電纜故障檢測方法大全
標簽： 電纜故障測試儀
電纜故障檢測方法大全：對于電纜的故障點檢測一般都要經過故障類型的診斷、故障點測距、準確定點三個主要步驟。故障類型診斷主要是確定電纜故障點的故障相別,屬于高阻接地或者低阻接地,以便于測試人員選擇適當的檢測方法。故障點測距也叫預定位,故障電纜芯線上施加測試信號或者在線測量、分析故障信息,初步確定故障的距離,盡量縮小故障范圍,以方便準確定點的進行。對于直接短路或斷線電纜故障用萬用表可直接測量判斷；對于非直接短路電纜故障和(he)接(jie)地(di)電(dian)纜(lan)故障，用兆歐表(biao)遙(yao)測芯(xin)線(xian)間絕(jue)緣電(dian)阻(zu)(zu)或芯(xin)線(xian)對地(di)絕(jue)緣電(dian)阻(zu)(zu)，根據其阻(zu)(zu)值可判斷電(dian)纜(lan)故障類型。下面介紹電(dian)纜(lan)故障查找的方法(fa)：
零電位法
a）先在b和c相芯線上接上電池E，再在地面上敷設一根與故障電纜長度相等的比較導線S，該導線要用裸銅線或裸鋁線，其截面應相等，不能有中間接頭。
b）將微伏表的負極接地，正極接一根較長的軟導線，導線另一端要求在敷設的比較導線上滑動時能充分接觸。
c）合上閘刀開關S，將軟導線的端頭在比較導線上滑動，當微伏表指示為零時的位置即為電纜故障點的位置。
高壓電橋法
高壓電橋法就是用雙臂電橋測出電纜芯線的直流電阻值，再準確測量電纜實際長度，按照電纜長度與電阻的正比例關系，計算出電纜故障點。該方法對于電纜芯線間直接短路或短路點接觸電阻小于1Ω的故障，判斷誤差一般不大于3m，對于故障點接觸電阻大于1Ω的故障，可采用加高電壓燒穿的方法使電阻降至1Ω以下，再按此方法測量。測量電路時，首先測出芯線a與b之間的電阻R1，R1=2RX+R其中RX為a相或b相至電纜故障點的一相電阻值，只為短接點的接觸電阻。再就電橋移到電纜的另一端，測出a1與b1芯線間的直流電阻值R2，則R2=2R（L-X） R，R（L-X）為a1相或b1相芯線至電纜故障點的一相電阻值。測完R1與R2后，再按圖3所示電路將b1與c1短路，測出b、c兩相芯線間的直流電阻值，則該組織的1/2為每相芯線的電阻值，用RL表示，RL=RX R（L-X），由此可得出故障點的接觸電阻值：R=R1 R2-2RL表，因此，故障點兩側芯線的電阻值可用下式表示：RX=（R1-R）/2，R（L-X）=（R2-R）/2。RX、R（L-X）、RL三個數值確定后，按比例公式即可求出故障點距電纜端頭的距離X或（L-X）：X=（RX/RL）L，（L-X）=（R（L-2）在電纜的末端在測量每相芯線的電容電流Ia1、Ib2、Ic3的數值，以核對完好芯線與斷線芯線的電容之比，初步可判斷出斷線距離近似點。
根據(ju)電(dian)(dian)(dian)(dian)容(rong)(rong)量(liang)(liang)(liang)計算公式(shi)C=I/（2ΠfU）可知(zhi)，正(zheng)(zheng)電(dian)(dian)(dian)(dian)壓U、頻(pin)(pin)率f不變(bian)時，C與(yu)I成(cheng)正(zheng)(zheng)比(bi)。因為(wei)工頻(pin)(pin)電(dian)(dian)(dian)(dian)壓的f（頻(pin)(pin)率）不變(bian)，測(ce)量(liang)(liang)(liang)時只要保(bao)證施加電(dian)(dian)(dian)(dian)壓不變(bian)，電(dian)(dian)(dian)(dian)容(rong)(rong)電(dian)(dian)(dian)(dian)流之(zhi)比(bi)即為(wei)電(dian)(dian)(dian)(dian)容(rong)(rong)量(liang)(liang)(liang)之(zhi)比(bi)。設電(dian)(dian)(dian)(dian)纜(lan)全長(chang)(chang)為(wei)L，芯(xin)線(xian)(xian)斷(duan)線(xian)(xian)點距離為(wei)X，則(ze)Ia/Ic=L/X，X=（IC/Ia）L。測(ce)量(liang)(liang)(liang)過程中，只要保(bao)證電(dian)(dian)(dian)(dian)壓不變(bian)，電(dian)(dian)(dian)(dian)流表讀書(shu)準確，電(dian)(dian)(dian)(dian)纜(lan)總長(chang)(chang)度(du)測(ce)量(liang)(liang)(liang)準確，其測(ce)定誤差比(bi)較小。
