當線路的電壓超過220kv時，為了降(jiang)低線路電抗和電暈損耗，通常采用擴徑導線。

擴徑導(dao)線(xian)(xian)(xian)就是把普通的導(dao)線(xian)(xian)(xian)做成(cheng)中空(kong)（里面用(yong)多股芯線(xian)(xian)(xian)和支(zhi)撐層做成(cheng)）或者減少其中部分層單(dan)線(xian)(xian)(xian)數量(liang)（使該層單(dan)線(xian)(xian)(xian)間存在一定數量(liang)空(kong)隙），最終達(da)到增加導(dao)線(xian)(xian)(xian)的等效半(ban)徑的目的。

擴徑導(dao)線(xian)是(shi)以滿(man)足技術(shu)條件(jian)的常規導(dao)線(xian)規格為基(ji)準，采取擴大導(dao)線(xian)外徑技術(shu)，在保證電暈所要求的導(dao)線(xian)外徑前提下，減(jian)少導(dao)線(xian)的鋁(lv)截面，從而減(jian)少導(dao)線(xian)的總重(zhong)量，減(jian)少鐵塔(ta)荷(he)載和結(jie)構重(zhong)量，極(ji)大地降低(di)線(xian)路造價。

擴(kuo)(kuo)徑導線(xian)(xian)(xian)(xian)通過支撐鋁線(xian)(xian)(xian)(xian)疏繞的(de)(de)方式 擴(kuo)(kuo)大了(le)導線(xian)(xian)(xian)(xian)外徑，這樣可減(jian)小導線(xian)(xian)(xian)(xian)表面的(de)(de)電(dian)(dian)場強度和電(dian)(dian)暈放電(dian)(dian)，降(jiang)低噪聲，減(jian)少(shao)對無線(xian)(xian)(xian)(xian)電(dian)(dian)的(de)(de)干擾。相對于常規(gui)導線(xian)(xian)(xian)(xian)，擴(kuo)(kuo)徑導線(xian)(xian)(xian)(xian)重(zhong)量較輕，安裝敷設后的(de)(de)塑蠕伸長減(jian)小，導線(xian)(xian)(xian)(xian)永久變(bian)形(xing)減(jian)少(shao)，在滿足輸(shu)送(song)容量要(yao)求和環境(jing)保護指標(biao)的(de)(de)前(qian)提下(xia)，可大幅降(jiang)低線(xian)(xian)(xian)(xian)路的(de)(de)整體造(zao)價(jia)。簡單說(shuo)來，擴(kuo)(kuo)徑導線(xian)(xian)(xian)(xian)是(shi)(shi)從常規(gui)導線(xian)(xian)(xian)(xian)中抽取數(shu)股鋁線(xian)(xian)(xian)(xian)后繞制而成(cheng)的(de)(de)，是(shi)(shi)常規(gui)導線(xian)(xian)(xian)(xian)時升級進(jin)化品。