隨(sui)著(zhu)負荷(he)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流變(bian)(bian)化及環境溫度變(bian)(bian)化，可能有(you)些電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)產(chan)品會(hui)發生(sheng)(sheng)熱(re)伸(shen)縮(suo)的(de)(de)情況(kuang)，其中(zhong)因電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)線芯的(de)(de)熱(re)脹冷縮(suo)而產(chan)生(sheng)(sheng)非常大(da)(da)的(de)(de)熱(re)機械力(li)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)線芯截面越大(da)(da)，所產(chan)生(sheng)(sheng)的(de)(de)熱(re)機械力(li)就越大(da)(da);同時線芯和金屬(shu)護套(tao)還會(hui)因熱(re)脹冷縮(suo)的(de)(de)多次循(xun)環，而產(chan)生(sheng)(sheng)蠕(ru)變(bian)(bian)。熱(re)伸(shen)縮(suo)對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)力(li)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)運行構成很(hen)大(da)(da)的(de)(de)威脅，會(hui)造成運行電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)位移、滑(hua)落，甚(shen)至損壞電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)及附件。目前國內己選用(yong)的(de)(de)最大(da)(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)截面為7 X 1600 mm,因此必(bi)須重視大(da)(da)截面電(dian)(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)(lan)(lan)的(de)(de)熱(re)伸(shen)縮(suo)問題。

現就各種敷設方式下(xia)電纜熱伸縮(suo)對安全運行(xing)帶來的威脅作一(yi)下(xia)簡單(dan)的分析：

（1）直埋敷設時，電(dian)纜(lan)(lan)因受到(dao)周邊土壤的限制，整(zheng)根電(dian)纜(lan)(lan)無(wu)法(fa)產(chan)(chan)生位(wei)移，于是線芯將在熱機械力(li)的作用下在線路的兩(liang)個(ge)末(mo)端產(chan)(chan)生很(hen)大的推力(li)，引起末(mo)端位(wei)移，從(cong)而對(dui)電(dian)纜(lan)(lan)附(fu)件的安(an)全構(gou)成極大威脅。

（2）徘管敷(fu)設時，電(dian)(dian)(dian)纜因不(bu)受到橫(heng)向約束，在熱機(ji)械力的作(zuo)用下電(dian)(dian)(dian)纜將(jiang)產生(sheng)彎(wan)(wan)曲(qu)變(bian)形;電(dian)(dian)(dian)纜隨著電(dian)(dian)(dian)纜溫度的不(bu)斷變(bian)化，彎(wan)(wan)曲(qu)變(bian)形反復出現(xian)，使電(dian)(dian)(dian)纜金屬護套產生(sheng)疲勞(lao)應變(bian)。

（3）隧道敷設時(shi)，電(dian)(dian)纜(lan)(lan)一(yi)般(ban)均放(fang)在(zai)支架上(shang)，不作剛性固(gu)定，故電(dian)(dian)纜(lan)(lan)的熱伸縮較大，在(zai)斜面敷設時(shi)易(yi)出(chu)(chu)現滑落現象;在(zai)電(dian)(dian)纜(lan)(lan)的彎曲(qu)處易(yi)出(chu)(chu)現嚴(yan)重(zhong)位移;電(dian)(dian)纜(lan)(lan)隨(sui)著電(dian)(dian)纜(lan)(lan)溫度的不斷變(bian)化，還會反復(fu)出(chu)(chu)現彎曲(qu)變(bian)形，使電(dian)(dian)纜(lan)(lan)金屬護(hu)套產(chan)生疲(pi)勞應變(bian)。

（4）豎井敷設時，電纜的自重及(ji)熱機械力有可能使(shi)金屬護套(tao)產生過分的應變，從(cong)而縮短電纜的使(shi)用壽命。

（5）市政(zheng)橋(qiao)梁敷(fu)設(she)時(shi)，若電纜敷(fu)設(she)在橋(qiao)內排管中，則存(cun)在與排管敷(fu)設(she)相同(tong)的(de)問題;若電纜敷(fu)設(she)在橋(qiao)的(de)箱梁中，則存(cun)在與隧(sui)道敷(fu)設(she)相同(tong)的(de)。