A Voltage Based Technique Using Combined Features of Stockwell Transform and Hilbert Transform for Detection of Islanding Events

A technique is utilizing the voltage signal to detect Islanding events and operational incidents and also to discriminate the operational events from the islanding events is proposed in this manuscript. A test utility network designed in Simulink environment of MATLAB software is used for the proposed study. Voltage waveforms recorded at the Point of Common Coupling (PCC) of the test grid is decomposed by utilizes the Stockwell Transform, and complex S-matrix is extracted. A median of S-matrix is obtained and represented as ST-index, which is plotted with time. Further, voltage waveforms are decomposed with the aid of Hilbert Transform, and the absolute outcome is represented as H-index. Element to element multiplication of ST-index and H-index is performed, and the resulting index is represented as Islanding index. A threshold value is set for this index and magnitudes more significant than the threshold presents the presence of islanding and value below the threshold indicates the operational event.