Negative-Sequence Directional Ground Relaying

The principles, problems, and solutions in applying negative sequence for directional ground relaying in 3-phase power systems are given in detail. Two general application areas are covered: (1) where system economics do not permit the necessary equipment for zero-sequence polarization and (2) for mutual induction on parallel lines. A practical method is included to evaluate relay operation without the knowledge of negative-sequence voltages and currents.