根據電(dian)(dian)力設備試驗規(gui)程規(gui)定(ding)，100kVA以下的(de)(de)變(bian)壓器(qi)(qi)接(jie)(jie)地(di)點接(jie)(jie)地(di)電(dian)(dian)阻(zu)(zu)不大于10Ω，100kVA以上的(de)(de)變(bian)壓器(qi)(qi)接(jie)(jie)地(di)點接(jie)(jie)地(di)電(dian)(dian)阻(zu)(zu)不大于4Ω。但由于設計(ji)施(shi)工技術的(de)(de)過(guo)失或(huo)外力的(de)(de)破壞，常常導致變(bian)壓器(qi)(qi)接(jie)(jie)地(di)點接(jie)(jie)地(di)電(dian)(dian)阻(zu)(zu)升(sheng)高(gao)和接(jie)(jie)地(di)線斷線故障發生，造成(cheng)供(gong)電(dian)(dian)異常，用戶電(dian)(dian)器(qi)(qi)設備燒毀(hui)，給供(gong)電(dian)(dian)單位的(de)(de)運行管(guan)理帶來一定(ding)困難。為此我們必須采取一定(ding)的(de)(de)措施(shi)，預(yu)防(fang)變(bian)壓器(qi)(qi)中性(xing)線與接(jie)(jie)地(di)線斷線和接(jie)(jie)地(di)電(dian)(dian)阻(zu)(zu)升(sheng)高(gao)造成(cheng)的(de)(de)危害。

1、變(bian)壓器(qi)接地(di)線和(he)中性線斷(duan)線及接地(di)電阻升(sheng)高的原因(yin)：

(1)由于(yu)接(jie)地(di)體埋(mai)設不規(gui)范，安裝工藝馬虎，接(jie)地(di)體與接(jie)地(di)線(xian)接(jie)頭松動，大(da)地(di)過于(yu)干燥等，均有可能造成接(jie)地(di)電阻的(de)升高。

(2)由(you)(you)于變壓(ya)器設計安裝時，對接地(di)線的(de)作用及重要性(xing)認(ren)識(shi)不足，中性(xing)線截面選擇過小，當三相(xiang)負荷不平(ping)衡時，中性(xing)線電流過大而導致(zhi)燒(shao)斷(duan)。另外(wai)由(you)(you)于外(wai)力的(de)破(po)壞或接地(di)線被盜(dao)等原因都(dou)有可能導致(zhi)接地(di)線或中性(xing)線斷(duan)線。

