臨時用(yong)(yong)的電(dian)(dian)氣(qi)線(xian)(xian)路會選(xuan)擇使用(yong)(yong)銅(tong)(tong)芯(xin)電(dian)(dian)纜(lan)(lan)，而長時間穩定使用(yong)(yong)的線(xian)(xian)路一般都會選(xuan)擇銅(tong)(tong)芯(xin)電(dian)(dian)纜(lan)(lan)，鋁(lv)(lv)芯(xin)電(dian)(dian)纜(lan)(lan)的價(jia)格(ge)要(yao)(yao)比銅(tong)(tong)芯(xin)電(dian)(dian)纜(lan)(lan)底三(san)到四(si)倍，那為什么一般還是(shi)要(yao)(yao)選(xuan)擇使用(yong)(yong)銅(tong)(tong)芯(xin)電(dian)(dian)纜(lan)(lan)，那是(shi)因(yin)為鋁(lv)(lv)芯(xin)電(dian)(dian)線(xian)(xian)電(dian)(dian)纜(lan)(lan)起火的危(wei)險系數要(yao)(yao)高(gao)于(yu)于(yu)銅(tong)(tong)芯(xin)電(dian)(dian)線(xian)(xian)電(dian)(dian)纜(lan)(lan)，鋁(lv)(lv)芯(xin)電(dian)(dian)線(xian)(xian)電(dian)(dian)纜(lan)(lan)如(ru)意(yi)引起火的原因(yin)有(you)大致有(you)以下幾點：

（1）鋁(lv)(lv)(lv)線表(biao)(biao)面(mian)易在(zai)空(kong)氣(qi)中氧(yang)化(hua)。凡導(dao)體表(biao)(biao)面(mian)都(dou)或(huo)多或(huo)少(shao)地存在(zai)膜(mo)(mo)電阻。若膜(mo)(mo)電阻引起(qi)連接(jie)(jie)處過(guo)熱(re)(re)，過(guo)熱(re)(re)又使膜(mo)(mo)電阻增(zeng)大(da)，導(dao)電情況就(jiu)越惡化(hua)，而鋁(lv)(lv)(lv)線連接(jie)(jie)中這(zhe)類過(guo)熱(re)(re)的情況尤(you)為(wei)嚴(yan)重。這(zhe)是(shi)因為(wei)鋁(lv)(lv)(lv)線表(biao)(biao)面(mian)即使刮擦光潔(jie)，它(ta)只(zhi)需在(zai)空(kong)氣(qi)中暴露數秒鐘(zhong)即可(ke)被氧(yang)化(hua)而立(li)即形成(cheng)一(yi)層氧(yang)化(hua)鋁(lv)(lv)(lv)薄(bo)膜(mo)(mo)。其厚度雖只(zhi)幾個微米，但卻具有很高的電阻率，從而呈(cheng)現較大(da)的膜(mo)(mo)電阻。因此在(zai)鋁(lv)(lv)(lv)線施工連接(jie)(jie)時，應(ying)在(zai)刮擦干(gan)凈(jing)鋁(lv)(lv)(lv)線表(biao)(biao)面(mian)后(hou)立(li)即涂以導(dao)電膏，以隔斷鋁(lv)(lv)(lv)線連接(jie)(jie)表(biao)(biao)面(mian)與空(kong)氣(qi)的接(jie)(jie)觸，不然將增(zeng)大(da)接(jie)(jie)觸電阻。

