Three-Phase Four-Wire System

In the low-voltage distribution network, the transmission line generally adopts a three-phase four-wire system, of which three lines represent A, B, C three-phase, and the other is the neutral line N. So, it calls three-phase four wire system.

Different from the neutral line, in the single-phase transmission line entering the user, there are two lines, one we call the live line, and the other we call the neutral line. Under normal circumstances, the neutral line needs to pass current to form a current loop in a single-phase line, while in a three-phase system, the three-phase loop is formed by itself. Under normal circumstances, the neutral wire is no current

In the 380V low-voltage distribution network, the N line is set to obtain the 220V line-to-line voltage from the 380V phase-to-phase voltage. In some cases, it can also be used for zero-sequence current detection to monitor the balance of the three-phase power supply.

About repeated grounding.

Regardless of the N line or the PE line, repeated grounding must be used on the user side to improve reliability. However, repeated grounding is just repeated grounding, it can only be connected together at the grounding point or close to the grounding, but it does not mean that it can be connected together at any location, especially indoors. This must be kept in mind, and also pay attention to whether your friends have violated.

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