Impedance Relays for Fault Detection

Impedance relays help protect power lines by watching the voltage-to-current ratio on a line. They measure the apparent impedance, which is the electrical opposition the relay sees at that point in the system. This makes them useful when time-delay overcurrent relays are hard to coordinate in complex radial systems and when ...

Coordinating time-delay overcurrent relays in complex radial systems can be challenging, as can directional overcurrent relays in multi-source transmission loops.

Impedance relays solve these issues by responding to voltage-to-current ratios, becoming more sensitive during three-phase faults when current increases and voltage decreases.