This protection method detects faults by monitoring phase current imbalances. It is widely employed in systems with an ungrounded neutral, a neutral grounded via an arc-suppression coil (Petersen coil), or a. A zero-sequence voltage relay is a protective device designed to detect imbalances in three-phase power systems by measuring the zero-sequence voltage component. This component arises when the vector sum of the three-phase voltages (Va, Vb, Vc) is non-zero, indicating an asymmetrical fault or. Ungrounded: There is no intentional ground applied to the system-however it's grounded through natural capacitance. Reactance Grounded: Total system capacitance is cancelled by equal inductance. I 2 = 31 (I a . fault type identification, fault direction identification, and fault discrim nation in general. Not influenced by load, they contribute to protection speed and sensitivity.