局部放電產生的原因及危害

1、局部放電產生的原因

所謂“局(ju)部放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)"是指在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)作(zuo)用(yong)下，絕(jue)(jue)緣(yuan)(yuan)(yuan)(yuan)(yuan)(yuan)系統中(zhong)只有部分區(qu)域發生(sheng)(sheng)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)而(er)并沒有形成貫穿性(xing)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)通道的(de)一種(zhong)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。產生(sheng)(sheng)局(ju)部放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)主要原因是電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)介(jie)(jie)質不均(jun)勻時(shi)，絕(jue)(jue)緣(yuan)(yuan)(yuan)(yuan)(yuan)(yuan)體各(ge)區(qu)域承受的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)強(qiang)度不均(jun)勻，在(zai)(zai)某些(xie)區(qu)域電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)強(qiang)度達(da)到擊(ji)穿場(chang)(chang)強(qiang)而(er)發生(sheng)(sheng)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，而(er)其它(ta)區(qu)域仍(reng)然(ran)保持(chi)絕(jue)(jue)緣(yuan)(yuan)(yuan)(yuan)(yuan)(yuan)的(de)特性(xing)。大型電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)氣(qi)設備的(de)絕(jue)(jue)緣(yuan)(yuan)(yuan)(yuan)(yuan)(yuan)結構比較復雜，使(shi)用(yong)的(de)材料多種(zhong)多樣，整個(ge)絕(jue)(jue)緣(yuan)(yuan)(yuan)(yuan)(yuan)(yuan)系統電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)分布很不均(jun)勻。由(you)于(yu)設計或(huo)制造工藝(yi)上不盡(jin)完善使(shi)絕(jue)(jue)緣(yuan)(yuan)(yuan)(yuan)(yuan)(yuan)系統中(zhong)含有氣(qi)隙(xi)，或(huo)是在(zai)(zai)長期(qi)運(yun)行過程中(zhong)絕(jue)(jue)緣(yuan)(yuan)(yuan)(yuan)(yuan)(yuan)受潮，水分在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)作(zuo)用(yong)下發生(sheng)(sheng)分解產生(sheng)(sheng)氣(qi)體而(er)形成氣(qi)泡(pao)。因為空氣(qi)的(de)介(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)常(chang)數比絕(jue)(jue)緣(yuan)(yuan)(yuan)(yuan)(yuan)(yuan)材料的(de)介(jie)(jie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)常(chang)數小，即使(shi)絕(jue)(jue)緣(yuan)(yuan)(yuan)(yuan)(yuan)(yuan)材料在(zai)(zai)不太高的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)作(zuo)用(yong)下，氣(qi)隙(xi)氣(qi)泡(pao)部位(wei)的(de)場(chang)(chang)強(qiang)也會很高，當(dang)場(chang)(chang)強(qiang)達(da)到一定值后就(jiu)會發生(sheng)(sheng)局(ju)部放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。另(ling)外絕(jue)(jue)緣(yuan)(yuan)(yuan)(yuan)(yuan)(yuan)內部存(cun)在(zai)(zai)缺陷或(huo)混入各(ge)種(zhong)雜質，或(huo)者在(zai)(zai)絕(jue)(jue)緣(yuan)(yuan)(yuan)(yuan)(yuan)(yuan)結構中(zhong)存(cun)在(zai)(zai)某些(xie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)氣(qi)連接(jie)不良，都會使(shi)局(ju)部電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)集中(zhong)，在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)場(chang)(chang)集中(zhong)的(de)地方就(jiu)有可(ke)能發生(sheng)(sheng)固體絕(jue)(jue)緣(yuan)(yuan)(yuan)(yuan)(yuan)(yuan)表面放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)和懸浮電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)。

2、局部放電的類

從局部放電(dian)發生的位置(zhi)、放電(dian)過程和(he)現象來看，局部放電(dian)可(ke)以分為內部放電(dian)、表面放電(dian)和(he)電(dian)暈(yun)放電(dian)三種類(lei)型：

