電氣火(huo)災發生的原(yuan)因是多種多樣(yang)的,例如過載、短路、接觸不良、電(dian)(dian)弧火花、漏電(dian)(dian)、雷電(dian)(dian)或(huo)靜電(dian)(dian)等(deng)都能引起(qi)火災。有(you)的(de)火災是(shi)人(ren)為的(de),比如:思想麻(ma)痹、疏(shu)忽大意、不遵(zun)守有(you)關防火法規、違(wei)犯操作規程等(deng)。從電(dian)(dian)氣(qi)防火角度看,電(dian)(dian)氣(qi)設備短路、安裝使用不當、保養不良、雷擊和靜電(dian)(dian)是(shi)造成電(dian)(dian)氣(qi)火災的(de)幾個重要原因。

　　1、短(duan)(duan)路(lu)(lu)、電弧和火花(hua)凡電流未(wei)經一定(ding)的(de)用電負載、阻抗或(huo)(huo)未(wei)按規定(ding)路(lu)(lu)徑而(er)就近自成通路(lu)(lu)的(de)狀(zhuang)態(tai)，稱為(wei)短(duan)(duan)路(lu)(lu)。如幾條(tiao)相(xiang)(xiang)線(xian)直接碰觸在(zai)一起，或(huo)(huo)者中性點接地系統的(de)相(xiang)(xiang)線(xian)與零線(xian)或(huo)(huo)大地相(xiang)(xiang)碰等(deng)。此(ci)時(shi)導線(xian)的(de)發(fa)熱(re)量(liang)劇增，不僅能使絕緣燃(ran)(ran)燒，而(er)且(qie)還會使金屬熔化或(huo)(huo)引起鄰近的(de)易燃(ran)(ran)、可燃(ran)(ran)物質燃(ran)(ran)燒釀成火災。短(duan)(duan)路(lu)(lu)是(shi)電氣(qi)設備(bei)最嚴(yan)重的(de)一種故障狀(zhuang)態(tai)，發(fa)生短(duan)(duan)路(lu)(lu)的(de)原因主要有：

　　(1)、電氣設(she)備的選用(yong)和安裝與使用(yong)環境不符,致使其絕(jue)緣體(ti)在高溫、潮濕、酸堿環境條(tiao)件下(xia)受到破(po)壞;

　　(2)、電(dian)氣(qi)設備使(shi)用(yong)時間過長,超過使(shi)用(yong)壽命,絕緣(yuan)老化發脆;

　　(3)、使(shi)用維護不當,長期(qi)帶病(bing)運行,擴大了故障范圍;

　　(4)、過(guo)電壓使絕緣擊穿(chuan);

　　(5)、錯誤操作或(huo)(huo)把電(dian)(dian)源投向故障線路。短路時(shi),在短路點或(huo)(huo)導線連(lian)接(jie)(jie)(jie)松弛(chi)的(de)電(dian)(dian)氣(qi)接(jie)(jie)(jie)頭處,會產生(sheng)(sheng)電(dian)(dian)弧(hu)(hu)(hu)或(huo)(huo)火花.電(dian)(dian)弧(hu)(hu)(hu)溫(wen)度很高,可達 6000 ℃以上,不(bu)(bu)但可引燃它本(ben)身的(de)絕緣(yuan)材(cai)料(liao),還可將它附(fu)近(jin)的(de)可燃材(cai)料(liao),蒸氣(qi)和粉塵引燃。電(dian)(dian)弧(hu)(hu)(hu)還可能(neng)是由于接(jie)(jie)(jie)地(di)裝(zhuang)(zhuang)置(zhi)不(bu)(bu)良(liang)或(huo)(huo)電(dian)(dian)氣(qi)設(she)備與接(jie)(jie)(jie)地(di)裝(zhuang)(zhuang)置(zhi)間(jian)距(ju)過(guo)小(xiao),過(guo)電(dian)(dian)壓時(shi)使空氣(qi)擊(ji)穿引起。切斷或(huo)(huo)接(jie)(jie)(jie)通大(da)電(dian)(dian)流電(dian)(dian)路時(shi)，或(huo)(huo)大(da)截面(mian)熔斷器(qi)爆斷時(shi),也能(neng)產生(sheng)(sheng)電(dian)(dian)弧(hu)(hu)(hu)。

