電力施工過程何謂跨步電壓(ya)?何謂接觸電壓(ya)?
當電(dian)(dian)(dian)氣裝置發生(sheng)對地(di)(di)短路故(gu)障(zhang)后，故(gu)障(zhang)電(dian)(dian)(dian)流(liu)從(cong)故(gu)障(zhang)點(dian)的地(di)(di)通過大(da)地(di)(di)到接(jie)地(di)(di)極(ji)，回到電(dian)(dian)(dian)源，于(yu)是(shi)在故(gu)障(zhang)點(dian)的地(di)(di)和接(jie)地(di)(di)極(ji)周圍產生(sheng)一個電(dian)(dian)(dian)場(chang)(chang)(chang)，離故(gu)障(zhang)點(dian)的地(di)(di)或接(jie)地(di)(di)極(ji)的地(di)(di)越近，電(dian)(dian)(dian)位(wei)(wei)越高，越遠則電(dian)(dian)(dian)位(wei)(wei)越低，離開(kai)20m，則可視(shi)為零(ling)。人(ren)(ren)兩腳分開(kai)相(xiang)距約為0.8m時，站在這個電(dian)(dian)(dian)場(chang)(chang)(chang)內(nei)，由于(yu)兩腳處于(yu)不同的電(dian)(dian)(dian)位(wei)(wei)點(dian)，就(jiu)有一個電(dian)(dian)(dian)位(wei)(wei)差，此電(dian)(dian)(dian)位(wei)(wei)差稱為跨(kua)步電(dian)(dian)(dian)壓。當人(ren)(ren)處于(yu)電(dian)(dian)(dian)場(chang)(chang)(chang)內(nei)有麻電(dian)(dian)(dian)感覺時，不能(neng)奔跑逃(tao)離電(dian)(dian)(dian)場(chang)(chang)(chang)，而應(ying)該單(dan)腳跳或細步離開(kai)電(dian)(dian)(dian)場(chang)(chang)(chang)。
某工(gong)地(di)，民工(gong)赤腳(jiao)挖溝時(shi)，兩腳(jiao)底(di)有麻(ma)電(dian)(dian)感覺(jue)，為了(le)找到麻(ma)電(dian)(dian)的(de)原因(yin)，利用跨步(bu)電(dian)(dian)壓(ya)(ya)的(de)原理，把一(yi)根金屬探(tan)棒(bang)(bang)插入(ru)故障點，移動另一(yi)根探(tan)棒(bang)(bang)，兩根探(tan)棒(bang)(bang)間接一(yi)只(zhi)電(dian)(dian)壓(ya)(ya)表(biao)，當探(tan)棒(bang)(bang)移至一(yi)變(bian)壓(ya)(ya)器(qi)的(de)接地(di)極(ji)時(shi)，出(chu)現_電(dian)(dian)壓(ya)(ya)，于(yu)是(shi)斷(duan)(duan)定跨步(bu)電(dian)(dian)壓(ya)(ya)來自此變(bian)壓(ya)(ya)器(qi)的(de)接地(di)故障電(dian)(dian)流，然(ran)后再用分(fen)路切斷(duan)(duan)該(gai)變(bian)壓(ya)(ya)器(qi)的(de)輸(shu)出(chu)回路，很快找到原因(yin)，是(shi)一(yi)根沿(yan)地(di)面臨時(shi)敷設的(de)電(dian)(dian)纜漏電(dian)(dian)所致。
電(dian)氣(qi)設備(bei)困絕緣損壞，發生(sheng)碰殼短路時(shi)，人觸及此電(dian)氣(qi)設備(bei)就(jiu)有遭到電(dian)擊的危險。為了衡量(liang)危險程度(du)，測出離(li)電(dian)氣(qi)設備(bei)水平A向0．8m（相當于(yu)跨(kua)步距離(li)）的地(di)電(dian)位(wei)(wei)和電(dian)氣(qi)裝置垂直(zhi)方向1．8m處（人手觸及的部(bu)位(wei)(wei)）的設備(bei)發生(sheng)故障時(shi)所帶的電(dian)位(wei)(wei)，兩(liang)者的電(dian)位(wei)(wei)差(cha)稱為接觸電(dian)壓(ya)。
如(ru)果設(she)備(bei)未接(jie)(jie)地(di)(di)，220V的(de)相(xiang)線(xian)碰殼(ke)，這時(shi)產生(sheng)的(de)接(jie)(jie)觸電(dian)(dian)壓(ya)可達到相(xiang)電(dian)(dian)壓(ya)大小；如(ru)果設(she)備(bei)接(jie)(jie)地(di)(di)，其接(jie)(jie)觸電(dian)(dian)壓(ya)與設(she)備(bei)的(de)接(jie)(jie)地(di)(di)電(dian)(dian)阻(zu)大小有關，當設(she)備(bei)的(de)接(jie)(jie)地(di)(di)電(dian)(dian)阻(zu)與電(dian)(dian)源的(de)工作接(jie)(jie)地(di)(di)電(dian)(dian)阻(zu)相(xiang)等(deng)時(shi)，接(jie)(jie)觸電(dian)(dian)壓(ya)可達到110V。
設備(bei)的(de)接地即使(shi)非常(chang)好，在(zai)(zai)故障電壓未切(qie)斷前(qian)，接觸(chu)電壓也是(shi)存(cun)在(zai)(zai)的(de)。只有故障電壓被斷路器或(huo)熔(rong)絲切(qie)斷后(hou)，才解除電擊的(de)危(wei)險。
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