變(bian)(bian)壓(ya)器的(de)(de)過(guo)負荷運(yun)行(xing)(xing),是指變(bian)(bian)壓(ya)器在運(yun)行(xing)(xing)時(shi)傳(chuan)輸(shu)(shu)的(de)(de)容(rong)量超(chao)過(guo)了(le)變(bian)(bian)壓(ya)器的(de)(de)額(e)(e)定容(rong)量.三相變(bian)(bian)壓(ya)器的(de)(de)額(e)(e)定容(rong)量為SN=〖KF(〗3〖KF)〗I-NU-N,而運(yun)行(xing)(xing)中記錄的(de)(de)是變(bian)(bian)壓(ya)器的(de)(de)有功輸(shu)(shu)出和無(wu)功輸(shu)(shu)出,故需會換算(suan).

當S>S-N時(shi),則(ze)變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)過(guo)負(fu)荷(he)運(yun)行(xing)(xing).變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)過(guo)負(fu)荷(he)一定(ding)是(shi)工作電(dian)流超過(guo)額定(ding)電(dian)流,這時(shi)變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)的(de)負(fu)載損耗急劇增加,勢必造成變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)溫度升高,而變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)溫度升高,對(dui)(dui)變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)的(de)運(yun)行(xing)(xing)及壽命危害大(da).因此,必須(xu)對(dui)(dui)變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)的(de)過(guo)負(fu)荷(he)運(yun)行(xing)(xing)加以限制(zhi).這種限制(zhi)實際(ji)上是(shi)對(dui)(dui)變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)繞(rao)組熱點溫度的(de)控制(zhi).從(cong)這個基(ji)點出(chu)發,變(bian)(bian)(bian)壓(ya)(ya)(ya)(ya)(ya)器(qi)(qi)(qi)(qi)過(guo)負(fu)荷(he)可(ke)以分為以下三種情況.

1、允許過負荷

變壓(ya)(ya)(ya)器雖然過(guo)(guo)負荷,但過(guo)(guo)負荷程度不(bu)大(da),且在過(guo)(guo)負荷前,變壓(ya)(ya)(ya)器負荷較(jiao)輕,變壓(ya)(ya)(ya)器頂部油(you)溫并不(bu)高,變壓(ya)(ya)(ya)器繞組的熱點(dian)溫度不(bu)會達(da)到有危害的程度,這(zhe)種(zhong)過(guo)(guo)負荷是(shi)變壓(ya)(ya)(ya)器容許的.

2、限制過負荷

變(bian)壓(ya)(ya)器的(de)(de)過負(fu)荷程(cheng)度(du)較大,使頂部油溫(wen)升高,變(bian)壓(ya)(ya)器繞組的(de)(de)熱(re)點(dian)溫(wen)度(du)可能達(da)到有害的(de)(de)程(cheng)度(du),但還未達(da)到危險的(de)(de)程(cheng)度(du),這時變(bian)壓(ya)(ya)器雖能繼續(xu)運行,但會(hui)使絕緣(yuan)強(qiang)度(du)下降威脅(xie)變(bian)壓(ya)(ya)器的(de)(de)安全,影響變(bian)壓(ya)(ya)器的(de)(de)壽命.這種過負(fu)荷是(shi)必須(xu)加以限制(zhi)的(de)(de).

3、禁止過負荷

變(bian)壓器(qi)(qi)過負荷(he)程度(du)較(jiao)大(da),時間較(jiao)長,使變(bian)壓器(qi)(qi)頂部油(you)溫已(yi)超(chao)過允(yun)許值,變(bian)壓器(qi)(qi)繞(rao)組的熱點溫度(du)已(yi)達到危險(xian)程度(du).這時變(bian)壓器(qi)(qi)若(ruo)繼續運行,熱點周(zhou)圍的絕緣(yuan)油(you)會分(fen)解產(chan)生氣泡(pao),絕緣(yuan)強(qiang)度(du)嚴重下降,可能會導致變(bian)壓器(qi)(qi)的重大(da)故障,這種過負荷(he)是必須禁止的.

變(bian)壓器在(zai)過負荷運(yun)行時,應(ying)特(te)別注意(yi)以下(xia)幾點:

(1)密(mi)切監視(shi)變(bian)壓器(qi)繞組溫度(du)和(he)頂部油溫.

