產品搜(sou)索
電纜(lan)故障測試儀是由系統主機和故障定位儀以及電纜(lan)路徑(jing)儀三部分組成。
電纜故障測試儀是光纜、電纜故障定位測試的儀表，適用測試對象為具有金屬導體(線對、護層、屏蔽層)的各種光纜、電纜。其主要功能為對地下絕緣不良點的定位測試，線纜路徑的探測以及線纜埋深的測試。這次主要介紹電纜故障測試儀尋找軌跡的原理，也稱為大信號法的工作原理。
1.尋找軌(gui)跡原理(大信號(hao)法)
我們知道(dao)，當交(jiao)流(liu)電(dian)(dian)流(liu)在導體(ti)中流(liu)過時(shi)，將會在導體(ti)周圍產(chan)(chan)生(sheng)交(jiao)變的(de)(de)磁(ci)(ci)(ci)場，并且該(gai)磁(ci)(ci)(ci)場的(de)(de)磁(ci)(ci)(ci)力線(xian)(xian)都是(shi)以該(gai)導體(ti)為(wei)同軸的(de)(de)。此(ci)時(shi)如(ru)果將一電(dian)(dian)磁(ci)(ci)(ci)線(xian)(xian)圈(quan)(quan)(quan)放入該(gai)磁(ci)(ci)(ci)場中，線(xian)(xian)圈(quan)(quan)(quan)的(de)(de)兩(liang)端就會產(chan)(chan)生(sheng)感(gan)應電(dian)(dian)壓。移動感(gan)應線(xian)(xian)圈(quan)(quan)(quan)，當線(xian)(xian)圈(quan)(quan)(quan)的(de)(de)方向(xiang)(xiang)與磁(ci)(ci)(ci)力線(xian)(xian)方向(xiang)(xiang)相同時(shi)，線(xian)(xian)圈(quan)(quan)(quan)兩(liang)端產(chan)(chan)生(sheng)的(de)(de)感(gan)應電(dian)(dian)壓將會大。也就是(shi)說，當線(xian)(xian)圈(quan)(quan)(quan)方向(xiang)(xiang)與導體(ti)方向(xiang)(xiang)垂直(zhi)時(shi)，感(gan)應電(dian)(dian)壓大;當線(xian)(xian)圈(quan)(quan)(quan)方向(xiang)(xiang)與導體(ti)方向(xiang)(xiang)平行時(shi)，感(gan)應電(dian)(dian)壓小。由此(ci)我們就得到了“大信號法(fa)(fa)"來探尋埋地電(dian)(dian)纜的(de)(de)軌跡，利(li)用接收線(xian)(xian)圈(quan)(quan)(quan)的(de)(de)45°法(fa)(fa)則(ze)可以測出地下線(xian)(xian)纜的(de)(de)埋深(shen)。
2、電(dian)纜故障定位(wei)原理
(1)差(cha)分電(dian)位法
如果一埋(mai)地電(dian)纜(lan)(lan)發生接地故障，我(wo)們可以利用電(dian)位差法(fa)(fa)找(zhao)出故障點(dian)(dian)(dian)。方法(fa)(fa)是在故障電(dian)纜(lan)(lan)的(de)測試(shi)(shi)點(dian)(dian)(dian)與地之間加上測試(shi)(shi)電(dian)壓，那么(me)在電(dian)纜(lan)(lan)的(de)入地點(dian)(dian)(dian)周圍將會形成以入地點(dian)(dian)(dian)為同(tong)心的(de)分布電(dian)場。該電(dian)場中(zhong)半(ban)徑相同(tong)的(de)任(ren)意點(dian)(dian)(dian)之間不存在電(dian)位差，但半(ban)徑不同(tong)的(de)任(ren)意兩(liang)點(dian)(dian)(dian)間卻(que)存在電(dian)位差(如圖中(zhong)A、B兩(liang)點(dian)(dian)(dian))，而且(qie)當兩(liang)點(dian)(dian)(dian)間距固定時(shi)，兩(liang)點(dian)(dian)(dian)離中(zhong)心越近電(dian)位差越強。
利用(yong)這(zhe)一特(te)點(dian)(dian)(dian)，我們就可(ke)以移(yi)動(dong)A、B兩點(dian)(dian)(dian)逐漸向中(zhong)心點(dian)(dian)(dian)逼近。當故障點(dian)(dian)(dian)恰好(hao)位(wei)于A、B兩點(dian)(dian)(dian)中(zhong)間時(shi)，電位(wei)差變為零(ling)。如(ru)果(guo)繼續移(yi)動(dong)越過故障點(dian)(dian)(dian)時(shi)，電位(wei)差極性將會反相，如(ru)此來(lai)回(hui)移(yi)動(dong)就可(ke)準確判斷出接地點(dian)(dian)(dian)。
(2)震(zhen)動探測法
當電(dian)纜呈現(xian)高阻故(gu)障，須使用沖擊閃絡(luo)法檢(jian)測故(gu)障時，故(gu)障點(dian)對(dui)地放電(dian)將會對(dui)地面產生輕微的(de)震動，此(ci)時可以(yi)利(li)用震動傳感器(qi)探測震中的(de)方法找出故(gu)障點(dian)。
