影響介電擊穿強度的因素有哪些?
影響介電擊(ji)穿強度(du)的因素有哪些?
閃絡(luo)-指高(gao)壓電器（如高(gao)壓絕(jue)緣子）在絕(jue)緣表(biao)面發生的放(fang)電現象，成為(wei)表(biao)面閃絡，簡稱(cheng)閃絡。
絕(jue)緣(yuan)閃絡：絕(jue)緣(yuan)材(cai)料(liao)在(zai)(zai)電(dian)(dian)場作用下，尚(shang)未發(fa)(fa)生絕(jue)緣(yuan)結構的(de)擊穿時，在(zai)(zai)其表(biao)面或與電(dian)(dian)極接觸的(de)空氣(qi)（離子化(hua)氣(qi)體）中發(fa)(fa)生的(de)放電(dian)(dian)現(xian)象，成(cheng)為絕(jue)緣(yuan)閃絡。
1.電壓波形直流(liu)、工頻(pin)正弦及沖擊電壓下，擊穿機理(li)不同(tong)(tong)，所測的擊穿場強也不同(tong)(tong)，工頻(pin)交(jiao)流(liu)電壓下的擊穿場強比直流(liu)和沖擊電壓下的低(di)得(de)多
2..電(dian)壓(ya)(ya)(ya)作用時(shi)間，無論電(dian)擊(ji)穿(chuan)(chuan)還是熱擊(ji)穿(chuan)(chuan)都需要(yao)時(shi)間，隨著(zhu)加壓(ya)(ya)(ya)時(shi)間的增長(chang)，擊(ji)穿(chuan)(chuan)電(dian)壓(ya)(ya)(ya)明顯下(xia)降。
3、電(dian)場(chang)的均勻性(xing)及電(dian)壓的極性(xing)，電(dian)場(chang)不均勻往往測得的電(dian)壓比本征擊穿(chuan)值(zhi)低。
4、試(shi)樣(yang)的厚度與不均勻性試(shi)樣(yang)的厚度增加，電極邊緣電場就更不均勻，試(shi)樣(yang)內部的熱量(liang)更不易散發，試(shi)樣(yang)內部的含有缺陷(xian)的幾率(lv)增大，這(zhe)些(xie)都會(hui)使擊(ji)穿場強下降。
5.環(huan)境條件試(shi)樣周圍(wei)的(de)環(huan)境條件，如溫(wen)度、濕度以及(ji)(ji)壓(ya)力等(deng)都會影(ying)響試(shi)樣的(de)擊穿(chuan)(chuan)場強(qiang)(qiang)(qiang)；溫(wen)度升(sheng)高，通常會使(shi)擊穿(chuan)(chuan)場強(qiang)(qiang)(qiang)下降；濕度增大，會使(shi)擊穿(chuan)(chuan)場強(qiang)(qiang)(qiang)下降；氣(qi)壓(ya)對擊穿(chuan)(chuan)場強(qiang)(qiang)(qiang)的(de)影(ying)響，主要是對氣(qi)體而言。氣(qi)壓(ya)高，擊穿(chuan)(chuan)場強(qiang)(qiang)(qiang)升(sheng)高：但接近真空時，也會使(shi)擊穿(chuan)(chuan)場強(qiang)(qiang)(qiang)升(sheng)高。另外還有：時間、輻射、機械(xie)力、電極(ji)材料及(ji)(ji)極(ji)性效應(ying)。
在強電(dian)(dian)場作用下，電(dian)(dian)介質喪失(shi)電(dian)(dian)絕緣能(neng)力的現(xian)象(xiang)。分為固體(ti)電(dian)(dian)介質擊穿(chuan)、液體(ti)電(dian)(dian)介質擊穿(chuan)和氣體(ti)電(dian)(dian)介質擊穿(chuan)3種。
固體電介質(zhi)擊穿導(dao)致擊穿的(de)zui低(di)(di)臨界(jie)電(dian)(dian)(dian)壓稱(cheng)(cheng)為擊(ji)(ji)穿(chuan)電(dian)(dian)(dian)壓。均勻電(dian)(dian)(dian)場(chang)中(zhong)(zhong)，擊(ji)(ji)穿(chuan)電(dian)(dian)(dian)壓與(yu)介(jie)質(zhi)厚(hou)度(du)(du)之比(bi)稱(cheng)(cheng)為擊(ji)(ji)穿(chuan)電(dian)(dian)(dian)場(chang)強(qiang)度(du)(du)（簡稱(cheng)(cheng)擊(ji)(ji)穿(chuan)場(chang)強(qiang)，又稱(cheng)(cheng)介(jie)電(dian)(dian)(dian)強(qiang)度(du)(du)）。它反映固體電(dian)(dian)(dian)介(jie)質(zhi)自身的耐(nai)電(dian)(dian)(dian)強(qiang)度(du)(du)。