2、升高(gao)的現象及危害

(1)變(bian)(bian)(bian)(bian)壓(ya)(ya)器接(jie)(jie)(jie)(jie)(jie)地(di)(di)(di)(di)線(xian)(xian)(xian)(xian)接(jie)(jie)(jie)(jie)(jie)地(di)(di)(di)(di)電(dian)(dian)(dian)(dian)阻(zu)(zu)升高(gao)，同(tong)時(shi)(shi)伴有相(xiang)線(xian)(xian)(xian)(xian)絕緣損壞(huai)而接(jie)(jie)(jie)(jie)(jie)地(di)(di)(di)(di)，例如(ru)(ru)，B相(xiang)接(jie)(jie)(jie)(jie)(jie)地(di)(di)(di)(di)，這(zhe)時(shi)(shi)變(bian)(bian)(bian)(bian)壓(ya)(ya)器接(jie)(jie)(jie)(jie)(jie)地(di)(di)(di)(di)線(xian)(xian)(xian)(xian)中將(jiang)有一(yi)個電(dian)(dian)(dian)(dian)流(liu)流(liu)過，B相(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)加(jia)(jia)在大(da)地(di)(di)(di)(di)和(he)接(jie)(jie)(jie)(jie)(jie)地(di)(di)(di)(di)電(dian)(dian)(dian)(dian)阻(zu)(zu)上，當(dang)接(jie)(jie)(jie)(jie)(jie)地(di)(di)(di)(di)電(dian)(dian)(dian)(dian)阻(zu)(zu)越(yue)大(da)，那(nei)么接(jie)(jie)(jie)(jie)(jie)地(di)(di)(di)(di)電(dian)(dian)(dian)(dian)阻(zu)(zu)上的分壓(ya)(ya)就(jiu)越(yue)大(da)。這(zhe)時(shi)(shi)，如(ru)(ru)果有人(ren)(ren)(ren)誤(wu)(wu)觸(chu)(chu)(chu)變(bian)(bian)(bian)(bian)壓(ya)(ya)器接(jie)(jie)(jie)(jie)(jie)地(di)(di)(di)(di)線(xian)(xian)(xian)(xian)或中性(xing)(xing)(xing)線(xian)(xian)(xian)(xian)以(yi)及變(bian)(bian)(bian)(bian)壓(ya)(ya)器外(wai)殼(ke)(ke)，人(ren)(ren)(ren)體將(jiang)和(he)接(jie)(jie)(jie)(jie)(jie)地(di)(di)(di)(di)電(dian)(dian)(dian)(dian)阻(zu)(zu)形成(cheng)并(bing)聯，如(ru)(ru)果接(jie)(jie)(jie)(jie)(jie)地(di)(di)(di)(di)電(dian)(dian)(dian)(dian)阻(zu)(zu)足夠大(da)，那(nei)么加(jia)(jia)在人(ren)(ren)(ren)體上的電(dian)(dian)(dian)(dian)壓(ya)(ya)就(jiu)會很高(gao)，導致人(ren)(ren)(ren)觸(chu)(chu)(chu)電(dian)(dian)(dian)(dian)。如(ru)(ru)果人(ren)(ren)(ren)體誤(wu)(wu)觸(chu)(chu)(chu)A相(xiang)或C相(xiang)，加(jia)(jia)在人(ren)(ren)(ren)體上的電(dian)(dian)(dian)(dian)壓(ya)(ya)將(jiang)是線(xian)(xian)(xian)(xian)電(dian)(dian)(dian)(dian)壓(ya)(ya)380V，那(nei)么對人(ren)(ren)(ren)身安(an)全將(jiang)造成(cheng)更(geng)大(da)的威脅(xie)。另外(wai)，由于(yu)有的用(yong)(yong)(yong)戶將(jiang)變(bian)(bian)(bian)(bian)壓(ya)(ya)器中性(xing)(xing)(xing)線(xian)(xian)(xian)(xian)與用(yong)(yong)(yong)電(dian)(dian)(dian)(dian)設備(bei)(bei)外(wai)殼(ke)(ke)相(xiang)連，作(zuo)保(bao)護接(jie)(jie)(jie)(jie)(jie)地(di)(di)(di)(di)用(yong)(yong)(yong)，而設備(bei)(bei)又不對地(di)(di)(di)(di)絕緣。當(dang)B相(xiang)接(jie)(jie)(jie)(jie)(jie)地(di)(di)(di)(di)，大(da)地(di)(di)(di)(di)就(jiu)和(he)B相(xiang)等電(dian)(dian)(dian)(dian)位(wei)，相(xiang)電(dian)(dian)(dian)(dian)壓(ya)(ya)就(jiu)加(jia)(jia)于(yu)大(da)地(di)(di)(di)(di)和(he)中性(xing)(xing)(xing)線(xian)(xian)(xian)(xian)之間，這(zhe)時(shi)(shi)用(yong)(yong)(yong)電(dian)(dian)(dian)(dian)設備(bei)(bei)如(ru)(ru)取(qu)用(yong)(yong)(yong)A相(xiang)或C相(xiang)電(dian)(dian)(dian)(dian)源，外(wai)殼(ke)(ke)對地(di)(di)(di)(di)電(dian)(dian)(dian)(dian)壓(ya)(ya)將(jiang)升高(gao)到220V，設備(bei)(bei)相(xiang)對地(di)(di)(di)(di)電(dian)(dian)(dian)(dian)壓(ya)(ya)將(jiang)為380V。這(zhe)時(shi)(shi)人(ren)(ren)(ren)如(ru)(ru)果接(jie)(jie)(jie)(jie)(jie)觸(chu)(chu)(chu)用(yong)(yong)(yong)電(dian)(dian)(dian)(dian)設備(bei)(bei)外(wai)殼(ke)(ke)，同(tong)樣會引起(qi)觸(chu)(chu)(chu)電(dian)(dian)(dian)(dian)。另外(wai)，B相(xiang)接(jie)(jie)(jie)(jie)(jie)地(di)(di)(di)(di)時(shi)(shi)，將(jiang)有一(yi)個電(dian)(dian)(dian)(dian)流(liu)從大(da)地(di)(di)(di)(di)流(liu)入機(ji)殼(ke)(ke)回到中性(xing)(xing)(xing)線(xian)(xian)(xian)(xian)，對于(yu)有的要求較高(gao)的用(yong)(yong)(yong)電(dian)(dian)(dian)(dian)設備(bei)(bei)將(jiang)無法運(yun)行(xing)。

(2)接(jie)(jie)地線斷線，變壓器附(fu)近接(jie)(jie)地線斷線，就猶如接(jie)(jie)地電(dian)(dian)(dian)阻(zu)升高到(dao)無(wu)窮大(da)，這(zhe)時(shi)的大(da)地電(dian)(dian)(dian)位(wei)就是(shi)接(jie)(jie)地相電(dian)(dian)(dian)位(wei)，一(yi)切現象就同接(jie)(jie)地電(dian)(dian)(dian)阻(zu)升高時(shi)一(yi)樣(yang)，只是(shi)危害更大(da)，這(zhe)里不再重述。

