你知道電容器回路串聯電抗器的意義在哪嗎？

       電容器在感性負載處并聯連接也就是所謂的串聯電抗器。這是電網中最常用的(de)(de)(de)(de)無功補償方法。它也(ye)是提(ti)高(gao)(gao)功率(lv)因數，改善電壓質量(liang)(liang)和能量(liang)(liang)損(sun)失的(de)(de)(de)(de)有效措施。為了滿足(zu)電網和電氣設(she)備(bei)的(de)(de)(de)(de)電壓質量(liang)(liang)要求，根據電抗負載的(de)(de)(de)(de)變(bian)化切換(huan)適量(liang)(liang)的(de)(de)(de)(de)電容(rong)。但是，當(dang)國有企業投入(ru)運營時，它們將(jiang)產生(sheng)大規(gui)模，高(gao)(gao)頻率(lv)的(de)(de)(de)(de)收盤(pan)激增。如果電容(rong)器(qi)連接到(dao)電網以存(cun)儲諧波(bo)污染，由于(yu)電容(rong)器(qi)的(de)(de)(de)(de)電容(rong)阻抗特性，諧波(bo)電流(liu)將(jiang)被(bei)放(fang)大。危險的(de)(de)(de)(de)過(guo)電流(liu)會對電氣設(she)備(bei)產生(sheng)不利影響，嚴重時會對設(she)備(bei)造成(cheng)損(sun)壞。

為了避免諧波對補償裝置的影響，電容器回路采用串聯電抗器，既不影響電(dian)(dian)容(rong)器的無功補償，又能抑制(zhi)高次(ci)諧波。因(yin)此(ci)，補償電(dian)(dian)容(rong)電(dian)(dian)路中的串(chuan)聯電(dian)(dian)抗器具有(you)抑制(zhi)高次(ci)諧波和限制(zhi)合閘涌流的作用(yong)。

然而，操(cao)作實踐表明，在電(dian)容器回(hui)路(lu)(lu)的串聯電(dian)抗(kang)器之后，當無功(gong)功(gong)率補償裝置投入運行時可(ke)能(neng)會發生過電(dian)壓，并且(qie)可(ke)以減(jian)小(xiao)電(dian)容器的端子電(dian)壓和使(shi)用壽(shou)命。分析了(le)串聯電(dian)抗(kang)器在電(dian)容器回(hui)路(lu)(lu)中的優缺點。

1電(dian)容器(qi)環路串聯電(dian)抗器(qi)的(de)優(you)點(dian)

（1）限制合閘涌流

無功補償電(dian)(dian)容(rong)(rong)器投(tou)切時，往往會發生(sheng)沖擊合閘涌(yong)流(liu)。這(zhe)是(shi)因為電(dian)(dian)容(rong)(rong)器第一次不充電(dian)(dian)，流(liu)入(ru)電(dian)(dian)容(rong)(rong)器的(de)(de)電(dian)(dian)流(liu)僅受(shou)電(dian)(dian)路(lu)阻(zu)抗的(de)(de)限制(zhi)。由于電(dian)(dian)路(lu)接近短路(lu)狀態，電(dian)(dian)路(lu)阻(zu)抗很小，會產生(sheng)很大的(de)(de)浪涌(yong)電(dian)(dian)流(liu)。

隨著(zhu)總(zong)線短(duan)路容器的(de)增加(jia)或電抗(kang)(kang)器電感對電容電容電抗(kang)(kang)的(de)百分比的(de)增加(jia)，K值大大降低，串聯電抗(kang)(kang)器可限制串聯電抗(kang)(kang)器后的(de)合閘涌流。

（2）抑制高次諧波

當補償電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)接入點處的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)網中存(cun)在諧(xie)(xie)波(bo)(bo)(bo)時，電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器(qi)對(dui)(dui)n次(ci)諧(xie)(xie)波(bo)(bo)(bo)的(de)(de)容(rong)抗(kang)降低到(dao)Xc / n，并且系統電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)對(dui)(dui)n次(ci)諧(xie)(xie)波(bo)(bo)(bo)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)升高到(dao)nXs。當網格中存(cun)在n個諧(xie)(xie)波(bo)(bo)(bo)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)時，如果(guo)nXs = Xc / n，則發生(sheng)(sheng)n次(ci)諧(xie)(xie)波(bo)(bo)(bo)共振現象。在疊(die)加(jia)n次(ci)諧(xie)(xie)波(bo)(bo)(bo)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)和(he)基波(bo)(bo)(bo)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)之(zhi)后，流(liu)過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器(qi)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)突然增(zeng)加(jia)，其(qi)過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)將危及電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器(qi)的(de)(de)安(an)全(quan)性(xing)。此時，由系統阻抗(kang)上的(de)(de)諧(xie)(xie)波(bo)(bo)(bo)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)產生(sheng)(sheng)的(de)(de)諧(xie)(xie)波(bo)(bo)(bo)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)與原始電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)疊(die)加(jia)，產生(sheng)(sheng)過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)，這將影響電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器(qi)的(de)(de)壽命。

