TN-C system

According to the International Electrotechnical Commission (IEC) standards, the wiring system of the low-voltage power network is divided into three
types: TN, TT and IT. aTT is a system in which the neutral point of the power transformer is directly grounded and the metal shell of the electrical equipment is separately grounded; IT is a system in which the power transformer neutral point is directly grounded. A system in which the neutral point is not grounded or is grounded through impedance, and the metal shell of the electrical equipment is grounded; TN is a zero-connection protection system in which the neutral point of the power transformer is directly grounded and the metal shell of the electrical equipment is connected to the neutral wire. The TN system is divided into TN-C system, TN-S system and TN-CS system. (I) TN-C system     In the entire system, the neutral line N (i.e., the working neutral line) and the protective neutral line PE are shared (referred to as PEN).