝置，根據低壓母線上的無功負荷而直接控制電容器的投切，電容器的投切是整組進行，做不到平滑的調節(jié)。低壓補償?shù)膬?yōu)點：接線簡單、運行維護工作量小，使無功就地平衡，從而提高配變利用率，降低網損，具有較高的經濟性，是目

5、前無功補償中常用的手段之一。（3） 高壓集中補償：高壓集中補償是指將并聯(lián)電容器組直接裝在變電所的610kv高壓母線上的補償方式適用于用戶遠離變電所或在供電線路的末端，用戶本身又有一定的高壓負荷，可以減少對電力系統(tǒng)無功的消耗并可以起到一定的補償作用；不差個裝置根據負荷的大小自動投切，從而合理地提高了用戶的功率因數(shù)，避免功率因數(shù)降低導致電費的增加。同時便于運行維護，補償效益高。3 采取適當措施，設法提高系統(tǒng)自然功率因數(shù)提高自然功率因數(shù)是不需要任何補償設備投資，僅采取各種管理上或者技術上的手段來減少各種用電設備所消耗的無功功率，這是一種最經濟的提高功率因數(shù)的方法。（1） 合理使用電動機；（2） 提高

6、異步電動機的檢修質量；（3） 采用同步電動機：同步電動機啊消耗的有功功率取決于電動機上所帶機械負荷的大小，而無功功率取決于轉子中的勵磁電流大小，在欠勵狀態(tài)時，定子繞組向電網“吸取”無功，在過勵狀態(tài)時，定子繞組向電網“送出”無功。因此。對于恒速長期運行的大型機構設備可以采取同步電動機作為動力。異步電動機同步運行就是將異步電動機三相轉子繞組適當連接并通入直流勵磁電流，使其呈同步電動機運行，這就是“異步電動機同步化”。（4） 合理選擇配變容量，改善配變的運行方式：對負載率比較低的配變，一般采取“撤、換、并、?！钡确椒?，使其負載率提高到最佳值，從而改善電網的自然功率因數(shù)。4 無功電源電力系統(tǒng)的無功電源

7、除了同步電動機外還有靜電電容器、靜止無功補償器以及無功發(fā)生器，這4種裝置又稱為無功補償裝置，除電容器外，其余幾種既能吸收容性無功又能吸收感性無功。（1） 同步電機：同步電機中有發(fā)電機、電動機及調相機3種。 同步發(fā)電機同步發(fā)電機是唯一的有功電源，同時又是最基本的無功電源，當其在額定狀態(tài)發(fā)出無功功率：其中：q、s、p、是相對應的無功功率、視在功率、有功功率和功率因數(shù)。發(fā)電機正常運行是，以滯后功率因數(shù)運行為主，向系統(tǒng)提供無功，但必要時，也可以減小勵磁電流，使功率因數(shù)超前，即所謂的“進相運行”，以吸收系統(tǒng)多余的無功。 同步調相機：同步調相機是空載運行的同步電機，它能在欠勵或過勵的情況下向系統(tǒng)吸收或者供

8、出無功，裝有自勵裝置的同步電機能根據電壓平滑地調節(jié)輸入或輸出的無功功率，這是其優(yōu)點，但它的有功損耗大、運行維護復雜、響應速度慢，近來已逐漸退出電網運行。 并聯(lián)電容器：并聯(lián)電容器補償是目前使用最廣泛的一種無功電源，由于通過電容器的交變電流在相位上正好超前于電容器極板上的電壓，相反于電感中的滯后，有此可視為向電網“發(fā)”無功功率：其中：q、u、分別為無功功率、電壓、電容器容抗。并聯(lián)電容器本身功耗很小，裝設靈活，節(jié)省投資；由它向系統(tǒng)提供無功可以改善功率因數(shù)，減少由發(fā)電機提供的無功功率。 靜止無功補償器：靜止無功補償器是由晶閘管所控制投切電抗器和電容器組成，由于晶閘管對于控制信號反應極為迅速，而且通斷次

9、數(shù)也可以不受限制，當電壓變化靜止補償器能快速、平滑地調節(jié)，以滿足動態(tài)無功補償?shù)男枰瑫r還能做到分相補償；對于三相不平衡負荷及沖擊負荷有較強的適應性；但由于晶閘管控制對電抗器的投切過程中會產生高次諧波，為此需加裝專門的濾波器。 靜止無功發(fā)生器：它的主體是一個電壓源型逆變器，由可關斷晶閘管適當?shù)耐〝啵瑢㈦娙萆系闹绷麟妷恨D換成為與電力系統(tǒng)電壓同步的三相交流電壓，再通過電抗器并聯(lián)接入電網，適當控制逆變器的輸出電壓，就可以靈活地改變其運行工況，使其處于容性、感性或零負荷狀態(tài)。與靜止無功補償器相比，靜止無功發(fā)生器相應速度更快，諧波電流更少，而且在系統(tǒng)電壓較低時仍能向系統(tǒng)注入較大的無功。5結束語本文集中探

10、討了功率因數(shù)對廣大供電企業(yè)的影響以及提高功率因數(shù)所帶來的經濟效益和社會效益，介紹了影響功率因數(shù)的主要因數(shù)和提高功率因數(shù)的幾種方法，還討論了目前所通用的幾種無功電源及其特點，這對供電企業(yè)是十分有益的。theory of grid planning of reactive power compensation many electric equipment are according to the principle of electromagnetic induction and work, such as distribution transformer, motor, etc， they a

11、re built to alternating magnetic field of energy conversion and transfer.to establish alternating magnetic field and inductive magnetic flux and need to be reactive power and power. therefore, the so-called "reactive" and not "useless" theelectrohydraulic power. but it is not con

12、verted into mechanical energy, power heat just; so in power supply system of meritorious power besides need outside, still need to reactive power, both are necessary.1, the main factors of influence power factor(1) a lot of inductive devices, such as induction motor, ac welders, induction, such equi

13、pment is reactive power consumption is the main. according to the statistics, consumed in industrial and mining enterprises in all the reactive power, asynchronous motor of reactive power consumption accounted for 60% to 70%, so want to improve the power factor of asynchronous motor to prevent motor

14、 racing operation and maximize load rate.(2) the consumption of reactive power transformer for its nominal capacity is typically about 10% 15%, its non-load reactive power for about one-third of full, therefore, in order to improve the power system and power factor of enterprise no-load transformer

15、should not running or the long-term at low load operation.(3) power supply voltage exceed within the prescribed scope of power factor will have a big impactwhen the power supply voltage when the 10% higher than the ratings, due to the influence of magnetic saturation, reactive power will grow fast,

16、according to the statistics, when the power supply voltage of ratings, generally for 110% of the reactive power will increase about 35%. when the power supply voltage is lower than ratings, reactive power when they drop accordingly improve the power factor, but the power supply voltage lowering will

17、 affect the normal work of the electrical equipment, so, shall adopt measures to prevent power system voltage supply as remained stable2 the general method of reactive power compensationreactive compensation the usual method basically has 3 kinds: low voltage individual compensation concentrated com

18、pensation, high pressure, low pressure concentrated compensation, the following simple introduce this three kinds of compensation methods applicable scope and the advantages and disadvantages of using this method for compensation.(1) low-pressure individual compensation:low voltage individual compen

19、sation is according to the individual of reactive power equipment will be a single stage because of the low voltage capacitor set or more sets with electrical equipment and scattered with electrical equipment pick, it public a set of circuit breaker, through the control and protection device and mot

20、or, meanwhile shots, random compensation applicable to cut large capacity and compensation individual connect operation, such as large and medium-sized asynchronous motor) reactive loss to recover the excitation reactive power is given priority to, the advantages of low voltage individual compensati

21、on, electricity equipment in operation. reactive compensation investment, electrical equipment, compensation equipment and action, and therefore won't cause from reactive delivers the placeholder, has less investment, small, easy installation, configuration is convenient and flexible, simple mai

22、ntenance and accidents etc.(2) low-pressure concentrated compensation:low voltage concentrated compensation refers to low voltage capacitor through the low pressure switch will pick up in distribution transformer, low-pressure busbar side reactive power compensation threw cutting device as control p

