接地故障模式和与带电设备接触造成的后果
零件与中性导线布置和
外露导电部件的连接。
为了正确选择保护装置，有必要知道哪个是
工厂的配电系统。
IEC 60364-1用两个字母对配电系统进行分类。
一个字母表示电力系统与地球的关系：
-T：交流系统中，一点直接接地，
通常为中性点；
-I：交流系统中与地面或一点隔离的所有带电部件，
通常为中性点，通过阻抗接地。
二个字母表示外露导电部件之间的关系
安装至地面：
-T：外露导电部件与地面的直接电气连接；
-N：外露导电部件与接地的直接电气连接
电力系统的点。
后续字母（如有）表示中性和保护
导线：
-S：保护功能由与中性点分离的导线提供
导体
-C：作为单个导体（PEN）组合的中性和保护功能
导线）。
考虑了三种类型的配电系统：

The earth fault modalities and the consequences caused by contact with live parts, are strictly related to the neutral conductor arrangement and to the connections of the exposed conductive parts. For a correct choice of the protective device, it is necessary to know which is the distribution system of the plant. IEC 60364-1 classifies the distribution systems with two letters. The first letter represents the relationship of the power system to earth: - T: direct connection of one point to earth, in alternating current systems, generally the neutral point; - I: all live parts isolated from earth, or one point, in alternating current systems, generally the neutral point, connected to earth through an impedance. The second letter represents the relationship of the exposed conductive parts of the installation to earth: - T: direct electrical connection of the exposed conductive parts to earth; - N: direct electrical connection of the exposed conductive parts to the earthed point of the power system. Subsequent letters, if any, represent the arrangement of neutral and protective conductors: - S: protective function is provided by a conductor separate from the neutral conductor; - C: neutral and protective functions combined as a single conductor (PEN conductor). Three types of distribution system are considered: