在(zai)發電(dian)廠(chang)變壓器那邊，零(ling)線(xian)(xian)的(de)確和(he)(he)地線(xian)(xian)是(shi)(shi)從一(yi)個(ge)中性線(xian)(xian)點引出來的(de)，源頭是(shi)(shi)短(duan)接到一(yi)起的(de)，然(ran)后也(ye)是(shi)(shi)和(he)(he)大地連接的(de)。對于工廠(chang)里(li)邊使(shi)用(yong)的(de)TN-C系統（我們常說的(de)三相四線(xian)(xian)制），零(ling)線(xian)(xian)和(he)(he)地線(xian)(xian)是(shi)(shi)一(yi)條(tiao)線(xian)(xian)，工廠(chang)的(de)設備都能正常使(shi)用(yong)。但是(shi)(shi)對于民(min)用(yong)的(de)TN-S或(huo)者TC-C-S系統（俗稱三相五線(xian)(xian)制），至少在(zai)家里(li)邊使(shi)用(yong)的(de)這段(duan)，零(ling)線(xian)(xian)和(he)(he)地線(xian)(xian)是(shi)(shi)嚴格分開的(de)，如果接到一(yi)起了，至少漏(lou)保是(shi)(shi)不能使(shi)用(yong)，即使(shi)你(ni)不裝了漏(lou)保強行使(shi)用(yong)，也(ye)會有很(hen)多的(de)安全隱(yin)患

1、零線(xian)和(he)地(di)(di)線(xian)，雖然源頭一(yi)樣是(shi)(shi)發電(dian)機的(de)(de)(de)(de)中性點，實(shi)際作用不同，零線(xian)是(shi)(shi)參與(yu)工作的(de)(de)(de)(de)，而地(di)(di)線(xian)使用來保護(hu)的(de)(de)(de)(de)，所以理想的(de)(de)(de)(de)TN-S系統，零線(xian)和(he)地(di)(di)線(xian)是(shi)(shi)一(yi)路嚴格(ge)分開來，零線(xian)和(he)相(xiang)線(xian)（火線(xian)）一(yi)樣走線(xian)，和(he)回(hui)路構成工作回(hui)路，零線(xian)的(de)(de)(de)(de)作用等(deng)同于相(xiang)線(xian)，而地(di)(di)線(xian)每隔開一(yi)段(duan)距(ju)離就要(yao)用扁鋼材料來接入(ru)大地(di)(di)，就是(shi)(shi)所謂的(de)(de)(de)(de)重(zhong)復(fu)接地(di)(di)，地(di)(di)線(xian)這(zhe)樣反復(fu)接入(ru)大地(di)(di)，是(shi)(shi)為了保證地(di)(di)線(xian)的(de)(de)(de)(de)電(dian)勢和(he)大地(di)(di)絕對相(xiang)等(deng)，人在大地(di)(di)上長期(qi)活動才(cai)可以起到保護(hu)作用。如果把地(di)(di)線(xian)和(he)零線(xian)短(duan)接一(yi)起了，三相(xiang)五線(xian)制就變成三相(xiang)四線(xian)制，白白浪費(fei)了一(yi)條布線(xian)，而且又失去了保護(hu)作用。

2、因為地(di)(di)線(xian)每隔一(yi)段(duan)距離就接入(ru)大(da)地(di)(di)，所(suo)以地(di)(di)線(xian)的(de)對地(di)(di)電阻非常小(xiao)，一(yi)般要小(xiao)于(yu)四歐姆(mu)，這(zhe)樣地(di)(di)線(xian)接到(dao)(dao)電器外(wai)殼上，電器外(wai)殼的(de)電位等同于(yu)大(da)地(di)(di)電位，人用手(shou)觸摸電器外(wai)殼，不會觸電。而零線(xian)并(bing)沒有這(zhe)樣的(de)接入(ru)大(da)地(di)(di)，因此到(dao)(dao)了用戶這(zhe)頭(tou)，零線(xian)對地(di)(di)的(de)電阻，是(shi)比地(di)(di)線(xian)大(da)很(hen)多的(de)，這(zhe)樣看起來，零線(xian)對大(da)地(di)(di)的(de)電位差并(bing)不是(shi)0，短接到(dao)(dao)一(yi)起，就可能危害(hai)到(dao)(dao)人體了。

