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Table 4 FIDS logic

From: Transmission line protection challenges influenced by inverter-based resources: a review

Angle between Ia2 and Ia0 Fault type permission
Ia2 is ± 30° of Ia0 Permit AG or BC
Ia2 lags Ia0 by 90° − 150° Permit BG or CA
Ia2 leads Ia0 by 90° − 150° Permit CG or AB
Ia2 leads or lags Ia0 by 30° − 60° Select the ptp mho element with the lowest calculated reach. Compare |Rag| with the |Rf| of that element
Ia2 lags Ia0 by 60° − 90° or 150° − 180° Select the ptp mho element with the lowest calculated reach. Compare |Rbg| with the |Rf| of that element
Ia2 leads Ia0 by 60° − 90° or 150° − 180° Select the ptp mho element with the lowest calculated reach. Compare |Rcg| with the |Rf| of that element
  1. ptp is phase-to-phase, Rag, Rbg, Rcg are A, B, C phase-to-ground fault resistances respectively, and Rf is the fault resistance