Working principle of zero sequence current transformer

1. The algebraic sum of the complex currents flowing into any node in the circuit is equal to zero. When the line and electrical equipment are normal, the vector sum of the currents of each phase is equal to zero. Therefore, the secondary side winding of the zero-sequence current transformer has no signal output, and the actuator does not operate.

2. When a ground fault occurs, the vector sum of the currents of each phase is not zero, the fault current causes magnetic flux to be generated in the ring iron core of the zero-sequence current transformer, and the induced voltage on the secondary side of the zero-sequence current transformer causes the actuator to act , Drive the tripping device, switch the power supply network, and achieve the purpose of ground fault protection.