Integrating Relay Models with RMS Dynamic Simulations

Recent major blackout reports have emphasized that protection systems are a critical reliability infrastructure in modern power systems, and that overly conservative relay settings have contributed to unnecessary tripping. Therefore, the need of enhancing the models of protective relays in simulation tools is a worth continuing effort. A PSRCC WG paper reviewed software relay models and divided them into two categories - phasor models and transient models. The phasor models correspond to the relay models largely used in fundamental frequency steady-state software packages. Whereas, the transient models correspond to the relay models that consider voltage/current waveforms, such as those performed on electromagnetic transient programs. Recent efforts to comply with a NERC Standard, give emphasis to the importance of combining RMS dynamic simulation and protection system modeling for severe faults, such as those in analysis of cascading failure risks, delayed fault clearing and stuck circuit breakers. The panel will focus on the integration of relay models with either positive-sequence or three-phase RMS dynamic simulation tools for the assessment of special protection schemes and the impact of extreme events.