Analysis of Protective Relay Operations during a Ground Fault on a 345kV Transformer Cable in Power Plant Systems

This study conducts a quantitative assessment of protective relay performance based on a 345kV transformer cable ground-fault event within a power plant system. Fault waveforms captured during the incident, along with relay Event Recorder data, were analyzed to characterize current and voltage behavior under both steady-state and fault conditions and to compute the magnitude and duration of the ground-fault current. The results validate the appropriateness of the existing relay parameter settings, confirm the reliability of their fault-clearing operations, and verify proper coordination among the associated protection devices. The findings provide technical insights that can support the refinement of protection settings and enhance the overall dependability of power plant protection schemes.