23、rotection device, according to the low-pressure busbar reactive load and direct control capacitors, capacitors cast cut, cut the cast is less than smooth adjustment. do low voltage compensation advantages: wiring is simple, operation and maintenance, small amount of reactive power balance, so as to

24、improve the in situ with variable utilization, decrease network loss, high efficiency, is currently reactive compensation in one of the common method.(3) high-pressure concentrated compensation:high-pressure concentrated compensation refers to will shunt capacitors installed directly in the substati

25、on of 6 to consumers 10kv high-pressure busbar compensation way suitable for user from substation or the end of the power supply line, user itself also has the certain high-voltage, can reduce on power system reactive power consumption and can play a certain role; the compensation not bad, according

26、 to the size of a device to load auto-switching, thus reasonable improve users' power factor, avoid power factor caused by the increase of electricity. also facilitate operation and maintenance, high compensation benefits.3 take appropriate measures to try to improve the system of natural power

27、factorimprove natural power factor is not to need any compensation equipment investment, only take various management or technical means to reduce power consumption equipment of reactive power, this is a kind of the most economic improving power factor method.(1) reasonably using the motor;(2) impro

28、ve the maintenance quality of asynchronous motor;(3) using synchronous motor: synchronous motor ah the active power consumed by motor with depends on the size of the mechanical load, and reactive power depends on the excitation currents, rotor shunt state in owe to the power grid, stator winding &qu

29、ot;drain" reactive, stator winding shunt state, to the power grid "send" reactive. therefore. for constant speed long-term operation of large institutions equipment can take synchronous motor as power.asynchronous motor synchronization operation is three-phase asynchronous motor rotor

30、 windings appropriate link and access to dc exciter current, to assume the synchronous motor running, it is a "asynchronous motor synchronization".（5） (4) rational choice, improve with variable volume with the operation mode: to change the load factor lower with variable, generally take &q

31、uot;withdraw, change, and methods, stop", make its load rate increased to best value, thereby improve the natural power factor.four reactive powerpower system reactive power except for synchronous motor and electrostatic capacitor, static outside of reactive power compensator and reactive gener

32、ator, the four devices called reactive compensation devices, except capacitor outside, the rest several can absorb capacitive reactive and can absorb perceptual reactive.(1) synchronous motor:synchronous motor are generators, motors and in three adjustable camera.(1) the synchronous generatorssynchr

33、onous generator is the only active power, and is the most basic reactive power, when its rated condition in issued reactive power:among them: q, s, p, phi is corresponding reactive power, shizai power, active power and power factor.generators in the normal operation of power factor is lagging, mainl

34、y to run, system to provide the reactive power, but when necessary, also can reduce excitation current, make the power factor ahead, the so-called "under-excitation operation", to absorb system redundant reactive.(1) the synchronous adjustable cameras:synchronous adjustable camera is no-lo

35、ad running synchronous motor, it can shunt or excitation in owe to the system under the condition of the absorption of reactive power, or for the synchronous motor with motivated device can smoothly according to the voltage regulation input or output of reactive power, this is its advantages, but it

36、s active loss is big, operation &maintenance complex, slow response, recently has gradually exit the power network operation.(2) the parallel capacitor:parallel capacitor compensation is the most widely used a reactive power, because through the capacitors in alternating current in advance exact

37、ly in the phase of voltage capacitor plates, as opposed to the lag, there is the inductance can be regarded as to the grid "hair" reactive power:among them: q and u, respectively, reactive power, voltage, capacitor rongkang.parallel capacitor itself power consumption is small, furnish flex

38、ible, save investment; by its system to provide reactive to can improve power factor, reduce by generators provide reactive power. (1) the static reactive power compensator:static reactive power compensator is cast by zhaguansuo control wafer cut reactor and capacitors because of thyristor reaction to control signal is rapidly, but hige number are also can not restricted, when voltage changing static compensator can fast and smooth to adjust to meet the needs of dynamic reactive compensation, also can achieve points phase compensati