What are the requirements when installing a zero sequence current transformer for cables? Why?

The wiring method of the zero-sequence current transformer is that a current transformer can be installed on the three-phase line, or the three-phase wire can pass through the zero-sequence current transformer together, or a zero-sequence current transformer can be installed on the neutral line N, and it can be used to detect the current vector sum of the three phases.

The function of the zero-sequence current transformer is to protect the action and cut off the power supply when an electric shock or leakage fault occurs in the circuit.

Kiss the zero sequence current transformer can't wear the zero line. A zero-sequence current transformer is a device used to measure and control the zero-sequence current in the electrical system, which helps to reduce the overcurrent and ground leakage current in the electrical system. Zero-sequence current transformers must be paired with positive-sequence current transformers to accurately measure positive-sequence currents and associated energy flows in the grid.

The zero-sequence current transformer cannot be used alone for the old liquid cover, otherwise the instability of the network system will be unstable, and even the safety and stability of the electrical system will be affected by oscillation. Therefore, the zero-sequence current transformer should not wear the neutral line to prevent the abnormality of the system and the imbalance of the current. In addition, it should be avoided to transfer the loaded neutral line and DC current together to avoid potential danger and damage to the system equipment.

Summary. Used in the three-phase four-wire system, the zero-sequence current transformer installed on the load side cannot pass through the neutral line, but only through the three-phase live wire.

Hello, dear, very happy with your question, zero sequence current transformer can never wear the zero line, right? , to help you find out: right.

Used in the three-phase four-wire system, the zero-sequence current transformer installed on the load side cannot pass through the neutral line, but only through the three-phase live wire.

This is because the zero-sequence current component generated by the three-phase live wire grip delay flows back from the neutral line to the neutral point of the power supply, so the magnitude is equal and the direction is opposite. If they all pass through the zero-sequence current intersection to make Li inductors, then the generated zero-hu impulse sequence magnetic flux is also equal in magnitude and opposite in direction, thus canceling each other.

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Hello! Installation problems (1) The current transformer should be installed on the bottom plate of the switch cabinet and fixed with a reliable bracket. However, some manufacturers or construction units will install the zero-sequence current transformer '> current transformer' on the bracket below the bottom plate of the open cabinet, and even tie the zero-sequence current transformer '> current transformer' to the cable, which violates the principle of fully enclosed open cabinet, which is neither safe, nor dust-proof, nor dust-proof, and can not prevent small animals, leaving many hidden dangers.

2) After the cable terminal passes through the external zero sequence current transformer '>' current transformer, the relative position of the metal shield grounding wire of the cable and the external zero sequence current transformer '>' current transformer is incorrect. According to the provisions of the "Code for the Installation of Electrical Engineering in Beijing": the copper shielding of each phase of the plastic cable and the steel armor tin soldered ground wire (the lead package and armor of the oil-impregnated paper insulated cable should be welded with the grounding wire), the current transformer, the cable metal sheath and the grounding wire should be grounded and insulated, the cable grounding point (cable grounding wire and cable metal shielding solder joint) is below the transformer, and the grounding wire should be directly grounded.