不均勻電(dian)(dian)(dian)場(chang)中(zhong)(zhong)，擊(ji)(ji)穿(chuan)電(dian)(dian)(dian)壓與(yu)擊(ji)(ji)穿(chuan)處介(jie)質(zhi)厚(hou)度(du)(du)之比(bi)稱(cheng)(cheng)為平均擊(ji)(ji)穿(chuan)場(chang)強(qiang)，它低(di)(di)于均勻電(dian)(dian)(dian)場(chang)中(zhong)(zhong)固體介(jie)質(zhi)的介(jie)電(dian)(dian)(dian)強(qiang)度(du)(du)。固體介(jie)質(zhi)擊(ji)(ji)穿(chuan)后，由于有巨大(da)電(dian)(dian)(dian)流通過，介(jie)質(zhi)中(zhong)(zhong)會出現(xian)熔化或燒(shao)焦(jiao)的通道，或出現(xian)裂(lie)紋(wen)。脆性介(jie)質(zhi)擊(ji)(ji)穿(chuan)時，常發生材料的碎裂(lie)，可據(ju)此破碎非金(jin)屬礦(kuang)石。固體電(dian)(dian)(dian)介(jie)質(zhi)擊(ji)(ji)穿(chuan)有3種形式：電(dian)(dian)擊(ji)穿(chuan)、熱(re)擊(ji)穿(chuan)和電(dian)(dian)化學(xue)擊(ji)穿(chuan)。電(dian)(dian)擊(ji)穿(chuan)是因(yin)電(dian)(dian)場(chang)使電(dian)(dian)介質(zhi)中積聚(ju)起足夠數(shu)量(liang)(liang)和能(neng)量(liang)(liang)的帶電(dian)(dian)質(zhi)點而(er)導致(zhi)電(dian)(dian)介質(zhi)失去(qu)絕緣(yuan)性(xing)能(neng)。熱(re)擊(ji)穿(chuan)是因(yin)在電(dian)(dian)場(chang)作(zuo)用(yong)下，電(dian)(dian)介質(zhi)內部熱(re)量(liang)(liang)積累、溫度(du)過高而(er)導致(zhi)失去(qu)絕緣(yuan)能(neng)力。電(dian)(dian)化學(xue)擊(ji)穿(chuan)是在電(dian)(dian)場(chang)、溫度(du)等(deng)因(yin)素作(zuo)用(yong)下，電(dian)(dian)介質(zhi)發(fa)生緩(huan)慢的化學(xue)變化，性(xing)能(neng)逐漸(jian)劣化，zui終(zhong)喪失(shi)絕緣能力。固體(ti)電介(jie)質的(de)化(hua)學變化(hua)通常(chang)使其(qi)電導增加，這(zhe)會(hui)使介(jie)質的(de)溫度上升，因(yin)而電化(hua)學擊穿的(de)zui終(zhong)形式是熱擊(ji)穿(chuan)。溫度和(he)電(dian)壓(ya)作用(yong)時間(jian)對(dui)電(dian)擊(ji)穿(chuan)的影響小，對(dui)熱擊(ji)穿(chuan)和(he)電(dian)化學擊(ji)穿(chuan)的影響大(da)；電(dian)場局部不(bu)均勻(yun)性對(dui)熱擊(ji)穿(chuan)的影響小，對(dui)其他兩(liang)種影響大(da)。
液(ye)體(ti)(ti)(ti)(ti)電(dian)(dian)(dian)介(jie)質(zhi)(zhi)擊(ji)(ji)(ji)(ji)穿(chuan)(chuan)純凈(jing)液(ye)體(ti)(ti)(ti)(ti)電(dian)(dian)(dian)介(jie)質(zhi)(zhi)與含雜質(zhi)(zhi)的(de)(de)工程液(ye)體(ti)(ti)(ti)(ti)電(dian)(dian)(dian)介(jie)質(zhi)(zhi)的(de)(de)擊(ji)(ji)(ji)(ji)穿(chuan)(chuan)機理不(bu)(bu)同。對(dui)前者主要有電(dian)(dian)(dian)擊(ji)(ji)(ji)(ji)穿(chuan)(chuan)理論(lun)和(he)(he)氣泡擊(ji)(ji)(ji)(ji)穿(chuan)(chuan)理論(lun)，對(dui)后者有氣體(ti)(ti)(ti)(ti)橋擊(ji)(ji)(ji)(ji)穿(chuan)(chuan)理論(lun)。