一、专用保护零线的做法在建筑电气安装中,增设专用保护零线的配线方式已日趋普遍。但自供电变压器低压侧引来的电源并未增设专用保护零线,且过去施工的建筑物也往往是把保护接零接在工作零线上。所以,就配电网而言,这种建筑物内增设专用保护零线的保护方式属于TN-C-S系统,即专用保护零线与电源工作 First, the practice of special protection of the zero line In the construction of electrical installations, the addition of special protection of the zero line has become increasingly common. However, no special protection neutral line has been added to the power source from the low-voltage side of the power supply transformer, and the buildings that were constructed in the past are often connected to zero on the working zero line. Therefore, in the case of distribution networks, the addition of a special protective zero line protection method in the building belongs to the TN-C-S system, ie the dedicated protection zero line and power supply