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Rapid technological development in grid integration of renewable energy (RE) plants has increased the RE penetration level in power utility network. This dramatic change in power scenario challenges the protection and stability of grid. Therefore, this work proposed a protection scheme algorithm (PSA) for the RE integrated hybrid power system. This PSA is implemented in the following steps: (1) calculate Wigner distribution function powered fault index (WFI), (2) calculate Stockwell transform powered combined FI (SCFI), (3) calculate hybrid FI (HFI) using WFI and SCFI, (4) classify the faults using number of faulty phases and fault ground index. Proposed hybrid fault index is used for the identification of faults. It also considers the change in magnitude and waveform distortions of current signals. The proposed PSA effectively identifies and classifies the faulty events such as single phase to ground, two phase, two phase to ground and all phases to ground. PSA is successfully tested for the recognition of faults under various operating scenarios like noisy scenario, different magnitudes of fault impedance, fault location node and fault incidence angle, lines comprising of overhead section and underground cable with availability of transformer. This PSA is effective to discriminate the operational switching events compared to faulty events. It is concluded that performance of the introduced PSA is better and fault detection time is less compared to wavelet energy spectrum entropy based PSA, discrete wavelet transform (DWT) based PSA and Stockwell transform supported PSA. [ABSTRACT FROM AUTHOR]

This paper introduces an algorithm based on wavelet packet supported fast kurtogram and decision rules for the identification and classification of complex power quality (PQ) disturbances. Features are extracted from the signals using fast kurtogram, envelope of filtered voltage signal and amplitude spectrum of squared envelop. Proposed algorithm can be implemented for the recognition of the complex PQ disturbances, which include the combination of voltage sag and harmonics, voltage momentary interruption (MI) and oscillatory transient (OT), voltage MI and harmonics, voltage sag and impulsive transient (IT), voltage sag, OT, IT and harmonics. Proposed work has been performed using the MATLAB software. Performance of the algorithm is compared with performance of algorithm supported by discrete wavelet transform (DWT) and fuzzy C-means clustering (FCM). [ABSTRACT FROM AUTHOR]

Penetration level of renewable energy (RE) in the utility grid is continuously increasing to minimize the environmental concerns, risk of energy security, and depletion of fossil fuels. The uncertain nature and availability of RE power for a short duration have created problems related to the protection, grid security, power reliability, and power quality. Further, integration of RE sources near the load centers has also pronounced the protection issues, such as false tripping, delayed tripping, etc. Hence, this paper introduces a hybrid grid protection scheme (HGPS) for the protection of the grid with RE integration. This combines the merits of the Stockwell Transform, Hilbert Transform, and Alienation Coefficient to improve performance of the protection scheme. The Stockwell Transform-based Median and Summation Index (SMSI) utilizing current signals, Hilbert Transform-based derivative index (HDI) utilizing voltage signals, and Alienation Coefficient index (ACI) utilizing voltage signals were used to compute a proposed Stockwell Transform-, Hilbert Transform-, and Alienation-based fault index (SAHFI). This SAHFI was used to recognize the fault conditions. The fault conditions were categorized using the number of faulty phases and the proposed Stockwell Transform and Hilbert Transform-based ground fault index (SHGFI) utilizing zero sequence currents. The fault conditions, such as phase and ground (PGF), any two phases (TPF), any two phases and ground (TPGF), all three phases (ATPF), and all three phases and ground (ATPGF), were recognized effectively, using the proposed SAHFI. The proposed method has the following merits: performance is least affected by the noise, it is effective in recognizing fault conditions in minimum time, and it is also effective in recognizing the fault conditions in different scenarios of the grid. Performance of the proposed approach was found to be superior compared to the discrete wavelet transform (DWT)-based method reported in the literature. The study was performed using the hybrid grid test system realized by integrating wind and solar photovoltaic (PV) plants to the IEEE-13 nodes network in MATLAB software. [ABSTRACT FROM AUTHOR]