*4.4. Double Phase to Ground Fault*

The double phase to ground (2PG) fault is simulated on phases A and B at 0.1 s at node 646. Current and voltage signals recorded at node 650 for the period of 0.2 s (12 cycles) are described in Figure 7a,b, respectively. Current signals are processed using WDF and WD-index is computed, which is detailed in Figure 7c. This is observed that WD-index corresponding to phases A and B has a high magnitude after incidence of 2PG fault. However, this index corresponding to the phase C has values comparable to the pre-fault values. The ALN-index is computed from the voltage signals and detailed in Figure 7d. This is inferred that ALN-index corresponding to all the phases, sharply increases just after incidence of 2PG fault.

Figure 7e details the FI corresponding to all the phases, during the event of 2PG fault. It is seen that FI corresponding to faulty phases (phases A and B) has a higher magnitude compared to TM after the incidence of 2PG fault. However, FI corresponding to the healthy phase (phase C) has a lower magnitude as compared to TM. Hence, the algorithm is found to be effective for the identification of 2PG fault and for the discrimination of the healthy and faulty phases. High resolution of FI is illustrated in Figure 7f. It is observed that FI corresponding to phases A and B rises and cross the TM after 8 × <sup>10</sup>−<sup>5</sup> s and 3 × <sup>10</sup>−<sup>5</sup> s, respectively, which are equal to 0.48% and 0.18% of total time of the cycle in same order. FI corresponding to the healthy phase C remains below the threshold. Hence, the 2PG fault was detected effectively in time equal to 0.48% of the total time duration of the cycle.

**Figure 7.** Recognition of 2PG fault incident at node 646 of hybrid test system (**a**) current waveform (**b**) voltage waveform (**c**) WD-index (**d**) ALN-index (**e**) FI (f) plot to compute fault recognition time.
