Principle: the basic principle of zero sequence current protection is based on Kirchhoff current law: the algebraic sum of complex current flowing into any node in the circuit is equal to zero. Under the normal condition of line and electrical equipment, the vector sum of each phase current is equal to zero. Therefore, the secondary winding of zero sequence current transformer has no signal output and the actuator does not act. In case of ground fault, the vector sum of each phase current is not zero. The fault current causes magnetic flux in the ring core of the zero sequence current transformer. The secondary side induced voltage of the zero sequence current transformer makes the actuator act, drives the tripping device, switches the power supply network, and achieves the purpose of ground fault protection.
Function: in case of electric shock or leakage fault in the circuit, the protection acts to cut off the power supply.
Use: a current transformer can be installed on each three-phase line, or three-phase wires can pass through a zero sequence current transformer together, or a zero sequence current transformer can be installed on the neutral line n to detect the three-phase current vector sum.https://www.ctsensorducer.com/