高溫水泵跳閘故障排除

1：故障現象 

　　梅縣發電廠125 mw機組自投產以來，給水泵偶爾會發生一合閘即跳閘的問題，并無任何信號繼電器掉牌。在排除了開關機構故障后，按常規方法檢查電纜、二次回路接線和各繼電器及其定值都正常，再次啟動又往往成功。后懷疑是dcs系統軟故障造成的，但改在控制盤上操作，仍會出現此現象。 

　　2：試驗查找原因 

　　為查清楚此現象的原因，觀察開關合閘過程中各表計的變化情況，以確認是何原因使其跳閘。 

　　試驗其中電壓表監視微機跳閘回路，毫安表監視差動繼電器1cj、2cj動作情況，電流表監視熱工保護回路。接好表計后，啟動給水泵，經過一段時間的試驗，終于有一次給水泵一啟動即跳閘，同時觀察到毫安表的指針偏轉了一下，其它監視表計沒有反應，新換上的xjl-0025/31型集成塊式信號繼電器1xj亦動作掉牌，表明是由差動保護動作導致跳閘。 

　　3：根源分析 

　　差動保護動作，首先懷疑被保護設備內部有故障。通過常規檢查，給水泵電機及其電纜正常，差動繼電器校驗正常，電流互感器極性連接正確。在排除設備故障和接線錯誤的原因后，差動保護在電機啟動過程中動作，表明在這過程中差動回路的差電流超過差動繼電器整定值。 

　　正常情況下引起差動回路差電流的原因主要有兩點：一是電機首尾兩側的電流互感器變比誤差不同，存在一個很小的差電流，這個差電流小于電機額定電流id的5%。二是首尾兩側電流互感器二次負荷的差別也會引起其變比的差別，從而存在一個差電流。在給水泵電機差動保護回路中的電流互感器負荷差別只是二次電纜長度的不同，大約相差50 m，并且在額定電流下，差動繼電器的功率消耗不大于3 va，二次負載并不重。檢查發現給水泵電機差動保護用的首尾側電流互感器型號均為lmzbj-10，b級15倍額定電流，變比600/5，容量40 va，完滿足二次負載的要求。 

　　以上(shang)分析(xi)是(shi)基于正(zheng)常運(yun)行(xing)的(de)(de)(de)(de)(de)條件下，在電機(ji)(ji)啟動(dong)(dong)(dong)(dong)(dong)(dong)(dong)時(shi)(shi)(shi)，情況(kuang)又有所不(bu)(bu)(bu)同(tong)。電機(ji)(ji)啟動(dong)(dong)(dong)(dong)(dong)(dong)(dong)時(shi)(shi)(shi)電流(liu)(liu)(liu)很大(da)(da)，首尾兩(liang)側的(de)(de)(de)(de)(de)電流(liu)(liu)(liu)互(hu)(hu)感(gan)(gan)(gan)(gan)器(qi)(qi)可能飽(bao)(bao)和(he)，此時(shi)(shi)(shi)由于各電流(liu)(liu)(liu)互(hu)(hu)感(gan)(gan)(gan)(gan)器(qi)(qi)磁化特性不(bu)(bu)(bu)一(yi)致，二次差(cha)電流(liu)(liu)(liu)可能很大(da)(da)。根(gen)據阿城繼(ji)電器(qi)(qi)廠(chang)的(de)(de)(de)(de)(de)lcd-12型(xing)差(cha)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)繼(ji)電器(qi)(qi)整定(ding)(ding)(ding)說明(ming)，繼(ji)電器(qi)(qi)的(de)(de)(de)(de)(de)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)作電流(liu)(liu)(liu)整定(ding)(ding)(ding)值izd=△i1×kk×in/n=0.06×3×356/120=0.534a(式中：△i1—首、尾端電流(liu)(liu)(liu)互(hu)(hu)感(gan)(gan)(gan)(gan)器(qi)(qi)正(zheng)常運(yun)行(xing)時(shi)(shi)(shi)的(de)(de)(de)(de)(de)zui大(da)(da)誤差(cha)，0.04～0.06；kk—可靠系(xi)(xi)數(shu)(shu)，2～3；in—電機(ji)(ji)額定(ding)(ding)(ding)電流(liu)(liu)(liu)；n—電流(liu)(liu)(liu)互(hu)(hu)感(gan)(gan)(gan)(gan)器(qi)(qi)變比)。應整定(ding)(ding)(ding)在1.0a的(de)(de)(de)(de)(de)位置(zhi)。在使(shi)用b級(ji)互(hu)(hu)感(gan)(gan)(gan)(gan)器(qi)(qi)的(de)(de)(de)(de)(de)情況(kuang)下，差(cha)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)繼(ji)電器(qi)(qi)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)作電流(liu)(liu)(liu)整定(ding)(ding)(ding)在1.，制(zhi)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)系(xi)(xi)數(shu)(shu)為0.4時(shi)(shi)(shi)，差(cha)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)保護在電機(ji)(ji)啟動(dong)(dong)(dong)(dong)(dong)(dong)(dong)時(shi)(shi)(shi)仍偶爾會動(dong)(dong)(dong)(dong)(dong)(dong)(dong)作，是(shi)由于b級(ji)電流(liu)(liu)(liu)互(hu)(hu)感(gan)(gan)(gan)(gan)器(qi)(qi)磁化特性飽(bao)(bao)和(he)點較(jiao)低，抗飽(bao)(bao)和(he)能力較(jiao)低，不(bu)(bu)(bu)能滿足差(cha)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)繼(ji)電器(qi)(qi)的(de)(de)(de)(de)(de)要求。通常要求差(cha)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)保護回路的(de)(de)(de)(de)(de)電流(liu)(liu)(liu)互(hu)(hu)感(gan)(gan)(gan)(gan)器(qi)(qi)采(cai)用d級(ji)，d級(ji)互(hu)(hu)感(gan)(gan)(gan)(gan)器(qi)(qi)的(de)(de)(de)(de)(de)飽(bao)(bao)和(he)點高一(yi)些，沒那么容(rong)易飽(bao)(bao)和(he)，可以減小電機(ji)(ji)啟動(dong)(dong)(dong)(dong)(dong)(dong)(dong)時(shi)(shi)(shi)流(liu)(liu)(liu)過差(cha)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)回路的(de)(de)(de)(de)(de)差(cha)電流(liu)(liu)(liu)。在更(geng)換為d級(ji)的(de)(de)(de)(de)(de)電流(liu)(liu)(liu)互(hu)(hu)感(gan)(gan)(gan)(gan)器(qi)(qi)，同(tong)時(shi)(shi)(shi)把差(cha)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)繼(ji)電器(qi)(qi)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)作電流(liu)(liu)(liu)整定(ding)(ding)(ding)在1.0a，制(zhi)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)系(xi)(xi)數(shu)(shu)為0.4后，再沒出現過開關(guan)一(yi)合閘即(ji)跳閘的(de)(de)(de)(de)(de)故障。