Detection of power swing and blocking the distance relay using the variance calculation of the current sampled data

Power swings appear as a result of sudden addition or removal of heavy loads, switching, cutoff of a parallel line, and reclosing. These swings can affect the protective zones of distance relays, causing them to malfunction and erroneously cut off healthy lines from the grid. This paper proposes a new solution for detecting power swings and preventing this malfunction based on the variance of data sampled from the current signal. The lack of any signal processing phase in the proposed solution makes it computationally light and thus suitable for implementation in distance relays. In addition, the method's performance is not affected by the presence of noise in the sampled signal. The method is able to detect power swings of stable, unstable, and multi-mode variety. In comparison with some of the latest works in the field of power swing detection as well as conventional methods, it is demonstrated that the method outperforms them in terms of response time, the ability to detect different varieties of the power swing, and the ability to detect different varieties of faults that may occur simultaneously with a power swing.