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變電(dian)站(zhan)10kV電(dian)容器組的配置

發布(bu)時間(jian):2020-04-21 11:15:00 來源:振航電氣(qi)科技有限公(gong)司(si)

引言

目(mu)前(qian),電力系(xi)統(tong)(tong)(tong)中(zhong)為了提高電壓質量,減少網絡損(sun)耗,普遍配置(zhi)(zhi)了無功補償裝置(zhi)(zhi),由(you)于電容器組容量可(ke)大可(ke)小(xiao)(xiao),即可(ke)集中(zhong)使用(yong),又可(ke)分散配置(zhi)(zhi),具有(you)較(jiao)(jiao)大的靈活性(xing),且價格較(jiao)(jiao)低,損(sun)耗較(jiao)(jiao)小(xiao)(xiao),維護方便(bian),故(gu)為目(mu)前(qian)系(xi)統(tong)(tong)(tong)中(zhong)使用(yong)最(zui)廣泛的無功電源之一。變電站設計(ji)中(zhong)一般(ban)將電容器組布置(zhi)(zhi)在10kV側(ce)。由(you)于10kV側(ce)配置(zhi)(zhi)電容器存在系(xi)統(tong)(tong)(tong)短路容量較(jiao)(jiao)小(xiao)(xiao)、分組數(shu)較(jiao)(jiao)多、易(yi)發生諧振(zhen)等問題,故(gu)如何合理選擇10kV電容器組就顯得(de)尤為重要。

1、電容器總容量的選擇

變(bian)電(dian)站安裝(zhuang)的"最(zui)(zui)大容(rong)性(xing)無(wu)功(gong)量"的選擇原則為:對(dui)于(yu)直接(jie)供電(dian)末端(duan)變(bian)電(dian)所,其最(zui)(zui)大容(rong)性(xing)無(wu)功(gong)量應等于(yu)裝(zhuang)置所在母線上的負荷按提高功(gong)率因(yin)數所需補償的最(zui)(zui)大容(rong)性(xing)無(wu)功(gong)量與主(zhu)變(bian)壓器所需補償的最(zui)(zui)大容(rong)性(xing)無(wu)功(gong)之和。即:

通過式(1)、(2)、(3)對變(bian)(bian)(bian)電站無功容(rong)量(liang)(liang)進行估(gu)算,負荷所需補償(chang)的最(zui)大容(rong)性無功量(liang)(liang)約為(wei)主變(bian)(bian)(bian)容(rong)量(liang)(liang)的5%~10%(按補償(chang)到功率因(yin)數0.96考慮),主變(bian)(bian)(bian)壓器所需補償(chang)的最(zui)大容(rong)性無功量(liang)(liang)14%~16%。

綜(zong)上所述,變(bian)電(dian)(dian)站的(de)容(rong)性無(wu)功(gong)補(bu)(bu)償(chang)以(yi)補(bu)(bu)償(chang)主變(bian)的(de)無(wu)功(gong)損(sun)耗為(wei)主,現(xian)變(bian)電(dian)(dian)站均按照主變(bian)容(rong)量(liang)來配置(zhi)(zhi)(zhi)電(dian)(dian)容(rong)器(qi)(qi)補(bu)(bu)償(chang)容(rong)量(liang)。根據《國(guo)家電(dian)(dian)網公(gong)司電(dian)(dian)力系統無(wu)功(gong)補(bu)(bu)償(chang)技術配置(zhi)(zhi)(zhi)原則》(以(yi)下(xia)簡稱配置(zhi)(zhi)(zhi)原則)要求(qiu),變(bian)電(dian)(dian)站可按照主變(bian)壓(ya)器(qi)(qi)容(rong)量(liang)的(de)20%-25%配置(zhi)(zhi)(zhi)容(rong)性無(wu)功(gong)補(bu)(bu)償(chang)裝(zhuang)置(zhi)(zhi)(zhi)。因此變(bian)電(dian)(dian)站的(de)電(dian)(dian)容(rong)器(qi)(qi)組(zu)(zu)總(zong)容(rong)量(liang)除(chu)個別情況(kuang)外,大(da)多數情況(kuang)應按照以(yi)上要求(qiu)配置(zhi)(zhi)(zhi),與電(dian)(dian)容(rong)器(qi)(qi)組(zu)(zu)的(de)電(dian)(dian)壓(ya)等級(ji)無(wu)關。

2、電容器分組容量的選擇

確定了電(dian)容(rong)器(qi)組總容(rong)量后,還需對(dui)電(dian)容(rong)器(qi)組分(fen)組容(rong)量進行選(xuan)擇。

(1)若分組容(rong)量過大,會(hui)引(yin)起(qi)投(tou)(tou)切(qie)時母線電壓(ya)波(bo)動(dong)增大、變電站投(tou)(tou)運初期負荷(he)變小,無(wu)法投(tou)(tou)入電容(rong)器進行無(wu)功補償等問題。

(2)若分組(zu)容量(liang)過小,會引起(qi)增加(jia)設備投資、減少(shao)變電(dian)站出現(xian)回(hui)路數、增大維護工作(zuo)量(liang)、增大變電(dian)站的(de)布置難度等問(wen)題。

