Mathematical Morphology-Based Fault Data Self-Synchronization Method for Differential Protection in Distribution Networks

Conventional overcurrent protection is hard to apply to modern distribution networks with high penetration of distributed generations and flexible operation modes. Current differential protection (CDP) is considered to be a good solution, but the expensive cost of data synchronization equipment limits its application. Fault data self-synchronization (FDSS) methods realize the approximate data synchronization according to the features of measured currents at both terminals, which makes it possible to achieve the low-cost CDP. However, the existing FDSS methods still have shortcomings such as low accuracy or complicated steps. In this paper, the principles and defects of existing FDSS methods are first analyzed, and then an improved FDSS method based on mathematical morphology (MM) is proposed. This method is realized by MM filter and MM-based peak-valley detection algorithm, which has higher synchronization accuracy and anti-noise ability. More importantly, in this method, the reference time required for synchronization can be obtained in the pre-communication process, which is easily implemented. The simulation based on PSCAD-MATLAB verifies the effectiveness of the proposed method under different fault conditions and its improvement compared with the existing method. Finally, the RTDS-based hardware test platform is used to verify the differential relay prototypes developed based on the proposed method.

Automated summary

This paper analyzes the principles and defects of existing fault data self-synchronization methods and proposes an improved method based on mathematical morphology. The effectiveness and improvement of the proposed method are verified through simulation and hardware testing.