在TT装置中，中性导线连接到电源星形中心，
它通常是分布式的，具有产生相电压的功能（例如。
230 V），适用于单相负载供电。外露导电
相反，部分单独或共同地局部连接到地球。
TT系统通常用于民用设施。
当电源分配给负载时，通常使用TN系统
拥有自己的变电站。中性导线直接接地
在变电站内；外露的导电部件连接到同一个
中性导线的接地点，并可局部接地。
根据输电系统的布置，考虑了三种类型的输电系统
中性和保护导体：
1.TN-C中性点和保护功能组合在一根导线中
（PEN导线）；
2.TN-S中性导线和保护导线始终分开；
3.TN-C-S中性点和保护功能组合在一根导线中
在系统的一部分（PEN）和另一部分（PE+N）中分离。
我

In TT installations, the neutral conductor is connected to the supply star center, it is usually distributed and has the function of making the phase voltage (e.g. 230 V) available, useful for single-phase load supply. The exposed conductive parts, on the contrary, singularly or collectively, are locally connected to earth. TT systems are generally used for civil installations. TN systems are typically used when the power supply is distributed to loads having their own electrical substation. The neutral conductor is directly earthed in the substation; the exposed conductive parts are connected to the same earthing point of the neutral conductor, and can be locally earthed. Three types of TN system are considered according to the arrangement of neutral and protective conductors: 1. TN-C neutral and protective functions are combined in a single conductor (PEN conductor); 2. TN-S neutral and protective conductors are always separated; 3. TN-C-S neutral and protective functions are combined in a single conductor in a part of the system (PEN) and are separated in another part (PE + N). I