對(dui)電容器(qi)回路(lu)中(zhong)的串聯電抗器(qi)進行補償后，可以有(you)效地避免諧(xie)振區，抑制(zhi)高(gao)次諧(xie)波。

當電網存(cun)在(zai)高次諧波(bo)時，當n>n0時，阻抗是感性的，對等效(xiao)網絡(luo)具有明顯的諧波(bo)抑制作用。

操作實踐表(biao)明(ming)，如果串聯電(dian)(dian)(dian)抗器的(de)主(zhu)要目的(de)是限制(zhi)浪(lang)涌電(dian)(dian)(dian)流(liu)，應(ying)(ying)選擇電(dian)(dian)(dian)容(rong)為0.2-2％的(de)電(dian)(dian)(dian)抗器;如果要抑制(zhi)高(gao)次諧波(bo)，應(ying)(ying)選擇電(dian)(dian)(dian)容(rong)為6％的(de)電(dian)(dian)(dian)抗器。電(dian)(dian)(dian)抗器應(ying)(ying)串聯在電(dian)(dian)(dian)容(rong)器組的(de)電(dian)(dian)(dian)源側，這樣可(ke)以更(geng)好地抑制(zhi)諧波(bo)效應(ying)(ying)。

2系列反應器的缺點

（1）電容器接(jie)通和斷開時(shi)發(fa)生過電壓。

在(zai)并聯(lian)電(dian)(dian)(dian)容(rong)器(qi)組的(de)電(dian)(dian)(dian)路(lu)(lu)中串聯(lian)連接的(de)電(dian)(dian)(dian)抗器(qi)，尤其是線性電(dian)(dian)(dian)抗器(qi)或高質(zhi)量電(dian)(dian)(dian)抗器(qi)，在(zai)斷路(lu)(lu)器(qi)切換(huan)電(dian)(dian)(dian)容(rong)器(qi)時(shi)產(chan)生過電(dian)(dian)(dian)壓，因為斷路(lu)(lu)器(qi)在(zai)閉合時(shi)反彈并分開。在(zai)門處重新(xin)點火(huo)將(jiang)增加過電(dian)(dian)(dian)壓的(de)概率和倍數(shu)。因此，切斷電(dian)(dian)(dian)容(rong)器(qi)的(de)斷路(lu)(lu)器(qi)應選擇(ze)性能高，無(wu)浪(lang)涌電(dian)(dian)(dian)流且無(wu)需重新(xin)點火(huo)的(de)開關(guan)，以避免在(zai)運行過程中產(chan)生過電(dian)(dian)(dian)壓。

（2）電(dian)(dian)容器(qi)端電(dian)(dian)壓升高

電(dian)(dian)(dian)容器串聯(lian)電(dian)(dian)(dian)抗(kang)器運(yun)行(xing)后，電(dian)(dian)(dian)容器端電(dian)(dian)(dian)壓高(gao)于母線電(dian)(dian)(dian)壓，電(dian)(dian)(dian)容器端電(dian)(dian)(dian)壓由下(xia)列公式確定(ding)。

Uc=Ue＆middot;Xc/（Xc-XL）

其中Ue是電(dian)容(rong)器總(zong)線的額定電(dian)壓。

當反應器(qi)XL大于電(dian)容(rong)器(qi)XC時，電(dian)容(rong)器(qi)端電(dian)壓升高。如果XL大于電(dian)容(rong)器(qi)XC，則電(dian)容(rong)器(qi)的(de)端電(dian)壓升高更(geng)多。例如，當xl=6%xc時，電(dian)容(rong)器(qi)端電(dian)壓降增加6.4%，當xl=13%xc時，電(dian)容(rong)器(qi)端電(dian)壓降增加11.5%。

另外，對于具有非接地中性點的電容器組，由于三相的實際電容不能完全平衡，使得某些電容器端面的電壓明顯增加。串聯電抗器后(hou)三相電容(rong)的不平(ping)衡現象(xiang)更加(jia)(jia)嚴重.結果(guo)表明，電容(rong)端電壓(ya)的增加(jia)(jia)值大于三相電容(rong)平(ping)衡值。

增加電(dian)容(rong)器(qi)端子的電(dian)壓將(jiang)危(wei)及安全操作(zuo)，影響使用(yong)壽命，甚至引起鼓脹和爆炸等事故(gu)。為此，電(dian)容(rong)器(qi)電(dian)路中的串聯電(dian)抗器(qi)還應考慮三相電(dian)容(rong)器(qi)的平衡，以避免較大的端電(dian)壓上升。