變壓器的維護要點
1、允許溫度
變壓(ya)(ya)器運行(xing)時,它的線圈和(he)鐵芯產生銅損和(he)鐵損,這些損耗變為熱能(neng),使(shi)(shi) 變壓(ya)(ya)器的鐵芯和(he)線圈溫度(du)上升。若(ruo)溫度(du)長(chang)時間(jian)超過允(yun)許值會(hui)使(shi)(shi)絕緣漸(jian)(jian)漸(jian)(jian)失去機 械彈性而使(shi)(shi)絕緣老化。
變(bian)(bian)(bian)壓(ya)器(qi)運行時各部分的(de)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)是(shi)不(bu)相同的(de),線圈的(de)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)最(zui)高(gao),其(qi)次(ci)是(shi)鐵(tie)芯(xin)的(de)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du),絕(jue)緣油(you)(you)(you)(you)(you)(you)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)低于(yu)線圈和鐵(tie)芯(xin)的(de)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)。變(bian)(bian)(bian)壓(ya)器(qi)的(de)上部油(you)(you)(you)(you)(you)(you)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)高(gao)于(yu)下(xia)(xia)部油(you)(you)(you)(you)(you)(you)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)。變(bian)(bian)(bian)壓(ya)器(qi)運行中的(de)允許溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)按(an)上層油(you)(you)(you)(you)(you)(you)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)來檢查。對于(yu) A 級(ji)絕(jue)緣的(de)變(bian)(bian)(bian)壓(ya)器(qi)在正(zheng)常運 行中,當周圍(wei)空氣溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)最(zui)高(gao)為 400C 時,變(bian)(bian)(bian)壓(ya)器(qi)繞組的(de)極限工作(zuo)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)是(shi) 1050C。由于(yu)繞組的(de)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)比油(you)(you)(you)(you)(you)(you)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)度(du)(du)高(gao) 100C,為防止油(you)(you)(you)(you)(you)(you)質劣化(hua),規定變(bian)(bian)(bian)壓(ya)器(qi)上層油(you)(you)(you)(you)(you)(you)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)最(zui)高(gao) 不(bu)超(chao)過 950C,而在正(zheng)常情況下(xia)(xia),為防止絕(jue)緣油(you)(you)(you)(you)(you)(you)過速氧化(hua),上層油(you)(you)(you)(you)(you)(you)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)不(bu)應超(chao)過 850C。對于(yu)采用強迫油(you)(you)(you)(you)(you)(you)循環水冷(leng)卻和風冷(leng)的(de)變(bian)(bian)(bian)壓(ya)器(qi),上層油(you)(you)(you)(you)(you)(you)溫(wen)(wen)(wen)(wen)(wen)(wen)(wen)不(bu)宜(yi)經常超(chao)過 750C。
2、允許溫升