① 內部放電

造成內(nei)部(bu)(bu)局部(bu)(bu)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)常見原(yuan)因是固體(ti)(ti)絕緣體(ti)(ti)內(nei)部(bu)(bu)存(cun)在氣(qi)(qi)隙或(huo)液(ye)體(ti)(ti)絕緣內(nei)部(bu)(bu)存(cun)在氣(qi)(qi)泡(pao)。絕緣內(nei)部(bu)(bu)氣(qi)(qi)隙發生(sheng)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)機理隨氣(qi)(qi)壓和(he)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極系統的(de)(de)(de)變化而(er)異，從(cong)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過程而(er)論，可(ke)分(fen)為電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)子碰撞電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)離放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)和(he)流注放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)兩類；在放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)形(xing)式上可(ke)分(fen)為脈(mo)沖(chong)型(xing)(火(huo)花型(xing))放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)和(he)非脈(mo)沖(chong)型(xing)(輝(hui)光型(xing))放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)兩種基本形(xing)式。一般情(qing)況下，局部(bu)(bu)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)都屬于(yu)脈(mo)沖(chong)型(xing)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，可(ke)以在外加(jia)工(gong)(gong)(gong)頻(pin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓的(de)(de)(de)一定相位(wei)上觀(guan)察(cha)到單個分(fen)離的(de)(de)(de)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)脈(mo)沖(chong)。在理論上，內(nei)部(bu)(bu)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)圖(tu)形(xing)在工(gong)(gong)(gong)頻(pin)正(zheng)、負半波是對(dui)(dui)稱的(de)(de)(de)，但由(you)于(yu)氣(qi)(qi)隙或(huo)氣(qi)(qi)泡(pao)周(zhou)(zhou)圍絕緣材料的(de)(de)(de)絕緣電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻并非理想情(qing)況下的(de)(de)(de)無窮(qiong)大，同(tong)時由(you)于(yu)在放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)中可(ke)能發生(sheng)沿氣(qi)(qi)隙或(huo)氣(qi)(qi)泡(pao)壁表面放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)等原(yuan)因，實際的(de)(de)(de)正(zheng)、負工(gong)(gong)(gong)頻(pin)周(zhou)(zhou)期放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)圖(tu)形(xing)是不完全對(dui)(dui)稱的(de)(de)(de)，而(er)且與電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極系統的(de)(de)(de)形(xing)式有很大的(de)(de)(de)關(guan)系：電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)極系統結構越(yue)對(dui)(dui)稱，正(zheng)、負工(gong)(gong)(gong)頻(pin)周(zhou)(zhou)期放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)圖(tu)形(xing)就越(yue)對(dui)(dui)稱。

② 表面放電

在電(dian)氣(qi)設(she)備的(de)高(gao)電(dian)壓端，由(you)于電(dian)場(chang)集中，沿面放(fang)(fang)電(dian)場(chang)強又比較低(di)，往往會(hui)產生(sheng)表(biao)面局部放(fang)(fang)電(dian)；絕緣體表(biao)面放(fang)(fang)電(dian)的(de)過(guo)程(cheng)及機理(li)與(yu)絕緣內部氣(qi)隙或氣(qi)泡放(fang)(fang)電(dian)的(de)過(guo)程(cheng)及機理(li)相(xiang)似(si)，不(bu)同(tong)的(de)是(shi)放(fang)(fang)電(dian)空間一(yi)端是(shi)絕緣介質，另(ling)一(yi)端是(shi)電(dian)極。如(ru)果電(dian)極系(xi)統是(shi)不(bu)對稱的(de)，發生(sheng)在工頻(pin)正、負(fu)半(ban)波(bo)的(de)放(fang)(fang)電(dian)圖形(xing)(xing)也是(shi)不(bu)對稱的(de)。當放(fang)(fang)電(dian)的(de)一(yi)端是(shi)高(gao)壓電(dian)極，不(bu)放(fang)(fang)電(dian)的(de)電(dian)極接(jie)地時，正半(ban)周放(fang)(fang)電(dian)量大而次數少，負(fu)半(ban)周放(fang)(fang)電(dian)次數多而放(fang)(fang)電(dian)量小。如(ru)果電(dian)極系(xi)統相(xiang)反，則放(fang)(fang)電(dian)圖形(xing)(xing)也相(xiang)反。