(2)起動變壓(ya)器(qi)的全部冷卻裝置,在冷卻裝置存(cun)在缺(que)陷(xian)或(huo)冷卻效率達(da)不到(dao)要求時,應禁止變壓(ya)器(qi)過負荷(he)運(yun)行.

(3)對(dui)帶有有載調壓裝置的變壓器,在過負(fu)荷程度較大時,應盡量避(bi)免用有載調壓裝置調節分(fen)接頭.

(4)主(zhu)變可(ke)以在正常(chang)(chang)過負(fu)(fu)荷(he)(he)(he)(he)和(he)事故過負(fu)(fu)荷(he)(he)(he)(he)情況下運(yun)行.正常(chang)(chang)過負(fu)(fu)荷(he)(he)(he)(he)其允許值應根據(ju)主(zhu)變的負(fu)(fu)荷(he)(he)(he)(he)曲線,冷卻介質(zhi)以及過負(fu)(fu)荷(he)(he)(he)(he)前主(zhu)變所帶的負(fu)(fu)荷(he)(he)(he)(he)來確定.事故過負(fu)(fu)荷(he)(he)(he)(he)和(he)正常(chang)(chang)過負(fu)(fu)荷(he)(he)(he)(he)的運(yun)行必須在主(zhu)變無(wu)異常(chang)(chang)現象情況下運(yun)行.如主(zhu)變存在冷卻器損壞(huai),嚴重(zhong)滲漏油,本體保護有嚴重(zhong)缺陷(xian)等(deng)情況下,則不允許過負(fu)(fu)荷(he)(he)(he)(he)運(yun)行.

GB/T 15164-94《油浸式電(dian)力變(bian)(bian)壓(ya)器(qi)(qi)(qi)負(fu)載導(dao)則》中規定按GB1094設計的(de)變(bian)(bian)壓(ya)器(qi)(qi)(qi),在額定負(fu)載和正常環境(jing)溫(wen)(wen)度(du)(20°C)下(xia)(xia)(xia),其(qi)熱(re)(re)點(dian)溫(wen)(wen)度(du)的(de)基準(zhun)值為(wei)98°C,在此溫(wen)(wen)度(du)下(xia)(xia)(xia)的(de)相對老(lao)化率(lv)(lv)為(wei)1,即在此條(tiao)件下(xia)(xia)(xia),變(bian)(bian)壓(ya)器(qi)(qi)(qi)消(xiao)耗正常壽命(ming).熱(re)(re)點(dian)溫(wen)(wen)度(du)每增加(jia)6K,老(lao)化率(lv)(lv)增加(jia)1倍.根據(ju)變(bian)(bian)壓(ya)器(qi)(qi)(qi)出廠溫(wen)(wen)升試驗(yan),折算(suan)到20°C下(xia)(xia)(xia)的(de)熱(re)(re)點(dian),溫(wen)(wen)度(du)均比(bi)98°C小得多(相差近20°C),因此實際(ji)上變(bian)(bian)壓(ya)器(qi)(qi)(qi)均留(liu)有較大的(de)溫(wen)(wen)升裕度(du).因為(wei)隨著變(bian)(bian)壓(ya)器(qi)(qi)(qi)投入運行時(shi)間的(de)增加(jia),其(qi)冷卻(que)系統的(de)熱(re)(re)效率(lv)(lv)會因散熱(re)(re)器(qi)(qi)(qi)的(de)臟污(wu)、油泵效率(lv)(lv)下(xia)(xia)(xia)降(jiang)等(deng)原因而比(bi)出廠時(shi)下(xia)(xia)(xia)降(jiang),實際(ji)溫(wen)(wen)升可能(neng)要比(bi)計算(suan)的(de)偏高(gao).當(dang)然,如制(zhi)造(zao)(zao)廠已提(ti)供(gong)了明確的(de)變(bian)(bian)壓(ya)器(qi)(qi)(qi)過負(fu)荷能(neng)力表(biao),應按制(zhi)造(zao)(zao)廠提(ti)供(gong)的(de)數(shu)據(ju)執行.