擴徑導(dao)線(xian)線(xian)膨(peng)脹系數較好(hao)，電(dian)暈損失小，有(you)良好(hao)的散熱性。適用(yong)于高(gao)低壓(ya)輸電(dian)線(xian)中電(dian)廠(chang)及變電(dian)站(zhan)配電(dian)線(xian)路、母線(xian)等。減(jian)少電(dian)暈損失，節約有(you)色金屬(shu)。

對(dui)(dui)于架空輸電(dian)線(xian)路，除了(le)導線(xian)電(dian)阻(zu)的有功損耗外，還有電(dian)暈損耗和沿絕(jue)緣(yuan)子漏電(dian)所(suo)致的有功損耗；對(dui)(dui)于電(dian)纜(lan)線(xian)路，主(zhu)要是(shi)介質損耗。一般在架空線(xian)路中，由絕(jue)緣(yuan)子泄(xie)露電(dian)流而產(chan)生的有功損耗極小，可忽略不記(ji)，所(suo)以對(dui)(dui)架空線(xian)路主(zhu)要考慮電(dian)暈損耗。

由(you)于架(jia)空(kong)線路(lu)(lu)的(de)絕緣(yuan)介質是空(kong)氣(qi)，當導線表(biao)面的(de)電(dian)(dian)(dian)(dian)(dian)(dian)場(chang)強(qiang)(qiang)度(du)超(chao)過空(kong)氣(qi)的(de)耐壓(ya)(ya)強(qiang)(qiang)度(du)時(shi)，空(kong)氣(qi)層就(jiu)產(chan)(chan)生游離(li)(li)形(xing)成放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)，空(kong)氣(qi)中帶電(dian)(dian)(dian)(dian)(dian)(dian)離(li)(li)子的(de)移動就(jiu)構成電(dian)(dian)(dian)(dian)(dian)(dian)暈(yun)(yun)(yun)電(dian)(dian)(dian)(dian)(dian)(dian)流。此刻，我們可以聽到(dao)滋滋的(de)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)聲，并可聞到(dao)氧分子被(bei)游離(li)(li)后又結合成臭氧的(de)氣(qi)味，在夜間(jian)可見到(dao)導線周圍發(fa)生淡藍(lan)色的(de)熒(ying)光，這(zhe)種現象(xiang)稱為電(dian)(dian)(dian)(dian)(dian)(dian)暈(yun)(yun)(yun)。電(dian)(dian)(dian)(dian)(dian)(dian)暈(yun)(yun)(yun)不(bu)但(dan)產(chan)(chan)生有(you)功損耗，而且還對無(wu)線電(dian)(dian)(dian)(dian)(dian)(dian)及高(gao)(gao)(gao)頻(pin)通(tong)訊(xun)產(chan)(chan)生干(gan)擾。電(dian)(dian)(dian)(dian)(dian)(dian)暈(yun)(yun)(yun)的(de)產(chan)(chan)生主要與(yu)輸電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)有(you)關(guan)，隨(sui)(sui)著電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)升高(gao)(gao)(gao)，電(dian)(dian)(dian)(dian)(dian)(dian)暈(yun)(yun)(yun)常是先從（尖(jian)角不(bu)光滑處）電(dian)(dian)(dian)(dian)(dian)(dian)場(chang)強(qiang)(qiang)度(du)較大(da)的(de)局部(bu)開(kai)始(shi)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)，叫(jiao)起(qi)始(shi)電(dian)(dian)(dian)(dian)(dian)(dian)暈(yun)(yun)(yun)。（起(qi)始(shi)電(dian)(dian)(dian)(dian)(dian)(dian)暈(yun)(yun)(yun)臨(lin)界強(qiang)(qiang)度(du)為30千伏/厘米）。隨(sui)(sui)后出現可見電(dian)(dian)(dian)(dian)(dian)(dian)暈(yun)(yun)(yun)，并擴大(da)到(dao)全部(bu)表(biao)面，形(xing)成全面電(dian)(dian)(dian)(dian)(dian)(dian)暈(yun)(yun)(yun)。為了減小電(dian)(dian)(dian)(dian)(dian)(dian)暈(yun)(yun)(yun)損耗，特(te)別是減少對無(wu)線電(dian)(dian)(dian)(dian)(dian)(dian)和(he)高(gao)(gao)(gao)頻(pin)通(tong)訊(xun)的(de)干(gan)擾，應盡量設法避免(mian)(mian)電(dian)(dian)(dian)(dian)(dian)(dian)暈(yun)(yun)(yun)的(de)發(fa)生。而避免(mian)(mian)電(dian)(dian)(dian)(dian)(dian)(dian)暈(yun)(yun)(yun)的(de)方法是，提(ti)高(gao)(gao)(gao)線路(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)暈(yun)(yun)(yun)的(de)臨(lin)界電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)，使其(qi)高(gao)(gao)(gao)于線路(lu)(lu)運行電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)，為此就(jiu)必(bi)須(xu)增(zeng)(zeng)(zeng)大(da)導線間(jian)的(de)距離(li)(li)和(he)導線半徑。但(dan)若(ruo)增(zeng)(zeng)(zeng)大(da)線間(jian)距離(li)(li)，必(bi)定使線路(lu)(lu)桿塔的(de)建造費用增(zeng)(zeng)(zeng)加，而對臨(lin)界電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)影(ying)響盛微(wei)。

因此。增大導線(xian)半(ban)徑(jing)(jing)才是提高(gao)臨(lin)界電(dian)壓的(de)有效方法。所以(yi)在特(te)高(gao)壓輸電(dian)線(xian)路中(zhong)，采用擴(kuo)徑(jing)(jing)導線(xian)或分(fen)(fen)裂導線(xian)（分(fen)(fen)裂導線(xian)的(de)等值半(ban)徑(jing)(jing)起(qi)了擴(kuo)徑(jing)(jing)的(de)作用）。