Are all the low-voltage systems in China Power Grid TN-C-S?

There are three systems coexisting in the low-voltage system of China power grid.

(1)TN-C system (three-phase four-wire system), in which neutral wire (n) and protection wire (PE) are integrated, also called protection neutral wire (PEN). Its advantage is that it saves a conductor, but its disadvantage is that when the three-phase load is unbalanced or the protective neutral wire is disconnected, the metal shell of all electrical equipment will carry dangerous voltage.

(2)TN-S system is a three-phase five-wire system. The N-wire and PE-wire of the system are separated, and five-wire power supply has been used since the transformer. Its advantage is that there is no current flowing on the PE line under normal circumstances, so it will not cause electromagnetic interference to other equipment on the PE line. In addition, because the N line and the PE line are separated, the disconnection of the N line will not affect the protection of the PE line.

(3) TN-C-S system (three-phase, four-wire ③TN-C-S hybrid system), with four-wire system from transformer to user distribution box, with neutral wire and protective ground wire as a whole; The neutral wire and protective ground wire from the distribution box to the user are separated, so it has the characteristics of TN-C system and TN-S system, and is often used in places with poor terminal environment of distribution system or strict requirements for electromagnetic anti-interference.