1kV及(ji)(ji)以下的4芯(xin)(xin)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)（3+1電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)），其中(zhong)的第4芯(xin)(xin)除作為保(bao)護接(jie)地(di)外，還(huan)要輸送電(dian)(dian)(dian)(dian)(dian)(dian)力系統在不平(ping)(ping)衡(heng)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)及(ji)(ji)短路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。它的大小由(you)不平(ping)(ping)衡(heng)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)及(ji)(ji)短路(lu)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)來確定，但一般(ban)不得(de)小于相(xiang)(xiang)(xiang)線(xian)的1/2。1kV及(ji)(ji)其以下三相(xiang)(xiang)(xiang)四線(xian)制低壓配(pei)電(dian)(dian)(dian)(dian)(dian)(dian)系統，當保(bao)護線(xian)和(he)中(zhong)性(xing)線(xian)合用同一導體時(shi)，應采用4芯(xin)(xin)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)，而(er)不得(de)采用3芯(xin)(xin)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)加單(dan)芯(xin)(xin)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)組合成一回路(lu)的方式(shi)，合肥電(dian)(dian)(dian)(dian)(dian)(dian)線(xian)，甚至直接(jie)利用3芯(xin)(xin)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)的金屬(shu)護套或鎧裝層等作中(zhong)性(xing)線(xian)的方式(shi)。否則，當3相(xiang)(xiang)(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)不平(ping)(ping)衡(heng)時(shi)，相(xiang)(xiang)(xiang)當于單(dan)芯(xin)(xin)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)的運行狀態，容易引起工頻干擾。

我們如(ru)何預防冬(dong)季電(dian)(dian)線電(dian)(dian)纜外皮脫落的(de)現(xian)象呢?1、出(chu)(chu)廠運輸：在(zai)(zai)(zai)產品(pin)(pin)(pin)出(chu)(chu)廠裝載到(dao)運輸工具上時(shi)，需(xu)要(yao)保暖(nuan)(nuan)(nuan)及保護措施。2、到(dao)達目的(de)地(di)或(huo)者施工現(xian)場時(shi)，產品(pin)(pin)(pin)供(gong)應商1好派駐(zhu)人員進行(xing)監督(du)，電(dian)(dian)線的(de)規格型號，防止(zhi)產品(pin)(pin)(pin)卸貨時(shi)出(chu)(chu)現(xian)粗暴作業行(xing)為(wei)。3、存(cun)放：1好將(jiang)產品(pin)(pin)(pin)置(zhi)于(yu)室內(nei)存(cun)放，同時(shi)在(zai)(zai)(zai)存(cun)放的(de)地(di)表上鋪(pu)上一(yi)層(ceng)隔離層(ceng)，如(ru)木(mu)板、被褥、泡沫(mo)等等，防止(zhi)產品(pin)(pin)(pin)受凍受潮，注意(yi)防止(zhi)產品(pin)(pin)(pin)與地(di)面(mian)直接接觸將(jiang)電(dian)(dian)線電(dian)(dian)纜外皮刮傷的(de)現(xian)象，輕拿輕放。4、產品(pin)(pin)(pin)敷設安裝時(shi)：1好選(xuan)擇在(zai)(zai)(zai)中下(xia)午(wu)溫度較暖(nuan)(nuan)(nuan)的(de)情(qing)況下(xia)作業，如(ru)有條(tiao)件可在(zai)(zai)(zai)使用前用暖(nuan)(nuan)(nuan)風機等設備提前給(gei)產品(pin)(pin)(pin)熱熱身(shen)，讓產品(pin)(pin)(pin)達到(dao)1好性能(neng)狀態。

購(gou)買(mai)電(dian)(dian)(dian)(dian)(dian)(dian)線(xian)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)時怎樣鑒別(bie)優(you)劣呢？一要(yao)看(kan)(kan)：看(kan)(kan)有無(wu)(wu)質(zhi)量(liang)(liang)體系認1證書；看(kan)(kan)合格(ge)證是(shi)(shi)否(fou)規范(fan)；看(kan)(kan)有無(wu)(wu)廠(chang)名、廠(chang)址、檢驗章、生產日期；看(kan)(kan)電(dian)(dian)(dian)(dian)(dian)(dian)線(xian)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)上(shang)是(shi)(shi)否(fou)印有商標(biao)、規格(ge)、電(dian)(dian)(dian)(dian)(dian)(dian)壓等(deng)。還要(yao)看(kan)(kan)電(dian)(dian)(dian)(dian)(dian)(dian)線(xian)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)銅(tong)芯(xin)的(de)橫斷(duan)面，電(dian)(dian)(dian)(dian)(dian)(dian)線(xian)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)一米多少錢，優(you)等(deng)品紫銅(tong)顏色光亮、色澤柔(rou)(rou)和，pvc電(dian)(dian)(dian)(dian)(dian)(dian)線(xian)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)，否(fou)則便是(shi)(shi)次品。二要(yao)試：可(ke)取一根(gen)電(dian)(dian)(dian)(dian)(dian)(dian)線(xian)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)頭用(yong)(yong)手反復彎曲，凡是(shi)(shi)手感柔(rou)(rou)軟(ruan)、抗(kang)1疲勞強度(du)好(hao)(hao)(hao)、塑料或橡膠手感彈(dan)性大且電(dian)(dian)(dian)(dian)(dian)(dian)線(xian)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)絕(jue)緣體上(shang)無(wu)(wu)裂痕的(de)就(jiu)是(shi)(shi)優(you)等(deng)品。電(dian)(dian)(dian)(dian)(dian)(dian)線(xian)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)是(shi)(shi)用(yong)(yong)戶在用(yong)(yong)電(dian)(dian)(dian)(dian)(dian)(dian)過程中的(de)材料，其質(zhi)量(liang)(liang)的(de)好(hao)(hao)(hao)壞(huai)，直接關(guan)系到千(qian)家萬戶的(de)用(yong)(yong)電(dian)(dian)(dian)(dian)(dian)(dian)安全。因此，在購(gou)買(mai)或選用(yong)(yong)時，如何快速、準確(que)檢查電(dian)(dian)(dian)(dian)(dian)(dian)線(xian)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)質(zhi)量(liang)(liang)的(de)好(hao)(hao)(hao)壞(huai)，是(shi)(shi)廣大電(dian)(dian)(dian)(dian)(dian)(dian)工(gong)必(bi)須掌握的(de)技(ji)能。