當(dang)線路的電(dian)壓超(chao)過(guo)220kv時，為了降(jiang)低(di)線路電(dian)抗和電(dian)暈損耗(hao)，通常采用擴徑導線。

擴(kuo)徑(jing)導線(xian)(xian)(xian)就是把(ba)普通的(de)導線(xian)(xian)(xian)做(zuo)成中(zhong)空（里面用多(duo)股芯線(xian)(xian)(xian)和支撐層(ceng)做(zuo)成）或者(zhe)減少(shao)其中(zhong)部(bu)分層(ceng)單(dan)線(xian)(xian)(xian)數(shu)量(liang)（使該(gai)層(ceng)單(dan)線(xian)(xian)(xian)間(jian)存在一定數(shu)量(liang)空隙），最終達到(dao)增加導線(xian)(xian)(xian)的(de)等效半徑(jing)的(de)目(mu)的(de)。

擴(kuo)徑導線(xian)是以滿足技(ji)術條件(jian)的常規(gui)導線(xian)規(gui)格為基(ji)準，采取擴(kuo)大導線(xian)外徑技(ji)術，在保證電(dian)暈(yun)所要求的導線(xian)外徑前提下，減(jian)少(shao)(shao)導線(xian)的鋁(lv)截(jie)面，從而減(jian)少(shao)(shao)導線(xian)的總重量，減(jian)少(shao)(shao)鐵塔荷載和結構重量，極大地降低線(xian)路造價。

擴徑導(dao)(dao)線(xian)(xian)通過支撐鋁線(xian)(xian)疏(shu)繞(rao)(rao)的(de)方式 擴大了導(dao)(dao)線(xian)(xian)外徑，這樣可(ke)減小導(dao)(dao)線(xian)(xian)表面的(de)電(dian)(dian)場強度(du)和電(dian)(dian)暈放(fang)電(dian)(dian)，降低噪聲，減少(shao)對(dui)無線(xian)(xian)電(dian)(dian)的(de)干擾。相(xiang)對(dui)于常(chang)規導(dao)(dao)線(xian)(xian)，擴徑導(dao)(dao)線(xian)(xian)重(zhong)量較輕，安(an)裝(zhuang)敷(fu)設后的(de)塑(su)蠕伸長減小，導(dao)(dao)線(xian)(xian)永久變形減少(shao)，在(zai)滿足輸送容量要(yao)求和環境(jing)保護指(zhi)標的(de)前提下，可(ke)大幅降低線(xian)(xian)路的(de)整體造價。簡單(dan)說(shuo)來，擴徑導(dao)(dao)線(xian)(xian)是從常(chang)規導(dao)(dao)線(xian)(xian)中抽取數股(gu)鋁線(xian)(xian)后繞(rao)(rao)制而成的(de)，是常(chang)規導(dao)(dao)線(xian)(xian)時(shi)升級(ji)進化品。