a transient current based busbar protection scheme using wavelet transforms

this paper deals with application of wavelet transform for detection of busbar faults and to discriminate them from external faults. the fault indexes of differential current and that of a source ct current are obtained over narrow moving windows based on their respective detail coefficients. the fault indexes of both current signals obtained are compared with their respective threshold values to detect the internal faults. the time shift of differential current detail coefficients compared to those of source current due to saturation of ct is used to discriminate the external faults from internal faults. the scheme is tested successfully for different types of external and internal faults.