測聲法
所謂(wei)測(ce)聲法就是根(gen)據故(gu)障電(dian)(dian)(dian)(dian)纜(lan)(lan)放(fang)(fang)電(dian)(dian)(dian)(dian)的聲音進行查找，該(gai)方法對(dui)(dui)于(yu)高壓(ya)電(dian)(dian)(dian)(dian)纜(lan)(lan)芯(xin)(xin)線對(dui)(dui)絕(jue)緣層(ceng)閃(shan)絡放(fang)(fang)電(dian)(dian)(dian)(dian)較(jiao)為(wei)有效。此方法所用設備為(wei)直流(liu)(liu)耐(nai)壓(ya)試(shi)(shi)驗機。其中TB為(wei)高壓(ya)試(shi)(shi)驗變壓(ya)器(qi)，C為(wei)高壓(ya)電(dian)(dian)(dian)(dian)容器(qi)，VE為(wei)高壓(ya)整流(liu)(liu)硅堆(dui)，R為(wei)限流(liu)(liu)電(dian)(dian)(dian)(dian)阻，Q為(wei)放(fang)(fang)電(dian)(dian)(dian)(dian)球間(jian)隙，L為(wei)電(dian)(dian)(dian)(dian)纜(lan)(lan)芯(xin)(xin)線。當電(dian)(dian)(dian)(dian)容器(qi)C充電(dian)(dian)(dian)(dian)到一(yi)定(ding)電(dian)(dian)(dian)(dian)壓(ya)值時(shi)(shi)，球間(jian)隙對(dui)(dui)電(dian)(dian)(dian)(dian)纜(lan)(lan)故(gu)障芯(xin)(xin)線放(fang)(fang)電(dian)(dian)(dian)(dian)，在(zai)電(dian)(dian)(dian)(dian)纜(lan)(lan)故(gu)障處電(dian)(dian)(dian)(dian)纜(lan)(lan)芯(xin)(xin)線對(dui)(dui)絕(jue)緣層(ceng)放(fang)(fang)電(dian)(dian)(dian)(dian)產生“滋、滋”的火花放(fang)(fang)電(dian)(dian)(dian)(dian)聲，對(dui)(dui)于(yu)明(ming)敷設電(dian)(dian)(dian)(dian)纜(lan)(lan)憑聽覺可(ke)直接查找，若為(wei)地埋(mai)電(dian)(dian)(dian)(dian)纜(lan)(lan)，則首(shou)先(xian)要(yao)確(que)定(ding)并標(biao)明(ming)電(dian)(dian)(dian)(dian)纜(lan)(lan)走向。查找時(shi)(shi)，將拾(shi)音器(qi)貼(tie)近地面，沿(yan)電(dian)(dian)(dian)(dian)纜(lan)(lan)走向慢慢移動，當聽到“滋、滋”放(fang)(fang)電(dian)(dian)(dian)(dian)聲大時(shi)(shi)，該(gai)處即(ji)為(wei)電(dian)(dian)(dian)(dian)纜(lan)(lan)故(gu)障點。使用該(gai)方法一(yi)定(ding)要(yao)注意安全，在(zai)試(shi)(shi)驗設備端(duan)和電(dian)(dian)(dian)(dian)纜(lan)(lan)末端(duan)應(ying)設專人(ren)監看。我公司生產的電(dian)(dian)(dian)(dian)纜(lan)(lan)故(gu)障定(ding)位儀不僅可(ke)以測(ce)聲，同時(shi)(shi)可(ke)以檢測(ce)磁信號，信號強度直觀同步顯示，能夠(gou)更快更準(zhun)的定(ding)位電(dian)(dian)(dian)(dian)纜(lan)(lan)故(gu)障點。