③ 電暈放電

電(dian)暈放(fang)(fang)(fang)電(dian)通常發生(sheng)(sheng)在高壓導體周圍完全是氣(qi)體的(de)情況下。由于氣(qi)體中的(de)分子(zi)(zi)自由移動，放(fang)(fang)(fang)電(dian)產(chan)生(sheng)(sheng)的(de)帶電(dian)質點不會固定在空間某(mou)一位(wei)置(zhi)上(shang)。對(dui)于針(zhen)-板電(dian)極(ji)(ji)系統，針(zhen)尖附(fu)近場強(qiang)最高而發生(sheng)(sheng)放(fang)(fang)(fang)電(dian)，由于負極(ji)(ji)性時(shi)(shi)容易(yi)發射電(dian)子(zi)(zi)，同(tong)時(shi)(shi)正離(li)子(zi)(zi)撞擊陰(yin)極(ji)(ji)發生(sheng)(sheng)二次(ci)電(dian)子(zi)(zi)發射，使得放(fang)(fang)(fang)電(dian)在負極(ji)(ji)性時(shi)(shi)最先(xian)出現(xian)(xian)。當外(wai)加電(dian)壓較低(di)時(shi)(shi)，電(dian)暈放(fang)(fang)(fang)電(dian)脈沖出現(xian)(xian)在外(wai)加電(dian)壓負半周90°相(xiang)位(wei)附(fu)近，并幾乎對(dui)稱(cheng)于90°；當電(dian)壓升(sheng)高時(shi)(shi)，正半周會出現(xian)(xian)少量(liang)幅(fu)值大而數(shu)量(liang)少的(de)放(fang)(fang)(fang)電(dian)脈沖。

以上是三種最(zui)基本的局部放(fang)電(dian)形(xing)式(shi)。此(ci)外，絕緣體(ti)中存(cun)在水珠、導電(dian)雜質、電(dian)氣設(she)備(bei)內(nei)部存(cun)在懸(xuan)浮電(dian)位體(ti)也(ye)會引起局部放(fang)電(dian)；液體(ti)絕緣內(nei)部也(ye)可(ke)能出現固體(ti)表(biao)面局部放(fang)電(dian)和電(dian)暈放(fang)電(dian)。

3、局部放電的危害

局(ju)部放電對絕(jue)緣結構起著一種侵(qin)蝕作用，它對絕(jue)緣的破(po)壞機理有以下幾個方面：

① 帶電粒子(zi)(電子(zi)、離(li)子(zi)等)沖擊絕(jue)緣，破壞(huai)其分子(zi)結構，如纖維碎(sui)裂，因(yin)而絕(jue)緣受到損傷(shang)；

② 由于帶(dai)電(dian)離(li)子的撞擊作用(yong)，使該絕緣出(chu)現局部溫(wen)度升高，從而(er)易引(yin)起絕緣的過熱，嚴重時就會出(chu)現碳化；

③ 局部放電產生(sheng)的(de)臭氧(O3)及氮的(de)氧化(hua)物(NO、NO2)會(hui)侵蝕絕(jue)緣，當遇有水分則(ze)產生(sheng)硝酸，對絕(jue)緣的(de)侵蝕更為劇烈(lie)；

④ 在局部放(fang)電時，油(you)因電解及電極的(de)(de)肖特(te)基輻射效應使(shi)油(you)分解，加上油(you)中原(yuan)來存在些(xie)雜質，故(gu)易使(shi)紙(zhi)層處(chu)凝集著因聚合作用生成(cheng)的(de)(de)油(you)泥(ni)(多在匝(za)絕(jue)(jue)緣或其他絕(jue)(jue)緣的(de)(de)油(you)楔處(chu))，油(you)泥(ni)生成(cheng)將(jiang)使(shi)絕(jue)(jue)緣的(de)(de)介質損傷(shang)角tgδ激增，散熱能(neng)力降(jiang)低，甚至導致(zhi)熱擊(ji)穿(chuan)的(de)(de)可能(neng)性。局部放(fang)電的(de)(de)持續發展會使(shi)絕(jue)(jue)緣的(de)(de)劣化損傷(shang)逐步擴大(da)，最(zui)終使(shi)絕(jue)(jue)緣正(zheng)常(chang)壽命縮短、短時絕(jue)(jue)緣強(qiang)度降(jiang)低，甚至可能(neng)使(shi)整個絕(jue)(jue)緣擊(ji)穿(chuan)。

發布時間:2021-7-16 訪問次數:1400