(3)當三相(xiang)(xiang)四線(xian)(xian)供電(dian)變(bian)壓器(qi)中(zhong)性線(xian)(xian)斷(duan)線(xian)(xian)時(shi)(shi)，此時(shi)(shi)由于三相(xiang)(xiang)負(fu)載的不(bu)平衡，負(fu)載接(jie)地(di)點(dian)將(jiang)發生偏移，接(jie)地(di)點(dian)電(dian)位不(bu)為(wei)零，使得(de)有的相(xiang)(xiang)電(dian)壓升(sheng)高，燒毀用電(dian)設備。當接(jie)地(di)線(xian)(xian)斷(duan)線(xian)(xian)或接(jie)地(di)電(dian)阻升(sheng)高時(shi)(shi)，由于變(bian)壓器(qi)避雷器(qi)接(jie)地(di)線(xian)(xian)斷(duan)開(kai)或接(jie)地(di)電(dian)阻升(sheng)高。雷擊過電(dian)壓時(shi)(shi)，避雷器(qi)不(bu)能正常對地(di)放電(dian)，致使避雷器(qi)或變(bian)壓器(qi)損壞。

3、預防措施

(1)嚴格(ge)施工工藝，規范接地體的(de)埋設。按規程選取(qu)接地線(xian)的(de)截面(mian)及種類，正確(que)選取(qu)中(zhong)性線(xian)截面(mian)積。

(2)在用(yong)戶電能(neng)表后(hou)(hou)裝設(she)剩余(yu)電流動作保(bao)(bao)護器(qi)(qi)(qi)。當我(wo)們在用(yong)戶裝設(she)了保(bao)(bao)護器(qi)(qi)(qi)后(hou)(hou)，如(ru)果用(yong)戶后(hou)(hou)的導(dao)線或用(yong)電設(she)備(bei)絕緣損壞，形成對地(di)放電。此時(shi)如(ru)果變壓器(qi)(qi)(qi)接地(di)點接地(di)電阻過高(gao)，大(da)地(di)電位將(jiang)(jiang)(jiang)不再為零，這時(shi)將(jiang)(jiang)(jiang)有一個電流經保(bao)(bao)護器(qi)(qi)(qi)、大(da)地(di)流入變壓器(qi)(qi)(qi)接地(di)點，此電流將(jiang)(jiang)(jiang)使保(bao)(bao)護器(qi)(qi)(qi)動作，而(er)將(jiang)(jiang)(jiang)接地(di)點切(qie)除，防止了大(da)地(di)電位的升(sheng)高(gao)。另(ling)外，加裝保(bao)(bao)護器(qi)(qi)(qi)后(hou)(hou)，當人接觸相線時(shi)，保(bao)(bao)護器(qi)(qi)(qi)也會動作，從而(er)保(bao)(bao)障了人員的人身(shen)安全。

(3)在(zai)(zai)變(bian)(bian)壓(ya)(ya)器的(de)中(zhong)(zhong)(zhong)性(xing)線(xian)上選取適(shi)當(dang)的(de)位置將變(bian)(bian)壓(ya)(ya)器的(de)中(zhong)(zhong)(zhong)性(xing)線(xian)多(duo)點(dian)(dian)重復接(jie)(jie)地(di)(di)。當(dang)變(bian)(bian)壓(ya)(ya)器中(zhong)(zhong)(zhong)性(xing)線(xian)在(zai)(zai)某點(dian)(dian)斷線(xian)時(shi)，由于多(duo)點(dian)(dian)接(jie)(jie)地(di)(di)，中(zhong)(zhong)(zhong)性(xing)線(xian)電(dian)流仍可經大(da)地(di)(di)回到變(bian)(bian)壓(ya)(ya)器中(zhong)(zhong)(zhong)性(xing)點(dian)(dian)，中(zhong)(zhong)(zhong)性(xing)線(xian)的(de)電(dian)位始終(zhong)為零(ling)，每相負載的(de)電(dian)壓(ya)(ya)始終(zhong)為正常的(de)相電(dian)壓(ya)(ya)。另一方面，當(dang)變(bian)(bian)壓(ya)(ya)器接(jie)(jie)地(di)(di)點(dian)(dian)接(jie)(jie)地(di)(di)電(dian)阻升高或接(jie)(jie)地(di)(di)線(xian)斷線(xian)相線(xian)接(jie)(jie)地(di)(di)，由于有了多(duo)點(dian)(dian)的(de)重復接(jie)(jie)地(di)(di)，也(ye)能(neng)保(bao)證大(da)地(di)(di)的(de)電(dian)位為零(ling)，不會對人生安全和設備(bei)的(de)正常運行造(zao)成威(wei)脅。在(zai)(zai)采取以上防范(fan)措施的(de)同(tong)時(shi)，也(ye)要(yao)加(jia)強對廣(guang)大(da)人民群眾進行電(dian)力法規(gui)的(de)廣(guang)泛宣傳(chuan)，讓更多(duo)的(de)人來關心電(dian)力設施。一經發現設備(bei)障(zhang)礙，能(neng)及時(shi)向供電(dian)部門反(fan)映，以求(qiu)盡快將電(dian)力設備(bei)故障(zhang)消滅在(zai)(zai)萌(meng)芽狀態(tai)，確保(bao)安全可靠地(di)(di)供電(dian)。