對低阻擊穿、短路、開路故障,可在電纜芯線上施加脈沖訊號。訊號在電纜傳達及反射,用數字示波器或手提筆記本電腦虛擬示波器等測出脈沖波形而算出故障點的位置。低壓脈沖反射法的優點是簡單、直觀,不需求細致的電纜原始材料,還能夠依據反射脈沖的極性分辨故障類型。缺陷是不能用于檢測高阻與閃絡故障。
應用傳輸線的特性阻抗發作變化時的回波現象,電纜芯線中加上一定電壓,使其不燒穿而產生放電。放電脈沖在電纜中傳達及反射,用數字示波器測出反射脈沖的位置比例,算出故障點的位置。本法適用于高阻擊穿,但操作人員的安全受要挾,波形較難區分。
三次脈沖法是一種新的電纜故障點預定位辦法,由于脈沖反射法發出的低壓脈沖在高阻故障點處不會發作反射,因而,此時故障點不會顯現在波形上,此時的低壓脈沖卻在測試電纜末端構成全反射,得到電纜全長的參考波形;
隨后發射的脈沖沖擊能夠在故障點處構成穩定的時間充分燃弧,然后運用一個高能量的檢測脈沖對故障點停止沖擊,此時脈沖幅值可到達1500V,可充沛保證在故障點構成負反射,得到故障點的故障波形。兩條波形比照可分明容易看到故障點位置。該辦法適用與除了中間頭受潮或進水特殊狀況外的一切故障類型,包括高阻接低和低阻接低。
二次脈沖法是近些年常用的測距辦法之一,其原理:對故障電纜釋放一個低壓脈沖,只需故障點的接地電阻大于電纜波阻抗5倍,能夠以為此時故障電纜相關于低壓脈沖是開路,那么在脈沖釋放端接納到反射波形相當于一個芯線絕緣良好電纜的波形;
對故障電纜釋放一個足以使芯線絕緣故障點發作閃絡的高壓脈沖,同時觸發釋放第二個低壓脈沖,故障點的電弧未熄滅時,故障點相關于低壓脈沖是完整短路,那么在脈沖釋放端接納的低壓脈沖反射波形相當于一個線芯對地完整短路的波形;兩個波形比照會有明顯的發散點,這個發散點就是故障點的反射波形點。其特性是易操作、多功用,回波圖形簡易。缺陷是不能用于檢測高阻與閃絡故障。
將被測(ce)電(dian)(dian)(dian)(dian)纜(lan)故障(zhang)相(xiang)(xiang)與(yu)非(fei)(fei)故障(zhang)相(xiang)(xiang)短接(jie),電(dian)(dian)(dian)(dian)橋(qiao)兩臂分別接(jie)故障(zhang)相(xiang)(xiang)與(yu)非(fei)(fei)故障(zhang)相(xiang)(xiang),調(diao)(diao)理電(dian)(dian)(dian)(dian)橋(qiao)兩臂上的(de)一個(ge)可調(diao)(diao)電(dian)(dian)(dian)(dian)阻(zu)器,使(shi)電(dian)(dian)(dian)(dian)橋(qiao)均衡,應(ying)用(yong)比例關(guan)系和(he)已(yi)知的(de)電(dian)(dian)(dian)(dian)纜(lan)長度就能得出故障(zhang)間隔。用(yong)低壓電(dian)(dian)(dian)(dian)橋(qiao)測(ce)電(dian)(dian)(dian)(dian)纜(lan)低阻(zu)擊(ji)穿,用(yong)電(dian)(dian)(dian)(dian)容(rong)電(dian)(dian)(dian)(dian)橋(qiao)測(ce)電(dian)(dian)(dian)(dian)纜(lan)開路(lu)斷線。電(dian)(dian)(dian)(dian)橋(qiao)法檢測(ce)結果(guo)準(zhun)確,但需(xu)求完(wan)好(hao)芯(xin)線做回路(lu),電(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)壓不能加得太高。