A study of the change in assessing the stability of the interconnected system when connecting a link (line) between its two subsystems

Under the current conditions of electricity market liberalization, it is often necessary to rapidly perform considerable changes in the power flows of cross-border lines or between isolated subsystems inside the country. For this purpose, in most cases, it is possible to use a simple connection / disconnection of a connection, which leads to a change in the topology of two subsystems. In such a situation it is quite reasonable to consider an issue regarding the change of the stability assessment for the generators on either side of the boundary interconnection before and after switching. In this paper, the authors have studied how the matrix eigenvalues of the coefficients of the two subsystems change after being combined into a single matrix; also, they have derived the conditions at which rapid assessment of the stability of the newly formed interconnected system can be performed according to preliminary estimates of the two subsystems before their interconnection. It has been indicated how and for what purposes this approach can be used when studying the stability of complex electrical systems.