只(zhi)監視(shi)變(bian)(bian)壓器(qi)(qi)運(yun)行(xing)(xing)中(zhong)的(de)(de)上(shang)層(ceng)油溫(wen),還不(bu)能保證變(bian)(bian)壓器(qi)(qi)的(de)(de)安(an)全運(yun)行(xing)(xing),還必須監視(shi)上(shang)層(ceng)油溫(wen)與冷卻空(kong)氣的(de)(de)溫(wen)差(cha)(cha)—即溫(wen)升(sheng)。 變(bian)(bian)壓器(qi)(qi)溫(wen)度(du)與周圍空(kong)氣溫(wen)度(du)的(de)(de)差(cha)(cha)值(zhi),稱為變(bian)(bian)壓器(qi)(qi)的(de)(de)溫(wen)升(sheng)。對 A 級絕緣的(de)(de)變(bian)(bian)壓器(qi)(qi),當周圍最高溫(wen)度(du)為 400C 時,國(guo)家(jia)標準規(gui)定繞組的(de)(de)溫(wen)升(sheng) 650C, 上(shang)層(ceng)油溫(wen)的(de)(de)允許溫(wen)升(sheng)為550C。 只(zhi)要變(bian)(bian)壓器(qi)(qi)溫(wen)升(sheng)不(bu)超過規(gui)定值(zhi),就能保證變(bian)(bian)壓器(qi)(qi)在額定負荷(he)下(xia)規(gui)定的(de)(de)運(yun)行(xing)(xing)年限內(nei)安(an)全運(yun)行(xing)(xing)。
3、合理容量
在(zai)正常運行時,應(ying)使變壓(ya)器(qi)承(cheng)受的用電(dian)負(fu)荷在(zai)變壓(ya)器(qi)額定容量的 75—90% 左右(you)。
4、變壓器低壓最大不平衡電流不得超過額定值的25%;變壓器電源電壓變化允許范圍為額定電壓的正負 5%
如果超過這一(yi)(yi)范圍應(ying)采用分接(jie)開(kai)關(guan)(guan)進(jin)行調整(zheng)(zheng), 使電壓(ya)(ya)(ya)達(da)到(dao)規定范圍。 (調整(zheng)(zheng) 時應(ying)停電進(jin)行)通常是(shi)(shi)改(gai)變(bian)(bian)一(yi)(yi)次繞(rao)組分接(jie)抽頭的(de)(de)位置實(shi)現(xian)調壓(ya)(ya)(ya)的(de)(de),連接(jie)及切換 分接(jie)抽頭位置的(de)(de)裝置叫分接(jie)開(kai)關(guan)(guan),它是(shi)(shi)通過改(gai)變(bian)(bian)變(bian)(bian)壓(ya)(ya)(ya)器(qi)高壓(ya)(ya)(ya)繞(rao)組的(de)(de)匝(za)數來調整(zheng)(zheng) 變(bian)(bian)比的(de)(de)。電壓(ya)(ya)(ya)低對變(bian)(bian)壓(ya)(ya)(ya)器(qi)本身無影(ying)響,只降(jiang)低一(yi)(yi)些出力,但對用電設備有影(ying)響; 電壓(ya)(ya)(ya)增(zeng)高,磁通增(zeng)加(jia),鐵(tie)芯飽和,鐵(tie)芯損(sun)耗增(zeng)加(jia),變(bian)(bian)壓(ya)(ya)(ya)器(qi)溫度升高。
5、過負荷
過負荷分正常過負荷和事故過負荷兩種情況。正常過負荷是在正常供電情況下,用戶用電量增加而引起的。它將使變壓器溫度升高,導致變壓器絕緣(yuan)加 速老化(hua),使用壽命(ming)降低,因(yin)此一(yi)般情況下不允許過(guo)負(fu)荷(he)(he)運行(xing)。特(te)殊(shu)情況變壓(ya)(ya)器 可在短時(shi)間(jian)內(nei)過(guo)負(fu)荷(he)(he)運行(xing),但在冬(dong)季(ji)不得(de)超過(guo)額(e)(e)定(ding)(ding)負(fu)荷(he)(he) 30%,夏季(ji)不得(de)超過(guo)額(e)(e) 定(ding)(ding)負(fu)荷(he)(he)的 15%。此外,應根據變壓(ya)(ya)器的溫升與制(zhi)造(zao)廠(chang)規定(ding)(ding)來確(que)定(ding)(ding)變壓(ya)(ya)器的過(guo)負(fu) 荷(he)(he)能(neng)力。
當電力系統或(huo)用戶變(bian)電站(zhan)發生事(shi)故(gu)時,為保(bao)證對重(zhong)要(yao)設備的(de)(de)連續供電,故(gu) 允許變(bian)壓(ya)(ya)器(qi)短(duan)時間過負(fu)(fu)(fu)荷(he)(he)運(yun)(yun)行,即事(shi)故(gu)過負(fu)(fu)(fu)荷(he)(he),事(shi)故(gu)過負(fu)(fu)(fu)荷(he)(he)時會引(yin)起線圈溫度(du) 超過允許值,因(yin)此對絕緣來講(jiang)比正常(chang)條(tiao)件老化(hua)要(yao)快。但事(shi)故(gu)過負(fu)(fu)(fu)荷(he)(he)的(de)(de)機會少, 在一般情況(kuang)下變(bian)壓(ya)(ya)器(qi)又是(shi)欠負(fu)(fu)(fu)荷(he)(he)運(yun)(yun)行,所以短(duan)時的(de)(de)過負(fu)(fu)(fu)荷(he)(he)致(zhi)于損壞(huai)變(bian)壓(ya)(ya)器(qi)的(de)(de)絕 緣。事(shi)故(gu)過負(fu)(fu)(fu)荷(he)(he)的(de)(de)時間及(ji)倍數應(ying)根(gen)據制造(zao)廠規(gui)定執行。
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