A Novel Time–Frequency Transform Based Spectral Energy Function for Fault Detection During Power Swing

Fault during a power swing is a challenging task for the distance relay functioning. This article presents a spectral energy function for fault detection during a power swing using a novel time frequency transform known as the S-transform, a variable windowed short-time Fourier transform, which combines the elements of short-time Fourier transform and wavelet transform. Initially, the current signal is preprocessed using S-transform to generate the S-matrix and corresponding S-contours (time–frequency contours). The spectral energy content of the S-counters is used to register symmetrical and unsymmetrical faults during a power swing and, based on a set threshold on the spectral energy, the relay blocks during a power swing and issue of the tripping signal during fault. The proposed technique is tested for different fault conditions during a power swing with possible variations in operating parameters, including the ability to identify the faults with a response time of 1.25 cycles from the fault inception during power swing.