Experience in using fault recording facilities in multifunction protective relays to detect actual fault circumstances

During a recent cogeneration plant commissioning, a phase-to-phase fault occurred and developed into a three-phase fault at a generator switchgear terminal. The fault was recorded by two multifunction relays that were protecting areas overlapping the fault location. The captured fault records from one of the relays allowed analysis that was confirmed by a visual inspection of the switchgear cubicle. This paper discusses an experience with the usage of a fault recording function of present-day-technology multifunction relays. The paper provides a methodology for analyzing the measured values of near-generator fault currents and confirms the importance of adequate fault recording facilities in the new multifunction protective relays