The adaptive and robust power system protection schemes in the presence of DGs

In recent years, using distributed generations (DGs) has increased in order to compensate the load and consumption growth. Although connecting DG resources to power system has many advantages, it might cause some protective problems such as mis-coordination between network protection devices, due to the changing in the short circuit level of power system. In this paper, two method for restoring the coordination of relays in the presence of DGs by using FCLs are proposed. In both methods, different criteria, such as considering the variation of network topology, optimizing the value and number of FCLs are considered to propose a comprehensive and adaptive protection method. In the first method, an adaptive protection scheme by using FCLs is proposed to active and deactivate FCLs in different topologies to restore the coordination of relays. In addition, the second method proposes a robust method which considers all possible situations and topologies of the power system to maintain the coordination of power system during fault. Finally, the proposed robust and adaptive protection scheme has been compared in terms of cost, the operation time of relays and computation time, and based on the aims of operators in a power system one of these method can be implemented, The proposed methods are implemented on IEEE 14-bus standard network, and all possible topologies of the mentioned network are considered. Simulation results show that the proposed method can maintain the coordination of overcurrent relay protection in the presence of DGs and topology changes. In other words, the proposed method is robust against topologies changes.