　　2、電(dian)(dian)氣(qi)設(she)備(bei)過負(fu)荷(he)(he)當電(dian)(dian)流通過導(dao)線(xian)時，由于導(dao)線(xian)有電(dian)(dian)阻存在，便會引起(qi)導(dao)線(xian)發(fa)熱。所謂(wei)過負(fu)荷(he)(he)(即過載),是(shi)指電(dian)(dian)氣(qi)設(she)備(bei)或(huo)導(dao)線(xian)的功率和電(dian)(dian)流超過了其(qi)額(e)定值。發(fa)生(sheng)設(she)備(bei)過負(fu)荷(he)(he)的原因主(zhu)要有：

　　(1)、設(she)(she)計(ji)、安裝時(shi)選(xuan)型(xing)不正確,使電氣(qi)設(she)(she)備(bei)的額定容(rong)量(liang)小于實(shi)際(ji)負載容(rong)量(liang);

　　(2)、導線截(jie)面選(xuan)得過細，與負荷電(dian)流(liu)值(zhi)不(bu)相(xiang)適應;

　　(3)、亂拉電(dian)(dian)(dian)線，過(guo)多(duo)地接入(ru)用電(dian)(dian)(dian)負載(zai)。電(dian)(dian)(dian)氣設(she)備或導線的(de)絕緣(yuan)材(cai)(cai)料,大(da)都(dou)是(shi)可燃材(cai)(cai)料。屬于有機絕緣(yuan)材(cai)(cai)料的(de)有油(you),紙,麻,絲和(he)棉的(de)紡織品,樹(shu)脂,瀝青,漆,塑料,橡膠等(deng)(deng)。只有少數(shu)屬于無機材(cai)(cai)料,例如陶瓷,石(shi)棉和(he)云(yun)母等(deng)(deng)是(shi)不易燃材(cai)(cai)料.過(guo)載(zai)使導體中的(de)電(dian)(dian)(dian)能轉變成熱能,當導體和(he)絕緣(yuan)物局部過(guo)熱,達到一(yi)定溫度時,就會引起火災。我(wo)國不乏(fa)這樣的(de)慘(can)痛教(jiao)訓:電(dian)(dian)(dian)線電(dian)(dian)(dian)纜上(shang)面的(de)木裝板被過(guo)載(zai)電(dian)(dian)(dian)流引燃 , 釀成商店,劇(ju)院和(he)場所(suo)的巨大(da)火(huo)災。

　　3、電(dian)氣設(she)備絕(jue)緣損壞或老(lao)(lao)化絕(jue)緣損壞或老(lao)(lao)化會(hui)使絕(jue)緣性能降低甚至(zhi)喪失，從而造成短路引發火災(zai)。引起絕(jue)緣老(lao)(lao)化的原(yuan)因主(zhu)要有：

　　(1)、電氣(qi)因素絕緣物局部放電;操(cao)作過(guo)電壓(ya)(ya)或雷擊過(guo)電壓(ya)(ya);事故或過(guo)負荷(he)的過(guo)電流(liu)等(deng)。

　　(2)、機械因素(su)旋轉部分、滑動部分、操作(zuo)過(guo)(guo)電壓(ya)或(huo)雷擊過(guo)(guo)電壓(ya);事故或(huo)過(guo)(guo)負荷的過(guo)(guo)電流等(deng)。

　　(3)、熱(re)因素溫(wen)升(sheng)過高使絕緣(yuan)物熱(re)分(fen)解(jie)、氧化等的化學變化、氣化、硬化、龜裂、脆(cui)化;設備反復起動停止(zhi)溫(wen)升(sheng)溫(wen)降的熱(re)循環，使結(jie)構材料間因熱(re)膨脹(zhang)系數不同產生(sheng)應力(li)等。

