該系統(tong)接地故障多(duo)為金屬性短路(lu)，因故障電(dian)流較大，使斷(duan)路(lu)器(qi)或熔斷(duan)器(qi)等(deng)過電(dian)流保護裝置動作(zuo)，造成房間停電(dian)。顯(xian)然TN—S系統(tong)不(bu)(bu)能滿足醫院中(zhong)一些(xie)重(zhong)要(yao)場(chang)所(suo)對不(bu)(bu)間斷(duan)供電(dian)的實用(yong)要(yao)求。故醫院2類場(chang)所(suo)：如(ru)中(zhong)心手術部的所(suo)有(you)手術室(shi)I所(suo)有(you)CU病房(包括ICU，CCU，NICU，PICU，SICU等(deng))和心臟導管介(jie)入(ru)室(shi)等(deng)，醫用(yong)it系統(tong)多(duo)少錢，應當采用(yong)醫用(yong)隔離(li)電(dian)源(IT)系統(tong)供電(dian)。

醫用IT系(xi)(xi)統(tong)(tong)(tong)（俗稱(cheng)醫用隔離電(dian)源系(xi)(xi)統(tong)(tong)(tong)），又叫中(zhong)(zhong)性點(dian)不(bu)接(jie)(jie)(jie)(jie)地配電(dian)系(xi)(xi)統(tong)(tong)(tong)。在IT系(xi)(xi)統(tong)(tong)(tong)中(zhong)(zhong)，系(xi)(xi)統(tong)(tong)(tong)中(zhong)(zhong)性點(dian)對地完全隔離，系(xi)(xi)統(tong)(tong)(tong)負載(zai)中(zhong)(zhong)的外殼經接(jie)(jie)(jie)(jie)地保(bao)(bao)護線(xian)接(jie)(jie)(jie)(jie)地。如(ru)果出現單相(xiang)接(jie)(jie)(jie)(jie)地故障(zhang)，對地漏(lou)電(dian)流(liu)只能經過系(xi)(xi)統(tong)(tong)(tong)泄露電(dian)容(rong)對系(xi)(xi)統(tong)(tong)(tong)相(xiang)線(xian)構成回路，而系(xi)(xi)統(tong)(tong)(tong)泄露電(dian)容(rong)引(yin)起的容(rong)抗總是(shi)遠(yuan)遠(yuan)大于(yu)TN系(xi)(xi)統(tong)(tong)(tong)中(zhong)(zhong)的接(jie)(jie)(jie)(jie)地電(dian)阻，因此IT系(xi)(xi)統(tong)(tong)(tong)中(zhong)(zhong)的漏(lou)電(dian)流(liu)非(fei)常(chang)的小，斷路器不(bu)會因接(jie)(jie)(jie)(jie)地電(dian)流(liu)的存在而引(yin)起過電(dian)流(liu)動作，從(cong)而保(bao)(bao)證系(xi)(xi)統(tong)(tong)(tong)帶故障(zhang)運(yun)行(xing)。

醫用IT系統是指(zhi):醫用IT系統中的電氣(qi)設(she)備(bei)(bei)有外露導電部分通過保護(hu)線接地．而(er)電源隔離回路中的設(she)備(bei)(bei)外殼(ke)不做(zuo)接地。它是采用特低電壓(ya)回路輔以不接地的等(deng)電位連(lian)(lian)接（將電源隔離區域內(nei)的各個電氣(qi)設(she)備(bei)(bei)金屬外殼(ke)用絕緣導線互相連(lian)(lian)通）來獲得(de)好的安全(quan)的效果。電源隔離適用于浴室(shi)、游泳池(chi)等(deng)危險大，對不間斷供電無(wu)特殊要求的潮濕(shi)場所。