*3.4. Ground Fault Index*

Faults 2P and 2PG cannot be differentiated from each other based on the number of faulty phases. This is achieved by introducing the ground fault index (GFI), which is obtained by processing the zero sequence component of the current signal sampled at the frequency of 3.84 kHz using Wigner distribution function as illustrated in Equation (5). A threshold magnitude for ground fault index (TMGFI) is set equal to 2000 for differentiating the 2P and 2PG faults. Magnitude of GFI greater than TMGFI will indicate the involvement of ground in the faulty event. Hence, values of GFI greater than TMGFI detects the 2PG fault. However, values low compared to the TMGFI detects the 2P fault.