因此電容(rong)器分(fen)組(zu)的總原(yuan)則應是:在滿足系統要求的前(qian)提下,盡量加大分(fen)組(zu)容(rong)量,減少組(zu)數。

2.1 電(dian)容(rong)器分(fen)組容(rong)量與(yu)母(mu)線電(dian)壓波動的研究

電容器在進行投切(qie)操作(zuo)時,將(jiang)引起母線電壓的變化,其變化幅度為:

從(cong)式(shi)(shi)(4)可以(yi)看出,母(mu)線電(dian)(dian)壓(ya)(ya)(ya)波動率與投切(qie)電(dian)(dian)容(rong)器(qi)(qi)的(de)(de)容(rong)量(liang)成正比,與母(mu)線三相短(duan)(duan)路容(rong)量(liang)成反比。《城(cheng)市電(dian)(dian)力(li)網規(gui)劃設計(ji)導則》中規(gui)定:變電(dian)(dian)站10kV側(ce)母(mu)線短(duan)(duan)路電(dian)(dian)流(liu)需控制在(zai)(zai)20kA以(yi)內, 10kV側(ce)極限(xian)短(duan)(duan)路容(rong)量(liang)為(wei)(wei)1.73210.520=363.7MVA,根據《配置原(yuan)則》要(yao)求,以(yi)投切(qie)最大單組補償設備(bei)引起(qi)的(de)(de)所在(zai)(zai)母(mu)線電(dian)(dian)壓(ya)(ya)(ya)的(de)(de)變動值不(bu)宜超過額定電(dian)(dian)壓(ya)(ya)(ya)的(de)(de)2.5%計(ji)算(suan)。10kV側(ce)單組電(dian)(dian)容(rong)器(qi)(qi)容(rong)量(liang)極限(xian)值為(wei)(wei)Qfz=363.72.5%=9.09Mvar。另外(wai),由于(yu)20kA為(wei)(wei)變電(dian)(dian)站在(zai)(zai)大方(fang)式(shi)(shi)下需保證的(de)(de)短(duan)(duan)路電(dian)(dian)流(liu),若(ruo)在(zai)(zai)小(xiao)方(fang)式(shi)(shi)下,則達不(bu)到20kA,相應的(de)(de)短(duan)(duan)路容(rong)量(liang)也要(yao)隨之減小(xiao)。

綜上所述,為保證投切電容(rong)器時(shi)母線電壓波(bo)動在2.5%以內,變電站(zhan)10kV電容(rong)器組(zu)(zu)的分組(zu)(zu)容(rong)量(liang)(liang)應通過計(ji)算確定(ding)。結合以往(wang)經(jing)驗,220kV變電站(zhan)分組(zu)(zu)容(rong)量(liang)(liang)不(bu)宜大于(yu)8Mvar,110kV變電站(zhan)不(bu)宜大于(yu)6Mvar。

2.2 電(dian)容(rong)器(qi)分組容(rong)量(liang)與諧波放大(da)的研究

投入并聯電(dian)(dian)容器(qi)(qi)裝(zhuang)(zhuang)置后,為防止其(qi)引起高次諧(xie)(xie)波(bo)(bo)電(dian)(dian)流放大和諧(xie)(xie)振(主要針對(dui)3、5、7次諧(xie)(xie)波(bo)(bo)而言),需(xu)在其(qi)回(hui)路(lu)裝(zhuang)(zhuang)設串聯電(dian)(dian)抗器(qi)(qi)。目前(qian)變電(dian)(dian)站一(yi)般(ban)在電(dian)(dian)容器(qi)(qi)組中串接(jie)5%的電(dian)(dian)抗器(qi)(qi),使電(dian)(dian)容器(qi)(qi)支路(lu)對(dui)5次及以上諧(xie)(xie)波(bo)(bo)均呈感性,可(ke)有效抑制(zhi)5次及以上諧(xie)(xie)波(bo)(bo)的危(wei)害(hai),但對(dui)3次諧(xie)(xie)波(bo)(bo)可(ke)能有電(dian)(dian)流放大作用(yong)。為抑制(zhi)3次諧(xie)(xie)波(bo)(bo)的危(wei)害(hai),可(ke)采取以下措施(shi):


3>>


1、電(dian)(dian)(dian)容(rong)器(qi)(qi)組串接12%~13%的(de)電(dian)(dian)(dian)抗(kang)器(qi)(qi),使電(dian)(dian)(dian)容(rong)器(qi)(qi)支路對3次及以上諧波均呈感性(xing)。但隨著串接電(dian)(dian)(dian)容(rong)器(qi)(qi)容(rong)量增大,會相應增加回路的(de)電(dian)(dian)(dian)能損耗,增大電(dian)(dian)(dian)容(rong)器(qi)(qi)端子的(de)運行電(dian)(dian)(dian)壓,縮短電(dian)(dian)(dian)容(rong)器(qi)(qi)使用(yong)壽命。因(yin)此從經濟性(xing)方面考(kao)慮,這一措(cuo)施僅(jin)在(zai)部分(fen)變電(dian)(dian)(dian)所(suo)使用(yong)。