　　(4)、環境(jing)因(yin)素周(zhou)圍(wei)有害物質(zhi)(煤氣、油(you)、藥品等)的腐蝕;陽光、紫外線(xian)長(chang)期照射和氧(yang)化作用;老鼠、白蟻等咬壞電線(xian)、電纜，以(yi)及水浸等。

　　(5)、人為因素施工不良、維護保養不善或設(she)備選型不當(dang)等(deng)。

　　4、電(dian)(dian)(dian)(dian)氣(qi)連(lian)接(jie)點(dian)接(jie)觸(chu)電(dian)(dian)(dian)(dian)阻(zu)過大在(zai)電(dian)(dian)(dian)(dian)氣(qi)回路中有許多連(lian)接(jie)點(dian)，這些(xie)電(dian)(dian)(dian)(dian)氣(qi)連(lian)接(jie)點(dian)不(bu)可(ke)避免地產(chan)生一定的(de)電(dian)(dian)(dian)(dian)阻(zu)，這個電(dian)(dian)(dian)(dian)阻(zu)叫做接(jie)觸(chu)電(dian)(dian)(dian)(dian)阻(zu)。正常時接(jie)觸(chu)電(dian)(dian)(dian)(dian)阻(zu)是(shi)很小的(de)，可(ke)以忽略不(bu)計(ji)。但不(bu)正常時，接(jie)觸(chu)電(dian)(dian)(dian)(dian)阻(zu)顯(xian)著增大，使這些(xie)部(bu)位局部(bu)過熱，金屬變色甚至(zhi)熔化，并能引起絕緣材料、可(ke)燃(ran)物(wu)質的(de)燃(ran)燒。電(dian)(dian)(dian)(dian)氣(qi)連(lian)接(jie)點(dian)接(jie)觸(chu)電(dian)(dian)(dian)(dian)阻(zu)過大的(de)原(yuan)因主(zhu)要有：

　　(1)、銅(tong)、鋁相接并處理不好

　　銅鋁連接處,因有約(yue) 1.69V 電位差的存在,潮(chao)濕(shi)時會發生電解作用,使鋁(lv)腐蝕,造成接觸不(bu)良。

　　(2)、接(jie)點連(lian)接(jie)松(song)弛

　　螺栓或螺母未擰緊，使(shi)兩導體間(jian)接(jie)觸不緊密，尤其在有塵(chen)埃的環境(jing)中，接(jie)觸電(dian)阻(zu)顯著增大。當電(dian)流(liu)流(liu)過時，接(jie)頭發熱，甚(shen)至產(chan)生火花(hua)。

　　(3)、烘烤(kao)電(dian)(dian)熱器(qi)具(ju) ( 如電(dian)(dian)爐,電(dian)(dian)熨斗等(deng)),照(zhao)明燈泡(pao),在正(zheng)常通電(dian)(dian)的狀態下(xia),就相(xiang)當(dang)于一個火源或高(gao)(gao)溫熱源。當(dang)其安裝不(bu)當(dang)或長(chang)期通電(dian)(dian)無人(ren)監護管(guan)理時,就可能使附近的可燃物受高(gao)(gao)溫而起火。

　　(4)、摩擦發(fa)電(dian)機和電(dian)動(dong)機等旋轉型電(dian)氣(qi)設備(bei),軸承出現潤滑不良(liang),干(gan)(gan)枯產生(sheng)干(gan)(gan)磨發(fa)熱或雖潤滑正常,但出現高速旋轉時(shi),都(dou)會引起火災。

