Reference Phasor-Based Data Self-Synchronization Scheme for Line Current Differential Protection in Active Distribution Networks

Line current differential protection (CDP) is very suitable for active distribution networks (ADNs) with complex fault characteristics in principle, but its high cost limits its application. The data self-synchronization (DSS) methods do not require investing in additional synchronization equipment and provide a low-cost solution for line CDP in ADNs. However, the existing DSS methods based on time-domain features still have some shortcomings, such as they cannot be applied to lines with T-connected branches and are vulnerable to noise. In this paper, the existing DSS methods are first reviewed. On this basis, an improved DSS scheme based on reference phasor is proposed. This scheme calculates reference phasors based on the full-cycle data in a specific period before the fault and corrects the CDP criterion according to reference phasors. The proposed scheme includes three correction methods designed for lines without T-connected branches, lines with measurable T-connected branches and lines with unmeasurable T-connected branches, respectively. Finally, the performance of the proposed scheme is verified by an ADN simulation model based on PSCAD/EMTDC. Simulation results show that compared with existing DSS methods, the proposed scheme has the advantages unaffected by fault inception angles, better anti-noise ability, lower sampling frequency requirements, and wider application scenarios.