2、恰當選(xuan)擇(ze)電(dian)(dian)容器(qi)(qi)分組(zu)容量,躲開3次(ci)(ci)諧(xie)波(bo)(bo)放大(da)(da)區。但此措施對(dui)3次(ci)(ci)諧(xie)波(bo)(bo)電(dian)(dian)流(liu)仍有放大(da)(da)作用,即系統內的3次(ci)(ci)諧(xie)波(bo)(bo)電(dian)(dian)流(liu),在投入電(dian)(dian)容器(qi)(qi)組(zu)后肯(ken)定要比(bi)投入前增大(da)(da)。在使用時,可根據電(dian)(dian)容器(qi)(qi)安(an)裝處3次(ci)(ci)諧(xie)波(bo)(bo)的污(wu)染程度,調(diao)整允許諧(xie)波(bo)(bo)電(dian)(dian)流(liu)的放大(da)(da)倍數,選(xuan)擇(ze)具體的分組(zu)容量。

根據式(shi)(4)及(ji)(5),當n=3、A=5%、K=2時,取最(zui)小運(yun)行方式(shi)下10kV短(duan)路(lu)容量為240MVA,最(zui)大(da)運(yun)行方式(shi)下短(duan)路(lu)容量為363.7MVA,則 應小于(yu)9.6Mvar或大(da)于(yu)33.2Mvar。即電容器投切時嚴禁投入9.6Mvar至(zhi)33.2Mvar之間容量,否則就會(hui)對其內流(liu)過(guo)的3次諧波產生不允(yun)許的放大(da)倍數,甚(shen)至(zhi)引起(qi)諧振,威脅設備安(an)全。

而(er)K值的選(xuan)擇(ze)是由電(dian)容(rong)器(qi)安裝處3次(ci)諧波的污染(ran)程度(du)(du)決定。若(ruo)污染(ran)程度(du)(du)較輕,則K值可(ke)選(xuan)的較大,相容(rong)短路容(rong)量(liang)下(xia),危險(xian)區就(jiu)較窄;若(ruo)污染(ran)程度(du)(du)較重,則K值可(ke)選(xuan)的較小,危險(xian)區就(jiu)較寬,相應的電(dian)容(rong)器(qi)分組(zu)容(rong)量(liang)選(xuan)擇(ze)就(jiu)需要謹慎。

2.3電容器分組容量(liang)選擇的(de)應用

以常見的50MVA主變壓(ya)器的110kV變電(dian)站為(wei)例(li),每臺(tai)主變壓(ya)器配置總(zong)容(rong)量(liang)10Mvar臺(tai)電(dian)容(rong)器,分(fen)組容(rong)量(liang)不超過5Mvar。10kV母線短路(lu)容(rong)量(liang)選擇極(ji)限(xian)最(zui)大值363.7MVA與最(zui)小值240MVA進(jin)行考慮。

3 結束語

隨(sui)著電(dian)(dian)(dian)網的(de)(de)(de)不斷(duan)發展,變(bian)電(dian)(dian)(dian)站單臺主變(bian)壓(ya)(ya)器(qi)(qi)(qi)容(rong)(rong)量不斷(duan)增大(da),按(an)照(zhao)主變(bian)壓(ya)(ya)器(qi)(qi)(qi)容(rong)(rong)量配置的(de)(de)(de)電(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)組(zu)總(zong)容(rong)(rong)量也在(zai)不斷(duan)增大(da)。若考慮減小(xiao)電(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)組(zu)總(zong)容(rong)(rong)量,則不能滿足系統(tong)電(dian)(dian)(dian)壓(ya)(ya)和功率(lv)因數(shu)方面的(de)(de)(de)要(yao)(yao)求。因此導致電(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)組(zu)總(zong)容(rong)(rong)量多在(zai)上安(an)全區。而(er)為控(kong)制電(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)投(tou)切時(shi)的(de)(de)(de)母線電(dian)(dian)(dian)壓(ya)(ya)波動,10kV單臺電(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)容(rong)(rong)量又(you)不宜過大(da),所以Qc值落入危險區的(de)(de)(de)概率(lv)大(da)。因此在(zai)電(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)分(fen)(fen)組(zu)時(shi),應(ying)具(ju)體情(qing)況具(ju)體分(fen)(fen)析,不要(yao)(yao)根(gen)據(ju)經驗盲目選(xuan)擇。另一方面還(huan)應(ying)該著眼于控(kong)制諧(xie)波源(yuan),盡量使(shi)其產生(sheng)的(de)(de)(de)諧(xie)波分(fen)(fen)量減少或在(zai)諧(xie)波源(yuan)的(de)(de)(de)外部采(cai)取措施,如裝(zhuang)設濾波器(qi)(qi)(qi)等吸收一部分(fen)(fen)諧(xie)波電(dian)(dian)(dian)流(liu),使(shi)允許的(de)(de)(de)K值增大(da),危險區域變(bian)窄,將更有利于電(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)的(de)(de)(de)分(fen)(fen)組(zu)選(xuan)擇。

參考文獻

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