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.

Research highlights
► External faults cause CT saturation and hence false-tripping of Differential Busbar protection scheme.
► Proposed scheme analyzes transients of differential and source currents using Wavelets.
► Fault Indexes are defined and used to detect all faults.
► False tripping is avoided by using the time shift between transients of these two currents in case of external faults.
► Scheme tested successfully for various internal and external faults.