沿液(ye)體(ti)(ti)(ti)(ti)和(he)(he)固(gu)體(ti)(ti)(ti)(ti)電(dian)(dian)(dian)介(jie)質(zhi)(zhi)分界面的(de)(de)放(fang)電(dian)(dian)(dian)現(xian)象(xiang)稱為(wei)液(ye)體(ti)(ti)(ti)(ti)電(dian)(dian)(dian)介(jie)質(zhi)(zhi)中的(de)(de)沿面放(fang)電(dian)(dian)(dian)。這種放(fang)電(dian)(dian)(dian)不(bu)(bu)僅(jin)使液(ye)體(ti)(ti)(ti)(ti)變質(zhi)(zhi)，而且放(fang)電(dian)(dian)(dian)產生(sheng)的(de)(de)熱作用(yong)和(he)(he)劇(ju)烈的(de)(de)壓力變化可能使固(gu)體(ti)(ti)(ti)(ti)介(jie)質(zhi)(zhi)內(nei)產生(sheng)氣泡。經多次作用(yong)會使固(gu)體(ti)(ti)(ti)(ti)介(jie)質(zhi)(zhi)出現(xian)分層、開(kai)裂現(xian)象(xiang)，放(fang)電(dian)(dian)(dian)有可能在固(gu)體(ti)(ti)(ti)(ti)介(jie)質(zhi)(zhi)內(nei)發(fa)展(zhan)，絕緣結(jie)構的(de)(de)擊(ji)(ji)(ji)(ji)穿(chuan)(chuan)電(dian)(dian)(dian)壓因此(ci)下降。脈沖電(dian)(dian)(dian)壓下液(ye)體(ti)(ti)(ti)(ti)電(dian)(dian)(dian)介(jie)質(zhi)(zhi)擊(ji)(ji)(ji)(ji)穿(chuan)(chuan)時(shi)，常(chang)出現(xian)強力氣體(ti)(ti)(ti)(ti)沖擊(ji)(ji)(ji)(ji)波（即(ji)電(dian)(dian)(dian)水錘），可用(yong)于水下探礦、橋墩探傷及(ji)人體(ti)(ti)(ti)(ti)內(nei)臟結(jie)石(shi)的(de)(de)體(ti)(ti)(ti)(ti)外破碎(sui)。
氣(qi)(qi)體(ti)電(dian)(dian)介(jie)質擊穿(chuan)(chuan)(chuan)在(zai)電(dian)(dian)場(chang)作(zuo)用下氣(qi)(qi)體(ti)分子發生碰撞電(dian)(dian)離而導致電(dian)(dian)極間(jian)(jian)的(de)貫穿(chuan)(chuan)(chuan)性(xing)放(fang)電(dian)(dian)。其影響因素很(hen)多(duo)，主要有作(zuo)用電(dian)(dian)壓(ya)、電(dian)(dian)板形狀(zhuang)、氣(qi)(qi)體(ti)的(de)性(xing)質及狀(zhuang)態等。氣(qi)(qi)體(ti)介(jie)質擊穿(chuan)(chuan)(chuan)常見的(de)有直流(liu)電(dian)(dian)壓(ya)擊穿(chuan)(chuan)(chuan)、工(gong)頻電(dian)(dian)壓(ya)擊穿(chuan)(chuan)(chuan)、高(gao)氣(qi)(qi)壓(ya)電(dian)(dian)擊穿(chuan)(chuan)(chuan)、沖(chong)擊電(dian)(dian)壓(ya)擊穿(chuan)(chuan)(chuan)、高(gao)真空電(dian)(dian)擊穿(chuan)(chuan)(chuan)、負(fu)電(dian)(dian)性(xing)氣(qi)(qi)體(ti)擊穿(chuan)(chuan)(chuan)等。空氣(qi)(qi)是很(hen)好的(de)氣(qi)(qi)體(ti)絕(jue)緣材(cai)料，電(dian)(dian)離場(chang)強和擊穿(chuan)(chuan)(chuan)場(chang)強高(gao)，擊穿(chuan)(chuan)(chuan)后能迅(xun)速恢復絕(jue)緣性(xing)能，且不(bu)燃、不(bu)爆(bao)、不(bu)老(lao)化、無腐蝕性(xing)，因而得到廣泛應(ying)用。為(wei)提供高(gao)電(dian)(dian)壓(ya)輸電(dian)(dian)線或變電(dian)(dian)所的(de)空氣(qi)(qi)間(jian)(jian)隙距(ju)離的(de)設計依據（高(gao)壓(ya)輸電(dian)(dian)線應(ying)離地(di)面(mian)多(duo)高(gao)等），需(xu)進行長空氣(qi)(qi)間(jian)(jian)隙的(de)工(gong)頻擊穿(chuan)(chuan)(chuan)試(shi)驗(yan)。
