為什(shen)么變壓器投(tou)運前(qian)進行5次(ci)沖擊試驗？

新變壓(ya)器(qi)或大修后的變壓(ya)器(qi)在正式投運(yun)前要做沖擊試驗的原(yuan)因(yin)如(ru)下：

(1)檢查變壓(ya)(ya)(ya)(ya)器(qi)及(ji)其回路的絕(jue)緣是否(fou)存(cun)在弱點(dian)或(huo)缺陷。拉(la)開空載(zai)變壓(ya)(ya)(ya)(ya)器(qi)時，有可能(neng)(neng)產生操(cao)作(zuo)過(guo)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)。在電(dian)(dian)(dian)力系統中(zhong)性(xing)點(dian)不(bu)接(jie)(jie)地或(huo)經消弧線圈接(jie)(jie)地時，過(guo)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)幅值(zhi)可達(da)4—4.5倍相電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)；在中(zhong)性(xing)點(dian)直接(jie)(jie)接(jie)(jie)地時，過(guo)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)幅值(zhi)可達(da)3倍相電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)。為了檢驗(yan)變壓(ya)(ya)(ya)(ya)器(qi)絕(jue)緣強度能(neng)(neng)否(fou)承(cheng)受全(quan)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)或(huo)操(cao)作(zuo)過(guo)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)的作(zuo)用，故在變壓(ya)(ya)(ya)(ya)器(qi)投入(ru)運(yun)行前，需(xu)做空載(zai)全(quan)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)沖擊試(shi)驗(yan)。若變壓(ya)(ya)(ya)(ya)器(qi)及(ji)其回路有絕(jue)緣弱點(dian)，就會作(zuo)過(guo)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)擊穿而加以(yi)暴露。

(2)檢查甘肅變壓器差動(dong)(dong)保(bao)護(hu)是否(fou)誤動(dong)(dong)。帶電(dian)投入(ru)空載(zai)變(bian)壓(ya)(ya)器(qi)時，會產生勵(li)(li)磁(ci)涌流(liu)，其值可(ke)達6-8倍額(e)定電(dian)流(liu)。勵(li)(li)磁(ci)涌流(liu)開始衰(shuai)減(jian)較快，一般經0.5—1s即可(ke)減(jian)到0.25—0.5倍額(e)定電(dian)流(liu)，但全部(bu)衰(shuai)減(jian)完畢時間較長，中小(xiao)型(xing)變(bian)壓(ya)(ya)器(qi)約(yue)幾秒，大型(xing)變(bian)壓(ya)(ya)器(qi)可(ke)達10-20s，故勵(li)(li)磁(ci)涌流(liu)衰(shuai)減(jian)初期，往往使差動(dong)(dong)保(bao)護(hu)誤動(dong)(dong)，造成(cheng)變(bian)壓(ya)(ya)器(qi)不(bu)能投入(ru)。因此，空載(zai)沖擊合(he)閘時，在勵(li)(li)磁(ci)涌流(liu)作(zuo)(zuo)用下，可(ke)對差動(dong)(dong)保(bao)護(hu)的接(jie)線、特性、定值進行(xing)實(shi)際檢(jian)查(cha)，并作(zuo)(zuo)出(chu)保(bao)護(hu)可(ke)否(fou)投入(ru)的評價和結論(lun)。

(3)考核變壓器的機械強度。由于勵磁涌生很大的電動力，為了考核蘭州變壓器的機械強度(du)，需做空載沖擊試驗。

按照規程規定，全電壓空載沖擊試驗次數，新產品投入，應連續沖擊5次；大修后投入，應連續沖擊3次。每次沖擊間隔時間不少于5min，操作前應派人到現場對甘肅變壓器廠家進行監視(shi)，檢查變匝(za)器(qi)有無異狀，如有異常應(ying)立即停止操作。

第(di)一次(ci)沖(chong)(chong)擊后(hou)要(yao)持續運行10分鐘以上，后(hou)面沖(chong)(chong)擊要(yao)等待5分鐘以上再(zai)進行下一次(ci)沖(chong)(chong)擊。至于為什(shen)么設置成5次(ci)是規(gui)程規(gui)定(ding)的，具體估計是對機械強度、過電壓、勵磁(ci)涌(yong)流(liu)的綜合(he)考慮而得出的結(jie)論。