The difference between ordinary current transformer and Zero Sequence Current Transformer

1. The role of ordinary current transformers

Ordinary current transformers can convert a larger value of primary current into a smaller value of secondary current through a certain transformation ratio, which is used for protection, measurement and other purposes. For example, a current transformer with a ratio of 400/5 can convert an actual current of 400A into a current of 5A.

2. Working principle of Zero Sequence Current Transformer

The basic principle of zero-sequence current protection is based on Kirchhoff's current law: 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 winding of the Zero Sequence Current Transformer has no signal output, and the actuator does not act. When the ground fault occurs, the vector sum of the currents of each phase is not zero, the fault current generates magnetic flux in the annular 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 and drive the tripping. device, switch the power supply network, and achieve the purpose of ground fault protection.

3. The role of Zero Sequence Current Transformer

When an electric shock or leakage fault occurs in the circuit, the protection action will cut off the power supply.

4. Zero Sequence Current Transformer usage conditions

A current transformer can be installed on each of the three-phase lines, or a Zero Sequence Current Transformer can be passed through the three-phase wires together, or a Zero Sequence Current Transformer can be installed on the neutral line N, Use it to detect the current vector sum of the three phases.