This paper deals with an innovative Loss of Field Protection Scheme (LoFPS), in which, some key supplementary features are provided to avoid spurious trip of the Conventional Impedance-Based Relay (CIBR) during Stable Power Swing (SPS). The proposed algorithm is developed for two conditions of the multiple-parallel-synchronous generator (SG) and single-SG in service. Entrance time (ti) of Z-trajectory to the CIBR zones is utilized for single- SG in service owing to the different dynamic responses of the SG to the LoF/SPS events. Meanwhile, for the multiple-parallel-SGs condition, the average value of the variation of the output reactive current of SG (ΔIRSG) is selected to analyze the dynamic behavior of the faulty- and healthy-parallel-SGs. The ΔIRSG for all the parallel- SGs during both normal and SPS conditions has a similar polarity, whereas during LoF incidence in one SG, its polarity is different for the faulty and healthy-parallel SGs. Therefore, the nuisance trip of the CIBR can be easily avoided by implementing the selected features. Widespread simulation studies in MATLAB/Simulink environ- ment on the IEEE 9-bus test system affirm the superiority, higher reliability, and easy implementation of the developed LoFPS than other schemes, especially the CIBR ones.
