Set impedance Zset: protect the impedance between the installation site and the set point.
Action impedance Zop: the impedance value measured when the impedance relay just acts.
1. The measured impedance is determined by the ratio of the measured voltage to the measured current applied to the impedance relay, and the measured impedance angle is the phase difference between the measured voltage and the measured current.
2. The setting impedance generally takes the line impedance from the protection device to the end of the protected area as the setting impedance.
3. The action impedance is the maximum measured impedance that enables the impedance relay to start. The working impedance of directional impedance relay and offset impedance relay changes with the change of impedance angle.