高壓(ya)電(dian)纜(lan)直流耐壓(ya)試驗(yan)的(de)問題。高壓(ya)及超(chao)高壓(ya)電(dian)纜(lan)已成為現代城(cheng)市電(dian)網項(xiang)目工程中不(bu)可或缺(que)的(de)材(cai)料，但我國高壓(ya)超(chao)高壓(ya)電(dian)纜(lan)領域起步晚，材(cai)料、設備及制(zhi)造(zao)技術(shu)長期以(yi)來主要依賴(lai)引(yin)進和模仿。
高壓電(dian)纜進行直流耐壓試(shi)驗(yan)的問題
隨著國(guo)家"西電(dian)(dian)東送"、"南電(dian)(dian)北(bei)送"等工程(cheng)的推進，高(gao)壓(ya)直(zhi)(zhi)流(liu)電(dian)(dian)纜將成被應用的主(zhu)力軍。新(xin)能(neng)源規模化接入及城(cheng)市輸電(dian)(dian)的電(dian)(dian)纜化建(jian)設(she)，都需要應用高(gao)壓(ya)直(zhi)(zhi)流(liu)電(dian)(dian)纜。高(gao)壓(ya)直(zhi)(zhi)流(liu)電(dian)(dian)纜更是海上(shang)風電(dian)(dian)、海上(shang)孤島的唯(wei)一輸電(dian)(dian)手段。
高(gao)(gao)壓(ya)及超高(gao)(gao)壓(ya)電纜(lan)(lan)已成(cheng)為(wei)現代城(cheng)市電網項目工程中不可或缺(que)的材料(liao)(liao)，但我國高(gao)(gao)壓(ya)超高(gao)(gao)壓(ya)電纜(lan)(lan)領域起步晚，材料(liao)(liao)、設備(bei)及制造(zao)技術長期以來(lai)主(zhu)要依(yi)賴引進和模仿。下面我們(men)就來(lai)說說，高(gao)(gao)壓(ya)電纜(lan)(lan)進行直流耐(nai)壓(ya)試(shi)驗的問題主(zhu)要表(biao)現在(zai)哪些個方面？
1.直(zhi)(zhi)流(liu)(liu)電(dian)(dian)(dian)(dian)壓下(xia)，電(dian)(dian)(dian)(dian)纜絕緣(yuan)的(de)(de)(de)電(dian)(dian)(dian)(dian)場(chang)(chang)分(fen)布取決(jue)(jue)于材料的(de)(de)(de)體積(ji)電(dian)(dian)(dian)(dian)阻(zu)率，而(er)交(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)壓下(xia)的(de)(de)(de)電(dian)(dian)(dian)(dian)場(chang)(chang)分(fen)布取決(jue)(jue)于各介(jie)質的(de)(de)(de)介(jie)電(dian)(dian)(dian)(dian)常(chang)數，特(te)別是在(zai)電(dian)(dian)(dian)(dian)纜終(zhong)端頭、接(jie)頭盒(he)等電(dian)(dian)(dian)(dian)纜附件(jian)中的(de)(de)(de)直(zhi)(zhi)流(liu)(liu)電(dian)(dian)(dian)(dian)場(chang)(chang)強度(du)的(de)(de)(de)分(fen)布和(he)交(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)場(chang)(chang)強度(du)的(de)(de)(de)分(fen)布完全(quan)不(bu)同，而(er)且直(zhi)(zhi)流(liu)(liu)電(dian)(dian)(dian)(dian)壓下(xia)絕緣(yuan)老化(hua)的(de)(de)(de)機理和(he)交(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)壓下(xia)的(de)(de)(de)老化(hua)機理不(bu)相(xiang)同。因此(ci)，直(zhi)(zhi)流(liu)(liu)耐(nai)壓試(shi)驗(yan)不(bu)能模擬(ni)高壓電(dian)(dian)(dian)(dian)纜的(de)(de)(de)運行工(gong)況。
2.高壓(ya)(ya)(ya)(ya)電(dian)纜在(zai)直(zhi)流電(dian)壓(ya)(ya)(ya)(ya)下會產生"記憶"效應，存儲積(ji)累單極性殘余電(dian)荷。一(yi)旦有了由于直(zhi)流耐壓(ya)(ya)(ya)(ya)試驗引起(qi)的(de)"記憶性"，需要很(hen)長時(shi)間才能將(jiang)這種直(zhi)流偏(pian)壓(ya)(ya)(ya)(ya)釋放(fang)。電(dian)纜如果在(zai)直(zhi)流殘余電(dian)荷未完(wan)全(quan)釋放(fang)之前投入運行(xing)，直(zhi)流偏(pian)壓(ya)(ya)(ya)(ya)便(bian)會疊(die)加在(zai)工頻電(dian)壓(ya)(ya)(ya)(ya)峰值上，使得電(dian)纜上的(de)電(dian)壓(ya)(ya)(ya)(ya)值遠遠超(chao)過其額定電(dian)壓(ya)(ya)(ya)(ya)，從而有可能導(dao)致(zhi)電(dian)纜絕緣擊(ji)穿。
3.直流耐(nai)壓試(shi)驗(yan)時，會有電(dian)(dian)子(zi)注入(ru)到聚合物介質內部，形成空(kong)(kong)間電(dian)(dian)荷(he)，使(shi)該(gai)處的電(dian)(dian)場(chang)強度(du)降低，從而難于發生擊穿。高壓電(dian)(dian)纜的半導體凸出處和(he)污穢點(dian)等(deng)處容易產(chan)生空(kong)(kong)間電(dian)(dian)荷(he)。但如(ru)果在試(shi)驗(yan)時電(dian)(dian)纜終端(duan)頭發生表(biao)面閃絡或電(dian)(dian)纜附(fu)件擊穿，會造成電(dian)(dian)纜芯線上產(chan)生波振蕩，在已積聚空(kong)(kong)間電(dian)(dian)荷(he)的地點(dian)，由于振蕩電(dian)(dian)壓極性迅速(su)改變為異(yi)極性，使(shi)該(gai)處電(dian)(dian)場(chang)強度(du)顯著增(zeng)大(da)，可能損壞(huai)絕緣，造成多(duo)點(dian)擊穿。
4.高壓(ya)電(dian)纜(lan)致(zhi)命(ming)的(de)(de)一(yi)個弱點(dian)是絕(jue)緣(yuan)內易(yi)產(chan)生水(shui)樹(shu)枝(zhi)，一(yi)旦產(chan)生水(shui)樹(shu)枝(zhi)，在(zai)直流電(dian)壓(ya)下(xia)會(hui)迅速轉變為電(dian)樹(shu)枝(zhi)，并形成(cheng)放電(dian)，加速了絕(jue)緣(yuan)劣化，以(yi)致(zhi)于(yu)運行后在(zai)工頻電(dian)壓(ya)作用下(xia)形成(cheng)擊穿(chuan)。而單純的(de)(de)水(shui)樹(shu)枝(zhi)在(zai)交流工作電(dian)壓(ya)下(xia)還能保(bao)持相當(dang)的(de)(de)耐壓(ya)值，并能保(bao)持一(yi)段時間。
生(sheng)命安全高于一切，高壓低壓耐火電纜因(yin)其獨特優勢在高層建筑、地(di)下鐵道、地(di)下街、大(da)型電站及重(zhong)要的工礦(kuang)企業等與防火安全和消(xiao)防救生(sheng)有關的地(di)方得到廣泛應用。
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