開關柜是在電力系統進行發電、輸電、配電和電能轉換的過程中，進行開合、控制和保護用電設備。還應保證設備長期、安全、可靠無故障地運行，在系統發生各種故障或不正常工作的情況下對供電設備和電動機實行保護，因此保護環節是所有電氣控制系統不可缺少的組成部分。開關柜控制系統(tong)中常用的(de)保(bao)護環節(jie)有短路保(bao)護、過載保(bao)護、過電流(liu)保(bao)護、失壓(ya)和欠壓(ya)保(bao)護等。

1.短路保護

電(dian)動機、電(dian)器(qi)(qi)以及導(dao)線(xian)的絕緣損壞或線(xian)路發生故障時(shi)，都可能(neng)(neng)造(zao)成短(duan)路事故。很大(da)的短(duan)路電(dian)流和(he)電(dian)動力可能(neng)(neng)使電(dian)器(qi)(qi)設備損壞。因此要(yao)求一旦發生短(duan)路故障時(shi)，控制線(xian)路能(neng)(neng)迅速切除(chu)電(dian)源。常(chang)用的短(duan)路保護元件有熔斷器(qi)(qi)和(he)低(di)壓斷路器(qi)(qi)，電(dian)動機短(duan)路保護的元件可按下述要(yao)求裝設：

1）在中性點直接接地的系統中，應在每相(xiang)上裝設。

2）在(zai)中性點不接地(di)的系統中，以熔(rong)斷(duan)器(qi)(qi)作(zuo)保護時，應(ying)在(zai)每(mei)相(xiang)上裝設(she)(she)；用低壓斷(duan)路器(qi)(qi)作(zuo)保護時，應(ying)在(zai)不少于兩相(xiang)上裝設(she)(she)。

2.過載保護

電(dian)(dian)動(dong)機長期超載(zai)(zai)運行，繞組溫升將超過(guo)其(qi)允(yun)許值，造成絕緣材料老化，壽命減小，嚴重時會使(shi)電(dian)(dian)動(dong)機損(sun)壞，過(guo)載(zai)(zai)電(dian)(dian)流越大，達到(dao)允(yun)許溫升的(de)(de)時間就(jiu)越短(duan)。常(chang)用(yong)的(de)(de)過(guo)載(zai)(zai)保護(hu)元件是(shi)熱繼(ji)電(dian)(dian)器，對大功率的(de)(de)重要電(dian)(dian)動(dong)機，應(ying)采用(yong)反時限性的(de)(de)過(guo)電(dian)(dian)流繼(ji)電(dian)(dian)器。

由于熱(re)(re)慣(guan)性的(de)原因(yin)，熱(re)(re)繼電(dian)器(qi)不(bu)會受電(dian)動機短(duan)(duan)時過(guo)載(zai)沖擊電(dian)流(liu)或短(duan)(duan)路電(dian)流(liu)的(de)影響而瞬時動作(zuo)，所以在使(shi)用熱(re)(re)繼電(dian)器(qi)作(zuo)過(guo)載(zai)保(bao)(bao)護(hu)(hu)(hu)時，還必須設(she)有短(duan)(duan)路保(bao)(bao)護(hu)(hu)(hu)，并且選作(zuo)短(duan)(duan)路保(bao)(bao)護(hu)(hu)(hu)的(de)熔斷器(qi)熔體(ti)的(de)額定電(dian)流(liu)不(bu)應超(chao)過(guo)4倍熱(re)(re)繼電(dian)器(qi)發熱(re)(re)元(yuan)件的(de)額定電(dian)流(liu)。由于過(guo)載(zai)保(bao)(bao)護(hu)(hu)(hu)特性與過(guo)電(dian)流(liu)保(bao)(bao)護(hu)(hu)(hu)特性不(bu)同，故不(bu)能用過(guo)電(dian)流(liu)保(bao)(bao)護(hu)(hu)(hu)方式來進(jin)行過(guo)載(zai)保(bao)(bao)護(hu)(hu)(hu)。

3.過電流保護

過電(dian)流保(bao)護(hu)廣(guang)泛用于(yu)(yu)直(zhi)流電(dian)動(dong)(dong)機或繞線式異步(bu)電(dian)動(dong)(dong)機。對于(yu)(yu)三相籠型(xing)異步(bu)電(dian)動(dong)(dong)機，由于(yu)(yu)其短時過電(dian)流不會產(chan)生嚴重后(hou)果，故可不設置(zhi)過電(dian)流保(bao)護(hu)。

過電(dian)流(liu)保護往往是(shi)由于不正確的啟動(dong)和過大的負載引起的，一(yi)般比短(duan)(duan)路電(dian)流(liu)要小，在電(dian)動(dong)機(ji)運行中(zhong)產生過電(dian)流(liu)比發生短(duan)(duan)路的可能(neng)性更大，尤其是(shi)在頻繁正反轉啟動(dong)的重復短(duan)(duan)時工(gong)作制電(dian)動(dong)機(ji)中(zhong)更是(shi)如(ru)此。

必(bi)須強調指出，短路、過(guo)電(dian)流、過(guo)載(zai)保護雖然都(dou)是(shi)電(dian)流保護，但由于故障電(dian)流、動(dong)作值以及(ji)保護特性、保護要求(qiu)以及(ji)使用元件的不同，它(ta)們之間是(shi)不能相互取代的。