3、零線(xian)(xian)(xian)在(zai)正(zheng)常情況下(xia)參(can)與了(le)工作，因為小(xiao)區里(li)邊(bian)是分成單相電(dian)(dian)(dian)(dian)入戶(hu)來給小(xiao)區使(shi)用的(de)(de)，零線(xian)(xian)(xian)會通過(guo)和火線(xian)(xian)(xian)一樣大的(de)(de)電(dian)(dian)(dian)(dian)流(liu)，這樣電(dian)(dian)(dian)(dian)器才(cai)可以正(zheng)常工作，所以現在(zai)零線(xian)(xian)(xian)都要(yao)求不(bu)能細過(guo)火線(xian)(xian)(xian)的(de)(de)，歐洲(zhou)有些標準還要(yao)求比火線(xian)(xian)(xian)粗(cu)，因為要(yao)考慮一些諧(xie)波問題(ti)。而地(di)線(xian)(xian)(xian)正(zheng)常時候并不(bu)參(can)與工作，只有火線(xian)(xian)(xian)擊穿絕(jue)緣漏電(dian)(dian)(dian)(dian)到(dao)外殼(ke)(ke)或者(zhe)火線(xian)(xian)(xian)脫落到(dao)外殼(ke)(ke)上(shang)的(de)(de)時候，地(di)線(xian)(xian)(xian)才(cai)會把(ba)電(dian)(dian)(dian)(dian)泄放掉，保證人(ren)體的(de)(de)安全。如果零線(xian)(xian)(xian)在(zai)家(jia)里(li)被短接到(dao)一起(qi)了(le)，如果電(dian)(dian)(dian)(dian)器外殼(ke)(ke)漏電(dian)(dian)(dian)(dian)了(le)，從火線(xian)(xian)(xian)過(guo)來的(de)(de)電(dian)(dian)(dian)(dian)流(liu)，會分成兩路(lu)徑流(liu)回到(dao)發(fa)電(dian)(dian)(dian)(dian)機那頭，

一條路徑(jing)是(shi)：火線→電器設備→零(ling)線→發(fa)電機中性點

另外一條路徑是：火線→電器設備→地線（大(da)地）→發電機中性(xing)點

如(ru)果碰巧(qiao)零線(xian)接(jie)觸(chu)不良甚至斷掉了，這樣接(jie)地的全部(bu)電器設備的外殼(ke)都帶電了，又發生了接(jie)地不好甚至地線(xian)斷了，人只(zhi)要碰到(dao)家(jia)里任何一(yi)部(bu)電器設備外殼(ke)，都會被電到(dao)的，非常危險(xian)。

4、有(you)些舊房子(zi)，還是用(yong)閘刀開關的(de)，線(xian)(xian)(xian)(xian)(xian)(xian)路上(shang)只有(you)火(huo)(huo)線(xian)(xian)(xian)(xian)(xian)(xian)零(ling)(ling)線(xian)(xian)(xian)(xian)(xian)(xian)，千萬(wan)不要把(ba)零(ling)(ling)線(xian)(xian)(xian)(xian)(xian)(xian)和地線(xian)(xian)(xian)(xian)(xian)(xian)短接(jie)一起(qi)了，可以(yi)(yi)換掉那種(zhong)兩極(ji)的(de)空氣(qi)開關，如果(guo)有(you)短路問題空氣(qi)開關還可以(yi)(yi)調整，但是零(ling)(ling)線(xian)(xian)(xian)(xian)(xian)(xian)和地線(xian)(xian)(xian)(xian)(xian)(xian)短接(jie)一起(qi)了會(hui)造成屋子(zi)里邊的(de)設備(bei)外殼都有(you)帶電(dian)危險。零(ling)(ling)線(xian)(xian)(xian)(xian)(xian)(xian)和地線(xian)(xian)(xian)(xian)(xian)(xian)，如果(guo)弄混淆了，無法知道，也要用(yong)心找出來(lai)的(de)，不能(neng)亂(luan)接(jie)回去。因為零(ling)(ling)線(xian)(xian)(xian)(xian)(xian)(xian)和火(huo)(huo)線(xian)(xian)(xian)(xian)(xian)(xian)的(de)電(dian)位在220伏(fu)作用(yong)，而地線(xian)(xian)(xian)(xian)(xian)(xian)和火(huo)(huo)線(xian)(xian)(xian)(xian)(xian)(xian)的(de)電(dian)壓(ya)一般會(hui)小一點，可以(yi)(yi)通過簡單(dan)測量來(lai)比較。或者(zhe)用(yong)電(dian)筆之類的(de)看燈暗亮來(lai)對比，火(huo)(huo)線(xian)(xian)(xian)(xian)(xian)(xian)當然(ran)是非常亮的(de)，而零(ling)(ling)線(xian)(xian)(xian)(xian)(xian)(xian)會(hui)微亮，地線(xian)(xian)(xian)(xian)(xian)(xian)是不會(hui)亮的(de)。

5、實際上，家里都(dou)有(you)漏(lou)電保護開(kai)關，如果零(ling)(ling)線(xian)(xian)和地線(xian)(xian)短(duan)接一(yi)起了(le)，漏(lou)電保護開(kai)關將(jiang)會(hui)(hui)(hui)直(zhi)接跳閘，無法合上的(de)。因為火(huo)線(xian)(xian)的(de)電流，會(hui)(hui)(hui)有(you)一(yi)部分通過地線(xian)(xian)泄露出(chu)去了(le)，并不會(hui)(hui)(hui)回到零(ling)(ling)線(xian)(xian)中，這(zhe)樣(yang)火(huo)線(xian)(xian)和零(ling)(ling)線(xian)(xian)的(de)電流矢量和不為零(ling)(ling)，所以(yi)漏(lou)保會(hui)(hui)(hui)跳閘保護。