external fault detection

In this paper, a new method is proposed for low fault resistance fault detection and classification in two interconnected microgrid with tie line connection in island situation (Islanded two interconnected AC microgrid). The proposed method classifies the types of faults based on modal and superimposed fault current analysis. In order to analyze the modal, the Clarke transform is used so that the zero-sequence current can be monitored. Also, mathematical morphology method is used to find the amount of injected fault current in signal processing context. In this article, the theory of mathematical morphology is proposed using signal closing filter to identify amplitude changes and distortion in the measured current through time domain analysis. This theory is implemented in this paper to identify and classify all types of faults in a timely manner. Additionally, comparing to another signal processing methods based on frequency domain analysis or frequency-time domain, it has the advantage of requiring a telecommunication system with lower bandwidth and cost. The proposed method for classifying single-phase to ground, two-phase to ground, and three-phase faults in two microgrids connected through a tie line has been simulated as a case study. The numerical results illustrate the efficiency and effectiveness of the proposed method in classifying the types of faults with small resistance.