An analysis to the concentric relaxation vulnerability area of voltage sag in power system

This paper presents a new definition of vulnerability area of voltage sags concentric relaxation vulnerability area (CRVA) that is the area of voltage sags caused by fault with the fault point as the center. Analyzing CRVA could greatly reduce the workload involved in traditional voltage sag vulnerability areas and provided us a judgment reference of the attribution of liabilities between power supply department and power users. Based on such conclusions, we use the GUI of MATLAB to conduct user graphical interface programmed to develop a general software for analyzing CRVA caused by voltage sags. Meanwhile, we take into account the influence posed on CRVA by transformer connection mode when the fault occurs on the low- or high-voltage side of the transformer. The above algorithm enables us to derive the CRVA of IEEE-30 bus system and build such a model through PSCAD to demonstrate the accuracy of CRVA analyzing software in a simulated manner.