Optimizing the boundary of a backup protection in a digital substation using graph theory

With the rapid development of smart grid, digital substation plays an important role to ensure reliability and security of power grid operation. The application of IEC61850 provides the communications standard for total information sharing within a substation. Based on this foundation, this paper analyzes the information from the entire substation's primary and secondary equipment and represents the topological structure of digital substation backup protection by means of graph theory. In this way, a graph showing their interconnections with a set of relationship matrices can be produced. Analyzing the relationship matrices can dynamically change the substation differential backup protection's boundary in various scenarios including CB opening/closing and CB information loss. The application of graph theory ensures the adaptability and correct operation of substation backup protection. It can also optimize the boundary of the backup protection by reducing the action of breakers.