Wiring a when the leakage protector in the TT system supplies a three-phase balanced load

The wiring of the leakage current protector (RCD) must be correct, otherwise it will cause refusal or malfunction. The basic requirements are as follows.
    ① All live conductors must pass through the zero sequence current transformer, but the protective neutral line PE is not allowed to pass through.
    ② The neutral wire N passing through the leakage protector must be insulated from the ground. In a TN or TT system, the neutral wire N of the neutral current protector passing through the leakage protector
must be insulated from the ground to ensure that the current flowing through the neutral wire N will not be diverted to other lines.
    ③In the TN-C system, the protective neutral line PE should be connected to the PEN line on the power side of the leakage protector, and
the neutral line N behind the leakage protector must be insulated from the ground.
    ④ In the TN-C system, after installing the leakage protector, the re- grounding must be located on the power supply side and not behind the leakage
protector.
(1) Wiring when the leakage protector in the TT system is used for three-phase balanced loads (Figure 20-7)
    In the TT system, the neutral point on the power side is directly grounded, and the metal shell of the electrical equipment on the power side adopts an independent protective grounding
system.

Wiring a when the leakage protector in the TT system supplies a three-phase balanced load