　　(5)、雷(lei)(lei)(lei)(lei)電(dian)(dian)(dian)(dian)(dian) 雷(lei)(lei)(lei)(lei)電(dian)(dian)(dian)(dian)(dian)是在大(da)氣中產生的(de)(de)(de)(de),雷(lei)(lei)(lei)(lei)云(yun)是大(da)氣電(dian)(dian)(dian)(dian)(dian)荷(he)的(de)(de)(de)(de)載體(ti),當雷(lei)(lei)(lei)(lei)云(yun)與地面建筑物或構筑物接近到一定(ding)距離時,雷(lei)(lei)(lei)(lei)云(yun)高(gao)電(dian)(dian)(dian)(dian)(dian)位(wei)就(jiu)會把(ba)空氣擊穿放(fang)電(dian)(dian)(dian)(dian)(dian),產生閃電(dian)(dian)(dian)(dian)(dian)、雷(lei)(lei)(lei)(lei)鳴現象。雷(lei)(lei)(lei)(lei)云(yun)電(dian)(dian)(dian)(dian)(dian)位(wei)可達 1 萬(wan)～10 萬(wan) kV, 雷(lei)(lei)(lei)(lei)電(dian)(dian)(dian)(dian)(dian)流(liu)可達 5OKA, 若(ruo)以0.00001s 的(de)(de)(de)(de)時間(jian)放(fang)電(dian)(dian)(dian)(dian)(dian),其(qi)放(fang)電(dian)(dian)(dian)(dian)(dian)能(neng)(neng)量(liang)(liang)約(yue)為 107J(107W?s),這(zhe)(zhe)個能(neng)(neng)量(liang)(liang)約(yue)為使人致(zhi)死(si)或易(yi)燃易(yi)爆物質點火(huo)能(neng)(neng)量(liang)(liang)的(de)(de)(de)(de) 100 萬(wan)倍(bei),足(zu)可使人死(si)亡或引起火(huo)災。雷(lei)(lei)(lei)(lei)電(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)危(wei)害類型(xing)除直擊雷(lei)(lei)(lei)(lei)外,還(huan)有(you)感(gan)應(ying)雷(lei)(lei)(lei)(lei) ( 含(han)靜電(dian)(dian)(dian)(dian)(dian)和電(dian)(dian)(dian)(dian)(dian)磁感(gan)應(ying) ),雷(lei)(lei)(lei)(lei)電(dian)(dian)(dian)(dian)(dian)反擊,雷(lei)(lei)(lei)(lei)電(dian)(dian)(dian)(dian)(dian)波(bo)的(de)(de)(de)(de)侵入和球雷(lei)(lei)(lei)(lei)等.這(zhe)(zhe)些雷(lei)(lei)(lei)(lei)電(dian)(dian)(dian)(dian)(dian)危(wei)害形式的(de)(de)(de)(de)共同特點就(jiu)是放(fang)電(dian)(dian)(dian)(dian)(dian)時總(zong)要(yao)伴隨機械力,高(gao)溫(wen)和強烈火(huo)花的(de)(de)(de)(de)產生。使建筑物破壞,輸電(dian)(dian)(dian)(dian)(dian)線或電(dian)(dian)(dian)(dian)(dian)氣設備損(sun)壞,油罐爆炸,堆場(chang)著火(huo)。黃島油庫因球雷(lei)(lei)(lei)(lei)起火(huo),就(jiu)是典型(xing)的(de)(de)(de)(de)例子。

　　(6)、靜電(dian)(dian) 靜電(dian)(dian)是(shi)物體中正負電(dian)(dian)荷處于靜止狀態下的(de)電(dian)(dian)。隨(sui)著靜電(dian)(dian)電(dian)(dian)荷不斷積聚(ju)而(er)形成(cheng)很(hen)高的(de)電(dian)(dian)位(wei),在一定(ding)條件下,則(ze)對金屬(shu)物或(huo)地放電(dian)(dian),產生有足夠能(neng)量的(de)強烈火花(hua)。此火花(hua)能(neng)使飛(fei)花(hua)麻絮(xu),粉塵,可燃(ran)蒸(zheng)氣(qi)及易(yi)燃(ran)液體燃(ran)燒起火,甚(shen)至引起爆炸。