High impedance fault detection using orthogonal transforms

High impedance faults (HIFs) are generated when power lines down on poorly conductive surface, or have unexpected contact with neighbor objects. They have been researched and investigated for many years since they pose a threat to humans and livestock; and there are already many methods of detecting this kind of fault. An electrical model for HIF is implemented, and practical fault events from official websites of Department of Energy/Electric Power Research Institute (DOE/EPRI) National Database Repository of Power System Events are studied for developing a reliable detecting method. The occurrence of HIF is detected by applying sliding orthogonal transforms such as fast Fourier transform (FFT) and Walsh Hadamard Transform (WHT) in order to investigate its harmonic-current content and perform HIF detection. The criteria to declare the existence of fault currents are based on the threshold and shape of the magnitude and phase responses of orthogonal transformed results.