（2）高膨(peng)脹系(xi)數。鋁(lv)的(de)(de)(de)膨(peng)脹系(xi)數高達(da)23 10-6／℃，比(bi)(bi)(bi)銅大(da)39％．比(bi)(bi)(bi)鐵大(da)97％。當鋁(lv)線與(yu)這(zhe)(zhe)兩(liang)種(zhong)金(jin)屬導(dao)體連(lian)(lian)(lian)接(jie)(jie)(jie)(jie)并通(tong)(tong)過電(dian)(dian)(dian)流時(shi)(shi)，連(lian)(lian)(lian)接(jie)(jie)(jie)(jie)點(dian)因存在接(jie)(jie)(jie)(jie)觸(chu)電(dian)(dian)(dian)阻(zu)而(er)發熱(re)。這(zhe)(zhe)三種(zhong)導(dao)體都(dou)膨(peng)脹，但鋁(lv)比(bi)(bi)(bi)銅、鐵膨(peng)脹更多(duo)，從而(er)使(shi)鋁(lv)線受擠壓。線路斷電(dian)(dian)(dian)冷卻后鋁(lv)線稍(shao)許壓扁而(er)不能完(wan)全(quan)恢(hui)復原狀，這(zhe)(zhe)樣就(jiu)在連(lian)(lian)(lian)接(jie)(jie)(jie)(jie)處(chu)出現(xian)空隙而(er)松動，并因進入(ru)空氣(qi)而(er)形(xing)成氧化鋁(lv)薄膜，這(zhe)(zhe)樣就(jiu)使(shi)接(jie)(jie)(jie)(jie)觸(chu)電(dian)(dian)(dian)阻(zu)增大(da)。下次通(tong)(tong)電(dian)(dian)(dian)時(shi)(shi)發熱(re)將更劇，使(shi)情況更為惡化，嚴重時(shi)(shi)可能因產生異常高溫或進發電(dian)(dian)(dian)火(huo)花(hua)而(er)引燃起火(huo)。為此大(da)截(jie)(jie)面(mian)積的(de)(de)(de)鋁(lv)導(dao)體與(yu)銅、鐵導(dao)體連(lian)(lian)(lian)接(jie)(jie)(jie)(jie)時(shi)(shi)應配置過渡接(jie)(jie)(jie)(jie)頭。小截(jie)(jie)面(mian)積（不大(da)于(yu)6mm2）鋁(lv)線的(de)(de)(de)連(lian)(lian)(lian)接(jie)(jie)(jie)(jie)則應采用彈簧壓接(jie)(jie)(jie)(jie)帽，這(zhe)(zhe)樣無論連(lian)(lian)(lian)接(jie)(jie)(jie)(jie)處(chu)是否通(tong)(tong)電(dian)(dian)(dian)，有(you)無發熱(re)，連(lian)(lian)(lian)接(jie)(jie)(jie)(jie)接(jie)(jie)(jie)(jie)觸(chu)面(mian)都(dou)處(chu)于(yu)彈簧的(de)(de)(de)壓力下而(er)使(shi)空氣(qi)和潮氣(qi)無隙可入(ru)，從而(er)保(bao)持連(lian)(lian)(lian)接(jie)(jie)(jie)(jie)的(de)(de)(de)導(dao)電(dian)(dian)(dian)良(liang)好。

（3）易出(chu)現電(dian)(dian)(dian)解腐蝕(shi)作用。若不同電(dian)(dian)(dian)位(wei)的(de)(de)兩(liang)金(jin)屬間存(cun)在帶酸性(xing)(xing)或堿性(xing)(xing)的(de)(de)液(ye)體，則兩(liang)金(jin)屬將(jiang)形成(cheng)局部(bu)電(dian)(dian)(dian)池。鋁(lv)的(de)(de)電(dian)(dian)(dian)位(wei)為(wei)(wei)-0.78V，而銅為(wei)(wei)-0.17V，當鋁(lv)導(dao)體與銅導(dao)體間存(cun)在含鹽分的(de)(de)水分時就形成(cheng)此種局部(bu)電(dian)(dian)(dian)池。電(dian)(dian)(dian)離(li)作用將(jiang)使電(dian)(dian)(dian)位(wei)低的(de)(de)鋁(lv)導(dao)體受到腐蝕(shi)而增(zeng)大接觸(chu)電(dian)(dian)(dian)阻(zu)。

（4）易被氯(lv)(lv)化(hua)氫腐(fu)蝕(shi)。對于PVC絕(jue)緣的(de)鋁芯電(dian)線、電(dian)纜(lan)，還可能出現另一個問(wen)題(ti)。為阻(zu)止(zhi)PVC絕(jue)緣分(fen)解(jie)出氯(lv)(lv)化(hua)氫氣體，PVC絕(jue)緣內添加有阻(zu)止(zhi)分(fen)解(jie)氯(lv)(lv)化(hua)氫的(de)穩(wen)定劑。但當線路溫度超過(guo)75℃時，例如發生線路過(guo)載或(huo)因其他(ta)原因而使連接處溫度過(guo)高時，穩(wen)定劑就不再能阻(zu)止(zhi)氯(lv)(lv)化(hua)氫的(de)形成，而氯(lv)(lv)化(hua)氫是要腐(fu)蝕(shi)鋁的(de)，這(zhe)同(tong)樣也將(jiang)增(zeng)大接觸電(dian)阻(zu)和起火危險。

文章編輯：CobiNet(寧波)  
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