4.失電壓保護

電(dian)(dian)(dian)(dian)動機(ji)正常工(gong)作時(shi)(shi)，如(ru)果電(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)壓(ya)(ya)因某(mou)種原因消失(shi)，那么在電(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)壓(ya)(ya)恢復(fu)時(shi)(shi)，如(ru)果電(dian)(dian)(dian)(dian)動機(ji)自行啟動，將(jiang)可能(neng)使生產設(she)備損(sun)壞，也(ye)可能(neng)造成人身事(shi)故。此外，對供電(dian)(dian)(dian)(dian)系(xi)統的(de)(de)電(dian)(dian)(dian)(dian)網，同時(shi)(shi)有(you)許(xu)多(duo)電(dian)(dian)(dian)(dian)動機(ji)及其他用電(dian)(dian)(dian)(dian)設(she)備自行啟動也(ye)會引起(qi)不允許(xu)的(de)(de)過電(dian)(dian)(dian)(dian)流及瞬間(jian)網絡電(dian)(dian)(dian)(dian)壓(ya)(ya)下降。為防止(zhi)電(dian)(dian)(dian)(dian)壓(ya)(ya)恢復(fu)時(shi)(shi)電(dian)(dian)(dian)(dian)動機(ji)自行啟動或(huo)電(dian)(dian)(dian)(dian)氣元件自行投入工(gong)作而(er)設(she)置的(de)(de)保護稱為失(shi)電(dian)(dian)(dian)(dian)壓(ya)(ya)保護。

采用(yong)(yong)接觸(chu)(chu)(chu)器(qi)和(he)按鈕控(kong)(kong)制的啟動(dong)(dong)、停止控(kong)(kong)制環節就具(ju)有失(shi)電(dian)(dian)壓(ya)保護(hu)功(gong)能(neng)。因(yin)為(wei)當電(dian)(dian)源(yuan)(yuan)電(dian)(dian)壓(ya)消(xiao)失(shi)時，接觸(chu)(chu)(chu)器(qi)會(hui)自(zi)動(dong)(dong)釋放而切(qie)斷電(dian)(dian)動(dong)(dong)機(ji)電(dian)(dian)源(yuan)(yuan)；電(dian)(dian)源(yuan)(yuan)電(dian)(dian)壓(ya)恢(hui)復(fu)時，由于接觸(chu)(chu)(chu)器(qi)自(zi)鎖(suo)觸(chu)(chu)(chu)點已斷開，不(bu)會(hui)自(zi)行啟動(dong)(dong)。如果用(yong)(yong)不(bu)能(neng)復(fu)位的手動(dong)(dong)開關、主令控(kong)(kong)制器(qi)來控(kong)(kong)制接觸(chu)(chu)(chu)器(qi)，必須采用(yong)(yong)專門的零電(dian)(dian)壓(ya)繼電(dian)(dian)器(qi)。工作過程中一旦失(shi)電(dian)(dian)壓(ya)，零電(dian)(dian)壓(ya)繼電(dian)(dian)器(qi)就釋放，其(qi)自(zi)鎖(suo)電(dian)(dian)路斷開，電(dian)(dian)源(yuan)(yuan)電(dian)(dian)壓(ya)恢(hui)復(fu)時，不(bu)會(hui)自(zi)行啟動(dong)(dong)。

5.欠電壓保護

當電(dian)(dian)(dian)(dian)(dian)動(dong)機正常(chang)運行時，電(dian)(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)(dian)壓(ya)過分地降(jiang)(jiang)低將引(yin)(yin)起一些電(dian)(dian)(dian)(dian)(dian)器(qi)釋放，造成(cheng)控(kong)制線路工作不正常(chang)，甚(shen)至(zhi)產生事(shi)故(gu)。當電(dian)(dian)(dian)(dian)(dian)網電(dian)(dian)(dian)(dian)(dian)壓(ya)過低時，如(ru)果電(dian)(dian)(dian)(dian)(dian)動(dong)機負載不變，則會造成(cheng)電(dian)(dian)(dian)(dian)(dian)動(dong)機電(dian)(dian)(dian)(dian)(dian)流增大，引(yin)(yin)起電(dian)(dian)(dian)(dian)(dian)動(dong)機發熱，嚴重時甚(shen)至(zhi)燒壞電(dian)(dian)(dian)(dian)(dian)動(dong)機。此外，電(dian)(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)(dian)壓(ya)過低還會引(yin)(yin)起電(dian)(dian)(dian)(dian)(dian)動(dong)機轉(zhuan)速下降(jiang)(jiang)，甚(shen)至(zhi)停轉(zhuan)。因此，在電(dian)(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)(dian)壓(ya)降(jiang)(jiang)到允許值以下時，需(xu)要(yao)采用保護措施，及時切斷(duan)電(dian)(dian)(dian)(dian)(dian)源(yuan)，這(zhe)就是欠電(dian)(dian)(dian)(dian)(dian)壓(ya)保護。通常(chang)是采用欠電(dian)(dian)(dian)(dian)(dian)壓(ya)繼電(dian)(dian)(dian)(dian)(dian)器(qi)來實現。

上圖為(wei)電(dian)動機(ji)常用保護的(de)接(jie)線，圖中各電(dian)器元件所起的(de)保護作(zuo)用分別為(wei)：

短(duan)路(lu)保(bao)護——熔斷器FU；

過載保護——熱繼電器(qi)FR；

過流保(bao)護——過電(dian)流繼電(dian)器KI1、KI2；

失電壓(ya)保護——中間繼電器KA；

欠(qian)電(dian)壓保(bao)護——欠(qian)電(dian)壓繼(ji)電(dian)器(qi)KV；

連(lian)鎖保護——通過KM1和(he)KM2互鎖點實現(xian)。

以上就是得潤電(dian)(dian)氣(qi)的小編給(gei)大家分(fen)享的電(dian)(dian)氣(qi)知識，希望可以電(dian)(dian)氣(qi)的朋(peng)友們有所幫助哈！

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