Towards defined security by identifying and quantifying power system failure sequences: Case example with the Finnish power system

Defining power system security requires knowledge of the dynamic behavior of the system in disturbed conditions. This paper describes the process of identifying vulnerabilities and quantifying the security of a power system by presenting a dynamic simulation study of the Finnish power system. The results show the change of the security of a power system as the amount of power transfer is increased or decreased on the critical corridor. The results also show the variation of system security as the fault frequency varies. The paper presents equal areas of risk when power transfer on critical corridor and fault frequency vary. This clearly illustrates that exceeding N - 1 secure transfer limits lead to highly different system collapse probabilities which depend on the grid fault frequency.