標準GB50168-92《電(dian)(dian)纜(lan)(lan)線路施(shi)(shi)(shi)工及驗(yan)收規范(fan)》第6.2.3條規定：6kV及以上(shang)電(dian)(dian)力電(dian)(dian)纜(lan)(lan)的終端(duan)和(he)接(jie)頭，尚應(ying)有改善電(dian)(dian)纜(lan)(lan)屏蔽端(duan)部電(dian)(dian)場集(ji)中(zhong)的有效(xiao)措施(shi)(shi)(shi)，并應(ying)確保外絕(jue)緣相間和(he)對(dui)地距離。電(dian)(dian)纜(lan)(lan)終端(duan)的銅屏蔽斷(duan)(duan)口處(chu)(chu)，由于電(dian)(dian)場集(ji)中(zhong)，需要采取繞制半(ban)導體(ti)帶來改善電(dian)(dian)場集(ji)中(zhong)的措施(shi)(shi)(shi)。如果不(bu)采取這些措施(shi)(shi)(shi)，則(ze)會使得運(yun)行中(zhong)電(dian)(dian)纜(lan)(lan)在屏蔽層(ceng)斷(duan)(duan)口處(chu)(chu)因(yin)電(dian)(dian)場集(ji)中(zhong)而引(yin)發(fa)電(dian)(dian)纜(lan)(lan)絕(jue)緣擊穿。

　　目前，半(ban)導(dao)體(ti)(ti)帶的(de)做法(fa)不是釆取繞(rao)制，而(er)是在電纜導(dao)體(ti)(ti)主絕緣(yuan)體(ti)(ti)外粘敷一(yi)層(ceng)(ceng)半(ban)導(dao)體(ti)(ti)膜。這層(ceng)(ceng)半(ban)導(dao)體(ti)(ti)膜是用(yong)于減小(xiao)高壓靜電場(chang)局(ju)部集中(zhong)而(er)發生擊穿。半(ban)導(dao)體(ti)(ti)層(ceng)(ceng)與被屏(ping)蔽的(de)絕緣(yuan)層(ceng)(ceng)有良好接觸(chu)，與金屬護套等電位，從而(er)避免在絕緣(yuan)層(ceng)(ceng)與護套之間發生局(ju)部放電。

　　再者(zhe)，電(dian)(dian)纜(lan)(lan)導(dao)(dao)體是(shi)由多根導(dao)(dao)線絞合而成，它(ta)與絕緣(yuan)層(ceng)(ceng)(ceng)(ceng)之(zhi)間(jian)容易形成氣隙，加上(shang)導(dao)(dao)體表面不光滑，都(dou)會造成電(dian)(dian)場局(ju)部(bu)集(ji)中(zhong)。在導(dao)(dao)體表絕緣(yuan)層(ceng)(ceng)(ceng)(ceng)上(shang)加一層(ceng)(ceng)(ceng)(ceng)半導(dao)(dao)體屏(ping)蔽(bi)(bi)層(ceng)(ceng)(ceng)(ceng)，它(ta)與被(bei)屏(ping)蔽(bi)(bi)的(de)導(dao)(dao)體等電(dian)(dian)位，與絕緣(yuan)層(ceng)(ceng)(ceng)(ceng)有良好的(de)接觸，這就避免了導(dao)(dao)體與絕緣(yuan)層(ceng)(ceng)(ceng)(ceng)之(zhi)間(jian)發(fa)生(sheng)局(ju)部(bu)放電(dian)(dian)。這一層(ceng)(ceng)(ceng)(ceng)屏(ping)蔽(bi)(bi)稱為內(nei)屏(ping)蔽(bi)(bi)層(ceng)(ceng)(ceng)(ceng)。導(dao)(dao)體外側絕緣(yuan)上(shang)沒(mei)有金屬(shu)護套的(de)擠包(bao)電(dian)(dian)纜(lan)(lan)，除半導(dao)(dao)電(dian)(dian)屏(ping)蔽(bi)(bi)層(ceng)(ceng)(ceng)(ceng)外，還要(yao)增加用銅帶或(huo)銅絲繞包(bao)的(de)金屬(shu)屏(ping)蔽(bi)(bi)層(ceng)(ceng)(ceng)(ceng)，作(zuo)用是(shi)在正常運行時(shi)通(tong)過電(dian)(dian)容電(dian)(dian)流;當系統發(fa)生(sheng)短路時(shi)，作(zuo)為短路電(dian)(dian)流的(de)通(tong)道，同時(shi)也起到屏(ping)蔽(bi)(bi)電(dian)(dian)場的(de)作(zuo)用。總(zong)上(shang)可見，如果(guo)電(dian)(dian)纜(lan)(lan)中(zhong)半導(dao)(dao)體層(ceng)(ceng)(ceng)(ceng)和銅屏(ping)蔽(bi)(bi)不存(cun)在，三芯(xin)電(dian)(dian)纜(lan)(lan)芯(xin)間(jian)發(fa)生(sheng)絕緣(yuan)擊穿的(de)可能性非常大。

　　特別需(xu)要指出的是：制(zhi)作電纜(lan)終端或接頭時剝除一段半導體層和屏(ping)(ping)蔽層主要目的是用來(lai)保證(zheng)高壓對地的爬電距離。屏(ping)(ping)蔽斷口處電場(chang)應(ying)力十分集中(zhong)，是薄弱環節!必須采取適當的措施進行(xing)應(ying)力處理。電纜(lan)頭附件設置應(ying)力錐就是為此而設。