How should the protective neutral connection be wired in a distribution box?
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In the distribution boxes of three-phase four-wire systems with neutral grounding used in enterprises, can the working neutral wire be connected to the enclosure of the distribution box? Is connecting the neutral wire to the enclosure of the distribution box considered protective grounding? In most cases, the three phases and the neutral wire are directly connected to the equipment. It is not connected to the distribution box; instead, the enclosure of the distribution box is connected to the ground. Can these two types of protective grounding be installed simultaneously? It means the neutral wire is connected to the casing and then to the ground.
Now it’s all three-phase five-wire system. In the three-phase five-wire system, the neutral wire (N) and the earth wire (PE) are two separate wires. In the TNC configuration, the live and neutral wires are shorted together at the load side; whereas in the TNS configuration, the neutral wire (N) and the earth wire (PE) at the load side are separate.
What was said upstairs is correct, but in the TNC method, the neutral wire can be directly connected to the ground wire. The TNS method must be connected to ground (PE).