低壓入(ru)(ru)(ru)戶線進(jin)入(ru)(ru)(ru)建(jian)筑物后要用浪涌保(bao)護(hu)(hu)器（SPD）對侵入(ru)(ru)(ru)波電(dian)(dian)(dian)壓加以(yi)限制(zhi)。浪涌保(bao)護(hu)(hu)器的(de)設置(zhi)方式和(he)低壓配(pei)電(dian)(dian)(dian)系(xi)統(tong)(tong)的(de)供(gong)電(dian)(dian)(dian)方式直(zhi)接(jie)(jie)相(xiang)(xiang)關。常用的(de)低壓配(pei)電(dian)(dian)(dian)系(xi)統(tong)(tong)的(de)供(gong)電(dian)(dian)(dian)方式有(you)三(san)(san)相(xiang)(xiang)四線制(zhi)保(bao)護(hu)(hu)接(jie)(jie)地（TT系(xi)統(tong)(tong)）、三(san)(san)相(xiang)(xiang)四線制(zhi)保(bao)護(hu)(hu)接(jie)(jie)零（TN-C系(xi)統(tong)(tong)）、三(san)(san)相(xiang)(xiang)五線制(zhi)（TN-S系(xi)統(tong)(tong)）以(yi)及三(san)(san)相(xiang)(xiang)三(san)(san)線制(zhi)保(bao)護(hu)(hu)接(jie)(jie)地（IT系(xi)統(tong)(tong)）。信(xin)息設備低壓配(pei)電(dian)(dian)(dian)系(xi)統(tong)(tong)應(ying)采用TN-S系(xi)統(tong)(tong)供(gong)電(dian)(dian)(dian)。當(dang)供(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)源(yuan)為TN-C系(xi)統(tong)(tong)時，應(ying)在(zai)進(jin)入(ru)(ru)(ru)信(xin)息系(xi)統(tong)(tong)機房前轉換(huan)為TN-S系(xi)統(tong)(tong)，稱為TN-C-S系(xi)統(tong)(tong)。

浪涌保護器(qi)的限壓元(yuan)件要接在(zai)相(xiang)線(xian)（L1、L2、L3）和中(zhong)性(xing)線(xian)（N線(xian)）間，或相(xiang)線(xian)和保護地（PE）間。在(zai)保護地和中(zhong)性(xing)線(xian)間沒有聯(lian)系(xi)時，在(zai)應在(zai)N和PE間設置限壓元(yuan)件。

一、TT系統

由于N線(xian)只在電源側接地，它與設(she)備的保護(hu)地是(shi)分(fen)開的，所以在N線(xian)和(he)PE間設(she)置了限(xian)壓元件。

方案一(yi)：4+0方案

4+0方案是指限(xian)壓(ya)元件接(jie)在相(xiang)(xiang)線(xian)和PE間的(de)方案。考慮到系統(tong)單項接(jie)地時，相(xiang)(xiang)線(xian)的(de)對(dui)地電(dian)壓(ya)會(hui)上升到超(chao)(chao)過相(xiang)(xiang)電(dian)壓(ya)，出現在N線(xian)和PE線(xian)間的(de)電(dian)壓(ya)差取決于系統(tong)中(zhong)性點的(de)位移，一般不會(hui)超(chao)(chao)過系統(tong)的(de)相(xiang)(xiang)電(dian)壓(ya)，因此(ci)設置在N線(xian)和PE間的(de)限(xian)壓(ya)元件的(de)工作條件要相(xiang)(xiang)對(dui)輕松些(xie)。

方(fang)案二：3+1方(fang)案

限壓元件接(jie)在(zai)相(xiang)線(xian)和(he)(he)N線(xian)間的(de)方案，作用(yong)在(zai)相(xiang)線(xian)和(he)(he)N線(xian)間的(de)限壓元件上(shang)的(de)工作電(dian)壓不(bu)會超過(guo)相(xiang)電(dian)壓，使用(yong)時(shi)應將限壓元件的(de)最大可持續運(yun)行電(dian)壓取得比(bi)其標(biao)稱(cheng)相(xiang)電(dian)壓大。

二、TN-C系統

由于TN-C系(xi)統N線(xian)(xian)(xian)(xian)(xian)(xian)和PE線(xian)(xian)(xian)(xian)(xian)(xian)在電(dian)源側已合為一條PEN線(xian)(xian)(xian)(xian)(xian)(xian)，所以不存在N線(xian)(xian)(xian)(xian)(xian)(xian)和PE線(xian)(xian)(xian)(xian)(xian)(xian)間設置限壓(ya)元件的問題，可稱為“3+0”方案。采用“3+0”方案時(shi)，在系(xi)統單項接地時(shi)，相(xiang)線(xian)(xian)(xian)(xian)(xian)(xian)的對地電(dian)壓(ya)會上升到超過相(xiang)電(dian)壓(ya)。

三、TN-S系(xi)統(tong)

由(you)于(yu)在用戶處N線和(he)PE線是(shi)分開的，所(suo)以在N線和(he)PE線間設置了限壓(ya)元(yuan)件(jian)(jian)。可分為(wei)“4+0”和(he)“3+1”方(fang)案兩種。TN-S系(xi)統中(zhong)，限壓(ya)元(yuan)件(jian)(jian)的最大持(chi)續運行電壓(ya)的選(xuan)取方(fang)法和(he)TT系(xi)統相同。

四、IT系統

由于(yu)IT系統中沒有中性(xing)線(xian)，所以(yi)不存在在N線(xian)和PE間設置(zhi)限(xian)壓元件(jian)的(de)問題(ti)，只需要采用三個限(xian)壓元件(jian)。

考(kao)慮到在IT系統中系統單項(xiang)接地時(shi)，健全(quan)(quan)相的(de)對(dui)地電壓(ya)會上升到線電壓(ya)，在考(kao)慮到安全(quan)(quan)裕度，使用時(shi)應(ying)將(jiang)限(xian)壓(ya)元件(jian)的(de)最大持續運行電壓(ya)取得比(bi)其(qi)標稱線電壓(ya)大。