A High-Speed Digital Current Differential Protection Algorithm for Power Transmission Lines in Smart Grids

The objective of this paper is to propose and investigate a novel hybrid technique consisting of wavelet packet transform (WPT) and direct and quadrature (dq) axis components for current differential protection of transmission lines. The idea in this paper is to develop and implement this hybrid technique by localizing the frequency sub-bands of dq axis components of the differential currents using the WPT in order to find out and evaluate the best signature of the internal faults. The results show that the high-frequency sub-band provides the best signature and enough information to detect any fault in the transmission lines. This hybrid technique provides good accuracy and fast fault clearance speed with minimum level of WPT of the dq components of the differential current. Off-line results of the collected data from a laboratory experimental setup are provided in this paper for different faults at different locations on the transmission line.