**9. Conclusions**

A method for the detection and classification of faults is presented in this paper to design a protection scheme for hybrid grid system integrated with wind and solar energy plants. Various fault types such as PG, 2P, 2PG, and 3PG were successfully identified in the RE sources based hybrid grid using proposed fault index. The FI is obtained using Wigner distribution function based decomposition of current signals (WD-index) sample with alienation coefficient of voltage signals (ALN-index). Fault types were classified using number of faulty phases and identified using proposed FI. A ground fault index, based on the Wigner distribution function supported decomposition of negative sequence current is proposed to differentiate the 2P and 2PG faults. It is concluded that the algorithm is fast and accurate for detection of all the types of faults in the hybrid grid with RE penetration. Furthermore, the algorithm was tested and effectively works in the presence of high level noise, different fault incidence angles, high fault impedance and different fault locations. The algorithm is also effective for the discrimination of switching events of capacitor, load and line feeder from faulty events. The algorithm is also effective in recognizing faults in the presence of transformers and hybrid lines consisting of OH line and UG cable sections. It is also established that the proposed algorithm obtained using WD-index and ALN-index has the combined merits of these indexes and provide fast response protection scheme whose performance is not affected by the noise. Hence it is established that performance of proposed algorithm is superior compared to DWT, ST, standalone WD-index and standalone ALN-index. As a future enhancement, testing of performance of algorithm with data recorded on real time network of the utility grids may be considered before implementation in the protection schemes.

**Author Contributions:** Conceptualization, S.R.O., O.P.M., A.S., V.S. and S.K.G.; methodology, S.R.O. and O.P.M.; software, S.R.O. and O.P.M.; validation, S.R.O. and O.P.M.; formal analysis, S.R.O., B.K. and O.P.M.; investigation, S.R.O. and O.P.M.; resources, A.S., S.K.G., H.H.A. and P.S.; data curation, S.R.O., B.K. and O.P.M.; writing—original draft preparation, S.R.O., B.K. and O.P.M.; writing—review and editing, B.K., H.H.A. and P.S.; visualization, B.K., H.H.A. and P.S.; supervision, A.S., S.K.G., H.H.A. and P.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** External funding is not received for this research.

**Conflicts of Interest:** The authors declare that they have no known conflicts of interest.

*Energies* **2020**, *13*, 1120
