*6.5. Sampling Frequency Variations*

To investigate the effect of frequency used for sampling the voltage and current signals on the performance of protection scheme, the algorithm was tested for different sampling frequencies. FI corresponding to the faulty phase A during the event of PG fault is observed and equal to 3.981 × 104, 5.055 × 104, and 5.170 × 104 while using the sampling frequencies of 1.92 kHz, 3.84 kHz and 7.68 kHz, respectively. Therefore, sampling frequency, lower than 3.84 kHz, reduces the peak magnitude of FI, which may also go lower compared to TM. Sampling frequency greater than 3.84 kHz increases the fault detection time due to large size of input data set. Hence, 3.84 kHz is observed to be the optimum SF for the protection scheme.

**Figure 12.** Recognition of PG fault incident on node 652 of hybrid test system in the presence of noise (10dB SNR) (**a**) current waveform (**b**) voltage waveform (**c**) WD-index (**d**) ALN-index (**e**) FI (**f**) plot to compute fault recognition time.

#### *6.6. Recognition of Fault by Recording Voltage and Current Signals at PCC*

Performance of the algorithm was tested by recording voltage and current signals at PCC (PS-2 relay location), where RE sources are integrated to test hybrid grid and when PG fault is simulated at node 646 to generalize the applicability of the algorithm. Results of the PG fault, simulated on phase A at 0.1 s at node 646 with measurements at node 680 are illustrated in Figure 13. Current and voltage signals captured at node 680 for a period of 0.2 s (12 cycles) are detailed in Figure 13a,b, respectively. Current signals are processed using WDF and WD-index is computed, which is described in Figure 13c. It is observed that WD-index corresponding to phase A has a higher magnitude after the incidence of PG fault. However, this index corresponding to the phases B and C has values comparable to the pre-fault values. The ALN-index is computed from the voltage signals and described in Figure 13d. It is concluded that the ALN-index corresponding to all phases sharply increases just after the incidence of PG fault.

Figure 13e details the FI corresponding to all phases during the event of PG fault, when current and voltage signals are recorded at PCC. It can be concluded that FI corresponding to faulty phase (phase A) has a higher magnitude compared to TM after the incidence of PG fault. However, the FI corresponding to the healthy phases B and C has a lower magnitude as compared to TM. Hence, it is established that algorithm is effective for the identification of PG fault and discrimination of the healthy and faulty phases by recording the data at PCC. It establishes the applicability of algorithm to provide protection against faults for the RE sources based hybrid grids.

**Figure 13.** Recognition of the PG fault incident at node 646 by recording voltage and current signals at PCC (**a**) current waveform (**b**) voltage waveform (**c**) WD-index (**d**) ALN-index (**e**) FI.
